Publications of Ehsan Samei    :chronological  alphabetical  combined listing:

%% Books   
@book{fds38014,
   Author = {E. Samei and A. Badano and D. Chakraborty and K. Compton and C.
             Cornelius, K. Corrigan and M.J. Flynn and B. Hemminger and N.
             Hangiandreou, J. Johnson and M. Moxley and W. Pavlicek and H.
             Roehrig, L. Rutz and J. Shepard and R. Uzenoff and J. Wang and C.
             Willis},
   Title = {Assessment of Display Performance for Medical Imaging
             Systems},
   Series = {Report of the American Association of Physicists in Medicine
             (AAPM) Task Group 18, AAPM On-Line Report No.
             03},
   Publisher = {Medical Physics Publishing, Madison, WI},
   Year = {2005},
   Month = {April},
   Key = {fds38014}
}

@book{fds38013,
   Title = {Advances in Digital Radiography},
   Series = {Categorical Course Syllabus},
   Publisher = {Radiological Society of North America (RSNA) Publication,
             Oak Brook, IL},
   Editor = {E. Samei},
   Year = {2003},
   Key = {fds38013}
}


%% Papers Published   
@article{fds329330,
   Author = {Fu, W and Marin, D and Ramirez-Giraldo, JC and Choudhury, KR and Solomon, J and Schabel, C and Patel, BN and Samei,
             E},
   Title = {Optimizing window settings for improved presentation of
             virtual monoenergetic images in dual-energy computed
             tomography.},
   Journal = {Medical physics},
   Volume = {44},
   Number = {11},
   Pages = {5686-5696},
   Year = {2017},
   Month = {November},
   url = {http://dx.doi.org/10.1002/mp.12501},
   Abstract = {Dual-energy computed tomography virtual monoenergetic
             imaging (VMI) at 40 keV exhibits superior contrast-to-noise
             ratio (CNR), although practicing radiologists do not
             consistently prefer it over VMI at 70 keV due to high
             perceivable noise. We hypothesize that the presentation of
             40 keV VMI may be compromised using window settings (i.e.,
             window-and-level values [W-L values]) designed for
             conventional single-energy CT. This study aimed to devise
             optimum window settings that reduce the apparent noise and
             utilize the high CNR of 40 keV VMI, in order to improve the
             conspicuity of hypervascular liver lesions.Three W-L value
             adjustment methods were investigated to alter the
             presentation of 40 keV VMI. To harness the high CNR of 40
             keV VMI, the methods were designed to achieve (a) liver
             histogram distribution, (b) lesion-to-liver contrast, or (c)
             liver background noise comparable to those perceived in 70
             keV VMI. This IRB-approved study included 18 patient
             abdominal datasets reconstructed at 40 and 70 keV. For each
             patient, the W-L values were determined using the three
             methods. For each of the images with default or adjusted W-L
             values, the noise, contrast, and CNR were calculated in
             terms of both display space and native CT number (referred
             to as HU) space. An observer study was performed to compare
             the 40 keV images with the three adjusted W-L values, and 40
             and 70 keV images with default W-L values in terms of noise,
             contrast, and diagnostic preference. A comparison was also
             made in terms of the applicability of using patient-specific
             or patient-averaged W-L values.Using the default W-L values,
             40 keV VMI exhibited higher HU CNR than 70 keV VMI by 24.6
             ± 14.9% (P < 0.001) but lower display CNR by 38.0 ± 16.4%
             (P < 0.001). Using adjusted W-L values, 40 keV images showed
             increased display CNR as compared to 70 keV images, by 21.2
             ± 13.1%, 17.4 ± 13.6%, and 24.2 ± 15.9% (P < 0.001) for
             histogram-, noise-, and contrast equalization methods,
             respectively. The 40 keV images with all three W-L value
             adjustment methods showed improved perceived conspicuity
             (CNR) of liver presentation by 103-120% (P < 0.001), as
             compared to default W-L values. The qualitative observer
             study revealed that 40 keV images with noise- and
             histogram-equalized W-L values were the most preferred,
             followed by 40 keV images with contrast-equalized W-L values
             and 70 keV images with default W-L values. The 40 keV images
             with default W-L values were the least preferred.
             Patient-specific W-L values offered similar results to those
             of patient-averaged W-L values.The adjusted W-L values can
             significantly improve the perception of VMI dataset image
             quality by improving the actual display CNR.},
   Doi = {10.1002/mp.12501},
   Key = {fds329330}
}

@article{fds328131,
   Author = {Abadi, E and Sanders, J and Samei, E},
   Title = {Patient-specific quantification of image quality: An
             automated technique for measuring the distribution of organ
             Hounsfield units in clinical chest CT images.},
   Journal = {Medical physics},
   Volume = {44},
   Number = {9},
   Pages = {4736-4746},
   Year = {2017},
   Month = {September},
   url = {http://dx.doi.org/10.1002/mp.12438},
   Abstract = {To develop and validate an automated technique for measuring
             organ Hounsfield units (HUs) in clinical chest CT images.An
             automated computer algorithm was developed to measure the
             distribution of HUs inside four major organs: the lungs,
             liver, aorta, and spine. These organs were first identified
             using image processing techniques. Each organ was segmented
             into multiple regions of interest (ROIs) and characterized
             in terms of HU values. The medians of the ROI histograms
             were computed for each dataset. The automated results were
             validated by assessing their correlation with manual
             measurements in fifteen contrast-enhanced and fifteen
             non-contrast-enhanced clinical chest CT datasets. The
             robustness of the measurements with respect to dependency on
             image noise and CTDIvol was ascertained. One utility of the
             approach was further demonstrated in assessing the
             variability in aorta HUs across 732 patients undergoing
             noncontrast and contrast-enhanced examinations.The algorithm
             successfully measured the histograms of the four organs in
             both contrast and non-contrast-enhanced chest CT exams. The
             automated measurements were in agreement with manual
             measurements with a near unity slope of the relationship
             between automated and manual measurements with high
             coefficient of determination (slope = 0.931-1.003, R2 =
             0.89-0.99). Organ median HU measurements were found to be
             largely independent of both image noise and CTDIvol (P >
             0.05), as expected. Across patient cases, the program ran
             successfully across 95% (697/732) of cases. Aorta median HUs
             demonstrated five times more variability in
             contrast-enhanced exams compared to that in
             non-contrast-enhanced exams.Patient-specific organ HUs can
             be measured from clinical datasets. The algorithm that was
             developed can be run on both contrast-enhanced and
             non-contrast-enhanced clinical datasets. The method can be
             applied to automatically extract image HU-contrast
             characteristics of clinical CT images, not captured in
             phantom data, whereby enabling quantification and
             optimization of image quality and contrast
             administration.},
   Doi = {10.1002/mp.12438},
   Key = {fds328131}
}

@article{fds324788,
   Author = {Solomon, J and Marin, D and Roy Choudhury and K and Patel, B and Samei,
             E},
   Title = {Effect of Radiation Dose Reduction and Reconstruction
             Algorithm on Image Noise, Contrast, Resolution, and
             Detectability of Subtle Hypoattenuating Liver Lesions at
             Multidetector CT: Filtered Back Projection versus a
             Commercial Model-based Iterative Reconstruction
             Algorithm.},
   Journal = {Radiology},
   Volume = {284},
   Number = {3},
   Pages = {777-787},
   Year = {2017},
   Month = {September},
   url = {http://dx.doi.org/10.1148/radiol.2017161736},
   Abstract = {Purpose To determine the effect of radiation dose and
             iterative reconstruction (IR) on noise, contrast,
             resolution, and observer-based detectability of subtle
             hypoattenuating liver lesions and to estimate the dose
             reduction potential of the IR algorithm in question.
             Materials and Methods This prospective, single-center,
             HIPAA-compliant study was approved by the institutional
             review board. A dual-source computed tomography (CT) system
             was used to reconstruct CT projection data from 21 patients
             into six radiation dose levels (12.5%, 25%, 37.5%, 50%, 75%,
             and 100%) on the basis of two CT acquisitions. A series of
             virtual liver lesions (five per patient, 105 total,
             lesion-to-liver prereconstruction contrast of -15 HU, 12-mm
             diameter) were inserted into the raw CT projection data and
             images were reconstructed with filtered back projection
             (FBP) (B31f kernel) and sinogram-affirmed IR (SAFIRE)
             (I31f-5 kernel). Image noise (pixel standard deviation),
             lesion contrast (after reconstruction), lesion boundary
             sharpness (average normalized gradient at lesion boundary),
             and contrast-to-noise ratio (CNR) were compared. Next, a
             two-alternative forced choice perception experiment was
             performed (16 readers [six radiologists, 10 medical
             physicists]). A linear mixed-effects statistical model was
             used to compare detection accuracy between FBP and SAFIRE
             and to estimate the radiation dose reduction potential of
             SAFIRE. Results Compared with FBP, SAFIRE reduced noise by a
             mean of 53% ± 5, lesion contrast by 12% ± 4, and lesion
             sharpness by 13% ± 10 but increased CNR by 89% ± 19.
             Detection accuracy was 2% higher on average with SAFIRE than
             with FBP (P = .03), which translated into an estimated
             radiation dose reduction potential (±95% confidence
             interval) of 16% ± 13. Conclusion SAFIRE increases
             detectability at a given radiation dose (approximately 2%
             increase in detection accuracy) and allows for imaging at
             reduced radiation dose (16% ± 13), while maintaining
             low-contrast detectability of subtle hypoattenuating focal
             liver lesions. This estimated dose reduction is somewhat
             smaller than that suggested by past studies. © RSNA, 2017
             Online supplemental material is available for this
             article.},
   Doi = {10.1148/radiol.2017161736},
   Key = {fds324788}
}

@article{fds328884,
   Author = {Samei, E and Tian, X and Paul Segars and W and Frush,
             DP},
   Title = {Radiation risk index for pediatric CT: a patient-derived
             metric.},
   Journal = {Pediatric Radiology},
   Year = {2017},
   Month = {August},
   url = {http://dx.doi.org/10.1007/s00247-017-3973-z},
   Abstract = {There is a benefit in characterizing radiation-induced
             cancer risk in pediatric chest and abdominopelvic CT: a
             singular metric that represents the whole-body radiation
             burden while also accounting for age, gender and organ
             sensitivity.To compute an index of radiation risk for
             pediatric chest and abdominopelvic CT.Using a protocol
             approved by our institutional review board, 42 pediatric
             patients (age: 0-16 years, weight: 2-80 kg) were modeled
             into virtual whole-body anatomical models. Organ doses were
             estimated for clinical chest and abdominopelvic CT
             examinations of the patients using validated Monte Carlo
             simulations of two major scanner models. Using age-, size-
             and gender-specific organ risk coefficients, the values were
             converted to normalized effective dose (by dose length
             product) (denoted as the k factor) and a normalized risk
             index (denoted as the q factor). An analysis was performed
             to determine how these factors are correlated with patient
             age and size for both males and females to provide a
             strategy to better characterize individualized risk.The k
             factor was found to be exponentially correlated with the
             average patient diameter. For both genders, the q factor
             also exhibited an exponential relationship with both the
             average patient diameter and with patient age. For both
             factors, the differences between the scanner models were
             less than 8%.The study defines a whole-body radiation risk
             index for chest and abdominopelvic CT imaging, that
             incorporates individual estimated organ dose values, organ
             radiation sensitivity, patient size, exposure age and
             patient gender. This indexing metrology enables the
             assessment and potential improvement of chest and
             abdominopelvic CT performance through surveillance of
             practice dose profiles across patients and may afford
             improved informed communication.},
   Doi = {10.1007/s00247-017-3973-z},
   Key = {fds328884}
}

@article{fds329138,
   Author = {Robins, M and Solomon, J and Sahbaee, P and Sedlmair, M and Roy
             Choudhury, K and Pezeshk, A and Sahiner, B and Samei,
             E},
   Title = {Techniques for virtual lung nodule insertion: volumetric and
             morphometric comparison of projection-based and image-based
             methods for quantitative CT.},
   Journal = {Physics in Medicine and Biology},
   Volume = {62},
   Number = {18},
   Pages = {7280-7299},
   Year = {2017},
   Month = {August},
   url = {http://dx.doi.org/10.1088/1361-6560/aa83f8},
   Abstract = {Virtual nodule insertion paves the way towards the
             development of standardized databases of hybrid CT images
             with known lesions. The purpose of this study was to assess
             three methods (an established and two newly developed
             techniques) for inserting virtual lung nodules into CT
             images. Assessment was done by comparing virtual nodule
             volume and shape to the CT-derived volume and shape of
             synthetic nodules. 24 synthetic nodules (three sizes, four
             morphologies, two repeats) were physically inserted into the
             lung cavity of an anthropomorphic chest phantom (KYOTO
             KAGAKU). The phantom was imaged with and without nodules on
             a commercial CT scanner (SOMATOM Definition Flash, Siemens)
             using a standard thoracic CT protocol at two dose levels
             (1.4 and 22 mGy CTDIvol). Raw projection data were saved and
             reconstructed with filtered back-projection and sinogram
             affirmed iterative reconstruction (SAFIRE, strength 5) at
             0.6 mm slice thickness. Corresponding 3D idealized,
             virtual nodule models were co-registered with the CT images
             to determine each nodule's location and orientation. Virtual
             nodules were voxelized, partial volume corrected, and
             inserted into nodule-free CT data (accounting for system
             imaging physics) using two methods: projection-based
             Technique A, and image-based Technique B. Also a third
             Technique C based on cropping a region of interest from the
             acquired image of the real nodule and blending it into the
             nodule-free image was tested. Nodule volumes were measured
             using a commercial segmentation tool (iNtuition, TeraRecon,
             Inc.) and deformation was assessed using the Hausdorff
             distance. Nodule volumes and deformations were compared
             between the idealized, CT-derived and virtual nodules using
             a linear mixed effects regression model which utilized the
             mean, standard deviation, and coefficient of variation
             ([Formula: see text], [Formula: see text] and [Formula: see
             text] of the regional Hausdorff distance. Overall, there was
             a close concordance between the volumes of the CT-derived
             and virtual nodules. Percent differences between them were
             less than 3% for all insertion techniques and were not
             statistically significant in most cases. Correlation
             coefficient values were greater than 0.97. The deformation
             according to the Hausdorff distance was also similar between
             the CT-derived and virtual nodules with minimal statistical
             significance in the ([Formula: see text]) for Techniques A,
             B, and C. This study shows that both projection-based and
             image-based nodule insertion techniques yield realistic
             nodule renderings with statistical similarity to the
             synthetic nodules with respect to nodule volume and
             deformation. These techniques could be used to create a
             database of hybrid CT images containing nodules of known
             size, location and morphology.},
   Doi = {10.1088/1361-6560/aa83f8},
   Key = {fds329138}
}

@article{fds329837,
   Author = {Samei, E and Hoeschen, C},
   Title = {Special Section Guest Editorial: Visions of Safety:
             Perspectives on Radiation Exposure and Risk in Medical
             Imaging.},
   Journal = {Journal of medical imaging (Bellingham, Wash.)},
   Volume = {4},
   Number = {3},
   Pages = {031201},
   Year = {2017},
   Month = {July},
   url = {http://dx.doi.org/10.1117/1.jmi.4.3.031201},
   Abstract = {This guest editorial introduces the special section on
             Visions of Safety: Perspectives on Radiation Exposure and
             Risk in Medical Imaging.},
   Doi = {10.1117/1.jmi.4.3.031201},
   Key = {fds329837}
}

@article{fds328129,
   Author = {Fu, W and Sturgeon, GM and Agasthya, G and Segars, WP and Kapadia, AJ and Samei, E},
   Title = {Breast dose reduction with organ-based, wide-angle tube
             current modulated CT.},
   Journal = {Journal of medical imaging (Bellingham, Wash.)},
   Volume = {4},
   Number = {3},
   Pages = {031208},
   Year = {2017},
   Month = {July},
   url = {http://dx.doi.org/10.1117/1.jmi.4.3.031208},
   Abstract = {This study aimed to estimate the organ dose reduction
             potential for organ-dose-based tube current modulated (ODM)
             thoracic computed tomography (CT) with a wide dose reduction
             arc. Twenty-one computational anthropomorphic phantoms
             (XCAT) were used to create a virtual patient population with
             clinical anatomic variations. The phantoms were created
             based on patient images with normal anatomy (age range: 27
             to 66 years, weight range: 52.0 to 105.8 kg). For each
             phantom, two breast tissue compositions were simulated:
             [Formula: see text] and [Formula: see text]
             (glandular-to-adipose ratio). A validated Monte Carlo
             program (PENELOPE, Universitat de Barcelona, Spain) was used
             to estimate the organ dose for standard tube current
             modulation (TCM) (SmartmA, GE Healthcare) and ODM (GE
             Healthcare) for a commercial CT scanner (Revolution, GE
             Healthcare) using a typical clinical thoracic CT protocol.
             Both organ dose and [Formula: see text]-to-organ dose
             conversion coefficients ([Formula: see text] factors) were
             compared between TCM and ODM. ODM significantly reduced all
             radiosensitive organ doses ([Formula: see text]). The breast
             dose was reduced by [Formula: see text]. For [Formula: see
             text] factors, organs in the anterior region (e.g., thyroid
             and stomach) exhibited substantial decreases, and the
             medial, distributed, and posterior region saw either an
             increase of less than 5% or no significant change. ODM
             significantly reduced organ doses especially for
             radiosensitive superficial anterior organs such as the
             breasts.},
   Doi = {10.1117/1.jmi.4.3.031208},
   Key = {fds328129}
}

@article{fds328130,
   Author = {Hoye, J and Zhang, Y and Agasthya, G and Sturgeon, G and Kapadia, A and Segars, WP and Samei, E},
   Title = {Organ dose variability and trends in tomosynthesis and
             radiography.},
   Journal = {Journal of medical imaging (Bellingham, Wash.)},
   Volume = {4},
   Number = {3},
   Pages = {031207},
   Year = {2017},
   Month = {July},
   url = {http://dx.doi.org/10.1117/1.jmi.4.3.031207},
   Abstract = {The purpose of this study was to investigate relationships
             between patient attributes and organ dose for a population
             of computational phantoms for 20 tomosynthesis and
             radiography protocols. Organ dose was estimated from 54
             adult computational phantoms (age: 18 to 78 years, weight 52
             to 117 kg) using a validated Monte-Carlo simulation
             (PENELOPE) of a system capable of performing tomosynthesis
             and radiography. The geometry and field of view for each
             exam were modeled to match clinical protocols. For each
             protocol, the energy deposited in each organ was estimated
             by the simulations, converted to dose units, and then
             normalized by exposure in air. Dose to radiosensitive organs
             was studied as a function of average patient thickness in
             the region of interest and as a function of body mass index.
             For tomosynthesis, organ doses were also studied as a
             function of x-ray tube position. This work developed
             comprehensive information for organ dose dependencies across
             a range of tomosynthesis and radiography protocols. The
             results showed a protocol-dependent exponential decrease
             with an increasing patient size. There was a variability in
             organ dose across the patient population, which should be
             incorporated in the metrology of organ dose. The results can
             be used to prospectively and retrospectively estimate organ
             dose for tomosynthesis and radiography.},
   Doi = {10.1117/1.jmi.4.3.031207},
   Key = {fds328130}
}

@article{fds327287,
   Author = {Pawlicki, T and Ayers, RG and Brock, KK and Clements, JB and Curran, BH and Dobbins, JT and Samei, E and Adams, E and Martin, MC and Schober,
             L},
   Title = {Proposed changes to the American Association of Physicists
             in Medicine governance.},
   Journal = {Journal of applied clinical medical physics / American
             College of Medical Physics},
   Volume = {18},
   Number = {4},
   Pages = {4-6},
   Year = {2017},
   Month = {July},
   url = {http://dx.doi.org/10.1002/acm2.12124},
   Doi = {10.1002/acm2.12124},
   Key = {fds327287}
}

@article{fds328885,
   Author = {Samei, E and Li, X and Frush, DP},
   Title = {Size-based quality-informed framework for quantitative
             optimization of pediatric CT.},
   Journal = {Journal of medical imaging (Bellingham, Wash.)},
   Volume = {4},
   Number = {3},
   Pages = {031209},
   Year = {2017},
   Month = {July},
   url = {http://dx.doi.org/10.1117/1.jmi.4.3.031209},
   Abstract = {The purpose of this study was to formulate a systematic,
             evidence-based method to relate quantitative diagnostic
             performance to radiation dose, enabling a multidimensional
             system to optimize computed tomography imaging across
             pediatric populations. Based on two prior foundational
             studies, radiation dose was assessed in terms of organ
             doses, effective dose ([Formula: see text]), and risk index
             for 30 patients within nine color-coded pediatric age-size
             groups as a function of imaging parameters. The cases,
             supplemented with added noise and simulated lesions, were
             assessed in terms of nodule detection accuracy in an
             observer receiving operating characteristic study. The
             resulting continuous accuracy-dose relationships were used
             to optimize individual scan parameters. Before optimization,
             the nine protocols had a similar [Formula: see text] of
             [Formula: see text] with accuracy decreasing from 0.89 for
             the youngest patients to 0.67 for the oldest. After
             optimization, a consistent target accuracy of 0.83 was
             established for all patient categories with [Formula: see
             text] ranging from 1 to 10 mSv. Alternatively, isogradient
             operating points targeted a consistent ratio of
             accuracy-per-unit-dose across the patient categories. The
             developed model can be used to optimize individual scan
             parameters and provide for consistent diagnostic performance
             across the broad range of body sizes in children.},
   Doi = {10.1117/1.jmi.4.3.031209},
   Key = {fds328885}
}

@article{fds324791,
   Author = {Sahbaee, P and Segars, WP and Marin, D and Nelson, RC and Samei,
             E},
   Title = {The Effect of Contrast Material on Radiation Dose at CT:
             Part I. Incorporation of Contrast Material Dynamics in
             Anthropomorphic Phantoms.},
   Journal = {Radiology},
   Volume = {283},
   Number = {3},
   Pages = {739-748},
   Year = {2017},
   Month = {June},
   url = {http://dx.doi.org/10.1148/radiol.2016152851},
   Abstract = {Purpose To develop a method to incorporate the propagation
             of contrast material into computational anthropomorphic
             phantoms for estimation of organ dose at computed tomography
             (CT). Materials and Methods A patient-specific
             physiologically based pharmacokinetic (PBPK) model of the
             human cardiovascular system was incorporated into 58
             extended cardiac-torso (XCAT) patient phantoms. The PBPK
             model comprised compartmental models of vessels and organs
             unique to each XCAT model. For typical injection protocols,
             the dynamics of the contrast material in the body were
             described according to a series of patient-specific iodine
             mass-balance differential equations, the solutions to which
             provided the contrast material concentration time curves for
             each compartment. Each organ was assigned to a corresponding
             time-varying iodinated contrast agent to create the contrast
             material-enhanced five-dimensional XCAT models, in which the
             fifth dimension represents the dynamics of contrast
             material. To validate the accuracy of the models, simulated
             aortic and hepatic contrast-enhancement results throughout
             the models were compared with previously published clinical
             data by using the percentage of discrepancy in the mean,
             time to 90% peak, peak value, and slope of enhancement in a
             paired t test at the 95% significance level. Results The
             PBPK model allowed effective prediction of the time-varying
             concentration curves of various contrast material
             administrations in each organ for different patient models.
             The contrast-enhancement results were in agreement with
             results of previously published clinical data, with mean
             percentage, time to 90% peak, peak value, and slope of less
             than 10% (P > .74), 4%, 7%, and 14% for uniphasic and 12% (P
             > .56), 4%, 12%, and 14% for biphasic injection protocols,
             respectively. The exception was hepatic enhancement results
             calculated for a uniphasic injection protocol for which the
             discrepancy was less than 25%. Conclusion A technique to
             model the propagation of contrast material in XCAT human
             models was developed. The models with added contrast
             material propagation can be applied to simulate
             contrast-enhanced CT examinations. © RSNA, 2017 Online
             supplemental material is available for this
             article.},
   Doi = {10.1148/radiol.2016152851},
   Key = {fds324791}
}

@article{fds326500,
   Author = {Sahbaee, P and Abadi, E and Segars, WP and Marin, D and Nelson, RC and Samei, E},
   Title = {The Effect of Contrast Material on Radiation Dose at CT:
             Part II. A Systematic Evaluation across 58 Patient
             Models.},
   Journal = {Radiology},
   Volume = {283},
   Number = {3},
   Pages = {749-757},
   Year = {2017},
   Month = {June},
   url = {http://dx.doi.org/10.1148/radiol.2017152852},
   Abstract = {Purpose To estimate the radiation dose as a result of
             contrast medium administration in a typical abdominal
             computed tomographic (CT) examination across a library of
             contrast material-enhanced computational patient models.
             Materials and Methods In part II of this study, first, the
             technique described in part I of this study was applied to
             enhance the extended cardiac-torso models with
             patient-specific iodine-time profiles reflecting the
             administration of contrast material. Second, the patient
             models were deployed to assess the patient-specific organ
             dose as a function of time in a typical abdominal CT
             examination using Monte Carlo simulation. In this
             hypothesis-generating study, organ dose refers to the total
             energy deposited in the unit mass of the tissue inclusive of
             iodine. Third, a study was performed as a strategy to
             anticipate the biologically relevant dose (absorbed dose to
             tissue) in highly perfused organs such as the liver and
             kidney. The time-varying organ-dose increment values
             relative to those for unenhanced CT examinations were
             reported. Results The results from the patient models
             subjected to the injection protocol indicated up to a total
             53%, 30%, 35%, 54%, 27%, 18%, 17%, and 24% increase in
             radiation dose delivered to the heart, spleen, liver,
             kidneys, stomach, colon, small intestine, and pancreas,
             respectively. The biologically relevant dose increase with
             respect to the dose at an unenhanced CT examination was in
             the range of 0%-18% increase for the liver and 27% for the
             kidney across 58 patient models. Conclusion The
             administration of contrast medium increases the total
             radiation dose. However, radiation dose, while relevant to
             be included in estimating the risk associated with
             contrast-enhanced CT, may still not fully characterize the
             total biologic effects. Therefore, given the fact that many
             CT diagnostic decisions would be impossible without the use
             of iodine, this study suggests the need to consider the
             effect of iodinated contrast material on the organ doses to
             patients undergoing CT studies when designing CT protocols.
             © RSNA, 2017 Online supplemental material is available for
             this article.},
   Doi = {10.1148/radiol.2017152852},
   Key = {fds326500}
}

@article{fds324467,
   Author = {Ria, F and Wilson, JM and Zhang, Y and Samei, E},
   Title = {Image noise and dose performance across a clinical
             population: Patient size adaptation as a metric of CT
             performance.},
   Journal = {Medical physics},
   Volume = {44},
   Number = {6},
   Pages = {2141-2147},
   Year = {2017},
   Month = {June},
   url = {http://dx.doi.org/10.1002/mp.12172},
   Abstract = {Modern CT systems adjust X-ray flux accommodating for
             patient size to achieve certain image noise values. The
             effectiveness of this adaptation is an important aspect of
             CT performance and should ideally be characterized in the
             context of real patient cases. The objective of this study
             was to characterize CT performance with a new metric that
             includes image noise and radiation dose across a clinical
             patient population.The study included 1526 examinations
             performed by three CT scanners (one GE Healthcare Discovery
             CT750HD, one GE Healthcare Lightspeed VCT, and one Siemens
             SOMATOM definition Flash) used for two routine clinical
             protocols (abdominopelvic with contrast and chest without
             contrast). An institutional monitoring system recorded all
             the data involved in the study. The dose-patient size and
             noise-patient size dependencies were linearized by
             considering a first-order approximation of analytical models
             that describe the relationship between ionization dose and
             patient size, as well as image noise and patient size. A
             3D-fit was performed for each protocol and each scanner with
             a planar function, and the root mean square error (RMSE)
             values were estimated as a metric of CT adaptability across
             the patient population.The data show different scanner
             dependencies in terms of adaptability: the RMSE values for
             the three scanners are between 0.0385 HU1/2 and 0.0215 HU1/2
             .A theoretical relationship between image noise, CTDIvol ,
             and patient size was determined based on real patient data.
             This relationship may be interpreted as a new metric related
             to the scanners' adaptability concerning image quality and
             radiation dose across a patient population. This method
             could be implemented to investigate the adaptability related
             to other image quality indexes and radiation dose in a
             clinical population.},
   Doi = {10.1002/mp.12172},
   Key = {fds324467}
}

@article{fds326625,
   Author = {Mileto, A and Nelson, RC and Larson, DG and Samei, E and Wilson, JM and Christianson, O and Marin, D and Boll, DT},
   Title = {Variability in Radiation Dose From Repeat Identical CT
             Examinations: Longitudinal Analysis of 2851 Patients
             Undergoing 12,635 Thoracoabdominal CT Scans in an Academic
             Health System.},
   Journal = {AJR. American journal of roentgenology},
   Volume = {208},
   Number = {6},
   Pages = {1285-1296},
   Year = {2017},
   Month = {June},
   url = {http://dx.doi.org/10.2214/ajr.16.17070},
   Abstract = {The purpose of this study was to conduct longitudinal
             analyses of radiation dose data from adult patients
             undergoing clinically indicated, repeat identical
             thoracoabdominal CT examinations.Radiation dose data were
             electronically collected from 2851 subjects undergoing
             12,635 repeat identical CT scans (mean number of scans per
             patient, 4.8; range, 2-33) in one health system. Included CT
             protocols were chest-abdomen-pelvis with contrast
             administration (n = 4621 CT studies of 1064 patients),
             abdomen-pelvis with contrast administration (n = 876 CT
             studies of 261 patients), renal stone (n = 1053 CT studies
             of 380 patients), and chest (n = 6085 CT studies of 1146
             patients) without contrast administration. A
             radiation-tracking software infrastructure was adopted to
             extract data from DICOM headers in PACS. Size-specific dose
             estimate (SSDE) was calculated.A trend was observed toward
             global reduction in SSDE values with all protocols
             investigated (chest-abdomen-pelvis slope, -1.78;
             abdomen-pelvis slope, -0.82; renal stone slope, -0.83; chest
             slope, -0.47; p < 0.001 for all comparisons). The
             intraindividual analyses of radiation dose distribution
             showed widespread variability in SSDE values across the four
             protocols investigated (chest-abdomen-pelvis mean
             coefficient of variance, 14.02 mGy; abdomen-pelvis mean
             coefficient of variance, 10.26 mGy; renal stone mean
             coefficient of variance, 34.18 mGy; chest mean coefficient
             of variance, 6.74 mGy).Although there is a trend toward
             global reduction in radiation doses, this study showed
             widespread variability in the radiation dose that each
             patient undergoing identical repeat thoracoabdominal CT
             protocols absorbs. These data may provide a foundation for
             the future development of best-practice guidelines for
             patient-specific radiation dose monitoring.},
   Doi = {10.2214/ajr.16.17070},
   Key = {fds326625}
}

@article{fds324793,
   Author = {Bellini, D and Ramirez-Giraldo, JC and Bibbey, A and Solomon, J and Hurwitz, LM and Farjat, A and Mileto, A and Samei, E and Marin,
             D},
   Title = {Dual-Source Single-Energy Multidetector CT Used to Obtain
             Multiple Radiation Exposure Levels within the Same Patient:
             Phantom Development and Clinical Validation.},
   Journal = {Radiology},
   Volume = {283},
   Number = {2},
   Pages = {526-537},
   Year = {2017},
   Month = {May},
   url = {http://dx.doi.org/10.1148/radiol.2016161233},
   Abstract = {Purpose To develop, in a phantom environment, a method to
             obtain multidetector computed tomographic (CT) data sets at
             multiple radiation exposure levels within the same patient
             and to validate its use for potential dose reduction by
             using different image reconstruction algorithms for the
             detection of liver metastases. Materials and Methods The
             American College of Radiology CT accreditation phantom was
             scanned by using a dual-source multidetector CT platform. By
             adjusting the radiation output of each tube, data sets at
             six radiation exposure levels (100%, 75%, 50%, 37.5%, 25%,
             and 12.5%) were reconstructed from two consecutive
             dual-source single-energy (DSSE) acquisitions, as well as a
             conventional single-source acquisition. A prospective,
             HIPAA-compliant, institutional review board-approved study
             was performed by using the same DSSE strategy in 19 patients
             who underwent multidetector CT of the liver for metastatic
             colorectal cancer. All images were reconstructed by using
             conventional weighted filtered back projection (FBP) and
             sinogram-affirmed iterative reconstruction with strength
             level of 3 (SAFIRE-3). Objective image quality metrics were
             compared in the phantom experiment by using multiple linear
             regression analysis. Generalized linear mixed-effects models
             were used to analyze image quality metrics and diagnostic
             performance for lesion detection by readers. Results The
             phantom experiment showed comparable image quality between
             DSSE and conventional single-source acquisition. In the
             patient study, the mean size-specific dose estimates for the
             six radiation exposure levels were 13.0, 9.8, 5.8, 4.4, 3.2,
             and 1.4 mGy. For each radiation exposure level, readers'
             perception of image quality and lesion conspicuity was
             consistently ranked superior with SAFIRE-3 when compared
             with FBP (P ≤ .05 for all comparisons). Reduction of up to
             62.5% in radiation exposure by using SAFIRE-3 yielded
             similar reader rankings of image quality and lesion
             conspicuity when compared with routine-dose FBP. Conclusion
             A method was developed and validated to synthesize
             multidetector CT data sets at multiple radiation exposure
             levels within the same patient. This technique may provide a
             foundation for future clinical trials aimed at estimating
             potential radiation dose reduction by using iterative
             reconstructions. © RSNA, 2016 Online supplemental material
             is available for this article.},
   Doi = {10.1148/radiol.2016161233},
   Key = {fds324793}
}

@article{fds324789,
   Author = {Zhang, Y and Smitherman, C and Samei, E},
   Title = {Size-specific optimization of CT protocols based on minimum
             detectability.},
   Journal = {Medical physics},
   Volume = {44},
   Number = {4},
   Pages = {1301-1311},
   Year = {2017},
   Month = {April},
   url = {http://dx.doi.org/10.1002/mp.12125},
   Abstract = {To develop a comprehensive model of task-based performance
             of CT across a broad library of CT protocols, so that
             radiation dose and image quality can be optimized within a
             large multivendor clinical facility.Eighty adult CT
             protocols from the Duke University Medical Center were
             grouped into 23 protocol groups with similar acquisition
             characteristics. A size-based image quality phantom (Duke
             Mercury Phantom 2.0) was imaged using these protocol groups
             for a range of clinically relevant dose levels on two CT
             manufacturer platforms (Siemens SOMATOM Definition Flash and
             GE CT750 HD). For each protocol group, phantom size, and
             dose level, the images were analyzed to extract task-based
             image quality metrics, the task transfer function (TTF), and
             the noise power spectrum (NPS). The TTF and NPS were further
             combined with generalized models of lesion task functions to
             predict the detectability of the lesions in terms of areas
             under the receiver operating characteristic curve (Az ). A
             graphical user interface (GUI) was developed to present Az
             as a function of lesion size and contrast, dose, patient
             size, and protocol, as well as to derive the necessary dose
             to achieve a detection threshold for a targeted lesion.The
             GUI provided the prediction of Az values modeling detection
             confidence for a targeted lesion, patient size, and dose. As
             an example, an abdomen pelvis exam for one scanner, with a
             reference task size/contrast of 5-mm/50-HU, and an Az of 0.9
             indicated a dose requirement of 4.0, 8.9, and 16.9 mGy for
             patient diameters of 25, 30, and 35 cm, respectively. For a
             constant patient diameter of 30 cm and 50-HU lesion
             contrast, the minimum detected lesion size at those dose
             levels were predicted to be 8.4, 5.0, and 3.9 mm,
             respectively.A CT protocol optimization platform was
             developed by combining task-based detectability calculations
             with a GUI that demonstrates the tradeoff between dose and
             image quality. The platform can be used to improve
             individual protocol dose efficiency, as well as to improve
             protocol consistency across various patient sizes and CT
             scanners.},
   Doi = {10.1002/mp.12125},
   Key = {fds324789}
}

@article{fds324792,
   Author = {Fu, W and Tian, X and Sturgeon, GM and Agasthya, G and Segars, WP and Goodsitt, MM and Kazerooni, EA and Samei, E},
   Title = {CT breast dose reduction with the use of breast positioning
             and organ-based tube current modulation.},
   Journal = {Medical physics},
   Volume = {44},
   Number = {2},
   Pages = {665-678},
   Year = {2017},
   Month = {February},
   url = {http://dx.doi.org/10.1002/mp.12076},
   Abstract = {This study aimed to investigate the breast dose reduction
             potential of a breast-positioning (BP) technique for
             thoracic CT examinations with organ-based tube current
             modulation (OTCM).This study included 13 female
             anthropomorphic computational phantoms (XCAT, age range:
             27-65 y.o., weight range: 52-105.8 kg). Each phantom was
             modified to simulate three breast sizes in standard supine
             geometry. The modeled breasts were then morphed to emulate
             BP that constrained the majority of the breast tissue inside
             the 120° anterior tube current (mA) reduction zone. The
             OTCM mA value was modeled using a ray-tracing program, which
             reduced the mA to 20% in the anterior region with a
             corresponding increase to the posterior region. The organ
             doses were estimated by a validated Monte Carlo program for
             a typical clinical CT system (SOMATOM Definition Flash,
             Siemens Healthcare). The simulated organ doses and organ
             doses normalized by CTDIvol were used to compare three CT
             protocols: attenuation-based tube current modulation (ATCM),
             OTCM, and OTCM with BP (OTCMBP ).On average, compared to
             ATCM, OTCM reduced breast dose by 19.3 ± 4.5%, whereas
             OTCMBP reduced breast dose by 38.6 ± 8.1% (an additional
             23.8 ± 9.4%). The dose saving of OTCMBP was more
             significant for larger breasts (on average 33, 38, and 44%
             reduction for 0.5, 1, and 2 kg breasts, respectively).
             Compared to ATCM, OTCMBP also reduced thymus and heart dose
             by 15.1 ± 7.4% and 15.9 ± 6.2% respectively.In
             thoracic CT examinations, OTCM with a breast-positioning
             technique can markedly reduce unnecessary exposure to
             radiosensitive organs in anterior chest wall, specifically
             breast tissue. The breast dose reduction is more notable for
             women with larger breasts.},
   Doi = {10.1002/mp.12076},
   Key = {fds324792}
}

@article{fds324790,
   Author = {Sanders, J and Tian, X and Segars, WP and Boone, J and Samei,
             E},
   Title = {Automated, patient-specific estimation of regional imparted
             energy and dose from tube current modulated computed
             tomography exams across 13 protocols.},
   Journal = {Journal of medical imaging (Bellingham, Wash.)},
   Volume = {4},
   Number = {1},
   Pages = {013503},
   Year = {2017},
   Month = {January},
   url = {http://dx.doi.org/10.1117/1.jmi.4.1.013503},
   Abstract = {Currently, computed tomography (CT) dosimetry relies on
             surrogates for dose, such as CT dose index and size-specific
             dose estimates, rather than dose per se. Organ dose is
             considered as the gold standard for radiation dosimetry.
             However, organ dose estimation requires precise knowledge of
             organ locations. Regional imparted energy and dose can also
             be used to quantify radiation burden and are beneficial
             because they do not require knowledge of organ size or
             location. This work investigated an automated technique to
             retrospectively estimate the imparted energy from tube
             current-modulated (TCM) CT exams across 13 protocols. Monte
             Carlo simulations of various head and body TCM CT
             examinations across various tube potentials and TCM
             strengths were performed on 58 adult computational extended
             cardiac-torso phantoms to develop relationships between
             scanned mass and imparted energy normalized by dose length
             product. Results from the Monte Carlo simulations indicate
             that normalized imparted energy increases with increasing
             both scanned mass and tube potential, but it is relatively
             unaffected by the strength of the TCM. The automated
             algorithm was tested on 40 clinical datasets with a 98%
             success rate.},
   Doi = {10.1117/1.jmi.4.1.013503},
   Key = {fds324790}
}

@article{fds326785,
   Author = {Ria, F and Wilson, JM and Zhang, Y and Samei, E},
   Title = {Adaptability index: Quantifying CT tube current modulation
             performance from dose and quality informatics},
   Journal = {Proceedings of SPIE},
   Volume = {10132},
   Year = {2017},
   Month = {January},
   ISBN = {9781510607095},
   url = {http://dx.doi.org/10.1117/12.2255631},
   Abstract = {© 2017 SPIE. The balance between risk and benefit in modern
             CT scanners is governed by the automatic adaptation
             mechanisms that adjust x-ray flux for accommodating patient
             size to achieve certain image noise values. The
             effectiveness of this adaptation is an important aspect of
             CT performance and should ideally be characterized in the
             context of real patient cases. Objective of this study was
             to characterize CT performance with an index that includes
             image-noise and radiation dose across a clinical patient
             population. The study included 1526 examinations performed
             by three scanners, from two vendors, used for two clinical
             protocols (abdominopelvic and chest). The dose-patient size
             and noise-patient size dependencies were linearized, and a
             3D-fit was performed for each protocol and each scanner with
             a planar function. In the fit residual plots the Root Mean
             Square Error (RMSE) values were estimated as a metric of CT
             adaptability across the patient population. The RMSE values
             were between 0.0344 HU 1/2 and 0.0215 HU 1/2 : different
             scanners offer varying degrees of reproducibility of noise
             and dose across the population. This analysis could be
             performed with phantoms, but phantom data would only provide
             information concerning specific exposure parameters for a
             scan: instead, a general population comparison is a way to
             obtain new information related to the relevant clinical
             adaptability of scanner models. A theoretical relationship
             between image noise, CTD Ivol and patient size was
             determined based on real patient data. This relationship may
             provide a new index related to the scanners' adaptability
             concerning image quality and radiation dose across a patient
             population.},
   Doi = {10.1117/12.2255631},
   Key = {fds326785}
}

@article{fds326844,
   Author = {Hoye, J and Zhang, Y and Agasthya, G and Sturgeon, G and Kapadia, A and Segars, WP and Samei, E},
   Title = {An atlas-based organ dose estimator for tomosynthesis and
             radiography},
   Journal = {Proceedings of SPIE},
   Volume = {10132},
   Year = {2017},
   Month = {January},
   ISBN = {9781510607095},
   url = {http://dx.doi.org/10.1117/12.2255583},
   Abstract = {© 2017 SPIE. The purpose of this study was to provide
             patient-specific organ dose estimation based on an atlas of
             human models for twenty tomosynthesis and radiography
             protocols. The study utilized a library of 54 adult
             computational phantoms (age: 18-78 years, weight 52-117 kg)
             and a validated Monte-Carlo simulation (PENELOPE) of a
             tomosynthesis and radiography system to estimate organ dose.
             Positioning of patient anatomy was based on radiographic
             positioning handbooks. The field of view for each exam was
             calculated to include relevant organs per protocol. Through
             simulations, the energy deposited in each organ was binned
             to estimate normalized organ doses into a reference
             database. The database can be used as the basis to devise a
             dose calculator to predict patient-specific organ dose
             values based on kVp, mAs, exposure in air, and patient
             habitus for a given protocol. As an example of the utility
             of this tool, dose to an organ was studied as a function of
             average patient thickness in the field of view for a given
             exam and as a function of Body Mass Index (BMI). For
             tomosynthesis, organ doses can also be studied as a function
             of x-ray tube position. This work developed comprehensive
             information for organ dose dependencies across tomosynthesis
             and radiography. There was a general exponential decrease
             dependency with increasing patient size that is highly
             protocol dependent. There was a wide range of variability in
             organ dose across the patient population, which needs to be
             incorporated in the metrology of organ dose.},
   Doi = {10.1117/12.2255583},
   Key = {fds326844}
}

@article{fds326786,
   Author = {Zhao, C and Solomon, J and Sturgeon, GM and Gehm, ME and Catenacci, M and Wiley, BJ and Samei, E and Lo, JY},
   Title = {Third generation anthropomorphic physical phantom for
             mammography and DBT: Incorporating voxelized 3D printing and
             uniform chest wall QC region},
   Journal = {Proceedings of SPIE},
   Volume = {10132},
   Year = {2017},
   Month = {January},
   ISBN = {9781510607095},
   url = {http://dx.doi.org/10.1117/12.2256091},
   Abstract = {© 2017 SPIE. Physical breast phantoms provide a standard
             method to test, optimize, and develop clinical mammography
             systems, including new digital breast tomosynthesis (DBT)
             systems. In previous work, we produced an anthropomorphic
             phantom based on 500x500x500 μm breast CT data using
             commercial 3D printing. We now introduce an improved phantom
             based on a new cohort of virtual models with 155x155x155 μm
             voxels and fabricated through voxelized 3D printing and
             dithering, which confer higher resolution and greater
             control over contrast. This new generation includes a
             uniform chest wall extension for evaluating conventional QC
             metrics. The uniform region contains a grayscale step wedge,
             chest wall coverage markers, fiducial markers, spheres, and
             metal ink stickers of line pairs and edges to assess
             contrast, resolution, artifact spread function, MTF, and
             other criteria. We also experimented with doping
             photopolymer material with calcium, iodine, and zinc to
             increase our current contrast. In particular, zinc was
             discovered to significantly increase attenuation beyond 100%
             breast density with a linear relationship between zinc
             concentration and attenuation or breast density. This linear
             relationship was retained when the zinc-doped material was
             applied in conjunction with 3D printing. As we move towards
             our long term goal of phantoms that are indistinguishable
             from patients, this new generation of anthropomorphic
             physical breast phantom validates our voxelized printing
             process, demonstrates the utility of a uniform QC region
             with features from 3D printing and metal ink stickers, and
             shows potential for improved contrast via
             doping.},
   Doi = {10.1117/12.2256091},
   Key = {fds326786}
}

@article{fds326845,
   Author = {Fu, W and Sturgeon, GM and Agasthya, G and Segars, WP and Kapadia, AJ and Samei, E},
   Title = {Estimation of breast dose reduction potential for
             organ-based tube current modulated CT with wide dose
             reduction arc},
   Journal = {Proceedings of SPIE},
   Volume = {10132},
   Year = {2017},
   Month = {January},
   ISBN = {9781510607095},
   url = {http://dx.doi.org/10.1117/12.2255797},
   Abstract = {© 2017 SPIE. This study aimed to estimate the organ dose
             reduction potential for organ-dose-based tube current
             modulated (ODM) thoracic CT with wide dose reduction arc.
             Twenty-one computational anthropomorphic phantoms (XCAT, age
             range: 27- 75 years, weight range: 52.0-105.8 kg) were used
             to create a virtual patient population with clinical
             anatomic variations. For each phantom, two breast tissue
             compositions were simulated: 50/50 and 20/80
             (glandular-to-adipose ratio). A validated Monte Carlo
             program was used to estimate the organ dose for standard
             tube current modulation (TCM) (SmartmA, GE Healthcare) and
             ODM (GE Healthcare) for a commercial CT scanner (Revolution,
             GE Healthcare) with explicitly modeled tube current
             modulation profile, scanner geometry, bowtie filtration, and
             source spectrum. Organ dose was determined using a typical
             clinical thoracic CT protocol. Both organ dose and CTDI vol
             -to-organ dose conversion coefficients (h factors) were
             compared between TCM and ODM. ODM significantly reduced all
             radiosensitive organ doses (p < 0.01). The breast dose was
             reduced by 30±2%. For h factors, organs in the anterior
             region (e.g. thyroid, stomach) exhibited substantial
             decreases, and the medial, distributed, and posterior region
             either saw an increase or no significant change. The
             organ-dose-based tube current modulation significantly
             reduced organ doses especially for radiosensitive
             superficial anterior organs such as the breasts.},
   Doi = {10.1117/12.2255797},
   Key = {fds326845}
}

@article{fds326846,
   Author = {Abadi, E and Sturgeon, GM and Agasthya, G and Harrawood, B and Hoeschen,
             C and Kapadia, A and Segars, WP and Samei, E},
   Title = {Airways, vasculature, and interstitial tissue: Anatomically
             informed computational modeling of human lungs for virtual
             clinical trials},
   Journal = {Proceedings of SPIE},
   Volume = {10132},
   Year = {2017},
   Month = {January},
   ISBN = {9781510607095},
   url = {http://dx.doi.org/10.1117/12.2254739},
   Abstract = {© 2017 SPIE. This study aimed to model virtual human lung
             phantoms including both non-parenchymal and parenchymal
             structures. Initial branches of the non-parenchymal
             structures (airways, arteries, and veins) were segmented
             from anatomical data in each lobe separately. A
             volume-filling branching algorithm was utilized to grow the
             higher generations of the airways and vessels to the level
             of terminal branches. The diameters of the airways and
             vessels were estimated using established relationships
             between flow rates and diameters. The parenchyma was modeled
             based on secondary pulmonary lobule units. Polyhedral shapes
             with variable sizes were modeled, and the borders were
             assigned to interlobular septa. A heterogeneous background
             was added inside these units using a non-parametric texture
             synthesis algorithm which was informed by a high-resolution
             CT lung specimen dataset. A voxelized based CT simulator was
             developed to create synthetic helical CT images of the
             phantom with different pitch values. Results showed the
             progressive degradation in depiction of lung details with
             increased pitch. Overall, the enhanced lung models combined
             with the XCAT phantoms prove to provide a powerful toolset
             to perform virtual clinical trials in the context of
             thoracic imaging. Such trials, not practical using clinical
             datasets or simplistic phantoms, can quantitatively evaluate
             and optimize advanced imaging techniques towards
             patient-based care.},
   Doi = {10.1117/12.2254739},
   Key = {fds326846}
}

@article{fds326847,
   Author = {Zheng, Y and Solomon, J and Choudhury, K and Marin, D and Samei,
             E},
   Title = {Accuracy and variability of texture-based radiomics features
             of lung lesions across CT imaging conditions},
   Journal = {Proceedings of SPIE},
   Volume = {10132},
   Year = {2017},
   Month = {January},
   ISBN = {9781510607095},
   url = {http://dx.doi.org/10.1117/12.2255806},
   Abstract = {© 2017 SPIE. Texture analysis for lung lesions is sensitive
             to changing imaging conditions but these effects are not
             well understood, in part, due to a lack of ground-truth
             phantoms with realistic textures. The purpose of this study
             was to explore the accuracy and variability of texture
             features across imaging conditions by comparing imaged
             texture features to voxel-based 3D printed textured lesions
             for which the true values are known. The seven features of
             interest were based on the Grey Level Co-Occurrence Matrix
             (GLCM). The lesion phantoms were designed with three shapes
             (spherical, lobulated, and spiculated), two textures
             (homogenous and heterogeneous), and two sizes (diameter <
             1.5 cm and 1.5 cm < diameter < 3 cm), resulting in 24
             lesions (with a second replica of each). The lesions were
             inserted into an anthropomorphic thorax phantom
             (Multipurpose Chest Phantom N1, Kyoto Kagaku) and imaged
             using a commercial CT system (GE Revolution) at three CTDI
             levels (0.67, 1.42, and 5.80 mGy), three reconstruction
             algorithms (FBP, IR-2, IR-4), four reconstruction kernel
             types (standard, soft, edge), and two slice thicknesses (0.6
             mm and 5 mm). Another repeat scan was performed. Texture
             features from these images were extracted and compared to
             the ground truth feature values by percent relative error.
             The variability across imaging conditions was calculated by
             standard deviation across a certain imaging condition for
             all heterogeneous lesions. The results indicated that the
             acquisition method has a significant influence on the
             accuracy and variability of extracted features and as such,
             feature quantities are highly susceptible to imaging
             parameter choices. The most influential parameters were
             slice thickness and reconstruction kernels. Thin slice
             thickness and edge reconstruction kernel overall produced
             more accurate and more repeatable results. Some features
             (e.g., Contrast) were more accurately quantified under
             conditions that render higher spatial frequencies (e.g.,
             thinner slice thickness and sharp kernels), while others
             (e.g., Homogeneity) showed more accurate quantification
             under conditions that render smoother images (e.g., higher
             dose and smoother kernels). Care should be exercised is
             relating texture features between cases of varied
             acquisition protocols, with need to cross calibration
             dependent on the feature of interest.},
   Doi = {10.1117/12.2255806},
   Key = {fds326847}
}

@article{fds326848,
   Author = {Solomon, J and Rubin, G and Smith, T and Harrawood, B and Choudhury, KR and Samei, E},
   Title = {Development of local complexity metrics to quantify the
             effect of anatomical noise on detectability of lung nodules
             in chest CT imaging},
   Journal = {Proceedings of SPIE},
   Volume = {10136},
   Year = {2017},
   Month = {January},
   ISBN = {9781510607170},
   url = {http://dx.doi.org/10.1117/12.2254044},
   Abstract = {© 2017 SPIE. The purpose of this study was to develop
             metrics of local anatomical complexity and compare them with
             detectability of lung nodules in CT. Data were drawn
             retrospectively from a published perception experiment in
             which detectability was assessed in cases enriched with
             virtual nodules (13 radiologists x 157 total nodules = 2041
             responses). A local anatomical complexity metric called the
             distractor index was developed, defined as the Gaussian
             weighted proportion (i.e., average) of distracting local
             voxels (50 voxels in-plane, 5 slices). A distracting voxel
             was classified by thresholding image data that had been
             selectively filtered to enhance nodule-like features. The
             distractor index was measured for each nodule location in
             the nodule-free images. The local pixel standard deviation
             (STD) was also measured for each nodule. Other confounding
             factors of search fraction (proportion of lung voxels to
             total voxels in the given slice) and peripheral distance
             (defined as the 3D distance of the nodule from the trachea
             bifurcation) were measured. A generalized linear
             mixed-effects statistical model (no interaction terms,
             probit link function, random reader term) was fit to the
             data to determine the influence of each metric on
             detectability. In order of decreasing effect size:
             distractor index, STD, and search fraction all significantly
             affected detectability (P < 0.001). Distance to the trachea
             did not have a significant effect (P > 0.05). These data
             demonstrate that local lung complexity degrades detection of
             lung nodules and the distractor index could serve as a good
             surrogate metric to quantify anatomical complexity.},
   Doi = {10.1117/12.2254044},
   Key = {fds326848}
}

@article{fds326849,
   Author = {Richards, T and Sturgeon, GM and Ramirez-Giraldo, JC and Rubin, G and Segars, P and Samei, E},
   Title = {Quantification of the uncertainty in coronary CTA plaque
             measurements using dynamic cardiac phantom and 3D-printed
             plaque models},
   Journal = {Proceedings of SPIE},
   Volume = {10132},
   Year = {2017},
   Month = {January},
   ISBN = {9781510607095},
   url = {http://dx.doi.org/10.1117/12.2255592},
   Abstract = {© 2017 SPIE. The purpose of this study was to quantify the
             accuracy of coronary computed tomography angiography (CTA)
             stenosis measurements using newly developed physical
             coronary plaque models attached to a base dynamic cardiac
             phantom (Shelley Medical DHP-01). Coronary plaque models (5
             mm diameter, 50% stenosis, and 32 mm long) were designed and
             3D-printed with tissue equivalent materials (calcified
             plaque with iodine enhanced lumen). Realistic cardiac motion
             was achieved by fitting known cardiac motion vectors to left
             ventricle volume-time curves to create synchronized heart
             motion profiles executed by the base cardiac phantom.
             Realistic coronary CTA acquisition was accomplished by
             synthesizing corresponding ECG waveforms for gating and
             reconstruction purposes. All scans were acquired using a
             retrospective gating technique on a dual-source CT system
             (Siemens SOMATOM FLASH) with 75ms temporal resolution.
             Multi-planar reformatted images were reconstructed along
             vessel centerlines and the enhanced lumens were manually
             segmented by 5 independent operators. On average, the
             stenosis measurement accuracy was 0.9% positive bias for the
             motion free condition (0 bpm). The measurement accuracy
             monotonically decreased to 18.5% negative bias at 90 bpm.
             Contrast-tonoise (CNR), vessel circularity, and segmentation
             conformity also decreased monotonically with increasing
             heart rate. These results demonstrate successful
             implementation of the base cardiac phantom with 3D-printed
             coronary plaque models, adjustable motion profiles, and
             coordinated ECG waveforms. They further show the utility of
             the model to ascertain metrics of coronary CT accuracy and
             image quality under a variety of plaque, motion, and
             acquisition conditions.},
   Doi = {10.1117/12.2255592},
   Key = {fds326849}
}

@article{fds326850,
   Author = {Sturgeon, GM and Richards, TW and Samei, E and Segars,
             WP},
   Title = {Improved virtual cardiac phantom with variable diastolic
             filling rates and coronary artery velocities},
   Journal = {Proceedings of SPIE},
   Volume = {10132},
   Year = {2017},
   Month = {January},
   ISBN = {9781510607095},
   url = {http://dx.doi.org/10.1117/12.2255572},
   Abstract = {© 2017 SPIE. To facilitate studies of measurement
             uncertainty in computed tomography angiography (CTA), we
             investigated the cardiac motion profile and resulting
             coronary artery motion utilizing innovative dynamic virtual
             and physical phantoms. The four-chamber cardiac finite
             element (FE) model developed in the Living Heart Project
             (LHP) served as the computational basis for our virtual
             cardiac phantom. This model provides deformation or strain
             information at high temporal and spatial resolution,
             exceeding that of speckle tracking echocardiography or
             tagged MRI. This model was extended by fitting its motion
             profile to left ventricular (LV) volume-time curves obtained
             from patient echocardiography data. By combining the dynamic
             patient variability from echo with the local strain
             information from the FE model, a series of virtual 4D
             cardiac phantoms were developed. Using the computational
             phantoms, we characterized the coronary motion and its
             effect on plaque imaging under a range of heart rates
             subject to variable diastolic function. The coronary artery
             motion was sampled at 248 spatial locations over 500
             consecutive time frames. The coronary artery velocities were
             calculated as their average velocity during an acquisition
             window centered at each time frame, which minimized the
             discretization error. For the initial set of twelve
             patients, the diastatic coronary artery velocity ranged from
             36.5 mm/s to 2.0 mm/s with a mean of 21.4 mm/s assuming an
             acquisition time of 75 ms. The developed phantoms have great
             potential in modeling cardiac imaging, providing a known
             truth and multiple realistic cardiac motion profiles to
             evaluate different image acquisition or reconstruction
             methods.},
   Doi = {10.1117/12.2255572},
   Key = {fds326850}
}

@article{fds326851,
   Author = {Smith, TB and Solomon, J and Samei, E},
   Title = {In-vivo detectability index: Development and validation of
             an automated methodology},
   Journal = {Proceedings of SPIE},
   Volume = {10132},
   Year = {2017},
   Month = {January},
   ISBN = {9781510607095},
   url = {http://dx.doi.org/10.1117/12.2255411},
   Abstract = {© 2017 SPIE. The purpose of this study was to develop and
             validate a method to estimate patient-specific detectability
             indices directly from patients' CT images (i.e., "in vivo").
             The method works by automatically extracting noise (NPS) and
             resolution (MTF) properties from each patient's CT series
             based on previously validated techniques. Patient images are
             thresholded into skin-air interfaces to form edge-spread
             functions, which are further binned, differentiated, and
             Fourier transformed to form the MTF. The NPS is likewise
             estimated from uniform areas of the image. These are
             combined with assumed task functions (reference function: 10
             mm disk lesion with contrast of -15 HU) to compute
             detectability indices for a non-prewhitening matched filter
             model observer predicting observer performance. The results
             were compared to those from a previous human detection study
             on 105 subtle, hypo-attenuating liver lesions, using a
             two-alternative-forcedchoice (2AFC) method, over 6 dose
             levels using 16 readers. The in vivo detectability indices
             estimated for all patient images were compared to binary
             2AFC outcomes with a generalized linear mixed-effects
             statistical model (Probit link function, linear terms only,
             no interactions, random term for readers). The model showed
             that the in vivo detectability indices were strongly
             predictive of 2AFC outcomes (P < 0.05). A linear comparison
             between the human detection accuracy and model-predicted
             detection accuracy (for like conditions) resulted in Pearson
             and Spearman correlations coefficients of 0.86 and 0.87,
             respectively. These data provide evidence that the in vivo
             detectability index could potentially be used to
             automatically estimate and track image quality in a clinical
             operation.},
   Doi = {10.1117/12.2255411},
   Key = {fds326851}
}

@article{fds326852,
   Author = {Zhao, A and Santana, M and Samei, E and Lo, J},
   Title = {Comparison of effects of dose on image quality in digital
             breast tomosynthesis across multiple vendors},
   Journal = {Proceedings of SPIE},
   Volume = {10132},
   Year = {2017},
   Month = {January},
   ISBN = {9781510607095},
   url = {http://dx.doi.org/10.1117/12.2255570},
   Abstract = {© 2017 SPIE. In traditional radiography and computed
             tomography (CT), contrast is an important measure of image
             quality that, in theory, does not vary with dose. While
             increasing dose may increase the overall contrast-to-noise
             ratio (CNR), the contrast in an image should be primarily
             dependent on variation in tissue density and attenuation. We
             investigated the behavior of all three currently
             FDA-approved vendors' 3D DBT systems (Siemens, Hologic, and
             General Electric (GE)) using the Computerized Imaging
             Reference Systems (CIRS) Model 011A Breast Phantom and found
             that for both Siemens and Hologic systems, contrast
             increased with dose across multiple repeated trials. For
             these two systems, experimental CNR also appeared to
             increase above the expected CNR, which suggests that these
             systems seem to have introduced post-processing by
             manipulation of contrast, and thus DBT data cannot be used
             to reliably quantify tissue characteristics. Additional
             experimentation with both 2D mammography and 3D DBT systems
             from GE in addition to the previously mentioned vendors,
             however, suggested that this relationship is not true for
             all systems. An initial comparison of contrast vs. dose
             showed no relationship between contrast and dose for 2D
             mammography, with the contrast remaining relatively constant
             in the dose range of 33% of the automatic exposure control
             setting (AEC) to 300% AEC for all three vendors. The GE DBT
             system also did not exhibit increased contrast with
             increased dose, suggesting that the behavior of 3D DBT
             systems is vendor-specific.},
   Doi = {10.1117/12.2255570},
   Key = {fds326852}
}

@article{fds326853,
   Author = {Robins, M and Solomon, J and Hoye, J and Smith, T and Ebner, L and Samei,
             E},
   Title = {Inter-algorithm lesion volumetry comparison of real and 3D
             simulated lung lesions in CT},
   Journal = {Proceedings of SPIE},
   Volume = {10132},
   Year = {2017},
   Month = {January},
   ISBN = {9781510607095},
   url = {http://dx.doi.org/10.1117/12.2254219},
   Abstract = {© 2017 SPIE. The purpose of this study was to establish
             volumetric exchangeability between real and computational
             lung lesions in CT. We compared the overall relative volume
             estimation performance of segmentation tools when used to
             measure real lesions in actual patient CT images and
             computational lesions virtually inserted into the same
             patient images (i.e., hybrid datasets). Pathologically
             confirmed malignancies from 30 thoracic patient cases from
             Reference Image Database to Evaluate Therapy Response
             (RIDER) were modeled and used as the basis for the
             comparison. Lesions included isolated nodules as well as
             those attached to the pleura or other lung structures.
             Patient images were acquired using a 16 detector row or 64
             detector row CT scanner (Lightspeed 16 or VCT; GE
             Healthcare). Scans were acquired using standard chest
             protocols during a single breath-hold. Virtual 3D lesion
             models based on real lesions were developed in Duke Lesion
             Tool (Duke University), and inserted using a validated
             image-domain insertion program. Nodule volumes were
             estimated using multiple commercial segmentation tools
             (iNtuition, TeraRecon, Inc., Syngo.via, Siemens Healthcare,
             and IntelliSpace, Philips Healthcare). Consensus based
             volume comparison showed consistent trends in volume
             measurement between real and virtual lesions across all
             software. The average percent bias (± standard error) shows
             -9.2±3.2% for real lesions versus -6.7±1.2% for virtual
             lesions with tool A, 3.9±2.5% and 5.0±0.9% for tool B, and
             5.3±2.3% and 1.8±0.8% for tool C, respectively. Virtual
             lesion volumes were statistically similar to those of real
             lesions ( < 4% difference) with p > .05 in most cases.
             Results suggest that hybrid datasets had similar
             inter-algorithm variability compared to real
             datasets.},
   Doi = {10.1117/12.2254219},
   Key = {fds326853}
}

@article{fds323724,
   Author = {Mileto, A and Samei, E},
   Title = {Hallway Conversations in Physics.},
   Journal = {AJR. American journal of roentgenology},
   Volume = {208},
   Number = {1},
   Pages = {W24-W27},
   Year = {2017},
   Month = {January},
   url = {http://dx.doi.org/10.2214/ajr.16.16462},
   Doi = {10.2214/ajr.16.16462},
   Key = {fds323724}
}

@article{fds325759,
   Author = {Lakshmanan, MN and Greenberg, JA and Samei, E and Kapadia,
             AJ},
   Title = {Accuracy assessment and characterization of x-ray coded
             aperture coherent scatter spectral imaging for breast cancer
             classification.},
   Journal = {Journal of medical imaging (Bellingham, Wash.)},
   Volume = {4},
   Number = {1},
   Pages = {013505},
   Year = {2017},
   Month = {January},
   url = {http://dx.doi.org/10.1117/1.jmi.4.1.013505},
   Abstract = {Although transmission-based x-ray imaging is the most
             commonly used imaging approach for breast cancer detection,
             it exhibits false negative rates higher than 15%. To improve
             cancer detection accuracy, x-ray coherent scatter computed
             tomography (CSCT) has been explored to potentially detect
             cancer with greater consistency. However, the 10-min scan
             duration of CSCT limits its possible clinical applications.
             The coded aperture coherent scatter spectral imaging
             (CACSSI) technique has been shown to reduce scan time
             through enabling single-angle imaging while providing high
             detection accuracy. Here, we use Monte Carlo simulations to
             test analytical optimization studies of the CACSSI
             technique, specifically for detecting cancer in ex vivo
             breast samples. An anthropomorphic breast tissue phantom was
             modeled, a CACSSI imaging system was virtually simulated to
             image the phantom, a diagnostic voxel classification
             algorithm was applied to all reconstructed voxels in the
             phantom, and receiver-operator characteristics analysis of
             the voxel classification was used to evaluate and
             characterize the imaging system for a range of parameters
             that have been optimized in a prior analytical study. The
             results indicate that CACSSI is able to identify the
             distribution of cancerous and healthy tissues (i.e.,
             fibroglandular, adipose, or a mix of the two) in tissue
             samples with a cancerous voxel identification
             area-under-the-curve of 0.94 through a scan lasting less
             than 10 s per slice. These results show that coded aperture
             scatter imaging has the potential to provide scatter images
             that automatically differentiate cancerous and healthy
             tissue within ex vivo samples. Furthermore, the results
             indicate potential CACSSI imaging system configurations for
             implementation in subsequent imaging development
             studies.},
   Doi = {10.1117/1.jmi.4.1.013505},
   Key = {fds325759}
}

@article{fds329838,
   Author = {Abadi, E and Segars, WP and Sturgeon, GM and Roos, JE and Ravin, CE and Samei, E},
   Title = {Modeling Lung Architecture in the XCAT Series of Phantoms:
             Physiologically Based Airways, Arteries and
             Veins},
   Journal = {IEEE Transactions on Medical Imaging},
   Pages = {1-1},
   Year = {2017},
   url = {http://dx.doi.org/10.1109/TMI.2017.2769640},
   Doi = {10.1109/TMI.2017.2769640},
   Key = {fds329838}
}

@article{fds329139,
   Author = {Segars, WP and Tsui, BMW and Cai, J and Yin, F-F and Fung, GSK and Samei,
             E},
   Title = {Application of the 4D XCAT Phantoms in Biomedical Imaging
             and Beyond},
   Journal = {IEEE Transactions on Medical Imaging},
   Pages = {1-1},
   Year = {2017},
   url = {http://dx.doi.org/10.1109/TMI.2017.2738448},
   Doi = {10.1109/TMI.2017.2738448},
   Key = {fds329139}
}

@article{fds322724,
   Author = {Solomon, J and Ba, A and Bochud, F and Samei, E},
   Title = {Comparison of low-contrast detectability between two CT
             reconstruction algorithms using voxel-based 3D printed
             textured phantoms.},
   Journal = {Medical physics},
   Volume = {43},
   Number = {12},
   Pages = {6497},
   Year = {2016},
   Month = {December},
   url = {http://dx.doi.org/10.1118/1.4967478},
   Abstract = {To use novel voxel-based 3D printed textured phantoms in
             order to compare low-contrast detectability between two
             reconstruction algorithms, FBP (filtered-backprojection) and
             SAFIRE (sinogram affirmed iterative reconstruction) and
             determine what impact background texture (i.e., anatomical
             noise) has on estimating the dose reduction potential of
             SAFIRE.Liver volumes were segmented from 23 abdominal CT
             cases. The volumes were characterized in terms of texture
             features from gray-level co-occurrence and run-length
             matrices. Using a 3D clustered lumpy background (CLB) model,
             a fitting technique based on a genetic optimization
             algorithm was used to find CLB textures that were reflective
             of the liver textures, accounting for CT system factors of
             spatial blurring and noise. With the modeled background
             texture as a guide, four cylindrical phantoms (Textures A-C
             and uniform, 165 mm in diameter, and 30 mm height) were
             designed, each containing 20 low-contrast spherical signals
             (6 mm diameter at nominal contrast levels of ∼3.2, 5.2,
             7.2, 10, and 14 HU with four repeats per signal). The
             phantoms were voxelized and input into a commercial
             multimaterial 3D printer (Object Connex 350), with custom
             software for voxel-based printing (using principles of
             digital dithering). Images of the textured phantoms and a
             corresponding uniform phantom were acquired at six radiation
             dose levels (SOMATOM Flash, Siemens Healthcare) and observer
             model detection performance (detectability index of a
             multislice channelized Hotelling observer) was estimated for
             each condition (5 contrasts × 6 doses × 2 reconstructions
             × 4 backgrounds = 240 total conditions). A multivariate
             generalized regression analysis was performed (linear terms,
             no interactions, random error term, log link function) to
             assess whether dose, reconstruction algorithm, signal
             contrast, and background type have statistically significant
             effects on detectability. Also, fitted curves of
             detectability (averaged across contrast levels) as a
             function of dose were constructed for each reconstruction
             algorithm and background texture. FBP and SAFIRE were
             compared for each background type to determine the
             improvement in detectability at a given dose, and the
             reduced dose at which SAFIRE had equivalent performance
             compared to FBP at 100% dose.Detectability increased with
             increasing radiation dose (P = 2.7 × 10-59) and contrast
             level (P = 2.2 × 10-86) and was higher in the uniform
             phantom compared to the textured phantoms (P = 6.9 ×
             10-51). Overall, SAFIRE had higher d' compared to FBP (P =
             0.02). The estimated dose reduction potential of SAFIRE was
             found to be 8%, 10%, 27%, and 8% for Texture-A, Texture-B,
             Texture-C and uniform phantoms.In all background types,
             detectability was higher with SAFIRE compared to FBP.
             However, the relative improvement observed from SAFIRE was
             highly dependent on the complexity of the background
             texture. Iterative algorithms such as SAFIRE should be
             assessed in the most realistic context possible.},
   Doi = {10.1118/1.4967478},
   Key = {fds322724}
}

@article{fds322105,
   Author = {Ikejimba, LC and Glick, SJ and Choudhury, KR and Samei, E and Lo,
             JY},
   Title = {Assessing task performance in FFDM, DBT, and synthetic
             mammography using uniform and anthropomorphic physical
             phantoms.},
   Journal = {Medical physics},
   Volume = {43},
   Number = {10},
   Pages = {5593},
   Year = {2016},
   Month = {October},
   url = {http://dx.doi.org/10.1118/1.4962475},
   Abstract = {The purpose of this study is to quantify the differences in
             detectability between full field digital mammography (FFDM),
             digital breast tomosynthesis (DBT), and synthetic
             mammography (SM) for challenging, low contrast signals, in
             the context of both a uniform and an anthropomorphic,
             textured phantom.Images of the phantoms were acquired using
             a Hologic Selenia Dimensions system. Images were taken at
             50%, 100%, and 200% of the dose delivered under automatic
             exposure control (AEC). Low-contrast disks, created using an
             inkjet printer with iodine-doped ink, were inserted into the
             phantom. The disks varied in diameter from 210 to 630 μm,
             and in local contrast from 1.1% to 2.8% in regular
             increments. Human observers located the disks in a 4
             alternative forced choice experiment. Proportion correct
             (PC) was computed as the number of correct localizations out
             of the total number of tries.Overall, scores from FFDM and
             DBT were consistently greater than scores from SM. At an
             exposure corresponding to the AEC setting, mean PC scores
             for the largest disks with the uniform phantom were 0.80 for
             FFDM, 0.83 for DBT, and 0.66 for SM, with the same rank
             ordering at other doses. Scores were similar but lower for
             the nonuniform background. At an exposure twice the AEC
             setting, however, the difference between uniform and
             nonuniform scores was most pronounced for DBT alone.
             Differences between scores for FFDM and SM were
             statistically significant, while those between FFDM and DBT
             were not. Scores were used to compute the minimum contrast
             level needed to reach 62.5% detection rate. The minimum
             contrast for SM was 36%-81% higher compared to FFDM or DBT,
             in either background.This study shows that an
             anthropomorphic phantom and lesions inserts may be used to
             conduct a reader study. Detectability was significantly
             lower for synthetic mammography than for FFDM or DBT, for
             all conditions. Additionally, observer performance was
             consistently lower for the anthropomorphic phantom,
             indicating the greater challenge due to anatomical
             background. Because of this, it may be important to use
             realistic phantoms in observer studies in order to draw
             conclusions that are more clinically relevant.},
   Doi = {10.1118/1.4962475},
   Key = {fds322105}
}

@article{fds322104,
   Author = {Sanders, J and Hurwitz, L and Samei, E},
   Title = {Patient-specific quantification of image quality: An
             automated method for measuring spatial resolution in
             clinical CT images.},
   Journal = {Medical physics},
   Volume = {43},
   Number = {10},
   Pages = {5330},
   Year = {2016},
   Month = {October},
   url = {http://dx.doi.org/10.1118/1.4961984},
   Abstract = {To develop and validate an automated technique for
             evaluating the spatial resolution characteristics of
             clinical computed tomography (CT) images.Twenty one chest
             and abdominopelvic clinical CT datasets were examined in
             this study. An algorithm was developed to extract a CT
             resolution index (RI) analogous to the modulation transfer
             function from clinical CT images by measuring the
             edge-spread function (ESF) across the patient's skin. A
             polygon mesh of the air-skin boundary was created. The faces
             of the mesh were then used to measure the ESF across the
             air-skin interface. The ESF was differentiated to obtain the
             line-spread function (LSF), and the LSF was Fourier
             transformed to obtain the RI. The algorithm's ability to
             detect the radial dependence of the RI was investigated. RIs
             measured with the proposed method were compared with a
             conventional phantom-based method across two reconstruction
             algorithms (FBP and iterative) using the spatial frequency
             at 50% RI, f50, as the metric for comparison. Three
             reconstruction kernels were investigated for each
             reconstruction algorithm. Finally, an observer study was
             conducted to determine if observers could visually perceive
             the differences in the measured blurriness of images
             reconstructed with a given reconstruction method.RI
             measurements performed with the proposed technique exhibited
             the expected dependencies on the image reconstruction. The
             measured f50 values increased with harder kernels for both
             FBP and iterative reconstruction. Furthermore, the proposed
             algorithm was able to detect the radial dependence of the
             RI. Patient-specific measurements of the RI were comparable
             to the phantom-based technique, but the patient data
             exhibited a large spread in the measured f50, indicating
             that some datasets were blurrier than others even when the
             projection data were reconstructed with the same
             reconstruction algorithm and kernel. Results from the
             observer study substantiated this finding.Clinically
             informed, patient-specific spatial resolution can be
             measured from clinical datasets. The method is sufficiently
             sensitive to reflect changes in spatial resolution due to
             different reconstruction parameters. The method can be
             applied to automatically assess the spatial resolution of
             patient images and quantify dependencies that may not be
             captured in phantom data.},
   Doi = {10.1118/1.4961984},
   Key = {fds322104}
}

@article{fds322725,
   Author = {Tian, X and Yin, Z and De Man and B and Samei, E},
   Title = {Estimation of Radiation Dose in CT Based on Projection
             Data.},
   Journal = {Journal of Digital Imaging},
   Volume = {29},
   Number = {5},
   Pages = {615-621},
   Year = {2016},
   Month = {October},
   url = {http://dx.doi.org/10.1007/s10278-016-9869-x},
   Abstract = {Managing and optimizing radiation dose has become a core
             problem for the CT community. As a fundamental step for dose
             optimization, accurate and computationally efficient dose
             estimates are crucial. The purpose of this study was to
             devise a computationally efficient projection-based dose
             metric. The absorbed energy and object mass were
             individually modeled using the projection data. The absorbed
             energy was estimated using the difference between intensity
             of the primary photon and the exit photon. The mass was
             estimated using the volume under the attenuation profile.
             The feasibility of the approach was evaluated across
             phantoms with a broad size range, various kVp settings, and
             two bowtie filters, using a simulation tool, the Computer
             Assisted Tomography SIMulator (CATSIM) software. The
             accuracy of projection-based dose estimation was validated
             against Monte Carlo (MC) simulations. The relationship
             between projection-based dose metric and MC dose estimate
             was evaluated using regression models. The projection-based
             dose metric showed a strong correlation with Monte Carlo
             dose estimates (R (2) > 0.94). The prediction errors for
             the projection-based dose metric were all below 15 %. This
             study demonstrated the feasibility of computationally
             efficient dose estimation requiring only the projection
             data.},
   Doi = {10.1007/s10278-016-9869-x},
   Key = {fds322725}
}

@article{fds322106,
   Author = {Kiarashi, N and Nolte, LW and Lo, JY and Segars, WP and Ghate, SV and Solomon, JB and Samei, E},
   Title = {Impact of breast structure on lesion detection in breast
             tomosynthesis, a simulation study.},
   Journal = {Journal of medical imaging (Bellingham, Wash.)},
   Volume = {3},
   Number = {3},
   Pages = {035504},
   Year = {2016},
   Month = {July},
   url = {http://dx.doi.org/10.1117/1.jmi.3.3.035504},
   Abstract = {This study aims to characterize the effect of background
             tissue density and heterogeneity on the detection of
             irregular masses in breast tomosynthesis, while
             demonstrating the capability of the sophisticated tools that
             can be used in the design, implementation, and performance
             analysis of virtual clinical trials (VCTs). Twenty breast
             phantoms from the extended cardiac-torso (XCAT) family,
             generated based on dedicated breast computed tomography of
             human subjects, were used to extract a total of 2173 volumes
             of interest (VOIs) from simulated tomosynthesis images. Five
             different lesions, modeled after human subject tomosynthesis
             images, were embedded in the breasts and combined with the
             lesion absent condition yielded a total of [Formula: see
             text] VOIs. Effects of background tissue density and
             heterogeneity on the detection of the lesions were studied
             by implementing a composite hypothesis signal detection
             paradigm with location known exactly, lesion known exactly
             or statistically, and background known statistically. Using
             the area under the receiver operating characteristic curve,
             detection performance deteriorated as density was increased,
             yielding findings consistent with clinical studies. A human
             observer study was performed on a subset of the simulated
             tomosynthesis images, confirming the detection performance
             trends with respect to density and serving as a validation
             of the implemented detector. Performance of the implemented
             detector varied substantially across the 20 breasts.
             Furthermore, background tissue density and heterogeneity
             affected the log-likelihood ratio test statistic differently
             under lesion absent and lesion present conditions.
             Therefore, considering background tissue variability in
             tissue models can change the outcomes of a VCT and is hence
             of crucial importance. The XCAT breast phantoms have the
             potential to address this concern by offering realistic
             modeling of background tissue variability based on a wide
             range of human subjects, comprising various breast shapes,
             sizes, and densities.},
   Doi = {10.1117/1.jmi.3.3.035504},
   Key = {fds322106}
}

@article{fds322726,
   Author = {Badano, A and Wang, J and Boynton, P and Le Callet and P and Cheng, W-C and Deroo, D and Flynn, MJ and Matsui, T and Penczek, J and Revie, C and Samei,
             E and Steven, PM and Swiderski, S and Van Hoey and G and Yamaguchi, M and Hasegawa, M and Nagy, BV},
   Title = {Technical Note: Gray tracking in medical color displays-A
             report of Task Group 196.},
   Journal = {Medical physics},
   Volume = {43},
   Number = {7},
   Pages = {4017},
   Year = {2016},
   Month = {July},
   url = {http://dx.doi.org/10.1118/1.4953186},
   Abstract = {The authors discuss measurement methods and instrumentation
             useful for the characterization of the gray tracking
             performance of medical color monitors for diagnostic
             applications. The authors define gray tracking as the
             variability in the chromaticity of the gray levels in a
             color monitor.The authors present data regarding the
             capability of color measurement instruments with respect to
             their abilities to measure a target white point
             corresponding to the CIE Standard Illuminant D65 at
             different luminance values within the grayscale palette of a
             medical display. The authors then discuss evidence of
             significant differences in performance among color
             measurement instruments currently available for medical
             physicists to perform calibrations and image quality checks
             for the consistent representation of color in medical
             displays. In addition, the authors introduce two metrics for
             quantifying grayscale chromaticity consistency of gray
             tracking.The authors' findings show that there is an order
             of magnitude difference in the accuracy of field and
             reference instruments. The gray tracking metrics quantify
             how close the grayscale chromaticity is to the chromaticity
             of the full white point (equal amounts of red, green, and
             blue at maximum level) or to consecutive levels (equal
             values for red, green, and blue), with a lower value
             representing an improved grayscale tracking performance. An
             illustrative example of how to calculate and report the gray
             tracking performance according to the Task Group definitions
             is provided.The authors' proposed methodology for
             characterizing the grayscale degradation in chromaticity for
             color monitors that can be used to establish standards and
             procedures aiding in the quality control testing of color
             displays and color measurement instrumentation.},
   Doi = {10.1118/1.4953186},
   Key = {fds322726}
}

@article{fds322727,
   Author = {Lin, Y and Samei, E},
   Title = {Development and validation of a segmentation-free
             polyenergetic algorithm for dynamic perfusion computed
             tomography.},
   Journal = {Journal of medical imaging (Bellingham, Wash.)},
   Volume = {3},
   Number = {3},
   Pages = {033503},
   Year = {2016},
   Month = {July},
   url = {http://dx.doi.org/10.1117/1.jmi.3.3.033503},
   Abstract = {Dynamic perfusion imaging can provide the morphologic
             details of the scanned organs as well as the dynamic
             information of blood perfusion. However, due to the
             polyenergetic property of the x-ray spectra, beam hardening
             effect results in undesirable artifacts and inaccurate CT
             values. To address this problem, this study proposes a
             segmentation-free polyenergetic dynamic perfusion imaging
             algorithm (pDP) to provide superior perfusion imaging.
             Dynamic perfusion usually is composed of two phases, i.e., a
             precontrast phase and a postcontrast phase. In the
             precontrast phase, the attenuation properties of diverse
             base materials (e.g., in a thorax perfusion exam, base
             materials can include lung, fat, breast, soft tissue, bone,
             and metal implants) can be incorporated to reconstruct
             artifact-free precontrast images. If patient motions are
             negligible or can be corrected by registration, the
             precontrast images can then be employed as a priori
             information to derive linearized iodine projections from the
             postcontrast images. With the linearized iodine projections,
             iodine perfusion maps can be reconstructed directly without
             the influence of various influential factors, such as iodine
             location, patient size, x-ray spectrum, and background
             tissue type. A series of simulations were conducted on a
             dynamic iodine calibration phantom and a dynamic
             anthropomorphic thorax phantom to validate the proposed
             algorithm. The simulations with the dynamic iodine
             calibration phantom showed that the proposed algorithm could
             effectively eliminate the beam hardening effect and enable
             quantitative iodine map reconstruction across various
             influential factors. The error range of the iodine
             concentration factors ([Formula: see text]) was reduced from
             [Formula: see text] for filtered back-projection (FBP) to
             [Formula: see text] for pDP. The quantitative results of the
             simulations with the dynamic anthropomorphic thorax phantom
             indicated that the maximum error of iodine concentrations
             can be reduced from [Formula: see text] for FBP to less than
             [Formula: see text] for pDP, which suggested that the
             proposed algorithm could not only effectively eliminate beam
             hardening artifacts but also significantly reduce the
             influence of the metal artifacts and accurately reconstruct
             the iodine map regardless of the influential factors. A
             segmentation-free polyenergetic dynamic perfusion imaging
             algorithm was proposed and validated via simulations. This
             method can accurately reconstruct artifact-free iodine maps
             for quantitative analyses.},
   Doi = {10.1117/1.jmi.3.3.033503},
   Key = {fds322727}
}

@article{fds322728,
   Author = {Solomon, J and Samei, E},
   Title = {Correlation between human detection accuracy and observer
             model-based image quality metrics in computed
             tomography.},
   Journal = {Journal of medical imaging (Bellingham, Wash.)},
   Volume = {3},
   Number = {3},
   Pages = {035506},
   Year = {2016},
   Month = {July},
   Abstract = {The purpose of this study was to compare computed tomography
             (CT) low-contrast detectability from human readers with
             observer model-based surrogates of image quality. A phantom
             with a range of low-contrast signals (five contrasts, three
             sizes) was imaged on a state-of-the-art CT scanner (Siemens'
             force). Images were reconstructed using filtered back
             projection and advanced modeled iterative reconstruction and
             were assessed by 11 readers using a two alternative forced
             choice method. Concurrently, contrast-to-noise ratio (CNR),
             area-weighted CNR (CNRA), and observer model-based metrics
             were estimated, including nonprewhitening (NPW) matched
             filter, NPW with eye filter (NPWE), NPW with internal noise,
             NPW with an eye filter and internal noise (NPWEi),
             channelized Hotelling observer (CHO), and CHO with internal
             noise (CHOi). The correlation coefficients (Pearson and
             Spearman), linear discriminator error, [Formula: see text],
             and magnitude of confidence intervals, [Formula: see text],
             were used to determine correlation, proper characterization
             of the reconstruction algorithms, and model precision,
             respectively. Pearson (Spearman) correlation was 0.36
             (0.33), 0.83 (0.84), 0.84 (0.86), 0.86 (0.88), 0.86 (0.91),
             0.88 (0.90), 0.85 (0.89), and 0.87 (0.84), [Formula: see
             text] was 0.25, 0.15, 0.2, 0.25, 0.3, 0.25, 0.4, and 0.45,
             and [Formula: see text] was [Formula: see text], [Formula:
             see text], [Formula: see text], [Formula: see text],
             [Formula: see text], [Formula: see text], [Formula: see
             text], and [Formula: see text] for CNR, CNRA, NPW, NPWE,
             NPWi, NPWEi, CHO, and CHOi, respectively.},
   Key = {fds322728}
}

@article{fds323996,
   Author = {Ria, F and Wilson, JM and Guntzer, P and Zanca, F and Samei,
             E},
   Title = {SU-F-I-48: Variability in CT Scanning Over-Range Across
             Clinical Operation.},
   Journal = {Medical physics},
   Volume = {43},
   Number = {6},
   Pages = {3397},
   Publisher = {American Association of Physicists in Medicine: Medical
             Physics},
   Year = {2016},
   Month = {June},
   url = {http://dx.doi.org/10.1118/1.4955876},
   Abstract = {Inconsistency in the scan range for a given protocol can be
             a source of variability in patient dose. The purpose of this
             study was to determine the variability in the over-scan
             length in clinical CT operation for chest and abdominopelvic
             (A&P) protocols.A total of 51 abdomen-pelvis and 121 chest
             CT exams were randomly selected from our clinical database.
             A commercial dose monitoring solution was used to extract
             and database the total exposure area and the geometrical
             information related to automatically-segmented anatomical
             landmarks for each target region. The data were exported
             off-line for the statistical analysis. The over-scan length
             (delta) was calculated as the difference between the real
             scanned length and ideal scanning length based on the
             anatomical landmarks for each target region.The mean delta
             for abdomen-pelvis exams was 12 mm (median 8 mm; min -191
             mm; max 158 mm; standard deviation 71 mm). The average delta
             values at the interfaces with the chest and lower extremity
             regions were 69 mm and -57 mm, respectively. For chest
             exams, the average delta was 91 mm (median 93 mm; min 36 mm;
             max 190 mm; standard deviation 29 mm), and the average delta
             values at interfaces with the neck and abdomen regions were
             26 mm and 65 mm, respectively. The percentage delta mean
             related to the abdomen-pelvis and chest lengths were 3% and
             45%, respectively.Although there is greater over-scan in the
             chest region, there is considerably more variability in the
             over-scan area for abdomen-pelvis exams. Estimation of the
             over-scan length must be included in the effective dose
             estimates, which uses different coefficients for different
             target region (ICRP 102). Furthermore, knowledge of
             over-scan lengths and variability can guide steps to improve
             clinical consistency and operation.},
   Doi = {10.1118/1.4955876},
   Key = {fds323996}
}

@article{fds326626,
   Author = {Ria, F and Wilson, JM and Guntzer, P and Zanca, F and Samei,
             E},
   Title = {Variability in CT Scanning Over-Range Across Clinical
             Operation},
   Journal = {Medical physics},
   Volume = {43},
   Number = {6},
   Pages = {3397-3397},
   Year = {2016},
   Month = {June},
   url = {http://dx.doi.org/10.1118/1.4955876},
   Doi = {10.1118/1.4955876},
   Key = {fds326626}
}

@article{fds322107,
   Author = {Marin, D and Ramirez-Giraldo, JC and Gupta, S and Fu, W and Stinnett,
             SS and Mileto, A and Bellini, D and Patel, B and Samei, E and Nelson,
             RC},
   Title = {Effect of a Noise-Optimized Second-Generation Monoenergetic
             Algorithm on Image Noise and Conspicuity of Hypervascular
             Liver Tumors: An In Vitro and In Vivo Study.},
   Journal = {AJR. American journal of roentgenology},
   Volume = {206},
   Number = {6},
   Pages = {1222-1232},
   Year = {2016},
   Month = {June},
   url = {http://dx.doi.org/10.2214/ajr.15.15512},
   Abstract = {The purpose of this study is to investigate whether the
             reduction in noise using a second-generation monoenergetic
             algorithm can improve the conspicuity of hypervascular liver
             tumors on dual-energy CT (DECT) images of the liver.An
             anthropomorphic liver phantom in three body sizes and
             iodine-containing inserts simulating hypervascular lesions
             was imaged with DECT and single-energy CT at various energy
             levels (80-140 kV). In addition, a retrospective clinical
             study was performed in 31 patients with 66 hypervascular
             liver tumors who underwent DECT during the late hepatic
             arterial phase. Datasets at energy levels ranging from 40 to
             80 keV were reconstructed using first- and second-generation
             monoenergetic algorithms. Noise, tumor-to-liver
             contrast-to-noise ratio (CNR), and CNR with a noise
             constraint (CNRNC) set with a maximum noise increase of 50%
             were calculated and compared among the different
             reconstructed datasets.The maximum CNR for the
             second-generation monoenergetic algorithm, which was
             attained at 40 keV in both phantom and clinical datasets,
             was statistically significantly higher than the maximum CNR
             for the first-generation monoenergetic algorithm (p < 0.001)
             or single-energy CT acquisitions across a wide range of
             kilovoltage values. With the second-generation monoenergetic
             algorithm, the optimal CNRNC occurred at 55 keV,
             corresponding to lower energy levels compared with
             first-generation algorithm (predominantly at 70 keV).
             Patient body size did not substantially affect the selection
             of the optimal energy level to attain maximal CNR and CNRNC
             using the second-generation monoenergetic algorithm.A
             noise-optimized second-generation monoenergetic algorithm
             significantly improves the conspicuity of hypervascular
             liver tumors.},
   Doi = {10.2214/ajr.15.15512},
   Key = {fds322107}
}

@article{fds324794,
   Author = {Solomon, J and Zhang, Y and Marin, D and Samei, E},
   Title = {SU-G-206-13: Validating Dose Split: A Method to Image the
             Same Patient at Multiple Doses with a Single CT
             Acquisition.},
   Journal = {Medical physics},
   Volume = {43},
   Number = {6},
   Pages = {3642},
   Year = {2016},
   Month = {June},
   url = {http://dx.doi.org/10.1118/1.4956954},
   Abstract = {Dose optimization studies in CT have a need for images
             acquired at multiple dose levels. This presents ethical and
             logistical challenges for performing such research with
             human subjects. As a result, most studies rely on phantom
             data. The purpose of this study was to perform a
             physics-based validation of a method to obtain images of the
             same patient at multiple dose levels using a single CT
             acquisition on a dual-source CT system.The Dose Split (DS)
             method relies on acquiring raw projection data
             simultaneously from two separate sources/detectors (denoted
             Tube A and Tube B) on a dual-source system. By distributing
             the dose unevenly between Tube A and Tube B (at the same
             kVp), it is possible to reconstruct images corresponding to
             any dose in the range of min(A,B) to A+B. CT data of the ACR
             phantom were acquired on a dual-source system (SOMATOM
             Flash, Siemens Healthcare) with a traditional single-source
             (SS) technique at 6 dose levels (25, 50, 75, 100, 150, and
             200 mAs). Corresponding data using the DS technique were
             acquired and compared with the SS data in terms of noise
             magnitude (pixel STD), contrast, contrast-to-noise ratio,
             noise power spectrum (average spatial frequency), modulation
             transfer function (50% frequency) and detectability index
             (for a non-prewhitening matched filter observer).Between the
             DS and SS techniques, the differences (SS-DS) in noise
             magnitude, contrast, and CNR were on average (across doses)
             1.2 HU (4.1%), 0.7 HU (11%), and 0.02 (6.9%), respectively.
             The differences in NPS average frequency, MTF 50% frequency,
             and detectability index were 0.01 cycles/mm (2.5%), 0.03
             cycles/mm (7.5%), and -.03 (-6.8%), respectively.The dose
             split method can be used to acquire images of the same
             patient equivalent to many dose levels in a single
             acquisition. Differences in noise, CNR, NPS, MTF, and
             detectability were all negligible.},
   Doi = {10.1118/1.4956954},
   Key = {fds324794}
}

@article{fds324795,
   Author = {Wilson, JM and Samei, E},
   Title = {SU-F-R-11: Designing Quality and Safety Informatics Through
             Implementation of a CT Radiation Dose Monitoring
             Program.},
   Journal = {Medical physics},
   Volume = {43},
   Number = {6},
   Pages = {3375},
   Year = {2016},
   Month = {June},
   url = {http://dx.doi.org/10.1118/1.4955783},
   Abstract = {Recent legislative and accreditation requirements have
             driven rapid development and implementation of CT radiation
             dose monitoring solutions. Institutions must determine how
             to improve quality, safety, and consistency of their
             clinical performance. The purpose of this work was to design
             a strategy and meaningful characterization of results from
             an in-house, clinically-deployed dose monitoring solution.A
             dose monitoring platform was designed by our imaging physics
             group that focused on extracting protocol parameters, dose
             metrics, and patient demographics and size. Compared to most
             commercial solutions, which focus on individual exam alerts
             and global thresholds, the program sought to characterize
             overall consistency and targeted thresholds based on eight
             analytic interrogations. Those were based on explicit
             questions related to protocol application, national
             benchmarks, protocol and size-specific dose targets,
             operational consistency, outliers, temporal trends,
             intra-system variability, and consistent use of electronic
             protocols. Using historical data since the start of 2013,
             95% and 99% intervals were used to establish yellow and
             amber parameterized dose alert thresholds, respectively, as
             a function of protocol, scanner, and size.Quarterly reports
             have been generated for three hospitals for 3 quarters of
             2015 totaling 27880, 28502, 30631 exams, respectively. Four
             adult and two pediatric protocols were higher than external
             institutional benchmarks. Four protocol dose levels were
             being inconsistently applied as a function of patient size.
             For the three hospitals, the minimum and maximum amber
             outlier percentages were [1.53%,2.28%], [0.76%,1.8%],
             [0.94%,1.17%], respectively. Compared with the electronic
             protocols, 10 protocols were found to be used with some
             inconsistency.Dose monitoring can satisfy requirements with
             global alert thresholds and patient dose records, but the
             real value is in optimizing patient-specific protocols,
             balancing image quality trade-offs that dose-reduction
             strategies promise, and improving the performance and
             consistency of a clinical operation. Data plots that capture
             patient demographics and scanner performance demonstrate
             that value.},
   Doi = {10.1118/1.4955783},
   Key = {fds324795}
}

@article{fds324796,
   Author = {Carver, D and Willis, C and Stauduhar, P and Nishino, T and Wells, J and Samei, E},
   Title = {TU-FG-209-07: Medical Physics 1.0 Versus Medical Physics
             2.0: A Case Study.},
   Journal = {Medical physics},
   Volume = {43},
   Number = {6},
   Pages = {3762},
   Year = {2016},
   Month = {June},
   url = {http://dx.doi.org/10.1118/1.4957577},
   Abstract = {To illustrate how performance analytics can identify
             performance decrement in digital radiography
             systems.Subsequent to a radiologist's image quality
             complaint, four different advanced methods contributed to
             root cause analysis. Our system was a GE Revolution XQi
             digital radiography unit. Initially, we reviewed weekly GE
             Quality Assurance Procedures (QAP) results in a database
             dating from 2001. Next, we evaluated objective image quality
             metrics of individual PA Chest radiographs acquired. These
             images were anonymized, securely transferred, and analyzed
             by the Duke University Clinical Imaging Physics Group with
             software previously described1 and validated2 . Third, we
             compared the exposure-dependent SNR2 (NEQ) of the unit with
             previously established confidence limits3 . Finally, we
             explored our service database to reveal events that might
             affect detector performance.QAP reported a decrease in CNR
             reflected in a significant increase in lung noise(Ln),
             mediastinum noise(Mn), and subdiaphragm-lung contrast(Slc)
             with a significant decrease in lung grey level(Lgl) after
             detector replacement. Most change occurred during week 1,
             before the QAP indicated one-half the ultimate decrease in
             CNR. After detector recalibration, QAP CNR improved, but was
             not restored to previous levels. Lgl and Slc were no longer
             significantly different from before, however Ln and Mn
             remained significantly different. Exposure-dependent SNR2
             show the detector to be operating within limits in October
             2006 but subsequently became miscalibrated sometime before
             acquisition of the 2011-2014 data. Service records revealed
             catastrophic failure of the Image Detection Controller that
             contained the 2007 calibration. Traditional metrics did not
             indicate that the system was performing outside of normal
             limits.Performance analytics are powerful tools whose proper
             application could allow early intervention in degraded
             system performance. The image-quality metrics appear to be
             highly sensitive to system performance and are reported with
             every acquisition rather than at arbitrary intervals.
             Confidence intervals may require customization for
             individual systems or detectors.},
   Doi = {10.1118/1.4957577},
   Key = {fds324796}
}

@article{fds324797,
   Author = {Robins, M and Solomon, J and Samei, E},
   Title = {TH-CD-207B-04: Is TTF a True Representation of the Sharpness
             Property of a Non-Linear CT System?},
   Journal = {Medical physics},
   Volume = {43},
   Number = {6},
   Pages = {3889},
   Year = {2016},
   Month = {June},
   url = {http://dx.doi.org/10.1118/1.4958210},
   Abstract = {To investigate if the task-transfer-function (TTF)
             accurately models the transfer properties of a CT system for
             lung nodule imaging.An anthropomorphic lung phantom was
             imaged using a standard chest protocol on a clinical CT
             scanner with and without 24 physically inserted synthetic
             lesions (nominal diameter: 8 - 10 mm). Images were
             reconstructed using FBP and iterative algorithm (SAFIRE,
             Siemens Healthcare). 3D TTF was measured using an
             established technique. Corresponding idealized virtual
             lesions were blurred with the TTF and superimposed onto
             lesion-less phantom images. Images of the physically and
             virtually inserted lesions were compared in terms of
             rendition of spatial features (blurriness of the edges),
             lesion morphology, and lesion volume. Feature rendition was
             measured in terms root-mean-square (RMS) of the frequency
             power of the native and TTF-transferred lesion edge
             transition. Morphology was assessed with the Regional
             Hausdorff Distance (RHD) using custom written code (MATLAB
             v2015b). Volumes were measured using a clinical segmentation
             tool (iNtution, TeraRecon).The RMS was less than 0.02 and
             0.05 for FBP and IR respectively. Using the nonlinear mixed
             effect (nlme) package (R, www.r-project.org), the difference
             in RHD between virtual and physical lesions was 5% on
             average. There was less than 1 ± 5% (R2 > 0.97) and 3 ± 4%
             (R2 > 0.97) difference between the volumes of the physical
             lesions and the corresponding virtual lesions for FBP and IR
             respectively. Additionally, was closer concordance for
             images reconstructed with FBP than iterative
             reconstruction.The TTF was found to accurately model the
             transfer properties of the CT imaging system on lung lesions
             for both FBP and iterative reconstruction algorithms. TTF
             was found to offer slightly better lesion renditions when
             modeling images reconstructed with FBP versus iterative
             reconstruction. This methodology will be used in future
             investigation of more complex imaging tasks such as low
             contrast detectability of known lesions.},
   Doi = {10.1118/1.4958210},
   Key = {fds324797}
}

@article{fds324798,
   Author = {Sanders, J and Ding, A and Samei, E},
   Title = {TH-CD-207B-02: An Automated Technique to Measure Spatial
             Resolution in Clinical CT Images: Application to Patient
             Data.},
   Journal = {Medical physics},
   Volume = {43},
   Number = {6},
   Pages = {3889},
   Year = {2016},
   Month = {June},
   url = {http://dx.doi.org/10.1118/1.4958208},
   Abstract = {To evaluate an automated technique for measuring spatial
             resolution across a database of clinical CT exams.A fully
             automated algorithm was developed to extract a CT resolution
             index (RI) analogous to the modulation transfer function
             from clinical CT images by measuring the edge-spread
             function (ESF) across the patient's skin and converting the
             results into scalar values, frequency at 50% RI, f50. The
             program was previously validated against observer data. This
             algorithm was applied to a database of CT images from our
             hospital that were reconstructed with different
             reconstruction algorithms (filtered back-projection and
             iterative) and reconstruction kernels (soft and hard). The
             results were analyzed in terms of mean and variability
             within reconstruction methods and kernel aspects of the
             protocols.The automated algorithm successfully measured the
             RI index from all of the clinical datasets examined. The
             measured f50 values increased with harder kernels for both
             FBP and iterative reconstruction. The mean f50 was 0.30 ±
             0.02 mm-1 and 0.42 ± 0.03 mm-1 for images reconstructed
             with soft and hard kernels, respectively, using filtered
             back-projection. The corresponding values for iterative
             reconstructions were 0.34 ± 0.02 mm-1 and 0.39 ± 0.03
             mm-1, respectively. Overall, there was more variability in
             the f50 measurements made on datasets reconstructed with a
             hard kernel. The differences were statistically significant
             (p<0.05).Clinically-informed, patient-specific spatial
             resolution can be measured from clinical datasets. The
             method is sufficiently sensitive to reflect changes in
             spatial resolution due to different reconstruction
             parameters. The method can be applied to automatically
             assess the spatial resolution of patient images and quantify
             dependencies that may not be captured in phantom
             data.},
   Doi = {10.1118/1.4958208},
   Key = {fds324798}
}

@article{fds329029,
   Author = {Sanders, J and Abadi, E and Meng, B and Samei, E},
   Title = {SU-F-I-45: An Automated Technique to Measure Image Contrast
             in Clinical CT Images.},
   Journal = {Medical physics},
   Volume = {43},
   Number = {6},
   Pages = {3397},
   Year = {2016},
   Month = {June},
   url = {http://dx.doi.org/10.1118/1.4955873},
   Abstract = {To develop and validate an automated technique for measuring
             image contrast in chest computed tomography (CT) exams.An
             automated computer algorithm was developed to measure the
             distribution of Hounsfield units (HUs) inside four major
             organs: the lungs, liver, aorta, and bones. These organs
             were first segmented or identified using computer vision and
             image processing techniques. Regions of interest (ROIs) were
             automatically placed inside the lungs, liver, and aorta and
             histograms of the HUs inside the ROIs were constructed. The
             mean and standard deviation of each histogram were computed
             for each CT dataset. Comparison of the mean and standard
             deviation of the HUs in the different organs provides
             different contrast values. The ROI for the bones is simply
             the segmentation mask of the bones. Since the histogram for
             bones does not follow a Gaussian distribution, the 25th and
             75th percentile were computed instead of the mean. The
             sensitivity and accuracy of the algorithm was investigated
             by comparing the automated measurements with manual
             measurements. Fifteen contrast enhanced and fifteen
             non-contrast enhanced chest CT clinical datasets were
             examined in the validation procedure.The algorithm
             successfully measured the histograms of the four organs in
             both contrast and non-contrast enhanced chest CT exams. The
             automated measurements were in agreement with manual
             measurements. The algorithm has sufficient sensitivity as
             indicated by the near unity slope of the automated versus
             manual measurement plots. Furthermore, the algorithm has
             sufficient accuracy as indicated by the high coefficient of
             determination, R2, values ranging from 0.879 to
             0.998.Patient-specific image contrast can be measured from
             clinical datasets. The algorithm can be run on both contrast
             enhanced and non-enhanced clinical datasets. The method can
             be applied to automatically assess the contrast
             characteristics of clinical chest CT images and quantify
             dependencies that may not be captured in phantom
             data.},
   Doi = {10.1118/1.4955873},
   Key = {fds329029}
}

@article{fds324799,
   Author = {Winslow, J and Zhang, Y and Samei, E},
   Title = {TU-H-207A-05: Automated Early Identification of An Excessive
             Air-In-Oil X-Ray Tube Artifact That Mimics Acute Cerebral
             Infarct.},
   Journal = {Medical physics},
   Volume = {43},
   Number = {6},
   Pages = {3772},
   Year = {2016},
   Month = {June},
   url = {http://dx.doi.org/10.1118/1.4957641},
   Abstract = {There is an infrequent but serious CT artifact that occurs
             when there is too much air in the cooling oil of an x-ray
             tube. This artifact manifests as patchy hypodensities and
             mimics acute cerebral infarct. Routine quality control
             testing is unlikely to detect this artifact before it is
             observed in patient images. The purpose of this project was
             to develop an automated, quantitative method that increased
             the likelihood of identifying and preventing such
             artifacts.Using QC phantom images with a known air-in-oil
             artifact, a 1D radial representation of the 2D noise power
             spectrum(NPS) was calculated and compared against that for
             artifact-free images. The QC program software used at our
             institution to analyze daily phantom images was modified to
             include measuring the average frequency of NPS within the
             water section of daily phantom scans. The threshold values
             developed for each CT system were incorporated into our
             daily QC program and email notification system.The NPS for
             the known air-in-oil artifact images included a large low
             frequency peak compared with artifact-free images; the
             average NPS frequency for these images were 0.197 and 0.319
             (1/mm), respectively. The average NPS frequency values
             (mean+/- standard deviation) for the GE CT750, GE VCT, GE
             Lightspeed Xtra, and Siemens SOMATOM Definition Flash
             scanners were 0.322+/- 0.0058, 0.324+/-0.0024,
             0.320+/-0.0020, and 0.303+/-0.0039 (1/mm), respectively.
             Threshold values were chosen to be the average plus or minus
             twice the standard deviation. Automated QC successfully
             identified an air-in-oil artifact in the Lightspeed Xtra
             before any detrimental clinical effect occurred; the average
             NPS frequency value that triggered service was 0.307, which
             is six standard deviations smaller than average.Clinically
             serious problems associated with the air-in-oil artifact can
             be detected earlier and mitigated/avoided by incorporating
             the average frequency of NPS measurements of daily phantom
             images into an automated QC program.},
   Doi = {10.1118/1.4957641},
   Key = {fds324799}
}

@article{fds324800,
   Author = {Sanders, J and Tian, X and Segars, P and Boone, J and Samei,
             E},
   Title = {TU-H-207A-09: An Automated Technique for Estimating
             Patient-Specific Regional Imparted Energy and Dose From TCM
             CT Exams Across 13 Protocols.},
   Journal = {Medical physics},
   Volume = {43},
   Number = {6},
   Pages = {3773},
   Year = {2016},
   Month = {June},
   url = {http://dx.doi.org/10.1118/1.4957645},
   Abstract = {To develop an automated technique for estimating
             patient-specific regional imparted energy and dose from tube
             current modulated (TCM) computed tomography (CT) exams
             across a diverse set of head and body protocols.A library of
             58 adult computational anthropomorphic extended
             cardiac-torso (XCAT) phantoms were used to model a patient
             population. A validated Monte Carlo program was used to
             simulate TCM CT exams on the entire library of phantoms for
             three head and 10 body protocols. The net imparted energy to
             the phantoms, normalized by dose length product (DLP), and
             the net tissue mass in each of the scan regions were
             computed. A knowledgebase containing relationships between
             normalized imparted energy and scanned mass was established.
             An automated computer algorithm was written to estimate the
             scanned mass from actual clinical CT exams. The scanned mass
             estimate, DLP of the exam, and knowledgebase were used to
             estimate the imparted energy to the patient. The algorithm
             was tested on 20 chest and 20 abdominopelvic TCM CT
             exams.The normalized imparted energy increased with
             increasing kV for all protocols. However, the normalized
             imparted energy was relatively unaffected by the strength of
             the TCM. The average imparted energy was 681 ± 376 mJ for
             abdominopelvic exams and 274 ± 141 mJ for chest exams.
             Overall, the method was successful in providing
             patientspecific estimates of imparted energy for 98% of the
             cases tested.Imparted energy normalized by DLP increased
             with increasing tube potential. However, the strength of the
             TCM did not have a significant effect on the net amount of
             energy deposited to tissue. The automated program can be
             implemented into the clinical workflow to provide estimates
             of regional imparted energy and dose across a diverse set of
             clinical protocols.},
   Doi = {10.1118/1.4957645},
   Key = {fds324800}
}

@article{fds324801,
   Author = {Samei, E},
   Title = {TU-D-207A-02: Quantitative Assessment of CT Systems with
             Iterative Image Reconstruction Algorithms.},
   Journal = {Medical physics},
   Volume = {43},
   Number = {6},
   Pages = {3747-3748},
   Year = {2016},
   Month = {June},
   url = {http://dx.doi.org/10.1118/1.4957495},
   Abstract = {In recent several years, motivated by the need to reduce
             radiation doses in CT exams, all of the major CT
             manufacturers have commercialized different iterative image
             reconstruction techniques and these innovative techniques
             were used in clinical routines with increasing popularity.
             However, due to the intrinsic nonlinearity of these new
             techniques, the well accepted quantitative image quality
             assessment metrics such as spatial resolution and contrast
             to noise ratio are not sufficient to provide the needed
             quantitative metrics for assessing image quality and for
             guiding the CT scan protocol optimization. This symposium
             aims at providing a thorough update to AAPM community on
             what we have understood in the past for linear CT imaging
             system, what are the new challenges and opportunities
             offered by the nonlinear iterative image reconstruction, and
             what would be the future directions in quantitative image
             quality assessment that the AAPM community can work together
             to address the challenges and to adapt the nonlinear image
             reconstruction methods to routine clinical practice to
             improve patient care. Three invited speakers will lead the
             discussions in this symposium. Dr. Ke Li from the University
             of Wisconsin-Madison will be presenting the new challenges
             introduced in model-based iterative reconstruction (MBIR)
             method with a focus on how the nonlinear nature of the MBIR
             reconstruction poses challenges in quantitative image
             quality metrics such as spatial resolution, noise power
             spectrum, and the limitations of CNR in protocol
             optimization which eventually leads to the need of
             task-based detectability index as the metric. Dr. Shuai Leng
             from Mayo Clinic will then present how the CNR metric is
             insufficient for nonlinear reconstruction algorithms, and
             how task based model observers can be used to more
             accurately quantify image quality, and to optimize imaging
             system and scanning protocols for nonlinear iterative image
             reconstruction algorithms based on specific imaging task.
             Practical considerations regarding the application of task
             based image quality metrics will also be discussed. Dr.
             Ehsan Samei from Duke University will start the symposium by
             summarizing a to-be-released AAPM Task Group report (TG 233:
             Performance Evaluation of Computed Tomography Systems). He
             will cover what has been understood and accepted for linear
             CT imaging system, what are the new challenges in CT image
             quality assessment introduced by the nonlinear iterative
             reconstruction (IR) techniques, and summarize both
             taskneutral and task-based metrologies developed in TG 233
             to partially address these challenges, and foresee
             additional challenges in the future.1. Understand the
             challenges in quantitative image quality assessment
             introduced by nonlinear iterative reconstruction techniques
             2. Understand the challenges and methods in noise
             performance assessment for nonlinear iterative
             reconstruction techniques 3. Understand the challenges and
             methods in in spatial resolution assessment for nonlinear
             iterative reconstruction techniques 4. Understand the
             challenges and methods in in task-based observer performance
             assessment for nonlinear iterative reconstruction techniques
             Funding support received from NIH and DOD; Funding support
             received from GE Healthcare; Funding support received from
             Siemens AX; Patent royalties received from GE Healthcare; S.
             Leng, R01 EB071095; U01 EB017185; E. Samei, Research grant,
             Siemens; Research grant, GE; K. Li, Funding from NIH, DOD
             and AAPM.},
   Doi = {10.1118/1.4957495},
   Key = {fds324801}
}

@article{fds324802,
   Author = {Richards, T and Mann, S and Samei, E},
   Title = {TU-FG-209-06: Quantitative Evaluation of the Temporal
             Performance of Clinical Fluoroscopic Imaging Systems: The
             Temporal Modulation Transfer Function (TMTF).},
   Journal = {Medical physics},
   Volume = {43},
   Number = {6},
   Pages = {3761-3762},
   Year = {2016},
   Month = {June},
   url = {http://dx.doi.org/10.1118/1.4957576},
   Abstract = {Measure the temporal modulation transfer function (TMTF) of
             clinical fluoroscopic flat panel imaging systems in order to
             accurately quantify their performance for temporally
             sensitive clinical tasks.Copper blades (0.76 mm thick, 6 cm
             radius) with precision-machined edges were manufactured and
             mounted on a voltage regulated DC motor apparatus. Images
             were acquired with the blade apparatus positioned at the
             center of the detector matrix and set in motion at a
             constant rotational velocity (0.66 Hz), thereby creating a
             rotating radio-opaque edge in both space and time. The
             spatio-temporal edge response function was analyzed using a
             single frame from the acquired image sequence. Image
             processing included semi-automatic detection of the center
             of rotation, rebinning the pixels into subsampled polar
             coordinates, and deconvolving the TMTF from the previously
             measured spatial MTF. The analysis returned the presampled
             TMTF. This method was applied to multiple fluoroscopic
             imaging systems.Initial experiments measured the TMTF of a
             typical fluoroscopy unit (Philips Allura Xper FD20) using
             cine acquisition (60.7 kVp, 6 fps, 42.6 ms pulse-width). For
             this system and protocol, the measured TMTF closely matched
             an idealized sinc function corresponding to the Fourier
             transform of the measured rectangular x-ray pulse-width.
             Within the frequency range of 0 - 47 Hz, the measured TMTF
             and ideal sinc function were compared at 1.46 Hz intervals.
             The differences measured varied within [-0.0164, 0.0324]
             with a root-mean-square (rms) difference of 0.0201. These
             particular results suggest that very little degradation in
             temporal performance is attributable to the imaging
             hardware, but rather the measured performance is dominated
             by the acquisition protocol parameters, namely pulse-width
             and frames-per-second.This method provides a clinically
             tractable and accurate measurement of the TMTF. Ongoing
             experiments are investigating the impact of different
             fluoroscopy systems, image processing, and protocol choice
             on the measured TMTF.},
   Doi = {10.1118/1.4957576},
   Key = {fds324802}
}

@article{fds324803,
   Author = {Mann, S and Nelson, J and Samei, E},
   Title = {TU-H-206-01: An Automated Approach for Identifying Geometric
             Distortions in Gamma Cameras.},
   Journal = {Medical physics},
   Volume = {43},
   Number = {6},
   Pages = {3773-3774},
   Year = {2016},
   Month = {June},
   url = {http://dx.doi.org/10.1118/1.4957646},
   Abstract = {To develop a clinically-deployable, automated process for
             detecting artifacts in routine nuclear medicine (NM) quality
             assurance (QA) bar phantom images.An artifact detection
             algorithm was created to analyze bar phantom images as part
             of an ongoing QA program. A low noise, high resolution
             reference image was acquired from an x-ray of the bar
             phantom with a Philips Digital Diagnost system utilizing
             image stitching. NM bar images, acquired for 5 million
             counts over a 512×512 matrix, were registered to the
             template image by maximizing mutual information (MI). The MI
             index was used as an initial test for artifacts; low values
             indicate an overall presence of distortions regardless of
             their spatial location. Images with low MI scores were
             further analyzed for bar linearity, periodicity, alignment,
             and compression to locate differences with respect to the
             template. Findings from each test were spatially correlated
             and locations failing multiple tests were flagged as
             potential artifacts requiring additional visual analysis.
             The algorithm was initially deployed for GE Discovery 670
             and Infinia Hawkeye gamma cameras.The algorithm successfully
             identified clinically relevant artifacts from both systems
             previously unnoticed by technologists performing the QA.
             Average MI indices for artifact-free images are 0.55. Images
             with MI indices < 0.50 have shown 100% sensitivity and
             specificity for artifact detection when compared with a
             thorough visual analysis. Correlation of geometric tests
             confirms the ability to spatially locate the most likely
             image regions containing an artifact regardless of initial
             phantom orientation.The algorithm shows the potential to
             detect gamma camera artifacts that may be missed by routine
             technologist inspections. Detection and subsequent
             correction of artifacts ensures maximum image quality and
             may help to identify failing hardware before it impacts
             clinical workflow. Going forward, the algorithm is being
             deployed to monitor data from all gamma cameras within our
             health system.},
   Doi = {10.1118/1.4957646},
   Key = {fds324803}
}

@article{fds324804,
   Author = {Samei, E},
   Title = {WE-B-BRC-03: Risk in the Context of Medical
             Imaging.},
   Journal = {Medical physics},
   Volume = {43},
   Number = {6},
   Pages = {3807},
   Year = {2016},
   Month = {June},
   url = {http://dx.doi.org/10.1118/1.4957800},
   Abstract = {Prospective quality management techniques, long used by
             engineering and industry, have become a growing aspect of
             efforts to improve quality management and safety in
             healthcare. These techniques are of particular interest to
             medical physics as scope and complexity of clinical practice
             continue to grow, thus making the prescriptive methods we
             have used harder to apply and potentially less effective for
             our interconnected and highly complex healthcare enterprise,
             especially in imaging and radiation oncology. An essential
             part of most prospective methods is the need to assess the
             various risks associated with problems, failures, errors,
             and design flaws in our systems. We therefore begin with an
             overview of risk assessment methodologies used in healthcare
             and industry and discuss their strengths and weaknesses. The
             rationale for use of process mapping, failure modes and
             effects analysis (FMEA) and fault tree analysis (FTA) by
             TG-100 will be described, as well as suggestions for the way
             forward. This is followed by discussion of radiation
             oncology specific risk assessment strategies and issues,
             including the TG-100 effort to evaluate IMRT and other ways
             to think about risk in the context of radiotherapy. Incident
             learning systems, local as well as the ASTRO/AAPM ROILS
             system, can also be useful in the risk assessment process.
             Finally, risk in the context of medical imaging will be
             discussed. Radiation (and other) safety considerations, as
             well as lack of quality and certainty all contribute to the
             potential risks associated with suboptimal imaging. The goal
             of this session is to summarize a wide variety of risk
             analysis methods and issues to give the medical physicist
             access to tools which can better define risks (and their
             importance) which we work to mitigate with both prescriptive
             and prospective risk-based quality management methods.1.
             Description of risk assessment methodologies used in
             healthcare and industry 2. Discussion of radiation
             oncology-specific risk assessment strategies and issues 3.
             Evaluation of risk in the context of medical imaging and
             image quality E. Samei: Research grants from Siemens and
             GE.},
   Doi = {10.1118/1.4957800},
   Key = {fds324804}
}

@article{fds324805,
   Author = {Abadi, E and Sanders, J and Agasthya, G and Segars, P and Samei,
             E},
   Title = {TH-AB-207A-01: Contrast-Enhanced CT: Correlation of
             Radiation Dose and Biological Effect.},
   Journal = {Medical physics},
   Volume = {43},
   Number = {6},
   Pages = {3859},
   Year = {2016},
   Month = {June},
   url = {http://dx.doi.org/10.1118/1.4958077},
   Abstract = {The potential risk from CT is generally characterized in
             terms of radiation dose. The presence of iodinated-contrast
             medium increases radiation dose. However, it is unclear how
             much of this increase is biologically relevant. The purpose
             of this study was to establish the contribution of dose
             increase from iodine to biological effect.Radiation organ
             dose was estimated in 58 human (XCAT) phantoms "undergoing"
             chest CT examination (120 kVp, 9 mGy CTDI) on a simulated CT
             system (Definition Flash, Siemens) with and without
             iodinated-contrast agent (62.5 mL of iodine per subject).
             The dose without and with the presence of iodine was
             compared to the increase in foci per cell (a surrogate of
             DNA damage) measured before and after similar CT exams
             without and with contrast agent (Piechowiak et al. 2015).
             The data were analyzed to ascertain how the enhancement in
             biological effect in contrast-enhanced CTs correlated with
             the increase in dose due to the presence of iodine.The
             presence of iodinated-contrast in CT increased the organ
             doses by 2% to 50% on average. Typical values were heart
             (50%±7%), kidney (19%±7%), and liver (2%±3%). The
             corresponding increase in the average foci per cell was
             107%±19%, indicating biological effect of iodine was
             greater than what would be anticipated from the
             iodine-initiated increase in radiation dose alone.Mean foci
             per cell and organ dose both increase in the presence of
             contrast agent. The former, however, is at least twice as
             large as the latter, indicating that iodine contributes to
             an increase in the probability of DNA damage not only as a
             consequence of increased x-ray energy deposition but also
             from other mechanisms. Hence iodine radiation dose, while
             relevant to be included in estimating the risk associated
             with contrast-enhanced CT, still can underestimate the
             biological effects.},
   Doi = {10.1118/1.4958077},
   Key = {fds324805}
}

@article{fds322108,
   Author = {Nelson, JS and Wells, JR and Baker, JA and Samei,
             E},
   Title = {How does c-view image quality compare with conventional 2D
             FFDM?},
   Journal = {Medical physics},
   Volume = {43},
   Number = {5},
   Pages = {2538},
   Year = {2016},
   Month = {May},
   url = {http://dx.doi.org/10.1118/1.4947293},
   Abstract = {The FDA approved the use of digital breast tomosynthesis
             (DBT) in 2011 as an adjunct to 2D full field digital
             mammography (FFDM) with the constraint that all DBT
             acquisitions must be paired with a 2D image to assure
             adequate interpretative information is provided. Recently
             manufacturers have developed methods to provide a
             synthesized 2D image generated from the DBT data with the
             hope of sparing patients the radiation exposure from the
             FFDM acquisition. While this much needed alternative
             effectively reduces the total radiation burden, differences
             in image quality must also be considered. The goal of this
             study was to compare the intrinsic image quality of
             synthesized 2D c-view and 2D FFDM images in terms of
             resolution, contrast, and noise.Two phantoms were utilized
             in this study: the American College of Radiology mammography
             accreditation phantom (ACR phantom) and a novel 3D printed
             anthropomorphic breast phantom. Both phantoms were imaged
             using a Hologic Selenia Dimensions 3D system. Analysis of
             the ACR phantom includes both visual inspection and
             objective automated analysis using in-house software.
             Analysis of the 3D anthropomorphic phantom includes visual
             assessment of resolution and Fourier analysis of the
             noise.Using ACR-defined scoring criteria for the ACR
             phantom, the FFDM images scored statistically higher than
             c-view according to both the average observer and automated
             scores. In addition, between 50% and 70% of c-view images
             failed to meet the nominal minimum ACR accreditation
             requirements-primarily due to fiber breaks. Software
             analysis demonstrated that c-view provided enhanced
             visualization of medium and large microcalcification
             objects; however, the benefits diminished for smaller high
             contrast objects and all low contrast objects. Visual
             analysis of the anthropomorphic phantom showed a measureable
             loss of resolution in the c-view image (11 lp/mm FFDM, 5
             lp/mm c-view) and loss in detection of small
             microcalcification objects. Spectral analysis of the
             anthropomorphic phantom showed higher total noise magnitude
             in the FFDM image compared with c-view. Whereas the FFDM
             image contained approximately white noise texture, the
             c-view image exhibited marked noise reduction at
             midfrequency and high frequency with far less noise
             suppression at low frequencies resulting in a mottled noise
             appearance.Their analysis demonstrates many instances where
             the c-view image quality differs from FFDM. Compared to
             FFDM, c-view offers a better depiction of objects of certain
             size and contrast, but provides poorer overall resolution
             and noise properties. Based on these findings, the
             utilization of c-view images in the clinical setting
             requires careful consideration, especially if considering
             the discontinuation of FFDM imaging. Not explicitly explored
             in this study is how the combination of DBT + c-view
             performs relative to DBT + FFDM or FFDM alone.},
   Doi = {10.1118/1.4947293},
   Key = {fds322108}
}

@article{fds322729,
   Author = {Tian, X and Segars, WP and Dixon, RL and Samei, E},
   Title = {Convolution-based estimation of organ dose in tube current
             modulated CT.},
   Journal = {Physics in Medicine and Biology},
   Volume = {61},
   Number = {10},
   Pages = {3935-3954},
   Year = {2016},
   Month = {May},
   url = {http://dx.doi.org/10.1088/0031-9155/61/10/3935},
   Abstract = {Estimating organ dose for clinical patients requires
             accurate modeling of the patient anatomy and the dose field
             of the CT exam. The modeling of patient anatomy can be
             achieved using a library of representative computational
             phantoms (Samei et al 2014 Pediatr. Radiol. 44 460-7). The
             modeling of the dose field can be challenging for CT exams
             performed with a tube current modulation (TCM) technique.
             The purpose of this work was to effectively model the dose
             field for TCM exams using a convolution-based method. A
             framework was further proposed for prospective and
             retrospective organ dose estimation in clinical practice.
             The study included 60 adult patients (age range: 18-70
             years, weight range: 60-180 kg). Patient-specific
             computational phantoms were generated based on patient CT
             image datasets. A previously validated Monte Carlo
             simulation program was used to model a clinical CT scanner
             (SOMATOM Definition Flash, Siemens Healthcare, Forchheim,
             Germany). A practical strategy was developed to achieve
             real-time organ dose estimation for a given clinical
             patient. CTDIvol-normalized organ dose coefficients
             ([Formula: see text]) under constant tube current were
             estimated and modeled as a function of patient size. Each
             clinical patient in the library was optimally matched to
             another computational phantom to obtain a representation of
             organ location/distribution. The patient organ distribution
             was convolved with a dose distribution profile to generate
             [Formula: see text] values that quantified the regional dose
             field for each organ. The organ dose was estimated by
             multiplying [Formula: see text] with the organ dose
             coefficients ([Formula: see text]). To validate the accuracy
             of this dose estimation technique, the organ dose of the
             original clinical patient was estimated using Monte Carlo
             program with TCM profiles explicitly modeled. The
             discrepancy between the estimated organ dose and dose
             simulated using TCM Monte Carlo program was quantified. We
             further compared the convolution-based organ dose estimation
             method with two other strategies with different approaches
             of quantifying the irradiation field. The proposed
             convolution-based estimation method showed good accuracy
             with the organ dose simulated using the TCM Monte Carlo
             simulation. The average percentage error (normalized by
             CTDIvol) was generally within 10% across all organs and
             modulation profiles, except for organs located in the pelvic
             and shoulder regions. This study developed an improved
             method that accurately quantifies the irradiation field
             under TCM scans. The results suggested that organ dose could
             be estimated in real-time both prospectively (with the
             localizer information only) and retrospectively (with
             acquired CT data).},
   Doi = {10.1088/0031-9155/61/10/3935},
   Key = {fds322729}
}

@article{fds323997,
   Author = {Sturgeon, GM and Kiarashi, N and Lo, JY and Samei, E and Segars,
             WP},
   Title = {Finite-element modeling of compression and gravity on a
             population of breast phantoms for multimodality imaging
             simulation.},
   Journal = {Medical physics},
   Volume = {43},
   Number = {5},
   Pages = {2207},
   Year = {2016},
   Month = {May},
   url = {http://dx.doi.org/10.1118/1.4945275},
   Abstract = {The authors are developing a series of computational breast
             phantoms based on breast CT data for imaging research. In
             this work, the authors develop a program that will allow a
             user to alter the phantoms to simulate the effect of gravity
             and compression of the breast (craniocaudal or mediolateral
             oblique) making the phantoms applicable to multimodality
             imaging.This application utilizes a template finite-element
             (FE) breast model that can be applied to their presegmented
             voxelized breast phantoms. The FE model is automatically fit
             to the geometry of a given breast phantom, and the material
             properties of each element are set based on the segmented
             voxels contained within the element. The loading and
             boundary conditions, which include gravity, are then
             assigned based on a user-defined position and compression.
             The effect of applying these loads to the breast is computed
             using a multistage contact analysis in FEBio, a freely
             available and well-validated FE software package
             specifically designed for biomedical applications. The
             resulting deformation of the breast is then applied to a
             boundary mesh representation of the phantom that can be used
             for simulating medical images. An efficient script performs
             the above actions seamlessly. The user only needs to specify
             which voxelized breast phantom to use, the compressed
             thickness, and orientation of the breast.The authors
             utilized their FE application to simulate compressed states
             of the breast indicative of mammography and tomosynthesis.
             Gravity and compression were simulated on example phantoms
             and used to generate mammograms in the craniocaudal or
             mediolateral oblique views. The simulated mammograms show a
             high degree of realism illustrating the utility of the FE
             method in simulating imaging data of repositioned and
             compressed breasts.The breast phantoms and the compression
             software can become a useful resource to the breast imaging
             research community. These phantoms can then be used to
             evaluate and compare imaging modalities that involve
             different positioning and compression of the
             breast.},
   Doi = {10.1118/1.4945275},
   Key = {fds323997}
}

@article{fds299992,
   Author = {Solomon, J and Mileto, A and Nelson, RC and Roy Choudhury and K and Samei,
             E},
   Title = {Quantitative Features of Liver Lesions, Lung Nodules, and
             Renal Stones at Multi-Detector Row CT Examinations:
             Dependency on Radiation Dose and Reconstruction
             Algorithm.},
   Journal = {Radiology},
   Volume = {279},
   Number = {1},
   Pages = {185-194},
   Year = {2016},
   Month = {April},
   ISSN = {0033-8419},
   url = {http://dx.doi.org/10.1148/radiol.2015150892},
   Abstract = {To determine if radiation dose and reconstruction algorithm
             affect the computer-based extraction and analysis of
             quantitative imaging features in lung nodules, liver
             lesions, and renal stones at multi-detector row computed
             tomography (CT).Retrospective analysis of data from a
             prospective, multicenter, HIPAA-compliant, institutional
             review board-approved clinical trial was performed by
             extracting 23 quantitative imaging features (size, shape,
             attenuation, edge sharpness, pixel value distribution, and
             texture) of lesions on multi-detector row CT images of 20
             adult patients (14 men, six women; mean age, 63 years;
             range, 38-72 years) referred for known or suspected focal
             liver lesions, lung nodules, or kidney stones. Data were
             acquired between September 2011 and April 2012. All
             multi-detector row CT scans were performed at two different
             radiation dose levels; images were reconstructed with
             filtered back projection, adaptive statistical iterative
             reconstruction, and model-based iterative reconstruction
             (MBIR) algorithms. A linear mixed-effects model was used to
             assess the effect of radiation dose and reconstruction
             algorithm on extracted features.Among the 23 imaging
             features assessed, radiation dose had a significant effect
             on five, three, and four of the features for liver lesions,
             lung nodules, and renal stones, respectively (P < .002 for
             all comparisons). Adaptive statistical iterative
             reconstruction had a significant effect on three, one, and
             one of the features for liver lesions, lung nodules, and
             renal stones, respectively (P < .002 for all comparisons).
             MBIR reconstruction had a significant effect on nine, 11,
             and 15 of the features for liver lesions, lung nodules, and
             renal stones, respectively (P < .002 for all comparisons).
             Of note, the measured size of lung nodules and renal stones
             with MBIR was significantly different than those for the
             other two algorithms (P < .002 for all comparisons).
             Although lesion texture was significantly affected by the
             reconstruction algorithm used (average of 3.33 features
             affected by MBIR throughout lesion types; P < .002, for all
             comparisons), no significant effect of the radiation dose
             setting was observed for all but one of the texture features
             (P = .002-.998).Radiation dose settings and reconstruction
             algorithms affect the extraction and analysis of
             quantitative imaging features in lesions at multi-detector
             row CT.},
   Doi = {10.1148/radiol.2015150892},
   Key = {fds299992}
}

@article{fds322109,
   Author = {Ikejimba, L and Lo, JY and Chen, Y and Oberhofer, N and Kiarashi, N and Samei, E},
   Title = {A quantitative metrology for performance characterization of
             five breast tomosynthesis systems based on an
             anthropomorphic phantom.},
   Journal = {Medical physics},
   Volume = {43},
   Number = {4},
   Pages = {1627},
   Year = {2016},
   Month = {April},
   url = {http://dx.doi.org/10.1118/1.4943373},
   Abstract = {In medical imaging systems, proper rendition of anatomy is
             essential in discerning normal tissue from disease.
             Currently, digital breast tomosynthesis (DBT) systems are
             evaluated using subjective evaluation of lesion visibility
             in uniform phantoms. This study involved the development of
             a new methodology to objectively measure the rendition of a
             3D breast model by an anthropomorphic breast phantom, and
             its implementation on five clinical DBT systems of different
             makes and models.A 3D, patient-based breast phantom was
             fabricated based on XCAT breast models. This phantom was
             imaged on representative breast tomosynthesis systems. The
             ability of tomosynthesis systems to accurately reproduce the
             3D structure of the breast was assessed by computational
             analysis of the resultant images in terms of three groups of
             indices: contrast index (CI), reflective of local difference
             between adipose and glandular material; adipose variability
             index (AVI), reflective of contributions of noise and
             artifacts within uniform adipose regions; and contrast
             detectability, which describes contrast against local
             background variability and is described by contrast
             variability index (CVI), coefficient of variation (COV),
             contrast to adipose variability index (CAVI), and contrast
             to noise ratio index (CNRI). The indices were obtained by
             comparing the image data to the gold standard 3D
             distribution of breast tissue in the model. Corresponding
             indices were measured within variable region of interest
             (ROI) sizes ranging from 10 to 37 mm. The characterization
             was performed on five tomosynthesis systems: Fuji Aspire
             Crystal, GE Essential, Hologic Dimension, IMS Giotto, and
             Siemens Inspiration, all evaluated at a fixed dose of 1.5
             mGy average glandular dose, anonymized in random order from
             A to E.Results are provided as a function of ROI size. The
             systems ranked orders in terms of CI with values of 7.4%,
             7.0%, 6.9%, 6.4%, and 5.2% for systems A-E, respectively.
             This system ranking was identical for CNRI. Both CI and CNRI
             were constant over ROI size. The ranking was similar for
             CVI. The COV also changed little with ROI size and was
             similar across systems. For 10 mm ROIs, the average system
             COV was 0.7, which reduced to 0.5 with 37 mm ROIs. Two
             systems (A and B) exhibited highest AVI values when measured
             in 10 mm ROIs. This, however, was ROI-size-dependent with
             the three other systems (C-E) yielding higher AVI values
             when measured with 37 mm ROIs. Two systems (B and E) showed
             inferior CAVI compared to others.The quality of rendition
             tracked with differences in image appearance across systems.
             The findings illustrate that the anthropomorphic phantom can
             be used as a basis to extract quantitative values of image
             attributes in DBT.},
   Doi = {10.1118/1.4943373},
   Key = {fds322109}
}

@article{fds324806,
   Author = {Sahbaee, P and Segars, PP and Marin, D and Nelson, R and Samei,
             E},
   Title = {Determination of contrast media administration to achieve a
             targeted contrast enhancement in computed
             tomography.},
   Journal = {Journal of medical imaging (Bellingham, Wash.)},
   Volume = {3},
   Number = {1},
   Pages = {013501},
   Year = {2016},
   Month = {January},
   url = {http://dx.doi.org/10.1117/1.jmi.3.1.013501},
   Abstract = {Contrast enhancement is a key component of computed
             tomography (CT) imaging and offers opportunities for
             optimization. The design and optimization of techniques,
             however, require orchestration with the scan parameters and,
             further, a methodology to relate contrast enhancement and
             injection function. We used such a methodology to develop a
             method, the analytical inverse method, to predict the
             required injection function to achieve a desired contrast
             enhancement in a given organ by incorporation of a
             physiologically based compartmental model. The method was
             evaluated across 32 different target contrast enhancement
             functions for aorta, kidney, stomach, small intestine, and
             liver. The results exhibited that the analytical inverse
             method offers accurate performance with error in the range
             of 10% deviation between the predicted and desired organ
             enhancement curves. However, this method is incapable of
             predicting the injection function based on the liver
             enhancement. The findings of this study can be useful in
             optimizing contrast medium injection function as well as
             scan timing to provide more consistency in the way
             contrast-enhanced CT examinations are performed. To our
             knowledge, this work is one of the first attempts to predict
             the contrast material injection function for a desired organ
             enhancement curve.},
   Doi = {10.1117/1.jmi.3.1.013501},
   Key = {fds324806}
}

@article{fds322110,
   Author = {Sikaria, D and Musinsky, S and Sturgeon, GM and Solomon, J and Diao, A and Gehm, ME and Samei, E and Glick, SJ and Lo, JY},
   Title = {Second generation anthropomorphic physical phantom for
             mammography and DBT: Incorporating voxelized 3D printing and
             inkjet printing of iodinated lesion inserts},
   Journal = {Proceedings of SPIE},
   Volume = {9783},
   Year = {2016},
   Month = {January},
   ISBN = {9781510600188},
   url = {http://dx.doi.org/10.1117/12.2217667},
   Abstract = {© 2016 SPIE. Physical phantoms are needed for the
             evaluation and optimization of new digital breast
             tomosynthesis (DBT) systems. Previously, we developed an
             anthropomorphic phantom based on human subject breast CT
             data and fabricated using commercial 3D printing. We now
             present three key advancements: voxelized 3D printing,
             photopolymer material doping, and 2D inkjet printing of
             lesion inserts. First, we bypassed the printer's control
             software in order to print in voxelized form instead of
             conventional STL surfaces, thus improving resolution and
             allowing dithering to mix the two photopolymer materials
             into arbitrary proportions. We demonstrated ability to print
             details as small as 150μm, and dithering to combine
             VeroWhitePlus and TangoPlus in 10% increments. Second, to
             address the limited attenuation difference among commercial
             photopolymers, we evaluated a beta sample from Stratasys
             with increased TiO 2 doping concentration up to 2.5%, which
             corresponded to 98% breast density. By spanning 36% to 98%
             breast density, this doubles our previous contrast. Third,
             using inkjet printers modified to print with iopamidol, we
             created 2D lesion patterns on paper that can be sandwiched
             into the phantom. Inkjet printing has advantages of being
             inexpensive and easy, and more contrast can be delivered
             through overprinting. Printing resolution was maintained at
             210 μm horizontally and 330 μm vertically even after 10
             overprints. Contrast increased linearly with overprinting at
             0.7% per overprint. Together, these three new features
             provide the basis for creating a new anthropomorphic
             physical breast phantom with improved resolution and
             contrast, as well as the ability to insert 2D lesions for
             task-based assessment of performance.},
   Doi = {10.1117/12.2217667},
   Key = {fds322110}
}

@article{fds322111,
   Author = {Lakshmanan, MN and Morris, RE and Greenberg, JA and Samei, E and Kapadia, AJ},
   Title = {Coded aperture coherent scatter imaging for breast cancer
             detection: A Monte Carlo evaluation},
   Journal = {Proceedings of SPIE},
   Volume = {9783},
   Year = {2016},
   Month = {January},
   ISBN = {9781510600188},
   url = {http://dx.doi.org/10.1117/12.2216482},
   Abstract = {© 2016 SPIE. It is known that conventional x-ray imaging
             provides a maximum contrast between cancerous and healthy
             fibroglandular breast tissues of 3% based on their linear
             x-ray attenuation coefficients at 17.5 keV, whereas coherent
             scatter signal provides a maximum contrast of 19% based on
             their differential coherent scatter cross sections.
             Therefore in order to exploit this potential contrast, we
             seek to evaluate the performance of a coded- aperture
             coherent scatter imaging system for breast cancer detection
             and investigate its accuracy using Monte Carlo simulations.
             In the simulations we modeled our experimental system, which
             consists of a raster-scanned pencil beam of x-rays, a
             bismuth-tin coded aperture mask comprised of a repeating
             slit pattern with 2-mm periodicity, and a linear-array of
             128 detector pixels with 6.5-keV energy resolution. The
             breast tissue that was scanned comprised a 3-cm sample taken
             from a patient-based XCAT breast phantom containing a
             tomosynthesis- based realistic simulated lesion. The
             differential coherent scatter cross section was
             reconstructed at each pixel in the image using an iterative
             reconstruction algorithm. Each pixel in the reconstructed
             image was then classified as being either air or the type of
             breast tissue with which its normalized reconstructed
             differential coherent scatter cross section had the highest
             correlation coefficient. Comparison of the final tissue
             classification results with the ground truth image showed
             that the coded aperture imaging technique has a cancerous
             pixel detection sensitivity (correct identification of
             cancerous pixels), specificity (correctly ruling out healthy
             pixels as not being cancer) and accuracy of 92.4%, 91.9% and
             92.0%, respectively. Our Monte Carlo evaluation of our
             experimental coded aperture coherent scatter imaging system
             shows that it is able to exploit the greater contrast
             available from coherently scattered x-rays to increase the
             accuracy of detecting cancerous regions within the
             breast.},
   Doi = {10.1117/12.2216482},
   Key = {fds322111}
}

@article{fds322112,
   Author = {Ikejimba, L and Glick, SJ and Samei, E and Lo, JY},
   Title = {Comparison of model and human observer performance in FFDM,
             DBT, and synthetic mammography},
   Journal = {Proceedings of SPIE},
   Volume = {9783},
   Year = {2016},
   Month = {January},
   ISBN = {9781510600188},
   url = {http://dx.doi.org/10.1117/12.2216858},
   Abstract = {© 2016 SPIE. Reader studies are important in assessing
             breast imaging systems. The purpose of this work was to
             assess task-based performance of full field digital
             mammography (FFDM), digital breast tomosynthesis (DBT), and
             synthetic mammography (SM) using different phantom types,
             and to determine an accurate observer model for human
             readers. Images were acquired on a Hologic Selenia
             Dimensions system with a uniform and anthropomorphic
             phantom. A contrast detail insert of small, low-contrast
             disks was created using an inkjet printer with iodine-doped
             ink and inserted in the phantoms. The disks varied in
             diameter from 210 to 630 μm, and in contrast from 1.1%
             contrast to 2.2% in regular increments. Human and model
             observers performed a 4-alternative forced choice
             experiment. The models were a non-prewhitening matched
             filter with eye model (NPWE) and a channelized Hotelling
             observer with either Gabor channels (Gabor-CHO) or
             Laguerre-Gauss channels (LG-CHO). With the given phantoms,
             reader scores were higher in FFDM and DBT than SM. The
             structure in the phantom background had a bigger impact on
             outcome for DBT than for FFDM or SM. All three model
             observers showed good correlation with humans in the uniform
             background, with ρ between 0.89 and 0.93. However, in the
             structured background, only the CHOs had high correlation,
             with ρ=0.92 for Gabor-CHO, 0.90 for LG-CHO, and 0.77 for
             NPWE. Because results of any analysis can depend on the
             phantom structure, conclusions of modality performance may
             need to be taken in the context of an appropriate model
             observer and a realistic phantom.},
   Doi = {10.1117/12.2216858},
   Key = {fds322112}
}

@article{fds322730,
   Author = {Solomon, J and Ba, A and Diao, A and Lo, J and Bier, E and Bochud, F and Gehm,
             M and Samei, E},
   Title = {Design, fabrication, and implementation of voxel-based 3D
             printed textured phantoms for task-based image quality
             assessment in CT},
   Journal = {Proceedings of SPIE},
   Volume = {9783},
   Year = {2016},
   Month = {January},
   ISBN = {9781510600188},
   url = {http://dx.doi.org/10.1117/12.2217463},
   Abstract = {© 2016 SPIE. In x-ray computed tomography (CT), task-based
             image quality studies are typically performed using uniform
             background phantoms with low-contrast signals. Such studies
             may have limited clinical relevancy for modern non-linear CT
             systems due to possible influence of background texture on
             image quality. The purpose of this study was to design and
             implement anatomically informed textured phantoms for
             task-based assessment of low-contrast detection. Liver
             volumes were segmented from 23 abdominal CT cases. The
             volumes were characterized in terms of texture features from
             gray-level co-occurrence and run-length matrices. Using a 3D
             clustered lumpy background (CLB) model, a fitting technique
             based on a genetic optimization algorithm was used to find
             the CLB parameters that were most reflective of the liver
             textures, accounting for CT system factors of spatial
             blurring and noise. With the modeled background texture as a
             guide, a cylinder phantom (165 mm in diameter and 30 mm
             height) was designed, containing 20 low-contrast spherical
             signals (6 mm in diameter at targeted contrast levels of
             ∼3.2, 5.2, 7.2, 10, and 14 HU, 4 repeats per signal). The
             phantom was voxelized and input into a commercial
             multi-material 3D printer (Object Connex 350), with custom
             software for voxel-based printing. Using principles of
             digital half-toning and dithering, the 3D printer was
             programmed to distribute two base materials (VeroWhite and
             TangoPlus, nominal voxel size of 42x84x30 microns) to
             achieve the targeted spatial distribution of x-ray
             attenuation properties. The phantom was used for task-based
             image quality assessment of a clinically available iterative
             reconstruction algorithm (Sinogram Affirmed Iterative
             Reconstruction, SAFIRE) using a channelized Hotelling
             observer paradigm. Images of the textured phantom and a
             corresponding uniform phantom were acquired at six dose
             levels and observer model performance was estimated for each
             condition (5 contrasts x 6 doses x 2 reconstructions x 2
             backgrounds = 120 total conditions). Based on the observer
             model results, the dose reduction potential of SAFIRE was
             computed and compared between the uniform and textured
             phantom. The dose reduction potential of SAFIRE was found to
             be 23% based on the uniform phantom and 17% based on the
             textured phantom. This discrepancy demonstrates the need to
             consider background texture when assessing non-linear
             reconstruction algorithms.},
   Doi = {10.1117/12.2217463},
   Key = {fds322730}
}

@article{fds322731,
   Author = {Sahbaee, P and Abadi, E and Sanders, J and Becchetti, M and Zhang, Y and Agasthya, G and Segars, P and Samei, E},
   Title = {A technique for multi-dimensional optimization of radiation
             dose, contrast dose, and image quality in CT
             imaging},
   Journal = {Proceedings of SPIE},
   Volume = {9783},
   Year = {2016},
   Month = {January},
   ISBN = {9781510600188},
   url = {http://dx.doi.org/10.1117/12.2216516},
   Abstract = {© 2016 SPIE. The purpose of this study was to substantiate
             the interdependency of image quality, radiation dose, and
             contrast material dose in CT towards the patient-specific
             optimization of the imaging protocols. The study deployed
             two phantom platforms. First, a variable sized phantom
             containing an iodinated insert was imaged on a
             representative CT scanner at multiple CTDI values. The
             contrast and noise were measured from the reconstructed
             images for each phantom diameter. Linearly related to
             iodine-concentration, contrast to noise ratio (CNR), was
             calculated for different iodine-concentration levels.
             Second, the analysis was extended to a recently developed
             suit of 58 virtual human models (5D-XCAT) with added
             contrast dynamics. Emulating a contrast-enhanced abdominal
             image procedure and targeting a peak-enhancement in aorta,
             each XCAT phantom was "imaged" using a CT simulation
             platform. 3D surfaces for each patient/size established the
             relationship between iodine-concentration, dose, and CNR.
             The Sensitivity of Ratio (SR), defined as ratio of change in
             iodine-concentration versus dose to yield a constant change
             in CNR was calculated and compared at high and low radiation
             dose for both phantom platforms. The results show that
             sensitivity of CNR to iodine concentration is larger at high
             radiation dose (up to 73%). The SR results were highly
             affected by radiation dose metric; CTDI or organ dose.
             Furthermore, results showed that the presence of contrast
             material could have a profound impact on optimization
             results (up to 45%).},
   Doi = {10.1117/12.2216516},
   Key = {fds322731}
}

@article{fds322732,
   Author = {Fu, W and Tian, X and Sahbaee, P and Zhang, Y and Segars, WP and Samei,
             E},
   Title = {Organ dose conversion coefficients for tube current
             modulated CT protocols for an adult population},
   Journal = {Proceedings of SPIE},
   Volume = {9783},
   Year = {2016},
   Month = {January},
   ISBN = {9781510600188},
   url = {http://dx.doi.org/10.1117/12.2217271},
   Abstract = {© 2016 SPIE. In computed tomography (CT), patient-specific
             organ dose can be estimated using pre-calculated organ dose
             conversion coefficients (organ dose normalized by CTDI vol ,
             h factor) database, taking into account patient size and
             scan coverage. The conversion coefficients have been
             previously estimated for routine body protocol classes,
             grouped by scan coverage, across an adult population for
             fixed tube current modulated CT. The coefficients, however,
             do not include the widely utilized tube current (mA)
             modulation scheme, which significantly impacts organ dose.
             This study aims to extend the h factors and the
             corresponding dose length product (DLP) to create effective
             dose conversion coefficients (k factor) database
             incorporating various tube current modulation strengths.
             Fifty-eight extended cardiac-torso (XCAT) phantoms were
             included in this study representing population anatomy
             variation in clinical practice. Four mA profiles,
             representing weak to strong mA dependency on body
             attenuation, were generated for each phantom and protocol
             class. A validated Monte Carlo program was used to simulate
             the organ dose. The organ dose and effective dose was
             further normalized by CTDI vol and DLP to derive the h
             factors and k factors, respectively. The h factors and k
             factors were summarized in an exponential regression model
             as a function of body size. Such a population-based
             mathematical model can provide a comprehensive organ dose
             estimation given body size and CTDI vol . The model was
             integrated into an iPhone app XCATdose version 2, enhancing
             the 1st version based upon fixed tube current modulation.
             With the organ dose calculator, physicists, physicians, and
             patients can conveniently estimate organ
             dose.},
   Doi = {10.1117/12.2217271},
   Key = {fds322732}
}

@article{fds322733,
   Author = {Sanders, JW and Tian, X and Segars, WP and Boone, J and Samei,
             E},
   Title = {An automated technique for estimating patient-specific
             regional imparted energy and dose in TCM CT
             exams},
   Journal = {Proceedings of SPIE},
   Volume = {9783},
   Year = {2016},
   Month = {January},
   ISBN = {9781510600188},
   url = {http://dx.doi.org/10.1117/12.2216413},
   Abstract = {© 2016 SPIE. Currently computed tomography (CT) dosimetry
             relies on CT dose index (CTDI) and size specific dose
             estimates (SSDE). Organ dose is a better metric of radiation
             burden. However, organ dose estimation requires precise
             knowledge of organ locations. Regional imparted energy and
             dose can also be used to quantify radiation burden.
             Estimating the imparted energy from CT exams is beneficial
             in that it does not require precise estimates of the organ
             size or location. This work investigated an automated
             technique for retrospectively estimating the imparted energy
             from chest and abdominopelvic tube current modulated (TCM)
             CT exams. Monte Carlo simulations of chest and
             abdominopelvic TCM CT examinations across various tube
             potentials and TCM strengths were performed on 58 adult
             computational extended cardiac-torso (XCAT) phantoms to
             develop relationships between scanned mass and imparted
             energy normalized by dose length product (DLP). An automated
             algorithm for calculating the scanned patient volume was
             further developed using an open source mesh generation
             toolbox. The scanned patient volume was then used to
             estimate the scanned mass accounting for diverse density
             within the scan region. The scanned mass and DLP from the
             exam were used to estimate the imparted energy to the
             patient using the knowledgebase developed from the Monte
             Carlo simulations. Patientspecific imparted energy estimates
             were made from 20 chest and 20 abdominopelvic clinical CT
             exams. The average imparted energy was 274 ± 141 mJ and 681
             ± 376 mJ for the chest and abdominopelvic exams,
             respectively. This method can be used to estimate the
             regional imparted energy and/or regional dose in chest and
             abdominopelvic TCM CT exams across clinical
             operations.},
   Doi = {10.1117/12.2216413},
   Key = {fds322733}
}

@article{fds322734,
   Author = {Fu, W and Tian, X and Sturgeon, G and Agasthya, G and Segars, WP and Goodsitt, MM and Kazerooni, EA and Samei, E},
   Title = {Estimation of breast dose saving potential using a breast
             positioning technique for organ-based tube current modulated
             CT},
   Journal = {Proceedings of SPIE},
   Volume = {9783},
   Year = {2016},
   Month = {January},
   ISBN = {9781510600188},
   url = {http://dx.doi.org/10.1117/12.2217239},
   Abstract = {© 2016 SPIE. In thoracic CT, organ-based tube current
             modulation (OTCM) reduces breast dose by lowering the tube
             current in the 120° anterior dose reduction zone of
             patients. However, in practice the breasts usually expand to
             an angle larger than the dose reduction zone. This work aims
             to simulate a breast positioning technique (BPT) to
             constrain the breast tissue to within the dose reduction
             zone for OTCM and to evaluate the corresponding potential
             reduction in breast dose. Thirteen female anthropomorphic
             computational phantoms were studied (age range: 27-65 y.o.,
             weight range: 52-105.8 kg). Each phantom was modeled in the
             supine position with and without application of the BPT.
             Attenuation-based tube current (ATCM, reference mA) was
             generated by a ray-tracing program, taking into account the
             patient attenuation change in the longitudinal and angular
             plane (CAREDose4D, Siemens Healthcare). OTCM was generated
             by reducing the mA to 20% between ± 60° anterior of the
             patient and increasing the mA in the remaining projections
             correspondingly (X-CARE, Siemens Healthcare) to maintain the
             mean tube current. Breast tissue dose was estimated using a
             validated Monte Carlo program for a commercial scanner
             (SOMATOM Definition Flash, Siemens Healthcare). Compared to
             standard tube current modulation, breast dose was
             significantly reduced using OTCM by 19.8±4.7%. With the
             BPT, breast dose was reduced by an additional 20.4±6.5% to
             37.1±6.9%, using the same CTDIvol. BPT was more effective
             for phantoms simulating women with larger breasts with the
             average breast dose reduction of 30.2%, 39.2%, and 49.2%
             from OTCMBP to ATCM, using the same CTDIvol for phantoms
             with 0.5, 1.5, and 2.5 kg breasts, respectively. This study
             shows that a specially designed BPT improves the
             effectiveness of OTCM.},
   Doi = {10.1117/12.2217239},
   Key = {fds322734}
}

@article{fds322735,
   Author = {Sahbaee, P and Robins, M and Solomon, J and Samei,
             E},
   Title = {Development of a Hausdorff distance based 3D quantification
             technique to evaluate the CT imaging system impact on
             depiction of lesion morphology},
   Journal = {Proceedings of SPIE},
   Volume = {9783},
   Year = {2016},
   Month = {January},
   ISBN = {9781510600188},
   url = {http://dx.doi.org/10.1117/12.2216503},
   Abstract = {© 2016 SPIE. The purpose of this study was to develop a 3D
             quantification technique to assess the impact of imaging
             system on depiction of lesion morphology. Regional Hausdorff
             Distance (RHD) was computed from two 3D volumes: virtual
             mesh models of synthetic nodules or "virtual nodules" and CT
             images of physical nodules or "physical nodules". The method
             can be described in following steps. First, the synthetic
             nodule was inserted into anthropomorphic Kyoto thorax
             phantom and scanned in a Siemens scanner (Flash). Then,
             nodule was segmented from the image. Second, in order to
             match the orientation of the nodule, the digital models of
             the "virtual" and "physical" nodules were both geometrically
             translated to the origin. Then, the "physical" was gradually
             rotated at incremental 10 degrees. Third, the Hausdorff
             Distance was calculated from each pair of "virtual" and
             "physical" nodules. The minimum HD value represented the
             most matching pair. Finally, the 3D RHD map and the
             distribution of RHD were computed for the matched pair. The
             technique was scalarized using the FWHM of the RHD
             distribution. The analysis was conducted for various shapes
             (spherical, lobular, elliptical, and speculated) of nodules.
             The calculated FWHM values of RHD distribution for the 8-mm
             spherical, lobular, elliptical, and speculated "virtual" and
             "physical" nodules were 0.23, 0.42, 0.33, and 0.49,
             respectively.},
   Doi = {10.1117/12.2216503},
   Key = {fds322735}
}

@article{fds322736,
   Author = {Robins, M and Solomon, J and Sahbaee, P and Samei,
             E},
   Title = {Development and comparison of projection and image space 3D
             nodule insertion techniques},
   Journal = {Proceedings of SPIE},
   Volume = {9783},
   Year = {2016},
   Month = {January},
   ISBN = {9781510600188},
   url = {http://dx.doi.org/10.1117/12.2216930},
   Abstract = {© 2016 SPIE. This study aimed to develop and compare two
             methods of inserting computerized virtual lesions into CT
             datasets. 24 physical (synthetic) nodules of three sizes and
             four morphologies were inserted into an anthropomorphic
             chest phantom (LUNGMAN, KYOTO KAGAKU). The phantom was
             scanned (Somatom Definition Flash, Siemens Healthcare) with
             and without nodules present, and images were reconstructed
             with filtered back projection and iterative reconstruction
             (SAFIRE) at 0.6 mm slice thickness using a standard thoracic
             CT protocol at multiple dose settings. Virtual 3D CAD models
             based on the physical nodules were virtually inserted
             (accounting for the system MTF) into the nodule-free CT data
             using two techniques. These techniques include
             projection-based and image-based insertion. Nodule volumes
             were estimated using a commercial segmentation tool
             (iNtuition, TeraRecon, Inc.). Differences were tested using
             paired t-tests and R2 goodness of fit between the virtually
             and physically inserted nodules. Both insertion techniques
             resulted in nodule volumes very similar to the real nodules
             ( < 3% difference) and in most cases the differences were
             not statistically significant. Also, R2 values were all <
             0.97 for both insertion techniques. These data imply that
             these techniques can confidently be used as a means of
             inserting virtual nodules in CT datasets. These techniques
             can be instrumental in building hybrid CT datasets composed
             of patient images with virtually inserted
             nodules.},
   Doi = {10.1117/12.2216930},
   Key = {fds322736}
}

@article{fds322737,
   Author = {Becchetti, MF and Solomon, JB and Segars, WP and Samei,
             E},
   Title = {Synthesized interstitial lung texture for use in
             anthropomorphic computational phantoms},
   Journal = {Proceedings of SPIE},
   Volume = {9783},
   Year = {2016},
   Month = {January},
   ISBN = {9781510600188},
   url = {http://dx.doi.org/10.1117/12.2217135},
   Abstract = {© 2016 SPIE. A realistic model of the anatomical texture
             from the pulmonary interstitium was developed with the goal
             of extending the capability of anthropomorphic computational
             phantoms (e.g., XCAT, Duke University), allowing for more
             accurate image quality assessment. Contrast-enhanced, high
             dose, thorax images for a healthy patient from a clinical CT
             system (Discovery CT750HD, GE healthcare) with thin (0.625
             mm) slices and filtered back- projection (FBP) were used to
             inform the model. The interstitium which gives rise to the
             texture was defined using 24 volumes of interest (VOIs).
             These VOIs were selected manually to avoid vasculature,
             bronchi, and bronchioles. A small scale Hessian-based line
             filter was applied to minimize the amount of partial-volumed
             supernumerary vessels and bronchioles within the VOIs. The
             texture in the VOIs was characterized using 8 Haralick and
             13 gray-level run length features. A clustered lumpy
             background (CLB) model with added noise and blurring to
             match CT system was optimized to resemble the texture in the
             VOIs using a genetic algorithm with the Mahalanobis distance
             as a similarity metric between the texture features. The
             most similar CLB model was then used to generate the
             interstitial texture to fill the lung. The optimization
             improved the similarity by 45%. This will substantially
             enhance the capabilities of anthropomorphic computational
             phantoms, allowing for more realistic CT
             simulations.},
   Doi = {10.1117/12.2217135},
   Key = {fds322737}
}

@article{fds269173,
   Author = {Brinkley, MF and Ramirez-Giraldo, JC and Samei, E and Frush, DJ and Choudhury, KR and Wilson, JM and Christianson, OI and Frush,
             DP},
   Title = {Effects of automatic tube potential selection on radiation
             dose index, image quality, and lesion detectability in
             pediatric abdominopelvic CT and CTA: a phantom
             study.},
   Journal = {European Radiology},
   Volume = {26},
   Number = {1},
   Pages = {157-166},
   Year = {2016},
   Month = {January},
   ISSN = {0938-7994},
   url = {http://dx.doi.org/10.1007/s00330-015-3817-x},
   Abstract = {To assess the effect of automatic tube potential selection
             (ATPS) on radiation dose, image quality, and lesion
             detectability in paediatric abdominopelvic CT and CT
             angiography (CTA).A paediatric modular phantom with contrast
             inserts was examined with routine pitch (1.4) and high pitch
             (3.0) using a standard abdominopelvic protocol with fixed
             120 kVp, and ATPS with variable kVp in non-contrast,
             contrast-enhanced, and CTA mode. The volume CT dose index
             (CTDIvol), contrast-to-noise ratio (CNR) and lesion
             detectability index (d') were compared between the standard
             protocol and ATPS examinations.CTDIvol was reduced in all
             routine pitch ATPS examinations, with dose reductions of
             27-52 % in CTA mode (P < 0.0001), 15-33 % in
             contrast-enhanced mode (P = 0.0003) and 8-14 % in
             non-contrast mode (P = 0.03). Iodine and soft tissue insert
             CNR and d' were improved or maintained in all ATPS
             examinations. kVp and dose were reduced in 25 % of high
             pitch ATPS examinations and in none of the full phantom
             examinations obtained after a single full phantom
             localizer.ATPS reduces radiation dose while maintaining
             image quality and lesion detectability in routine pitch
             paediatric abdominopelvic CT and CTA, but technical factors
             such as pitch and imaging range must be considered to
             optimize ATPS benefits.ATPS automatically individualizes CT
             scan technique for each patient. ATPS lowers radiation dose
             in routine pitch pediatric abdominopelvic CT and CTA. There
             is no loss of image quality or lesion detectability with
             ATPS. Pitch and scan range impact the effectiveness of ATPS
             dose reduction.},
   Doi = {10.1007/s00330-015-3817-x},
   Key = {fds269173}
}

@article{fds322113,
   Author = {Erickson, DW and Wells, JR and Sturgeon, GM and Samei, E and Dobbins,
             JT and Segars, WP and Lo, JY},
   Title = {Population of 224 realistic human subject-based
             computational breast phantoms.},
   Journal = {Medical physics},
   Volume = {43},
   Number = {1},
   Pages = {23},
   Year = {2016},
   Month = {January},
   url = {http://dx.doi.org/10.1118/1.4937597},
   Abstract = {To create a database of highly realistic and anatomically
             variable 3D virtual breast phantoms based on dedicated
             breast computed tomography (bCT) data.A tissue
             classification and segmentation algorithm was used to create
             realistic and detailed 3D computational breast phantoms
             based on 230 + dedicated bCT datasets from normal human
             subjects. The breast volume was identified using a coarse
             three-class fuzzy C-means segmentation algorithm which
             accounted for and removed motion blur at the breast
             periphery. Noise in the bCT data was reduced through
             application of a postreconstruction 3D bilateral filter. A
             3D adipose nonuniformity (bias field) correction was then
             applied followed by glandular segmentation using a 3D
             bias-corrected fuzzy C-means algorithm. Multiple tissue
             classes were defined including skin, adipose, and several
             fractional glandular densities. Following segmentation, a
             skin mask was produced which preserved the interdigitated
             skin, adipose, and glandular boundaries of the skin
             interior. Finally, surface modeling was used to produce
             digital phantoms with methods complementary to the XCAT
             suite of digital human phantoms.After rejecting some
             datasets due to artifacts, 224 virtual breast phantoms were
             created which emulate the complex breast parenchyma of
             actual human subjects. The volume breast density (with skin)
             ranged from 5.5% to 66.3% with a mean value of 25.3% ±
             13.2%. Breast volumes ranged from 25.0 to 2099.6 ml with a
             mean value of 716.3 ± 386.5 ml. Three breast phantoms were
             selected for imaging with digital compression (using finite
             element modeling) and simple ray-tracing, and the results
             show promise in their potential to produce realistic
             simulated mammograms.This work provides a new population of
             224 breast phantoms based on in vivo bCT data for imaging
             research. Compared to previous studies based on only a few
             prototype cases, this dataset provides a rich source of new
             cases spanning a wide range of breast types, volumes,
             densities, and parenchymal patterns.},
   Doi = {10.1118/1.4937597},
   Key = {fds322113}
}

@article{fds322738,
   Author = {Samei, E},
   Title = {Cutting to the Chase: With So Much Physics "Stuff," What Do
             Radiologists Really Need to Know?},
   Journal = {AJR. American journal of roentgenology},
   Volume = {206},
   Number = {1},
   Pages = {W9},
   Year = {2016},
   Month = {January},
   url = {http://dx.doi.org/10.2214/ajr.15.15223},
   Doi = {10.2214/ajr.15.15223},
   Key = {fds322738}
}

@article{fds322739,
   Author = {Tian, X and Samei, E},
   Title = {Accurate assessment and prediction of noise in clinical CT
             images.},
   Journal = {Medical physics},
   Volume = {43},
   Number = {1},
   Pages = {475},
   Year = {2016},
   Month = {January},
   url = {http://dx.doi.org/10.1118/1.4938588},
   Abstract = {The objectives of this study were (a) to devise a technique
             for measuring quantum noise in clinical body computed
             tomography (CT) images and (b) to develop a model for
             predicting that noise with high accuracy.The study included
             83 clinical image sets at two dose levels (clinical and 50%
             reduced dose levels). The quantum noise in clinical images
             was measured by subtracting sequential slices and filtering
             out edges. Noise was then measured in the resultant uniform
             area. The noise measurement technique was validated using 17
             clinical image cases and a turkey phantom. With a validated
             method to measure noise in clinical images, this noise was
             predicted by establishing the correlation between
             water-equivalent diameter (Dw) and noise in a variable-sized
             phantom and ascribing a noise level to the patient based on
             Dw estimated from CT image. The accuracy of this prediction
             model was validated using 66 clinical image sets.The error
             in noise measurement was within 1.5 HU across two
             reconstruction algorithms. In terms of noise prediction,
             across the 83 clinical image sets, the average discrepancies
             between predicted and measured noise were 6.9% and 6.6% for
             adaptive statistical iterative reconstruction and filtered
             back projection reconstruction, respectively.This study
             proposed a practically applicable method to assess quantum
             noise in clinical images. The image-based measurement
             technique enables automatic quality control monitoring of
             image noise in clinical practice. Further, a phantom-based
             model can accurately predict quantum noise level in patient
             images. The prediction model can be used to quantitatively
             optimize individual protocol to achieve targeted noise level
             in clinical images.},
   Doi = {10.1118/1.4938588},
   Key = {fds322739}
}

@article{fds323998,
   Author = {Lakshmanan, MN and Greenberg, JA and Samei, E and Kapadia,
             AJ},
   Title = {Design and implementation of coded aperture coherent scatter
             spectral imaging of cancerous and healthy breast tissue
             samples.},
   Journal = {Journal of medical imaging (Bellingham, Wash.)},
   Volume = {3},
   Number = {1},
   Pages = {013505},
   Year = {2016},
   Month = {January},
   url = {http://dx.doi.org/10.1117/1.jmi.3.1.013505},
   Abstract = {A scatter imaging technique for the differentiation of
             cancerous and healthy breast tissue in a heterogeneous
             sample is introduced in this work. Such a technique has
             potential utility in intraoperative margin assessment during
             lumpectomy procedures. In this work, we investigate the
             feasibility of the imaging method for tumor classification
             using Monte Carlo simulations and physical experiments. The
             coded aperture coherent scatter spectral imaging technique
             was used to reconstruct three-dimensional (3-D) images of
             breast tissue samples acquired through a single-position
             snapshot acquisition, without rotation as is required in
             coherent scatter computed tomography. We perform a
             quantitative assessment of the accuracy of the cancerous
             voxel classification using Monte Carlo simulations of the
             imaging system; describe our experimental implementation of
             coded aperture scatter imaging; show the reconstructed
             images of the breast tissue samples; and present
             segmentations of the 3-D images in order to identify the
             cancerous and healthy tissue in the samples. From the Monte
             Carlo simulations, we find that coded aperture scatter
             imaging is able to reconstruct images of the samples and
             identify the distribution of cancerous and healthy tissues
             (i.e., fibroglandular, adipose, or a mix of the two) inside
             them with a cancerous voxel identification sensitivity,
             specificity, and accuracy of 92.4%, 91.9%, and 92.0%,
             respectively. From the experimental results, we find that
             the technique is able to identify cancerous and healthy
             tissue samples and reconstruct differential coherent scatter
             cross sections that are highly correlated with those
             measured by other groups using x-ray diffraction. Coded
             aperture scatter imaging has the potential to provide
             scatter images that automatically differentiate cancerous
             and healthy tissue inside samples within a time on the order
             of a minute per slice.},
   Doi = {10.1117/1.jmi.3.1.013505},
   Key = {fds323998}
}

@article{fds269158,
   Author = {Sechopoulos, I and Ali, ESM and Badal, A and Badano, A and Boone, JM and Kyprianou, IS and Mainegra-Hing, E and McMillan, KL and McNitt-Gray,
             MF and Rogers, DWO and Samei, E and Turner, AC},
   Title = {Monte Carlo reference data sets for imaging research:
             Executive summary of the report of AAPM Research Committee
             Task Group 195.},
   Journal = {Medical physics},
   Volume = {42},
   Number = {10},
   Pages = {5679-5691},
   Year = {2015},
   Month = {October},
   ISSN = {0094-2405},
   url = {http://dx.doi.org/10.1118/1.4928676},
   Abstract = {The use of Monte Carlo simulations in diagnostic medical
             imaging research is widespread due to its flexibility and
             ability to estimate quantities that are challenging to
             measure empirically. However, any new Monte Carlo simulation
             code needs to be validated before it can be used reliably.
             The type and degree of validation required depends on the
             goals of the research project, but, typically, such
             validation involves either comparison of simulation results
             to physical measurements or to previously published results
             obtained with established Monte Carlo codes. The former is
             complicated due to nuances of experimental conditions and
             uncertainty, while the latter is challenging due to typical
             graphical presentation and lack of simulation details in
             previous publications. In addition, entering the field of
             Monte Carlo simulations in general involves a steep learning
             curve. It is not a simple task to learn how to program and
             interpret a Monte Carlo simulation, even when using one of
             the publicly available code packages. This Task Group report
             provides a common reference for benchmarking Monte Carlo
             simulations across a range of Monte Carlo codes and
             simulation scenarios. In the report, all simulation
             conditions are provided for six different Monte Carlo
             simulation cases that involve common x-ray based imaging
             research areas. The results obtained for the six cases using
             four publicly available Monte Carlo software packages are
             included in tabular form. In addition to a full description
             of all simulation conditions and results, a discussion and
             comparison of results among the Monte Carlo packages and the
             lessons learned during the compilation of these results are
             included. This abridged version of the report includes only
             an introductory description of the six cases and a brief
             example of the results of one of the cases. This work
             provides an investigator the necessary information to
             benchmark his/her Monte Carlo simulation software against
             the reference cases included here before performing his/her
             own novel research. In addition, an investigator entering
             the field of Monte Carlo simulations can use these
             descriptions and results as a self-teaching tool to ensure
             that he/she is able to perform a specific simulation
             correctly. Finally, educators can assign these cases as
             learning projects as part of course objectives or training
             programs.},
   Doi = {10.1118/1.4928676},
   Key = {fds269158}
}

@article{fds269172,
   Author = {Saiprasad, G and Filliben, J and Peskin, A and Siegel, E and Chen, J and Trimble, C and Yang, Z and Christianson, O and Samei, E and Krupinski,
             E and Dima, A},
   Title = {Evaluation of Low-Contrast Detectability of Iterative
             Reconstruction across Multiple Institutions, CT Scanner
             Manufacturers, and Radiation Exposure Levels.},
   Journal = {Radiology},
   Volume = {277},
   Number = {1},
   Pages = {124-133},
   Year = {2015},
   Month = {October},
   ISSN = {0033-8419},
   url = {http://dx.doi.org/10.1148/radiol.2015141260},
   Abstract = {To compare image resolution from iterative reconstruction
             with resolution from filtered back projection for
             low-contrast objects on phantom computed tomographic (CT)
             images across vendors and exposure levels.Randomized repeat
             scans of an American College of Radiology CT accreditation
             phantom (module 2, low contrast) were performed for multiple
             radiation exposures, vendors, and vendor iterative
             reconstruction algorithms. Eleven volunteers were presented
             with 900 images by using a custom-designed graphical user
             interface to perform a task created specifically for this
             reader study. Results were analyzed by using statistical
             graphics and analysis of variance.Across three vendors
             (blinded as A, B, and C) and across three exposure levels,
             the mean correct classification rate was higher for
             iterative reconstruction than filtered back projection (P <
             .01): 87.4% iterative reconstruction and 81.3% filtered back
             projection at 20 mGy, 70.3% iterative reconstruction and
             63.9% filtered back projection at 12 mGy, and 61.0%
             iterative reconstruction and 56.4% filtered back projection
             at 7.2 mGy. There was a significant difference in mean
             correct classification rate between vendor B and the other
             two vendors. Across all exposure levels, images obtained by
             using vendor B's scanner outperformed the other vendors,
             with a mean correct classification rate of 74.4%, while the
             mean correct classification rate for vendors A and C was
             68.1% and 68.3%, respectively. Across all readers, the mean
             correct classification rate for iterative reconstruction
             (73.0%) was higher compared with the mean correct
             classification rate for filtered back projection (67.0%).The
             potential exists to reduce radiation dose without
             compromising low-contrast detectability by using iterative
             reconstruction instead of filtered back projection. There is
             substantial variability across vendor reconstruction
             algorithms.},
   Doi = {10.1148/radiol.2015141260},
   Key = {fds269172}
}

@article{fds269161,
   Author = {Lakshmanan, MN and Harrawood, BP and Samei, E and Kapadia,
             AJ},
   Title = {Volumetric x-ray coherent scatter imaging of cancer in
             resected breast tissue: a Monte Carlo study using virtual
             anthropomorphic phantoms.},
   Journal = {Physics in Medicine and Biology},
   Volume = {60},
   Number = {16},
   Pages = {6355-6370},
   Year = {2015},
   Month = {August},
   ISSN = {0031-9155},
   url = {http://dx.doi.org/10.1088/0031-9155/60/16/6355},
   Abstract = {Breast cancer patients undergoing surgery often choose to
             have a breast conserving surgery (BCS) instead of mastectomy
             for removal of only the breast tumor. If post-surgical
             analysis such as histological assessment of the resected
             tumor reveals insufficient healthy tissue margins around the
             cancerous tumor, the patient must undergo another surgery to
             remove the missed tumor tissue. Such re-excisions are
             reported to occur in 20%-70% of BCS patients. A real-time
             surgical margin assessment technique that is fast and
             consistently accurate could greatly reduce the number of
             re-excisions performed in BCS. We describe here a tumor
             margin assessment method based on x-ray coherent scatter
             computed tomography (CSCT) imaging and demonstrate its
             utility in surgical margin assessment using Monte Carlo
             simulations. A CSCT system was simulated in GEANT4 and used
             to simulate two virtual anthropomorphic CSCT scans of
             phantoms resembling surgically resected tissue. The
             resulting images were volume-rendered and found to
             distinguish cancerous tumors embedded in complex
             distributions of adipose and fibroglandular breast tissue
             (as is expected in the breast). The images exhibited
             sufficient spatial and spectral (i.e. momentum transfer)
             resolution to classify the tissue in any given voxel as
             healthy or cancerous. ROC analysis of the classification
             accuracy revealed an area under the curve of up to 0.97.
             These results indicate that coherent scatter imaging is
             promising as a possible fast and accurate surgical margin
             assessment technique.},
   Doi = {10.1088/0031-9155/60/16/6355},
   Key = {fds269161}
}

@article{fds269159,
   Author = {Segars, WP and Norris, H and Sturgeon, GM and Zhang, Y and Bond, J and Minhas, A and Tward, DJ and Ratnanather, JT and Miller, MI and Frush, D and Samei, E},
   Title = {The development of a population of 4D pediatric XCAT
             phantoms for imaging research and optimization.},
   Journal = {Medical physics},
   Volume = {42},
   Number = {8},
   Pages = {4719-4726},
   Year = {2015},
   Month = {August},
   ISSN = {0094-2405},
   url = {http://dx.doi.org/10.1118/1.4926847},
   Abstract = {We previously developed a set of highly detailed 4D
             reference pediatric extended cardiac-torso (XCAT) phantoms
             at ages of newborn, 1, 5, 10, and 15 yr with organ and
             tissue masses matched to ICRP Publication 89 values. In this
             work, we extended this reference set to a series of 64
             pediatric phantoms of varying age and height and body mass
             percentiles representative of the public at large. The
             models will provide a library of pediatric phantoms for
             optimizing pediatric imaging protocols.High resolution
             positron emission tomography-computed tomography data
             obtained from the Duke University database were reviewed by
             a practicing experienced radiologist for anatomic
             regularity. The CT portion of the data was then segmented
             with manual and semiautomatic methods to form a target model
             defined using nonuniform rational B-spline surfaces. A
             multichannel large deformation diffeomorphic metric mapping
             algorithm was used to calculate the transform from the best
             age matching pediatric XCAT reference phantom to the patient
             target. The transform was used to complete the target,
             filling in the nonsegmented structures and defining models
             for the cardiac and respiratory motions. The complete
             phantoms, consisting of thousands of structures, were then
             manually inspected for anatomical accuracy. The mass for
             each major tissue was calculated and compared to linearly
             interpolated ICRP values for different ages.Sixty four new
             pediatric phantoms were created in this manner. Each model
             contains the same level of detail as the original XCAT
             reference phantoms and also includes parameterized models
             for the cardiac and respiratory motions. For the phantoms
             that were 10 yr old and younger, we included both sets of
             reproductive organs. This gave them the capability to
             simulate both male and female anatomy. With this, the
             population can be expanded to 92. Wide anatomical variation
             was clearly seen amongst the phantom models, both in organ
             shape and size, even for models of the same age and sex. The
             phantoms can be combined with existing simulation packages
             to generate realistic pediatric imaging data from different
             modalities.This work provides a large cohort of highly
             detailed pediatric phantoms with 4D capabilities of varying
             age, height, and body mass. The population of phantoms will
             provide a vital tool with which to optimize 3D and 4D
             pediatric imaging devices and techniques in terms of image
             quality and radiation-absorbed dose.},
   Doi = {10.1118/1.4926847},
   Key = {fds269159}
}

@article{fds269160,
   Author = {Solomon, J and Wilson, J and Samei, E},
   Title = {Characteristic image quality of a third generation
             dual-source MDCT scanner: Noise, resolution, and
             detectability.},
   Journal = {Medical physics},
   Volume = {42},
   Number = {8},
   Pages = {4941-4953},
   Year = {2015},
   Month = {August},
   ISSN = {0094-2405},
   url = {http://dx.doi.org/10.1118/1.4923172},
   Abstract = {The purpose of this work was to assess the inherent image
             quality characteristics of a new multidetector computed
             tomography system in terms of noise, resolution, and
             detectability index as a function of image acquisition and
             reconstruction for a range of clinically relevant settings.A
             multisized image quality phantom (37, 30, 23, 18.5, and 12
             cm physical diameter) was imaged on a SOMATOM Force scanner
             (Siemens Medical Solutions) under variable dose, kVp, and
             tube current modulation settings. Images were reconstructed
             with filtered back projection (FBP) and with advanced
             modeled iterative reconstruction (ADMIRE) with iterative
             strengths of 3, 4, and 5. Image quality was assessed in
             terms of the noise power spectrum (NPS), task transfer
             function (TTF), and detectability index for a range of
             detection tasks (contrasts of approximately 45, 90, 300,
             -900, and 1000 HU, and 2-20 mm diameter) based on a
             non-prewhitening matched filter model observer with eye
             filter.Image noise magnitude decreased with decreasing
             phantom size, increasing dose, and increasing ADMIRE
             strength, offering up to 64% noise reduction relative to
             FBP. Noise texture in terms of the NPS was similar between
             FBP and ADMIRE (<5% shift in peak frequency). The
             resolution, based on the TTF, improved with increased ADMIRE
             strength by an average of 15% in the TTF 50% frequency for
             ADMIRE-5. The detectability index increased with increasing
             dose and ADMIRE strength by an average of 55%, 90%, and 163%
             for ADMIRE 3, 4, and 5, respectively. Assessing the impact
             of mA modulation for a fixed average dose over the length of
             the phantom, detectability was up to 49% lower in smaller
             phantom sections and up to 26% higher in larger phantom
             sections for the modulated scan compared to a fixed tube
             current scan. Overall, the detectability exhibited less
             variability with phantom size for modulated scans compared
             to fixed tube current scans.Image quality increased with
             increasing dose and decreasing phantom size. The CT system
             exhibited nonlinear noise and resolution properties,
             especially at very low-doses, large phantom sizes, and for
             low-contrast objects. Objective image quality metrics
             generally increased with increasing dose and ADMIRE
             strength, and with decreasing phantom size. The ADMIRE
             algorithm could offer comparable image quality at reduced
             doses or improved image quality at the same dose. The use of
             tube current modulation resulted in more consistent image
             quality with changing phantom size.},
   Doi = {10.1118/1.4923172},
   Key = {fds269160}
}

@article{fds269167,
   Author = {Kiarashi, N and Nolte, AC and Sturgeon, GM and Segars, WP and Ghate, SV and Nolte, LW and Samei, E and Lo, JY},
   Title = {Development of realistic physical breast phantoms matched to
             virtual breast phantoms based on human subject
             data.},
   Journal = {Medical physics},
   Volume = {42},
   Number = {7},
   Pages = {4116-4126},
   Year = {2015},
   Month = {July},
   ISSN = {0094-2405},
   url = {http://dx.doi.org/10.1118/1.4919771},
   Abstract = {Physical phantoms are essential for the development,
             optimization, and evaluation of x-ray breast imaging
             systems. Recognizing the major effect of anatomy on image
             quality and clinical performance, such phantoms should
             ideally reflect the three-dimensional structure of the human
             breast. Currently, there is no commercially available
             three-dimensional physical breast phantom that is
             anthropomorphic. The authors present the development of a
             new suite of physical breast phantoms based on human
             data.The phantoms were designed to match the extended
             cardiac-torso virtual breast phantoms that were based on
             dedicated breast computed tomography images of human
             subjects. The phantoms were fabricated by high-resolution
             multimaterial additive manufacturing (3D printing)
             technology. The glandular equivalency of the photopolymer
             materials was measured relative to breast tissue-equivalent
             plastic materials. Based on the current state-of-the-art in
             the technology and available materials, two variations were
             fabricated. The first was a dual-material phantom, the
             Doublet. Fibroglandular tissue and skin were represented by
             the most radiographically dense material available; adipose
             tissue was represented by the least radiographically dense
             material. The second variation, the Singlet, was fabricated
             with a single material to represent fibroglandular tissue
             and skin. It was subsequently filled with adipose-equivalent
             materials including oil, beeswax, and permanent
             urethane-based polymer. Simulated microcalcification
             clusters were further included in the phantoms via crushed
             eggshells. The phantoms were imaged and characterized
             visually and quantitatively.The mammographic projections and
             tomosynthesis reconstructed images of the fabricated
             phantoms yielded realistic breast background. The mammograms
             of the phantoms demonstrated close correlation with
             simulated mammographic projection images of the
             corresponding virtual phantoms. Furthermore, power-law
             descriptions of the phantom images were in general agreement
             with real human images. The Singlet approach offered more
             realistic contrast as compared to the Doublet approach, but
             at the expense of air bubbles and air pockets that formed
             during the filling process.The presented physical breast
             phantoms and their matching virtual breast phantoms offer
             realistic breast anatomy, patient variability, and ease of
             use, making them a potential candidate for performing both
             system quality control testing and virtual clinical
             trials.},
   Doi = {10.1118/1.4919771},
   Key = {fds269167}
}

@article{fds269170,
   Author = {Christianson, O and Winslow, J and Frush, DP and Samei,
             E},
   Title = {Automated Technique to Measure Noise in Clinical CT
             Examinations.},
   Journal = {AJR. American journal of roentgenology},
   Volume = {205},
   Number = {1},
   Pages = {W93-W99},
   Year = {2015},
   Month = {July},
   ISSN = {0361-803X},
   url = {http://dx.doi.org/10.2214/ajr.14.13613},
   Abstract = {OBJECTIVE: The purpose of this study was to develop and
             validate an automated method to measure noise in clinical CT
             examinations. MATERIALS AND METHODS: An automated algorithm
             was developed to measure noise in CT images. To assess its
             validity, the global noise level was compared with image
             noise measured using an image subtraction technique in an
             anthropomorphic phantom. The global noise level was further
             compared with image noise values from clinical patient CT
             images obtained by an observer study. Finally, the clinical
             utility of the global noise level was shown by assessing
             variability of image noise across scanner models for
             abdominopelvic CT examinations performed in 2358 patients.
             RESULTS: The global noise level agreed well with the
             phantom-based and clinical image-based noise measurements,
             with an average difference of 3.4% and 4.7% from each of
             these measures, respectively. No significant difference was
             detected between the global noise level and the validation
             dataset in either case. It further indicated differences
             across scanners, with the median global noise level varying
             significantly between different scanner models (15-35%).
             CONCLUSION: The global noise level provides an accurate,
             robust, and automated method to measure CT noise in clinical
             examinations for quality assurance programs. The significant
             difference in noise across scanner models indicates the
             unexploited potential to efficiently assess and subsequently
             improve protocol consistency. Combined with other automated
             characterization of imaging performance (e.g., dose
             monitoring), the global noise level may offer a promising
             platform for the standardization and optimization of CT
             protocols.},
   Doi = {10.2214/ajr.14.13613},
   Key = {fds269170}
}

@article{fds269171,
   Author = {Samei, E and Thompson, J and Richard, S and Bowsher,
             J},
   Title = {A Case for Wide-Angle Breast Tomosynthesis.},
   Journal = {Academic Radiology},
   Volume = {22},
   Number = {7},
   Pages = {860-869},
   Year = {2015},
   Month = {July},
   ISSN = {1076-6332},
   url = {http://dx.doi.org/10.1016/j.acra.2015.02.015},
   Abstract = {Conventional mammography is largely limited by superimposed
             anatomy. Digital breast tomosynthesis (DBT) and computed
             tomography (CT) alleviate this limitation but with added
             out-of-plane artifacts or limited chest wall coverage. This
             article presents a wide-angle breast tomosynthesis (WBT),
             aimed to provide a practical solution to these limitations,
             and offers an initial study of its utility in comparison
             with DBT and CT using a singular evaluation platform.Using
             an anthropomorphic virtual breast phantom, a Monte Carlo
             code modeled a breast imaging system for three modalities of
             DBT, WBT, and breast CT (44°, 99°, and 198° total angle
             range, respectively) at four breast compression levels, all
             at a constant mean glandular dose level of 1.5 mGy.
             Reconstructed volumes were generated using iterative
             reconstruction methods. Lesion detectability was estimated
             using contrast-to-noise ratio and a channelized Hotelling
             observer model in terms of the area under the receiver
             operating characteristic (AUC).Results showed improved
             detection with increased angular span and compression. The
             estimated AUCs for WBT were similar to that of CT.
             Comparative performance averaged over all thicknesses
             between CT and WBT was 4.3 ± 3.0%, whereas that between WBT
             and DBT was 5.6 ± 1.0%. At compression levels reflective of
             the modality (7-, 5-, and 4-cm thickness for CT, WBT, and
             DBT, respectively), WBT yielded an AUC comparable to CT
             (performance difference of 1.2%) but superior to DBT
             (performance difference of 5.5%).The proposed imaging
             modality showed significant advantages over conventional
             DBT. WBT exhibited superior imaging performance over DBT at
             lower compression levels, highlighting further potential for
             reduced breast compression.},
   Doi = {10.1016/j.acra.2015.02.015},
   Key = {fds269171}
}

@article{fds299997,
   Author = {Wells, J and Christensen, J and Samei, E},
   Title = {A Consumer Report for Mobile Digital Radiography: A Holistic
             Comparative Evaluation Across Four Systems},
   Journal = {Medical physics},
   Volume = {42},
   Number = {6},
   Pages = {3720-3720},
   Year = {2015},
   Month = {June},
   ISSN = {0094-2405},
   url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000356998303462&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
   Key = {fds299997}
}

@article{fds299994,
   Author = {Nelson, J and Wells, J and Samei, E},
   Title = {Intrinsic Image Quality Comparison of Synthesized 2-D and
             FFDM Images},
   Journal = {Medical physics},
   Volume = {42},
   Number = {6},
   Pages = {3611-3612},
   Year = {2015},
   Month = {June},
   ISSN = {0094-2405},
   url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000356998303094&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
   Key = {fds299994}
}

@article{fds299996,
   Author = {Becchetti, M and Tian, X and Segars, P and Samei,
             E},
   Title = {GPU Accelerated Monte Carlo Technique for Fast Concurrent
             Image and Dose Simulation},
   Journal = {Medical physics},
   Volume = {42},
   Number = {6},
   Pages = {3583-3584},
   Year = {2015},
   Month = {June},
   ISSN = {0094-2405},
   url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000356998302731&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
   Key = {fds299996}
}

@article{fds299995,
   Author = {Tian, X and Segars, P and Andersson, J and Pavlicek, W and Samei,
             E},
   Title = {A Reference Organ Dose Database for Body CT Examination
             Based On AAPM 246},
   Journal = {Medical physics},
   Volume = {42},
   Number = {6},
   Pages = {3746-3746},
   Year = {2015},
   Month = {June},
   ISSN = {0094-2405},
   url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000356998303553&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
   Key = {fds299995}
}

@article{fds299999,
   Author = {Sahbaee, P and Zhang, Y and Solomon, J and Becchetti, M and Segars, P and Samei, E},
   Title = {TU-G-204-04: A Unified Strategy for Bi-Factorial
             Optimization of Radiation Dose and Contrast Dose in CT
             Imaging.},
   Journal = {Medical physics},
   Volume = {42},
   Number = {6},
   Pages = {3633},
   Year = {2015},
   Month = {June},
   ISSN = {0094-2405},
   url = {http://dx.doi.org/10.1118/1.4925768},
   Abstract = {PURPOSE: To substantiate the interdependency of contrast
             dose, radiation dose, and image quality in CT towards the
             patient- specific optimization of the imaging protocols
             METHODS: The study deployed two phantom platforms. A
             variable sized (12, 18, 23, 30, 37 cm) phantom (Mercury-3.0)
             containing an iodinated insert (8.5 mgI/ml) was imaged on a
             representative CT scanner at multiple CTDI values (0.7-22.6
             mGy). The contrast and noise were measured from the
             reconstructed images for each phantom diameter. Linearly
             related to iodine-concentration, contrast-to-noise ratio
             (CNR), were calculated for 16 iodine-concentration levels
             (0-8.5 mgI/ml). The analysis was extended to a recently
             developed suit of 58 virtual human models (5D XCAT) with
             added contrast dynamics. Emulating a contrast-enhanced
             abdominal image procedure and targeting a peak-enhancement
             in aorta, each XCAT phantom was "imaged" using a simulation
             platform (CatSim, GE). 3D surfaces for each patient/size
             established the relationship between iodine-concentration,
             dose, and CNR. The ratios of change in iodine-concentration
             versus dose (IDR) to yield a constant change in CNR were
             calculated for each patient size. RESULTS: Mercury phantom
             results show the image-quality size- dependence on CTDI and
             IC levels. For desired image-quality values, the
             iso-contour-lines reflect the trade off between
             contrast-material and radiation doses. For a fixed
             iodine-concentration (4 mgI/mL), the IDR values for low (1.4
             mGy) and high (11.5 mGy) dose levels were 1.02, 1.07, 1.19,
             1.65, 1.54, and 3.14, 3.12, 3.52, 3.76, 4.06, respectively
             across five sizes. The simulation data from XCAT models
             confirmed the empirical results from Mercury phantom.
             CONCLUSION: The iodine-concentration, image quality, and
             radiation dose are interdependent. The understanding of the
             relationships between iodine-concentration, image quality,
             and radiation dose will allow for a more comprehensive
             optimization of CT imaging devices and techniques, providing
             the methodology to balance iodine-concentration and dose
             based on patient's attributes.},
   Doi = {10.1118/1.4925768},
   Key = {fds299999}
}

@article{fds299998,
   Author = {Wells, J and Zhang, L and Samei, E},
   Title = {Automated Characterization of Perceptual Quality of Clinical
             Chest Radiographs: Improvements in Lung, Spine, and Hardware
             Detection},
   Journal = {Medical physics},
   Volume = {42},
   Number = {6},
   Pages = {3695-3695},
   Year = {2015},
   Month = {June},
   ISSN = {0094-2405},
   url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000356998303374&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
   Key = {fds299998}
}

@article{fds299993,
   Author = {Willis, C and Willis, C and Nishino, T and Wells, J and Wilson, J and Samei, E},
   Title = {Medical Physics 2.0 in Practice: Automated QC Assessment of
             Clinical Chest Images},
   Journal = {Medical physics},
   Volume = {42},
   Number = {6},
   Pages = {3695-3696},
   Year = {2015},
   Month = {June},
   ISSN = {0094-2405},
   url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000356998303376&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
   Key = {fds299993}
}

@article{fds269178,
   Author = {Solomon, J and Mileto, A and Ramirez-Giraldo, JC and Samei,
             E},
   Title = {Diagnostic Performance of an Advanced Modeled Iterative
             Reconstruction Algorithm for Low-Contrast Detectability with
             a Third-Generation Dual-Source Multidetector CT Scanner:
             Potential for Radiation Dose Reduction in a Multireader
             Study.},
   Journal = {Radiology},
   Volume = {275},
   Number = {3},
   Pages = {735-745},
   Year = {2015},
   Month = {June},
   ISSN = {0033-8419},
   url = {http://dx.doi.org/10.1148/radiol.15142005},
   Abstract = {PURPOSE: To assess the effect of radiation dose reduction on
             low-contrast detectability by using an advanced modeled
             iterative reconstruction (ADMIRE; Siemens Healthcare,
             Forchheim, Germany) algorithm in a contrast-detail phantom
             with a third-generation dual-source multidetector computed
             tomography (CT) scanner. MATERIALS AND METHODS: A
             proprietary phantom with a range of low-contrast cylindrical
             objects, representing five contrast levels (range, 5-20 HU)
             and three sizes (range, 2-6 mm) was fabricated with a
             three-dimensional printer and imaged with a third-generation
             dual-source CT scanner at various radiation dose index
             levels (range, 0.74-5.8 mGy). Image data sets were
             reconstructed by using different section thicknesses (range,
             0.6-5.0 mm) and reconstruction algorithms (filtered back
             projection [FBP] and ADMIRE with a strength range of three
             to five). Eleven independent readers blinded to technique
             and reconstruction method assessed all data sets in two
             reading sessions by measuring detection accuracy with a
             two-alternative forced choice approach (first session) and
             by scoring the total number of visible object groups (second
             session). Dose reduction potentials based on both reading
             sessions were estimated. Results between FBP and ADMIRE were
             compared by using both paired t tests and analysis of
             variance tests at the 95% significance level. RESULTS:
             During the first session, detection accuracy increased with
             increasing contrast, size, and dose index (diagnostic
             accuracy range, 50%-87%; interobserver variability, ±7%).
             When compared with FBP, ADMIRE improved detection accuracy
             by 5.2% on average across the investigated variables (P <
             .001). During the second session, a significantly increased
             number of visible objects was noted with increasing
             radiation dose index, section thickness, and ADMIRE strength
             over FBP (up to 80% more visible objects, P < .001).
             Radiation dose reduction potential ranged from 56% to 60%
             and from 4% to 80% during the two sessions, respectively.
             CONCLUSION: Low-contrast detectability performance increased
             with increasing object size, object contrast, dose index,
             section thickness, and ADMIRE strength. Compared with FBP,
             ADMIRE allows a substantial radiation dose reduction while
             preserving low-contrast detectability. Online supplemental
             material is available for this article.},
   Doi = {10.1148/radiol.15142005},
   Key = {fds269178}
}

@article{fds269179,
   Author = {Christianson, O and Chen, JJS and Yang, Z and Saiprasad, G and Dima, A and Filliben, JJ and Peskin, A and Trimble, C and Siegel, EL and Samei,
             E},
   Title = {An Improved Index of Image Quality for Task-based
             Performance of CT Iterative Reconstruction across Three
             Commercial Implementations.},
   Journal = {Radiology},
   Volume = {275},
   Number = {3},
   Pages = {725-734},
   Year = {2015},
   Month = {June},
   ISSN = {0033-8419},
   url = {http://dx.doi.org/10.1148/radiol.15132091},
   Abstract = {PURPOSE: To develop and validate a metric of computed
             tomographic (CT) image quality that incorporates the noise
             texture and resolution properties of an image. MATERIALS AND
             METHODS: Images of the American College of Radiology CT
             quality assurance phantom were acquired by using three
             commercial CT systems at seven dose levels with filtered
             back projection (FBP) and iterative reconstruction (IR).
             Image quality was characterized by the contrast-to-noise
             ratio (CNR) and a detectability index (d') that incorporated
             noise texture and spatial resolution. The measured CNR and
             d' were compared with a corresponding observer study by
             using the Spearman rank correlation coefficient to determine
             how well each metric reflects the ability of an observer to
             detect subtle lesions. Statistical significance of the
             correlation between each metric and observer performance was
             determined by using a Student t distribution; P values less
             than .05 indicated a significant correlation. Additionally,
             each metric was used to estimate the dose reduction
             potential of IR algorithms while maintaining image quality.
             RESULTS: Across all dose levels, scanner models, and
             reconstruction algorithms, the d' correlated strongly with
             observer performance in the corresponding observer study (ρ
             = 0.95; P < .001), whereas the CNR correlated weakly with
             observer performance (ρ = 0.31; P = .21). Furthermore, the
             d' showed that the dose-reduction capabilities differed
             between clinical implementations (range, 12%-35%) and were
             less than those predicted from the CNR (range, 50%-54%).
             CONCLUSION: The strong correlation between the observer
             performance and the d' indicates that the d' is superior to
             the CNR for the evaluation of CT image quality. Moreover,
             the results of this study indicate that the d' improves less
             than the CNR with the use of IR, which indicates less
             potential for IR dose reduction than previously
             thought.},
   Doi = {10.1148/radiol.15132091},
   Key = {fds269179}
}

@article{fds300000,
   Author = {Nelson, J and Wells, J and Samei, E},
   Title = {TU-CD-207-08: Intrinsic Image Quality Comparison of
             Synthesized 2-D and FFDM Images.},
   Journal = {Medical physics},
   Volume = {42},
   Number = {6},
   Pages = {3611},
   Year = {2015},
   Month = {June},
   ISSN = {0094-2405},
   url = {http://dx.doi.org/10.1118/1.4925627},
   Abstract = {PURPOSE: With the combined interest of managing patient
             dose, maintaining or improving image quality, and
             maintaining or improving the diagnostic utility of
             mammographic data, this study aims to compare the intrinsic
             image quality of Hologic's synthesized 2-D (C-View) and 2-D
             FFDM images in terms of resolution, contrast, and noise.
             METHODS: This study utilized a novel 3-D printed
             anthropomorphic breast phantom in addition to the American
             College of Radiology (ACR) mammography accreditation
             phantom. Analysis of the 3-D anthropomorphic phantom
             included visual assessment of resolution and analysis of the
             normalized noise power spectrum. Analysis of the ACR phantom
             included both visual inspection and objective automated
             analysis using in-house software. The software incorporates
             image- and object-specific CNR visibility thresholds which
             account for image characteristics such as noise texture
             which affect object visualization. T- test statistical
             analysis was also performed on ACR phantom scores. RESULTS:
             The spatial resolution of C-View images is markedly lower
             (at least 50% worse) than that of FFDM. And while this is
             generally associated with the benefit of reduced relative
             noise magnitude, the noise in C-View images tends to have a
             more mottled (predominantly low-frequency) texture. In
             general, for high contrast objects, C-View provides superior
             visualization over FFDM; however this benefit diminishes for
             low contrast objects and is applicable only to objects that
             are sufficiently larger than the spatial resolution
             threshold. Based on both observer and automated ACR phantom
             analysis, between 50-70% of C-View images failed to meet ACR
             minimum accreditation requirements - primarily due to
             insufficient (unbroken) fiber visibility. CONCLUSION:
             Compared to FFDM, C-View offers better depiction of objects
             of certain size and contrast, but provides poorer overall
             resolution and noise properties. Based on these findings,
             the utilization of C-View images in the clinical setting
             requires careful consideration, especially if considering
             the discontinuation of FFDM imaging.},
   Doi = {10.1118/1.4925627},
   Key = {fds300000}
}

@article{fds300001,
   Author = {Becchetti, M and Tian, X and Segars, P and Samei,
             E},
   Title = {MO-F-CAMPUS-I-03: GPU Accelerated Monte Carlo Technique for
             Fast Concurrent Image and Dose Simulation.},
   Journal = {Medical physics},
   Volume = {42},
   Number = {6},
   Pages = {3583},
   Year = {2015},
   Month = {June},
   ISSN = {0094-2405},
   url = {http://dx.doi.org/10.1118/1.4925488},
   Abstract = {PURPOSE: To develop an accurate and fast Monte Carlo (MC)
             method of simulating CT that is capable of correlating dose
             with image quality using voxelized phantoms. METHODS: A
             realistic voxelized phantom based on patient CT data, XCAT,
             was used with a GPU accelerated MC code for helical MDCT.
             Simulations were done with both uniform density organs and
             with textured organs. The organ doses were validated using
             previous experimentally validated simulations of the same
             phantom under the same conditions. Images acquired by
             tracking photons through the phantom with MC require lengthy
             computation times due to the large number of photon
             histories necessary for accurate representation of noise. A
             substantial speed up of the process was attained by using a
             low number of photon histories with kernel denoising of the
             projections from the scattered photons. These FBP
             reconstructed images were validated against those that were
             acquired in simulations using many photon histories by
             ensuring a minimal normalized root mean square error.
             RESULTS: Organ doses simulated in the XCAT phantom are
             within 10% of the reference values. Corresponding images
             attained using projection kernel smoothing were attained
             with 3 orders of magnitude less computation time compared to
             a reference simulation using many photon histories.
             CONCLUSION: Combining GPU acceleration with kernel denoising
             of scattered photon projections in MC simulations allows
             organ dose and corresponding image quality to be attained
             with reasonable accuracy and substantially reduced
             computation time than is possible with standard simulation
             approaches.},
   Doi = {10.1118/1.4925488},
   Key = {fds300001}
}

@article{fds300002,
   Author = {Wells, J and Zhang, L and Samei, E},
   Title = {WE-G-204-07: Automated Characterization of Perceptual
             Quality of Clinical Chest Radiographs: Improvements in Lung,
             Spine, and Hardware Detection.},
   Journal = {Medical physics},
   Volume = {42},
   Number = {6},
   Pages = {3695},
   Year = {2015},
   Month = {June},
   ISSN = {0094-2405},
   url = {http://dx.doi.org/10.1118/1.4926091},
   Abstract = {PURPOSE: To develop and validate more robust methods for
             automated lung, spine, and hardware detection in AP/PA chest
             images. This work is part of a continuing effort to
             automatically characterize the perceptual image quality of
             clinical radiographs. [Y. Lin et al. Med. Phys. 39,
             7019-7031 (2012)] METHODS: Our previous implementation of
             lung/spine identification was applicable to only one vendor.
             A more generalized routine was devised based on three
             primary components: lung boundary detection, fuzzy c-means
             (FCM) clustering, and a clinically-derived lung pixel
             probability map. Boundary detection was used to constrain
             the lung segmentations. FCM clustering produced grayscale-
             and neighborhood-based pixel classification probabilities
             which are weighted by the clinically-derived probability
             maps to generate a final lung segmentation. Lung centerlines
             were set along the left-right lung midpoints. Spine
             centerlines were estimated as a weighted average of body
             contour, lateral lung contour, and intensity-based
             centerline estimates. Centerline estimation was tested on
             900 clinical AP/PA chest radiographs which included
             inpatient/outpatient, upright/bedside, men/women, and
             adult/pediatric images from multiple imaging systems. Our
             previous implementation further did not account for the
             presence of medical hardware (pacemakers, wires, implants,
             staples, stents, etc.) potentially biasing image quality
             analysis. A hardware detection algorithm was developed using
             a gradient-based thresholding method. The training and
             testing paradigm used a set of 48 images from which 1920
             51×51 pixel(2) ROIs with and 1920 ROIs without hardware
             were manually selected. RESULTS: Acceptable lung centerlines
             were generated in 98.7% of radiographs while spine
             centerlines were acceptable in 99.1% of radiographs.
             Following threshold optimization, the hardware detection
             software yielded average true positive and true negative
             rates of 92.7% and 96.9%, respectively. CONCLUSION: Updated
             segmentation and centerline estimation methods in addition
             to new gradient-based hardware detection software provide
             improved data integrity control and error-checking for
             automated clinical chest image quality characterization
             across multiple radiography systems.},
   Doi = {10.1118/1.4926091},
   Key = {fds300002}
}

@article{fds300003,
   Author = {Willis, C and Willis, C and Nishino, T and Wells, J and Wilson, J and Samei, E},
   Title = {WE-G-204-09: Medical Physics 2.0 in Practice: Automated QC
             Assessment of Clinical Chest Images.},
   Journal = {Medical physics},
   Volume = {42},
   Number = {6},
   Pages = {3695},
   Year = {2015},
   Month = {June},
   ISSN = {0094-2405},
   url = {http://dx.doi.org/10.1118/1.4926093},
   Abstract = {PURPOSE: To determine whether a proposed suite of objective
             image quality metrics for digital chest radiographs is
             useful for monitoring image quality in our clinical
             operation. METHODS: Seventeen gridless AP Chest radiographs
             from a GE Optima portable digital radiography (DR) unit
             (Group 1), seventeen (routine) PA Chest radiographs from a
             GE Discovery DR unit (Group 2), and sixteen gridless
             (non-routine) PA Chest radiographs from the same Discovery
             DR unit (Group 3) were chosen for analysis. Groups were
             selected to represent "sub-standard" (Group 1),
             "standard-of-care" (Group 2), and images with a gross
             technical error (Group 3). Group 1 images were acquired with
             lower kVp (90 vs. 125), shorter source-to-image distance
             (127cm vs 183cm) and were expected to have lower quality
             than images in Group 2. Group 3 was expected to have
             degraded contrast versus Group 2.This evaluation was
             approved by the institutional Quality Improvement Assurance
             Board (QIAB). Images were anonymized and securely
             transferred to the Duke University Clinical Imaging Physics
             Group for analysis using software previously described(1)
             and validated(2). Image quality for individual images was
             reported in terms of lung grey level(Lgl); lung noise(Ln);
             rib-lung contrast(RLc); rib sharpness(Rs); mediastinum
             detail(Md), noise(Mn), and alignment(Ma); subdiaphragm-lung
             contrast(SLc); and subdiaphragm area(Sa). Metrics were
             compared across groups. RESULTS: Metrics agreed with
             published Quality Consistency Ranges with three exceptions:
             higher Lgl, lower RLc, and SDc. Higher bit depth (16 vs 12)
             accounted for higher Lgl values in our images. Values were
             most internally consistent for Group 2. The most sensitive
             metric for distinguishing between groups was Mn followed
             closely by Ln. The least sensitive metrics were Md and RLc.
             CONCLUSION: The software appears promising for objectively
             and automatically identifying substandard images in our
             operation. The results can be used to establish local
             quality consistency ranges and action limits per facility
             preferences.},
   Doi = {10.1118/1.4926093},
   Key = {fds300003}
}

@article{fds300004,
   Author = {Wells, J and Christensen, J and Samei, E},
   Title = {TH-AB-201-12: A Consumer Report for Mobile Digital
             Radiography: A Holistic Comparative Evaluation Across Four
             Systems.},
   Journal = {Medical physics},
   Volume = {42},
   Number = {6},
   Pages = {3720},
   Year = {2015},
   Month = {June},
   ISSN = {0094-2405},
   url = {http://dx.doi.org/10.1118/1.4926196},
   Abstract = {PURPOSE: To provide a template for the comprehensive
             clinical evaluation of new imaging technologies with initial
             application to mobile digital radiography (DR). METHODS:
             Four mobile DR devices (GE Optima XR220amx+Flashpad;
             Carestream DRX Revolution+DRX-1C; Philips Mobile Diagnost
             wDR; Philips Mobile Diagnost wDR+Skyplate) were evaluated
             under four categories: 1)Technical specifications: Vendor
             data were collected and complied into a unified
             nomenclature. 2)Physical performance: Each unit underwent
             imaging physics evaluation including MTF, NPS, DQE, and grid
             artifact analysis. 3)Clinical performance: Fifteen bedside
             chest radiographs were acquired using each unit. Metadata
             were stripped and images cropped to 14:17 aspect ratio to
             ensure vendor anonymity. Six cardiothoracic radiologists
             scored the randomized images on PACS workstations using five
             criteria: overall quality, mediastinum noise, rib-lung
             contrast, lung density, and lung detail. Results were
             processed using multiple linear regression analysis.
             4)Operability performance: A survey was designed and
             administered to technologists asking questions which
             captured use, preference, and experiential data for each
             unit. To avoid impropriety, units were randomly assigned
             numbers 1-4. RESULTS: Vendor specifications were compiled
             into a single-page table enabling ready comparative review.
             All systems had MTF within 20% and NNPS within 27% of the
             average response at frequencies below 2.5 mm(-1). Units
             [1,2,4] had DQE within 19% of average while unit 3 was 49%
             below average at high-frequencies. According to grid
             artifact analysis, the best and worst results were from
             units [2,3,4,1], respectively. The radiologist study
             revealed high inter-radiologist variability which limited
             the number of significant overall results. Survey results
             uncovered clear technologist biases. In general,
             technologists value practical over optional features.
             CONCLUSION: The compilation of vendor, physicist,
             radiologist, and technologist data provides an easy means
             for healthcare professionals to compare different medical
             equipment options using a data-driven approach. This type of
             comprehensive assessment now serves as a model for new
             technology review at our institution. This work was
             supported by Duke University Health Systems.},
   Doi = {10.1118/1.4926196},
   Key = {fds300004}
}

@article{fds300005,
   Author = {Tian, X and Segars, P and Andersson, J and Pavlicek, W and Samei,
             E},
   Title = {TH-EF-BRA-07: A Reference Organ Dose Database for Body CT
             Examination Based On AAPM 246.},
   Journal = {Medical physics},
   Volume = {42},
   Number = {6},
   Pages = {3746},
   Year = {2015},
   Month = {June},
   ISSN = {0094-2405},
   url = {http://dx.doi.org/10.1118/1.4926314},
   Abstract = {PURPOSE: This study aims to establish a reference organ dose
             database for clinical body CT based on detailed modeling of
             patient anatomy and irradiation condition. METHODS: Clinical
             CT images of 40 adult patients (age range: 18-78 y.o., 22
             male, 18 female) were included. Each patient received a
             chest and abdominopelvic CT examination at our institution.
             Whole-body computer models were created from clinical CT
             data, which included most of the radiosensitive organs
             defined by ICRP Publication 103. A previously-validated
             Monte Carlo program was used to simulate organ dose for each
             patient model. The scanner spectrum, geometry and material
             information of the bowtie filter, and the tube current
             modulation (TCM) profiles were explicitly modeled. Three
             examination conditions were modeled: (1) fixed tube current
             (2) TCM exams with modest modulation strength (alpha = 0.5),
             and (3) TCM exams with strong modulation strength (alpha =
             1).The calculated organ dose values were provided as a
             reference database for dosimetry benchmarking for chest and
             abdominopelvic examinations. RESULTS: Given the examination
             CTDIvol to be 7 mGy, organ dose for chest examination were
             in the range of 1.42 mGy to 14.4 mGy. For abdominopelvic
             examination, organ dose were in the range of 1.71 mGy to
             10.5 mGy. Organ dose shows a gradual decrease with the
             increase of tube current modulation level. For chest scan,
             the average organ dose decreased 42.8% for the heart, and
             25.0% for the lungs for strong modulation scans compared to
             no modulation. For abdominopelvic scan, the average organ
             dose decreased 33.8% for the stomach and 31.6% for the liver
             when implemented with strong TCM modulation compared to no
             modulation. CONCLUSION: A database of organ dose estimation
             is provided with information available for detailed modeling
             of the patient anatomy and scanner irradiation condition.
             Such database may be used as a reference standard in
             quantification and reporting of organ doses. Research
             fundings from GE, Siemens, and Carestream.},
   Doi = {10.1118/1.4926314},
   Key = {fds300005}
}

@article{fds269176,
   Author = {Tian, X and Li, X and Segars, WP and Frush, DP and Samei,
             E},
   Title = {Prospective estimation of organ dose in CT under tube
             current modulation.},
   Journal = {Medical physics},
   Volume = {42},
   Number = {4},
   Pages = {1575-1585},
   Year = {2015},
   Month = {April},
   ISSN = {0094-2405},
   url = {http://dx.doi.org/10.1118/1.4907955},
   Abstract = {Computed tomography (CT) has been widely used worldwide as a
             tool for medical diagnosis and imaging. However, despite its
             significant clinical benefits, CT radiation dose at the
             population level has become a subject of public attention
             and concern. In this light, optimizing radiation dose has
             become a core responsibility for the CT community. As a
             fundamental step to manage and optimize dose, it may be
             beneficial to have accurate and prospective knowledge about
             the radiation dose for an individual patient. In this study,
             the authors developed a framework to prospectively estimate
             organ dose for chest and abdominopelvic CT exams under tube
             current modulation (TCM).The organ dose is mainly dependent
             on two key factors: patient anatomy and irradiation field. A
             prediction process was developed to accurately model both
             factors. To model the anatomical diversity and complexity in
             the patient population, the authors used a previously
             developed library of computational phantoms with broad
             distributions of sizes, ages, and genders. A selected
             clinical patient, represented by a computational phantom in
             the study, was optimally matched with another computational
             phantom in the library to obtain a representation of the
             patient's anatomy. To model the irradiation field, a
             previously validated Monte Carlo program was used to model
             CT scanner systems. The tube current profiles were modeled
             using a ray-tracing program as previously reported that
             theoretically emulated the variability of modulation
             profiles from major CT machine manufacturers Li et al.,
             [Phys. Med. Biol. 59, 4525-4548 (2014)]. The prediction of
             organ dose was achieved using the following process: (1)
             CTDIvol-normalized-organ dose coefficients (horgan) for
             fixed tube current were first estimated as the prediction
             basis for the computational phantoms; (2) each computation
             phantom, regarded as a clinical patient, was optimally
             matched with one computational phantom in the library; (3)
             to account for the effect of the TCM scheme, a weighted
             organ-specific CTDIvol [denoted as CTDIvol organ,weighted]
             was computed for each organ based on the TCM profile and the
             anatomy of the "matched" phantom; (4) the organ dose was
             predicted by multiplying the weighted organ-specific CTDIvol
             with the organ dose coefficients (horgan). To quantify the
             prediction accuracy, each predicted organ dose was compared
             with the corresponding organ dose simulated from the Monte
             Carlo program with the TCM profile explicitly modeled.The
             predicted organ dose showed good agreements with the
             simulated organ dose across all organs and modulation
             profiles. The average percentage error in organ dose
             estimation was generally within 20% across all organs and
             modulation profiles, except for organs located in the pelvic
             and shoulder regions. For an average CTDIvol of a CT exam of
             10 mGy, the average error at full modulation strength (α =
             1) across all organs was 0.91 mGy for chest exams, and 0.82
             mGy for abdominopelvic exams.This study developed a
             quantitative model to predict organ dose for clinical chest
             and abdominopelvic scans. Such information may aid in the
             design of optimized CT protocols in relation to a targeted
             level of image quality.},
   Doi = {10.1118/1.4907955},
   Key = {fds269176}
}

@article{fds269157,
   Author = {Samei, E and Zhang, Y and Christianson, O},
   Title = {Comment on “Comparison of patient specific dose metrics
             between chest radiography, tomosynthesis, and CT for adult
             patients of wide ranging body habitus” [Med. Phys. 41(2),
             023901 (12pp.) (2014)]},
   Journal = {Medical physics},
   Volume = {42},
   Number = {4},
   Pages = {2094-2095},
   Year = {2015},
   Month = {March},
   ISSN = {0094-2405},
   url = {http://dx.doi.org/10.1118/1.4914374},
   Doi = {10.1118/1.4914374},
   Key = {fds269157}
}

@article{fds269177,
   Author = {Wilson, JM and Samei, E},
   Title = {Implementation of the ACR Dose Index Registry.},
   Journal = {Journal of the American College of Radiology},
   Volume = {12},
   Number = {3},
   Pages = {312-313},
   Year = {2015},
   Month = {March},
   ISSN = {1546-1440},
   url = {http://dx.doi.org/10.1016/j.jacr.2014.11.019},
   Doi = {10.1016/j.jacr.2014.11.019},
   Key = {fds269177}
}

@article{fds269162,
   Author = {Tian, X and Segars, WP and Dixon, RL and Samei, E},
   Title = {Convolution-based estimation of organ dose in tube current
             modulated CT},
   Journal = {Proceedings of SPIE},
   Volume = {9412},
   Year = {2015},
   Month = {January},
   ISBN = {9781628415025},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.2082238},
   Abstract = {© 2015 SPIE. Among the various metrics that quantify
             radiation dose in computed tomography (CT), organ dose is
             one of the most representative quantities reflecting
             patient-specific radiation burden.1 Accurate estimation of
             organ dose requires one to effectively model the patient
             anatomy and the irradiation field. As illustrated in
             previous studies, the patient anatomy factor can be modeled
             using a library of computational phantoms with
             representative body habitus. 2 However, the modeling of
             irradiation field can be practically challenging, especially
             for CT exams performed with tube current modulation. The
             central challenge is to effectively quantify the scatter
             irradiation field created by the dynamic change of tube
             current. In this study, we present a convolution-based
             technique to effectively quantify the primary and scatter
             irradiation field for TCM examinations. The organ dose for a
             given clinical patient can then be rapidly determined using
             the convolution-based method, a patient-matching technique,
             and a library of computational phantoms. 58 adult patients
             were included in this study (age range: 18-70 y.o., weight
             range: 60-180 kg). One computational phantom was created
             based on the clinical images of each patient. Each patient
             was optimally matched against one of the remaining 57
             computational phantoms using a leave-one-out strategy. For
             each computational phantom, the organ dose coefficients
             (CTDI vol -normalized organ dose) under fixed tube current
             were simulated using a validated Monte Carlo simulation
             program. Such organ dose coefficients were multiplied by a
             scaling factor, (CTDI vol ) organ, convolution that
             quantifies the regional irradiation field. The
             convolution-based organ dose was compared with the organ
             dose simulated from Monte Carlo program with TCM profiles
             explicitly modeled on the original phantom created based on
             patient images. The estimation error was within 10% across
             all organs and modulation profiles for abdominopelvic
             examination. This strategy enables prospective and
             retrospective patient-specific dose estimation without the
             need of Monte Carlo simulation.},
   Doi = {10.1117/12.2082238},
   Key = {fds269162}
}

@article{fds269163,
   Author = {Lakshmanan, MN and Greenberg, JA and Samei, E and Kapadia,
             AJ},
   Title = {Experimental implementation of coded aperture coherent
             scatter spectral imaging of cancerous and healthy breast
             tissue samples},
   Journal = {Proceedings of SPIE},
   Volume = {9412},
   Year = {2015},
   Month = {January},
   ISBN = {9781628415025},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.2082318},
   Abstract = {© 2015 SPIE. A fast and accurate scatter imaging technique
             to differentiate cancerous and healthy breast tissue is
             introduced in this work. Such a technique would have
             wide-ranging clinical applications from intra-operative
             margin assessment to breast cancer screening. Coherent
             Scatter Computed Tomography (CSCT) has been shown to
             differentiate cancerous from healthy tissue, but the need to
             raster scan a pencil beam at a series of angles and slices
             in order to reconstruct 3D images makes it prohibitively
             time consuming. In this work we apply the coded aperture
             coherent scatter spectral imaging technique to reconstruct
             3D images of breast tissue samples from experimental data
             taken without the rotation usually required in CSCT. We
             present our experimental implementation of coded aperture
             scatter imaging, the reconstructed images of the breast
             tissue samples and segmentations of the 3D images in order
             to identify the cancerous and healthy tissue inside of the
             samples. We find that coded aperture scatter imaging is able
             to reconstruct images of the samples and identify the
             distribution of cancerous and healthy tissues (i.e.,
             fibroglandular, adipose, or a mix of the two) inside of
             them. Coded aperture scatter imaging has the potential to
             provide scatter images that automatically differentiate
             cancerous and healthy tissue inside of ex vivo samples
             within a time on the order of a minute.},
   Doi = {10.1117/12.2082318},
   Key = {fds269163}
}

@article{fds269164,
   Author = {Ikejimba, L and Chen, Y and Oberhofer, N and Kiarashi, N and Lo, JY and Samei, E},
   Title = {A quantitative metrology for performance characterization of
             breast tomosynthesis systems based on an anthropomorphic
             phantom},
   Journal = {Proceedings of SPIE},
   Volume = {9412},
   Year = {2015},
   Month = {January},
   ISBN = {9781628415025},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.2082594},
   Abstract = {© 2015 SPIE. Purpose: Common methods for assessing image
             quality of digital breast tomosynthesis (DBT) devices
             currently utilize simplified or otherwise unrealistic
             phantoms, which use inserts in a uniform background and
             gauge performance based on a subjective evaluation of insert
             visibility. This study proposes a different methodology to
             assess system performance using a three-dimensional
             clinically-informed anthropomorphic breast phantom. Methods:
             The system performance is assessed by imaging the phantom
             and computationally characterizing the resultant images in
             terms of several new metrics. These include a contrast index
             (reflective of local difference between adipose and
             glandular material), a contrast to noise ratio index
             (reflective of contrast against local background noise), and
             a nonuniformity index (reflective of contributions of noise
             and artifacts within uniform adipose regions). Indices were
             measured at ROI sizes of 10mm and 37 mm, respectively. The
             method was evaluated at fixed dose of 1.5 mGy AGD. Results:
             Results indicated notable differences between systems. At 10
             mm, vendor A had the highest contrast index, followed by B
             and C in that. The performance ranking was identical at the
             largest ROI size. The non-uniformity index similarly
             exhibited system-dependencies correlated with visual
             appearance of clutter from out-of-plane artifacts. Vendor A
             had the greatest NI at all ROI sizes, B had the second
             greatest, and C the least. Conclusions: The findings
             illustrate that the anthropomorphic phantom can be used as a
             quality control tool with results that are targeted to be
             more reflective of clinical performance of breast
             tomosynthesis systems of multiple manufacturers.},
   Doi = {10.1117/12.2082594},
   Key = {fds269164}
}

@article{fds269165,
   Author = {Sahbaee, P and Li, Y and Segars, P and Marin, D and Nelson, R and Samei,
             E},
   Title = {Determination of contrast media administration to achieve a
             targeted contrast enhancement in CT},
   Journal = {Proceedings of SPIE},
   Volume = {9412},
   Year = {2015},
   Month = {January},
   ISBN = {9781628415025},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.2082261},
   Abstract = {© 2015 SPIE. Contrast enhancement is a key component of CT
             imaging and offer opportunities for optimization. The design
             and optimization of new techniques however requires
             orchestration with the scan parameters and further a
             methodology to relate contrast enhancement and injection
             function. In this study, we used such a methodology to
             develop a method, analytical inverse method, to predict the
             required injection function to achieve a desired contrast
             enhancement in a given organ by incorporation of a
             physiologically based compartmental model. The method was
             evaluated across 32 different target contrast enhancement
             functions for aorta, kidney, stomach, small intestine, and
             liver. The results exhibited that the analytical inverse
             method offers accurate performance with error in the range
             of 10% deviation between the predicted and desired organ
             enhancement curves. However, this method is incapable of
             predicting the injection function based on the liver
             enhancement. The findings of this study can be useful in
             optimizing contrast medium injection function as well as the
             scan timing to provide more consistency in the way that the
             contrast enhanced CT examinations are performed. To our
             knowledge, this work is one of the first attempts to predict
             the contrast material injection function for a desired organ
             enhancement curve.},
   Doi = {10.1117/12.2082261},
   Key = {fds269165}
}

@article{fds269166,
   Author = {Kiarashi, N and Nolte, LW and Lo, JY and Segars, WP and Ghate, SV and Samei, E},
   Title = {The impact of breast structure on lesion detection in breast
             tomosynthesis},
   Journal = {Proceedings of SPIE},
   Volume = {9412},
   Year = {2015},
   Month = {January},
   ISBN = {9781628415025},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.2082473},
   Abstract = {© 2015 SPIE. Virtual clinical trials (VCT) can be carefully
             designed to inform, orient, or potentially replace clinical
             trials. The focus of this study was to demonstrate the
             capability of the sophisticated tools that can be used in
             the design, implementation, and performance analysis of
             VCTs, through characterization of the effect of background
             tissue density and heterogeneity on the detection of
             irregular masses in digital breast tomosynthesis. Twenty
             breast phantoms from the extended cardiactorso (XCAT)
             family, generated based on dedicated breast computed
             tomography of human subjects, were used to extract a total
             of 2173 volumes of interest (VOI) from simulated
             tomosynthesis images. Five different lesions, modeled after
             human subject tomosynthesis images, were embedded in the
             breasts, for a total of 6×2173 VOIs with and without
             lesions. Effects of background tissue density and
             heterogeneity on the detection of the lesions were studied
             by implementing a doubly composite hypothesis signal
             detection theory paradigm with location known exactly,
             lesion known exactly, and background known statistically.
             The results indicated that the detection performance as
             measured by the area under the receiver operating
             characteristic curve (ROC) deteriorated as density was
             increased, yielding findings consistent with clinical
             studies. The detection performance varied substantially
             across the twenty breasts. Furthermore, the log-likelihood
             ratio under H 0 and H 1 seemed to be affected by background
             tissue density and heterogeneity differently. Considering
             background tissue variability can change the outcomes of a
             VCT and is hence of crucial importance. The XCAT breast
             phantoms can address this concern by offering realistic
             modeling of background tissue variability based on a wide
             range of human subjects.},
   Doi = {10.1117/12.2082473},
   Key = {fds269166}
}

@article{fds269168,
   Author = {Solomon, J and Samei, E},
   Title = {What observer models best reflect low-contrast detectability
             in CT?},
   Journal = {Proceedings of SPIE},
   Volume = {9416},
   Year = {2015},
   Month = {January},
   ISBN = {9781628415063},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.2081655},
   Abstract = {© 2015 SPIE. The purpose of this work was to compare CT
             low-contrast detectability as measured via human perception
             experiments with observer model surrogates of image quality
             measured directly from the images. A phantom was designed
             with a range of low-contrast circular inserts representing 5
             contrast levels and 3 sizes. The phantom was imaged
             repeatedly (20 times) on a third-generation dual-source CT
             scanner (SOMATOM Definition Force, Siemens Healthcare).
             Images were reconstructed at 0.6 mm slice thickness using
             filtered back projection (FBP) and advanced modeled
             iterative reconstruction (ADMIRE) and were assessed by
             eleven blinded and independent readers using a two
             alternative forced choice (2AFC) detection experiment. The
             human scores were taken as the accuracy, averaged across
             observers. The predicted performance was computed directly
             from the images for several traditional image quality
             metrics and model observers including contrast to noise
             ratio (CNR), area weighted CNR (CNRa), non-prewhitening
             matched filter (NPW), non-prewhitening matched filter with
             an eye filter (NPWE), channelized Hotelling observer (CHO),
             and channelized Hotelling observer with internal noise
             (CHOi). The correlation between model observer predictions
             and human performance was assessed using linear regression
             analysis. The coefficient of determination (R < sup > 2 <
             /sup > ) was used as goodness-of-fit metric to determine how
             well each model observer predicts human performance. R2 was
             0.11, 0.71, 0.73, 0.77, 0.60, and 0.72 for CNR, CNRa, NPW,
             NPWE, CHO, and CHOi, respectively. The findings demonstrate
             NPW, NPWE, and CHOi all to have strong correlation with
             human performance and could be used to optimize scan and
             reconstruction settings.},
   Doi = {10.1117/12.2081655},
   Key = {fds269168}
}

@article{fds269169,
   Author = {Solomon, J and Mileto, A and Ramirez-Giraldo, JC and Samei,
             E},
   Title = {A multireader diagnostic performance study of low-contrast
             detectability on a third-generation dual-source CT scanner:
             Filtered back projection versus advanced modeled iterative
             reconstruction},
   Journal = {Proceedings of SPIE},
   Volume = {9416},
   Year = {2015},
   Month = {January},
   ISBN = {9781628415063},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.2081647},
   Abstract = {© 2015 SPIE. The purpose of this work was to compare CT
             low-contrast detectability between two reconstruction
             algorithms, filtered back-projection (FBP) and advanced
             modeled iterative reconstruction (ADMIRE). A phantom was
             designed with a range of low-contrast circular inserts
             representing 5 contrast levels and 3 sizes. The phantom was
             imaged on a third-generation dual-source CT scanner (SOMATOM
             Definition Force, Siemens Healthcare) under various dose
             levels (0.74-5.8 mGy CTDI < inf > Vol < /inf > ). Images
             were reconstructed using different settings of slice
             thickness (0.6-5 mm) and reconstruction algorithms (FBP and
             ADMIRE with strength of 3-5) and were assessed by eleven
             blinded and independent readers using a two alternative
             forced choice (2AFC) detection experiment. A second observer
             experiment was further performed in which observers scored
             the images based on the total number of visible object
             groups. Detection performance increased with increasing
             contrast, size, dose, with accuracy ranging from 50% (i.e.,
             guessing) to 87% with an average inter-observer variability
             of ±7%. The use of ADMIRE-3 increased performance by 5.2%
             resulting in an estimated dose reduction potential of
             56-60%. The results from the second experiment also showed
             increased number of visible object groups for increasing
             dose, slice thickness, and ADMIRE strength. The score
             difference between FBP and ADMIRE was 0.9, 1.3, and 2.1 for
             ADMIRE strengths of 3, 4, and 5, respectively, resulting in
             estimated dose reduction potentials between 4-80%. Overall,
             the data indicated potential to image at reduced doses while
             maintaining comparable image quality when using ADMIRE
             compared to FBP.},
   Doi = {10.1117/12.2081647},
   Key = {fds269169}
}

@article{fds269180,
   Author = {Samei, E and Richard, S},
   Title = {Assessment of the dose reduction potential of a model-based
             iterative reconstruction algorithm using a task-based
             performance metrology.},
   Journal = {Medical physics},
   Volume = {42},
   Number = {1},
   Pages = {314-323},
   Year = {2015},
   Month = {January},
   ISSN = {0094-2405},
   url = {http://dx.doi.org/10.1118/1.4903899},
   Abstract = {Different computed tomography (CT) reconstruction techniques
             offer different image quality attributes of resolution and
             noise, challenging the ability to compare their dose
             reduction potential against each other. The purpose of this
             study was to evaluate and compare the task-based imaging
             performance of CT systems to enable the assessment of the
             dose performance of a model-based iterative reconstruction
             (MBIR) to that of an adaptive statistical iterative
             reconstruction (ASIR) and a filtered back projection (FBP)
             technique.The ACR CT phantom (model 464) was imaged across a
             wide range of mA setting on a 64-slice CT scanner (GE
             Discovery CT750 HD, Waukesha, WI). Based on previous work,
             the resolution was evaluated in terms of a task-based
             modulation transfer function (MTF) using a circular-edge
             technique and images from the contrast inserts located in
             the ACR phantom. Noise performance was assessed in terms of
             the noise-power spectrum (NPS) measured from the uniform
             section of the phantom. The task-based MTF and NPS were
             combined with a task function to yield a task-based estimate
             of imaging performance, the detectability index (d'). The
             detectability index was computed as a function of dose for
             two imaging tasks corresponding to the detection of a
             relatively small and a relatively large feature (1.5 and 25
             mm, respectively). The performance of MBIR in terms of the
             d' was compared with that of ASIR and FBP to assess its dose
             reduction potential.Results indicated that MBIR exhibits a
             variability spatial resolution with respect to object
             contrast and noise while significantly reducing image noise.
             The NPS measurements for MBIR indicated a noise texture with
             a low-pass quality compared to the typical midpass noise
             found in FBP-based CT images. At comparable dose, the d' for
             MBIR was higher than those of FBP and ASIR by at least 61%
             and 19% for the small feature and the large feature tasks,
             respectively. Compared to FBP and ASIR, MBIR indicated a
             46%-84% dose reduction potential, depending on task, without
             compromising the modeled detection performance.The presented
             methodology based on ACR phantom measurements extends
             current possibilities for the assessment of CT image quality
             under the complex resolution and noise characteristics
             exhibited with statistical and iterative reconstruction
             algorithms. The findings further suggest that MBIR can
             potentially make better use of the projections data to
             reduce CT dose by approximately a factor of 2.
             Alternatively, if the dose held unchanged, it can improve
             image quality by different levels for different
             tasks.},
   Doi = {10.1118/1.4903899},
   Key = {fds269180}
}

@article{fds269181,
   Author = {Segars, WP and Rybicki, K and Norris, H and Frush, D and Samei,
             E},
   Title = {Organ localization: toward prospective patient-specific
             organ dosimetry in computed tomography.},
   Journal = {Medical physics},
   Volume = {41},
   Number = {12},
   Pages = {121908},
   Year = {2014},
   Month = {December},
   ISSN = {0094-2405},
   url = {http://dx.doi.org/10.1118/1.4901554},
   Abstract = {With increased focus on radiation dose from medical imaging,
             prospective radiation dose estimates are becoming
             increasingly desired. Using available populations of adult
             and pediatric patient phantoms, radiation dose calculations
             can be catalogued and prospectively applied to individual
             patients that best match certain anatomical characteristics.
             In doing so, the knowledge of organ size and location is a
             required element. Here, the authors develop a predictive
             model of organ locations and volumes based on an analysis of
             adult and pediatric computed tomography (CT) data.Fifty
             eight adult and 69 pediatric CT datasets were segmented and
             utilized in the study. The maximum and minimum points of the
             organs were recorded with respect to the axial distance from
             the tip of the sacrum. The axial width, midpoint, and volume
             of each organ were calculated. Linear correlations between
             these three organ parameters and patient age, BMI, weight,
             and height were determined.No statistically significant
             correlations were found in adult patients between the axial
             width, midpoint, and volume of the organs versus the patient
             age or BMI. Slight, positive linear trends were found for
             organ midpoint versus patient weight (max r(2) = 0.382, mean
             r(2) = 0.236). Similar trends were found for organ midpoint
             versus height (max r(2) = 0.439, mean r(2) = 0.200) and for
             organ volume versus height (max r(2) = 0.410, mean r(2) =
             0.153). Gaussian fits performed on probability density
             functions of the adult organs resulted in r(2)-values
             ranging from 0.96 to 0.996. The pediatric patients showed
             much stronger correlations overall. Strong correlations were
             observed between organ axial midpoint versus age, height,
             and weight (max r(2) = 0.842, mean r(2) = 0.790; max r(2) =
             0.949, mean r(2) = 0.894; and max r(2) = 0.870, mean r(2) =
             0.847, respectively). Moderate linear correlations were also
             observed for organ axial width versus height (max r(2) =
             0.772, mean r(2) = 0.562) and for organ volume versus height
             (max r(2) = 0.781, mean r(2) = 0.601).Adult patients
             exhibited small variations in organ volume and location with
             respect to height and weight, but no meaningful correlation
             existed between these parameters and age or BMI. Once
             adulthood is reached, organ morphology and positioning seem
             to remain static. However, clear trends are evident between
             pediatric organ locations versus age, height, and weight.
             Such information can be incorporated into a matching
             methodology that may provide the highest probability of
             representing the anatomy of a patient undergoing a clinical
             exam to prospectively estimate the radiation
             dose.},
   Doi = {10.1118/1.4901554},
   Key = {fds269181}
}

@article{fds269182,
   Author = {Chen, B and Ramirez Giraldo and JC and Solomon, J and Samei,
             E},
   Title = {Evaluating iterative reconstruction performance in computed
             tomography.},
   Journal = {Medical physics},
   Volume = {41},
   Number = {12},
   Pages = {121913},
   Year = {2014},
   Month = {December},
   ISSN = {0094-2405},
   url = {http://dx.doi.org/10.1118/1.4901670},
   Abstract = {Iterative reconstruction (IR) offers notable advantages in
             computed tomography (CT). However, its performance
             characterization is complicated by its potentially nonlinear
             behavior, impacting performance in terms of specific tasks.
             This study aimed to evaluate the performance of IR with both
             task-specific and task-generic strategies.The performance of
             IR in CT was mathematically assessed with an observer model
             that predicted the detection accuracy in terms of the
             detectability index (d'). d' was calculated based on the
             properties of the image noise and resolution, the observer,
             and the detection task. The characterizations of image noise
             and resolution were extended to accommodate the nonlinearity
             of IR. A library of tasks was mathematically modeled at a
             range of sizes (radius 1-4 mm), contrast levels (10-100 HU),
             and edge profiles (sharp and soft). Unique d' values were
             calculated for each task with respect to five radiation
             exposure levels (volume CT dose index, CTDIvol: 3.4-64.8
             mGy) and four reconstruction algorithms (filtered
             backprojection reconstruction, FBP; iterative reconstruction
             in imaging space, IRIS; and sinogram affirmed iterative
             reconstruction with strengths of 3 and 5, SAFIRE3 and
             SAFIRE5; all provided by Siemens Healthcare, Forchheim,
             Germany). The d' values were translated into the areas under
             the receiver operating characteristic curve (AUC) to
             represent human observer performance. For each task and
             reconstruction algorithm, a threshold dose was derived as
             the minimum dose required to achieve a threshold AUC of 0.9.
             A task-specific dose reduction potential of IR was
             calculated as the difference between the threshold doses for
             IR and FBP. A task-generic comparison was further made
             between IR and FBP in terms of the percent of all tasks
             yielding an AUC higher than the threshold.IR required less
             dose than FBP to achieve the threshold AUC. In general,
             SAFIRE5 showed the most significant dose reduction
             potentials (11-54 mGy, 77%-84%), followed by SAFIRE3 (7-36
             mGy, 50%-61%) and IRIS (6-26 mGy, 37%-50%). The dose
             reduction potentials highly depended on task size and task
             contrast, with tasks of lower contrasts and smaller sizes,
             i.e., more challenging tasks, indicating higher dose
             reductions. Softer edge profile showed higher dose reduction
             potentials with SAFIRE3 and SAFIRE5, but not with IRIS. The
             task-generic comparison between IR and FBP demonstrated the
             overall superiority of IR performance, as IR allowed a
             larger percent of tasks to exceed the threshold AUC: IRIS,
             8%-12%; SAFIRE3, 10%-16%; and SAFIRE5, 20%-33%. The
             improvement with IR was generally more pronounced at lower
             dose levels.Expanding beyond traditional contrast and noise
             based assessments of IR, we performed both task-specific and
             task-generic evaluations of IR performance. The
             task-specific evaluation demonstrated the dependency of IR's
             dose reduction potential on task attributes, which can be
             employed to optimize IR for clinical indications with
             specific range of size and contrast. The task-generic
             evaluation demonstrated IR's overall superiority over FBP in
             terms of the range of tasks exceeding a threshold
             performance level, which can be employed for general
             comparisons between algorithms.},
   Doi = {10.1118/1.4901670},
   Key = {fds269182}
}

@article{fds269183,
   Author = {Mileto, A and Nelson, RC and Samei, E and Choudhury, KR and Jaffe, TA and Wilson, JM and Marin, D},
   Title = {Dual-energy MDCT in hypervascular liver tumors: effect of
             body size on selection of the optimal monochromatic energy
             level.},
   Journal = {AJR. American journal of roentgenology},
   Volume = {203},
   Number = {6},
   Pages = {1257-1264},
   Year = {2014},
   Month = {December},
   ISSN = {0361-803X},
   url = {http://dx.doi.org/10.2214/ajr.13.12229},
   Abstract = {OBJECTIVE: The purpose of this article is to investigate the
             effect of body size on the selection of optimal
             monochromatic energy level for maximizing the conspicuity of
             hypervascular liver tumors during late hepatic arterial
             phase using dual-energy MDCT. MATERIALS AND METHODS: An
             anthropomorphic liver phantom in three body sizes and
             iodine-containing inserts simulating low- and high-contrast
             hypervascular lesions was imaged with dual- and
             single-energy MDCT at various energy levels (80, 100, 120,
             and 140 kVp). Dual-energy MDCT was also performed in 48
             patients with 114 hypervascular liver tumors; virtual
             monochromatic images were reconstructed at energy levels
             from 40 to 140 keV. The effect of body size and lesion
             iodine concentration on noise and tumor-to-liver
             contrast-to-noise ratio was compared among different
             datasets for phantoms and patients. RESULTS: The highest
             tumor-to-liver contrast-to-noise ratio was noted at 80 kVp
             for all phantom sizes. On virtual monochromatic images, the
             minimum noise was noted at 70 keV for small and medium
             phantoms and at 80 keV for the large phantom. Tumor-to-liver
             contrast-to-noise ratio was highest at 50 keV for small and
             medium phantoms and at 60 keV for the large phantom
             (p<0.0001). Compared with 80-kVp images, an optimal
             monochromatic energy level yielded a significantly higher
             (p<0.0001) tumor-to-liver contrast-to-noise ratio for
             high-contrast lesions in the large body size and for
             low-contrast lesions in all phantom sizes. In patients, the
             optimal monochromatic energy level for tumor-to-liver
             contrast-to-noise ratio increased proportionally along with
             body size (p<0.0001). CONCLUSION: Selection of the optimal
             monochromatic energy level for maximizing the conspicuity of
             hypervascular liver tumors is significantly affected by
             patient's body size.},
   Doi = {10.2214/ajr.13.12229},
   Key = {fds269183}
}

@article{fds269184,
   Author = {Samei, E and Lin, Y and Choudhury, KR and McAdams,
             HP},
   Title = {Automated characterization of perceptual quality of clinical
             chest radiographs: validation and calibration to observer
             preference.},
   Journal = {Medical physics},
   Volume = {41},
   Number = {11},
   Pages = {111918},
   Year = {2014},
   Month = {November},
   ISSN = {0094-2405},
   url = {http://dx.doi.org/10.1118/1.4899183},
   Abstract = {The authors previously proposed an image-based technique [Y.
             Lin et al. Med. Phys. 39, 7019-7031 (2012)] to assess the
             perceptual quality of clinical chest radiographs. In this
             study, an observer study was designed and conducted to
             validate the output of the program against rankings by
             expert radiologists and to establish the ranges of the
             output values that reflect the acceptable image appearance
             so the program output can be used for image quality
             optimization and tracking.Using an IRB-approved protocol,
             2500 clinical chest radiographs (PA/AP) were collected from
             our clinical operation. The images were processed through
             our perceptual quality assessment program to measure their
             appearance in terms of ten metrics of perceptual image
             quality: lung gray level, lung detail, lung noise, rib-lung
             contrast, rib sharpness, mediastinum detail, mediastinum
             noise, mediastinum alignment, subdiaphragm-lung contrast,
             and subdiaphragm area. From the results, for each targeted
             appearance attribute/metric, 18 images were selected such
             that the images presented a relatively constant appearance
             with respect to all metrics except the targeted one. The
             images were then incorporated into a graphical user
             interface, which displayed them into three panels of six in
             a random order. Using a DICOM calibrated diagnostic display
             workstation and under low ambient lighting conditions, each
             of five participating attending chest radiologists was
             tasked to spatially order the images based only on the
             targeted appearance attribute regardless of the other
             qualities. Once ordered, the observer also indicated the
             range of image appearances that he/she considered clinically
             acceptable. The observer data were analyzed in terms of the
             correlations between the observer and algorithmic rankings
             and interobserver variability. An observer-averaged
             acceptable image appearance was also statistically derived
             for each quality attribute based on the collected individual
             acceptable ranges.The observer study indicated that, for
             each image quality attribute, the averaged observer ranking
             strongly correlated with the algorithmic ranking (linear
             correlation coefficient R > 0.92), with highest correlation
             (R = 1) for lung gray level and the lowest (R = 0.92) for
             mediastinum noise. There was a strong concordance between
             the observers in terms of their rankings (i.e., Kendall's
             tau agreement > 0.84). The observers also generally
             indicated similar tolerance and preference levels in terms
             of acceptable ranges, as 85% of the values were close to the
             overall tolerance or preference levels and the differences
             were smaller than 0.15.The observer study indicates that the
             previously proposed technique provides a robust reflection
             of the perceptual image quality in clinical images. The
             results established the range of algorithmic outputs for
             each metric that can be used to quantitatively assess and
             qualify the appearance quality of clinical chest
             radiographs.},
   Doi = {10.1118/1.4899183},
   Key = {fds269184}
}

@article{fds269185,
   Author = {Solomon, J and Samei, E},
   Title = {A generic framework to simulate realistic lung, liver and
             renal pathologies in CT imaging.},
   Journal = {Physics in Medicine and Biology},
   Volume = {59},
   Number = {21},
   Pages = {6637-6657},
   Year = {2014},
   Month = {November},
   ISSN = {0031-9155},
   url = {http://dx.doi.org/10.1088/0031-9155/59/21/6637},
   Abstract = {Realistic three-dimensional (3D) mathematical models of
             subtle lesions are essential for many computed tomography
             (CT) studies focused on performance evaluation and
             optimization. In this paper, we develop a generic
             mathematical framework that describes the 3D size, shape,
             contrast, and contrast-profile characteristics of a lesion,
             as well as a method to create lesion models based on CT data
             of real lesions. Further, we implemented a technique to
             insert the lesion models into CT images in order to create
             hybrid CT datasets. This framework was used to create a
             library of realistic lesion models and corresponding hybrid
             CT images. The goodness of fit of the models was assessed
             using the coefficient of determination (R(2)) and the visual
             appearance of the hybrid images was assessed with an
             observer study using images of both real and simulated
             lesions and receiver operator characteristic (ROC) analysis.
             The average R(2) of the lesion models was 0.80, implying
             that the models provide a good fit to real lesion data. The
             area under the ROC curve was 0.55, implying that the
             observers could not readily distinguish between real and
             simulated lesions. Therefore, we conclude that the
             lesion-modeling framework presented in this paper can be
             used to create realistic lesion models and hybrid CT images.
             These models could be instrumental in performance evaluation
             and optimization of novel CT systems.},
   Doi = {10.1088/0031-9155/59/21/6637},
   Key = {fds269185}
}

@article{fds269186,
   Author = {Samei, E},
   Title = {Pros and cons of organ shielding for CT imaging.},
   Journal = {Pediatric Radiology},
   Volume = {44 Suppl 3},
   Pages = {495-500},
   Year = {2014},
   Month = {October},
   ISSN = {0301-0449},
   url = {http://dx.doi.org/10.1007/s00247-014-3084-z},
   Abstract = {With the increased importance of CT radiation dose to health
             care providers, patients and the general public, there is an
             increased responsibility to minimize patient dose
             effectively. Bismuth shields offer a simple strategy to
             reduce dose to certain anterior radiosensitive organs such
             as breasts and eyes. However, in order to reduce organ dose
             they must be used properly; improper use can lead to an
             actual increase in the patient dose. They also create a
             proportional increase in image noise in the section of the
             body adjacent to the shield and further reduce the
             quantitative precision of CT numbers. In addition, shielding
             can degrade the overall efficiency (by an order of
             approximately 10%) of the imaging process, reducing the
             theoretical image quality that can be expected from a
             certain level of patient dose. However, in spite of their
             significant disadvantages, there are certain clinical
             situations and practice considerations that provide
             qualified justification for their continued
             use.},
   Doi = {10.1007/s00247-014-3084-z},
   Key = {fds269186}
}

@article{fds269187,
   Author = {Samei, E and Tian, X and Segars, WP},
   Title = {Determining organ dose: the holy grail.},
   Journal = {Pediatric Radiology},
   Volume = {44 Suppl 3},
   Pages = {460-467},
   Year = {2014},
   Month = {October},
   ISSN = {0301-0449},
   url = {http://dx.doi.org/10.1007/s00247-014-3117-7},
   Abstract = {Among the various metrics to quantify CT radiation dose,
             organ dose is generally regarded as one of the best to
             reflect patient radiation burden. Organ dose is dependent on
             two main factors, namely patient anatomy and irradiation
             field. An accurate estimation of organ dose requires
             detailed modeling of both factors. The modeling of patient
             anatomy needs to reflect the anatomical diversity and
             complexity across the population so that the attributes of a
             given clinical patient can be properly accounted for. The
             modeling of the irradiation field needs to accurately
             reflect the CT system condition, especially the tube current
             modulation (TCM) technique. We present an atlas-based method
             to model patient anatomy via a library of computational
             phantoms with representative ages, sizes and genders. A
             clinical patient is matched with a corresponding
             computational phantom to obtain a representation of patient
             anatomy. The irradiation field of the CT system is modeled
             using a validated Monte Carlo simulation program. The tube
             current modulation profiles are simulated using a
             manufacturer-generalizable ray-tracing algorithm. Combining
             the patient model, Monte Carlo results, and TCM profile,
             organ doses are obtained by multiplying organ dose values
             from a fixed mA scan (normalized to CTDIvol-normalized,
             denoted as h organ ) and an adjustment factor that reflects
             the specific irradiation of each organ. The accuracy of the
             proposed method was quantified by simulating clinical
             abdominopelvic examinations of 58 patients. The predicted
             organ doses showed good agreement with simulated organ dose
             across all organs and modulation schemes. For an average
             CTDIvol of a CT exam of 10 mGy, the absolute median error
             across all organs was 0.64 mGy (-0.21 and 0.97 for 25th and
             75th percentiles, respectively). The percentage differences
             were within 15%. The study demonstrates that it is feasible
             to estimate organ doses in clinical CT examinations for
             protocols without and with tube current modulation. The
             methodology can be used for both prospective and
             retrospective estimation of organ dose.},
   Doi = {10.1007/s00247-014-3117-7},
   Key = {fds269187}
}

@article{fds269188,
   Author = {Solomon, J and Samei, E},
   Title = {Quantum noise properties of CT images with anatomical
             textured backgrounds across reconstruction algorithms: FBP
             and SAFIRE.},
   Journal = {Medical physics},
   Volume = {41},
   Number = {9},
   Pages = {091908},
   Year = {2014},
   Month = {September},
   ISSN = {0094-2405},
   url = {http://dx.doi.org/10.1118/1.4893497},
   Abstract = {Quantum noise properties of CT images are generally assessed
             using simple geometric phantoms with uniform backgrounds.
             Such phantoms may be inadequate when assessing nonlinear
             reconstruction or postprocessing algorithms. The purpose of
             this study was to design anatomically informed textured
             phantoms and use the phantoms to assess quantum noise
             properties across two clinically available reconstruction
             algorithms, filtered back projection (FBP) and sinogram
             affirmed iterative reconstruction (SAFIRE).Two phantoms were
             designed to represent lung and soft-tissue textures. The
             lung phantom included intricate vessel-like structures along
             with embedded nodules (spherical, lobulated, and
             spiculated). The soft tissue phantom was designed based on a
             three-dimensional clustered lumpy background with included
             low-contrast lesions (spherical and anthropomorphic). The
             phantoms were built using rapid prototyping (3D printing)
             technology and, along with a uniform phantom of similar
             size, were imaged on a Siemens SOMATOM Definition Flash CT
             scanner and reconstructed with FBP and SAFIRE. Fifty
             repeated acquisitions were acquired for each background type
             and noise was assessed by estimating pixel-value statistics,
             such as standard deviation (i.e., noise magnitude),
             autocorrelation, and noise power spectrum. Noise
             stationarity was also assessed by examining the spatial
             distribution of noise magnitude. The noise properties were
             compared across background types and between the two
             reconstruction algorithms.In FBP and SAFIRE images, noise
             was globally nonstationary for all phantoms. In FBP images
             of all phantoms, and in SAFIRE images of the uniform
             phantom, noise appeared to be locally stationary (within a
             reasonably small region of interest). Noise was locally
             nonstationary in SAFIRE images of the textured phantoms with
             edge pixels showing higher noise magnitude compared to
             pixels in more homogenous regions. For pixels in uniform
             regions, noise magnitude was reduced by an average of 60% in
             SAFIRE images compared to FBP. However, for edge pixels,
             noise magnitude ranged from 20% higher to 40% lower in
             SAFIRE images compared to FBP. SAFIRE images of the lung
             phantom exhibited distinct regions with varying noise
             texture (i.e., noise autocorrelation/power spectra).Quantum
             noise properties observed in uniform phantoms may not be
             representative of those in actual patients for nonlinear
             reconstruction algorithms. Anatomical texture should be
             considered when evaluating the performance of CT systems
             that use such nonlinear algorithms.},
   Doi = {10.1118/1.4893497},
   Key = {fds269188}
}

@article{fds269193,
   Author = {Lakshmanan, MN and Kapadia, AJ and Sahbaee, P and Wolter, SD and Harrawood, BP and Brady, D and Samei, E},
   Title = {An X-ray scatter system for material identification in
             cluttered objects: A Monte Carlo simulation
             study},
   Journal = {Nuclear Instruments and Methods in Physics Research Section
             B: Beam Interactions with Materials and Atoms},
   Volume = {335},
   Pages = {31-38},
   Year = {2014},
   Month = {September},
   ISSN = {0168-583X},
   url = {http://dx.doi.org/10.1016/j.nimb.2014.05.021},
   Doi = {10.1016/j.nimb.2014.05.021},
   Key = {fds269193}
}

@article{fds269209,
   Author = {Mileto, A and Nelson, RC and Samei, E and Jaffe, TA and Paulson, EK and Barina, A and Choudhury, KR and Wilson, JM and Marin,
             D},
   Title = {Impact of dual-energy multi-detector row CT with virtual
             monochromatic imaging on renal cyst pseudoenhancement: in
             vitro and in vivo study.},
   Journal = {Radiology},
   Volume = {272},
   Number = {3},
   Pages = {767-776},
   Year = {2014},
   Month = {September},
   ISSN = {0033-8419},
   url = {http://dx.doi.org/10.1148/radiol.14132856},
   Abstract = {PURPOSE: To investigate whether dual-energy multi-detector
             row computed tomography (CT) with virtual monochromatic
             imaging can overcome renal cyst pseudoenhancement in a
             phantom experiment and a clinical study. MATERIALS AND
             METHODS: This retrospective single-center HIPAA-compliant
             study was approved by the institutional review board, with
             waiver of informed consent. Four renal compartments inserted
             into torso phantoms were filled with saline to simulate the
             unenhanced state and with iodinated solutions to simulate
             the three levels of renal parenchyma enhancement (140, 180,
             and 240 HU). Saline-filled spheres simulating renal cysts
             (15 and 18 mm in diameter) were serially suspended in the
             renal compartments and imaged with dual-energy and
             single-energy multi-detector row CT at four different energy
             levels (80, 100, 120, and 140 kVp). In addition, 28 patients
             (mean age, 66 years ± 10; mean body mass index, 31.3
             kg/m(2) ± 6.2) with 34 intrarenal cysts were included.
             Virtual monochromatic images were reconstructed in 10-keV
             increments at energy levels ranging from 40 to 140 keV.
             Phantom and clinical data were analyzed by using
             multivariate regression analysis. RESULTS: In the phantom
             experiment, all polychromatic image data sets showed
             pseudoenhancement (postcontrast attenuation increase >10 HU)
             in all investigated conditions, with a significant effect on
             cyst size (P <.001), location (P <.001), and renal
             background attenuation level (P <.001). Virtual
             monochromatic images at energy levels ranging from 80 to 140
             keV did not show pseudoenhancement, with the minimum
             attenuation increase (mean, 6.1 HU ± 1.6; range, 1.6-7.7
             HU) on 80-keV images. In patients, pseudoenhancement never
             occurred on virtual monochromatic images at energy levels
             ranging from 90 to 140 keV. Patient body size had a
             significant effect (P = .007) on selection of the optimal
             monochromatic energy level. CONCLUSION: Dual-energy
             multi-detector row CT with reconstruction of virtual
             monochromatic images at an optimal energy level can overcome
             renal cyst pseudoenhancement.},
   Doi = {10.1148/radiol.14132856},
   Key = {fds269209}
}

@article{fds269189,
   Author = {Li, X and Segars, WP and Samei, E},
   Title = {The impact on CT dose of the variability in tube current
             modulation technology: a theoretical investigation.},
   Journal = {Physics in Medicine and Biology},
   Volume = {59},
   Number = {16},
   Pages = {4525-4548},
   Year = {2014},
   Month = {August},
   ISSN = {0031-9155},
   url = {http://dx.doi.org/10.1088/0031-9155/59/16/4525},
   Abstract = {Body CT scans are routinely performed using
             tube-current-modulation (TCM) technology. There is notable
             variability across CT manufacturers in terms of how TCM
             technology is implemented. Some manufacturers aim to provide
             uniform image noise across body regions and patient sizes,
             whereas others aim to provide lower noise for smaller
             patients. The purpose of this study was to conduct a
             theoretical investigation to understand how
             manufacturer-dependent TCM scheme affects organ dose, and to
             develop a generic approach for assessing organ dose across
             TCM schemes. The adult reference female extended
             cardiac-torso (XCAT) phantom was used for this study. A
             ray-tracing method was developed to calculate the
             attenuation of the phantom for a given projection angle
             based on phantom anatomy, CT system geometry, x-ray energy
             spectrum, and bowtie filter filtration. The tube current
             (mA) for a given projection angle was then calculated as a
             log-linear function of the attenuation along that
             projection. The slope of this function, termed modulation
             control strength, α, was varied from 0 to 1 to emulate the
             variability in TCM technology. Using a validated Monte Carlo
             program, organ dose was simulated for five α values (α =
             0, 0.25, 0.5, 0.75, and 1) in the absence and presence of a
             realistic system mA limit. Organ dose was further normalized
             by volume-weighted CT dose index (CTDIvol) to obtain
             conversion factors (h factors) that are relatively
             independent of system specifics and scan parameters. For
             both chest and abdomen-pelvis scans and for 24
             radiosensitive organs, organ dose conversion factors varied
             with α, following second-order polynomial equations. This
             result suggested the need for α-specific organ dose
             conversion factors (i.e., conversion factors specific to the
             modulation scheme used). On the other hand, across the full
             range of α values, organ dose in a TCM scan could be
             derived from the conversion factors established for a
             fixed-mA scan (hFIXED). This was possible by multiplying
             hFIXED by a revised definition of CTDIvol that accounts for
             two factors: (a) the tube currents at the location of an
             organ and (b) the variation in organ volume along the
             longitudinal direction. This α-generic approach represents
             an approximation. The error associated with this
             approximation was evaluated using the α-specific organ dose
             (i.e., the organ dose obtained by using α-specific mA
             profiles as inputs into the Monte Carlo simulation) as the
             reference standard. When the mA profiles were constrained by
             a realistic system limit, this α-generic approach had
             errors of less than ~20% for the full range of α values.
             This was the case for 24 radiosensitive organs in both chest
             and abdomen-pelvis CT scans with the exception of thyroid in
             the chest scan and bladder in the abdomen-pelvis scan. For
             these two organs, the errors were less than ~40%. The
             results of this theoretical study suggested that knowing the
             mA modulation profile and the fixed-mA conversion factors,
             organ dose may be estimated for a TCM scan independent of
             the specific modulation scheme applied.},
   Doi = {10.1088/0031-9155/59/16/4525},
   Key = {fds269189}
}

@article{fds269191,
   Author = {Samei, E and Richard, S and Lurwitz, L},
   Title = {Model-based CT performance assessment and optimization for
             iodinated and noniodinated imaging tasks as a function of
             kVp and body size.},
   Journal = {Medical physics},
   Volume = {41},
   Number = {8},
   Pages = {081910},
   Year = {2014},
   Month = {August},
   ISSN = {0094-2405},
   url = {http://dx.doi.org/10.1118/1.4890082},
   Abstract = {The goal of this study was to assess the comparative
             performance of iterative reconstruction in space (IRIS) and
             filtered back projection (FBP) reconstruction algorithms in
             terms of image quality and dose across kVps and phantom
             sizes.The ACR CT phantom (model 464) was supplemented with
             the addition of an iodinated spherical capsule (1.5 mm
             diameter, 3.4 mg iodine per ml) to simulate the contrast
             filled structures and with an additional circular attachment
             consisting of an array of 500 um brass beads for spatial
             resolution measurements. A larger sized phantom was also
             created by wrapping the original phantom with additional
             tissue equivalent material of 4 cm thickness. The phantoms
             were imaged on a 64 detector array multidetector computed
             tomography scanner (Somatom Definition, Siemens, Germany)
             using clinically applicable protocols (0.5 s rotation time;
             80, 100, 120, and 140 kVp; 64 to 640 mA; 220 to 250 mm field
             of view). Images were reconstructed using the FBP and the
             IRIS algorithms. Combining measurements of image noise and
             spatial resolution with a task function, a figure of merit
             (FOM) for image quality was generated taking into account
             the type of visualization required from the image for the
             detection of either large or small image features with and
             without iodine content. The FOM was further reported in
             terms of area under the receiver operating characteristic
             (ROC) curve (AZ) to predict the comparative diagnostic
             performance of the two algorithms at different dose
             levels.For a given dose level, the predicted AZ for IRIS
             consistently outperformed that of FBP. At comparative AZ,
             depending on protocol and task, the dose requirement for the
             optimal technique (optimized kVp with IRIS) was 2-3 times
             lower than that for standard technique (120 kVp with FBP).
             The potential for dose reduction was found to be higher when
             performing small feature detection tasks in comparison to
             larger feature detection tasks. The optimal kVp was from 80
             to 100 kVp for the small phantom, 100 to 120 kVp for the
             larger phantom.Overall, greater dose reduction may be
             achieved with IRIS compared to FBP, with enhanced advantage
             at thinner slice reconstructions. The results highlight how
             IRIS may offer a superior balance between image quality and
             dose across a range of imaging tasks, thus enabling dose
             reduction at constant quality or image quality improvement
             at constant dose. The prediction of the investigation can be
             used toward effective design of subsequent clinical
             studies.},
   Doi = {10.1118/1.4890082},
   Key = {fds269191}
}

@article{fds269196,
   Author = {Samei, E and Christianson, O},
   Title = {Dose index analytics: more than a low number.},
   Journal = {Journal of the American College of Radiology},
   Volume = {11},
   Number = {8},
   Pages = {832-834},
   Year = {2014},
   Month = {August},
   ISSN = {1546-1440},
   url = {http://dx.doi.org/10.1016/j.jacr.2014.05.004},
   Doi = {10.1016/j.jacr.2014.05.004},
   Key = {fds269196}
}

@article{fds269192,
   Author = {Kiarashi, N and Lo, JY and Lin, Y and Ikejimba, LC and Ghate, SV and Nolte,
             LW and Dobbins, JT and Segars, WP and Samei, E},
   Title = {Development and application of a suite of 4-D virtual breast
             phantoms for optimization and evaluation of breast imaging
             systems.},
   Journal = {IEEE Transactions on Medical Imaging},
   Volume = {33},
   Number = {7},
   Pages = {1401-1409},
   Year = {2014},
   Month = {July},
   ISSN = {0278-0062},
   url = {http://dx.doi.org/10.1109/tmi.2014.2312733},
   Abstract = {Mammography is currently the most widely utilized tool for
             detection and diagnosis of breast cancer. However, in women
             with dense breast tissue, tissue overlap may obscure
             lesions. Digital breast tomosynthesis can reduce tissue
             overlap. Furthermore, imaging with contrast enhancement can
             provide additional functional information about lesions,
             such as morphology and kinetics, which in turn may improve
             lesion identification and characterization. The performance
             of these imaging techniques is strongly dependent on the
             structural composition of the breast, which varies
             significantly among patients. Therefore, imaging system and
             imaging technique optimization should take patient
             variability into consideration. Furthermore, optimization of
             imaging techniques that employ contrast agents should
             include the temporally varying breast composition with
             respect to the contrast agent uptake kinetics. To these
             ends, we have developed a suite of 4-D virtual breast
             phantoms, which are incorporated with the kinetics of
             contrast agent propagation in different tissues and can
             realistically model normal breast parenchyma as well as
             benign and malignant lesions. This development presents a
             new approach in performing simulation studies using truly
             anthropomorphic models. To demonstrate the utility of the
             proposed 4-D phantoms, we present a simplified example study
             to compare the performance of 14 imaging paradigms
             qualitatively and quantitatively.},
   Doi = {10.1109/tmi.2014.2312733},
   Key = {fds269192}
}

@article{fds269194,
   Author = {Chen, B and Christianson, O and Wilson, JM and Samei,
             E},
   Title = {Assessment of volumetric noise and resolution performance
             for linear and nonlinear CT reconstruction
             methods.},
   Journal = {Medical physics},
   Volume = {41},
   Number = {7},
   Pages = {071909},
   Year = {2014},
   Month = {July},
   ISSN = {0094-2405},
   url = {http://dx.doi.org/10.1118/1.4881519},
   Abstract = {For nonlinear iterative image reconstructions (IR), the
             computed tomography (CT) noise and resolution properties can
             depend on the specific imaging conditions, such as lesion
             contrast and image noise level. Therefore, it is imperative
             to develop a reliable method to measure the noise and
             resolution properties under clinically relevant conditions.
             This study aimed to develop a robust methodology to measure
             the three-dimensional CT noise and resolution properties
             under such conditions and to provide guidelines to achieve
             desirable levels of accuracy and precision.The methodology
             was developed based on a previously reported CT image
             quality phantom. In this methodology, CT noise properties
             are measured in the uniform region of the phantom in terms
             of a task-based 3D noise-power spectrum (NPStask). The
             in-plane resolution properties are measured in terms of the
             task transfer function (TTF) by applying a radial edge
             technique to the rod inserts in the phantom. The z-direction
             resolution properties are measured from a supplemental
             phantom, also in terms of the TTF. To account for the
             possible nonlinearity of IR, the NPStask is measured with
             respect to the noise magnitude, and the TTF with respect to
             noise magnitude and edge contrast. To determine the accuracy
             and precision of the methodology, images of known noise and
             resolution properties were simulated. The NPStask and TTF
             were measured on the simulated images and compared to the
             truth, with criteria established to achieve NPStask and TTF
             measurements with <10% error. To demonstrate the utility of
             this methodology, measurements were performed on a
             commercial CT system using five dose levels, two slice
             thicknesses, and three reconstruction algorithms (filtered
             backprojection, FBP; iterative reconstruction in imaging
             space, IRIS; and sinogram affirmed iterative reconstruction
             with strengths of 5, SAFIRE5).To achieve NPStask
             measurements with <10% error, the number of regions of
             interest needed to be greater than 65. To achieve TTF
             measurements with <10% error, the contrast-to-noise ratio of
             the edge needed to be ≥15, achievable by averaging
             multiple slices across the same edge. The NPStask measured
             on a commercial CT system showed IR's reduced noise (IRIS,
             30% and SAFIRE5, 55%) and "waxier" texture (peak
             frequencies: FBP, 0.25 mm(-1); IRIS, 0.23 mm(-1); and
             SAFIRE5, 0.16 mm(-1)). The TTF measured within the axial
             plane showed improved in-plane resolution with SAFIRE5 at
             the TTF 50% frequency, f50 (FBP, 0.36-0.41 mm(-1); SAFIRE5,
             0.37-0.46 mm(-1)). The TTF measured along the axial
             direction showed improved z-direction resolution with
             thinner slice thickness (f50: 0.6 mm, 0.35-0.79 mm(-1);
             1.5 mm, 0.22-0.3 mm(-1)) and with SAFIRE5 (f50: FBP,
             0.35-0.52 mm(-1); SAFIRE5, 0.42-0.79 mm(-1)). Both in-plane
             and z-direction resolution of SAFIRE5 showed strong
             dependency on contrast, reflecting SAFIRE5's nonlinearity.A
             methodology was developed to measure three-dimensional CT
             noise and resolution properties for iterative
             reconstruction, especially at challenging measurement
             conditions with low contrast and high image noise. The
             methodology also demonstrated its utility for evaluating
             commercial CT systems.},
   Doi = {10.1118/1.4881519},
   Key = {fds269194}
}

@article{fds269195,
   Author = {Sahbaee, P and Segars, WP and Samei, E},
   Title = {Patient-based estimation of organ dose for a population of
             58 adult patients across 13 protocol categories.},
   Journal = {Medical physics},
   Volume = {41},
   Number = {7},
   Pages = {072104},
   Year = {2014},
   Month = {July},
   ISSN = {0094-2405},
   url = {http://dx.doi.org/10.1118/1.4883778},
   Abstract = {This study aimed to provide a comprehensive patient-specific
             organ dose estimation across a multiplicity of computed
             tomography (CT) examination protocols.A validated Monte
             Carlo program was employed to model a common CT system
             (LightSpeed VCT, GE Healthcare). The organ and effective
             doses were estimated from 13 commonly used body and
             neurological CT examination. The dose estimation was
             performed on 58 adult computational extended cardiac-torso
             phantoms (35 male, 23 female, mean age 51.5 years, mean
             weight 80.2 kg). The organ dose normalized by CTDIvol (h
             factor) and effective dose normalized by the dose length
             product (DLP) (k factor) were calculated from the results. A
             mathematical model was derived for the correlation between
             the h and k factors with the patient size across the
             protocols. Based on this mathematical model, a dose
             estimation iPhone operating system application was designed
             and developed to be used as a tool to estimate dose to the
             patients for a variety of routinely used CT examinations.The
             organ dose results across all the protocols showed an
             exponential decrease with patient body size. The correlation
             was generally strong for the organs which were fully or
             partially located inside the scan coverage (Pearson sample
             correlation coefficient (r) of 0.49). The correlation was
             weaker for organs outside the scan coverage for which
             distance between the organ and the irradiation area was a
             stronger predictor of dose to the organ. For body protocols,
             the effective dose before and after normalization by DLP
             decreased exponentially with increasing patient's body
             diameter (r > 0.85). The exponential relationship between
             effective dose and patient's body diameter was significantly
             weaker for neurological protocols (r < 0.41), where the
             trunk length was a slightly stronger predictor of effective
             dose (0.15 < r < 0.46).While the most accurate estimation of
             a patient dose requires specific modeling of the patient
             anatomy, a first order approximation of organ and effective
             doses from routine CT scan protocols can be reasonably
             estimated using size specific factors. Estimation accuracy
             is generally poor for organ outside the scan range and for
             neurological protocols. The dose calculator designed in this
             study can be used to conveniently estimate and report the
             dose values for a patient across a multiplicity of CT scan
             protocols.},
   Doi = {10.1118/1.4883778},
   Key = {fds269195}
}

@article{fds269208,
   Author = {Lin, Y and Ramirez-Giraldo, JC and Gauthier, DJ and Stierstorfer, K and Samei, E},
   Title = {An angle-dependent estimation of CT x-ray spectrum from
             rotational transmission measurements.},
   Journal = {Medical physics},
   Volume = {41},
   Number = {6},
   Pages = {062104},
   Year = {2014},
   Month = {June},
   ISSN = {0094-2405},
   url = {http://dx.doi.org/10.1118/1.4876380},
   Abstract = {Computed tomography (CT) performance as well as dose and
             image quality is directly affected by the x-ray spectrum.
             However, the current assessment approaches of the CT x-ray
             spectrum require costly measurement equipment and
             complicated operational procedures, and are often limited to
             the spectrum corresponding to the center of rotation. In
             order to address these limitations, the authors propose an
             angle-dependent estimation technique, where the incident
             spectra across a wide range of angular trajectories can be
             estimated accurately with only a single phantom and a single
             axial scan in the absence of the knowledge of the bowtie
             filter.The proposed technique uses a uniform cylindrical
             phantom, made of ultra-high-molecular-weight polyethylene
             and positioned in an off-centered geometry. The projection
             data acquired with an axial scan have a twofold purpose.
             First, they serve as a reflection of the transmission
             measurements across different angular trajectories. Second,
             they are used to reconstruct the cross sectional image of
             the phantom, which is then utilized to compute the
             intersection length of each transmission measurement. With
             each CT detector element recording a range of transmission
             measurements for a single angular trajectory, the spectrum
             is estimated for that trajectory. A data conditioning
             procedure is used to combine information from hundreds of
             collected transmission measurements to accelerate the
             estimation speed, to reduce noise, and to improve estimation
             stability. The proposed spectral estimation technique was
             validated experimentally using a clinical scanner (Somatom
             Definition Flash, Siemens Healthcare, Germany) with spectra
             provided by the manufacturer serving as the comparison
             standard. Results obtained with the proposed technique were
             compared against those obtained from a second conventional
             transmission measurement technique with two materials (i.e.,
             Cu and Al). After validation, the proposed technique was
             applied to measure spectra from the clinical system across a
             range of angular trajectories [-15°, 15°] and spectrum
             settings (80, 100, 120, 140 kVp).At 140 kVp, the proposed
             technique was comparable to the conventional technique in
             terms of the mean energy difference (MED, -0.29 keV) and the
             normalized root mean square difference (NRMSD, 0.84%) from
             the comparison standard compared to 0.64 keV and 1.56%,
             respectively, with the conventional technique. The average
             absolute MEDs and NRMSDs across kVp settings and angular
             trajectories were less than 0.61 keV and 3.41%,
             respectively, which indicates a high level of estimation
             accuracy and stability.An angle-dependent estimation
             technique of CT x-ray spectra from rotational transmission
             measurements was proposed. Compared with the conventional
             technique, the proposed method simplifies the measurement
             procedures and enables incident spectral estimation for a
             wide range of angular trajectories. The proposed technique
             is suitable for rigorous research objectives as well as
             routine clinical quality control procedures.},
   Doi = {10.1118/1.4876380},
   Key = {fds269208}
}

@article{fds324807,
   Author = {Nelson, J and Christianson, O and Samei, E},
   Title = {SU-C-9A-02: Structured Noise Index as An Automated Quality
             Control for Nuclear Medicine: A Two Year
             Experience.},
   Journal = {Medical physics},
   Volume = {41},
   Number = {6},
   Pages = {104},
   Year = {2014},
   Month = {June},
   url = {http://dx.doi.org/10.1118/1.4887843},
   Abstract = {Flood-field uniformity evaluation is an essential element in
             the assessment of nuclear medicine (NM) gamma cameras. It
             serves as the central element of the quality control (QC)
             program, acquired and analyzed on a daily basis prior to
             clinical imaging. Uniformity images are traditionally
             analyzed using pixel value-based metrics which often fail to
             capture subtle structure and patterns caused by changes in
             gamma camera performance requiring additional visual
             inspection which is subjective and time demanding. The goal
             of this project was to develop and implement a robust QC
             metrology for NM that is effective in identifying
             non-uniformity issues, reporting issues in a timely manner
             for efficient correction prior to clinical involvement, all
             incorporated into an automated effortless workflow, and to
             characterize the program over a two year period.A new
             quantitative uniformity analysis metric was developed based
             on 2D noise power spectrum metrology and confirmed based on
             expert observer visual analysis. The metric, termed
             Structured Noise Index (SNI) was then integrated into an
             automated program to analyze, archive, and report on daily
             NM QC uniformity images. The effectiveness of the program
             was evaluated over a period of 2 years.The SNI metric
             successfully identified visually apparent non-uniformities
             overlooked by the pixel valuebased analysis methods.
             Implementation of the program has resulted in nonuniformity
             identification in about 12% of daily flood images. In
             addition, due to the vigilance of staff response, the
             percentage of days exceeding trigger value shows a decline
             over time.The SNI provides a robust quantification of the NM
             performance of gamma camera uniformity. It operates
             seamlessly across a fleet of multiple camera models. The
             automated process provides effective workflow within the NM
             spectra between physicist, technologist, and clinical
             engineer. The reliability of this process has made it the
             preferred platform for NM uniformity analysis.},
   Doi = {10.1118/1.4887843},
   Key = {fds324807}
}

@article{fds324468,
   Author = {Winslow, J and Wilson, J and Christianson, O and Samei,
             E},
   Title = {WE-D-18A-02: Performance Evaluation of Automatic Exposure
             Control (AEC) Across 12 Clinical CT Systems.},
   Journal = {Medical physics},
   Volume = {41},
   Number = {6},
   Pages = {498},
   Year = {2014},
   Month = {June},
   url = {http://dx.doi.org/10.1118/1.4889411},
   Abstract = {Automatic exposure control (AEC) is not typically evaluated
             or monitored in CT quality assurance programs. The purpose
             of this study was to develop/evaluate a new AEC testing
             platform for the clinical physics program at our
             institution, and characterize AEC performance across
             different CT systems.The Mercury Phantom comprises three
             tapered and four uniform regions of polyethylene(16, 23, 30,
             and 37 cm in diameter); each region includes four inserts:
             air, Polystyrene, Acrylic, and Teflon. The phantom was
             imaged using AEC and a fixed tube current technique across
             12 clinical CT scanners. Those included five Siemens Somatom
             Definition Flash, four GE Discovery CT750HD, and three GE
             Lightspeed VCT systems. A custom MATLAB software package
             provided MTF, NPS, and detectability indices for each
             diameter section of the phantom. Detectability indices were
             used to evaluate the relationship between AEC setting,
             patient size, and image quality. The magnitude of the power
             of a best fit exponential curve to the detectability indices
             and phantom diameter was used as a measure of AEC strength.
             Results were compared within/across scanner models, and as
             baseline values for comparison with future system
             performance testing.For each scanner model, the percent
             difference in expected image quality and AEC setting was
             under 3%(+/-2%). The average decrease in detectability
             between the small and large diameter phantom sections for
             the Siemens Flash, GE CT750, and GE VCT was 99%(+/-10%),
             42%(+/-25%), and 33%(+/-41%), respectively. The value
             signifying AEC strength was 0.051(+/-13%), 0.019(+/-18%),
             and 0.018(+/-26%), for the Siemens Flash, GE CT750, and GE
             VCT models, respectively.This study demonstrated a practical
             approach to test the AEC performance of clinical CT systems
             at a large academic medical center. The quantification and
             evaluation of AEC performance should be included in
             acceptance testing and in annual physics testing of clinical
             CT systems.},
   Doi = {10.1118/1.4889411},
   Key = {fds324468}
}

@article{fds324469,
   Author = {Wells, J and Wilson, J and Zhang, Y and Samei, E and Ravin,
             CE},
   Title = {SU-E-I-94: Automated Image Quality Assessment of
             Radiographic Systems Using An Anthropomorphic
             Phantom.},
   Journal = {Medical physics},
   Volume = {41},
   Number = {6},
   Pages = {152},
   Year = {2014},
   Month = {June},
   url = {http://dx.doi.org/10.1118/1.4888044},
   Abstract = {In a large, academic medical center, consistent radiographic
             imaging performance is difficult to routinely monitor and
             maintain, especially for a fleet consisting of multiple
             vendors, models, software versions, and numerous imaging
             protocols. Thus, an automated image quality control
             methodology has been implemented using routine image quality
             assessment with a physical, stylized anthropomorphic chest
             phantom.The "Duke" Phantom (Digital Phantom 07-646,
             Supertech, Elkhart, IN) was imaged twice on each of 13
             radiographic units from a variety of vendors at 13 primary
             care clinics. The first acquisition used the clinical PA
             chest protocol to acquire the post-processed "FOR
             PRESENTATION" image. The second image was acquired without
             an antiscatter grid followed by collection of the "FOR
             PROCESSING" image. Manual CNR measurements were made from
             the largest and thickest contrast-detail inserts in the
             lung, heart, and abdominal regions of the phantom in each
             image. An automated image registration algorithm was used to
             estimate the CNR of the same insert using similar ROIs.
             Automated measurements were then compared to the manual
             measurements.Automatic and manual CNR measurements obtained
             from "FOR PRESENTATION" images had average percent
             differences of 0.42%±5.18%, -3.44%±4.85%, and 1.04%±3.15%
             in the lung, heart, and abdominal regions, respectively;
             measurements obtained from "FOR PROCESSING" images had
             average percent differences of -0.63%±6.66%, -0.97%±3.92%,
             and -0.53%±4.18%, respectively. The maximum absolute
             difference in CNR was 15.78%, 10.89%, and 8.73% in the
             respective regions. In addition to CNR assessment of the
             largest and thickest contrast-detail inserts, the automated
             method also provided CNR estimates for all 75
             contrast-detail inserts in each phantom image.Automated
             analysis of a radiographic phantom has been shown to be a
             fast, robust, and objective means for assessing radiographic
             image quality. The method reduces the burden of manual
             measurements and provides a means by which to monitor and
             compare radiographic system performance.},
   Doi = {10.1118/1.4888044},
   Key = {fds324469}
}

@article{fds324808,
   Author = {Winslow, J and Christianson, O and Samei, E},
   Title = {SU-F-18C-07: Automated CT QC Program with Analytics,
             Archival, and Notification Capabilities.},
   Journal = {Medical physics},
   Volume = {41},
   Number = {6},
   Pages = {404},
   Year = {2014},
   Month = {June},
   url = {http://dx.doi.org/10.1118/1.4889092},
   Abstract = {Tracking metrics over time is a well-established means of
             establishing a quality control program. The number of
             metrics followed and testing frequency is limited by
             available resources. Automating the image analysis and data
             archival of a QC program enables objective and efficient
             tracking of performance metrics. The purpose of this study
             was to develop such a QC method and to assess its utility at
             a large clinical facility.The QC program at our institution
             is based on the acquisition of daily water-phantom scans,
             and biweekly ACR-phantom scans for each CT system. We
             developed a QC program to analyze these data. The QC
             software operates on the images sent directly to our server.
             The relevant information from DICOM headers was extracted,
             data analyzed, and a database was populated. The
             measurements performed on the waterphantom included water
             CT-number, uniformity, noise, and artifact. The measurements
             performed on the ACR-phantom included the MTF, NPS,
             detectability, artifact, uniformity, CNR, and the CT-numbers
             for water, polyethylene, bone, air, and acrylic. Email
             notifications and criteria limits were directly based upon
             ACR accreditation requirements and developing threshold
             values.Across ten clinical CT scanners, the daily water
             CT-number was -0.2+/-1.4 HU(mean+/-standard deviation). The
             corresponding numbers for 10%MTF, uniformity, CNR squared
             normalized to CTDI, and detectability squared normalized to
             CTDI were 0.69+/-0.01 (1/mm), 0.93+/-0.29, 0.06+/-0.02
             (1/mGy), and 3.3+/-0.7 (1/mGy), respectively. For all
             ACR-phantom inserts, the largest standard deviation for any
             individual scanner was 1.9 HU. Artifact analysis triggers
             successfully identified problematic images.Automating image
             analysis allows one to frequently track meaningful metrics
             that would be impractical to follow otherwise. System
             inconsistencies are more likely to be identified and
             corrected earlier. Much tighter system specific criteria
             limits are possible.},
   Doi = {10.1118/1.4889092},
   Key = {fds324808}
}

@article{fds324809,
   Author = {Samei, E and Hangiandreou, N and Nelson, J},
   Title = {TH-E-9A-01: Medical Physics 1.0 to 2.0, Session 4: Computed
             Tomography, Ultrasound and Nuclear Medicine.},
   Journal = {Medical physics},
   Volume = {41},
   Number = {6},
   Pages = {574-575},
   Year = {2014},
   Month = {June},
   url = {http://dx.doi.org/10.1118/1.4889842},
   Abstract = {Medical Physics 2.0 is a bold vision for an existential
             transition of clinical imaging physics in face of the new
             realities of value-based and evidencebased medicine,
             comparative effectiveness, and meaningful use. It speaks to
             how clinical imaging physics can expand beyond traditional
             insular models of inspection and acceptance testing,
             oriented toward compliance, towards team-based models of
             operational engagement, prospective definition and assurance
             of effective use, and retrospective evaluation of clinical
             performance. Organized into four sessions of the AAPM, this
             particular session focuses on three specific modalities as
             outlined below. CT 2.0: CT has been undergoing a dramatic
             transition in the last few decades. While the changes in the
             technology merits discussions of their own, an important
             question is how clinical medical physicists are expected to
             effectively engage with the new realities of CT technology
             and practice. Consistent with the upcoming paradigm of
             Medical Physics 2.0, this CT presentation aims to provide
             definitions and demonstration of the components of the new
             clinical medical physics practice pertaining CT. The topics
             covered include physics metrics and analytics that aim to
             provide higher order clinicallyrelevant quantification of
             system performance as pertains to new (and not so new)
             technologies. That will include the new radiation and dose
             metrics (SSDE, organ dose, risk indices), image quality
             metrology (MTF/NPS/d'), task-based phantoms, and the effect
             of patient size. That will follow with a discussion of the
             testing implication of new CT hardware (detectors, tubes),
             acquisition methods (innovative helical geometries, AEC,
             wide beam CT, dual energy, inverse geometry, application
             specialties), and image processing and analysis (iterative
             reconstructions, quantitative CT, advanced renditions). The
             presentation will conclude with a discussion of clinical and
             operational aspects of Medical Physics 2.0 including
             training and communication, use optimization (dose and
             technique factors), automated analysis and data management
             (automated QC methods, protocol tracking, dose monitoring,
             issue tracking), and meaningful QC considerations. US 2.0:
             Ultrasound imaging is evolving at a rapid pace, adding new
             imaging functions and modes that continue to enhance its
             clinical utility and benefits to patients. The ultrasound
             talk will look ahead 10-15 years and consider how medical
             physicists can bring maximal value to the clinical
             ultrasound practices of the future. The roles of physics in
             accreditation and regulatory compliance, image quality and
             exam optimization, clinical innovation, and education of
             staff and trainees will all be considered. A detailed
             examination of expected technology evolution and impact on
             image quality metrics will be presented. Clinical
             implementation of comprehensive physics services will also
             be discussed. Nuclear Medicine 2.0: Although the basic
             science of nuclear imaging has remained relatively unchanged
             since its inception, advances in instrumentation continue to
             advance the field into new territories. With a great number
             of these advances occurring over the past decade, the role
             and testing strategies of clinical nuclear medicine
             physicists must evolve in parallel. The Nuclear Medicine 2.0
             presentation is designed to highlight some of the recent
             advances from a clinical medical physicist perspective and
             provide ideas and motivation for designing better evaluation
             strategies. Topics include improvement of traditional
             physics metrics and analytics, testing implications of
             hybrid imaging and advanced detector technologies, and
             strategies for effective implementation into the clinic.1.
             Become familiar with new physics metrics and analytics in
             nuclear medicine, CT, and ultrasound. 2. To become familiar
             with the major new developments of clinical physics support.
             3. To understand the physics testing implications of new
             technologies, hardware, software, and applications. 4.
             Identify approaches for implementing comprehensive medical
             physics services in future imaging practices.},
   Doi = {10.1118/1.4889842},
   Key = {fds324809}
}

@article{fds324810,
   Author = {Samei, E and Pfeiffer, D and Frey, G and Krupinski, E and Pizzutiello,
             R and Carson, P and Mahesh, M and Hangiandreou, N and Jordan, D and Dixon,
             R},
   Title = {TU-C-18C-01: Medical Physics 1.0 to 2.0: Introduction and
             Panel Discussion.},
   Journal = {Medical physics},
   Volume = {41},
   Number = {6},
   Pages = {461-462},
   Year = {2014},
   Month = {June},
   url = {http://dx.doi.org/10.1118/1.4889289},
   Abstract = {Medical Physics 2.0, a new frontier in clinical imaging
             physics: Diagnostic imaging has always been a technological
             highlight of modern medicine. Imaging systems, with their
             ever-expanding advancement in terms of technology and
             application, increasingly require skilled expertise to
             understand the delicacy of their operation, monitor their
             performance, design their effective use, and ensure their
             overall quality and safety, scientifically and in
             quantitative terms. Physicists can play a crucial role in
             that process. But that role has largely remained a severely
             untapped resource. Many imaging centers fail to appreciate
             this potential, with medical physics groups either
             nonexistent or highly understaffed and their services poorly
             integrated into the patient care process. As a field, we
             have yet to define and enact how the clinical physicist can
             engage as an active, effective, and integral member of the
             clinical team, and how the services that she/he provides can
             be financially accounted for. Physicists do and will always
             contribute to research and development. However, their
             indispensible contribution to clinical imaging operations is
             something that has not been adequately established. That, in
             conjunction with new realities of healthcare practice,
             indicates a growing need to establish an updated approach to
             clinical medical imaging physics. This presentation aims to
             describe a vision as how clinical imaging physics can expand
             beyond traditional insular models of inspection and
             acceptance testing, oriented toward compliance, towards
             team-based models of operational engagement addressing
             topics such as new non-classical challenges of new
             technologies, quantitative imaging, and operational
             optimization. The Medical Physics 2.0 paradigm extends
             clinical medical physics from isolated characterization of
             inherent properties of the equipment to effective use of the
             equipment and to retrospective evaluation of clinical
             performance. This is an existential transition of the field
             that speaks to the new paradigms of value-based and
             evidence-based medicine, comparative effectiveness, and
             meaningful use. The panel discussion that follows includes
             prominent practitioners, thinkers, and leaders that would
             lead the discussion on how Medical Physics 2.0 can be
             actualized. Topics of discussion will include the
             administrative, financial, regulatory, and accreditation
             requirements of the new paradigm, effective models of
             practice, and the steps that we need to take to make MP 2.0
             a reality.1. To understand the new paradigm of clinical
             medical physics practice extending from traditional insular
             models of compliance towards teambased models of operational
             engagement. 2. To understand how clinical physics can most
             effectively contribute to clinical care. 3. Learn to
             identify strengths and weaknesses in studies designed to
             measure the effect of low doses of ionizing radiation 4. To
             recognize the impediments to Medical Physics 2.0
             paradigm.},
   Doi = {10.1118/1.4889289},
   Key = {fds324810}
}

@article{fds324811,
   Author = {Christianson, O and Winslow, J and Samei, E},
   Title = {TH-C-18A-06: Combined CT Image Quality and Radiation Dose
             Monitoring Program Based On Patient Data to Assess
             Consistency of Clinical Imaging Across Scanner
             Models.},
   Journal = {Medical physics},
   Volume = {41},
   Number = {6},
   Pages = {558},
   Year = {2014},
   Month = {June},
   url = {http://dx.doi.org/10.1118/1.4889630},
   Abstract = {One of the principal challenges of clinical imaging is to
             achieve an ideal balance between image quality and radiation
             dose across multiple CT models. The number of scanners and
             protocols at large medical centers necessitates an automated
             quality assurance program to facilitate this objective.
             Therefore, the goal of this work was to implement an
             automated CT image quality and radiation dose monitoring
             program based on actual patient data and to use this program
             to assess consistency of protocols across CT scanner
             models.Patient CT scans are routed to a HIPPA compliant
             quality assurance server. CTDI, extracted using optical
             character recognition, and patient size, measured from the
             localizers, are used to calculate SSDE. A previously
             validated noise measurement algorithm determines the noise
             in uniform areas of the image across the scanned anatomy to
             generate a global noise level (GNL). Using this program,
             2358 abdominopelvic scans acquired on three commercial CT
             scanners were analyzed. Median SSDE and GNL were compared
             across scanner models and trends in SSDE and GNL with
             patient size were used to determine the impact of differing
             automatic exposure control (AEC) algorithms.There was a
             significant difference in both SSDE and GNL across scanner
             models (9-33% and 15-35% for SSDE and GNL, respectively).
             Adjusting all protocols to achieve the same image noise
             would reduce patient dose by 27-45% depending on scanner
             model. Additionally, differences in AEC methodologies across
             vendors resulted in disparate relationships of SSDE and GNL
             with patient size.The difference in noise across scanner
             models indicates that protocols are not optimally matched to
             achieve consistent image quality. Our results indicated
             substantial possibility for dose reduction while achieving
             more consistent image appearance. Finally, the difference in
             AEC methodologies suggests the need for size-specific CT
             protocols to minimize variability in image quality across CT
             vendors.},
   Doi = {10.1118/1.4889630},
   Key = {fds324811}
}

@article{fds324812,
   Author = {Sahbaee, P and Samei, E and Segars, W},
   Title = {SU-C-12A-03: The Impact of Contrast Medium On Radiation Dose
             in CT: A Systematic Evaluation Across 58 Patient
             Models.},
   Journal = {Medical physics},
   Volume = {41},
   Number = {6},
   Pages = {106},
   Year = {2014},
   Month = {June},
   url = {http://dx.doi.org/10.1118/1.4887851},
   Abstract = {To assess the effect of contrast medium on radiation dose as
             a function of time via Monte Carlo simulation from the liver
             CT scan across a library of 5D XCAT models METHODS: A
             validated Monte Carlo simulation package (PENELOPE) was
             employed to model a CT system (LightSpeed 64 VCT, GE
             Healthcare). The radiation dose was estimated from a common
             abdomen CT examination. The dose estimation was performed on
             a library of adult extended cardiac-torso (5D XCAT) phantoms
             (35 male, 23 female, mean age 51.5 years, mean weight 80.2
             kg). The 5D XCAT models were created based on
             patient-specific iodine concentration-time results from our
             computational contrast medium propagation model for
             different intravenous injection protocols. To enable a
             dynamic estimation of radiation dose, each organ in the
             model was assigned to its own time-concentration curve via
             the PENELOPE package, material.exe. Using the Monte Carlo,
             for each scan time point after the injection, 80 million
             photons were initiated and tracked through the phantoms.
             Finally, the dose to the liver was tallied from the
             deposited energy.Monte Carlo simulation results of radiation
             dose delivered to the liver from the XCAT models indicated
             up to 30% increase in dose for different time after the
             administration of contrast medium.The contrast enhancement
             is employed in over 60% of imaging modalities, which not
             only remarkably affects the CT image quality, but also
             increases the radiation dose by as much as 70%. The
             postinjection multiple acquisition in several enhanced CT
             protocols, makes the radiation dose increment through the
             use of contrast medium, an inevitable factor in optimization
             of these protocols. The relationship between radiation dose
             and injected contrast medium as a function of time studied
             in this work allows optimization of contrast administration
             for vulnerable individuals.},
   Doi = {10.1118/1.4887851},
   Key = {fds324812}
}

@article{fds324813,
   Author = {Chen, G and Pan, X and Stayman, J and Samei, E},
   Title = {MO-C-18A-01: Advances in Model-Based 3D Image
             Reconstruction.},
   Journal = {Medical physics},
   Volume = {41},
   Number = {6},
   Pages = {416-417},
   Year = {2014},
   Month = {June},
   url = {http://dx.doi.org/10.1118/1.4889136},
   Abstract = {Recent years have seen the emergence of CT image
             reconstruction techniques that exploit physical models of
             the imaging system, photon statistics, and even the patient
             to achieve improved 3D image quality and/or reduction of
             radiation dose. With numerous advantages in comparison to
             conventional 3D filtered backprojection, such techniques
             bring a variety of challenges as well, including: a
             demanding computational load associated with sophisticated
             forward models and iterative optimization methods;
             nonlinearity and nonstationarity in image quality
             characteristics; a complex dependency on multiple free
             parameters; and the need to understand how best to
             incorporate prior information (including patient-specific
             prior images) within the reconstruction process. The
             advantages, however, are even greater - for example:
             improved image quality; reduced dose; robustness to noise
             and artifacts; task-specific reconstruction protocols;
             suitability to novel CT imaging platforms and noncircular
             orbits; and incorporation of known characteristics of the
             imager and patient that are conventionally discarded. This
             symposium features experts in 3D image reconstruction, image
             quality assessment, and the translation of such methods to
             emerging clinical applications. Dr. Chen will address novel
             methods for the incorporation of prior information in 3D and
             4D CT reconstruction techniques. Dr. Pan will show recent
             advances in optimization-based reconstruction that enable
             potential reduction of dose and sampling requirements. Dr.
             Stayman will describe a "task-based imaging" approach that
             leverages models of the imaging system and patient in
             combination with a specification of the imaging task to
             optimize both the acquisition and reconstruction process.
             Dr. Samei will describe the development of methods for image
             quality assessment in such nonlinear reconstruction
             techniques and the use of these methods to characterize and
             optimize image quality and dose in a spectrum of clinical
             applications.1. Learn the general methodologies associated
             with model-based 3D image reconstruction. 2. Learn the
             potential advantages in image quality and dose associated
             with model-based image reconstruction. 3. Learn the
             challenges associated with computational load and image
             quality assessment for such reconstruction methods. 4. Learn
             how imaging task can be incorporated as a means to drive
             optimal image acquisition and reconstruction techniques. 5.
             Learn how model-based reconstruction methods can incorporate
             prior information to improve image quality, ease sampling
             requirements, and reduce dose.},
   Doi = {10.1118/1.4889136},
   Key = {fds324813}
}

@article{fds324814,
   Author = {Winslow, J and Hurwitz, L and Christianson, O and Samei,
             E},
   Title = {SU-E-I-91: Reproducibility in Prescribed Dose in AEC CT
             Scans Due to Table Height, Patient Size, and Localizer
             Acquisition Order.},
   Journal = {Medical physics},
   Volume = {41},
   Number = {6},
   Pages = {151},
   Year = {2014},
   Month = {June},
   url = {http://dx.doi.org/10.1118/1.4888041},
   Abstract = {In CT scanners, the automatic exposure control (AEC) tube
             current prescription depends on the acquired prescan
             localizer image(s). The purpose of this study was to
             quantify the effect that table height, patient size, and
             localizer acquisition order may have on the reproducibility
             in prescribed dose.Three phantoms were used for this study:
             the Mercury Phantom (comprises three tapered and four
             uniform regions of polyethylene 16, 23, 30, and 37 cm in
             diameter), acrylic sheets, and an adult anthropomorphic
             phantom. Phantoms were positioned per clinical protocol by
             our chief CT technologist or broader symmetry. Using a GE
             Discovery CT750HD scanner, a lateral (LAT) and
             posterior-anterior (PA) localizer was acquired for each
             phantom at different table heights. AEC scan acquisitions
             were prescribed for each combination of phantom, localizer
             orientation, and table height; the displayed volume CTDI was
             recorded for each. Results were analyzed versus table
             height.For the two largest Mercury Phantom section scans
             based on the PA localizer, the percent change in volume CTDI
             from ideal were at least 20% lower and 35% greater for table
             heights 4 cm above and 4 cm below proper centering,
             respectively. For scans based on the LAT localizer, the
             percent change in volume CTDI from ideal were no greater
             than 12% different for 4 cm differences in table height. The
             properly centered PA and LAT localizer-based volume CTDI
             values were within 13% of each other.Since uncertainty in
             vertical patient positioning is inherently greater than
             lateral positioning and because the variability in dose
             exceeds any dose penalties incurred, the LAT localizer
             should be used to precisely and reproducibly deliver the
             intended amount of radiation prescribed by CT protocols. CT
             protocols can be adjusted to minimize the expected change in
             average patient dose.},
   Doi = {10.1118/1.4888041},
   Key = {fds324814}
}

@article{fds324815,
   Author = {Sahbaee, P and Samei, E and Segars, W},
   Title = {MO-E-17A-02: Incorporation of Contrast Medium Dynamics in
             Anthropomorphic Phantoms: The Advent of 5D XCAT
             Models.},
   Journal = {Medical physics},
   Volume = {41},
   Number = {6},
   Pages = {424},
   Year = {2014},
   Month = {June},
   url = {http://dx.doi.org/10.1118/1.4889154},
   Abstract = {To develop a unique method to incorporate the dynamics of
             contrast-medium propagation into the anthropomorphic
             phantom, to generate a five-dimensional (5D) patient model
             for multimodality imaging studies.A compartmental model of
             blood circulation network within the body was embodied into
             an extended cardiac-torso (4D-XCAT) patient model. To do so,
             a computational physiologic model of the human
             cardiovascular system was developed which includes a series
             of compartments representing heart, vessels, and organs.
             Patient-specific cardiac output and blood volume were used
             as inputs influenced by the weight, height, age, and gender
             of the patient's model. For a given injection protocol and
             given XCAT model, the contrast-medium transmission within
             the body was described by a series of mass balance
             differential equations, the solutions to which provided the
             contrast enhancement-time curves for each organ; thereby
             defining the tissue materials including the contrastmedium
             within the XCAT model. A library of time-dependent organ
             materials was then defined. Each organ in each voxelized
             4D-XCAT phantom was assigned to a corresponding time-varying
             material to create the 5D-XCAT phantom in which the fifth
             dimension is blood/contrast-medium within the temporal
             domain.The model effectively predicts the time-varying
             concentration behavior of various contrast-medium
             administration in each organ for different patient models as
             function of patient size (weight/height) and different
             injection protocol factors (injection rate and pattern,
             iodine concentration or volume). The contrast enhanced XCAT
             patient models was developed based on the concentration of
             iodine as a function of time after injection.Majority of
             medical imaging systems take advantage of contrast-medium
             administration in terms of better image quality, the effect
             of which was ignored in previous optimization studies. The
             study enables a comprehensive optimization of contrast
             administration both in terms of image quality and radiation
             dose, and can be used in different modalities such as CT,
             MRI, and ultrasound.},
   Doi = {10.1118/1.4889154},
   Key = {fds324815}
}

@article{fds324816,
   Author = {Rehani, M and Samei, E and Morgan, W and Shore, R and Goske,
             M},
   Title = {MO-C-18C-01: Radiation Risks at Level of Few CT Scans: How
             Real?- Science to Practice.},
   Journal = {Medical physics},
   Volume = {41},
   Number = {6},
   Pages = {417},
   Year = {2014},
   Month = {June},
   url = {http://dx.doi.org/10.1118/1.4889137},
   Abstract = {There are controversies surrounding radiation effects in
             human population in the range of radiation doses encountered
             by patients resulting from one to several CT scans. While it
             is understandable why the effects from low levels of
             diagnostic radiation are controversial, the situation is
             complicated by the media which may distort the known facts.
             There is need to understand the state of science regarding
             low-level radiation effects and also to understand how to
             communicate the potential risk with patients, the public and
             media. This session will seek to come to a consensus in
             order to speak with one voice to the media and the public.
             This session will review radiation effects known so far from
             a variety of exposed groups since the nuclear holocaust,
             provide clarification where effects are certain and where
             they are not, at what level extrapolation is the only way
             and at what level there is weak but agreeable acceptance. We
             will depict where and why there is agreement among
             organizations responsible for studying radiation effects,
             and how to deal with situations where effects are uncertain.
             Specific focus on radiation effects in children will be
             provided.Finally, the session will attempt to bridge the
             communication gap from the science to how to be an effective
             communicator with patients, parents, and media about
             ionizing radiation.1. To have a clear understanding about
             certainties and uncertainties of radiation effects at the
             level of a few CT scans 2. To understand the results and
             limitations from 3 major pediatric CT scientific studies on
             childhood exposures published recently. 3. To understand
             successful strategies used in risk communication.},
   Doi = {10.1118/1.4889137},
   Key = {fds324816}
}

@article{fds324817,
   Author = {Smitherman, C and Chen, B and Samei, E},
   Title = {SU-F-18C-01: Minimum Detectability Analysis for
             Comprehensive Sized Based Optimization of Image Quality and
             Radiation Dose Across CT Protocols.},
   Journal = {Medical physics},
   Volume = {41},
   Number = {6},
   Pages = {402-403},
   Year = {2014},
   Month = {June},
   url = {http://dx.doi.org/10.1118/1.4889085},
   Abstract = {This work involved a comprehensive modeling of task-based
             performance of CT across a wide range of protocols. The
             approach was used for optimization and consistency of dose
             and image quality within a large multi-vendor clinical
             facility.150 adult protocols from the Duke University
             Medical Center were grouped into sub-protocols with similar
             acquisition characteristics. A size based image quality
             phantom (Duke Mercury Phantom) was imaged using these
             sub-protocols for a range of clinically relevant doses on
             two CT manufacturer platforms (Siemens, GE). The images were
             analyzed to extract task-based image quality metrics such as
             the Task Transfer Function (TTF), Noise Power Spectrum, and
             Az based on designer nodule task functions. The data were
             analyzed in terms of the detectability of a lesion
             size/contrast as a function of dose, patient size, and
             protocol. A graphical user interface (GUI) was developed to
             predict image quality and dose to achieve a minimum level of
             detectability.Image quality trends with variations in dose,
             patient size, and lesion contrast/size were evaluated and
             calculated data behaved as predicted. The GUI proved
             effective to predict the Az values representing radiologist
             confidence for a targeted lesion, patient size, and dose. As
             an example, an abdomen pelvis exam for the GE scanner, with
             a task size/contrast of 5-mm/50-HU, and an Az of 0.9
             requires a dose of 4.0, 8.9, and 16.9 mGy for patient
             diameters of 25, 30, and 35 cm, respectively. For a constant
             patient diameter of 30 cm, the minimum detected lesion size
             at those dose levels would be 8.4, 5, and 3.9 mm,
             respectively.The designed CT protocol optimization platform
             can be used to evaluate minimum detectability across dose
             levels and patient diameters. The method can be used to
             improve individual protocols as well as to improve protocol
             consistency across CT scanners.},
   Doi = {10.1118/1.4889085},
   Key = {fds324817}
}

@article{fds269207,
   Author = {Ikejimba, LC and Kiarashi, N and Ghate, SV and Samei, E and Lo,
             JY},
   Title = {Task-based strategy for optimized contrast enhanced breast
             imaging: Analysis of six imaging techniques for mammography
             and tomosynthesis},
   Journal = {Medical physics},
   Volume = {41},
   Number = {6Part1},
   Pages = {061908-061908},
   Year = {2014},
   Month = {May},
   ISSN = {0094-2405},
   url = {http://dx.doi.org/10.1118/1.4873317},
   Doi = {10.1118/1.4873317},
   Key = {fds269207}
}

@article{fds269210,
   Author = {Lin, Y and Samei, E},
   Title = {A fast poly-energetic iterative FBP algorithm.},
   Journal = {Physics in Medicine and Biology},
   Volume = {59},
   Number = {7},
   Pages = {1655-1678},
   Year = {2014},
   Month = {April},
   ISSN = {0031-9155},
   url = {http://dx.doi.org/10.1088/0031-9155/59/7/1655},
   Abstract = {The beam hardening (BH) effect can influence medical
             interpretations in two notable ways. First, high attenuation
             materials, such as bones, can induce strong artifacts, which
             severely deteriorate the image quality. Second, voxel values
             can significantly deviate from the real values, which can
             lead to unreliable quantitative evaluation results. Some
             iterative methods have been proposed to eliminate the BH
             effect, but they cannot be widely applied for clinical
             practice because of the slow computational speed. The
             purpose of this study was to develop a new fast and
             practical poly-energetic iterative filtered backward
             projection algorithm (piFBP). The piFBP is composed of a
             novel poly-energetic forward projection process and a robust
             FBP-type backward updating process. In the forward
             projection process, an adaptive base material decomposition
             method is presented, based on which diverse body tissues
             (e.g., lung, fat, breast, soft tissue, and bone) and metal
             implants can be incorporated to accurately evaluate
             poly-energetic forward projections. In the backward updating
             process, one robust and fast FBP-type backward updating
             equation with a smoothing kernel is introduced to avoid the
             noise accumulation in the iteration process and to improve
             the convergence properties. Two phantoms were designed to
             quantitatively validate our piFBP algorithm in terms of the
             beam hardening index (BIdx) and the noise index (NIdx). The
             simulation results showed that piFBP possessed fast
             convergence speed, as the images could be reconstructed
             within four iterations. The variation range of the BIdx's of
             various tissues across phantom size and spectrum were
             reduced from [-7.5, 17.5] for FBP to [-0.1, 0.1] for piFBP
             while the NIdx's were maintained in the same low level
             (about [0.3, 1.7]). When a metal implant presented in a
             complex phantom, piFBP still had excellent reconstruction
             performance, as the variation range of the BIdx's of body
             tissues were reduced from [-2.9, 15.9] for FBP to [-0.3,
             0.3] for piFBP and the magnitude of the BIdx of the metal
             implant was reduced from 23.3 to 1.3. The proposed algorithm
             piFBP can effectively eliminate beam hardening artifacts
             caused by bones, greatly reduce metal artifacts caused by
             metal implants, and quantitatively reconstruct accurate
             images with poly-energetic spectrum. Its fast reconstruction
             speed and excellent performance make it ready for clinical
             applications on the current single spectrum CT
             scanners.},
   Doi = {10.1088/0031-9155/59/7/1655},
   Key = {fds269210}
}

@article{fds269211,
   Author = {Norris, H and Zhang, Y and Bond, J and Sturgeon, GM and Minhas, A and Tward, DJ and Ratnanather, JT and Miller, MI and Frush, D and Samei, E and Segars, WP},
   Title = {A set of 4D pediatric XCAT reference phantoms for
             multimodality research.},
   Journal = {Medical physics},
   Volume = {41},
   Number = {3},
   Pages = {033701},
   Year = {2014},
   Month = {March},
   ISSN = {0094-2405},
   url = {http://dx.doi.org/10.1118/1.4864238},
   Abstract = {The authors previously developed an adult population of 4D
             extended cardiac-torso (XCAT) phantoms for multimodality
             imaging research. In this work, the authors develop a
             reference set of 4D pediatric XCAT phantoms consisting of
             male and female anatomies at ages of newborn, 1, 5, 10, and
             15 years. These models will serve as the foundation from
             which the authors will create a vast population of pediatric
             phantoms for optimizing pediatric CT imaging protocols.Each
             phantom was based on a unique set of CT data from a normal
             patient obtained from the Duke University database. The
             datasets were selected to best match the reference values
             for height and weight for the different ages and genders
             according to ICRP Publication 89. The major organs and
             structures were segmented from the CT data and used to
             create an initial pediatric model defined using nonuniform
             rational B-spline surfaces. The CT data covered the entire
             torso and part of the head. To complete the body, the
             authors manually added on the top of the head and the arms
             and legs using scaled versions of the XCAT adult models or
             additional models created from cadaver data. A multichannel
             large deformation diffeomorphic metric mapping algorithm was
             then used to calculate the transform from a template XCAT
             phantom (male or female 50th percentile adult) to the target
             pediatric model. The transform was applied to the template
             XCAT to fill in any unsegmented structures within the target
             phantom and to implement the 4D cardiac and respiratory
             models in the new anatomy. The masses of the organs in each
             phantom were matched to the reference values given in ICRP
             Publication 89. The new reference models were checked for
             anatomical accuracy via visual inspection.The authors
             created a set of ten pediatric reference phantoms that have
             the same level of detail and functionality as the original
             XCAT phantom adults. Each consists of thousands of
             anatomical structures and includes parameterized models for
             the cardiac and respiratory motions. Based on patient data,
             the phantoms capture the anatomic variations of childhood,
             such as the development of bone in the skull, pelvis, and
             long bones, and the growth of the vertebrae and organs. The
             phantoms can be combined with existing simulation packages
             to generate realistic pediatric imaging data from different
             modalities.The development of patient-derived pediatric
             computational phantoms is useful in providing variable
             anatomies for simulation. Future work will expand this
             ten-phantom base to a host of pediatric phantoms
             representative of the public at large. This can provide a
             means to evaluate and improve pediatric imaging devices and
             to optimize CT protocols in terms of image quality and
             radiation dose.},
   Doi = {10.1118/1.4864238},
   Key = {fds269211}
}

@article{fds269212,
   Author = {Lin, Y and Samei, E},
   Title = {An efficient polyenergetic SART (pSART) reconstruction
             algorithm for quantitative myocardial CT
             perfusion.},
   Journal = {Medical physics},
   Volume = {41},
   Number = {2},
   Pages = {021911},
   Year = {2014},
   Month = {February},
   ISSN = {0094-2405},
   url = {http://dx.doi.org/10.1118/1.4863481},
   Abstract = {In quantitative myocardial CT perfusion imaging, beam
             hardening effect due to dense bone and high concentration
             iodinated contrast agent can result in visible artifacts and
             inaccurate CT numbers. In this paper, an efficient
             polyenergetic Simultaneous Algebraic Reconstruction
             Technique (pSART) was presented to eliminate the beam
             hardening artifacts and to improve the CT quantitative
             imaging ability.Our algorithm made three a priori
             assumptions: (1) the human body is composed of several base
             materials (e.g., fat, breast, soft tissue, bone, and
             iodine); (2) images can be coarsely segmented to two types
             of regions, i.e., nonbone regions and noniodine regions; and
             (3) each voxel can be decomposed into a mixture of two most
             suitable base materials according to its attenuation value
             and its corresponding region type information. Based on the
             above assumptions, energy-independent accumulated effective
             lengths of all base materials can be fast computed in the
             forward ray-tracing process and be used repeatedly to obtain
             accurate polyenergetic projections, with which a SART-based
             equation can correctly update each voxel in the backward
             projecting process to iteratively reconstruct artifact-free
             images. This approach effectively reduces the influence of
             polyenergetic x-ray sources and it further enables
             monoenergetic images to be reconstructed at any arbitrarily
             preselected target energies. A series of simulation tests
             were performed on a size-variable cylindrical phantom and a
             realistic anthropomorphic thorax phantom. In addition, a
             phantom experiment was also performed on a clinical CT
             scanner to further quantitatively validate the proposed
             algorithm.The simulations with the cylindrical phantom and
             the anthropomorphic thorax phantom showed that the proposed
             algorithm completely eliminated beam hardening artifacts and
             enabled quantitative imaging across different materials,
             phantom sizes, and spectra, as the absolute relative errors
             were reduced from [-7.5%, 12.1%] for SART to [-0.1%, 0.1%]
             for pSART. When using low kVp spectra and high reference
             energies, pSART also showed improved reconstruction
             efficiency in terms of convergence speed compared to the
             conventional SART algorithm. The phantom experiment on a
             clinical CT scanner indicated that the quantitative
             advantage of pSART is realizable in experimental CT
             acquisition, as the absolute relative errors across material
             inserts were less than 0.4%.By incorporatinga priori
             information (material attenuation coefficients, x-ray source
             spectrum, and region type information) into the
             reconstruction process, the proposed pSART algorithm could
             effectively eliminate beam hardening artifacts, reconstruct
             the accurate attenuation coefficients for precise
             quantitative imaging, and accelerate the reconstruction
             process.},
   Doi = {10.1118/1.4863481},
   Key = {fds269212}
}

@article{fds269213,
   Author = {Zhang, Y and Li, X and Segars, WP and Samei, E},
   Title = {Comparison of patient specific dose metrics between chest
             radiography, tomosynthesis, and CT for adult patients of
             wide ranging body habitus.},
   Journal = {Medical physics},
   Volume = {41},
   Number = {2},
   Pages = {023901},
   Year = {2014},
   Month = {February},
   ISSN = {0094-2405},
   url = {http://dx.doi.org/10.1118/1.4859315},
   Abstract = {Given the radiation concerns inherent to the x-ray
             modalities, accurately estimating the radiation doses that
             patients receive during different imaging modalities is
             crucial. This study estimated organ doses, effective doses,
             and risk indices for the three clinical chest x-ray imaging
             techniques (chest radiography, tomosynthesis, and CT) using
             59 anatomically variable voxelized phantoms and Monte Carlo
             simulation methods.A total of 59 computational
             anthropomorphic male and female extended cardiac-torso
             (XCAT) adult phantoms were used in this study. Organ doses
             and effective doses were estimated for a clinical
             radiography system with the capability of conducting chest
             radiography and tomosynthesis (Definium 8000, VolumeRAD, GE
             Healthcare) and a clinical CT system (LightSpeed VCT, GE
             Healthcare). A Monte Carlo dose simulation program
             (PENELOPE, version 2006, Universitat de Barcelona, Spain)
             was used to mimic these two clinical systems. The Duke
             University (Durham, NC) technique charts were used to
             determine the clinical techniques for the radiographic
             modalities. An exponential relationship between CTDIvol and
             patient diameter was used to determine the absolute dose
             values for CT. The simulations of the two clinical systems
             compute organ and tissue doses, which were then used to
             calculate effective dose and risk index. The calculation of
             the two dose metrics used the tissue weighting factors from
             ICRP Publication 103 and BEIR VII report.The average
             effective dose of the chest posteroanterior examination was
             found to be 0.04 mSv, which was 1.3% that of the chest CT
             examination. The average effective dose of the chest
             tomosynthesis examination was found to be about ten times
             that of the chest posteroanterior examination and about 12%
             that of the chest CT examination. With increasing patient
             average chest diameter, both the effective dose and risk
             index for CT increased considerably in an exponential
             fashion, while these two dose metrics only increased
             slightly for radiographic modalities and for chest
             tomosynthesis. Effective and organ doses normalized to mAs
             all illustrated an exponential decrease with increasing
             patient size. As a surface organ, breast doses had less
             correlation with body size than that of lungs or
             liver.Patient body size has a much greater impact on
             radiation dose of chest CT examinations than chest
             radiography and tomosynthesis. The size of a patient should
             be considered when choosing the best thoracic imaging
             modality.},
   Doi = {10.1118/1.4859315},
   Key = {fds269213}
}

@article{fds269219,
   Author = {Tian, X and Li, X and Segars, WP and Paulson, EK and Frush, DP and Samei,
             E},
   Title = {Pediatric chest and abdominopelvic CT: organ dose estimation
             based on 42 patient models.},
   Journal = {Radiology},
   Volume = {270},
   Number = {2},
   Pages = {535-547},
   Year = {2014},
   Month = {February},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/24126364},
   Abstract = {PURPOSE: To estimate organ dose from pediatric chest and
             abdominopelvic computed tomography (CT) examinations and
             evaluate the dependency of organ dose coefficients on
             patient size and CT scanner models. MATERIALS AND METHODS:
             The institutional review board approved this HIPAA-compliant
             study and did not require informed patient consent. A
             validated Monte Carlo program was used to perform
             simulations in 42 pediatric patient models (age range, 0-16
             years; weight range, 2-80 kg; 24 boys, 18 girls).
             Multidetector CT scanners were modeled on those from two
             commercial manufacturers (LightSpeed VCT, GE Healthcare,
             Waukesha, Wis; SOMATOM Definition Flash, Siemens Healthcare,
             Forchheim, Germany). Organ doses were estimated for each
             patient model for routine chest and abdominopelvic
             examinations and were normalized by volume CT dose index
             (CTDI(vol)). The relationships between CTDI(vol)-normalized
             organ dose coefficients and average patient diameters were
             evaluated across scanner models. RESULTS: For organs within
             the image coverage, CTDI(vol)-normalized organ dose
             coefficients largely showed a strong exponential
             relationship with the average patient diameter (R(2) > 0.9).
             The average percentage differences between the two scanner
             models were generally within 10%. For distributed organs and
             organs on the periphery of or outside the image coverage,
             the differences were generally larger (average, 3%-32%)
             mainly because of the effect of overranging. CONCLUSION: It
             is feasible to estimate patient-specific organ dose for a
             given examination with the knowledge of patient size and the
             CTDI(vol). These CTDI(vol)-normalized organ dose
             coefficients enable one to readily estimate patient-specific
             organ dose for pediatric patients in clinical settings. This
             dose information, and, as appropriate, attendant risk
             estimations, can provide more substantive information for
             the individual patient for both clinical and research
             applications and can yield more expansive information on
             dose profiles across patient populations within a
             practice.},
   Doi = {10.1148/radiol.13122617},
   Key = {fds269219}
}

@article{fds269203,
   Author = {Mahadevan, R and Ikejimba, LC and Lin, Y and Samei, E and Lo,
             JY},
   Title = {A task-based comparison of two reconstruction algorithms for
             digital breast tomosynthesis},
   Journal = {Proceedings of SPIE},
   Volume = {9033},
   Year = {2014},
   Month = {January},
   ISBN = {9780819498267},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.2043829},
   Abstract = {Digital breast tomosynthesis (DBT) generates 3-D
             reconstructions of the breast by taking X-Ray projections at
             various angles around the breast. DBT improves cancer
             detection as it minimizes tissue overlap that is present in
             traditional 2-D mammography. In this work, two methods of
             reconstruction, filtered backprojection (FBP) and the
             Newton-Raphson iterative reconstruction were used to create
             3-D reconstructions from phantom images acquired on a breast
             tomosynthesis system. The task based image analysis method
             was used to compare the performance of each reconstruction
             technique. The task simulated a 10mm lesion within the
             breast containing iodine concentrations between 0.0mg/ml and
             8.6mg/ml. The TTF was calculated using the reconstruction of
             an edge phantom, and the NPS was measured with a structured
             breast phantom (CIRS 020) over different exposure levels.
             The detectability index d’was calculated to assess
             image quality of the reconstructed phantom images. Image
             quality was assessed for both conventional, single energy
             and dual energy subtracted reconstructions. Dose allocation
             between the high and low energy scans was also examined.
             Over the full range of dose allocations, the iterative
             reconstruction yielded a higher detectability index than the
             FBP for single energy reconstructions. For dual energy
             subtraction, detectability index was maximized when most of
             the dose was allocated to the high energy image. With that
             dose allocation, the performance trend for reconstruction
             algorithms reversed; FBP performed better than the
             corresponding iterative reconstruction. However, FBP
             performance varied very erratically with changing dose
             allocation. Therefore, iterative reconstruction is preferred
             for both imaging modalities despite underperforming dual
             energy FBP, as it provides stable results. © 2014
             SPIE.},
   Doi = {10.1117/12.2043829},
   Key = {fds269203}
}

@article{fds269204,
   Author = {Segars, WP and Veress, AI and Wells, JR and Sturgeon, GM and Kiarashi,
             N and Lo, JY and Samei, E and Dobbins, JT},
   Title = {Population of 100 realistic, patient-based computerized
             breast phantoms for multi-modality imaging
             research},
   Journal = {Proceedings of SPIE},
   Volume = {9033},
   Year = {2014},
   Month = {January},
   ISBN = {9780819498267},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.2043868},
   Abstract = {Breast imaging is an important area of research with many
             new Techniques being investigated To further reduce The
             morbidity and mortality of breast cancer Through early
             detection. Computerized phantoms can provide an essential
             Tool To quantitatively compare new imaging systems and
             Techniques. Current phantoms, however, lack sufficient
             realism in depicting The complex 3D anatomy of The breast.
             In This work, we created one-hundred realistic and detailed
             3D computational breast phantoms based on high-resolution CT
             datasets from normal patients. We also developed a
             finiteelement application To simulate different compression
             states of The breast, making The phantoms applicable To
             multimodality imaging research. The breast phantoms and
             Tools developed in This work were packaged into
             user-friendly software applications To distribute for breast
             imaging research. © 2014 SPIE.},
   Doi = {10.1117/12.2043868},
   Key = {fds269204}
}

@article{fds269206,
   Author = {Nolte, A and Kiarashi, N and Samei, E and Segars, WP and Lo,
             JY},
   Title = {A second generation of physical anthropomorphic 3D breast
             phantoms based on human subject data},
   Journal = {Proceedings of SPIE},
   Volume = {9033},
   Year = {2014},
   Month = {January},
   ISBN = {9780819498267},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.2043703},
   Abstract = {Previous fabrication of anthropomorphic breast phantoms has
             demonstrated Their viability as a model for 2D (mammography)
             and 3D (tomosynthesis) breast imaging systems. Further
             development of These models will be essential for The
             evaluation of breast x-ray systems. There is also The
             potential To use Them as The ground Truth in virtual
             clinical Trials. The first generation of phantoms was
             segmented from human subject dedicated breast computed
             Tomography data and fabricated into physical models using
             highresolution 3D printing. Two variations were made. The
             first was a multi-material model (doublet) printed with Two
             photopolymers To represent glandular and adipose Tissues
             with The greatest physical contrast available, mimicking 75%
             and 35% glandular Tissue. The second model was printed with
             a single 75% glandular equivalent photopolymer (singlet) To
             represent glandular Tissue, which can be filled
             independently with an adipose-equivalent material such as
             oil. For This study, we have focused on improving The
             latter, The singlet phantom. First, The Temporary oil filler
             has been replaced with a permanent adipose-equivalent
             urethane-based polymer. This offers more realistic contrast
             as compared To The multi-material approach at The expense of
             air bubbles and pockets That form during The filling
             process. Second, microcalcification clusters have been
             included in The singlet model via crushed eggshells, which
             have very similar chemical composition To calcifications in
             vivo. The results from These new prototypes demonstrate
             significant improvement over The first generation of
             anthropomorphic physical phantoms. © 2014
             SPIE.},
   Doi = {10.1117/12.2043703},
   Key = {fds269206}
}

@article{fds269197,
   Author = {Chen, B and Wilson, J and Samei, E},
   Title = {A refined methodology for modeling volume quantification
             performance in CT},
   Journal = {Proceedings of SPIE},
   Volume = {9033},
   Year = {2014},
   Month = {January},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.2044004},
   Abstract = {The utility of CT lung nodule volume quantification
             technique depends on the precision of the quantification. To
             enable the evaluation of quantification precision, we
             previously developed a mathematical model that related
             precision to image resolution and noise properties in
             uniform backgrounds in terms of an estimability index
             (e’). The e’was shown to predict empirical
             precision across 54 imaging and reconstruction protocols,
             but with different correlation qualities for FBP and
             iterative reconstruction (IR) due to the non-linearity of IR
             impacted by anatomical structure. To better account for the
             non-linearity of IR, this study aimed to refine the noise
             characterization of the model in the presence of textured
             backgrounds. Repeated scans of an anthropomorphic lung
             phantom were acquired. Subtracted images were used to
             measure the image quantum noise, which was then used to
             adjust the noise component of the e’calculation
             measured from a uniform region. In addition to the model
             refinement, the validation of the model was further extended
             to 2 nodule sizes (5 and 10 mm) and 2 segmentation
             algorithms. Results showed that the magnitude of IR’s
             quantum noise was significantly higher in structured
             backgrounds than in uniform backgrounds (ASiR, 30-50%; MBIR,
             100-200%). With the refined model, the correlation between
             e’values and empirical precision no longer depended
             on reconstruction algorithm. In conclusion, the model with
             refined noise characterization relfected the nonlinearity of
             iterative reconstruction in structured background, and
             further showed successful prediction of quantification
             precision across a variety of nodule sizes, dose levels,
             slice thickness, reconstruction algorithms, and segmentation
             software. © 2014 SPIE.},
   Doi = {10.1117/12.2044004},
   Key = {fds269197}
}

@article{fds269198,
   Author = {Tian, X and Wilson, J and Frush, D and Samei, E},
   Title = {Prospective optimization of CT under tube current
             modulation: II. image quality},
   Journal = {Proceedings of SPIE},
   Volume = {9033},
   Year = {2014},
   Month = {January},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.2044013},
   Abstract = {Despite the significant clinical benefits of computed
             tomography (CT) in providing diagnostic information for a
             broad range of diseases, concerns have been raised regarding
             the potential cancer risk induced by CT radiation exposure.
             In that regard, optimizing CT protocols and minimizing
             radiation dose have become the core problem for the CT
             community. To develop strategies to optimize radiation dose,
             it is crucial to effectively characterize CT image quality.
             Such image quality estimates need to be prospective to
             ensure that optimization can be performed before the scan is
             initiated. The purpose of this study was to establish a
             phantombased methodology to predict quantum noise in CT
             images as a first step in our image quality prediction.
             Quantum noise was measured using a variable-sized phantom
             under clinical protocols. The mathematical relationship
             between noise and water-equivalent-diameter (Dw) was further
             established. The prediction was achieved by ascribing a
             noise value to a patient according to the patient’s
             water-equivalent- diameter. The prediction accuracy was
             evaluated in anthropomorphic phantoms across a broad range
             of sizes, anatomy, and reconstruction algorithms. The
             differences between the measured and predicted noise were
             within 10% for anthropomorphic phantoms across all sizes and
             anatomy. This study proposed a practically applicable
             technique to predict noise in CT images. With a prospective
             estimation of image quality level, the scanning parameters
             can then by adjusted to ensure optimized imaging
             performance. © 2014 SPIE.},
   Doi = {10.1117/12.2044013},
   Key = {fds269198}
}

@article{fds269199,
   Author = {Tian, X and Li, X and Segars, WP and Frush, D and Samei,
             E},
   Title = {Prospective optimization of CT under Tube current
             modulation: I. organ dose},
   Journal = {Proceedings of SPIE},
   Volume = {9033},
   Year = {2014},
   Month = {January},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.2043858},
   Abstract = {In an environment in which computed Tomography (CT) has
             become an indispensable diagnostic Tool employed with great
             frequency, dose concerns at The population level have become
             a subject of public attention. In That regard, optimizing
             radiation dose has become a core problem To The CT
             community. As a fundamental step To optimize radiation dose,
             it is crucial To effectively quantify radiation dose for a
             given CT exam. Such dose estimates need To be
             patient-specific To reflect individual radiation burden. It
             further needs To be prospective so That The scanning
             parameters can be dynamically adjusted before The scan is
             performed. The purpose of This study was To prospectively
             estimate organ dose in abdominopelvic CT exams under Tube
             current modulation (TCM). CTDI vol -normalized-organ dose
             coefficients (h fixed ) for fixed Tube current were first
             estimated using a validated Monte Carlo simulation program
             and 58 computational phantoms. To account for The effect of
             TCM scheme, a weighted CTDI vol was computed for each organ
             based on The Tube current modulation profile. The organ dose
             was predicted by multiplying The weighted CTDI vol with The
             organ dose coefficients (h fixed ). To quantify prediction
             accuracy, each predicted organ dose was compared with organ
             dose simulated from Monte Carlo program with TCM profile
             explicitly modeled. The predicted organ dose showed good
             agreement with simulated organ dose across all organs and
             modulation strengths. For an average CTDI vol of a CT exam
             of 10 mGy, The absolute median error across all organs were
             0.64 mGy (-0.21 and 0.97 for 25th and 75 th percentiles,
             respectively). The percentage differences (normalized by
             CTDI vol of The exam) were within 15%. This study developed
             a quantitative model To predict organ dose under clinical
             abdominopelvic scans. Such information may aid in The
             optimization of CT protocols. © 2014 SPIE.},
   Doi = {10.1117/12.2043858},
   Key = {fds269199}
}

@article{fds269200,
   Author = {Norris, H and Zhang, Y and Frush, J and Sturgeon, GM and Minhas, A and Tward, DJ and Ratnanather, JT and Miller, MI and Frush, D and Samei, E and Segars, WP},
   Title = {The development of a population of 4D pediatric XCAT
             phantoms for CT imaging research and optimization},
   Journal = {Proceedings of SPIE},
   Volume = {9033},
   Year = {2014},
   Month = {January},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.2043777},
   Abstract = {With The increased use of CT examinations, The associated
             radiation dose has become a large concern, especially for
             pediatrics. Much research has focused on reducing radiation
             dose Through new scanning and reconstruction methods.
             Computational phantoms provide an effective and efficient
             means for evaluating image quality, patient-specific dose,
             and organ-specific dose in CT. We previously developed a set
             of highly-detailed 4D reference pediatric XCAT phantoms at
             ages of newborn, 1, 5, 10, and 15 years with organ and
             Tissues masses matched To ICRP Publication 89 values. We now
             extend This reference set To a series of 64 pediatric
             phantoms of a variety of ages and height and weight
             percentiles, representative of The public at large. High
             resolution PET-CT data was reviewed by a practicing
             experienced radiologist for anatomic regularity and was Then
             segmented with manual and semi-Automatic methods To form a
             Target model. A Multi-Channel Large Deformation
             Diffeomorphic Metric Mapping (MC-LDDMM) algorithm was used
             To calculate The Transform from The best age matching
             pediatric reference phantom To The patient Target. The
             Transform was used To complete The Target, filling in The
             non-segmented structures and defining models for The cardiac
             and respiratory motions. The complete phantoms, consisting
             of Thousands of structures, were Then manually inspected for
             anatomical accuracy. 3D CT data was simulated from The
             phantoms To demonstrate Their ability To generate realistic,
             patient quality imaging data. The population of pediatric
             phantoms developed in This work provides a vital Tool To
             investigate dose reduction Techniques in 3D and 4D pediatric
             CT. © 2014 SPIE.},
   Doi = {10.1117/12.2043777},
   Key = {fds269200}
}

@article{fds269201,
   Author = {Solomon, J and Bochud, F and Samei, E},
   Title = {Design of anthropomorphic Textured phantoms for CT
             performance evaluation},
   Journal = {Proceedings of SPIE},
   Volume = {9033},
   Year = {2014},
   Month = {January},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.2043555},
   Abstract = {Commercially available computed Tomography (CT) Technologies
             such as iterative reconstruction (IR) have The potential To
             enable reduced patient doses while maintaining diagnostic
             image quality. However, systematically determining safe dose
             reduction levels for IR algorithms is a challenging Task due
             To Their nonlinear nature. Most attempts To evaluate IR
             algorithms rely on measurements made in uniform phantoms.
             Such measurements may overstate The dose reduction potential
             of IR because They don’t account for The complex
             relationship between anatomical variability and image
             quality. The purpose of This study was To design
             anatomically informed Textured phantoms for CT performance
             evaluation. Two phantoms were designed To represent lung and
             soft-tissue Textures. The lung phantom includes intricate
             vessel-like structures along with embedded nodules
             (spherical, lobulated, and spiculated). The soft Tissue
             phantom was designed based on a Three-dimensional clustered
             lumpy background with included low-contrast lesions
             (spherical and anthropomorphic). The phantoms were built
             using rapid prototyping (3D printing) Technology and imaged
             on a modern multi-slice clinical CT scanner To assess The
             noise performance of a commercial IR algorithm in The
             context of uniform and Textured backgrounds. Fifty repeated
             acquisitions were acquired for each background Type and
             noise was assessed by measuring pixel standard deviation,
             across The ensemble of repeated acquisitions. For pixels in
             uniform areas, The IR algorithm reduced noise magnitude
             (STD) by 60% (compared To FBP). However, for edge pixels,
             The noise magnitude in The IR images ranged from 20% higher
             To 40% lower compared To FBP. In all FBP images and in IR
             images of The uniform phantom, noise appeared To be globally
             non-stationary (i.e., spatially dependent) but locally
             stationary (within a reasonably small region of interest).
             In The IR images of The Textured phantoms, The noise was
             globally and locally non-stationary. © 2014
             SPIE.},
   Doi = {10.1117/12.2043555},
   Key = {fds269201}
}

@article{fds269202,
   Author = {Lakshmanan, MN and Kapadia, AJ and Harrawood, BP and Brady, D and Samei,
             E},
   Title = {X-ray coherent scatter imaging for surgical margin
             detection: A Monte Carlo study},
   Journal = {Proceedings of SPIE},
   Volume = {9033},
   Year = {2014},
   Month = {January},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.2043856},
   Abstract = {Instead of having the entire breast removed (a mastectomy),
             breast cancer patients often receive a breast con-serving
             surgery (BCS) for removal of only the breast tumor. If
             post-surgery analysis reveals ta missed margin around the
             tumor tissue excised through the BCS procedure, the
             physician must often call the patient back for another
             surgery, which is both difficult and risky for the patient.
             If this “margin detectionâ€could be performed
             during the BCS procedure itself, the surgical team could use
             the analysis to ensure that all tumor tissue was removed in
             a single surgery, thereby potentially reducing the number of
             call backs from breast cancer surgery. We describe here a
             potential technique to detect surgical tumor margins in
             breast cancer using x-ray coherent scatter imaging. In this
             study, we demonstrate the imaging ability of this technique
             using Monte Carlo simulations. © 2014 SPIE.},
   Doi = {10.1117/12.2043856},
   Key = {fds269202}
}

@article{fds269205,
   Author = {Lin, Y and Choudhury, KR and McAdams, HP and Foos, DH and Samei,
             E},
   Title = {Validation of an image-based technique to assess the
             perceptual quality of clinical chest radiographs with an
             observer study},
   Journal = {Proceedings of SPIE},
   Volume = {9033},
   Year = {2014},
   Month = {January},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.2043993},
   Abstract = {We previously proposed a novel image-based quality
             assessment technique 1 to assess the perceptual quality of
             clinical chest radiographs. In this paper, an observer study
             was designed and conducted to systematically validate this
             technique. Ten metrics were involved in the observer study,
             i.e., lung grey level, lung detail, lung noise, riblung
             contrast, rib sharpness, mediastinum detail, mediastinum
             noise, mediastinum alignment, subdiaphragm-lung contrast,
             and subdiaphragm area. For each metric, three tasks were
             successively presented to the observers. In each task, six
             ROI images were randomly presented in a row and observers
             were asked to rank the images only based on a designated
             quality and disregard the other qualities. A range slider on
             the top of the images was used for observers to indicate the
             acceptable range based on the corresponding perceptual
             attribute. Five boardcertificated radiologists from Duke
             participated in this observer study on a DICOM calibrated
             diagnostic display workstation and under low ambient
             lighting conditions. The observer data were analyzed in
             terms of the correlations between the observer ranking
             orders and the algorithmic ranking orders. Based on the
             collected acceptable ranges, quality consistency ranges were
             statistically derived. The observer study showed that, for
             each metric, the averaged ranking orders of the participated
             observers were strongly correlated with the algorithmic
             orders. For the lung grey level, the observer ranking orders
             completely accorded with the algorithmic ranking orders. The
             quality consistency ranges derived from this observer study
             were close to these derived from our previous study. The
             observer study indicates that the proposed image-based
             quality assessment technique provides a robust reflection of
             the perceptual image quality of the clinical chest
             radiographs. The derived quality consistency ranges can be
             used to automatically predict the acceptability of a
             clinical chest radiograph. © 2014 SPIE.},
   Doi = {10.1117/12.2043993},
   Key = {fds269205}
}

@article{fds269217,
   Author = {Nelson, JS and Christianson, OI and Harkness, BA and Madsen, MT and Mah,
             E and Thomas, SR and Zaidi, H and Samei, E},
   Title = {Improved nuclear medicine uniformity assessment with noise
             texture analysis.},
   Journal = {Journal of nuclear medicine : official publication, Society
             of Nuclear Medicine},
   Volume = {55},
   Number = {1},
   Pages = {169-174},
   Year = {2014},
   Month = {January},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/24212975},
   Abstract = {UNLABELLED: Because γ cameras are generally susceptible to
             environmental conditions and system vulnerabilities, they
             require routine evaluation of uniformity performance. The
             metrics for such evaluations are commonly pixel value-based.
             Although these metrics are typically successful at
             identifying regional nonuniformities, they often do not
             adequately reflect subtle periodic structures; therefore,
             additional visual inspections are required. The goal of this
             project was to develop, test, and validate a new uniformity
             analysis metric capable of accurately identifying structures
             and patterns present in nuclear medicine flood-field
             uniformity images. METHODS: A new uniformity assessment
             metric, termed the structured noise index (SNI), was based
             on the 2-dimensional noise power spectrum (NPS). The
             contribution of quantum noise was subtracted from the NPS of
             a flood-field uniformity image, resulting in an NPS
             representing image artifacts. A visual response filter
             function was then applied to both the original NPS and the
             artifact NPS. A single quantitative score was calculated on
             the basis of the magnitude of the artifact. To verify the
             validity of the SNI, an observer study was performed with 5
             expert nuclear medicine physicists. The correlation between
             the SNI and the visual score was assessed with Spearman rank
             correlation analysis. The SNI was also compared with pixel
             value-based assessment metrics modeled on the National
             Electrical Manufacturers Association standard for integral
             uniformity in both the useful field of view (UFOV) and the
             central field of view (CFOV). RESULTS: The SNI outperformed
             the pixel value-based metrics in terms of its correlation
             with the visual score (ρ values for the SNI, integral UFOV,
             and integral CFOV were 0.86, 0.59, and 0.58, respectively).
             The SNI had 100% sensitivity for identifying both structured
             and nonstructured nonuniformities; for the integral UFOV and
             CFOV metrics, the sensitivities were only 62% and 54%,
             respectively. The overall positive predictive value of the
             SNI was 87%; for the integral UFOV and CFOV metrics, the
             positive predictive values were only 67% and 50%,
             respectively. CONCLUSION: The SNI accurately identified both
             structured and nonstructured flood-field nonuniformities and
             correlated closely with expert visual assessment. Compared
             with traditional pixel value-based analysis, the SNI showed
             superior performance in terms of its correlation with visual
             perception. The SNI method is effective for detecting and
             quantifying visually apparent nonuniformities and may reduce
             the need for more subjective visual analyses.},
   Doi = {10.2967/jnumed.113.125450},
   Key = {fds269217}
}

@article{fds269175,
   Author = {Samei, E and Christianson, O},
   Title = {Dose index analytics: More than a low number},
   Journal = {Journal of the American College of Radiology},
   Volume = {11},
   Number = {8},
   Pages = {832-834},
   Publisher = {Elsevier},
   Year = {2014},
   ISSN = {1546-1440},
   url = {http://dx.doi.org/10.1016/j.jacr.2014.05.004},
   Doi = {10.1016/j.jacr.2014.05.004},
   Key = {fds269175}
}

@article{fds269190,
   Author = {Samei, E and Christianson, O},
   Title = {Dose index analytics: More than a low number},
   Journal = {Journal of the American College of Radiology},
   Volume = {11},
   Number = {8},
   Pages = {832-834},
   Publisher = {Elsevier},
   Year = {2014},
   ISSN = {1546-1440},
   url = {http://dx.doi.org/10.1016/j.jacr.2014.05.004},
   Doi = {10.1016/j.jacr.2014.05.004},
   Key = {fds269190}
}

@article{fds269216,
   Author = {Tian, X and Li, X and Segars, WP and Frush, DP and Paulson, EK and Samei,
             E},
   Title = {Dose coefficients in pediatric and adult abdominopelvic CT
             based on 100 patient models.},
   Journal = {Physics in Medicine and Biology},
   Volume = {58},
   Number = {24},
   Pages = {8755-8768},
   Year = {2013},
   Month = {December},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/24301136},
   Abstract = {Recent studies have shown the feasibility of estimating
             patient dose from a CT exam using CTDI(vol)-normalized-organ
             dose (denoted as h), DLP-normalized-effective dose (denoted
             as k), and DLP-normalized-risk index (denoted as q).
             However, previous studies were limited to a small number of
             phantom models. The purpose of this work was to provide dose
             coefficients (h, k, and q) across a large number of
             computational models covering a broad range of patient
             anatomy, age, size percentile, and gender. The study
             consisted of 100 patient computer models (age range, 0 to 78
             y.o.; weight range, 2-180 kg) including 42 pediatric models
             (age range, 0 to 16 y.o.; weight range, 2-80 kg) and 58
             adult models (age range, 18 to 78 y.o.; weight range, 57-180
             kg). Multi-detector array CT scanners from two commercial
             manufacturers (LightSpeed VCT, GE Healthcare; SOMATOM
             Definition Flash, Siemens Healthcare) were included. A
             previously-validated Monte Carlo program was used to
             simulate organ dose for each patient model and each scanner,
             from which h, k, and q were derived. The relationships
             between h, k, and q and patient characteristics (size, age,
             and gender) were ascertained. The differences in conversion
             coefficients across the scanners were further characterized.
             CTDI(vol)-normalized-organ dose (h) showed an exponential
             decrease with increasing patient size. For organs within the
             image coverage, the average differences of h across scanners
             were less than 15%. That value increased to 29% for organs
             on the periphery or outside the image coverage, and to 8%
             for distributed organs, respectively. The
             DLP-normalized-effective dose (k) decreased exponentially
             with increasing patient size. For a given gender, the
             DLP-normalized-risk index (q) showed an exponential decrease
             with both increasing patient size and patient age. The
             average differences in k and q across scanners were 8% and
             10%, respectively. This study demonstrated that the
             knowledge of patient information and CTDIvol/DLP values may
             be used to estimate organ dose, effective dose, and risk
             index in abdominopelvic CT based on the coefficients derived
             from a large population of pediatric and adult
             patients.},
   Doi = {10.1088/0031-9155/58/24/8755},
   Key = {fds269216}
}

@article{fds269214,
   Author = {Marin, D and Choudhury, KR and Gupta, RT and Ho, LM and Allen, BC and Schindera, ST and Colsher, JG and Samei, E and Nelson,
             RC},
   Title = {Clinical impact of an adaptive statistical iterative
             reconstruction algorithm for detection of hypervascular
             liver tumours using a low tube voltage, high tube current
             MDCT technique},
   Journal = {European Radiology},
   Volume = {23},
   Number = {12},
   Pages = {3325-3335},
   Year = {2013},
   Month = {December},
   ISSN = {0938-7994},
   url = {http://dx.doi.org/10.1007/s00330-013-2964-1},
   Abstract = {Objectives: To investigate the impact of an adaptive
             statistical iterative reconstruction (ASiR) algorithm on
             diagnostic accuracy and confidence for the diagnosis of
             hypervascular liver tumours, as well as the reader's
             perception of image quality, using a low tube voltage (80
             kVp), high tube current computed tomography (CT) technique.
             Methods: Forty patients (29 men, 11 women) with 65
             hypervascular liver tumours underwent dual energy CT. The 80
             kV set of the dual energy acquisition was reconstructed with
             standard filtered backprojection (FBP) and ASiR at different
             blending levels. Lesion contrast-to-noise ratio (CNR),
             reader's confidence for lesion detection and
             characterisation, and reader's evaluation of image quality
             were recorded. Results: ASiR yielded significantly higher
             CNR values compared with FBP (P < 0.0001 for all
             comparisons). Reader's perception of lesion conspicuity and
             confidence in the diagnosis of malignancy were also higher
             with 60 % and 80 % ASiR, compared with FBP (P = 0.01 and <
             0.001, respectively). Compared with FBP, ASiR yielded nearly
             significantly lower specificity for lesion detection and a
             substantial decrease in the reader's perception of image
             quality. Conclusions: Compared with the standard FBP
             algorithm, ASiR significantly improves conspicuity of
             hypervascular liver lesions. This improvement may come at
             the cost of decreased specificity and reader's perception of
             image quality. Key Points: • Adaptive statistical
             iterative reconstruction algorithms (ASiRs) offer increasing
             potential in multidetector CT. • An ASiR algorithm
             significantly improves conspicuity of hypervascular liver
             lesions at MDCT. • Improved lesion conspicuity translates
             into increased reader's confidence for diagnosis of
             malignancy. • False positive findings may increase with
             ASiR, leading to potentially lower specificity. © 2013
             European Society of Radiology.},
   Doi = {10.1007/s00330-013-2964-1},
   Key = {fds269214}
}

@article{fds269233,
   Author = {Marin, D and Choudhury, KR and Gupta, RT and Ho, LM and Allen, BC and Schindera, ST and Colsher, JG and Samei, E and Nelson,
             RC},
   Title = {Clinical impact of an adaptive statistical iterative
             reconstruction algorithm for detection of hypervascular
             liver tumours using a low tube voltage, high tube current
             MDCT technique.},
   Journal = {European Radiology},
   Volume = {23},
   Number = {12},
   Pages = {3325-3335},
   Year = {2013},
   Month = {December},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/23832320},
   Abstract = {OBJECTIVES: To investigate the impact of an adaptive
             statistical iterative reconstruction (ASiR) algorithm on
             diagnostic accuracy and confidence for the diagnosis of
             hypervascular liver tumours, as well as the reader's
             perception of image quality, using a low tube voltage (80
             kVp), high tube current computed tomography (CT) technique.
             METHODS: Forty patients (29 men, 11 women) with 65
             hypervascular liver tumours underwent dual energy CT. The 80
             kV set of the dual energy acquisition was reconstructed with
             standard filtered backprojection (FBP) and ASiR at different
             blending levels. Lesion contrast-to-noise ratio (CNR),
             reader's confidence for lesion detection and
             characterisation, and reader's evaluation of image quality
             were recorded. RESULTS: ASiR yielded significantly higher
             CNR values compared with FBP (P < 0.0001 for all
             comparisons). Reader's perception of lesion conspicuity and
             confidence in the diagnosis of malignancy were also higher
             with 60 % and 80 % ASiR, compared with FBP (P = 0.01
             and < 0.001, respectively). Compared with FBP, ASiR
             yielded nearly significantly lower specificity for lesion
             detection and a substantial decrease in the reader's
             perception of image quality. CONCLUSIONS: Compared with the
             standard FBP algorithm, ASiR significantly improves
             conspicuity of hypervascular liver lesions. This improvement
             may come at the cost of decreased specificity and reader's
             perception of image quality.},
   Doi = {10.1007/s00330-013-2964-1},
   Key = {fds269233}
}

@article{fds269215,
   Author = {Chen, B and Barnhart, H and Richard, S and Robins, M and Colsher, J and Samei, E},
   Title = {Volumetric quantification of lung nodules in CT with
             iterative reconstruction (ASiR and MBIR).},
   Volume = {40},
   Number = {11},
   Pages = {111902},
   Year = {2013},
   Month = {November},
   ISSN = {0094-2405},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/24320435},
   Abstract = {PURPOSE: Volume quantifications of lung nodules with
             multidetector computed tomography (CT) images provide useful
             information for monitoring nodule developments. The accuracy
             and precision of the volume quantification, however, can be
             impacted by imaging and reconstruction parameters. This
             study aimed to investigate the impact of iterative
             reconstruction algorithms on the accuracy and precision of
             volume quantification with dose and slice thickness as
             additional variables. METHODS: Repeated CT images were
             acquired from an anthropomorphic chest phantom with
             synthetic nodules (9.5 and 4.8 mm) at six dose levels, and
             reconstructed with three reconstruction algorithms [filtered
             backprojection (FBP), adaptive statistical iterative
             reconstruction (ASiR), and model based iterative
             reconstruction (MBIR)] into three slice thicknesses. The
             nodule volumes were measured with two clinical software (A:
             Lung VCAR, B: iNtuition), and analyzed for accuracy and
             precision. RESULTS: Precision was found to be generally
             comparable between FBP and iterative reconstruction with no
             statistically significant difference noted for different
             dose levels, slice thickness, and segmentation software.
             Accuracy was found to be more variable. For large nodules,
             the accuracy was significantly different between ASiR and
             FBP for all slice thicknesses with both software, and
             significantly different between MBIR and FBP for 0.625 mm
             slice thickness with Software A and for all slice
             thicknesses with Software B. For small nodules, the accuracy
             was more similar between FBP and iterative reconstruction,
             with the exception of ASIR vs FBP at 1.25 mm with Software A
             and MBIR vs FBP at 0.625 mm with Software A. CONCLUSIONS:
             The systematic difference between the accuracy of FBP and
             iterative reconstructions highlights the importance of
             extending current segmentation software to accommodate the
             image characteristics of iterative reconstructions. In
             addition, a calibration process may help reduce the
             dependency of accuracy on reconstruction algorithms, such
             that volumes quantified from scans of different
             reconstruction algorithms can be compared. The little
             difference found between the precision of FBP and iterative
             reconstructions could be a result of both iterative
             reconstruction's diminished noise reduction at the edge of
             the nodules as well as the loss of resolution at high noise
             levels with iterative reconstruction. The findings do not
             rule out potential advantage of IR that might be evident in
             a study that uses a larger number of nodules or repeated
             scans.},
   Doi = {10.1118/1.4823463},
   Key = {fds269215}
}

@article{fds269220,
   Author = {Hoang, JK and Wang, C and Frush, DP and Enterline, DS and Samei, E and Toncheva, G and Lowry, C and Yoshizumi, TT},
   Title = {Estimation of radiation exposure for brain perfusion CT:
             standard protocol compared with deviations in
             protocol.},
   Journal = {AJR. American journal of roentgenology},
   Volume = {201},
   Number = {5},
   Pages = {W730-W734},
   Year = {2013},
   Month = {November},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/24063388},
   Abstract = {OBJECTIVE: The purpose of this study was to measure the
             organ doses and estimate the effective dose for the standard
             brain perfusion CT protocol and erroneous protocols.
             MATERIALS AND METHODS: An anthropomorphic phantom with metal
             oxide semiconductor field effect transistor (MOSFET)
             detectors was scanned on a 64-MDCT scanner. Protocol 1 used
             a standard brain perfusion protocol with 80 kVp and fixed
             tube current of 200 mA. Protocol 2 used 120 kVp and fixed
             tube current of 200 mA. Protocol 3 used 120 kVp with
             automatic tube current modulation (noise index, 2.4;
             minimum, 100 mA; maximum, 520 mA). RESULTS: Compared with
             protocol 1, the effective dose was 2.8 times higher with
             protocol 2 and 7.8 times higher with protocol 3. For all
             protocols, the peak dose was highest in the skin, followed
             by the brain and calvarial marrow. Compared with protocol 1,
             the peak skin dose was 2.6 times higher with protocol 2 and
             6.7 times higher with protocol 3. The peak skin dose for
             protocol 3 exceeded 3 Gy. The ocular lens received
             significant scatter radiation: 177 mGy for protocol 2 and
             435 mGy for protocol 3, which were 4.6 and 11.3 times the
             dose for protocol 1, respectively. CONCLUSION: Compared with
             the standard protocol, erroneous protocols of increasing the
             tube potential from 80 kVp to 120 kVp will lead to a three-
             to fivefold increase in organ doses, and concurrent use of
             high peak kilovoltage with incorrectly programmed tube
             current modulation can increase dose to organs by 7- to
             11-fold. Tube current modulation with a low noise index can
             lead to doses to the skin and ocular lens that are close to
             thresholds for tissue reactions.},
   Doi = {10.2214/AJR.12.10031},
   Key = {fds269220}
}

@article{fds269218,
   Author = {Kiarashi, N and Samei, E},
   Title = {Digital breast tomosynthesis: A concise overview},
   Journal = {Imaging in Medicine},
   Volume = {5},
   Number = {5},
   Pages = {467-476},
   Year = {2013},
   Month = {October},
   ISSN = {1755-5191},
   url = {http://dx.doi.org/10.2217/iim.13.52},
   Abstract = {The proven limited sensitivity of mammography, due to tissue
             superposition in a 2D image, has motivated the development
             of alternative 3D imaging systems with minimal ionizing
             exposure and relatively low cost. The advent of digital
             detectors facilitated the realization of digital breast
             tomosynthesis systems, which acquire low-dose projection
             images of the breast from multiple directions to synthesize
             slices through the volume of the breast parallel to the
             plane of the projection images. Although still in its
             clinical infancy, this imaging system has been studied in a
             multitude of domains. This concise overview introduces
             digital breast tomosynthesis and elaborates on the
             state-of-the-art in its applications and performance. ©
             2013 Future Medicine Ltd.},
   Doi = {10.2217/iim.13.52},
   Key = {fds269218}
}

@article{fds269226,
   Author = {Boyce, SJ and Choudhury, KR and Samei, E},
   Title = {Effective DQE (eDQE) for monoscopic and stereoscopic chest
             radiography imaging systems with the incorporation of
             anatomical noise.},
   Volume = {40},
   Number = {9},
   Pages = {091916},
   Year = {2013},
   Month = {September},
   ISSN = {0094-2405},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/24007167},
   Abstract = {PURPOSE: Stereoscopic chest biplane correlation imaging
             (stereo∕BCI) has been proposed as an alternative modality
             to single view chest x-ray (CXR). The metrics effective
             modulation transfer function (eMTF), effective normalized
             noise power spectrum (eNNPS), and effective detective
             quantum efficiency (eDQE) have been proposed as clinically
             relevant metrics for assessing clinical system performance
             taking into consideration the magnification and scatter
             effects. This study compared the metrics eMTF, eNNPS, eDQE,
             and detectability index for stereo∕BCI and single view CXR
             under isodose conditions at two magnifications for two
             anthropomorphic phantoms of differing sizes. METHODS:
             Measurements for the eMTF were taken for two phantom sizes
             with an opaque edge test device using established
             techniques. The eNNPS was measured at two isodose conditions
             for two phantoms using established techniques. The scatter
             was measured for two phantoms using an established beam stop
             method. All measurements were also taken at two different
             magnifications with two phantoms. A geometrical phantom was
             used for comparison with prior results for CXR although the
             results for an anatomy free phantom are not expected to vary
             for BCI. RESULTS: Stereo∕BCI resulted in improved metrics
             compared to single view CXR. Results indicated that
             magnification can potentially improve the detection
             performance primarily due to the air gap which reduced
             scatter by ∼20%. For both phantoms, at isodose, eDQE(0)
             for stereo∕BCI was ∼100 times higher than that for CXR.
             Magnification at isodose improved eDQE(0) by ∼10 times for
             stereo∕BCI. Increasing the dose did not improve eDQE. The
             detectability index for stereo∕BCI was ∼100 times better
             than single view CXR for all conditions. The detectability
             index was also not improved with increased dose.
             CONCLUSIONS: The findings indicate that stereo∕BCI with
             magnification may improve detectability of subtle lung
             nodules compared to single view CXR. Results were improved
             with magnification for the smaller phantom but not for the
             larger phantom. The effective DQE and the detectability
             index did not improve with increasing dose.},
   Doi = {10.1118/1.4818060},
   Key = {fds269226}
}

@article{fds269227,
   Author = {Swanick, CW and Gaca, AM and Hollingsworth, CL and Maxfield, CM and Li,
             X and Samei, E and Paulson, EK and McCarthy, MB and Frush,
             DP},
   Title = {Comparison of conventional and simulated reduced-tube
             current MDCT for evaluation of suspected appendicitis in the
             pediatric population.},
   Journal = {AJR. American journal of roentgenology},
   Volume = {201},
   Number = {3},
   Pages = {651-658},
   Year = {2013},
   Month = {September},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/23971460},
   Abstract = {OBJECTIVE: The purpose of this study was to compare CT with
             conventional and simulated reduced-tube current in the
             evaluation for acute appendicitis in children. MATERIALS AND
             METHODS: Validated noise-addition (tube current-reduction)
             software was used to create 50% and 75% tube current
             reductions in 60 CT examinations performed for suspected
             appendicitis, resulting in 180 image sets. Three blinded
             pediatric radiologists scored the randomized studies for the
             following factors: presence of the normal appendix or
             appendicitis (5-point scale; 1=definitely absent and
             5=definitely present), presence of alternate diagnoses, and
             overall image quality (1=nondiagnostic and 5=excellent).
             Truth was defined by the interpretation of the conventional
             examination. RESULTS: For conventional examinations, the
             total number of reviews (60 cases×3 readers=180) in which
             the normal appendix was identified was 120 of 180 (66.7%),
             compared with 108 of 180 (60%) in the 50% (p=0.19) and 91 of
             180 (50.6%) in the 75% (p=0.002) tube current-reduction
             groups. Appendicitis was identified in a total of 39 of 180
             (21.7%), 38 of 180 (21.1%), and 37 of 180 (20.6%)
             examinations, respectively (p>0.05). This translates to
             sensitivities of 97% and 95% for the 50% and 75% tube
             current-reduction groups, respectively. Alternate diagnoses
             were detected in 14%, 16%, and 13% of scans, respectively.
             Compared with conventional-tube current examinations, reader
             confidence and assessment of image quality were
             significantly decreased for both tube current-reduction
             groups. CONCLUSION: Simulated tube current-reduction
             technology provides for systematic evaluation of diagnostic
             thresholds. Application of this technology in the setting of
             suspected appendicitis shows that tube current can be
             reduced by at least 50% without significantly affecting
             diagnostic quality, despite a decrease in reader confidence
             and assessment of image quality.},
   Doi = {10.2214/AJR.12.9667},
   Key = {fds269227}
}

@article{fds269228,
   Author = {Samei, E and Murphy, S and Christianson, O},
   Title = {DQE of wireless digital detectors: comparative performance
             with differing filtration schemes.},
   Volume = {40},
   Number = {8},
   Pages = {081910},
   Year = {2013},
   Month = {August},
   ISSN = {0094-2405},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/23927324},
   Abstract = {PURPOSE: Wireless flat panel detectors are gaining increased
             usage in portable medical imaging. Two such detectors were
             evaluated and compared with a conventional flat-panel
             detector using the formalism of the International
             Electrotechnical Commission (IEC 62220-1) for measuring
             modulation transfer function (MTF), normalized noise power
             spectrum (NNPS), and detective quantum efficiency (DQE)
             using two different filtration schemes. METHODS: Raw images
             were acquired for three image receptors (DRX-1C and DRX-1,
             Carestream Health; Inc., Pixium 4600, Trixell) using a
             radiographic system with a well-characterized output
             (Philips Super80 CP, Philips Healthcare). Free in-air
             exposures were measured using a calibrated radiation meter
             (Unfors Mult-O-Meter Type 407, Unfors Instruments AB).
             Additional aluminum filtration and a new alternative
             combined copper-aluminum filtration were used to conform the
             x ray output to IEC-specified beam quality definitions RQA5
             and RQA9. Using the IEC 62220-1 formalism, each detector was
             evaluated at XN∕2, XN, and 2XN, where the normal exposure
             level to the detector surface (XN) was set to 8.73 μGy (1.0
             mR). The prescribed edge test device was used to evaluate
             the MTF, while the NNPS was measured using uniform images.
             The DQE was then calculated from the MTF and NNPS and
             compared across detectors, exposures, and filtration
             schemes. RESULTS: The three DR systems had largely
             comparable MTFs with DRX-1 demonstrating lower values above
             1.0 cycles∕mm. At each exposure, DRX-1C and Pixium
             detectors demonstrated better noise performance than that of
             DRX-1. Zero-frequency DQEs for DRX-1C, Pixium, and DRX-1
             detectors were approximately 74%, 63%, and 38% for RQA5 and
             50%, 42%, and 28% for RQA9, respectively. CONCLUSIONS:
             DRX-1C detector exhibited superior DQE performance compared
             to Pixium and DRX-1. In terms of filtration, the alternative
             filtration was found to provide comparable performance in
             terms of rank ordering of different detectors with the added
             convenience of being less bulky for in-the-field
             measurements.},
   Doi = {10.1118/1.4813298},
   Key = {fds269228}
}

@article{fds327417,
   Author = {Christianson, O and Winslow, J and Samei, E},
   Title = {TU-C-103-10: An Automated Technique to Measure CT Noise in
             Patient Images},
   Journal = {Medical physics},
   Volume = {40},
   Number = {6Part26},
   Pages = {438-438},
   Year = {2013},
   Month = {June},
   url = {http://dx.doi.org/10.1118/1.4815399},
   Doi = {10.1118/1.4815399},
   Key = {fds327417}
}

@article{fds327670,
   Author = {Solomon, J and Nelson, R and Samei, E},
   Title = {TU-C-103-01: A Framework for 3D Modeling of Anthropomorphic
             Lesions in CT},
   Journal = {Medical physics},
   Volume = {40},
   Number = {6Part26},
   Pages = {436-436},
   Year = {2013},
   Month = {June},
   url = {http://dx.doi.org/10.1118/1.4815390},
   Doi = {10.1118/1.4815390},
   Key = {fds327670}
}

@article{fds269388,
   Author = {Samei, E and Li, X and Chen, B and Reiman, R},
   Title = {The effect of dose heterogeneity on radiation risk in
             medical imaging.},
   Journal = {Radiation Protection Dosimetry},
   Volume = {155},
   Number = {1},
   Pages = {42-58},
   Year = {2013},
   Month = {June},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/23118440},
   Abstract = {The current estimations of risk associated with medical
             imaging procedures rely on assessing the organ dose via
             direct measurements or simulation. The dose to each organ is
             assumed to be homogeneous. To take into account the
             differences in radiation sensitivities, the mean organ doses
             are weighted by a corresponding tissue-weighting
             coefficients provided by ICRP to calculate the effective
             dose, which has been used as a surrogate of radiation risk.
             However, those coefficients were derived under the
             assumption of a homogeneous dose distribution within each
             organ. That assumption is significantly violated in most
             medical-imaging procedures. In helical chest CT, for
             example, superficial organs (e.g. breasts) demonstrate a
             heterogeneous dose distribution, whereas organs on the
             peripheries of the irradiation field (e.g. liver) might
             possess a discontinuous dose profile. Projection radiography
             and mammography involve an even higher level of organ dose
             heterogeneity spanning up to two orders of magnitude. As
             such, mean dose or point measured dose values do not reflect
             the maximum energy deposited per unit volume of the organ.
             In this paper, the magnitude of the dose heterogeneity in
             both CT and projection X-ray imaging was reported, using
             Monte Carlo methods. The lung dose demonstrated factors of
             1.7 and 2.2 difference between the mean and maximum dose for
             chest CT and radiography, respectively. The corresponding
             values for the liver were 1.9 and 3.5. For mammography and
             breast tomosynthesis, the difference between mean glandular
             dose and maximum glandular dose was 3.1. Risk models based
             on the mean dose were found to provide a reasonable
             reflection of cancer risk. However, for leukaemia, they were
             found to significantly under-represent the risk when the
             organ dose distribution is heterogeneous. A systematic study
             is needed to develop a risk model for heterogeneous dose
             distributions.},
   Doi = {10.1093/rpd/ncs275},
   Key = {fds269388}
}

@article{fds328132,
   Author = {Christianson, O and Winslow, J and Solomon, J and Samei,
             E},
   Title = {WE-C-103-06: An Automated CT Quality Control
             Program.},
   Journal = {Medical physics},
   Volume = {40},
   Number = {6Part29},
   Pages = {481},
   Year = {2013},
   Month = {June},
   url = {http://dx.doi.org/10.1118/1.4815555},
   Abstract = {Daily image quality assessment is an essential part of a
             rigorous quality control program. Time constraints; however,
             make it difficult to fully analyze image quality daily.
             Therefore, the goal of this work was to develop a robust
             automated CT quality control program to extract meaningful
             image quality metrics including artifact analysis, noise
             texture measurement, and the calculation of a detectability
             index.The ACR CT phantom was scanned on five different CT
             scanners. The automated algorithm was used to calculate the
             standard metrics including HU accuracy, CNR, noise, and
             uniformity as well as more advanced metrics including the
             MTF, NPS, detectability index, and artifact detection. To
             validate the automated program, the HU accuracy, CNR, and
             noise metrics were compared to measurements conducted by a
             human observer. Additionally, the 10th percentile of the MTF
             (MTF 10) was compared the high-contrast resolution and the
             detectability index was compared to the low-contrast
             detectability recorded by the human observer using the
             Spearman rank sum correlation.The HU, CNR, and noise
             determined by the automated algorithm agreed well with the
             human observer measurements (0.12%, 5.1%, and 7.1%
             difference for the HU, CNR, and noise respectively).
             Further, there was a strong correlation between MTF10 and
             the observer high-contrast resolution as well as the
             detectability index and the low-contrast detectability
             (rho=1 in both cases).There was a strong agreement between
             the results of the automated quality control program and the
             human observer measurements. Further, the Fourier based MTF
             and detectability index were found to correlate strongly
             with observer image quality assessment. Therefore, this
             automated quality control program offers a viable
             alternative for routine image quality assessment of the ACR
             phantom.},
   Doi = {10.1118/1.4815555},
   Key = {fds328132}
}

@article{fds328133,
   Author = {Samei, E},
   Title = {MO-A-141-01: Memorial to Fearghus O' tFoghludha - Memorial
             Lecture.},
   Journal = {Medical physics},
   Volume = {40},
   Number = {6Part23},
   Pages = {390},
   Year = {2013},
   Month = {June},
   url = {http://dx.doi.org/10.1118/1.4815217},
   Abstract = {Medical Physics community lost one of its prominent members,
             Fearghus O' tFoghludha, in July 2012. Fearghus O' tFoghludha
             was the editor of Medical Physics from 1985 to 1987 and the
             President of the AAPM from 1971 to 1972. Born in 1927 in
             Dublin, Fearghus studied at University College Dublin,
             National University of Ireland, Royal University of Uppsala
             (Sweden), and the University of Lund (Sweden). He served as
             Senior Physicist at St. Luke's Hospital in Dublin and the
             head of Radiation Physics at the Medical College of Virginia
             till 1970 when he joined Duke University. Noteworthy among
             his accomplishments are the design and optimization of
             modern mammography equipment, and the design of an
             experiment on solar radiation for the Apollo 13 lunar
             mission. He was one of the pioneers in designing imaging
             equipment so that radiation dose can be minimized. During
             his distinguished career, he had working affiliation with
             the Oak Ridge National Lab, NIH, NSF, ACR, the Atomic Energy
             Commission, CERN, and NASA.},
   Doi = {10.1118/1.4815217},
   Key = {fds328133}
}

@article{fds328134,
   Author = {Norris, H and Bond, J and Zhang, Y and Sturgeon, G and Tward, D and Ratnanather, T and Miller, M and Samei, E and Segars,
             P},
   Title = {MO-D-141-10: Development of 4D XCAT Pediatric Reference
             Phantoms for Multi-Modality Imaging Research and
             Optimization.},
   Journal = {Medical physics},
   Volume = {40},
   Number = {6Part24},
   Pages = {401},
   Year = {2013},
   Month = {June},
   url = {http://dx.doi.org/10.1118/1.4815257},
   Abstract = {A set of 4D Extended Cardiac-Torso (XCAT) pediatric
             reference phantoms were created for multimodality imaging
             research, which have highly detailed whole-body anatomies,
             including cardiac and respiratory functions. Models were
             created for newborn, 1-year, 5-year, 10-year, and 15-year
             old males and females capturing the anatomical variations of
             childhood development.The initial anatomy of each phantom
             was obtained from the Duke University PET-CT database. The
             major organs and structures for each phantom were segmented
             from the corresponding data using semiautomatic and manual
             segmentation. 3D Non-Uniform Rational B-Spline (NURBS)
             surfaces were fitted to the segmented data. Arms and legs
             were manually attached using scaled versions of the original
             XCAT adult male and female phantoms. Some patient datasets
             had incomplete skulls; skullcaps were manually matched to
             complete the skulls of these datasets. A multichannel large
             deformation diffeomorphic metric mapping (MC-LDDMM)
             algorithm was used to calculate the transform from a
             template XCAT phantom to the target patient model, which
             filled in unsegmented structures within the target phantom
             and implemented the 4D cardiac and respiratory models in the
             new anatomy. Organ weights were matched to the 50th
             percentile ICRP publication 89 values within 5%.A reference
             set of 10 pediatric phantoms were created with thousands of
             anatomical structures and cardiac and respiratory motions.
             These phantoms can be combined with existing simulation
             packages to simulate realistic imaging data. The phantoms
             provide a valuable tool to investigate radiation dose and
             image quality optimization.The development of
             patient-derived pediatric computational phantoms is useful
             in providing variable anatomies for simulation. Future work
             will expand this 10-phantom base to a host of pediatric
             phantoms representative of the public at large. This can
             provide a means to evaluate and improve pediatric imaging
             devices and to optimize CT protocols in terms of image
             quality and radiation dose.},
   Doi = {10.1118/1.4815257},
   Key = {fds328134}
}

@article{fds269234,
   Author = {Chen, B and Marin, D and Richard, S and Husarik, D and Nelson, R and Samei,
             E},
   Title = {Precision of iodine quantification in hepatic CT: effects of
             iterative reconstruction with various imaging
             parameters.},
   Journal = {AJR. American journal of roentgenology},
   Volume = {200},
   Number = {5},
   Pages = {W475-W482},
   Year = {2013},
   Month = {May},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/23617515},
   Abstract = {OBJECTIVE: The objective of this study was to evaluate the
             feasibility of using iterative reconstructions in hepatic CT
             to improve the precision of Hounsfield unit quantification,
             which is the degree to which repeated measurements under
             unchanged conditions provide consistent results. MATERIALS
             AND METHODS: An anthropomorphic liver phantom with iodinated
             lesions designed to simulate the enhancement of
             hypervascular tumors during the late hepatic arterial phase
             was imaged, and images were reconstructed with both filtered
             back projection (FBP) and iterative reconstructions, such as
             adaptive statistical iterative reconstruction (ASIR) and
             model-based iterative reconstruction (MBIR). This protocol
             was further expanded into various dose levels, tube
             voltages, and slice thicknesses to investigate the effect of
             iterative reconstructions under all these conditions. The
             iodine concentrations of the lesions were quantified, with
             their precision calculated in terms of repeatability
             coefficient. RESULTS: ASIR reduced image noise by
             approximately 35%, and improved the quantitative precision
             by approximately 5%, compared with FBP. MBIR reduced noise
             by more than 65% and improved the precision by approximately
             25% compared with the routine protocol. MBIR consistently
             showed better precision across a thinner slice thickness,
             lower tube voltage, and larger patient, achieving the target
             precision level at a dose lower (≥ 40%) than that of FBP.
             CONCLUSION: ASIR blended with 50% of FBP indicated a
             moderate gain in quantitative precision compared with FBP
             but could achieve more with a higher percentage. A higher
             gain was achieved by MBIR. These findings may be used to
             reduce the dose required for reliable quantification and may
             further serve as a basis for protocol optimization in terms
             of iodine quantification.},
   Doi = {10.2214/AJR.12.9658},
   Key = {fds269234}
}

@article{fds269239,
   Author = {Segars, WP and Bond, J and Frush, J and Hon, S and Eckersley, C and Williams, CH and Feng, J and Tward, DJ and Ratnanather, JT and Miller,
             MI and Frush, D and Samei, E},
   Title = {Population of anatomically variable 4D XCAT adult phantoms
             for imaging research and optimization.},
   Volume = {40},
   Number = {4},
   Pages = {043701},
   Year = {2013},
   Month = {April},
   ISSN = {0094-2405},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/23556927},
   Abstract = {PURPOSE: The authors previously developed the 4D extended
             cardiac-torso (XCAT) phantom for multimodality imaging
             research. The XCAT consisted of highly detailed whole-body
             models for the standard male and female adult, including the
             cardiac and respiratory motions. In this work, the authors
             extend the XCAT beyond these reference anatomies by
             developing a series of anatomically variable 4D XCAT adult
             phantoms for imaging research, the first library of 4D
             computational phantoms. METHODS: The initial anatomy of each
             phantom was based on chest-abdomen-pelvis computed
             tomography data from normal patients obtained from the Duke
             University database. The major organs and structures for
             each phantom were segmented from the corresponding data and
             defined using nonuniform rational B-spline surfaces. To
             complete the body, the authors manually added on the head,
             arms, and legs using the original XCAT adult male and female
             anatomies. The structures were scaled to best match the age
             and anatomy of the patient. A multichannel large deformation
             diffeomorphic metric mapping algorithm was then used to
             calculate the transform from the template XCAT phantom (male
             or female) to the target patient model. The transform was
             applied to the template XCAT to fill in any unsegmented
             structures within the target phantom and to implement the 4D
             cardiac and respiratory models in the new anatomy. Each new
             phantom was refined by checking for anatomical accuracy via
             inspection of the models. RESULTS: Using these methods, the
             authors created a series of computerized phantoms with
             thousands of anatomical structures and modeling cardiac and
             respiratory motions. The database consists of 58 (35 male
             and 23 female) anatomically variable phantoms in total. Like
             the original XCAT, these phantoms can be combined with
             existing simulation packages to simulate realistic imaging
             data. Each new phantom contains parameterized models for the
             anatomy and the cardiac and respiratory motions and can,
             therefore, serve as a jumping point from which to create an
             unlimited number of 3D and 4D variations for imaging
             research. CONCLUSIONS: A population of phantoms that
             includes a range of anatomical variations representative of
             the public at large is needed to more closely mimic a
             clinical study or trial. The series of anatomically variable
             phantoms developed in this work provide a valuable resource
             for investigating 3D and 4D imaging devices and the effects
             of anatomy and motion in imaging. Combined with Monte Carlo
             simulation programs, the phantoms also provide a valuable
             tool to investigate patient-specific dose and image quality,
             and optimization for adults undergoing imaging
             procedures.},
   Doi = {10.1118/1.4794178},
   Key = {fds269239}
}

@article{fds269236,
   Author = {Samei, E and Murphy, S and Richard, S},
   Title = {Assessment of multi-directional MTF for breast
             tomosynthesis.},
   Journal = {Physics in Medicine and Biology},
   Volume = {58},
   Number = {5},
   Pages = {1649-1661},
   Year = {2013},
   Month = {March},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/23422248},
   Abstract = {A method was developed to assess the multi-directional
             modulation transfer function (MTF) of breast tomosynthesis
             imaging systems using a sphere phantom. The method was
             initially developed based on a simulation dataset.
             Projections were simulated for a uniform voxelized breast
             phantom with sphere inserts using a fluence modeled from a
             28 kVp beam incident upon an indirect flat-panel detector.
             Based on cascaded systems modeling, characteristic noise and
             blurring were added to each projection. The projections were
             reconstructed using a standard filtered backprojection
             technique, producing a 3D volume with an isotropic voxel
             size of 200 µm. ROIs that completely encompassed single
             spheres were extracted and conical regions were prescribed
             along the three major axes extending from the centroids.
             Pixels within the cones were used to form edge spread
             functions (ESFs), from which the directional MTFs were
             calculated. Binning size and conical range were adjusted to
             maximize the accuracy and to minimize the noise of the MTF.
             A method was further devised to remove out-of-plane
             artifacts from the ESF in the x-y plane. Finally, the method
             was applied to experimentally assess the directional MTF of
             a prototype tomosynthesis system. Comparisons of the
             sphere-based MTF along the different axes and the
             theoretical MTF yielded good agreement. A 30° angular cone
             and a 20 µm sampling were found to provide an ideal
             trade-off between the noise and accuracy of the measurement.
             The removal of artifacts in ESF yielded 'modified' MTFs that
             enabled a resolution-only characterization of the in-slice
             resolution of tomosynthesis. Drop-off frequencies in the x-
             and y-directional MTFs were 1.6 cycles mm(-1) and 1.5 cycles
             mm(-1), respectively. The presented method of separating the
             effective resolution and artifacts from the measured ESF was
             found experimentally implementable and is expected to
             facilitate the interpretation of MTF measurements in
             tomosynthesis.},
   Doi = {10.1088/0031-9155/58/5/1649},
   Key = {fds269236}
}

@article{fds269237,
   Author = {Solomon, JB and Li, X and Samei, E},
   Title = {Relating noise to image quality indicators in CT
             examinations with tube current modulation.},
   Journal = {AJR. American journal of roentgenology},
   Volume = {200},
   Number = {3},
   Pages = {592-600},
   Year = {2013},
   Month = {March},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/23436849},
   Abstract = {OBJECTIVE: Modern CT systems use surrogates of noise-noise
             index (NI) and quality reference effective tube current-time
             product (Q)-to infer the quality of images acquired using
             tube current modulation. This study aimed to determine the
             relationship between actual noise and these surrogates for
             two CT scanners from two different manufacturers. MATERIALS
             AND METHODS: Two phantoms (adult and 1-year-old child) were
             imaged on two CT scanners (64 and 128 MDCT) using a clinical
             range of NI (6-22) and Q (30-300 mA). Each scan was
             performed twice, and noise was measured in the mediastinum,
             lung, and abdomen using an image subtraction technique. The
             effect on noise from changing other imaging parameters, such
             as beam collimation, pitch, peak kilovoltage, slice
             thickness, FOV, reconstruction kernel or algorithm, and
             patient age category (adult or pediatric), was investigated.
             RESULTS: On the 64-MDCT scanner, noise increased linearly
             along with NI, with the slope affected by changing the
             anatomy of interest, peak kilovoltage, reconstruction
             algorithm, and convolution kernel. The noise-NI relationship
             was independent of phantom size, slice thickness, pitch,
             FOV, and beam width. On the 128-MDCT scanner, noise
             decreased nonlinearly along with increasing Q, slice
             thickness, and peak tube voltage. The noise-Q relationship
             also depended on anatomy of interest, phantom size, age
             selection, and reconstruction algorithm but was independent
             of pitch, FOV, and detector configuration. CONCLUSION: We
             established how noise changes with changing image quality
             indicators across a clinically relevant range of imaging
             parameters. This work can aid in optimizing protocols by
             targeting specific noise levels for different types of CT
             examinations.},
   Doi = {10.2214/AJR.12.8580},
   Key = {fds269237}
}

@article{fds269238,
   Author = {Wilson, JM and Christianson, OI and Richard, S and Samei,
             E},
   Title = {A methodology for image quality evaluation of advanced CT
             systems.},
   Volume = {40},
   Number = {3},
   Pages = {031908},
   Year = {2013},
   Month = {March},
   ISSN = {0094-2405},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/23464323},
   Abstract = {PURPOSE: This work involved the development of a
             phantom-based method to quantify the performance of tube
             current modulation and iterative reconstruction in modern
             computed tomography (CT) systems. The quantification
             included resolution, HU accuracy, noise, and noise texture
             accounting for the impact of contrast, prescribed dose,
             reconstruction algorithm, and body size. METHODS: A
             42-cm-long, 22.5-kg polyethylene phantom was designed to
             model four body sizes. Each size was represented by a
             uniform section, for the measurement of the noise-power
             spectrum (NPS), and a feature section containing various
             rods, for the measurement of HU and the task-based
             modulation transfer function (TTF). The phantom was scanned
             on a clinical CT system (GE, 750HD) using a range of tube
             current modulation settings (NI levels) and reconstruction
             methods (FBP and ASIR30). An image quality analysis program
             was developed to process the phantom data to calculate the
             targeted image quality metrics as a function of contrast,
             prescribed dose, and body size. RESULTS: The phantom
             fabrication closely followed the design specifications. In
             terms of tube current modulation, the tube current and
             resulting image noise varied as a function of phantom size
             as expected based on the manufacturer specification: From
             the 16- to 37-cm section, the HU contrast for each rod was
             inversely related to phantom size, and noise was relatively
             constant (<5% change). With iterative reconstruction, the
             TTF exhibited a contrast dependency with better performance
             for higher contrast objects. At low noise levels, TTFs of
             iterative reconstruction were better than those of FBP, but
             at higher noise, that superiority was not maintained at all
             contrast levels. Relative to FBP, the NPS of iterative
             reconstruction exhibited an ~30% decrease in magnitude and a
             0.1 mm(-1) shift in the peak frequency. CONCLUSIONS: Phantom
             and image quality analysis software were created for
             assessing CT image quality over a range of contrasts, doses,
             and body sizes. The testing platform enabled robust NPS,
             TTF, HU, and pixel noise measurements as a function of body
             size capable of characterizing the performance of
             reconstruction algorithms and tube current modulation
             techniques.},
   Doi = {10.1118/1.4791645},
   Key = {fds269238}
}

@article{fds269397,
   Author = {Boyce, SJ and McAdams, HP and Ravin, CE and Patz, EF and Washington, L and Martinez, S and Koweek, L and Samei, E},
   Title = {Preliminary evaluation of biplane correlation (BCI)
             stereographic imaging for lung nodule detection.},
   Journal = {Journal of Digital Imaging},
   Volume = {26},
   Number = {1},
   Pages = {109-114},
   Year = {2013},
   Month = {February},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/22422436},
   Abstract = {A biplane correlation (BCI) imaging system obtains images
             that can be viewed in stereo, thereby minimizing overlapping
             structures. This study investigated whether using
             stereoscopic visualization provides superior lung nodule
             detection compared to standard postero-anterior (PA) image
             display. Images were acquired at two oblique views of ±3°
             as well as at a standard PA position from 60 patients.
             Images were processed using optimal parameters and displayed
             on a stereoscopic display. The PA image was viewed in the
             standard format, while the oblique views were paired to
             provide a stereoscopic view of the subject. A preliminary
             observer study was performed with four radiologists who
             viewed and scored the PA image then viewed and scored the
             BCI stereoscopic image. The BCI stereoscopic viewing of lung
             nodules resulted in 71 % sensitivity and 0.31 positive
             predictive value (PPV) index compared to PA results of 86 %
             sensitivity and 0.26 PPV index. The sensitivity for lung
             nodule detection with the BCI stereoscopic system was
             reduced by 15 %; however, the total number of false
             positives reported was reduced by 35 % resulting in an
             improved PPV index of 20 %. The preliminary results indicate
             observer dependency in terms of relative advantage of either
             system in the detection of lung nodules, but overall
             equivalency of the two methods with promising potential for
             BCI as an adjunct diagnostic technique.},
   Doi = {10.1007/s10278-012-9466-6},
   Key = {fds269397}
}

@article{fds269385,
   Author = {Copple, C and Robertson, ID and Thrall, DE and Samei,
             E},
   Title = {Evaluation of two objective methods to optimize kVp and
             personnel exposure using a digital indirect flat panel
             detector and simulated veterinary patients.},
   Journal = {Veterinary Radiology & Ultrasound},
   Volume = {54},
   Number = {1},
   Pages = {9-16},
   Year = {2013},
   Month = {January},
   ISSN = {1058-8183},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/23293957},
   Abstract = {It is important to optimize digital radiographic technique
             settings for small animal imaging in order to maximize image
             quality while minimizing radiation exposure to personnel.
             The purpose of this study was to evaluate two objective
             methods for determining optimal kVp values for an indirect
             flat panel digital detector. One method considered both
             image quality and personnel exposure as endpoints and one
             considered only image quality. Phantoms simulated veterinary
             patients of varying thicknesses with lesions of varying
             sizes. Phantoms were exposed to a range of kVp values (60,
             81, 100, and 121), using different mAs settings for each
             phantom. Additionally, all phantoms were exposed to a
             standard test exposure of 100 kVp/2.5 mAs. Scattered
             radiation was recorded and used as a measure of personnel
             exposure. When personnel exposure was considered, a figure
             of merit was calculated as an endpoint of optimization. The
             optimal kVp value for each phantom was determined based on
             the highest signal difference-to-noise ratio with or without
             inclusion of the figure of merit. When personnel exposure
             was not considered, increasing kVp resulted in higher signal
             difference-to-noise ratios and personnel exposure increased
             when both patient thickness and kVp increased. Findings
             indicated that a single standard technique of 100 kVp/2.5
             mAs was only optimal for most medium-sized patients. Images
             of thinner patients should be made with a lower kVp. Very
             large patients require a higher kVp than 100 regardless of
             the optimization method used. Personnel exposure from
             optimized techniques was low and not expected to exceed
             annual occupational dose limits.},
   Language = {eng},
   Doi = {10.1111/j.1740-8261.2012.01989.x},
   Key = {fds269385}
}

@article{fds269221,
   Author = {Bond, J and Frush, D and Samei, E and Segars, WP},
   Title = {Simulation of Anatomical Texture in Voxelized XCAT
             Phantoms},
   Journal = {Proceedings of SPIE - The International Society for Optical
             Engineering},
   Volume = {8668},
   Year = {2013},
   ISSN = {0277-786X},
   url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000322002700020&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
   Doi = {10.1117/12.2008422},
   Key = {fds269221}
}

@article{fds269222,
   Author = {Solomon, J and Samei, E},
   Title = {Are Uniform Phantoms Sufficient to Characterize the
             Performance of Iterative Reconstruction in
             CT?},
   Journal = {Proceedings of SPIE - The International Society for Optical
             Engineering},
   Volume = {8668},
   Year = {2013},
   ISSN = {0277-786X},
   url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000322002700157&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
   Doi = {10.1117/12.2008378},
   Key = {fds269222}
}

@article{fds269223,
   Author = {Chen, B and Samei, E},
   Title = {Development of a phantom-based methodology for the
             assessment of quantification performance in
             CT},
   Journal = {Proceedings of SPIE - The International Society for Optical
             Engineering},
   Volume = {8668},
   Year = {2013},
   ISSN = {0277-786X},
   url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000322002700046&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
   Doi = {10.1117/12.2008481},
   Key = {fds269223}
}

@article{fds269224,
   Author = {Tian, X and Yin, Z and De Man and B and Samei, E},
   Title = {Projection-based Dose Metric: Accuracy Testing and
             Applications for CT Design},
   Journal = {Proceedings of SPIE - The International Society for Optical
             Engineering},
   Volume = {8668},
   Year = {2013},
   ISSN = {0277-786X},
   url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000322002700077&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
   Doi = {10.1117/12.2008051},
   Key = {fds269224}
}

@article{fds269231,
   Author = {Kiarashi, N and Sturgeon, GM and Nolte, LW and Lo, JY and III, JTD and Segars, WP and Samei, E},
   Title = {Development of matched virtual and physical breast phantoms
             based on patient data},
   Journal = {Proceedings of SPIE},
   Volume = {8668},
   Year = {2013},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.2008406},
   Abstract = {Physical phantoms are essential for the development,
             optimization, and clinical evaluation of x-ray systems.
             These phantoms are used for various tests such as quality
             assurance testing, system characterization, reconstruction
             evaluation, and dosimetry. They should ideally be capable of
             serving as ground truth for purposes such as virtual
             clinical trials. Currently, there is no anthropomorphic 3D
             physical phantom commercially available. We present our
             development of a new suite of physical breast phantoms based
             on real patient data. The phantoms were generated from the
             NURBS-based extended cardiac-torso (XCAT) breast phantoms,
             which were segmented from patient dedicated breast computed
             tomography data. High-resolution multi-material 3D printing
             technology was used to fabricate the physical models.
             Glandular tissue and skin were presented by the most
             radiographically dense photopolymer available to the
             printer, mimicking a 75% glandular tissue. Adipose tissue
             was presented by the least radiographically dense
             photopolymer, mimicking a 35% glandular tissue. The
             glandular equivalency was measured by comparing x-ray images
             of samples of the photopolymers available to the printer
             with those of breast tissue-equivalent materials. The
             mammographic projections and tomosynthesis reconstructed
             images of fabricated models showed great improvement over
             available phantoms, presenting a more realistic breast
             background. © 2013 SPIE.},
   Doi = {10.1117/12.2008406},
   Key = {fds269231}
}

@article{fds269225,
   Author = {Chung, H and Ikejimba, L and Kiarashi, N and Samei, E and Hoernig, M and Lo, JY},
   Title = {Estimating breast density with dual energy mammography: A
             simple model based on calibration phantoms},
   Journal = {Proceedings of SPIE},
   Volume = {8668},
   Year = {2013},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.2008398},
   Abstract = {Dual energy digital mammography has been used to suppress
             specific breast tissue, primarily for the purpose of iodine
             contrast-enhanced imaging. Another application of dual
             energy digital mammography is to estimate breast density, as
             defined by the fraction of glandular tissue, by suppressing
             adipose tissue. Adipose equivalent phantoms were used to
             derive the weighting factor for dual energy subtraction at
             2, 4, 6, and 8 cm thickness. For each thickness besides 8
             cm, measurements were taken over a range of densities (0,
             50, and 100%) and used for calibration measurements to model
             a density map. Once the density map was verified with
             uniform slabs, the density map was evaluated with 50/50 CIRS
             020 phantom at 2, 4, and 6 cm thickness and demonstrated the
             feasibility of using dual energy subtraction to estimate
             breast density on complex phantoms. © 2013
             SPIE.},
   Doi = {10.1117/12.2008398},
   Key = {fds269225}
}

@article{fds269229,
   Author = {Zhang, Y and Li, X and Segars, WP and Samei, E},
   Title = {Comparative dosimetry of radiography, tomosynthesis, and CT
             for chest imaging across 59 adult patients},
   Journal = {Proceedings of SPIE},
   Volume = {8668},
   Year = {2013},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.2008544},
   Abstract = {There are three main x-ray based modalities for imaging the
             thorax: radiography, tomosynthesis, and CT. CT provides
             perhaps the highest level of feature resolution but at
             notably higher radiation dose. To implement the ALARA (as
             low as reasonable achievable) principle in making an
             appropriate choice between standard chest projection
             imaging, tomosynthesis, and CT to achieve the lowest
             possible dose to patients, the effective doses and risk
             indices for each modality should be accurately known. In
             this study, we employed 59 computational anthropomorphic
             male and female extended cardiac-torso (XCAT) adult phantoms
             and a Monte Carlo simulation program (PENELOPE, version
             2006, Universitat de Barcelona, Spain). Effective dose and
             risk index was estimated for a clinical radiography system
             enabling to conduct chest radiography and tomosynthesis
             sweep (Definium 8000, Volume RAD, GE Healthcare) and a
             clinical CT system (LightSpeed VCT, GE Healthcare). It was
             found that the absolute effective dose and risk index
             increased greatly with increasing patient size for CT, while
             these two dose metrics only increased slightly for
             radiography and tomosynthesis. This suggests that it is
             important to specify patient size when comparing radiation
             dose across imaging modalities. © 2013 SPIE.},
   Doi = {10.1117/12.2008544},
   Key = {fds269229}
}

@article{fds269230,
   Author = {Li, X and Segars, WP and Samei, E},
   Title = {Organ dose in chest CT: Effect of modulation scheme on
             estimation accuracy},
   Journal = {Proceedings of SPIE},
   Volume = {8668},
   Year = {2013},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.2008505},
   Abstract = {The purpose of this study was to evaluate how different
             implementations of the tube current modulation (TCM)
             technology affect organ dose conversion factors in chest CT
             and how organ dose can be accurately estimated for various
             modulation schemes. Computational phantom of a normal-weight
             female patient was used. A method was developed to generate
             tube current (mA) modulation profiles based on the
             attenuation of the phantom, taking into account the geometry
             of the CT system as well as the x-ray energy spectrum and
             bowtie filtration in a CT scan. The mA for a given
             projection angle was calculated as a power-law function of
             the attenuation along this projection. The exponent of this
             function, termed modulation control strength, was varied
             from 0 to 1 to emulate the effects of different TCM schemes.
             Organ dose was estimated for a chest scan for each
             modulation scheme and was subsequently normalized by
             volume-weighted CT dose index (CTDIvol) to obtain conversion
             factors. The results showed that the conversion factors are
             second-order polynomial functions of the modulation control
             strength. The conversion factors established for a fixed-mA
             scan may be used to estimate organ dose in a TCM scan. For
             organs on the periphery of the scan coverage, the best
             accuracy is achieved when using CTDIvol computed from the
             average mA of the entire scan. For organs inside the scan
             coverage, the best accuracy is achieved when using CTDIvol
             computed from the volume-averaged mA values of all the axial
             slices containing the organ. © 2013 SPIE.},
   Doi = {10.1117/12.2008505},
   Key = {fds269230}
}

@article{fds269232,
   Author = {Kapadia, AJ and Lakshmanan, MN and Krishnamurthy, K and Sahbaee, P and Chawla, A and Wolter, S and Maccabe, K and Brady, D and Samei,
             E},
   Title = {Monte-Carlo simulations of a coded-aperture X-ray scatter
             imaging system for molecular imaging},
   Journal = {Proceedings of SPIE},
   Volume = {8668},
   Year = {2013},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.2008484},
   Abstract = {In this work, we demonstrate the ability to determine the
             material composition of a sample by measuring coherent
             scatter diffraction patterns generated using a
             coded-aperture x-ray scatter imaging (CAXSI) system. Most
             materials are known to exhibit unique diffraction patterns
             through coherent scattering of low-energy x-rays. However,
             clinical x-ray imagers typically discard scatter radiation
             as noise that degrades image quality. Through the addition
             of a coded aperture, the system can be sensitized to
             coherent scattered photons that carry information about the
             identity and location of the scattering material. In this
             work, we demonstrate this process using a Monte-Carlo
             simulation of a CAXSI system. A simulation of a CAXSI system
             was developed in GEANT4 with modified physics libraries to
             model coherent scatter diffraction patterns in materials.
             Simulated images were generated from 10 materials including
             plastics, hydrocarbons, and biological tissue. The materials
             were irradiated using collimated pencil- and fan-beams with
             energies of 160 kVp. The diffraction patterns were imaged
             using a simulated 2D detector and mathematically
             deconstructed using an analytical projection model that
             accounted for the known x-ray source spectrum. The
             deconstructed diffraction patterns were then matched with a
             library of known coherent scatter form-factors of different
             materials to determine the identity of the scatterer at
             different locations in the object. The results showed good
             agreement between the measured and known scatter patterns
             from the materials, demonstrating the ability to image and
             identify materials at different 3D locations within an
             object using a projection-based CAXSI system. © 2013
             SPIE.},
   Doi = {10.1117/12.2008484},
   Key = {fds269232}
}

@article{fds269235,
   Author = {Boyce, SJ and McAdams, HP and Ravin, CE and Jr, EFP and Washington, L and Martinez, S and Koweek, L and Samei, E},
   Title = {Preliminary evaluation of biplane correlation (BCI)
             stereographic imaging for lung nodule detection},
   Journal = {Journal of Digital Imaging},
   Volume = {26},
   Number = {1},
   Pages = {109-114},
   Year = {2013},
   ISSN = {0897-1889},
   url = {http://dx.doi.org/10.1007/s10278-012-9466-6},
   Abstract = {A biplane correlation (BCI) imaging system obtains images
             that can be viewed in stereo, thereby minimizing overlapping
             structures. This study investigated whether using
             stereoscopic visualization provides superior lung nodule
             detection compared to standard postero-anterior (PA) image
             display. Images were acquired at two oblique views of ±3 as
             well as at a standard PA position from 60 patients. Images
             were processed using optimal parameters and displayed on a
             stereoscopic display. The PA image was viewed in the
             standard format, while the oblique views were paired to
             provide a stereoscopic view of the subject. A preliminary
             observer study was performed with four radiologists who
             viewed and scored the PA image then viewed and scored the
             BCI stereoscopic image. The BCI stereoscopic viewing of lung
             nodules resulted in 71 % sensitivity and 0.31 positive
             predictive value (PPV) index compared to PA results of 86 %
             sensitivity and 0.26 PPV index. The sensitivity for lung
             nodule detection with the BCI stereoscopic system was
             reduced by 15 %; however, the total number of false
             positives reported was reduced by 35 % resulting in an
             improved PPV index of 20 %. The preliminary results indicate
             observer dependency in terms of relative advantage of either
             system in the detection of lung nodules, but overall
             equivalency of the two methods with promising potential for
             BCI as an adjunct diagnostic technique. © 2012 Society for
             Imaging Informatics in Medicine.},
   Language = {ENG},
   Doi = {10.1007/s10278-012-9466-6},
   Key = {fds269235}
}

@article{fds269386,
   Author = {Christianson, O and Li, X and Frush, D and Samei,
             E},
   Title = {Automated size-specific CT dose monitoring program:
             assessing variability in CT dose.},
   Journal = {Medical physics},
   Volume = {39},
   Number = {11},
   Pages = {7131-7139},
   Year = {2012},
   Month = {November},
   ISSN = {0094-2405},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/23127104},
   Keywords = {Algorithms • Automation • Body Size* • Humans
             • Radiation Dosage* • Tomography, X-Ray Computed
             • adverse effects • methods*},
   Abstract = {PURPOSE: The potential health risks associated with low
             levels of ionizing radiation have created a movement in the
             radiology community to optimize computed tomography (CT)
             imaging protocols to use the lowest radiation dose possible
             without compromising the diagnostic usefulness of the
             images. Despite efforts to use appropriate and consistent
             radiation doses, studies suggest that a great deal of
             variability in radiation dose exists both within and between
             institutions for CT imaging. In this context, the authors
             have developed an automated size-specific radiation dose
             monitoring program for CT and used this program to assess
             variability in size-adjusted effective dose from CT imaging.
             METHODS: The authors radiation dose monitoring program
             operates on an independent health insurance portability and
             accountability act compliant dosimetry server. Digital
             imaging and communication in medicine routing software is
             used to isolate dose report screen captures and scout images
             for all incoming CT studies. Effective dose conversion
             factors (k-factors) are determined based on the protocol and
             optical character recognition is used to extract the CT dose
             index and dose-length product. The patient's thickness is
             obtained by applying an adaptive thresholding algorithm to
             the scout images and is used to calculate the size-adjusted
             effective dose (ED(adj)). The radiation dose monitoring
             program was used to collect data on 6351 CT studies from
             three scanner models (GE Lightspeed Pro 16, GE Lightspeed
             VCT, and GE Definition CT750 HD) and two institutions over a
             one-month period and to analyze the variability in ED(adj)
             between scanner models and across institutions. RESULTS: No
             significant difference was found between computer
             measurements of patient thickness and observer measurements
             (p = 0.17), and the average difference between the two
             methods was less than 4%. Applying the size correction
             resulted in ED(adj) that differed by up to 44% from
             effective dose estimates that were not adjusted by patient
             size. Additionally, considerable differences were noted in
             ED(adj) distributions between scanners, with scanners
             employing iterative reconstruction exhibiting significantly
             lower ED(adj) (range: 9%-64%). Finally, a significant
             difference (up to 59%) in ED(adj) distributions was observed
             between institutions, indicating the potential for dose
             reduction. CONCLUSIONS: The authors developed a robust
             automated size-specific radiation dose monitoring program
             for CT. Using this program, significant differences in
             ED(adj) were observed between scanner models and across
             institutions. This new dose monitoring program offers a
             unique tool for improving quality assurance and
             standardization both within and across institutions.},
   Language = {eng},
   Doi = {10.1118/1.4761871},
   Key = {fds269386}
}

@article{fds269387,
   Author = {Lin, Y and Luo, H and Dobbins, JT and Page McAdams and H and Wang, X and Sehnert, WJ and Barski, L and Foos, DH and Samei,
             E},
   Title = {An image-based technique to assess the perceptual quality of
             clinical chest radiographs.},
   Journal = {Medical physics},
   Volume = {39},
   Number = {11},
   Pages = {7019-7031},
   Year = {2012},
   Month = {November},
   ISSN = {0094-2405},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/23127093},
   Keywords = {Humans • Pilot Projects • Quality Control •
             Radiography, Thoracic • standards*},
   Abstract = {PURPOSE: Current clinical image quality assessment
             techniques mainly analyze image quality for the imaging
             system in terms of factors such as the capture system
             modulation transfer function, noise power spectrum,
             detective quantum efficiency, and the exposure technique.
             While these elements form the basic underlying components of
             image quality, when assessing a clinical image, radiologists
             seldom refer to these factors, but rather examine several
             specific regions of the displayed patient images, further
             impacted by a particular image processing method applied, to
             see whether the image is suitable for diagnosis. In this
             paper, the authors developed a novel strategy to simulate
             radiologists' perceptual evaluation process on actual
             clinical chest images. METHODS: Ten regional based
             perceptual attributes of chest radiographs were determined
             through an observer study. Those included lung grey level,
             lung detail, lung noise, rib-lung contrast, rib sharpness,
             mediastinum detail, mediastinum noise, mediastinum
             alignment, subdiaphragm-lung contrast, and subdiaphragm
             area. Each attribute was characterized in terms of a
             physical quantity measured from the image algorithmically
             using an automated process. A pilot observer study was
             performed on 333 digital chest radiographs, which included
             179 PA images with 10:1 ratio grids (set 1) and 154 AP
             images without grids (set 2), to ascertain the correlation
             between image perceptual attributes and physical
             quantitative measurements. To determine the acceptable range
             of each perceptual attribute, a preliminary quality
             consistency range was defined based on the preferred 80% of
             images in set 1. Mean value difference (μ(1) - μ(2)) and
             variance ratio (σ(1) (2)/σ(2) (2)) were investigated to
             further quantify the differences between the selected two
             image sets. RESULTS: The pilot observer study demonstrated
             that our regional based physical quantity metrics of chest
             radiographs correlated very well with their corresponding
             perceptual attributes. The distribution comparisons, mean
             value difference estimations, and variance ratio estimations
             of each physical quantity between sets of images from two
             different techniques matched our expectation that the image
             quality of set 1 should be better than that of set 2.
             CONCLUSIONS: The measured physical quantities provide a
             robust reflection of perceptual image quality in clinical
             images. The methodology can be readily applied for automated
             evaluation of perceptual image quality in clinical chest
             radiographs.},
   Language = {eng},
   Doi = {10.1118/1.4760886},
   Key = {fds269387}
}

@article{fds269389,
   Author = {Li, X and Samei, E and Williams, CH and Segars, WP and Tward, DJ and Miller, MI and Ratnanather, JT and Paulson, EK and Frush,
             DP},
   Title = {Effects of protocol and obesity on dose conversion factors
             in adult body CT.},
   Journal = {Medical physics},
   Volume = {39},
   Number = {11},
   Pages = {6550-6571},
   Year = {2012},
   Month = {November},
   ISSN = {0094-2405},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/23127050},
   Keywords = {Adult • Female • Humans • Male • Middle
             Aged • Monte Carlo Method • Neoplasms,
             Radiation-Induced • Obesity* • Phantoms, Imaging
             • Radiation Dosage* • Radiometry • Risk
             • Tomography, X-Ray Computed • Whole-Body
             Irradiation • adverse effects • etiology •
             methods*},
   Abstract = {PURPOSE: In computed tomography (CT), organ dose, effective
             dose, and risk index can be estimated from volume-weighted
             CT dose index (CTDI(vol)) or dose-length product (DLP) using
             conversion coefficients. Studies have investigated how these
             coefficients vary across scanner models, scan parameters,
             and patient size. However, their variability across CT
             protocols has not been systematically studied. Furthermore,
             earlier studies of the effect of patient size have not
             included obese individuals, which currently represent more
             than one-third of U.S. adults. The purpose of this study was
             to assess the effects of protocol and obesity on dose and
             risk conversion coefficients in adult body CT. METHODS:
             Whole-body computational phantoms were created from clinical
             CT images of six adult patients (three males, three
             females), representing normal-weight patients and patients
             of three obesity classes. Body CT protocols at our
             institution were selected and categorized into ten
             examination categories based on anatomical region examined.
             A validated Monte Carlo program was used to estimate organ
             dose. Organ dose estimates were normalized by CTDI(vol) and
             size-specific dose estimate (SSDE) to obtain organ dose
             conversion coefficients (denoted as h and h(ss) factors,
             respectively). Assuming each phantom to be 20, 40, and 60
             years old, effective dose and risk index were calculated and
             normalized by DLP to obtain effective dose and risk index
             conversion coefficients (denoted as k and q factors,
             respectively). Coefficient of variation was used to quantify
             the variability of each conversion coefficient across
             examination categories. The effect of obesity was assessed
             by comparing each obese phantom with the normal-weight
             phantom of the same gender. RESULTS: For a given organ, the
             variability of h factor across examination categories that
             encompassed the entire organ volume was generally within
             15%. However, k factor varied more across examination
             categories (15%-27%). For all three ages, the variability of
             q factor was small for male (<10%), but large for female
             phantoms (21%-43%). Relative to the normal-weight phantoms,
             the reduction in h factor (an average across fully
             encompassed organs) was 17%-42%, 17%-40%, and 51%-63% for
             obese-class-I, obese-class-II, and obese-class-III phantoms,
             respectively. h(ss) factor was not independent of patient
             diameter and generally decreased with increasing obesity.
             Relative to the normal-weight phantoms, the reduction in k
             factor was 12%-40%, 14%-46%, and 44%-59% for obese-class-I,
             obese-class-II, and obese-class-III phantoms, respectively.
             The respective reduction in q factor was 11%-36%, 17%-42%,
             and 48%-59% at 20 years of age and similar at other ages.
             CONCLUSIONS: In adult body CT, dose to an organ fully
             encompassed by the primary radiation beam can be estimated
             from CTDI(vol) using a protocol-independent conversion
             coefficient. However, fully encompassed organs only account
             for 50% ± 19% of k factor and 46% ± 24% of q factor. Dose
             received by partially encompassed organs is also
             substantial. To estimate effective dose and risk index from
             DLP, it is necessary to use conversion coefficients specific
             to the anatomical region examined. Obesity has a significant
             effect on dose and risk conversion coefficients, which
             cannot be predicted using body diameter alone.
             SSDE-normalized organ dose is not independent of diameter.
             SSDE itself generally overestimates organ dose for obese
             patients.},
   Language = {eng},
   Doi = {10.1118/1.4754584},
   Key = {fds269389}
}

@article{fds214916,
   Author = {E Samei and X Li and B Chen and R Reiman},
   Title = {THE EFFECT OF DOSE HETEROGENEITY ON RADIATION RISK IN
             MEDICAL IMAGING.},
   Journal = {Radiation protection dosimetry},
   Year = {2012},
   Month = {October},
   ISSN = {1742-3406},
   url = {http://dx.doi.org/10.1093/rpd/ncs275},
   Abstract = {The current estimations of risk associated with medical
             imaging procedures rely on assessing the organ dose via
             direct measurements or simulation. The dose to each organ is
             assumed to be homogeneous. To take into account the
             differences in radiation sensitivities, the mean organ doses
             are weighted by a corresponding tissue-weighting
             coefficients provided by ICRP to calculate the effective
             dose, which has been used as a surrogate of radiation risk.
             However, those coefficients were derived under the
             assumption of a homogeneous dose distribution within each
             organ. That assumption is significantly violated in most
             medical-imaging procedures. In helical chest CT, for
             example, superficial organs (e.g. breasts) demonstrate a
             heterogeneous dose distribution, whereas organs on the
             peripheries of the irradiation field (e.g. liver) might
             possess a discontinuous dose profile. Projection radiography
             and mammography involve an even higher level of organ dose
             heterogeneity spanning up to two orders of magnitude. As
             such, mean dose or point measured dose values do not reflect
             the maximum energy deposited per unit volume of the organ.
             In this paper, the magnitude of the dose heterogeneity in
             both CT and projection X-ray imaging was reported, using
             Monte Carlo methods. The lung dose demonstrated factors of
             1.7 and 2.2 difference between the mean and maximum dose for
             chest CT and radiography, respectively. The corresponding
             values for the liver were 1.9 and 3.5. For mammography and
             breast tomosynthesis, the difference between mean glandular
             dose and maximum glandular dose was 3.1. Risk models based
             on the mean dose were found to provide a reasonable
             reflection of cancer risk. However, for leukaemia, they were
             found to significantly under-represent the risk when the
             organ dose distribution is heterogeneous. A systematic study
             is needed to develop a risk model for heterogeneous dose
             distributions.},
   Language = {ENG},
   Doi = {10.1093/rpd/ncs275},
   Key = {fds214916}
}

@article{fds269390,
   Author = {Solomon, JB and Christianson, O and Samei, E},
   Title = {Quantitative comparison of noise texture across CT scanners
             from different manufacturers.},
   Journal = {Medical physics},
   Volume = {39},
   Number = {10},
   Pages = {6048-6055},
   Year = {2012},
   Month = {October},
   ISSN = {0094-2405},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/23039643},
   Keywords = {Image Processing, Computer-Assisted • Phantoms, Imaging
             • Quality Control • Tomography, X-Ray Computed
             • instrumentation*},
   Abstract = {PURPOSE: To quantitatively compare noise texture across
             computed tomography (CT) scanners from different
             manufacturers using the noise power spectrum (NPS). METHODS:
             The American College of Radiology CT accreditation phantom
             (Gammex 464, Gammex, Inc., Middleton, WI) was imaged on two
             scanners: Discovery CT 750HD (GE Healthcare, Waukesha, WI),
             and SOMATOM Definition Flash (Siemens Healthcare, Germany),
             using a consistent acquisition protocol (120 kVp,
             0.625∕0.6 mm slice thickness, 250 mAs, and 22 cm field of
             view). Images were reconstructed using filtered
             backprojection and a wide selection of reconstruction
             kernels. For each image set, the 2D NPS were estimated from
             the uniform section of the phantom. The 2D spectra were
             normalized by their integral value, radially averaged, and
             filtered by the human visual response function. A systematic
             kernel-by-kernel comparison across manufacturers was
             performed by computing the root mean square difference
             (RMSD) and the peak frequency difference (PFD) between the
             NPS from different kernels. GE and Siemens kernels were
             compared and kernel pairs that minimized the RMSD and |PFD|
             were identified. RESULTS: The RMSD (|PFD|) values between
             the NPS of GE and Siemens kernels varied from 0.01 mm(2)
             (0.002 mm(-1)) to 0.29 mm(2) (0.74 mm(-1)). The GE kernels
             "Soft," "Standard," "Chest," and "Lung" closely matched the
             Siemens kernels "B35f," "B43f," "B41f," and "B80f" (RMSD <
             0.05 mm(2), |PFD| < 0.02 mm(-1), respectively). The GE
             "Bone," "Bone+," and "Edge" kernels all matched most closely
             with Siemens "B75f" kernel but with sizeable RMSD and |PFD|
             values up to 0.18 mm(2) and 0.41 mm(-1), respectively. These
             sizeable RMSD and |PFD| values corresponded to visually
             perceivable differences in the noise texture of the images.
             CONCLUSIONS: It is possible to use the NPS to quantitatively
             compare noise texture across CT systems. The degree to which
             similar texture across scanners could be achieved varies and
             is limited by the kernels available on each
             scanner.},
   Language = {eng},
   Doi = {10.1118/1.4752209},
   Key = {fds269390}
}

@article{fds269391,
   Author = {Lungren, MP and Samei, E and Barnhart, H and McAdams, HP and Leder, RA and Christensen, JD and Wylie, JD and Tan, JW and Li, X and Hurwitz,
             LM},
   Title = {Gray-scale inversion radiographic display for the detection
             of pulmonary nodules on chest radiographs.},
   Journal = {Clinical Imaging},
   Volume = {36},
   Number = {5},
   Pages = {515-521},
   Year = {2012},
   Month = {September},
   ISSN = {1873-4499},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/22920355},
   Abstract = {The purpose of this study was to investigate gray-scale
             inversion in nodule detection on chest radiography.
             Simulated nodules were superimposed randomly onto normal
             chest radiographs. Six radiologists interpreted 144 chest
             radiographs during three reading sessions: traditional
             presentation, inverted gray-scale, and a choice session
             allowing use of traditional and gray-scale inverted views.
             Sensitivity and specificity were used to assess accuracy
             based on presence or absence of a nodule. Gray-scale
             inversion and choice display sessions resulted in
             significantly higher nodule detection specificity and
             decreased sensitivity compared to traditional display.
             Gray-scale inversion may decrease false-positive nodule
             findings during chest X-ray interpretation.},
   Language = {eng},
   Doi = {10.1016/j.clinimag.2012.01.009},
   Key = {fds269391}
}

@article{fds269394,
   Author = {McCollough, CH and Chen, GH and Kalender, W and Leng, S and Samei, E and Taguchi, K and Wang, G and Yu, L and Pettigrew, RI},
   Title = {Achieving routine submillisievert CT scanning: report from
             the summit on management of radiation dose in
             CT.},
   Journal = {Radiology},
   Volume = {264},
   Number = {2},
   Pages = {567-580},
   Year = {2012},
   Month = {August},
   ISSN = {1527-1315},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/22692035},
   Keywords = {Age Factors • Algorithms • Female • Humans
             • Male • Radiation Dosage* • Radiation
             Protection • Radiographic Image Interpretation,
             Computer-Assisted • Risk Factors • Sex Factors
             • Tomography Scanners, X-Ray Computed •
             Tomography, X-Ray Computed • methods • methods*
             • trends*},
   Abstract = {This Special Report presents the consensus of the Summit on
             Management of Radiation Dose in Computed Tomography (CT)
             (held in February 2011), which brought together participants
             from academia, clinical practice, industry, and regulatory
             and funding agencies to identify the steps required to
             reduce the effective dose from routine CT examinations to
             less than 1 mSv. The most promising technologies and methods
             discussed at the summit include innovations and developments
             in x-ray sources; detectors; and image reconstruction, noise
             reduction, and postprocessing algorithms. Access to raw
             projection data and standard data sets for algorithm
             validation and optimization is a clear need, as is the need
             for new, clinically relevant metrics of image quality and
             diagnostic performance. Current commercially available
             techniques such as automatic exposure control, optimization
             of tube potential, beam-shaping filters, and dynamic z-axis
             collimators are important, and education to successfully
             implement these methods routinely is critically needed.
             Other methods that are just becoming widely available, such
             as iterative reconstruction, noise reduction, and
             postprocessing algorithms, will also have an important role.
             Together, these existing techniques can reduce dose by a
             factor of two to four. Technical advances that show
             considerable promise for additional dose reduction but are
             several years or more from commercial availability include
             compressed sensing, volume of interest and interior
             tomography techniques, and photon-counting detectors. This
             report offers a strategic roadmap for the CT user and
             research and manufacturer communities toward routinely
             achieving effective doses of less than 1 mSv, which is well
             below the average annual dose from naturally occurring
             sources of radiation.},
   Language = {eng},
   Doi = {10.1148/radiol.12112265},
   Key = {fds269394}
}

@article{fds269399,
   Author = {Pollard, BJ and Samei, E and Chawla, AS and Beam, C and Heyneman, LE and Koweek, LMH and Martinez-Jimenez, S and Washington, L and Hashimoto,
             N and McAdams, HP},
   Title = {The effects of ambient lighting in chest radiology reading
             rooms.},
   Journal = {Journal of Digital Imaging},
   Volume = {25},
   Number = {4},
   Pages = {520-526},
   Year = {2012},
   Month = {August},
   ISSN = {1618-727X},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/22349990},
   Keywords = {Area Under Curve • Data Display* • Humans •
             Lighting • Lung • Lung Neoplasms • ROC Curve
             • Radiographic Image Enhancement • Reproducibility
             of Results • Sensitivity and Specificity • Visual
             Perception* • diagnosis* • methods* •
             radiography*},
   Abstract = {Under typical dark chest radiography reading room
             conditions, a radiologist's pupils contract and dilate as
             their visual focus intermittently shifts between the high
             luminance monitor and the darker background wall, resulting
             in increased visual fatigue and degradation of diagnostic
             performance. A controlled increase of ambient lighting may
             minimize these visual adjustments and potentially improve
             comfort and accuracy. This study was designed to determine
             the effect of a controlled increase of ambient lighting on
             chest radiologist nodule detection performance. Four chest
             radiologists read 100 radiographs (50 normal and 50
             containing a subtle nodule) under low (E=1 lx) and elevated
             (E=50 lx) ambient lighting levels on a DICOM-calibrated,
             medical-grade liquid crystal display. Radiologists were
             asked to identify nodule locations and rate their detection
             confidence. A receiver operating characteristic (ROC)
             analysis of radiologist results was performed and area under
             ROC curve (AUC) values calculated for each ambient lighting
             level. Additionally, radiologist selection times under both
             illuminance conditions were determined. Average AUC values
             did not significantly differ (p>0.05) between ambient
             lighting levels (estimated mean difference=-0.03; 95% CI,
             (-0.08, 0.03)). Average selection times decreased or
             remained constant with increased illuminance. The most
             considerable decreases occurred for false positive
             identification times (35.4±18.8 to 26.2±14.9 s) and true
             positive identification times (29.7±18.3 to 24.5±15.5 s).
             No performance differences were statistically significant.
             Study findings suggest that a controlled increase of ambient
             lighting within darkly lit chest radiology reading rooms, to
             a level more suitable for performance of common radiological
             tasks, does not appear to have a statistically significant
             effect on nodule detection performance.},
   Language = {eng},
   Doi = {10.1007/s10278-012-9459-5},
   Key = {fds269399}
}

@article{fds269402,
   Author = {Husarik, DB and Marin, D and Samei, E and Richard, S and Chen, B and Jaffe,
             TA and Bashir, MR and Nelson, RC},
   Title = {Radiation dose reduction in abdominal computed tomography
             during the late hepatic arterial phase using a model-based
             iterative reconstruction algorithm: how low can we
             go?},
   Journal = {Investigative Radiology},
   Volume = {47},
   Number = {8},
   Pages = {468-474},
   Year = {2012},
   Month = {August},
   ISSN = {1536-0210},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/22717881},
   Keywords = {Algorithms • Computer Simulation • Diagnosis,
             Computer-Assisted • Dose-Response Relationship,
             Radiation • Hepatic Artery* • Humans • Image
             Enhancement • Image Processing, Computer-Assisted
             • Phantoms, Imaging • Radiography, Abdominal
             • Tomography, X-Ray Computed • instrumentation*
             • methods},
   Abstract = {OBJECTIVE: The aim of this study was to compare the image
             quality of abdominal computed tomography scans in an
             anthropomorphic phantom acquired at different radiation dose
             levels where each raw data set is reconstructed with both a
             standard convolution filtered back projection (FBP) and a
             full model-based iterative reconstruction (MBIR) algorithm.
             MATERIALS AND METHODS: An anthropomorphic phantom in 3 sizes
             was used with a custom-built liver insert simulating late
             hepatic arterial enhancement and containing hypervascular
             liver lesions of various sizes. Imaging was performed on a
             64-section multidetector-row computed tomography scanner
             (Discovery CT750 HD; GE Healthcare, Waukesha, WI) at 3
             different tube voltages for each patient size and 5
             incrementally decreasing tube current-time products for each
             tube voltage. Quantitative analysis consisted of
             contrast-to-noise ratio calculations and image noise
             assessment. Qualitative image analysis was performed by 3
             independent radiologists rating subjective image quality and
             lesion conspicuity. RESULTS: Contrast-to-noise ratio was
             significantly higher and mean image noise was significantly
             lower on MBIR images than on FBP images in all patient
             sizes, at all tube voltage settings, and all radiation dose
             levels (P < 0.05). Overall image quality and lesion
             conspicuity were rated higher for MBIR images compared with
             FBP images at all radiation dose levels. Image quality and
             lesion conspicuity on 25% to 50% dose MBIR images were rated
             equal to full-dose FBP images. CONCLUSION: This phantom
             study suggests that depending on patient size, clinically
             acceptable image quality of the liver in the late hepatic
             arterial phase can be achieved with MBIR at approximately
             50% lower radiation dose compared with FBP.},
   Language = {eng},
   Doi = {10.1097/RLI.0b013e318251eafd},
   Key = {fds269402}
}

@article{fds269392,
   Author = {Richard, S and Husarik, DB and Yadava, G and Murphy, SN and Samei,
             E},
   Title = {Towards task-based assessment of CT performance: system and
             object MTF across different reconstruction
             algorithms.},
   Journal = {Medical physics},
   Volume = {39},
   Number = {7},
   Pages = {4115-4122},
   Year = {2012},
   Month = {July},
   ISSN = {0094-2405},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/22830744},
   Keywords = {Algorithms* • Humans • Phantoms, Imaging •
             Radiographic Image Enhancement • Radiographic Image
             Interpretation, Computer-Assisted • Reproducibility of
             Results • Sensitivity and Specificity •
             Tomography, X-Ray Computed • instrumentation •
             methods*},
   Abstract = {PURPOSE: To investigate a measurement method for evaluating
             the resolution properties of CT imaging systems across
             reconstruction algorithms, dose, and contrast. METHODS: An
             algorithm was developed to extract the task-based modulation
             transfer function (MTF) from disk images generated from the
             rod inserts in the ACR phantom (model 464 Gammex, WI). These
             inserts are conventionally employed for HU accuracy
             assessment. The edge of the disk objects was analyzed to
             determine the edge-spread function, which was differentiated
             to yield the line-spread function and Fourier-transformed to
             generate the object-specific MTF for task-based assessment,
             denoted MTF(Task). The proposed MTF measurement method was
             validated against the conventional wire technique and
             further applied to measure the MTF of CT images
             reconstructed with an adaptive statistical iterative
             algorithm (ASIR) and a model-based iterative (MBIR)
             algorithm. Results were further compared to the standard
             filtered back projection (FBP) algorithm. Measurements were
             performed and compared across different doses and contrast
             levels to ascertain the MTF(Task) dependencies on those
             factors. RESULTS: For the FBP reconstructed images, the
             MTF(Task) measured with the inserts were the same as the MTF
             measured from the wire-based method. For the ASIR and MBIR
             data, the MTF(Task) using the high contrast insert was
             similar to the wire-based MTF and equal or superior to that
             of FBP. However, results for the MTF(Task) measured using
             the low-contrast inserts, the MTF(Task) for ASIR and MBIR
             data was lower than for the FBP, which was constant
             throughout all measurements. Similarly, as a function of mA,
             the MTF(Task) for ASIR and MBIR varied as a function of
             noise--with MTF(Task) being proportional to mA. Overall
             greater variability of MTF(Task) across dose and contrast
             was observed for MBIR than for ASIR. CONCLUSIONS: This
             approach provides a method for assessing the task-based MTF
             of a CT system using conventional and iterative
             reconstructions. Results demonstrated that the
             object-specific MTF can vary as a function of dose and
             contrast. The analysis highlighted the paradigm shift for
             iterative reconstructions when compared to FBP, where
             iterative reconstructions generally offer superior noise
             performance but with varying resolution as a function of
             dose and contrast. The MTF(Task) generated by this method is
             expected to provide a more comprehensive assessment of image
             resolution across different reconstruction algorithms and
             imaging tasks.},
   Language = {eng},
   Doi = {10.1118/1.4725171},
   Key = {fds269392}
}

@article{fds269246,
   Author = {Nelson, J and Christianson, O and Harkness, B and Madsen, M and Mah, E and Thomas, S and Zaidi, H and Samei, E},
   Title = {Nuclear Medicine Uniformity Assessment Using 2D Noise Power
             Spectrum},
   Journal = {Medical physics},
   Volume = {39},
   Number = {6},
   Pages = {3621-3621},
   Year = {2012},
   Month = {June},
   ISSN = {0094-2405},
   url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000308905804102&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
   Abstract = {Nuclear medicine quality control programs require daily
             evaluation for the presence of potential non-uniformities by
             commonly utilizing a traditional pixel value-based
             assessment (Integral CFOVUniformity). While this method
             effectively captures regional non- uniformities in the
             image, it does not adequately reflect subtle periodic
             structures that are visually apparent and clinically
             unacceptable, therefore requiring the need for additional
             visual inspection of the image. The goal of this project was
             to develop a new uniformity assessment metric by
             targetingstructural patterns and more closely correlating
             with visual inspection.The new quantitative uniformity
             assessment metric is based on the 2D Noise Power Spectrum
             (NPS). A full 2D NPS was performed on each image. The NPS
             was thresholded to remove quantum noise and further filtered
             by the visual response function. A score, the Structure
             Noise Index (SNI), was then applied to each based on the
             average magnitude of the structured noise in the processed
             image. To verify the validity of the new metric, 50 daily
             uniformity images with varying degrees of visual structured
             and non-structured non-uniformity were scored by 5 expert
             nuclear medicine physicists. The correlation between the
             visual score and SNI were assessed. The Integral CFOV was
             also compared against the visual score.Our new SNI
             assessment metric compared to the Integral CFOV showed in
             increase in sensitivity from 67% to 100% in correctly
             identifying structured non-uniformities. The overall
             positive predictive value also increased from 55% to 72%.Our
             new uniformity metric correlates much more closely with
             visual assessment of structured non- uniform NM images than
             the traditional pixel-based method. Using this new metric in
             conjunction with the traditional pixel value-based
             assessment will allow a more accurate quantitative
             assessment of nuclear medicineuniformity.},
   Doi = {10.1118/1.4734700},
   Key = {fds269246}
}

@article{fds269248,
   Author = {Wilson, JM and Christianson, O and Chen, B and Winslow, J and Samei,
             E},
   Title = {MA Modulation and Iterative Reconstruction: Evaluation Using
             a New CT Phantom},
   Journal = {Medical physics},
   Volume = {39},
   Number = {6},
   Pages = {4015-4015},
   Year = {2012},
   Month = {June},
   ISSN = {0094-2405},
   url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000308905805833&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
   Doi = {10.1118/1.4736378},
   Key = {fds269248}
}

@article{fds269252,
   Author = {McNitt-Gray, M and Noo, F and Fessler, J and Samei,
             E},
   Title = {Limits of Dose Reduction in CT: Where Are They and How Will
             We Know When We Get There?},
   Journal = {Medical physics},
   Volume = {39},
   Number = {6},
   Pages = {3868-3868},
   Year = {2012},
   Month = {June},
   ISSN = {0094-2405},
   url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000308905805255&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
   Abstract = {Radiation Dose continues to be a concern with respect to all
             diagnostic imaging using ionizing radiation, but especially
             so with CT imaging. We have always known how to reduce
             radiation dose in CT - for example, simply turning down the
             system output (e.g. reduce mAs). What we have not been able
             to do is to simultaneously reduce dose and maintain
             "diagnostic image quality". Many recent technical
             developments have appeared, and will continue to appear,
             that will allow users to reduce radiation dose in CT while
             "maintaining image quality". However, this last term is
             ill-defined and current metrics of image quality are not
             very applicable to actual clinical practice. The purpose of
             this symposium is to: (a) describe several current and
             possible future radiation dose reduction methods and the
             magnitude of their potential for dose reduction, (b) some
             description of what "diagnostic image quality" means, the
             effects that dose reductions methods have on this property,
             description of some metrics that may help us assess this
             property quantitatively and this information can be used to
             guide how low radiation doses can be reduced.1. Understand
             both conventional and emerging radiation dose reduction
             methods in CT. 2. Understand the implications on diagnostic
             image quality for each radiation dose reduction method. 3.
             Understand some of the issues in evaluating how much
             radiation dose can be reduced and still accomplish a
             diagnostic imaging task.},
   Doi = {10.1118/1.4735793},
   Key = {fds269252}
}

@article{fds269254,
   Author = {Winslow, J and Wilson, J and Christianson, O and Samei,
             E},
   Title = {CT QA Revisited in Context of Tube Current Modulation and
             Iterative Reconstruction},
   Journal = {Medical physics},
   Volume = {39},
   Number = {6},
   Pages = {3606-3606},
   Year = {2012},
   Month = {June},
   ISSN = {0094-2405},
   url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000308905804042&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
   Doi = {10.1118/1.4734638},
   Key = {fds269254}
}

@article{fds269256,
   Author = {Li, X and Samei, E and Solomon, J and Frush, D},
   Title = {Defining Performance-Based, Size-Specific, Optimized
             Protocols for Pediatric CT},
   Journal = {Medical physics},
   Volume = {39},
   Number = {6},
   Pages = {4014-4015},
   Year = {2012},
   Month = {June},
   ISSN = {0094-2405},
   url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000308905805831&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
   Doi = {10.1118/1.4736376},
   Key = {fds269256}
}

@article{fds269258,
   Author = {Christianson, O and Frush, D and Samei, E},
   Title = {Comparison of Automated Methods to Measure Patient Size for
             Dose-Monitoring in Computed Tomography},
   Journal = {Medical physics},
   Volume = {39},
   Number = {6},
   Pages = {3940-3940},
   Year = {2012},
   Month = {June},
   ISSN = {0094-2405},
   url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000308905805537&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
   Doi = {10.1118/1.4736077},
   Key = {fds269258}
}

@article{fds269259,
   Author = {Choudhury, KR and Tian, R and Li, X and Samei, E},
   Title = {Comparison of Risks for Two Medical Imaging
             Procedures},
   Journal = {Medical physics},
   Volume = {39},
   Number = {6},
   Pages = {3635-3635},
   Year = {2012},
   Month = {June},
   ISSN = {0094-2405},
   url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000308905804163&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
   Abstract = {Radiologists may need to decide which type of image
             procedure is most appropriate for a particular patient. One
             factor relevant in making this decision is the relative risk
             of secondary cancers due to each relevant procedure.
             Differences in the risk posed by each method are not just
             due to the total radiation dose imparted by each procedure,
             but also the distribution of absorbed dose across various
             organs in the imaging procedure. Two imaging procedures with
             the same total radiation dose may pose different risks of
             differential sensitivity to radiation across organs.New
             methods of radiation dosimetry enable us to estimate the
             dose distribution across organs in individual patients. We
             propose a measure of the relative risk of two medical
             imaging procedures derived from the hazard function of
             cancer incidence. The relative risk measure is shown to
             approximately equal to a weighted sum of the dose difference
             in each organ. The weights are proportional to organ
             specific incidence rates. The measure is also sensitive to
             factors such as the patient's age at exposure to radiation,
             the attained age and gender, as well as the incidence
             characteristics of the population to which the patient
             belongs. We propose to quantify the effects of these factors
             using information from publically available SEER database
             for US based patients as well as the LSS study of atomic
             bomb survivors. The method is illustrated by application to
             a study comparing chest and abdominal CT scans for a group
             of pediatric patients.Fig. 1 shows higher absolute relative
             risk for those exposed at younger ages, with chest scans
             being riskier for females while abdominal scans were riskier
             for males. At higher ages, the relative risk is
             approximately equal.Relative risks can quantify risks
             comparisons between imaging procedures.},
   Doi = {10.1118/1.4734763},
   Key = {fds269259}
}

@article{fds269272,
   Author = {Bower, D and Samei, E and Johnson, J},
   Title = {The Design of An Institution Wide Comprehensive Technique
             Chart for Size- Specific Radiography From Pediatrics to
             Adults},
   Journal = {Medical physics},
   Volume = {39},
   Number = {6},
   Pages = {3608-3608},
   Year = {2012},
   Month = {June},
   ISSN = {0094-2405},
   url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000308905804050&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
   Doi = {10.1118/1.4734647},
   Key = {fds269272}
}

@article{fds269273,
   Author = {Johnson, J and Samei, E and Christianson, O and Bower,
             D},
   Title = {An Effective Dose Monitoring Program for Computed
             Radiography},
   Journal = {Medical physics},
   Volume = {39},
   Number = {6},
   Pages = {3607-3607},
   Year = {2012},
   Month = {June},
   ISSN = {0094-2405},
   url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000308905804047&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
   Doi = {10.1118/1.4734644},
   Key = {fds269273}
}

@article{fds269276,
   Author = {Cook, T and Christianson, O and Samei, E},
   Title = {Informatics 2: Dose Monitoring},
   Journal = {Medical physics},
   Volume = {39},
   Number = {6},
   Pages = {3917-3917},
   Year = {2012},
   Month = {June},
   ISSN = {0094-2405},
   url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000308905805449&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
   Abstract = {Public concern over radiation from medical imaging is now
             higher than ever before and hospitals are being placed under
             increased scrutiny to ensure that their patients do not
             receive radiation overdoses. California already requires
             that there is a record of a dose estimate for every CT
             examination. In response, there has been a renewed interest
             in research and commercial ventures for the best method to
             monitor radiation dose for medical imaging procedures. The
             goal of this session is to highlight some tools that are
             currently available for dose monitoring, to illustrate how
             using these tools can improve the quality of care at an
             institution, and to provide a sample of the future
             developments in radiation dose monitoring.1. To provide an
             understanding of the basic science behind dose monitoring 2.
             To demonstrate few clinical implementation of dose
             monitoring systems 3. To discuss the advanced concepts
             currently under investigation (eg, patient size tracking) 4.
             To demonstrate how dose monitoring systems can be used for
             improved quality initiatives.},
   Doi = {10.1118/1.4735988},
   Key = {fds269276}
}

@article{fds269278,
   Author = {Chen, J and Yang, Z and Samei, E and Christianson, O and Dima, A and Filliben, J and Peskin, A and Saiprasad, G and Siegel,
             E},
   Title = {Evaluating the Impact of Iterative Reconstruction for Three
             Major CT Vendors},
   Journal = {Medical physics},
   Volume = {39},
   Number = {6},
   Pages = {3605-3606},
   Year = {2012},
   Month = {June},
   ISSN = {0094-2405},
   url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000308905804041&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
   Doi = {10.1118/1.4734637},
   Key = {fds269278}
}

@article{fds269279,
   Author = {Solomon, J and Christianson, O and Samei, E},
   Title = {Quantitative Comparison of Noise Texture Across CT Scanners
             From Different Vendors},
   Journal = {Medical physics},
   Volume = {39},
   Number = {6},
   Pages = {4016-4016},
   Year = {2012},
   Month = {June},
   ISSN = {0094-2405},
   url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000308905805838&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
   Doi = {10.1118/1.4736381},
   Key = {fds269279}
}

@article{fds269280,
   Author = {Kapadia, A and Samei, E and Harrawood, B and Sahbaee, P and Chawla, A and Tan, Z and Brady, D},
   Title = {X-Ray Coherent Scatter Diffraction Pattern Modeling in
             GEANT4},
   Journal = {Medical physics},
   Volume = {39},
   Number = {6},
   Pages = {3642-3643},
   Year = {2012},
   Month = {June},
   ISSN = {0094-2405},
   url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000308905804193&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
   Abstract = {To model X-ray coherent scatter diffraction patterns in
             GEANT4 for simulating experiments involving material
             detection through diffraction pattern measurement. Although
             coherent scatter cross-sections are modeled accurately in
             GEANT4, diffraction patterns for crystalline materials are
             not yet included. Here we describe our modeling of
             crystalline diffraction patterns in GEANT4 for specific
             materials and the validation of the results against
             experimentally measured data.Coherent scatter in GEANT4 is
             currently based on Hubbell's non-relativistic form factor
             tabulations from EPDL97. We modified the form-factors by
             introducing an interference function that accounts for the
             angular dependence between the Rayleigh-scattered photons
             and the photon wavelength. The modified form factors were
             used to replace the inherent form-factors in GEANT4. The
             simulation was tested using monochromatic and polychromatic
             x-ray beams (separately) incident on objects containing one
             or more elements with modified form-factors. The simulation
             results were compared against the experimentally measured
             diffraction images of corresponding objects using an
             in-house x-ray diffraction imager for validation. The
             comparison was made using the following metrics: number of
             diffraction rings, radial distance, absolute intensity, and
             relative intensity.Sharp diffraction pattern rings were
             observed in the monochromatic simulations at locations
             consistent with the angular dependence of the photon
             wavelength. In the polychromatic simulations, the
             diffraction patterns exhibited a radial blur consistent with
             the energy spread of the polychromatic spectrum. The
             simulated and experimentally measured patterns showed
             identical numbers of rings with close agreement in radial
             distance, absolute and relative intensities (barring
             statistical fluctuations). No significant change was
             observed in the execution time of the simulations.This work
             demonstrates the ability to model coherent scatter
             diffraction in GEANT4 in an accurate and efficient manner
             without compromising the accuracy or runtime of the
             simulation. This work was supported by the Department of
             Homeland Security under grant DHS (BAA 10-01 F075), and by
             the Department of Defense under award W81XWH-09-1-0066.},
   Doi = {10.1118/1.4734794},
   Key = {fds269280}
}

@article{fds269393,
   Author = {Zhang, Y and Li, X and Segars, WP and Samei, E},
   Title = {Organ doses, effective doses, and risk indices in adult CT:
             comparison of four types of reference phantoms across
             different examination protocols.},
   Journal = {Medical physics},
   Volume = {39},
   Number = {6},
   Pages = {3404-3423},
   Year = {2012},
   Month = {June},
   ISSN = {0094-2405},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/22755721},
   Keywords = {Adult • Female • Humans • Male •
             Neoplasms, Radiation-Induced • Phantoms, Imaging*
             • Radiation Dosage* • Risk Assessment •
             Tomography, X-Ray Computed • etiology •
             instrumentation*},
   Abstract = {PURPOSE: Radiation exposure from computed tomography (CT) to
             the public has increased the concern among radiation
             protection professionals. Being able to accurately assess
             the radiation dose patients receive during CT procedures is
             a crucial step in the management of CT dose. Currently,
             various computational anthropomorphic phantoms are used to
             assess radiation dose by different research groups. It is
             desirable to better understand how the dose results are
             affected by different choices of phantoms. In this study,
             the authors assessed the uncertainties in CT dose and risk
             estimation associated with different types of computational
             phantoms for a selected group of representative CT
             protocols. METHODS: Routinely used CT examinations were
             categorized into ten body and three neurological examination
             categories. Organ doses, effective doses, risk indices, and
             conversion coefficients to effective dose and risk index (k
             and q factors, respectively) were estimated for these
             examinations for a clinical CT system (LightSpeed VCT, GE
             Healthcare). Four methods were used, each employing a
             different type of reference phantoms. The first and second
             methods employed a Monte Carlo program previously developed
             and validated in our laboratory. In the first method, the
             reference male and female extended cardiac-torso (XCAT)
             phantoms were used, which were initially created from the
             Visible Human data and later adjusted to match organ masses
             defined in ICRP publication 89. In the second method, the
             reference male and female phantoms described in ICRP
             publication 110 were used, which were initially developed
             from tomographic data of two patients and later modified to
             match ICRP 89 organ masses. The third method employed a
             commercial dosimetry spreadsheet (ImPACT group, London,
             England) with its own hermaphrodite stylized phantom. In the
             fourth method, another widely used dosimetry spreadsheet
             (CT-Expo, Medizinische Hochschule, Hannover, Germany) was
             employed together with its associated male and female
             stylized phantoms. RESULTS: For fully irradiated organs,
             average coefficients of variation (COV) ranged from 0.07 to
             0.22 across the four male phantoms and from 0.06 to 0.18
             across the four female phantoms; for partially irradiated
             organs, average COV ranged from 0.13 to 0.30 across the four
             male phantoms and from 0.15 to 0.30 across the four female
             phantoms. Doses to the testes, breasts, and esophagus showed
             large variations between phantoms. COV for gender-averaged
             effective dose and k factor ranged from 0.03 to 0.23 and
             from 0.06 to 0.30, respectively. COV for male risk index and
             q factor ranged from 0.06 to 0.30 and from 0.05 to 0.36,
             respectively; COV for female risk index and q factor ranged
             from 0.06 to 0.49 and from 0.07 to 0.54, respectively.
             CONCLUSIONS: Despite closely matched organ mass, total body
             weight, and height, large differences in organ dose exist
             due to variation in organ location, spatial distribution,
             and dose approximation method. Dose differences for fully
             irradiated radiosensitive organs were much smaller than
             those for partially irradiated organs. Weighted dosimetry
             quantities including effective dose, male risk indices, k
             factors, and male q factors agreed well across phantoms. The
             female risk indices and q factors varied considerably across
             phantoms.},
   Language = {eng},
   Doi = {10.1118/1.4718710},
   Key = {fds269393}
}

@article{fds269395,
   Author = {Guo, W and Li, Q and Boyce, SJ and McAdams, HP and Shiraishi, J and Doi, K and Samei, E},
   Title = {A computerized scheme for lung nodule detection in
             multiprojection chest radiography.},
   Journal = {Medical physics},
   Volume = {39},
   Number = {4},
   Pages = {2001-2012},
   Year = {2012},
   Month = {April},
   ISSN = {0094-2405},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/22482621},
   Keywords = {Algorithms* • Humans • Imaging, Three-Dimensional
             • Pattern Recognition, Automated • Radiographic
             Image Enhancement • Radiographic Image Interpretation,
             Computer-Assisted • Radiography, Thoracic •
             Reproducibility of Results • Sensitivity and
             Specificity • Solitary Pulmonary Nodule •
             Subtraction Technique* • methods • methods* •
             radiography*},
   Abstract = {PURPOSE: Our previous study indicated that multiprojection
             chest radiography could significantly improve radiologists'
             performance for lung nodule detection in clinical practice.
             In this study, the authors further verify that
             multiprojection chest radiography can greatly improve the
             performance of a computer-aided diagnostic (CAD) scheme.
             METHODS: Our database consisted of 59 subjects, including 43
             subjects with 45 nodules and 16 subjects without nodules.
             The 45 nodules included 7 real and 38 simulated ones. The
             authors developed a conventional CAD scheme and a new fusion
             CAD scheme to detect lung nodules. The conventional CAD
             scheme consisted of four steps for (1) identification of
             initial nodule candidates inside lungs, (2) nodule candidate
             segmentation based on dynamic programming, (3) extraction of
             33 features from nodule candidates, and (4) false positive
             reduction using a piecewise linear classifier. The
             conventional CAD scheme processed each of the three
             projection images of a subject independently and discarded
             the correlation information between the three images. The
             fusion CAD scheme included the four steps in the
             conventional CAD scheme and two additional steps for (5)
             registration of all candidates in the three images of a
             subject, and (6) integration of correlation information
             between the registered candidates in the three images. The
             integration step retained all candidates detected at least
             twice in the three images of a subject and removed those
             detected only once in the three images as false positives. A
             leave-one-subject-out testing method was used for evaluation
             of the performance levels of the two CAD schemes. RESULTS:
             At the sensitivities of 70%, 65%, and 60%, our conventional
             CAD scheme reported 14.7, 11.3, and 8.6 false positives per
             image, respectively, whereas our fusion CAD scheme reported
             3.9, 1.9, and 1.2 false positives per image, and 5.5, 2.8,
             and 1.7 false positives per patient, respectively. The low
             performance of the conventional CAD scheme may be attributed
             to the high noise level in chest radiography, and the small
             size and low contrast of most nodules. CONCLUSIONS: This
             study indicated that the fusion of correlation information
             in multiprojection chest radiography can markedly improve
             the performance of CAD scheme for lung nodule
             detection.},
   Language = {eng},
   Doi = {10.1118/1.3694096},
   Key = {fds269395}
}

@article{fds269400,
   Author = {Chen, B and Barnhart, H and Richard, S and Colsher, J and Amurao, M and Samei, E},
   Title = {Quantitative CT: technique dependence of volume estimation
             on pulmonary nodules.},
   Journal = {Physics in Medicine and Biology},
   Volume = {57},
   Number = {5},
   Pages = {1335-1348},
   Year = {2012},
   Month = {March},
   ISSN = {1361-6560},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/22349265},
   Keywords = {Anthropometry • Equipment Design • Humans •
             Imaging, Three-Dimensional • Lung • Lung Neoplasms
             • Models, Statistical • Phantoms, Imaging •
             Polypropylenes • Reproducibility of Results •
             Software • Solitary Pulmonary Nodule • Thorax
             • Tomography, X-Ray Computed • chemistry •
             diagnosis • methods* • pathology •
             radiography • radiography*},
   Abstract = {Current estimation of lung nodule size typically relies on
             uni- or bi-dimensional techniques. While new
             three-dimensional volume estimation techniques using MDCT
             have improved size estimation of nodules with irregular
             shapes, the effect of acquisition and reconstruction
             parameters on accuracy (bias) and precision (variance) of
             the new techniques has not been fully investigated. To
             characterize the volume estimation performance dependence on
             these parameters, an anthropomorphic chest phantom
             containing synthetic nodules was scanned and reconstructed
             with protocols across various acquisition and reconstruction
             parameters. Nodule volumes were estimated by a clinical lung
             analysis software package, LungVCAR. Precision and accuracy
             of the volume assessment were calculated across the nodules
             and compared between protocols via a generalized estimating
             equation analysis. Results showed that the precision and
             accuracy of nodule volume quantifications were dependent on
             slice thickness, with different dependences for different
             nodule characteristics. Other parameters including kVp,
             pitch, and reconstruction kernel had lower impact.
             Determining these technique dependences enables better
             volume quantification via protocol optimization and
             highlights the importance of consistent imaging parameters
             in sequential examinations.},
   Language = {eng},
   Doi = {10.1088/0031-9155/57/5/1335},
   Key = {fds269400}
}

@article{fds269396,
   Author = {Samei, E and Button, TM and Orton, CG},
   Title = {Point/Counterpoint: The 2014 initiative can have potentially
             unintended negative consequences for medical physics in
             diagnostic imaging and nuclear medicine.},
   Journal = {Medical physics},
   Volume = {39},
   Number = {3},
   Pages = {1167-1168},
   Year = {2012},
   Month = {March},
   ISSN = {0094-2405},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/22380347},
   Language = {eng},
   Doi = {10.1118/1.3658741},
   Key = {fds269396}
}

@article{fds269398,
   Author = {Schnell, EA and Samei, E and Dobbins, JT},
   Title = {Plate-specific gain map correction for the improvement of
             detective quantum efficiency in computed
             radiography.},
   Journal = {Medical physics},
   Volume = {39},
   Number = {3},
   Pages = {1495-1504},
   Year = {2012},
   Month = {March},
   ISSN = {0094-2405},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/22380382},
   Abstract = {PURPOSE: The purpose of this work is to improve the noise
             power spectrum (NPS), and thus the detective quantum
             efficiency (DQE), of computed radiography (CR) images by
             correcting for spatial gain variations specific to
             individual imaging plates. CR devices have not traditionally
             employed gain-map corrections, unlike the case with
             flat-panel detectors, because of the multiplicity of plates
             used with each reader. The lack of gain-map correction has
             limited the DQE(f) at higher exposures with CR. This current
             work describes a feasible solution to generating
             plate-specific gain maps. METHODS: Ten high-exposure open
             field images were taken with an RQA5 spectrum, using a sixth
             generation CR plate suspended in air without a cassette.
             Image values were converted to exposure, the plates
             registered using fiducial dots on the plate, the ten images
             averaged, and then high-pass filtered to remove low
             frequency contributions from field inhomogeneity. A gain-map
             was then produced by converting all pixel values in the
             average into fractions with mean of one. The resultant
             gain-map of the plate was used to normalize subsequent
             single images to correct for spatial gain fluctuation. To
             validate performance, the normalized NPS (NNPS) for all
             images was calculated both with and without the gain-map
             correction. Variations in the quality of correction due to
             exposure levels, beam voltage/spectrum, CR reader used, and
             registration were investigated. RESULTS: The NNPS with
             plate-specific gain-map correction showed improvement over
             the noncorrected case over the range of frequencies from
             0.15 to 2.5 mm(-1). At high exposure (40 mR), NNPS was
             50%-90% better with gain-map correction than without. A
             small further improvement in NNPS was seen from carefully
             registering the gain-map with subsequent images using small
             fiducial dots, because of slight misregistration during
             scanning. Further improvement was seen in the NNPS from
             scaling the gain map about the mean to account for different
             beam spectra. CONCLUSIONS: This study demonstrates that a
             simple gain-map can be used to correct for the fixed-pattern
             noise in a given plate and thus improve the DQE of CR
             imaging. Such a method could easily be implemented by
             manufacturers because each plate has a unique bar code and
             the gain-map for all plates associated with a reader could
             be stored for future retrieval. These experiments indicated
             that an improvement in NPS (and hence, DQE) is possible,
             depending on exposure level, over a wide range of
             frequencies with this technique.},
   Language = {eng},
   Doi = {10.1118/1.3685580},
   Key = {fds269398}
}

@article{fds269415,
   Author = {Samei, E and Majdi-Nasab, N and Dobbins, JT and McAdams,
             HP},
   Title = {Biplane correlation imaging: a feasibility study based on
             phantom and human data.},
   Journal = {Journal of Digital Imaging},
   Volume = {25},
   Number = {1},
   Pages = {137-147},
   Year = {2012},
   Month = {February},
   ISSN = {1618-727X},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/21618054},
   Keywords = {Adult • Aged • Algorithms* • Artifacts •
             False Positive Reactions • Feasibility Studies •
             Humans • Lung Neoplasms • Middle Aged •
             Pattern Recognition, Automated • Phantoms, Imaging*
             • ROC Curve • Radiographic Image Enhancement
             • Radiographic Image Interpretation, Computer-Assisted
             • Radiography, Thoracic • Sampling Studies •
             Solitary Pulmonary Nodule • methods • methods*
             • radiography • radiography*},
   Abstract = {The objective of this study was to implement and evaluate
             the performance of a biplane correlation imaging (BCI)
             technique aimed to reduce the effect of anatomic noise and
             improve the detection of lung nodules in chest radiographs.
             Seventy-one low-dose posterior-anterior images were acquired
             from an anthropomorphic chest phantom with 0.28° angular
             separations over a range of ±10° along the vertical axis
             within an 11 s interval. Similar data were acquired from 19
             human subjects with institutional review board approval and
             informed consent. The data were incorporated into a
             computer-aided detection (CAD) algorithm in which suspect
             lesions were identified by examining the geometrical
             correlation of the detected signals that remained relatively
             constant against variable anatomic backgrounds. The data
             were analyzed to determine the effect of angular separation,
             and the overall sensitivity and false-positives for lung
             nodule detection. The best performance was achieved for
             angular separations of the projection pairs greater than
             5°. Within that range, the technique provided an order of
             magnitude decrease in the number of false-positive reports
             when compared with CAD analysis of single-view images.
             Overall, the technique yielded ~1.1 false-positive per
             patient with an average sensitivity of 75%. The results
             indicated that the incorporation of angular information can
             offer a reduction in the number of false-positives without a
             notable reduction in sensitivity. The findings suggest that
             the BCI technique has the potential for clinical
             implementation as a cost-effective technique to improve the
             detection of subtle lung nodules with lowered rate of
             false-positives.},
   Language = {eng},
   Doi = {10.1007/s10278-011-9392-z},
   Key = {fds269415}
}

@article{fds269281,
   Author = {Guo, W and Li, Q and Boyce, SJ and McAdams, HP and Shiraishi, J and Doi, K and Samei, E},
   Title = {Computerized Scheme for Lung Nodule Detection in
             Multi-Projection Chest Radiography},
   Journal = {Proceedings of SPIE - The International Society for Optical
             Engineering},
   Volume = {8315},
   Year = {2012},
   ISSN = {0277-786X},
   url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000305454600028&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
   Doi = {10.1117/12.911881},
   Key = {fds269281}
}

@article{fds269349,
   Author = {Lin, Y and Ghate, S and Lo, J and Samei, E},
   Title = {3D biopsy for tomosynthesis: Simulation of prior information
             based reconstruction for dose and artifact
             reduction},
   Journal = {Proceedings of SPIE},
   Volume = {8313},
   Year = {2012},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.912346},
   Abstract = {Accurately targeting of small lesions for success is crucial
             in breast biopsy. In this paper, we proposed a new 3D
             tomobased biopsy, which is characterized in being more
             accurate, easier to perform, lower in dose, and free of
             metal artifact. In the scout phase, a conventional
             tomosynthesis scan is performed, and the reconstructed 3D
             image is then used for radiologists to accurately localize
             target volume and determine optimized needle path. In the
             prefire phase, two prefire stereotactic images are obtained
             at +24° and -24° angular levels for retrieving needle and
             shifted lesion locations. By combining the reconstructed 3D
             tomosynthesis image, needle location and lesion location,
             synthetic prefire and postfire images are generated for
             radiologists' reference before firing the real needle. The
             proposed scheme not only improves the biopsy accuracy but
             also reduces dose by 3.7-5.6 times compared to conventional
             mammo-based stereotactic biopsy. A simulation using
             anthropomorphic phantom was conducted to verify our method.
             Both needle and lesion were precisely recovered just based
             on two tomo angled images. For the needle registration, the
             sum of translation discrepancy is less than 3 pixels, and
             the sum of rotation discrepancy is less than 3 degrees. For
             the lesion registration, the sum of coordinate discrepancy
             is less than 4 pixels. The predicted 3D prefire and postfire
             images exhibited more intuitive spatial relationship of the
             shifted lesion and biopsy needle tip than mammo-based
             stereotactic biopsy. © 2012 Copyright Society of
             Photo-Optical Instrumentation Engineers (SPIE).},
   Doi = {10.1117/12.912346},
   Key = {fds269349}
}

@article{fds269350,
   Author = {Ikejimba, L and Kiarashi, N and Lin, Y and Chen, B and Ghate, SV and Zerhouni, M and Samei, E and Lo, JY},
   Title = {Task-based strategy for optimized contrast enhanced breast
             imaging: Analysis of six imaging techniques for mammography
             and tomosynthesis},
   Journal = {Proceedings of SPIE},
   Volume = {8313},
   Year = {2012},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.913377},
   Abstract = {Digital breast tomosynthesis (DBT) is a novel x-ray imaging
             technique that provides 3D structural information of the
             breast. In contrast to 2D mammography, DBT minimizes tissue
             overlap potentially improving cancer detection and reducing
             number of unnecessary recalls. The addition of a contrast
             agent to DBT and mammography for lesion enhancement has the
             benefit of providing functional information of a lesion, as
             lesion contrast uptake and washout patterns may help
             differentiate between benign and malignant tumors. This
             study used a task-based method to determine the optimal
             imaging approach by analyzing six imaging paradigms in terms
             of their ability to resolve iodine at a given dose: contrast
             enhanced mammography and tomosynthesis, temporal subtraction
             mammography and tomosynthesis, and dual energy subtraction
             mammography and tomosynthesis. Imaging performance was
             characterized using a detectability index d', derived from
             the system task transfer function (TTF), an imaging task,
             iodine contrast, and the noise power spectrum (NPS). The
             task modeled a 5 mm lesion containing iodine concentrations
             between 2.1 mg/cc and 8.6 mg/cc. TTF was obtained using an
             edge phantom, and the NPS was measured over several exposure
             levels, energies, and target-filter combinations. Using a
             structured CIRS phantom, d' was generated as a function of
             dose and iodine concentration. In general, higher dose gave
             higher d', but for the lowest iodine concentration and
             lowest dose, dual energy subtraction tomosynthesis and
             temporal subtraction tomosynthesis demonstrated the highest
             performance. © 2012 Copyright Society of Photo-Optical
             Instrumentation Engineers (SPIE).},
   Doi = {10.1117/12.913377},
   Key = {fds269350}
}

@article{fds269364,
   Author = {Kiarashi, N and Lin, Y and Segars, WP and Ghate, SV and Ikejimba, L and Chen, B and Lo, JY and Iii, JTD and Nolte, LW and Samei,
             E},
   Title = {Development of a dynamic 4D anthropomorphic breast phantom
             for contrast-based breast imaging},
   Journal = {Proceedings of SPIE},
   Volume = {8313},
   Year = {2012},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.913332},
   Abstract = {Mammography is currently the most widely accepted tool for
             detection and diagnosis of breast cancer. However, the
             sensitivity of mammography is reduced in women with dense
             breast tissue due to tissue overlap, which may obscure
             lesions. Digital breast tomosynthesis with contrast
             enhancement reduces tissue overlap and provides additional
             functional information about lesions (i.e. morphology and
             kinetics), which in turn may improve lesion
             characterization. The performance of such techniques is
             highly dependent on the structural composition of the
             breast, which varies significantly across patients.
             Therefore, optimization of breast imaging systems should be
             done with respect to this patient versatility. Furthermore,
             imaging techniques that employ contrast require the
             inclusion of a temporally varying breast composition with
             respect to the contrast agent kinetics to enable the
             optimization of the system. To these ends, we have developed
             a dynamic 4D anthropomorphic breast phantom, which can be
             used for optimizing a breast imaging system by incorporating
             material characteristics. The presented dynamic phantom is
             based on two recently developed anthropomorphic breast
             phantoms, which can be representative of a whole population
             through their randomized anatomical feature generation and
             various compression levels. The 4D dynamic phantom is
             incorporated with the kinetics of contrast agent uptake in
             different tissues and can realistically model benign and
             malignant lesions. To demonstrate the utility of the
             proposed dynamic phantom, contrast-enhanced digital
             mammography and breast tomosynthesis were simulated where a
             ray-tracing algorithm emulated the projections, a filtered
             back projection algorithm was used for reconstruction, and
             dual-energy and temporal subtractions were performed and
             compared. © 2012 Copyright Society of Photo-Optical
             Instrumentation Engineers (SPIE).},
   Doi = {10.1117/12.913332},
   Key = {fds269364}
}

@article{fds269334,
   Author = {Chen, B and Richard, S and Christianson, O and Zhou, X and Samei,
             E},
   Title = {CT performance as a variable function of resolution, noise,
             and task property for iterative reconstructions},
   Journal = {Proceedings of SPIE},
   Volume = {8313},
   Year = {2012},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.913220},
   Abstract = {The increasing availability of iterative reconstruction (IR)
             algorithms on clinical scanners is creating a demand for
             effectively and efficiently evaluating imaging performance
             and potential dose reduction. In this study, the location-
             and task-specific evaluation was performed using
             detectability index (d') by combining a task function, the
             task transfer function (TTF), and the noise power spectrum
             (NPS). Task function modeled a wide variety detection tasks
             in terms of shape and contrast. The TTF and NPS were
             measured from a physical phantom as a function of contrast
             and dose levels. Measured d' values were compared between
             three IRs (IRIS, SAFIRE3 and SAFIRE5) and conventional
             filtered back-projection (FBP) at various dose levels,
             showing an equivalent performance of IR at lower dose
             levels. AUC further calculated from d' showed that compared
             to FBP, SAFIRE5 may reduce dose by up to 50-60%; SAFIRE3 and
             IRIS by up to 20-30%. This study provides an initial
             framework for the localized and task-specific evaluation of
             IRs in CT and a guideline for the identification of optimal
             operating dose point with iterative reconstructions. © 2012
             Copyright Society of Photo-Optical Instrumentation Engineers
             (SPIE).},
   Doi = {10.1117/12.913220},
   Key = {fds269334}
}

@article{fds269335,
   Author = {Chen, B and Richard, S and Samei, E},
   Title = {Relevance of MTF and NPS in quantitative CT: Towards
             developing a predictable model of quantitative
             performance},
   Journal = {Proceedings of SPIE},
   Volume = {8313},
   Year = {2012},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.913219},
   Abstract = {The quantification of lung nodule volume based on CT images
             provides valuable information for disease diagnosis and
             staging. However, the precision of the quantification is
             protocol, system, and technique dependent and needs to be
             evaluated for each specific case. To efficiently investigate
             the quantitative precision and find an optimal operating
             point, it is important to develop a predictive model based
             on basic system parameters. In this study, a Fourier-based
             metric, the estimability index (e') was proposed as such a
             predictor, and validated across a variety of imaging
             conditions. To first obtain the ground truth of quantitative
             precision, an anthropomorphic chest phantom with synthetic
             spherical nodules were imaged on a 64 slice CT scanner
             across a range of protocols (five exposure levels and two
             reconstruction algorithms). The volumes of nodules were
             quantified from the images using clinical software, with the
             precision of the quantification calculated for each
             protocol. To predict the precision, e' was calculated for
             each protocol based on several Fourier-based figures of
             merit, which modeled the characteristic of the quantitation
             task and the imaging condition (resolution, noise, etc.) of
             a particular protocol. Results showed a strong correlation
             (R 2=0.92) between the measured and predicted precision
             across all protocols, indicating e' as an effective
             predictor of the quantitative precision. This study provides
             a useful framework for quantification-oriented optimization
             of CT protocols. © 2012 Copyright Society of Photo-Optical
             Instrumentation Engineers (SPIE).},
   Doi = {10.1117/12.913219},
   Key = {fds269335}
}

@article{fds269351,
   Author = {Kiarashi, N and Ghate, SV and Lo, JY and Nolte, LW and Samei,
             E},
   Title = {Application of a dynamic 4D anthropomorphic breast phantom
             in contrast-based imaging system optimization: Dual-energy
             or temporal subtraction?},
   Journal = {Lecture notes in computer science},
   Volume = {7361 LNCS},
   Pages = {658-665},
   Year = {2012},
   ISSN = {0302-9743},
   url = {http://dx.doi.org/10.1007/978-3-642-31271-7_85},
   Abstract = {We previously developed a dynamic 4D anthropomorphic breast
             phantom, which can be used to optimize contrast-based breast
             imaging systems, accounting for patient variability and
             contrast kinetics [1]. In this study we aim to compare the
             performance of contrast-enhanced mammographic and
             tomosynthesis imaging protocols followed by temporal
             subtraction and dual-energy subtraction, qualitatively and
             quantitatively across a couple of patient models.
             Signal-difference-to-noise ratio (SDNR) is measured for the
             six paradigms of contrast enhanced, temporally subtracted,
             and dual-energy subtracted mammography and tomosynthesis and
             compared. The results show how the performance is more
             dependent on the breast model in mammography than in
             tomosynthesis. Also, it is observed that dual-energy
             subtraction can be beneficial in mammography, whereas it is
             not advantageous in tomosynthesis. Lastly, the results
             suggest that temporal subtraction in general outperforms
             dual-energy subtraction. © 2012 Springer-Verlag Berlin
             Heidelberg.},
   Doi = {10.1007/978-3-642-31271-7_85},
   Key = {fds269351}
}

@article{fds269357,
   Author = {Tian, X and Li, X and Segars, WP and Frush, DP and Samei,
             E},
   Title = {Patient- and cohort-specific dose and risk estimation for
             abdominopelvic CT: A study based on 100 patients},
   Journal = {Proceedings of SPIE},
   Volume = {8313},
   Year = {2012},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.913341},
   Abstract = {The purpose of this work was twofold: (a) to estimate
             patient- and cohort-specific radiation dose and cancer risk
             index for abdominopelvic computer tomography (CT) scans; (b)
             to evaluate the effects of patient anatomical
             characteristics (size, age, and gender) and CT scanner model
             on dose and risk conversion coefficients. The study included
             100 patient models (42 pediatric models, 58 adult models)
             and multi-detector array CT scanners from two commercial
             manufacturers (LightSpeed VCT, GE Healthcare; SOMATOM
             Definition Flash, Siemens Healthcare). A
             previously-validated Monte Carlo program was used to
             simulate organ dose for each patient model and each scanner,
             from which DLP-normalized-effective dose (k factor) and
             DLP-normalized-risk index values (q factor) were derived.
             The k factor showed exponential decrease with increasing
             patient size. For a given gender, q factor showed
             exponential decrease with both increasing patient size and
             patient age. The discrepancies in k and q factors across
             scanners were on average 8% and 15%, respectively. This
             study demonstrates the feasibility of estimating
             patient-specific organ dose and cohort-specific effective
             dose and risk index in abdominopelvic CT requiring only the
             knowledge of patient size, gender, and age. © 2012
             Copyright Society of Photo-Optical Instrumentation Engineers
             (SPIE).},
   Doi = {10.1117/12.913341},
   Key = {fds269357}
}

@article{fds269358,
   Author = {Bond, J and Frush, J and Hon, S and Eckersley, C and Williams, CH and Feng,
             J and Tward, DJ and Ratnanather, TJT and Miller, MI and Frush, D and Samei,
             E and Segars, WP},
   Title = {Series of 4D adult XCAT phantoms for imaging research and
             dosimetry},
   Journal = {Proceedings of SPIE},
   Volume = {8313},
   Year = {2012},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.911676},
   Abstract = {Computerized phantoms are finding an increasingly important
             role in medical imaging research. With the ability to
             simulate various imaging conditions, they offer a practical
             means with which to quantitatively evaluate and improve
             imaging devices and techniques. This is especially true in
             CT due to the high radiation levels involved with it.
             Despite their utility, due to the time required to develop
             them, only a handful of computational models currently exist
             of varying detail. Most phantoms available are limited to 3D
             and not capable of modeling patient motion. We have
             previously developed a technique to rapidly create highly
             detailed 4D extended cardiac-torso (XCAT) phantoms based on
             patient CT data [1]. In this study, we utilize this
             technique to generate 58 new adult XCAT phantoms to be added
             to our growing library of virtual patients available for
             imaging research. These computerized patients provide a
             valuable tool for investigating imaging devices and the
             effects of anatomy and motion in imaging. They also provide
             the essential tools to investigate patient-specific dose
             estimation and optimization for adults undergoing CT
             procedures. © 2012 Copyright Society of Photo-Optical
             Instrumentation Engineers (SPIE).},
   Doi = {10.1117/12.911676},
   Key = {fds269358}
}

@article{fds269365,
   Author = {MacCabe, K and Krishnamurthy, K and Chawla, A and Marks, D and Samei, E and Brady, D},
   Title = {Pencil beam coded aperture x-ray scatter
             imaging},
   Journal = {Optics express},
   Volume = {20},
   Number = {15},
   Pages = {16310-16320},
   Year = {2012},
   ISSN = {1094-4087},
   url = {http://dx.doi.org/10.1364/OE.20.016310},
   Abstract = {We use coded aperture x-ray scatter imaging to interrogate
             scattering targets with a pencil beam. Observations from a
             single x-ray exposure of a flat-panel scintillation detector
             are used to simultaneously determine the along-beam
             positions and momentum transfer profiles of two crystalline
             powders (NaCl and Al). The system operates with a 3 cm range
             resolution and a momentum transfer resolution of 0.1 nm 1.
             These results demonstrate that a single snapshot can be used
             to estimate scattering properties along an x-ray beam, and
             serve as a foundation for volumetric imaging of scattering
             objects. © 2012 Optical Society of America.},
   Doi = {10.1364/OE.20.016310},
   Key = {fds269365}
}

@article{fds269401,
   Author = {Samei, E and Anthony Seibert and J},
   Title = {The tenuous state of clinical medical physics in diagnostic
             imaging.},
   Journal = {Medical physics},
   Volume = {38},
   Number = {12},
   Pages = {iii-iv},
   Year = {2011},
   Month = {December},
   ISSN = {0094-2405},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/22149863},
   Keywords = {Diagnostic Imaging • Health Physics • Physician's
             Role* • United States • trends*},
   Language = {eng},
   Doi = {10.1118/1.3664002},
   Key = {fds269401}
}

@article{fds269411,
   Author = {D'Alessandro, B and Madsen, M and Samei, E and Li, X and Wooi-Tan, J and Berbaum, KS and Schartz, K and Caldwell, R and Zuckier,
             LS},
   Title = {Synthetic positron emission tomography-computed tomography
             images for use in perceptual studies.},
   Journal = {Seminars in Nuclear Medicine},
   Volume = {41},
   Number = {6},
   Pages = {437-448},
   Year = {2011},
   Month = {November},
   ISSN = {1558-4623},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/21978446},
   Keywords = {Algorithms • Artifacts* • Data Display •
             Diagnostic Errors • Humans • Image Processing,
             Computer-Assisted • Models, Biological* •
             Perception • Positron-Emission Tomography •
             Sensitivity and Specificity • Tomography, X-Ray
             Computed • methods* • prevention &
             control*},
   Abstract = {To better understand fundamental issues, perception studies
             of the fusion display would best be performed with a panel
             of lesions of variable location, size, intensity, and
             background. There are compelling reasons to use synthetic
             images that contain artificial lesions for perception
             research. A consideration of how to obtain this panel of
             lesions is the nucleus of the present review. This article
             is a conjoint effort of 3 groups that have joined together
             to review results from work that they and others have
             performed. The techniques we review include (1) substitution
             of lesions into a preexisting image matrix (either using
             actual prior patient-derived lesions or mathematically
             modeled artificial lesions), (2) addition of images (either
             in the attenuation-corrected image space or at an earlier
             stage before image reconstruction), and (3) simulation of
             the entire patient image. A judicious combination of the
             techniques discussed in this review may represent the most
             efficient pathway of simulating statistically varied but
             realistic appearing lesions.},
   Language = {eng},
   Doi = {10.1053/j.semnuclmed.2011.06.007},
   Key = {fds269411}
}

@article{fds269414,
   Author = {Wang, CL and Chea, YW and Boll, DT and Samei, E and Neville, AM and Dale,
             BM and Merkle, EM},
   Title = {Effect of gadolinium chelate contrast agents on diffusion
             weighted MR imaging of the liver, spleen, pancreas and
             kidney at 3 T.},
   Journal = {European Journal of Radiology},
   Volume = {80},
   Number = {2},
   Pages = {e1-e7},
   Year = {2011},
   Month = {November},
   ISSN = {1872-7727},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/20646887},
   Keywords = {Adult • Analysis of Variance • Contrast Media
             • Diffusion Magnetic Resonance Imaging •
             Echo-Planar Imaging • Female • Gadolinium DTPA
             • Humans • Kidney Diseases • Liver Diseases
             • Male • Meglumine • Middle Aged •
             Organometallic Compounds • Pancreatic Diseases •
             Retrospective Studies • Splenic Diseases •
             administration & dosage • analogs & derivatives* •
             diagnosis* • diagnostic use • diagnostic use*
             • methods*},
   Abstract = {PURPOSE: To retrospectively test the null hypotheses that
             the qualitative appearance of DWI and the signal intensity
             values in DWI and corresponding ADC values of the liver,
             spleen, pancreas and kidneys are identical before and after
             the administration of gadolinium. MATERIALS AND METHODS:
             Following IRB approval, DWI was acquired in 50 patients (25
             male; mean age 54.9 years) prior to and after contrast
             administration, using single-shot echo planar imaging with
             b-values of 50 s/mm2 and 800 s/mm2 at 3 T. Binomial analysis
             was used to determine which image set was more significantly
             preferred in conveying the diffusion information. Pre- and
             post-gadolinium DWI and ADC values of corresponding regions
             of each organ were analyzed using standardized signal
             intensity measurements. RESULTS: Pre-contrast DWI images of
             the liver, spleen, and pancreas were preferred 52%, 49%, and
             58%, respectively, with none of the differences being
             statistically significant. DWI of the kidneys was preferred
             on pre-contrast images in 83% (p<0.001). In the liver and
             spleen, contrast caused a significant increase in the
             post-contrast DWI signal intensity values at b=50 (p<0.02)
             and b=800 (p<0.05) but had no statistically significant
             effect on the ADC value (p>0.40). Pancreatic DWI signal
             intensity and ADC values pre- and post-contrast were also
             not significantly different (p=0.489). In the renal
             parenchyma, significant decrease in the values of DWI at
             b=50 (p<0.01) and b=800 (p<0.01) as well as ADC (p<0.02) was
             demonstrated following gadolinium administration.
             CONCLUSION: Intravenous gadolinium administration does not
             make a statistically significant difference in the
             qualitative appearance or ADC measurements of the liver,
             spleen, or pancreas when comparing pre-contrast to
             post-contrast DWI. In the kidneys, however, ADC values are
             significantly lower post-contrast with the pre-contrast
             diffusion weighted images also being qualitatively
             preferred.},
   Language = {eng},
   Doi = {10.1016/j.ejrad.2010.05.019},
   Key = {fds269414}
}

@article{fds269409,
   Author = {Samei, E and Saunders, RS},
   Title = {Dual-energy contrast-enhanced breast tomosynthesis:
             optimization of beam quality for dose and image
             quality.},
   Journal = {Physics in Medicine and Biology},
   Volume = {56},
   Number = {19},
   Pages = {6359-6378},
   Year = {2011},
   Month = {October},
   ISSN = {1361-6560},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/21908902},
   Keywords = {Breast • Breast Neoplasms • Computer Simulation
             • Contrast Media • Female • Humans •
             Image Processing, Computer-Assisted • Models,
             Biological • Monte Carlo Method • Phantoms,
             Imaging • Photons • Quality Control •
             Radiography, Dual-Energy Scanned Projection •
             diagnostic use* • methods* • pathology* •
             standards},
   Abstract = {Dual-energy contrast-enhanced breast tomosynthesis is a
             promising technique to obtain three-dimensional functional
             information from the breast with high resolution and speed.
             To optimize this new method, this study searched for the
             beam quality that maximized image quality in terms of mass
             detection performance. A digital tomosynthesis system was
             modeled using a fast ray-tracing algorithm, which created
             simulated projection images by tracking photons through a
             voxelized anatomical breast phantom containing iodinated
             lesions. The single-energy images were combined into
             dual-energy images through a weighted log subtraction
             process. The weighting factor was optimized to minimize
             anatomical noise, while the dose distribution was chosen to
             minimize quantum noise. The dual-energy images were analyzed
             for the signal difference to noise ratio (SdNR) of iodinated
             masses. The fast ray-tracing explored 523 776 dual-energy
             combinations to identify which yields optimum mass SdNR. The
             ray-tracing results were verified using a Monte Carlo model
             for a breast tomosynthesis system with a selenium-based
             flat-panel detector. The projection images from our
             voxelized breast phantom were obtained at a constant total
             glandular dose. The projections were combined using weighted
             log subtraction and reconstructed using commercial
             reconstruction software. The lesion SdNR was measured in the
             central reconstructed slice. The SdNR performance varied
             markedly across the kVp and filtration space. Ray-tracing
             results indicated that the mass SdNR was maximized with a
             high-energy tungsten beam at 49 kVp with 92.5 µm of copper
             filtration and a low-energy tungsten beam at 49 kVp with 95
             µm of tin filtration. This result was consistent with Monte
             Carlo findings. This mammographic technique led to a mass
             SdNR of 0.92 ± 0.03 in the projections and 3.68 ± 0.19 in
             the reconstructed slices. These values were markedly higher
             than those for non-optimized techniques. Our findings
             indicate that dual-energy breast tomosynthesis can be
             performed optimally at 49 kVp with alternative copper and
             tin filters, with reconstruction following weighted
             subtraction. The optimum technique provides best visibility
             of iodine against structured breast background in
             dual-energy contrast-enhanced breast tomosynthesis.},
   Language = {eng},
   Doi = {10.1088/0031-9155/56/19/013},
   Key = {fds269409}
}

@article{fds269406,
   Author = {Samei, E and Ranger, NT and Dobbins, JT and Ravin,
             CE},
   Title = {Effective dose efficiency: an application-specific metric of
             quality and dose for digital radiography.},
   Journal = {Physics in Medicine and Biology},
   Volume = {56},
   Number = {16},
   Pages = {5099-5118},
   Year = {2011},
   Month = {August},
   ISSN = {1361-6560},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/21775791},
   Keywords = {Adult • Humans • Infant • Male •
             Phantoms, Imaging • Quality Control • Radiation
             Dosage* • Radiographic Image Enhancement •
             Radiography, Thoracic • methods* •
             standards*},
   Abstract = {The detective quantum efficiency (DQE) and the effective DQE
             (eDQE) are relevant metrics of image quality for digital
             radiography detectors and systems, respectively. The current
             study further extends the eDQE methodology to technique
             optimization using a new metric of the effective dose
             efficiency (eDE), reflecting both the image quality as well
             as the effective dose (ED) attributes of the imaging system.
             Using phantoms representing pediatric, adult and large adult
             body habitus, image quality measurements were made at 80,
             100, 120 and 140 kVp using the standard eDQE protocol and
             exposures. ED was computed using Monte Carlo methods. The
             eDE was then computed as a ratio of image quality to ED for
             each of the phantom/spectral conditions. The eDQE and eDE
             results showed the same trends across tube potential with 80
             kVp yielding the highest values and 120 kVp yielding the
             lowest. The eDE results for the pediatric phantom were
             markedly lower than the results for the adult phantom at
             spatial frequencies lower than 1.2-1.7 mm(-1), primarily due
             to a correspondingly higher value of ED per entrance
             exposure. The relative performance for the adult and large
             adult phantoms was generally comparable but affected by
             kVps. The eDE results for the large adult configuration were
             lower than the eDE results for the adult phantom, across all
             spatial frequencies (120 and 140 kVp) and at spatial
             frequencies greater than 1.0 mm(-1) (80 and 100 kVp).
             Demonstrated for chest radiography, the eDE shows promise as
             an application-specific metric of imaging performance,
             reflective of body habitus and radiographic technique, with
             utility for radiography protocol assessment and
             optimization.},
   Language = {eng},
   Doi = {10.1088/0031-9155/56/16/002},
   Key = {fds269406}
}

@article{fds328135,
   Author = {Murphy, S and Christianson, O and Samei, E},
   Title = {SU-C-220-01: Comparative MTF and DQE Performance of Wireless
             Digital Image Receptors},
   Journal = {Medical physics},
   Volume = {38},
   Number = {6Part2},
   Pages = {3379-3379},
   Year = {2011},
   Month = {June},
   url = {http://dx.doi.org/10.1118/1.3611507},
   Doi = {10.1118/1.3611507},
   Key = {fds328135}
}

@article{fds328136,
   Author = {Murphy, S and Richard, S and Samei, E},
   Title = {WE-G-110-03: Directional MTF Measurement of Tomosynthesis
             Images Using a Cone-Based Technique},
   Journal = {Medical physics},
   Volume = {38},
   Number = {6Part33},
   Pages = {3833-3833},
   Year = {2011},
   Month = {June},
   url = {http://dx.doi.org/10.1118/1.3613433},
   Doi = {10.1118/1.3613433},
   Key = {fds328136}
}

@article{fds328137,
   Author = {Zhang, Y and Li, X and Segars, W and Samei, E},
   Title = {TH-A-214-02: Organ Dose, Effective Dose, and Dose Conversion
             Coefficients in Adult CT: Comparison of Mathematical, XCAT,
             and ICRP Reference Phantoms},
   Journal = {Medical physics},
   Volume = {38},
   Number = {6Part34},
   Pages = {3842-3843},
   Year = {2011},
   Month = {June},
   url = {http://dx.doi.org/10.1118/1.3613467},
   Doi = {10.1118/1.3613467},
   Key = {fds328137}
}

@article{fds328138,
   Author = {Sechopoulos, I and Abboud, S and Ali, E and Badal, A and Badano, A and Feng, SSJ and Kyprianou, I and McNitt-Gray, M and Samei, E and Turner,
             A},
   Title = {WE-G-110-06: Introduction to the AAPM Task Group No. 195 -
             Monte Carlo Reference Data Sets for Imaging
             Research},
   Journal = {Medical physics},
   Volume = {38},
   Number = {6Part33},
   Pages = {3834-3834},
   Year = {2011},
   Month = {June},
   url = {http://dx.doi.org/10.1118/1.3613436},
   Doi = {10.1118/1.3613436},
   Key = {fds328138}
}

@article{fds328139,
   Author = {McNitt-Gray, M and Xu, X and Samei, E},
   Title = {TU-C-110-01: Patient Dose in CT: Calculating Patient
             Specific Doses in CT(Joint with Education)},
   Journal = {Medical physics},
   Volume = {38},
   Number = {6Part29},
   Pages = {3759-3759},
   Year = {2011},
   Month = {June},
   url = {http://dx.doi.org/10.1118/1.3613145},
   Doi = {10.1118/1.3613145},
   Key = {fds328139}
}

@article{fds328140,
   Author = {Samei, E and Gingold, E},
   Title = {TU-A-110-01: Resolution in Digital Radiography},
   Journal = {Medical physics},
   Volume = {38},
   Number = {6Part28},
   Pages = {3744-3744},
   Year = {2011},
   Month = {June},
   url = {http://dx.doi.org/10.1118/1.3613089},
   Doi = {10.1118/1.3613089},
   Key = {fds328140}
}

@article{fds328141,
   Author = {Richard, S and Samei, E},
   Title = {SU-D-301-06: Impact of Non-Stationarity in Breast
             Tomosynthesis on Task-Based Imaging Performance},
   Journal = {Medical physics},
   Volume = {38},
   Number = {6Part3},
   Pages = {3389-3389},
   Year = {2011},
   Month = {June},
   url = {http://dx.doi.org/10.1118/1.3611548},
   Doi = {10.1118/1.3611548},
   Key = {fds328141}
}

@article{fds328142,
   Author = {Richard, S and Samei, E},
   Title = {WE-C-110-08: A Novel Phantom for CT Performance Assessment:
             Towards a Task-Based Measure of Image Quality},
   Journal = {Medical physics},
   Volume = {38},
   Number = {6Part32},
   Pages = {3810-3810},
   Year = {2011},
   Month = {June},
   url = {http://dx.doi.org/10.1118/1.3613347},
   Doi = {10.1118/1.3613347},
   Key = {fds328142}
}

@article{fds327418,
   Author = {Christianson, O and Li, X and Frush, D and Samei,
             E},
   Title = {TH-A-214-03: Automated Patient-Specific CT Dose Monitoring
             System: Assessing Variability in CT Dose},
   Journal = {Medical physics},
   Volume = {38},
   Number = {6Part34},
   Pages = {3843-3843},
   Year = {2011},
   Month = {June},
   url = {http://dx.doi.org/10.1118/1.3613468},
   Doi = {10.1118/1.3613468},
   Key = {fds327418}
}

@article{fds269408,
   Author = {Li, X and Samei, E and Segars, WP and Sturgeon, GM and Colsher, JG and Frush, DP},
   Title = {Patient-specific radiation dose and cancer risk for
             pediatric chest CT.},
   Journal = {Radiology},
   Volume = {259},
   Number = {3},
   Pages = {862-874},
   Year = {2011},
   Month = {June},
   ISSN = {1527-1315},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/21467251},
   Keywords = {Adolescent • Body Size • Child • Child,
             Preschool • Female • Humans • Infant •
             Infant, Newborn • Male • Models, Anatomic •
             Monte Carlo Method • Neoplasms, Radiation-Induced
             • Radiation Dosage* • Radiography, Thoracic •
             Regression Analysis • Risk • Thoracic Neoplasms
             • Thorax • Tomography, X-Ray Computed •
             adverse effects* • anatomy & histology* •
             etiology*},
   Abstract = {PURPOSE: To estimate patient-specific radiation dose and
             cancer risk for pediatric chest computed tomography (CT) and
             to evaluate factors affecting dose and risk, including
             patient size, patient age, and scanning parameters.
             MATERIALS AND METHODS: The institutional review board
             approved this study and waived informed consent. This study
             was HIPAA compliant. The study included 30 patients (0-16
             years old), for whom full-body computer models were recently
             created from clinical CT data. A validated Monte Carlo
             program was used to estimate organ dose from eight chest
             protocols, representing clinically relevant combinations of
             bow tie filter, collimation, pitch, and tube potential.
             Organ dose was used to calculate effective dose and risk
             index (an index of total cancer incidence risk). The dose
             and risk estimates before and after normalization by
             volume-weighted CT dose index (CTDI(vol)) or dose-length
             product (DLP) were correlated with patient size and age. The
             effect of each scanning parameter was studied. RESULTS:
             Organ dose normalized by tube current-time product or
             CTDI(vol) decreased exponentially with increasing average
             chest diameter. Effective dose normalized by tube
             current-time product or DLP decreased exponentially with
             increasing chest diameter. Chest diameter was a stronger
             predictor of dose than weight and total scan length. Risk
             index normalized by tube current-time product or DLP
             decreased exponentially with both chest diameter and age.
             When normalized by DLP, effective dose and risk index were
             independent of collimation, pitch, and tube potential (<10%
             variation). CONCLUSION: The correlations of dose and risk
             with patient size and age can be used to estimate
             patient-specific dose and risk. They can further guide the
             design and optimization of pediatric chest CT protocols.
             SUPPLEMENTAL MATERIAL: http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.11101900/-/DC1.},
   Language = {eng},
   Doi = {10.1148/radiol.11101900},
   Key = {fds269408}
}

@article{fds269405,
   Author = {Li, X and Samei, E and Barnhart, HX and Gaca, AM and Hollingsworth, CL and Maxfield, CM and Carrico, CWT and Colsher, JG and Frush,
             DP},
   Title = {Lung nodule detection in pediatric chest CT: quantitative
             relationship between image quality and radiologist
             performance.},
   Journal = {Medical physics},
   Volume = {38},
   Number = {5},
   Pages = {2609-2618},
   Year = {2011},
   Month = {May},
   ISSN = {0094-2405},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/21776798},
   Keywords = {Adolescent • Algorithms* • Child • Child,
             Preschool • Female • Humans • Infant •
             Infant, Newborn • Male • Observer Variation •
             Professional Competence* • Radiographic Image
             Enhancement • Radiographic Image Interpretation,
             Computer-Assisted • Radiography, Thoracic •
             Reproducibility of Results • Sensitivity and
             Specificity • Solitary Pulmonary Nodule •
             Tomography, X-Ray Computed • methods • methods*
             • radiography*},
   Abstract = {PURPOSE: To determine the quantitative relationship between
             image quality and radiologist performance in detecting small
             lung nodules in pediatric CT. METHODS: The study included
             clinical chest CT images of 30 pediatric patients (0-16
             years) scanned at tube currents of 55-180 mA. Calibrated
             noise addition software was used to simulate cases at three
             nominal mA settings: 70, 35, and 17.5 mA, resulting in
             quantum noise of 7-32 Hounsfield Unit (HU). Using a
             validated nodule simulation technique, lung nodules with
             diameters of 3-5 mm and peak contrasts of 200-500 HU were
             inserted into the cases, which were then randomized and
             rated independently by four experienced pediatric
             radiologists for nodule presence on a continuous scale from
             0 (definitely absent) to 100 (definitely present). The
             receiver operating characteristic (ROC) data were analyzed
             to quantify the relationship between diagnostic accuracy
             (area under the ROC curve, AUC) and image quality (the
             product of nodule peak contrast and displayed diameter to
             noise ratio, CDNR display). RESULTS: AUC increased rapidly
             from 0.70 to 0.87 when CDNR display increased from 60 to 130
             mm, followed by a slow increase to 0.94 when CDNR display
             further increased to 257 mm. For the average nodule diameter
             (4 mm) and contrast (350 HU), AUC decreased from 0.93 to
             0.71 with noise increased from 7 to 28 HU. CONCLUSIONS: We
             quantified the relationship between image quality and the
             performance of radiologists in detecting lung nodules in
             pediatric CT. The relationship can guide CT protocol design
             to achieve the desired diagnostic performance at the lowest
             radiation dose.]},
   Language = {eng},
   Doi = {10.1118/1.3582975},
   Key = {fds269405}
}

@article{fds269412,
   Author = {Chen, B and Shorey, J and Saunders, RS and Richard, S and Thompson, J and Nolte, LW and Samei, E},
   Title = {An anthropomorphic breast model for breast imaging
             simulation and optimization.},
   Journal = {Academic Radiology},
   Volume = {18},
   Number = {5},
   Pages = {536-546},
   Year = {2011},
   Month = {May},
   ISSN = {1878-4046},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/21397528},
   Keywords = {Computer Simulation • Humans • Mammography* •
             Models, Anatomic* • Monte Carlo Method •
             Tomography, X-Ray Computed},
   Abstract = {RATIONALE AND OBJECTIVES: Optimization studies for
             x-ray-based breast imaging systems using computer simulation
             can greatly benefit from a phantom capable of modeling
             varying anatomical variability across different patients.
             This study aimed to develop a three-dimensional phantom
             model with realistic and randomizable anatomical features.
             MATERIALS AND METHODS: A voxelized breast model was
             developed consisting of an outer layer of skin and
             subcutaneous fat, a mixture of glandular and adipose,
             stochastically generated ductal trees, masses, and
             microcalcifications. Randomized realization of the breast
             morphology provided a range of patient models. Compression
             models were included to represent the breast under various
             compression levels along different orientations. A Monte
             Carlo (MC) simulation code was adapted to simulate x-ray
             based imaging systems for the breast phantom. Simulated
             projections of the phantom at different angles were
             generated and reconstructed with iterative methods,
             simulating mammography, breast tomosynthesis, and computed
             tomography (CT) systems. Phantom dose maps were further
             generated for dosimetric evaluation. RESULTS: Region of
             interest comparisons of simulated and real mammograms showed
             strong similarities in terms of appearance and features.
             Noise-power spectra of simulated mammographic images
             demonstrated that the phantom provided target properties for
             anatomical backgrounds. Reconstructed tomosynthesis and CT
             images and dose maps provided corresponding data from a
             single breast enabling optimization studies. Dosimetry
             result provided insight into the dose distribution
             difference between modalities and compression levels.
             CONCLUSION: The anthropomorphic breast phantom, combined
             with the MC simulation platform, generated a realistic model
             for a breast imaging system. The developed platform is
             expected to provide a versatile and powerful framework for
             optimizing volumetric breast imaging systems.},
   Language = {eng},
   Doi = {10.1016/j.acra.2010.11.009},
   Key = {fds269412}
}

@article{fds269418,
   Author = {Webb, LJ and Samei, E and Lo, JY and Baker, JA and Ghate, SV and Kim, C and Soo, MS and Walsh, R},
   Title = {Comparative performance of multiview stereoscopic and
             mammographic display modalities for breast lesion
             detection.},
   Journal = {Medical physics},
   Volume = {38},
   Number = {4},
   Pages = {1972-1980},
   Year = {2011},
   Month = {April},
   ISSN = {0094-2405},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/21626930},
   Keywords = {Algorithms • Breast Neoplasms • Computer Graphics*
             • Humans • Image Processing, Computer-Assisted
             • Mammography • ROC Curve • instrumentation
             • methods* • radiography*},
   Abstract = {PURPOSE: Mammography is known to be one of the most
             difficult radiographic exams to interpret. Mammography has
             important limitations, including the superposition of normal
             tissue that can obscure a mass, chance alignment of normal
             tissue to mimic a true lesion and the inability to derive
             volumetric information. It has been shown that
             stereomammography can overcome these deficiencies by showing
             that layers of normal tissue lay at different depths. If
             standard stereomammography (i.e., a single stereoscopic pair
             consisting of two projection images) can significantly
             improve lesion detection, how will multiview stereoscopy
             (MVS), where many projection images are used, compare to
             mammography? The aim of this study was to assess the
             relative performance of MVS compared to mammography for
             breast mass detection. METHODS: The MVS image sets consisted
             of the 25 raw projection images acquired over an arc of
             approximately 45 degrees using a Siemens prototype breast
             tomosynthesis system. The mammograms were acquired using a
             commercial Siemens FFDM system. The raw data were taken from
             both of these systems for 27 cases and realistic simulated
             mass lesions were added to duplicates of the 27 images at
             the same local contrast. The images with lesions (27
             mammography and 27 MVS) and the images without lesions (27
             mammography and 27 MVS) were then postprocessed to provide
             comparable and representative image appearance across the
             two modalities. All 108 image sets were shown to five
             full-time breast imaging radiologists in random order on a
             state-of-the-art stereoscopic display. The observers were
             asked to give a confidence rating for each image (0 for
             lesion definitely not present, 100 for lesion definitely
             present). The ratings were then compiled and processed using
             ROC and variance analysis. RESULTS: The mean AUC for the
             five observers was 0.614 +/- 0.055 for mammography and 0.778
             +/- 0.052 for multiview stereoscopy. The difference of 0.164
             +/- 0.065 was statistically significant with a p-value of
             0.0148. CONCLUSIONS: The differences in the AUCs and the
             p-value suggest that multiview stereoscopy has a
             statistically significant advantage over mammography in the
             detection of simulated breast masses. This highlights the
             dominance of anatomical noise compared to quantum noise for
             breast mass detection. It also shows that significant lesion
             detection can be achieved with MVS without any of the
             artifacts associated with tomosynthesis.},
   Language = {eng},
   Doi = {10.1118/1.3562901},
   Key = {fds269418}
}

@article{fds269403,
   Author = {Li, X and Samei, E and Segars, WP and Sturgeon, GM and Colsher, JG and Toncheva, G and Yoshizumi, TT and Frush, DP},
   Title = {Patient-specific radiation dose and cancer risk estimation
             in CT: part I. development and validation of a Monte Carlo
             program.},
   Journal = {Medical physics},
   Volume = {38},
   Number = {1},
   Pages = {397-407},
   Year = {2011},
   Month = {January},
   ISSN = {0094-2405},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/21361208},
   Keywords = {Adult • Female • Humans • Individualized
             Medicine • Infant • Monte Carlo Method* •
             Neoplasms, Radiation-Induced • Phantoms, Imaging •
             Radiation Dosage* • Risk Assessment •
             Thermoluminescent Dosimetry • Tomography, X-Ray
             Computed • adverse effects* • etiology* •
             methods*},
   Abstract = {PURPOSE: Radiation-dose awareness and optimization in CT can
             greatly benefit from a dose-reporting system that provides
             dose and risk estimates specific to each patient and each CT
             examination. As the first step toward patient-specific dose
             and risk estimation, this article aimed to develop a method
             for accurately assessing radiation dose from CT
             examinations. METHODS: A Monte Carlo program was developed
             to model a CT system (LightSpeed VCT, GE Healthcare). The
             geometry of the system, the energy spectra of the x-ray
             source, the three-dimensional geometry of the bowtie
             filters, and the trajectories of source motions during axial
             and helical scans were explicitly modeled. To validate the
             accuracy of the program, a cylindrical phantom was built to
             enable dose measurements at seven different radial distances
             from its central axis. Simulated radial dose distributions
             in the cylindrical phantom were validated against ion
             chamber measurements for single axial scans at all
             combinations of tube potential and bowtie filter settings.
             The accuracy of the program was further validated using two
             anthropomorphic phantoms (a pediatric one-year-old phantom
             and an adult female phantom). Computer models of the two
             phantoms were created based on their CT data and were
             voxelized for input into the Monte Carlo program. Simulated
             dose at various organ locations was compared against
             measurements made with thermoluminescent dosimetry chips for
             both single axial and helical scans. RESULTS: For the
             cylindrical phantom, simulations differed from measurements
             by -4.8% to 2.2%. For the two anthropomorphic phantoms, the
             discrepancies between simulations and measurements ranged
             between (-8.1%, 8.1%) and (-17.2%, 13.0%) for the single
             axial scans and the helical scans, respectively.
             CONCLUSIONS: The authors developed an accurate Monte Carlo
             program for assessing radiation dose from CT examinations.
             When combined with computer models of actual patients, the
             program can provide accurate dose estimates for specific
             patients.},
   Language = {eng},
   Doi = {10.1118/1.3515839},
   Key = {fds269403}
}

@article{fds269417,
   Author = {Li, X and Samei, E and Segars, WP and Sturgeon, GM and Colsher, JG and Toncheva, G and Yoshizumi, TT and Frush, DP},
   Title = {Patient-specific radiation dose and cancer risk estimation
             in CT: part II. Application to patients.},
   Journal = {Medical physics},
   Volume = {38},
   Number = {1},
   Pages = {408-419},
   Year = {2011},
   Month = {January},
   ISSN = {0094-2405},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/21361209},
   Keywords = {Adult • Child • Female • Humans •
             Individualized Medicine • Infant • Male •
             Neoplasms, Radiation-Induced • Organs at Risk •
             Radiation Dosage* • Risk Assessment • Tomography,
             X-Ray Computed • adverse effects* • etiology*
             • methods* • radiation effects},
   Abstract = {PURPOSE: Current methods for estimating and reporting
             radiation dose from CT examinations are largely
             patient-generic; the body size and hence dose variation from
             patient to patient is not reflected. Furthermore, the
             current protocol designs rely on dose as a surrogate for the
             risk of cancer incidence, neglecting the strong dependence
             of risk on age and gender. The purpose of this study was to
             develop a method for estimating patient-specific radiation
             dose and cancer risk from CT examinations. METHODS: The
             study included two patients (a 5-week-old female patient and
             a 12-year-old male patient), who underwent 64-slice CT
             examinations (LightSpeed VCT, GE Healthcare) of the chest,
             abdomen, and pelvis at our institution in 2006. For each
             patient, a nonuniform rational B-spine (NURBS) based
             full-body computer model was created based on the patient's
             clinical CT data. Large organs and structures inside the
             image volume were individually segmented and modeled. Other
             organs were created by transforming an existing adult male
             or female full-body computer model (developed from visible
             human data) to match the framework defined by the segmented
             organs, referencing the organ volume and anthropometry data
             in ICRP Publication 89. A Monte Carlo program previously
             developed and validated for dose simulation on the
             LightSpeed VCT scanner was used to estimate patient-specific
             organ dose, from which effective dose and risks of cancer
             incidence were derived. Patient-specific organ dose and
             effective dose were compared with patient-generic CT dose
             quantities in current clinical use: the volume-weighted CT
             dose index (CTDIvol) and the effective dose derived from the
             dose-length product (DLP). RESULTS: The effective dose for
             the CT examination of the newborn patient (5.7 mSv) was
             higher but comparable to that for the CT examination of the
             teenager patient (4.9 mSv) due to the size-based clinical CT
             protocols at our institution, which employ lower scan
             techniques for smaller patients. However, the overall risk
             of cancer incidence attributable to the CT examination was
             much higher for the newborn (2.4 in 1000) than for the
             teenager (0.7 in 1000). For the two pediatric-aged patients
             in our study, CTDIvol underestimated dose to large organs in
             the scan coverage by 30%-48%. The effective dose derived
             from DLP using published conversion coefficients differed
             from that calculated using patient-specific organ dose
             values by -57% to 13%, when the tissue weighting factors of
             ICRP 60 were used, and by -63% to 28%, when the tissue
             weighting factors of ICRP 103 were used. CONCLUSIONS: It is
             possible to estimate patient-specific radiation dose and
             cancer risk from CT examinations by combining a validated
             Monte Carlo program with patient-specific anatomical models
             that are derived from the patients' clinical CT data and
             supplemented by transformed models of reference adults. With
             the construction of a large library of patient-specific
             computer models encompassing patients of all ages and weight
             percentiles, dose and risk can be estimated for any patient
             prior to or after a CT examination. Such information may aid
             in decisions for image utilization and can further guide the
             design and optimization of CT technologies and scan
             protocols.},
   Language = {eng},
   Doi = {10.1118/1.3515864},
   Key = {fds269417}
}

@article{fds269331,
   Author = {Richard, S and Li, X and Yadava, G and Samei, E},
   Title = {Predictive models for observer performance in CT:
             Applications in protocol optimization},
   Journal = {Proceedings of SPIE},
   Volume = {7961},
   Year = {2011},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.877069},
   Abstract = {The relationship between theoretical descriptions of imaging
             performance (Fourier-based) and the performance of real
             human observers was investigated for detection tasks in
             multi-slice CT. The detectability index for the
             Fisher-Hotelling model observer and non-prewhitening model
             observer (with and without internal noise and eye filter)
             was computed using: 1) the measured modulation transfer
             function (MTF) and noise-power spectrum (NPS) for CT; and 2)
             a Fourier description of imaging task. Based upon CT images
             of human patients with added simulated lesions, human
             observer performance was assessed via an observer study in
             terms of the area under the ROC curve (Az). The degree to
             which the detectability index correlated with human observer
             performance was investigated and results for the
             non-prewhitening model observer with internal noise and eye
             filter (NPWE) were found to agree best with human
             performance over a broad range of imaging conditions.
             Results provided initial validation that CT image
             acquisition and reconstruction parameters can be optimized
             for observer performance rather than system performance
             (i.e., contrast-to-noise ratio, MTF, and NPS). The NPWE
             model was further applied for the comparison of FBP with a
             novel modelbased iterative reconstruction algorithm to
             assess its potential for dose reduction.},
   Doi = {10.1117/12.877069},
   Key = {fds269331}
}

@article{fds269332,
   Author = {Richard, S and Samei, E},
   Title = {3D task-based performance assessment metrics for
             optimization of performance and dose in breast
             tomosynthesis},
   Journal = {Proceedings of SPIE},
   Volume = {7961},
   Year = {2011},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.877070},
   Abstract = {This study aimed to investigate a method for empirically
             evaluating 3D imaging task performance of breast
             tomosynthesis imaging systems. A simulation and experimental
             approach was used to develop a robust method for performance
             assessment. To identify a method for experimentally
             assessing the 3D modulation transfer function (MTF), a
             breast tomosysnthesis system was first simulated using
             cascaded system analysis to model the signal and noise
             characteristics of the projections. A range of spheres with
             varying contrast and size were reconstructed using filtered
             back projection from which the 3D MTF was evaluated. Results
             revealed that smaller spheres result in lower artifacts in
             the measured MTF, where a sphere of 0.5 mm was found ideal
             for experimental purposes. A clinical tomosynthesis unit was
             used as a platform for quantifying the effect of acquisition
             and processing parameters (e.g., angular extent and
             sampling, dose, and voxel size) on breast imaging
             performance. The 3D noise-power spectrum (NPS) was measured
             using a uniform phantom and 3D MTF was measured using 0.5 mm
             ruby spheres. These metrics were combined with a
             mathematical description of imaging task to generate a
             figure of merit called the detectability index for system
             evaluation and optimization. Clinically relevant imaging
             tasks were considered, such as the detection and
             localization of a spherical mass. The detectability index
             was found to provide a useful metric that accounts for the
             complex 3D imaging characteristics of breast tomosynthesis.
             Results highlighted the dependence of optimal technique on
             the imaging task. They further provided initial validation
             of an empirically assessed figure of merit for clinical
             performance assessment and optimization of breast
             tomosynthesis systems. © 2011 SPIE.},
   Doi = {10.1117/12.877070},
   Key = {fds269332}
}

@article{fds269337,
   Author = {Chen, B and Marin, D and Samei, E},
   Title = {A new iodinated liver phantom for the quantitative
             evaluation of advanced CT acquisition and reconstruction
             techniques},
   Journal = {Proceedings of SPIE},
   Volume = {7961},
   Year = {2011},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.878916},
   Abstract = {An iodinated liver phantom is needed for liver CT related
             studies, such as the quantification of lesion contrast.
             Prior studies simulated iodinated hepatic lesions with tubes
             of iodine solution, which involved complications associated
             with the setup, differences from actual lesion morphology,
             and susceptibility to iodine sediments. To develop a
             dedicated liver phantom with anthropomorphic structures and
             solid lesions, we designed a phantom with iodinated liver
             inserts and lesions of different sizes and contrasts. The
             concentration of iodine in liver parenchyma was determined
             according to the HU measured from clinical images. The
             concentrations in high and low contrast lesions were
             selected so as to provide challenging but reasonable
             detection tasks. The application of the liver phantom was
             initially validated at different doses and reconstruction
             settings. © 2011 SPIE.},
   Doi = {10.1117/12.878916},
   Key = {fds269337}
}

@article{fds269356,
   Author = {Li, X and Samei, E and Segars, WP and Paulson, EK and Frush,
             DP},
   Title = {The feasibility of universal DLP-to-risk conversion
             coefficients for body CT protocols},
   Journal = {Proceedings of SPIE},
   Volume = {7961},
   Year = {2011},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.878616},
   Abstract = {The effective dose associated with computed tomography (CT)
             examinations is often estimated from dose-length product
             (DLP) using scanner-independent conversion coefficients.
             Such conversion coefficients are available for a small
             number of examinations, each covering an entire region of
             the body (e.g., head, neck, chest, abdomen and/or pelvis).
             Similar conversion coefficients, however, do not exist for
             examinations that cover a single organ or a sub-region of
             the body, as in the case of a multi-phase liver examination.
             In this study, we extended the DLP-to-effective dose
             conversion coefficient (k factor) to a wide range of body CT
             protocols and derived the corresponding DLP-to-cancer risk
             conversion coefficient (q factor). An extended cardiactorso
             (XCAT) computational model was used, which represented a
             reference adult male patient. A range of body CT protocols
             used in clinical practice were categorized based on
             anatomical regions examined into 10 protocol classes. A
             validated Monte Carlo program was used to estimate the organ
             dose associated with each protocol class. Assuming the
             reference model to be 20 years old, effective dose and risk
             index (an index of the total risk for cancer incidence) were
             then calculated and normalized by DLP to obtain the k and q
             factors. The k and q factors varied across protocol classes;
             the coefficients of variation were 28% and 9%, respectively.
             The small variation exhibited by the q factor suggested the
             feasibility of universal q factors for a wide range of body
             CT protocols. © 2011 SPIE.},
   Doi = {10.1117/12.878616},
   Key = {fds269356}
}

@article{fds269363,
   Author = {Lin, Y and Samei, E and Luo, H and Iii, JTD and McAdams, HP and Wang, X and Sehnert, WJ and Barski, L and Foos, DH},
   Title = {A patient image-based technique to assess the image quality
             of clinical chest radiographs},
   Journal = {Proceedings of SPIE},
   Volume = {7961},
   Year = {2011},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.878765},
   Abstract = {Current clinical image quality assessment techniques mainly
             analyze image quality for the imaging system in terms of
             factors such as the capture system DQE and MTF, the exposure
             technique, and the particular image processing method and
             processing parameters. However, when assessing a clinical
             image, radiologists seldom refer to these factors, but
             rather examine several specific regions of the image to see
             whether the image is suitable for diagnosis. In this work,
             we developed a new strategy to learn and simulate
             radiologists' evaluation process on actual clinical chest
             images. Based on this strategy, a preliminary study was
             conducted on 254 digital chest radiographs (38 AP without
             grids, 35 AP with 6:1 ratio grids and 151 PA with 10:1 ratio
             grids). First, ten regional based perceptual qualities were
             summarized through an observer study. Each quality was
             characterized in terms of a physical quantity measured from
             the image, and as a first step, the three physical
             quantities in lung region were then implemented
             algorithmically. A pilot observer study was performed to
             verify the correlation between image perceptual qualities
             and physical quantitative qualities. The results
             demonstrated that our regional based metrics have promising
             performance for grading perceptual properties of chest
             radiographs. © 2011 SPIE.},
   Doi = {10.1117/12.878765},
   Key = {fds269363}
}

@article{fds269368,
   Author = {Chen, B and Samei, E and Colsher, J and Barnhart, H and Marin, D and Nelson, R},
   Title = {Precision of iodine quantification in hepatic CT: Effects of
             reconstruction (FBP and MBIR) and imaging
             parameters},
   Journal = {Proceedings of SPIE},
   Volume = {7961},
   Year = {2011},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.878833},
   Abstract = {In hepatic CT imaging, the lesion enhancement after the
             injection of contrast media is of quantitative interest.
             However, the precision of this quantitative measurement may
             be dependent on the imaging techniques such as dose and
             reconstruction algorithm. To determine the impact of
             different techniques, we scanned an iodinated liver phantom
             with acquisition protocols of different dose levels, and
             reconstructed images with different algorithms (FBP and
             MBIR) and slice thicknesses. The contrast of lesions was
             quantified from the images, and its precision was calculated
             for each protocol separately. Results showed that precision
             was improved by increasing dose, increasing slice thickness,
             and using MBIR reconstruction. When using MBIR instead of
             FBP, the same precision can be achieved at 50% less dose. To
             our knowledge, this is the first investigation of the
             quantification precision in hepatic CT imaging using
             iterative reconstructions. © 2011 SPIE.},
   Doi = {10.1117/12.878833},
   Key = {fds269368}
}

@article{fds269413,
   Author = {Kim, S and Song, H and Samei, E and Yin, F-F and Yoshizumi,
             TT},
   Title = {Computed tomography dose index and dose length product for
             cone-beam CT: Monte Carlo simulations of a commercial
             system},
   Journal = {Journal of applied clinical medical physics / American
             College of Medical Physics},
   Volume = {12},
   Number = {2},
   Pages = {84-95},
   Year = {2011},
   ISSN = {1526-9914},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/21587186},
   Keywords = {Calibration • Computer Simulation • Cone-Beam
             Computed Tomography • Equipment Design • Film
             Dosimetry • Humans • Models, Statistical •
             Monte Carlo Method • Phantoms, Imaging • Radiation
             Dosage • Radiometry • Tomography, X-Ray Computed
             • methods • methods*},
   Abstract = {Dosimetry in kilovoltage cone beam computed tomography
             (CBCT) is a challenge due to the limitation of physical
             measurements. To address this, we used a Monte Carlo (MC)
             method to estimate the CT dose index (CTDI) and the dose
             length product (DLP) for a commercial CBCT system. As Dixon
             and Boone(1) showed that CTDI concept can be applicable to
             both CBCT and conventional CT, we evaluated weighted CT dose
             index (CTDIw) and DLP for a commercial CBCT system. Two
             extended CT phantoms were created in our BEAMnrc/EGSnrc MC
             system. Before the simulations, the beam collimation of a
             Varian On-Board Imager (OBI) system was measured with
             radiochromic films (model: XR-QA). The MC model of the OBI
             X-ray tube, validated in a previous study, was used to
             acquire the phase space files of the full-fan and half-fan
             cone beams. Then, DOSXYZnrc user code simulated a total of
             20 CBCT scans for the nominal beam widths from 1 cm to 10
             cm. After the simulations, CBCT dose profiles at center and
             peripheral locations were extracted and integrated (dose
             profile integral, DPI) to calculate the CTDI per each beam
             width. The weighted cone-beam CTDI (CTDIw,l) was calculated
             from DPI values and mean CTDIw,l (CTDIw,l) and DLP were
             derived. We also evaluated the differences of CTDIw,1 values
             between MC simulations and point dose measurements using
             standard CT phantoms. In results, it was found that,CTDI600w
             was 8.74 ± 0.01 cGy for head and CTDI900w was 4.26 ± 0.01
             cGy for body scan. The DLP was found to be proportional to
             the beam collimation. We also found that the point dose
             measurements with standard CT phantoms can estimate the CTDI
             within 3% difference compared to the full integrated CTDI
             from the MC method. This study showed the usability of CTDI
             as a dose index and DLP as a total dose descriptor in CBCT
             scans.},
   Language = {eng},
   Key = {fds269413}
}

@article{fds269410,
   Author = {Richard, S and Samei, E},
   Title = {Quantitative breast tomosynthesis: from detectability to
             estimability.},
   Journal = {Medical physics},
   Volume = {37},
   Number = {12},
   Pages = {6157-6165},
   Year = {2010},
   Month = {December},
   ISSN = {0094-2405},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/21302772},
   Keywords = {Breast Neoplasms • Breast* • Fourier Analysis
             • Mammography • Phantoms, Imaging • Radiation
             Dosage • Radiographic Image Enhancement •
             Reproducibility of Results • methods* •
             radiography},
   Abstract = {PURPOSE: This work aimed to extend Fourier-based imaging
             metrics for modeling and predicting quantitative imaging
             performance. The new methodology was applied to the platform
             of breast tomosynthesis for investigating the influence of
             acquisition parameters (e.g., acquisition angle and dose) on
             quantitative imaging performance. METHODS: Two quantitative
             imaging tasks were considered: Area estimation and volume
             estimation of a 4 mm diameter spherical target. The maximum
             likelihood estimator yielded training data to generate a
             size estimation task function, which was combined with the
             MTF and NPS to predict estimation performance by computing
             an "estimability index" analogous to the detectability
             index. Estimation performance for the two tasks was computed
             as a function of acquisition angle and dose. The results
             were used for system optimization in terms of quantitation
             performance and further compared to the detectability index
             for the detection of the same spherical target. RESULTS: The
             estimability index computed with the size estimation tasks
             correlated well with precision measurements for area and
             volume estimation over a broad range of imaging conditions
             and provided a meaningful figure of merit for quantitative
             imaging performance and optimization. The results
             highlighted that optimal breast tomosynthesis acquisition
             parameters depend significantly on imaging task and dose. At
             nominal dose (1.5 mGy), mass detection was optimal at an
             acquisition angle of 85 degrees, while area and volume
             estimation for the same mass were optimal at approximately
             125 degrees and 164 degrees acquisition angles,
             respectively. CONCLUSIONS: These findings provide an initial
             validation that the Fourier-based metrics extended to
             estimation tasks can represent a meaningful metric and
             predictor of quantitative imaging performance. The
             optimization framework also revealed trade-off between
             anatomical noise and system noise in volumetric imaging
             systems potentially identifying different optimal
             acquisition parameters than currently used in breast
             tomosynthesis and CT.},
   Language = {eng},
   Doi = {10.1118/1.3501883},
   Key = {fds269410}
}

@article{fds269404,
   Author = {Marin, D and Nelson, RC and Barnhart, H and Schindera, ST and Ho, LM and Jaffe, TA and Yoshizumi, TT and Youngblood, R and Samei,
             E},
   Title = {Detection of pancreatic tumors, image quality, and radiation
             dose during the pancreatic parenchymal phase: effect of a
             low-tube-voltage, high-tube-current CT technique--preliminary
             results.},
   Journal = {Radiology},
   Volume = {256},
   Number = {2},
   Pages = {450-459},
   Year = {2010},
   Month = {August},
   ISSN = {1527-1315},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/20656835},
   Keywords = {Aged • Aged, 80 and over • Body Burden* •
             Female • Humans • Male • Middle Aged •
             Pancreas • Pancreatic Neoplasms • Pilot Projects
             • Radiation Dosage* • Radiation Protection •
             Reproducibility of Results • Sensitivity and
             Specificity • Tomography, X-Ray Computed •
             methods* • radiography*},
   Abstract = {PURPOSE: To intraindividually compare a low-tube-voltage (80
             kVp), high-tube-current (675 mA) computed tomographic (CT)
             technique with a high-tube-voltage (140 kVp) CT protocol for
             the detection of pancreatic tumors, image quality, and
             radiation dose during the pancreatic parenchymal phase.
             MATERIALS AND METHODS: This prospective, single-center,
             HIPAA-compliant study was approved by the institutional
             review board, and written informed consent was obtained.
             Twenty-seven patients (nine men, 18 women; mean age, 64
             years) with 23 solitary pancreatic tumors underwent
             dual-energy CT. Two imaging protocols were used: 140 kVp and
             385 mA (protocol A) and 80 kVp and 675 mA (protocol B). For
             both protocols, the following variables were compared during
             the pancreatic parenchymal phase: contrast enhancement for
             the aorta, the pancreas, and the portal vein;
             pancreas-to-tumor contrast-to-noise ratio (CNR); noise; and
             effective dose. Two blinded, independent readers
             qualitatively scored the two data sets for tumor detection
             and image quality. Random-effect analysis of variance tests
             were used to compare differences between the two protocols.
             RESULTS: Compared with protocol A, protocol B yielded
             significantly higher contrast enhancement for the aorta
             (508.6 HU vs 221.5 HU, respectively), pancreas (151.2 HU vs
             67.0 HU), and portal vein (189.7 HU vs 87.3 HU), along with
             a greater pancreas-to-tumor CNR (8.1 vs 5.9) (P < .001 for
             all comparisons). No statistically significant difference in
             tumor detection was observed between the two protocols.
             Although standard deviation of image noise increased with
             protocol B (11.5 HU vs 18.6 HU), this protocol significantly
             reduced the effective dose (from 18.5 to 5.1 mSv; P < .001).
             CONCLUSION: A low-tube-voltage, high-tube-current CT
             technique has the potential to improve the enhancement of
             the pancreas and peripancreatic vasculature, improve tumor
             conspicuity, and reduce patient radiation dose during the
             pancreatic parenchymal phase.},
   Language = {eng},
   Doi = {10.1148/radiol.10091819},
   Key = {fds269404}
}

@article{fds269416,
   Author = {Kim, S and Yoo, S and Yin, F-F and Samei, E and Yoshizumi,
             T},
   Title = {Kilovoltage cone-beam CT: comparative dose and image quality
             evaluations in partial and full-angle scan
             protocols.},
   Journal = {Medical physics},
   Volume = {37},
   Number = {7},
   Pages = {3648-3659},
   Year = {2010},
   Month = {July},
   ISSN = {0094-2405},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/20831072},
   Keywords = {Cone-Beam Computed Tomography • Linear Models •
             Phantoms, Imaging • Quality Control • Radiation
             Dosage* • methods*},
   Abstract = {PURPOSE: To assess imaging dose of partial and full-angle
             kilovoltage CBCT scan protocols and to evaluate image
             quality for each protocol. METHODS: The authors obtained the
             CT dose index (CTDI) of the kilovoltage CBCT protocols in an
             on-board imager by ion chamber (IC) measurements and Monte
             Carlo (MC) simulations. A total of six new CBCT scan
             protocols were evaluated: Standard-dose head (100 kVp, 151
             mA s, partial-angle), low-dose head (100 kVp, 75 mA s,
             partial-angle), high-quality head (100 kVp, 754 mA s,
             partial-angle), pelvis (125 kVp, 706 mA s, full-angle),
             pelvis spotlight (125 kVp, 752 mA s, partial-angle), and
             low-dose thorax (110 kVp, 271 mA s, full-angle). Using the
             point dose method, various CTDI values were calculated by
             (1) the conventional weighted CTDI (CTDIw) calculation and
             (2) Bakalyar's method (CTDIwb). The MC simulations were
             performed to obtain the CTDIw and CTDIwb, as well as from
             (3) central slice averaging (CTDI(2D)) and (4) volume
             averaging (CTDI(3D)) techniques. The CTDI values of the new
             protocols were compared to those of the old protocols
             (full-angle CBCT protocols). Image quality of the new
             protocols was evaluated following the CBCT image quality
             assurance (QA) protocol [S. Yoo et al., "A quality assurance
             program for the on-board image, "Med. Phys. 33(11),
             4431-4447 (2006)] testing Hounsfield unit (HU) linearity,
             spatial linearity/resolution, contrast resolution, and HU
             uniformity. RESULTS: The CTDI, were found as 6.0, 3.2, 29.0,
             25.4, 23.8, and 7.7 mGy for the new protocols, respectively.
             The CTDI, and CTDIwb differed within +3% between IC
             measurements and MC simulations. Method (2) results were
             within +/- 12% of method (1). In MC simulations, the CTDIw
             and CTDIwb were comparable to the CTDI(2D) and CTDI(3D) with
             the differences ranging from -4.3% to 20.6%. The CTDI(3D)
             were smallest among all the CTDI values. CTDIw of the new
             protocols were found as approximately 14 times lower for
             standard head scan and 1.8 times lower for standard body
             scan than the old protocols, respectively. In the image
             quality QA tests, all the protocols except low-dose head and
             low-dose thorax protocols were within the tolerance in the
             HU verification test. The HU value for the two protocols was
             always higher than the nominal value. All the protocols
             passed the spatial linearity/resolution and HU uniformity
             tests. In the contrast resolution test, only high-quality
             head and pelvis scan protocols were within the tolerance. In
             addition, crescent effect was found in the partial-angle
             scan protocols. CONCLUSIONS: The authors found that CTDIw of
             the new CBCT protocols has been significantly reduced
             compared to the old protocols with acceptable image quality.
             The CTDIw values in the point dose method were close to the
             volume averaging method within 9%-21% for all the CBCT scan
             protocols. The Bakalyar's method produced more accurate dose
             estimation within 14%. The HU inaccuracy from low-dose head
             and low-dose thorax protocols can render incorrect dose
             results in the treatment planning system. When high
             soft-tissue contrast data are desired, high-quality head or
             pelvis scan protocol is recommended depending on the imaging
             area. The point dose method can be applicable to estimate
             CBCT dose with reasonable accuracy in the clinical
             environment.},
   Language = {eng},
   Doi = {10.1118/1.3438478},
   Key = {fds269416}
}

@article{fds328143,
   Author = {Flynn, M and Samei, E and Badano, A and Roehrig, H},
   Title = {MO-B-201C-01: Color Monitors for Medical
             Workstations},
   Journal = {Medical physics},
   Volume = {37},
   Number = {6Part2},
   Pages = {3337-3337},
   Year = {2010},
   Month = {June},
   url = {http://dx.doi.org/10.1118/1.3469047},
   Doi = {10.1118/1.3469047},
   Key = {fds328143}
}

@article{fds327419,
   Author = {Kim, S and Song, H and Samei, E and Yin, F and Yoshizumi,
             T},
   Title = {SU-GG-I-14: A Method to Estimate Cone-Beam CT Dose Index and
             Cone-Beam Dose Length Product},
   Journal = {Medical physics},
   Volume = {37},
   Number = {6Part3},
   Pages = {3104-3104},
   Year = {2010},
   Month = {June},
   url = {http://dx.doi.org/10.1118/1.3468047},
   Doi = {10.1118/1.3468047},
   Key = {fds327419}
}

@article{fds327420,
   Author = {Kim, S and Yoo, S and Yin, F and Samei, E and Yoshizumi,
             T},
   Title = {SU-GG-I-57: Dose and Image Quality Evaluation for Partial
             and Full-Angle Kilovoltage Cone-Beam CT Protocols},
   Journal = {Medical physics},
   Volume = {37},
   Number = {6Part3},
   Pages = {3114-3114},
   Year = {2010},
   Month = {June},
   url = {http://dx.doi.org/10.1118/1.3468090},
   Doi = {10.1118/1.3468090},
   Key = {fds327420}
}

@article{fds269407,
   Author = {Richard, S and Samei, E},
   Title = {Quantitative imaging in breast tomosynthesis and CT:
             comparison of detection and estimation task
             performance.},
   Journal = {Medical physics},
   Volume = {37},
   Number = {6},
   Pages = {2627-2637},
   Year = {2010},
   Month = {June},
   ISSN = {0094-2405},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/20632574},
   Keywords = {Algorithms* • Artificial Intelligence • Female
             • Humans • Mammography • Pattern Recognition,
             Automated • Phantoms, Imaging • Radiographic Image
             Enhancement • Radiographic Image Interpretation,
             Computer-Assisted • Reproducibility of Results •
             Sensitivity and Specificity • Tomography, X-Ray
             Computed • instrumentation • methods •
             methods*},
   Abstract = {PURPOSE: This work investigates a framework for modeling
             volumetric breast imaging to compare detection and
             estimation task performance and optimize quantitative breast
             imaging. METHODS: Volumetric reconstructions of a breast
             phantom, which incorporated electronic, quantum, and
             anatomical noise with embedded spherical lesions, were
             simulated over a range of acquisition angles varying from 4
             degrees to 204 degrees with a constant total acquisition
             dose of 1.5 mGy. A maximum likelihood estimator was derived
             in terms of the noise power spectrum, which yielded figures
             of merit for quantitative imaging performance in terms of
             accuracy and precision. These metrics were computed for
             estimation of lesion area, volume, and location. Estimation
             task performance was optimized as a function of acquisition
             angle and compared to the performance of a more conventional
             lesion detection task. RESULTS: Results revealed tradeoffs
             between electronic, quantum, and anatomical noise. The
             detection of a 4 mm sphere was optimal at an acquisition
             angle of 84 degrees, where reconstructed images using a
             smaller acquisition angle exhibited increased anatomical
             noise and reconstructed images using a larger acquisition
             angle exhibited increased quantum and electronic noise. For
             all estimation tasks, accuracy was found to be fairly
             constant as a function acquisition angle indicating adequate
             system calibration, whereas a more significant dependence on
             acquisition angle was observed for precision performance.
             Precision for the 2D area estimation task was optimal at
             approximately 104 degrees, while precision of the 3D volume
             estimation task was optimal at larger angles (approximately
             124 degrees). Precision for the localization task showed
             orientation dependence where localization was significantly
             inferior in the depth direction. Overall, precision for
             localization was optimal at larger angles (i.e., > 125
             degrees) compared to the size estimation tasks. Results
             suggested that for quantitative imaging tasks, the
             acquisition angle should be larger than currently used in
             conventional breast tomosynthesis for lesion detection.
             CONCLUSIONS: Analysis of quantitative imaging performance
             using Fourier-based metrics highlights the difference
             between estimation and detection task in volumetric breast
             imaging and provides a meaningful framework for optimizing
             the performance of breast imaging systems for quantitative
             imaging applications.},
   Language = {eng},
   Doi = {10.1118/1.3429025},
   Key = {fds269407}
}

@article{fds269419,
   Author = {Ranger, NT and Lo, JY and Samei, E},
   Title = {A technique optimization protocol and the potential for dose
             reduction in digital mammography.},
   Journal = {Medical physics},
   Volume = {37},
   Number = {3},
   Pages = {962-969},
   Year = {2010},
   Month = {March},
   ISSN = {0094-2405},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/20384232},
   Keywords = {Algorithms* • Body Burden* • Feasibility Studies
             • Female • Humans • Mammography •
             Phantoms, Imaging • Quality Control • Radiation
             Dosage • Radiation Protection • Radiographic Image
             Enhancement • Radiographic Image Interpretation,
             Computer-Assisted • Reproducibility of Results •
             Sensitivity and Specificity • instrumentation •
             methods*},
   Abstract = {Digital mammography requires revisiting techniques that have
             been optimized for prior screen/film mammography systems.
             The objective of the study was to determine optimized
             radiographic technique for a digital mammography system and
             demonstrate the potential for dose reduction in comparison
             to the clinically established techniques based on screen-
             film. An objective figure of merit (FOM) was employed to
             evaluate a direct-conversion amorphous selenium (a-Se) FFDM
             system (Siemens Mammomat Novation(DR), Siemens AG Medical
             Solutions, Erlangen, Germany) and was derived from the
             quotient of the squared signal-difference-to-noise ratio to
             mean glandular dose, for various combinations of technique
             factors and breast phantom configurations including
             kilovoltage settings (23-35 kVp), target/filter combinations
             (Mo-Mo and W-Rh), breast-equivalent plastic in various
             thicknesses (2-8 cm) and densities (100% adipose, 50%
             adipose/50% glandular, and 100% glandular), and simulated
             mass and calcification lesions. When using a W-Rh spectrum,
             the optimized FOM results for the simulated mass and
             calcification lesions showed highly consistent trends with
             kVp for each combination of breast density and thickness.
             The optimized kVp ranged from 26 kVp for 2 cm 100% adipose
             breasts to 30 kVp for 8 cm 100% glandular breasts. The use
             of the optimized W-Rh technique compared to standard Mo-Mo
             techniques provided dose savings ranging from 9% for 2 cm
             thick, 100% adipose breasts, to 63% for 6 cm thick, 100%
             glandular breasts, and for breasts with a 50% adipose/50%
             glandular composition, from 12% for 2 cm thick breasts up to
             57% for 8 cm thick breasts.},
   Language = {eng},
   Doi = {10.1118/1.3276732},
   Key = {fds269419}
}

@article{fds269420,
   Author = {Fleck, MS and Samei, E and Mitroff, SR},
   Title = {Generalized "satisfaction of search": adverse influences on
             dual-target search accuracy.},
   Journal = {Journal of Experimental Psychology: Applied},
   Volume = {16},
   Number = {1},
   Pages = {60-71},
   Year = {2010},
   Month = {March},
   ISSN = {1939-2192},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/20350044},
   Keywords = {Adolescent • Female • Humans • Male •
             Personal Satisfaction* • Radiology • Signal
             Detection, Psychological* • Visual Perception* •
             Young Adult • methods*},
   Abstract = {The successful detection of a target in a radiological
             search can reduce the detectability of a second target, a
             phenomenon termed satisfaction of search (SOS). Given the
             potential consequences, here we investigate the generality
             of SOS with the goal of simultaneously informing radiology,
             cognitive psychology, and nonmedical searches such as
             airport luggage screening. Ten experiments utilizing
             nonmedical searches and untrained searchers suggest that SOS
             is affected by a diverse array of factors, including (1) the
             relative frequency of different target types, (2) external
             pressures (reward and time), and (3) expectations about the
             number of targets present. Collectively, these experiments
             indicate that SOS arises when searchers have a biased
             expectation about the low likelihood of specific targets or
             events, and when they are under pressure to perform
             efficiently. This first demonstration of SOS outside of
             radiology implicates a general heuristic applicable to many
             kinds of searches. In an example like airport luggage
             screening, the current data suggest that the detection of an
             easy-to-spot target (e.g., a water bottle) might reduce
             detection of a hard-to-spot target (e.g., a box
             cutter).},
   Language = {eng},
   Doi = {10.1037/a0018629},
   Key = {fds269420}
}

@article{fds269422,
   Author = {Shafer, CM and Samei, E and Lo, JY},
   Title = {The quantitative potential for breast tomosynthesis
             imaging.},
   Journal = {Medical physics},
   Volume = {37},
   Number = {3},
   Pages = {1004-1016},
   Year = {2010},
   Month = {March},
   ISSN = {0094-2405},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/20384236},
   Keywords = {Algorithms* • Breast Neoplasms • Computer
             Simulation • Feasibility Studies • Female •
             Humans • Imaging, Three-Dimensional • Mammography
             • Models, Biological • Phantoms, Imaging •
             Radiographic Image Enhancement • Radiographic Image
             Interpretation, Computer-Assisted • Reproducibility of
             Results • Sensitivity and Specificity •
             Tomography, X-Ray Computed • instrumentation •
             methods • methods* • physiopathology •
             radiography*},
   Abstract = {PURPOSE: Due to its limited angular scan range, breast
             tomosynthesis has lower resolution in the depth direction,
             which may limit its accuracy in quantifying tissue density.
             This study assesses the quantitative potential of breast
             tomosynthesis using relatively simple reconstruction and
             image processing algorithms. This quantitation could allow
             improved characterization of lesions as well as image
             processing to present tomosynthesis images with the familiar
             appearance of mammography by preserving more low-frequency
             information. METHODS: All studies were based on a Siemens
             prototype MAMMOMAT Novation TOMO breast tomo system with a
             45 degrees total angular span. This investigation was
             performed using both simulations and empirical measurements.
             Monte Carlo simulations were conducted using the breast
             tomosynthesis geometry and tissue-equivalent, uniform,
             voxelized phantoms with cuboid lesions of varying density
             embedded within. Empirical studies were then performed using
             tissue-equivalent plastic phantoms which were imaged on the
             actual prototype system. The material surrounding the
             lesions was set to either fat-equivalent or
             glandular-equivalent plastic. From the simulation
             experiments, the effects of scatter, lesion depth, and
             background material density were studied. The empirical
             experiments studied the effects of lesion depth, background
             material density, x-ray tube energy, and exposure level.
             Additionally, the proposed analysis methods were
             independently evaluated using a commercially available QA
             breast phantom (CIRS Model 11A). All image reconstruction
             was performed with a filtered backprojection algorithm.
             Reconstructed voxel values within each slice were corrected
             to reduce background nonuniformities. RESULTS: The resulting
             lesion voxel values varied linearly with known glandular
             fraction (correlation coefficient R2 > 0.90) under all
             simulated and empirical conditions, including for the
             independent tests with the QA phantom. Analysis of variance
             performed on the fit line parameters revealed statistically
             significant differences between the two different background
             materials and between 28 kVp and the remaining energies (26,
             30, and 32 kVp) for the dense experimental phantom. How
             ever, no significant differences arose between different
             energies for the fatty phantom, nor for any of the many
             other combinations of parameters. CONCLUSIONS: These strong
             linear relationships suggest that breast tomosynthesis image
             voxel values, after being corrected by our outlined methods,
             are highly positively correlated with true tissue density.
             This consistent linearity implies that breast tomosynthesis
             imaging indeed has potential to be quantitative.},
   Language = {eng},
   Doi = {10.1118/1.3285038},
   Key = {fds269422}
}

@article{fds269421,
   Author = {Marin, D and Nelson, RC and Schindera, ST and Richard, S and Youngblood,
             RS and Yoshizumi, TT and Samei, E},
   Title = {Low-tube-voltage, high-tube-current multidetector abdominal
             CT: improved image quality and decreased radiation dose with
             adaptive statistical iterative reconstruction
             algorithm--initial clinical experience.},
   Journal = {Radiology},
   Volume = {254},
   Number = {1},
   Pages = {145-153},
   Year = {2010},
   Month = {January},
   ISSN = {1527-1315},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/20032149},
   Keywords = {Aged • Algorithms • Analysis of Variance •
             Contrast Media • Female • Humans • Iopamidol
             • Liver Neoplasms • Male • Middle Aged •
             Phantoms, Imaging • Prospective Studies •
             Radiation Dosage • Radiographic Image Interpretation,
             Computer-Assisted • Radiography, Abdominal •
             Tomography, X-Ray Computed • administration & dosage
             • instrumentation • instrumentation* •
             radiography*},
   Abstract = {PURPOSE: To investigate whether an adaptive statistical
             iterative reconstruction (ASIR) algorithm improves the image
             quality at low-tube-voltage (80-kVp), high-tube-current
             (675-mA) multidetector abdominal computed tomography (CT)
             during the late hepatic arterial phase. MATERIALS AND
             METHODS: This prospective, single-center HIPAA-compliant
             study was institutional review board approved. Informed
             patient consent was obtained. Ten patients (six men, four
             women; mean age, 63 years; age range, 51-77 years) known or
             suspected to have hypervascular liver tumors underwent
             dual-energy 64-section multidetector CT. High- and
             low-tube-voltage CT images were acquired sequentially during
             the late hepatic arterial phase of contrast enhancement.
             Standard convolution FBP was used to reconstruct 140-kVp
             (protocol A) and 80-kVp (protocol B) image sets, and ASIR
             (protocol C) was used to reconstruct 80-kVp image sets. The
             mean image noise; contrast-to-noise ratio (CNR) relative to
             muscle for the aorta, liver, and pancreas; and effective
             dose with each protocol were assessed. A figure of merit
             (FOM) was computed to normalize the image noise and CNR for
             each protocol to effective dose. Repeated-measures analysis
             of variance with Bonferroni adjustment for multiple
             comparisons was used to compare differences in mean CNR,
             image noise, and corresponding FOM among the three
             protocols. The noise power spectra generated from a custom
             phantom with each protocol were also compared. RESULTS: When
             image noise was normalized to effective dose, protocol C, as
             compared with protocols A (P = .0002) and B (P = .0001),
             yielded an approximately twofold reduction in noise. When
             the CNR was normalized to effective dose, protocol C yielded
             significantly higher CNRs for the aorta, liver, and pancreas
             than did protocol A (P = .0001 for all comparisons) and a
             significantly higher CNR for the liver than did protocol B
             (P = .003). Mean effective doses were 17.5 mSv +/- 0.6
             (standard error) with protocol A and 5.1 mSv +/- 0.3 with
             protocols B and C. Compared with protocols A and B, protocol
             C yielded a small but quantifiable noise reduction across
             the entire spectrum of spatial frequencies. CONCLUSION:
             Compared with standard FBP reconstruction, an ASIR algorithm
             improves image quality and has the potential to decrease
             radiation dose at low-tube-voltage, high-tube-current
             multidetector abdominal CT during the late hepatic arterial
             phase.},
   Language = {eng},
   Doi = {10.1148/radiol.09090094},
   Key = {fds269421}
}

@article{fds269241,
   Author = {Thompson, J and Chen, B and Richard, S and Bowsher, J and Samei,
             E},
   Title = {Wide-angle Breast Tomosynthesis: Initial Comparative
             Evaluation},
   Journal = {Proceedings of SPIE - The International Society for Optical
             Engineering},
   Volume = {7622},
   Year = {2010},
   ISSN = {0277-786X},
   url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000285047200011&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
   Doi = {10.1117/12.845649},
   Key = {fds269241}
}

@article{fds269242,
   Author = {Richard, S and Chen, B and Samei, E},
   Title = {Extending the Detectability Index to Quantitative Imaging
             Performance: Applications in Tomosynthesis and
             CT},
   Journal = {Proceedings of SPIE - The International Society for Optical
             Engineering},
   Volume = {7622},
   Year = {2010},
   ISSN = {0277-786X},
   url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000285047200033&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
   Doi = {10.1117/12.845286},
   Key = {fds269242}
}

@article{fds269243,
   Author = {Jacobs, J and Marshall, N and Cockmartin, L and Zanca, F and van Engen,
             R and Young, K and Bosmans, H and Samei, E},
   Title = {Towards an international consensus strategy for periodic
             quality control of digital breast tomosynthesis
             systems},
   Journal = {Proceedings of SPIE - The International Society for Optical
             Engineering},
   Volume = {7622},
   Year = {2010},
   ISSN = {0277-786X},
   url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000285047200015&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
   Doi = {10.1117/12.844228},
   Key = {fds269243}
}

@article{fds269262,
   Author = {Samei, E and Li, X and Chen, B and Reiman, R},
   Title = {The myth of mean dose as a surrogate for radiation
             risk?},
   Journal = {Proceedings of SPIE - The International Society for Optical
             Engineering},
   Volume = {7622},
   Year = {2010},
   ISSN = {0277-786X},
   url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000285047200027&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
   Doi = {10.1117/12.845940},
   Key = {fds269262}
}

@article{fds269263,
   Author = {Chen, B and Richard, S and Barnhart, H and Colsher, J and Amurao, M and Samei, E},
   Title = {Quantitative CT: Technique Dependency of Volume Assessment
             for Pulmonary Nodules},
   Journal = {Proceedings of SPIE - The International Society for Optical
             Engineering},
   Volume = {7622},
   Year = {2010},
   ISSN = {0277-786X},
   url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000285047200100&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
   Doi = {10.1117/12.845493},
   Key = {fds269263}
}

@article{fds269277,
   Author = {Lia, X and Samei, E and Segars, WP and Sturgeon, GM and Colsher, JG and Frush, DP},
   Title = {Patient-Specific Radiation Dose and Cancer Risk Estimation
             in Pediatric Chest CT: A Study in 30 Patients},
   Journal = {Proceedings of SPIE - The International Society for Optical
             Engineering},
   Volume = {7622},
   Year = {2010},
   ISSN = {0277-786X},
   url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000285047200053&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
   Doi = {10.1117/12.845491},
   Key = {fds269277}
}

@article{fds269328,
   Author = {Shepard, SJ and Wang, J and Flynn, M and Gingold, E and Goldman, L and Krugh, K and Leong, DL and Mah, E and Ogden, K and Peck, D and Samei, E and Willis, CE},
   Title = {Erratum: An exposure indicator for digital radiography: AAPM
             Task Group 116 (Executive Summary) (Medical Physics (2009)
             36 (2898-2914))},
   Journal = {Medical physics},
   Volume = {37},
   Number = {1},
   Pages = {405-},
   Year = {2010},
   ISSN = {0094-2405},
   url = {http://dx.doi.org/10.1118/1.3266686},
   Doi = {10.1118/1.3266686},
   Key = {fds269328}
}

@article{fds269329,
   Author = {Jacobs, J and Marshall, N and Cockmartin, L and Samei, E and Bosmans,
             H},
   Title = {Constancy checking of digital breast tomosynthesis
             systems},
   Journal = {Lecture notes in computer science},
   Volume = {6136 LNCS},
   Pages = {518-525},
   Year = {2010},
   ISSN = {0302-9743},
   url = {http://dx.doi.org/10.1007/978-3-642-13666-5_70},
   Abstract = {As the number of installed digital breast tomosynthesis
             (DBT) systems increases, the need for quality control
             routines rises. Current work reports on our initial
             experience with a newly developed method for the analysis of
             DBT acquisitions of a homogenous phantom. Both the
             uniformity of the projection as of the reconstruction data
             is analyzed, together with the in-plane and inter-plane
             noise variations. The approach was tested in 2 different
             ways: on DBT projection and reconstructed data of different
             vendors and via simulations of potential detector artifacts
             known from 2D mammography into the projection images of the
             DBT (and followed by reconstruction of the hybrid data). The
             following potentially disturbing artifacts were observed:
             localized detector artifacts, modification of reconstruction
             software settings and synchronization issues. Our results
             indicate that the proposed method could be an easy and
             reliable way of performing constancy checking of DBT
             systems. © 2010 Springer-Verlag.},
   Doi = {10.1007/978-3-642-13666-5_70},
   Key = {fds269329}
}

@article{fds269330,
   Author = {Lin, Y and Wang, X and Sehnert, WJ and Foos, DH and Barski, L and Samei,
             E},
   Title = {Quantification of radiographic image quality based on
             patient anatomical contrast-to-noise ratio: A preliminary
             study with chest images},
   Journal = {Proceedings of SPIE},
   Volume = {7627},
   Year = {2010},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.847033},
   Abstract = {The quality of a digital radiograph for diagnostic imaging
             depends on many factors, such as the capture system DQE and
             MTF, the exposure technique factors, the patient anatomy,
             and the particular image processing method and processing
             parameters used. Therefore, the overall image quality as
             perceived by the radiologists depends on many factors. This
             work explores objective image quality metrics directly from
             display-ready patient images. A preliminary study was
             conducted based on a multi-frequency analysis of anatomy
             contrast and noise magnitude from 250 computed radiography
             (CR) chest radiographs (150 PA, 50 AP captured with
             anti-scatter grids, and 50 AP without grids). The contrast
             and noise values were evaluated in different sub-bands
             separately according to their frequency properties.
             Contrast-Noise ratio (CNR) was calculated, the results
             correlated well with the human observers' overall impression
             on the images captured with and without grids. © 2010
             Copyright SPIE - The International Society for Optical
             Engineering.},
   Doi = {10.1117/12.847033},
   Key = {fds269330}
}

@article{fds269423,
   Author = {Chawla, AS and Lo, JY and Baker, JA and Samei, E},
   Title = {Optimized image acquisition for breast tomosynthesis in
             projection and reconstruction space.},
   Journal = {Medical physics},
   Volume = {36},
   Number = {11},
   Pages = {4859-4869},
   Year = {2009},
   Month = {November},
   ISSN = {0094-2405},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/19994493},
   Keywords = {Algorithms • Area Under Curve • Bayes Theorem
             • Breast Neoplasms • Clinical Trials as Topic
             • Diagnostic Imaging • Female • Humans •
             Image Processing, Computer-Assisted • Models,
             Theoretical • ROC Curve • diagnosis* •
             methods • methods* • pathology},
   Abstract = {Breast tomosynthesis has been an exciting new development in
             the field of breast imaging. While the diagnostic
             improvement via tomosynthesis is notable, the full potential
             of tomosynthesis has not yet been realized. This may be
             attributed to the dependency of the diagnostic quality of
             tomosynthesis on multiple variables, each of which needs to
             be optimized. Those include dose, number of angular
             projections, and the total angular span of those
             projections. In this study, the authors investigated the
             effects of these acquisition parameters on the overall
             diagnostic image quality of breast tomosynthesis in both the
             projection and reconstruction space. Five mastectomy
             specimens were imaged using a prototype tomosynthesis
             system. 25 angular projections of each specimen were
             acquired at 6.2 times typical single-view clinical dose
             level. Images at lower dose levels were then simulated using
             a noise modification routine. Each projection image was
             supplemented with 84 simulated 3 mm 3D lesions embedded at
             the center of 84 nonoverlapping ROIs. The projection images
             were then reconstructed using a filtered backprojection
             algorithm at different combinations of acquisition
             parameters to investigate which of the many possible
             combinations maximizes the performance. Performance was
             evaluated in terms of a Laguerre-Gauss channelized Hotelling
             observer model-based measure of lesion detectability. The
             analysis was also performed without reconstruction by
             combining the model results from projection images using
             Bayesian decision fusion algorithm. The effect of
             acquisition parameters on projection images and
             reconstructed slices were then compared to derive an
             optimization rule for tomosynthesis. The results indicated
             that projection images yield comparable but higher
             performance than reconstructed images. Both modes, however,
             offered similar trends: Performance improved with an
             increase in the total acquisition dose level and the angular
             span. Using a constant dose level and angular span, the
             performance rolled off beyond a certain number of
             projections, indicating that simply increasing the number of
             projections in tomosynthesis may not necessarily improve its
             performance. The best performance for both projection images
             and tomosynthesis slices was obtained for 15-17 projections
             spanning an angular are of approximately 45 degrees--the
             maximum tested in our study, and for an acquisition dose
             equal to single-view mammography. The optimization framework
             developed in this framework is applicable to other
             reconstruction techniques and other multiprojection
             systems.},
   Language = {eng},
   Doi = {10.1118/1.3231814},
   Key = {fds269423}
}

@article{fds269425,
   Author = {Samei, E and Ranger, NT and MacKenzie, A and Honey, ID and Dobbins, JT and Ravin, CE},
   Title = {Effective DQE (eDQE) and speed of digital radiographic
             systems: an experimental methodology.},
   Journal = {Medical physics},
   Volume = {36},
   Number = {8},
   Pages = {3806-3817},
   Year = {2009},
   Month = {August},
   ISSN = {0094-2405},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/19746814},
   Keywords = {Humans • Mammography • Phantoms, Imaging •
             Radiographic Image Enhancement • Scattering, Radiation
             • Time Factors • methods*},
   Abstract = {Prior studies on performance evaluation of digital
             radiographic systems have primarily focused on the
             assessment of the detector performance alone. However, the
             clinical performance of such systems is also substantially
             impacted by magnification, focal spot blur, the presence of
             scattered radiation, and the presence of an antiscatter
             grid. The purpose of this study is to evaluate an
             experimental methodology to assess the performance of a
             digital radiographic system, including those attributes, and
             to propose a new metric, effective detective quantum
             efficiency (eDQE), a candidate for defining the efficiency
             or speed of digital radiographic imaging systems. The study
             employed a geometric phantom simulating the attenuation and
             scatter properties of the adult human thorax and a
             representative indirect flat-panel-based clinical digital
             radiographic imaging system. The noise power spectrum (NPS)
             was derived from images of the phantom acquired at three
             exposure levels spanning the operating range of the clinical
             system. The modulation transfer function (MTF) was measured
             using an edge device positioned at the surface of the
             phantom, facing the x-ray source. Scatter measurements were
             made using a beam stop technique. The eDQE was then computed
             from these measurements, along with measures of phantom
             attenuation and x-ray flux. The MTF results showed notable
             impact from the focal spot blur, while the NPS depicted a
             large component of structured noise resulting from use of an
             antiscatter grid. The eDQE was found to be an order of
             magnitude lower than the conventional DQE. At 120 kVp,
             eDQE(0) was in the 8%-9% range, fivefold lower than DQE(0)
             at the same technique. The eDQE method yielded reproducible
             estimates of the system performance in a clinically relevant
             context by quantifying the inherent speed of the system,
             that is, the actual signal to noise ratio that would be
             measured under clinical operating conditions.},
   Language = {eng},
   Doi = {10.1118/1.3171690},
   Key = {fds269425}
}

@article{fds269426,
   Author = {Li, X and Samei, E and DeLong, DM and Jones, RP and Gaca, AM and Hollingsworth, CL and Maxfield, CM and Colsher, JG and Frush,
             DP},
   Title = {Pediatric MDCT: towards assessing the diagnostic influence
             of dose reduction on the detection of small lung
             nodules.},
   Journal = {Academic Radiology},
   Volume = {16},
   Number = {7},
   Pages = {872-880},
   Year = {2009},
   Month = {July},
   ISSN = {1878-4046},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/19394875},
   Keywords = {Body Burden* • Child • Child, Preschool •
             Humans • Infant • Lung Neoplasms • Male
             • Pediatrics • Radiation Dosage •
             Reproducibility of Results • Sensitivity and
             Specificity • Solitary Pulmonary Nodule •
             Tomography, X-Ray Computed • methods • methods*
             • radiography*},
   Abstract = {RATIONALE AND OBJECTIVES: The purpose of this study was to
             evaluate the effect of reduced tube current (dose) on lung
             nodule detection in pediatric multidetector array computed
             tomography (MDCT). MATERIALS AND METHODS: The study included
             normal clinical chest MDCT images of 13 patients (aged 1-7
             years) scanned at tube currents of 70 to 180 mA. Calibrated
             noise addition software was used to simulate cases as they
             would have been acquired at 70 mA (the lowest original tube
             current), 35 mA (50% reduction), and 17.5 mA (75%
             reduction). Using a validated nodule simulation technique,
             small lung nodules of 3 to 5 mm in diameter were inserted
             into the cases, which were then randomized and rated
             independently by three experienced pediatric radiologists
             for nodule presence on a continuous scale ranging from zero
             (definitely absent) to 100 (definitely present). The
             observer data were analyzed to assess the influence of dose
             on detection accuracy using the Dorfman-Berbaum-Mets method
             for multiobserver, multitreatment receiver-operating
             characteristic (ROC) analysis and the Williams trend test.
             RESULTS: The areas under the ROC curves were 0.95, 0.91, and
             0.92 at 70, 35, and 17.5 mA, respectively, with standard
             errors of 0.02 and interobserver variability of 0.02. The
             Dorfman-Berbaum-Mets method and the Williams trend test
             yielded P values for the effect of dose of .09 and .05,
             respectively. CONCLUSION: Tube current (dose) has a weak
             effect on the detection accuracy of small lung nodules in
             pediatric MDCT. The effect on detection accuracy of a 75%
             dose reduction was comparable to interobserver variability,
             suggesting a potential for dose reduction.},
   Language = {eng},
   Doi = {10.1016/j.acra.2009.01.028},
   Key = {fds269426}
}

@article{fds269428,
   Author = {Shepard, SJ and Wang, J and Flynn, M and Gingold, E and Goldman, L and Krugh, K and Leong, DL and Mah, E and Ogden, K and Peck, D and Samei, E and Wang, J and Willis, CE},
   Title = {An exposure indicator for digital radiography: AAPM Task
             Group 116 (executive summary).},
   Journal = {Medical physics},
   Volume = {36},
   Number = {7},
   Pages = {2898-2914},
   Year = {2009},
   Month = {July},
   ISSN = {0094-2405},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/19673189},
   Keywords = {Aluminum • Animals • Automation • Calibration
             • Computer Simulation • Copper • Feedback
             • Humans • Mammography • Photons •
             Radiation Dosage • Radiation Monitoring* •
             Radiographic Image Enhancement* • Radiography, Dental
             • Radiography, Thoracic • Spectrum Analysis •
             X-Rays • instrumentation • methods •
             veterinary},
   Abstract = {Digital radiographic imaging systems, such as those using
             photostimulable storage phosphor, amorphous selenium,
             amorphous silicon, CCD, and MOSFET technology, can produce
             adequate image quality over a much broader range of exposure
             levels than that of screen/film imaging systems. In
             screen/film imaging, the final image brightness and contrast
             are indicative of over- and underexposure. In digital
             imaging, brightness and contrast are often determined
             entirely by digital postprocessing of the acquired image
             data. Overexposure and underexposures are not readily
             recognizable. As a result, patient dose has a tendency to
             gradually increase over time after a department converts
             from screen/film-based imaging to digital radiographic
             imaging. The purpose of this report is to recommend a
             standard indicator which reflects the radiation exposure
             that is incident on a detector after every exposure event
             and that reflects the noise levels present in the image
             data. The intent is to facilitate the production of
             consistent, high quality digital radiographic images at
             acceptable patient doses. This should be based not on image
             optical density or brightness but on feedback regarding the
             detector exposure provided and actively monitored by the
             imaging system. A standard beam calibration condition is
             recommended that is based on RQA5 but uses filtration
             materials that are commonly available and simple to use.
             Recommendations on clinical implementation of the indices to
             control image quality and patient dose are derived from
             historical tolerance limits and presented as
             guidelines.},
   Language = {eng},
   Doi = {10.1118/1.3121505},
   Key = {fds269428}
}

@article{fds328144,
   Author = {Richard, S and Samei, E},
   Title = {SU-FF-I-109: Quantitative Breast Tomosynthesis: Development
             of An Estimation Performance Metric and Optimization
             Framework},
   Journal = {Medical physics},
   Volume = {36},
   Number = {6Part4},
   Pages = {2459-2460},
   Year = {2009},
   Month = {June},
   url = {http://dx.doi.org/10.1118/1.3181230},
   Doi = {10.1118/1.3181230},
   Key = {fds328144}
}

@article{fds327671,
   Author = {Shafer, C and Lo, J and Samei, E},
   Title = {MO-FF-A4-01: Evaluation of Background Trend Correction
             Technique in Breast Tomosynthesis Quantitation},
   Journal = {Medical physics},
   Volume = {36},
   Number = {6Part21},
   Pages = {2713-2713},
   Year = {2009},
   Month = {June},
   url = {http://dx.doi.org/10.1118/1.3182295},
   Doi = {10.1118/1.3182295},
   Key = {fds327671}
}

@article{fds269427,
   Author = {Marin, D and Nelson, RC and Samei, E and Paulson, EK and Ho, LM and Boll,
             DT and DeLong, DM and Yoshizumi, TT and Schindera,
             ST},
   Title = {Hypervascular liver tumors: low tube voltage, high tube
             current multidetector CT during late hepatic arterial phase
             for detection--initial clinical experience.},
   Journal = {Radiology},
   Volume = {251},
   Number = {3},
   Pages = {771-779},
   Year = {2009},
   Month = {June},
   ISSN = {1527-1315},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/19346514},
   Keywords = {Adult • Aged • Contrast Media • Female •
             Humans • Iopamidol • Liver Neoplasms • Male
             • Middle Aged • Prospective Studies •
             Radiation Dosage • Radiographic Image Interpretation,
             Computer-Assisted • Statistics, Nonparametric •
             Tomography, X-Ray Computed • blood supply •
             diagnostic use • instrumentation • methods* •
             pathology • radiography*},
   Abstract = {PURPOSE: To intraindividually compare a low tube voltage (80
             kVp), high tube current computed tomographic (CT) technique
             with a standard CT protocol (140 kVp) in terms of image
             quality, radiation dose, and detection of malignant
             hypervascular liver tumors during the late hepatic arterial
             phase. MATERIALS AND METHODS: This prospective single-center
             HIPAA-compliant study had institutional review board
             approval, and written informed consent was obtained.
             Forty-eight patients (31 men, 17 women; age range, 35-77
             years) with 60 malignant hypervascular liver tumors (mean
             diameter, 20.1 mm +/- 16.4 [standard deviation]) were
             enrolled. Pathologic proof of focal lesions was obtained
             with histopathologic analysis for 33 nodules and imaging
             follow-up after a minimum of 12 months for 27 nodules.
             Patients underwent dual-energy 64-section multi-detector row
             CT. By using vendor-specific software, two imaging
             protocols-140 kVp and 385 mA (protocol A) and 80 kVp and 675
             mA (protocol B)-were compared during the late hepatic
             arterial phase of contrast enhancement. Paired t tests were
             used to compare tumor-to-liver contrast-to-noise ratio (CNR)
             for each lesion, mean image noise, and effective dose
             between the two data sets. Three readers qualitatively
             assessed the two data sets in a blinded and independent
             fashion. Lesion detection and characterization and reader
             confidence were recorded, as well as readers' subjective
             evaluations of image quality. Wilcoxon-Mann-Whitney
             statistical analysis was performed on this assessment.
             RESULTS: Image noise increased from 5.7 to 11.4 HU as the
             tube voltage decreased from 140 to 80 kVp (P < .0001),
             resulting in a significantly lower image quality score (4.0
             vs 3.0, respectively) with protocol B according to all
             readers (P < .001). At the same time, protocol B yielded
             significantly higher CNR (8.2 vs 6.4) and lesion conspicuity
             scores (4.6 vs 4.1) than protocol A, along with a lower
             effective dose (5.1 vs 17.5 mSv) (P < .001 for all).
             CONCLUSION: By substantially increasing the tumor-to-liver
             CNR, a low tube voltage, high tube current CT technique
             improves the conspicuity of malignant hypervascular liver
             tumors during the late hepatic arterial phase while
             significantly reducing patient radiation
             dose.},
   Language = {eng},
   Doi = {10.1148/radiol.2513081330},
   Key = {fds269427}
}

@article{fds269429,
   Author = {Saunders, RS and Samei, E and Lo, JY and Baker, JA},
   Title = {Can compression be reduced for breast tomosynthesis? Monte
             carlo study on mass and microcalcification conspicuity in
             tomosynthesis.},
   Journal = {Radiology},
   Volume = {251},
   Number = {3},
   Pages = {673-682},
   Year = {2009},
   Month = {June},
   ISSN = {1527-1315},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/19474373},
   Keywords = {Algorithms • Breast • Breast Neoplasms •
             Calcinosis • Compressive Strength • Humans •
             Imaging, Three-Dimensional • Mammography • Monte
             Carlo Method • Phantoms, Imaging • Radiographic
             Image Enhancement • Radiographic Image Interpretation,
             Computer-Assisted • Sensitivity and Specificity •
             methods* • pathology • physiology •
             radiography*},
   Abstract = {PURPOSE: To assess, in a voxelized anthropomorphic breast
             phantom, how the conspicuity of breast masses and
             microcalcifications may be affected by applying reduced
             breast compression in tomosynthesis. MATERIALS AND METHODS:
             A breast tomosynthesis system was modeled by using a Monte
             Carlo program and a voxelized anthropomorphic breast
             phantom. The Monte Carlo program created simulated
             tomosynthesis projection images, which were reconstructed by
             using filtered back-projection software. Reconstructed
             images were analyzed for mass and microcalcification
             conspicuity, or the ratio of the lesion contrast to the
             anatomic and quantum noise surrounding the lesion. This
             analysis was performed at two compression levels (standard
             and 12.5% reduction) and for two breast compression
             thicknesses (4 and 6 cm). The change in conspicuity was
             analyzed for significance by using a bootstrap method and a
             paired Student t test. RESULTS: While keeping the glandular
             radiation dose constant with respective standard and reduced
             compression levels, the mean mass conspicuities were 1.39
             +/- 0.15 (standard error of the mean) and 1.46 +/- 0.22 for
             a 4-cm breast compression phantom and 1.26 +/- 0.15 and 1.22
             +/- 0.20 for a 6-cm breast phantom, and the mean
             microcalcification conspicuities were 16.2 +/- 2.87 and 18.6
             +/- 2.63 for a 4-cm breast phantom and 11.4 +/- 1.11 and
             10.6 +/- 1.18 for a 6-cm breast compression phantom.
             CONCLUSION: For constant glandular dose, mass and
             microcalcification conspicuity remained approximately
             constant with decreased compression. Constant conspicuity
             implies that reduced compression would have a minimal effect
             on radiologists' performance, which suggests that there is
             justification for a measured reduction of breast compression
             for breast tomosynthesis, increasing the comfort of women
             undergoing the examination.},
   Language = {eng},
   Doi = {10.1148/radiol.2521081278},
   Key = {fds269429}
}

@article{fds269250,
   Author = {Wang, C and Dale, B and Neville, A and Boll, D and Samei, E and Merkle,
             E},
   Title = {Qualitative Effect of Gadolinium on Diffusion-Weighted MR
             Imaging of the Liver, Spleen, Pancreas and Kidney at
             3T},
   Journal = {AJR. American journal of roentgenology},
   Volume = {192},
   Number = {5},
   Year = {2009},
   Month = {May},
   ISSN = {0361-803X},
   url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000265387200187&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
   Key = {fds269250}
}

@article{fds269432,
   Author = {Li, X and Samei, E and Delong, DM and Jones, RP and Gaca, AM and Hollingsworth, CL and Maxfield, CM and Carrico, CWT and Frush,
             DP},
   Title = {Three-dimensional simulation of lung nodules for paediatric
             multidetector array CT.},
   Journal = {British Journal of Radiology},
   Volume = {82},
   Number = {977},
   Pages = {401-411},
   Year = {2009},
   Month = {May},
   ISSN = {1748-880X},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/19153182},
   Keywords = {Algorithms* • Child • Computer Simulation* •
             Humans • Imaging, Three-Dimensional* • Lung
             Neoplasms • ROC Curve • Reproducibility of Results
             • Sarcoma • Solitary Pulmonary Nodule •
             Tomography, X-Ray Computed • methods* •
             radiography • radiography*},
   Abstract = {The purpose of this study was to develop and validate a
             technique for three-dimensional (3D) modelling of small lung
             nodules on paediatric multidetector array computed
             tomography (MDCT) images. Clinical images were selected from
             21 patients (<18 years old) who underwent MDCT examinations.
             Sixteen of the patients had one or more real lung nodules
             with diameters between 2.5 and 6 mm. A mathematical
             simulation technique was developed to emulate the 3D
             characteristics of the real nodules. To validate this
             technique, MDCT images of 34 real nodules and 55 simulated
             nodules were randomised and rated independently by four
             experienced paediatric radiologists on a continuous scale of
             appearance between 0 (definitely not real) and 100
             (definitely real). Receiver operating characteristic (ROC)
             analysis, t-test, and equivalence test were performed to
             assess the radiologists' ability to distinguish between
             simulated and real nodules. The two types of nodules were
             also compared in terms of measured shape and contrast
             profile irregularities. The areas under the ROC curves were
             0.59, 0.60, 0.40, and 0.63 for the four observers. Mean
             score differences between simulated and real nodules were
             -8, -11, 13, and -4 for the four observers with p-values of
             0.17, 0.06, 0.17, and 0.26, respectively. The simulated and
             real nodules were perceptually equivalent and had comparable
             shape and contrast profile irregularities. In conclusion,
             mathematical simulation is a feasible technique for creating
             realistic small lung nodules on paediatric MDCT
             images.},
   Language = {eng},
   Doi = {10.1259/bjr/51749983},
   Key = {fds269432}
}

@article{fds269431,
   Author = {Chawla, AS and Saunders, RS and Singh, S and Lo, JY and Samei,
             E},
   Title = {Towards optimized acquisition scheme for multiprojection
             correlation imaging of breast cancer.},
   Journal = {Academic Radiology},
   Volume = {16},
   Number = {4},
   Pages = {456-463},
   Year = {2009},
   Month = {April},
   ISSN = {1878-4046},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/19268858},
   Keywords = {Algorithms • Artificial Intelligence* • Breast
             Neoplasms • Female • Humans • Imaging,
             Three-Dimensional • Mammography • Pattern
             Recognition, Automated • Radiographic Image Enhancement
             • Radiographic Image Interpretation, Computer-Assisted
             • Reproducibility of Results • Sensitivity and
             Specificity • Statistics as Topic • methods*
             • radiography*},
   Abstract = {RATIONALE AND OBJECTIVES: Correlation imaging (CI) is a form
             of multiprojection imaging in which multiple images of a
             patient are acquired from slightly different angles.
             Information from these images is combined to make the final
             diagnosis. A critical factor affecting the performance of CI
             is its data acquisition scheme, because nonoptimized
             acquisition may distort pathologic indicators. The authors
             describe a computer-aided detection (CADe) methodology to
             optimize the acquisition scheme of CI for superior
             diagnostic accuracy. MATERIALS AND METHODS: Images from 106
             subjects were used. For each subject, 25 angular projections
             of a single breast were acquired. Projection images were
             supplemented with a simulated 3-mm three-dimensional lesion.
             Each projection was then processed using a traditional CADe
             algorithm at high sensitivity, followed by the reduction of
             false-positives by combining the geometric correlation
             information available from the multiple images. The
             performance of the CI system was determined in terms of
             free-response receiver-operating characteristic curves and
             the areas under receiver-operating characteristic curves.
             For optimization, the components of acquisition, such as the
             number of projections and their angular span, were
             systematically changed to investigate which of the many
             possible combinations maximized the obtainable CADe
             sensitivity and specificity. RESULTS: The performance of the
             CI system was improved by increasing the angular span.
             Increasing the number of angular projections beyond a
             certain number did not improve performance. Maximum
             performance was obtained between 7 and 10 projections
             spanning a maximum angular arc of 45 degrees . CONCLUSION:
             The findings suggest the existence of an optimum acquisition
             scheme for CI of the breast. CADe results confirmed earlier
             predictions on the basis of observer models. An optimized CI
             system may be an important diagnostic tool for improved
             breast cancer detection.},
   Language = {eng},
   Doi = {10.1016/j.acra.2008.09.013},
   Key = {fds269431}
}

@article{fds269435,
   Author = {Pollard, BJ and Samei, E and Chawla, AS and Baker, J and Ghate, S and Kim,
             C and Soo, MS and Hashimoto, N},
   Title = {The influence of increased ambient lighting on mass
             detection in mammograms.},
   Journal = {Academic Radiology},
   Volume = {16},
   Number = {3},
   Pages = {299-304},
   Year = {2009},
   Month = {March},
   ISSN = {1878-4046},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/19201358},
   Keywords = {Artifacts • Breast Neoplasms • Computer Terminals*
             • Environment • Female • Humans •
             Lighting • Mammography • Observer Variation •
             Radiographic Image Interpretation, Computer-Assisted •
             Reproducibility of Results • Sensitivity and
             Specificity • Task Performance and Analysis* •
             Visual Perception* • methods* •
             radiography*},
   Abstract = {RATIONALE AND OBJECTIVES: Recent research has provided
             evidence that in reading rooms equipped with liquid crystal
             displays (LCDs), a measured increase of ambient lighting may
             improve clinicians' detection performance. In agreement with
             this research, the American College of Radiology (ACR) has
             recommended a moderate increase of ambient lighting in
             mammography reading rooms. This study was designed to
             examine the effect of a controlled increase of ambient
             lighting in mammography reading rooms on the diagnostic
             performance of breast imaging radiologists. MATERIALS AND
             METHODS: Four breast imaging radiologists read 86 mammograms
             (43 containing subtle cancerous masses and 43 normal) under
             low (E = 1 lux) and elevated (E = 50 lux) ambient lighting
             levels on a Digital Imaging and Communications in
             Medicine-calibrated, medical-grade LCD. Radiologists were
             asked to identify cancerous masses and to rate their
             detection confidence. Observer areas under the curve (AUCs)
             were calculated using a receiver-operating characteristic
             analysis of fully paired results. Additionally, average
             observer selection times under both ambient lighting levels
             were determined. RESULTS: Average radiologist AUCs decreased
             with elevated ambient lighting (0.78 +/- 0.03 to 0.72 +/-
             0.04). Observer performance differences, however, were of
             the same order of magnitude as interobserver variability and
             were not statistically significant. Average selection times
             under increased ambient lighting remained constant or
             decreased, with the greatest decrease occurring for
             false-positive (20.4 +/- 18.9 to 14.4 +/- 9.6 seconds) and
             true-positive (18.0 +/- 13.8 to 12.9 +/- 9.4 seconds)
             selections. CONCLUSION: The results agree with those of
             previous studies in that observer performance differences
             under a controlled increase of ambient lighting are not
             statistically significant. On the basis of these findings
             and ACR guidelines, a moderate increase of ambient lighting
             in mammography reading rooms is still suggested, but further
             research with additional cases and observers should be
             considered.},
   Language = {eng},
   Doi = {10.1016/j.acra.2008.08.017},
   Key = {fds269435}
}

@article{fds269433,
   Author = {Castella, C and Eckstein, MP and Abbey, CK and Kinkel, K and Verdun, FR and Saunders, RS and Samei, E and Bochud, FO},
   Title = {Mass detection on mammograms: influence of signal shape
             uncertainty on human and model observers.},
   Journal = {Journal of the Optical Society of America
             A},
   Volume = {26},
   Number = {2},
   Pages = {425-436},
   Year = {2009},
   Month = {February},
   ISSN = {1084-7529},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/19183697},
   Keywords = {Artificial Intelligence* • Breast Neoplasms •
             Computer Simulation • Early Detection of Cancer* •
             Humans • Mammography • Observer Variation •
             Radiographic Image Interpretation, Computer-Assisted •
             Uncertainty* • methods* • radiography},
   Abstract = {We studied the influence of signal variability on human and
             model observers for detection tasks with realistic simulated
             masses superimposed on real patient mammographic backgrounds
             and synthesized mammographic backgrounds (clustered lumpy
             backgrounds, CLB). Results under the signal-known-exactly
             (SKE) paradigm were compared with signal-known-statistically
             (SKS) tasks for which the observers did not have prior
             knowledge of the shape or size of the signal. Human
             observers' performance did not vary significantly when
             benign masses were superimposed on real images or on CLB.
             Uncertainty and variability in signal shape did not degrade
             human performance significantly compared with the SKE task,
             while variability in signal size did. Implementation of
             appropriate internal noise components allowed the fit of
             model observers to human performance.},
   Language = {eng},
   Key = {fds269433}
}

@article{fds269434,
   Author = {Li, X and Samei, E},
   Title = {Comparison of patient size-based methods for estimating
             quantum noise in CT images of the lung.},
   Journal = {Medical physics},
   Volume = {36},
   Number = {2},
   Pages = {541-546},
   Year = {2009},
   Month = {February},
   ISSN = {0094-2405},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/19291993},
   Keywords = {Body Size* • Humans • Image Processing,
             Computer-Assisted • Lung • Phantoms, Imaging
             • Tomography, X-Ray Computed • Water •
             methods* • physiology* • radiography* •
             standards},
   Abstract = {The authors explored four methods for estimating quantum
             noise in CT images of the lung, each based on a different
             definition of patient size (water-equivalent diameter) and
             the relationship between noise and diameter determined in
             water phantoms. The accuracies of the four methods were
             evaluated using an image-subtraction method as a gold
             standard. Noise estimates based on patient sizes derived
             from chest area, water-equivalent area, non-lung area, and
             water-equivalent path length had maximum errors of 229%,
             93%, 34%, and 57%, respectively. Considering the magnitude
             of noise variation across the lung volume (approximately
             30%), noise estimate based on non-lung area was reasonably
             accurate.},
   Language = {eng},
   Doi = {10.1118/1.3058482},
   Key = {fds269434}
}

@article{fds269348,
   Author = {Chawla, AS and Samei, E and Lo, JY},
   Title = {Optimized lesion detection in breast tomosynthesis},
   Journal = {Proceedings of SPIE},
   Volume = {7258},
   Year = {2009},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.813964},
   Abstract = {While diagnostic improvement via breast tomosynthesis has
             been notable, the full potential of tomosynthesis has not
             yet been realized. This is because of the complex task of
             optimizing multiple parameters that constitute image
             acquisition and thus affect tomosynthesis performance. Those
             parameters include dose, number of angular projections, and
             the total angular span of those projections. In this study,
             we investigated the effects of acquisition parameters,
             independent of each other, on the overall diagnostic image
             quality of tomosynthesis. Five mastectomy specimens were
             imaged using a prototype tomosynthesis system. 25 angular
             projections of each specimen were acquired at 6.2 times
             typical single-view mammographic dose level. Images at lower
             dose levels were then simulated using a noise modification
             routine. Each projection image was supplemented with 84
             simulated 3 mm 3D lesions embedded at the center of 84
             non-overlapping ROIs. The projection images were then
             reconstructed using a filtered-back projection (FBP)
             algorithm at 224 different combinations of acquisition
             parameters to investigate which one of the many possible
             combinations maximized performance. Performance was
             evaluated in terms of a Laguerre-Gauss channelized Hotelling
             observer model-based measure of lesion detectability.
             Results showed that performance improved with an increase in
             the total acquisition dose level and the angular span. At a
             constant dose level and angular span, the performance
             rolled-off beyond a certain number of projections,
             indicating that simply increasing the number of projections
             in tomosynthesis may not necessarily improve its
             performance. The best performance was obtained with 15-17
             projections spanning an angular arc of ~45° - the maximum
             tested in our study, and for an acquisition dose equal to
             single-view mammography. The optimization framework
             developed in this framework is applicable to other
             reconstruction techniques and other multi-projection
             systems. © 2009 SPIE.},
   Doi = {10.1117/12.813964},
   Key = {fds269348}
}

@article{fds269325,
   Author = {Ertan, F and Mackenzie, A and Urbanczyk, HJ and Ranger, NT and Samei,
             E},
   Title = {Use of effective detective quantum efficiency to optimise
             radiographic exposures for chest imaging with computed
             radiography},
   Journal = {Proceedings of SPIE},
   Volume = {7258},
   Year = {2009},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.813650},
   Abstract = {The purpose of the work was to test if effective detective
             quantum efficiency (eDQE) could be useful for optimisation
             of radiographic factors for computed radiography (CR) for
             adult chest examinations. The eDQE was therefore measured
             across a range of kilovoltage, with and without an
             anti-scatter grid. The modulation transfer function, noise
             power spectra, transmission factor and scatter fraction were
             measured with a phantom made of sheets of Aluminum and
             Acrylic. The entrance air kerma was selected to give an
             effective dose of 4.9 ìSv. The effective noise equivalent
             quanta (eNEQ) is introduced in this work. eNEQ can be
             considered equal to the number of X-ray quanta equivalent in
             the image corrected for the amount of scatter and the
             blurring processes. The eNEQ was then normalised to account
             for slight differences in the effective dose (eNEQED). The
             peak eNEQED was largest at 80 kV and 100 kV with no grid and
             with grid respectively. At each kilovoltage, the eNEQED and
             eDQE were between 10% and 70% larger when the grid was not
             used. The results show that 80 kV without grid is the most
             suitable exposure conditions for CR in chest. This is
             consistent with clinical practice in the UK and previous
             publications recommending a low kV technique for CR for
             average sized adult chest imaging. © 2009
             SPIE.},
   Doi = {10.1117/12.813650},
   Key = {fds269325}
}

@article{fds269326,
   Author = {Elojeimy, S and Huda, W and Ogden, KM and Owen, R and Samei, E and Rumboldt, Z},
   Title = {The effect of dose reductions on lesion detection in head
             CT},
   Journal = {Proceedings of SPIE},
   Volume = {7258},
   Year = {2009},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.812051},
   Abstract = {The purpose of this study was to quantitatively evaluate the
             effect of reducing radiation dose (i.e., mAs) on lesion
             detection in head CT examinations. We used a simulation
             package (Syngo Explorer) to reconstruct 5-mm thick CT images
             of the brain of one patient pertaining to the centrum
             semiovale, the basal ganglia, and the sella turcica. Lesion
             detection was measured using two Alternate Forced Choice
             (2-AFC) experiments that measure the lesion contrast (I 92%)
             corresponding to a detection accuracy of 92%. Two observers
             performed experiments to investigate detection of low
             contrast lesions with four sizes ranging from 3 mm to 10 mm
             and at four x-ray beam intensities ranging from 105 mAs to
             300 mAs. Results were plotted as log[I 92%] versus log[mAs],
             and the slopes were measured for each lesion size. Lowering
             the mAs always reduced lesion detection performance in all
             images, and for all lesion sizes. Average slopes of the I
             92% versus mAs curves were -0.23 for 3 mm lesions,-0.16 for
             4.5 mm lesions, and ∼-0.11 for the 7 and 10 mm lesions.
             For the smallest lesions investigated (3 mm), doubling the
             x-ray intensity improved lesion detection performance by ∼
             15%, whereas for the largest sized lesions (7 and 10 mm),
             doubling the tube current improved lesion detection
             performance by ∼ 7%. The observed improvements in
             detection performance are markedly lower than predicted by
             the Rose model where a doubling of the tube current would be
             expected to improve detection performance by 29% at all
             lesion sizes. © 2009 SPIE.},
   Doi = {10.1117/12.812051},
   Key = {fds269326}
}

@article{fds269327,
   Author = {Elojeimy, S and Huda, W and Ogden, KM and Owen, R and Samei, E and Rumboldt, Z},
   Title = {Contrast detail curves in head ct examinations},
   Journal = {Proceedings of SPIE},
   Volume = {7263},
   Year = {2009},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.811660},
   Abstract = {The purpose of this study was to generate contrast detail
             (CD) curves for low contrast mass lesions embedded in images
             obtained in head and neck CT examinations. Axial head and
             neck CT slice images were randomly chosen from patients at
             five different levels. All images were acquired at 120 kV,
             and reconstructed using a standard soft tissue
             reconstruction filter. For each head CT image, we measured
             detection of low contrast mass lesions using a 2 Alternate
             Forced Choice (2-AFC) experimental paradigm. In an AFC
             experiment, an observer identifies the lesion location in
             one of two regions of interest. After performing 128
             sequential observations, it is possible to compute the
             lesion contrast corresponding to a 92% accuracy of lesion
             detection (i.e., I92%). Five lesion sizes were investigated
             ranging from 4 mm to 12.5 mm, with the experimental order
             randomized to eliminate learning curve as well as observer
             fatigue. Contrast detail curves were generated by plotting
             log[I92%] versus log[lesion size]. Experimental slopes
             ranged from ~ -0.1 to ~ -0.4. The slope of the CD curve was
             directly related to the complexity of the anatomical
             structure in the head CT image. As the apparent anatomical
             complexity increased, the slope of the corresponding CD
             curve was reduced. Results from our pilot study suggest that
             anatomical structure is of greater importance than quantum
             mottle, and that the type of anatomical background structure
             is an important determinant of lesion detection in CT
             imaging.},
   Doi = {10.1117/12.811660},
   Key = {fds269327}
}

@article{fds269336,
   Author = {Chawla, AS and Boyce, S and Washington, L and McAdams, HP and Samei,
             E},
   Title = {Design and development of a new multi-projection X-ray
             system for chest imaging},
   Journal = {IEEE Transactions on Nuclear Science},
   Volume = {56},
   Number = {1},
   Pages = {36-45},
   Year = {2009},
   ISSN = {0018-9499},
   url = {http://dx.doi.org/10.1109/TNS.2008.2008647},
   Abstract = {Overlapping anatomical structures may confound the detection
             of abnormal pathology, including lung nodules, in
             conventional single-projection chest radiography. To
             minimize this fundamental limiting factor, a dedicated
             digital multi-projection system for chest imaging was
             recently developed at the Radiology Department of Duke
             University. We are reporting the design of the
             multi-projection imaging system and its initial performance
             in an ongoing clinical trial. The system is capable of
             acquiring multiple full-field projections of the same
             patient along both the horizontal and vertical axes at
             variable speeds and acquisition frame rates. These images
             acquired in rapid succession from slightly different angles
             about the posterior-anterior (PA) orientation can be
             correlated to minimize the influence of overlying anatomy.
             The developed system has been tested for repeatability and
             motion blur artifacts to investigate its robustness for
             clinical trials. Excellent geometrical consistency was found
             in the tube motion, with positional errors for clinical
             settings within 1%. The effect of tube-motion on the image
             quality measured in terms of impact on the Modulation
             Transfer Function (MTF) was found to be minimal. The system
             was deemed clinic-ready and a clinical trial was
             subsequently launched. The flexibility of image acquisition
             built into the system provides a unique opportunity to
             easily modify it for different clinical applications,
             including tomosynthesis, correlation imaging (CI), and
             stereoscopic imaging. © 2006 IEEE.},
   Doi = {10.1109/TNS.2008.2008647},
   Key = {fds269336}
}

@article{fds269354,
   Author = {Li, X and Samei, E and Segars, WP and Sturgeon, GM and Colsher, JG and Frush, DP},
   Title = {Patient-specific dose estimation for pediatric
             abdomen-pelvisCT},
   Journal = {Proceedings of SPIE},
   Volume = {7258},
   Year = {2009},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.813531},
   Abstract = {The purpose of this study is to develop a method for
             estimating patient-specific dose from abdomen-pelvis CT
             examinations and to investigate dose variation across
             patients in the same weight group. Our study consisted of
             seven pediatric patients in the same weight/protocol group,
             for whom full-body computer models were previously created
             based on the patients' CT data obtained for clinical
             indications. Organ and effective dose of these patients from
             an abdomen-pelvis scan protocol (LightSpeed VCT scanner,
             120- kVp, 85-90 mA, 0.4-s gantry rotation period,
             1.375-pitch, 40-mm beam collimation, and small body scan
             field-of-view) was calculated using a Monte Carlo program
             previously developed and validated for the same CT system.
             The seven patients had effective dose of 2.4-2.8 mSv,
             corresponding to normalized effective dose of 6.6-8.3
             mSv/100mAs (coefficient of variation: 7.6%). Dose variations
             across the patients were small for large organs in the scan
             coverage (mean: 6.6%; range: 4.9%-9.2%), larger for small
             organs in the scan coverage (mean: 10.3%; range:
             1.4%-15.6%), and the largest for organs partially or
             completely outside the scan coverage (mean: 14.8%; range:
             5.7%-27.7%). Normalized effective dose correlated strongly
             with body weight (correlation coefficient: r = -0.94).
             Normalized dose to the kidney and the adrenal gland
             correlated strongly with mid-liver equivalent diameter
             (kidney: r = -0.97; adrenal glands: r = -0.98). Normalized
             dose to the small intestine correlated strongly with
             mid-intestine equivalent diameter (r = -0.97). These strong
             correlations suggest that patient-specific dose may be
             estimated for any other child in the same size group who
             undergoes the abdomen-pelvis scan. © 2009
             SPIE.},
   Doi = {10.1117/12.813531},
   Key = {fds269354}
}

@article{fds269355,
   Author = {Segars, WP and Sturgeon, G and Li, X and Cheng, L and Ceritoglu, C and Ratnanather, JT and Miller, MI and Tsui, BMW and Frush, D and Samei,
             E},
   Title = {Patient specific computerized phantoms to estimate dose in
             pediatric CT},
   Journal = {Proceedings of SPIE},
   Volume = {7258},
   Year = {2009},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.813517},
   Abstract = {We create a series of detailed computerized phantoms to
             estimate patient organ and effective dose in pediatric CT
             and investigate techniques for efficiently creating
             patient-specific phantoms based on imaging data. The initial
             anatomy of each phantom was previously developed based on
             manual segmentation of pediatric CT data. Each phantom was
             extended to include a more detailed anatomy based on
             morphing an existing adult phantom in our laboratory to
             match the framework (based on segmentation) defined for the
             target pediatric model. By morphing a template anatomy to
             match the patient data in the LDDMM framework, it was
             possible to create a patient specific phantom with many
             anatomical structures, some not visible in the CT data. The
             adult models contain thousands of defined structures that
             were transformed to define them in each pediatric anatomy.
             The accuracy of this method, under different conditions, was
             tested using a known voxelized phantom as the target. Errors
             were measured in terms of a distance map between the
             predicted organ surfaces and the known ones. We also
             compared calculated dose measurements to see the effect of
             different magnitudes of errors in morphing. Despite some
             variations in organ geometry, dose measurements from
             morphing predictions were found to agree with those
             calculated from the voxelized phantom thus demonstrating the
             feasibility of our methods. © 2009 SPIE.},
   Doi = {10.1117/12.813517},
   Key = {fds269355}
}

@article{fds269362,
   Author = {Ranger, NT and Mackenzie, A and Honey, ID and III, JTD and Ravin, CE and Samei, E},
   Title = {Extension of DQE to include scatter, grid, magnification,
             and focal spot blur: A new experimental technique and
             metric},
   Journal = {Proceedings of SPIE},
   Volume = {7258},
   Year = {2009},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.813779},
   Abstract = {In digital radiography, conventional DQE evaluations are
             performed under idealized conditions that do not reflect
             typical clinical operating conditions. For this reason, we
             have developed and evaluated an experimental methodology for
             measuring the effective detective quantum efficiency (eDQE)
             of digital radiographic systems and its utility in chest
             imaging applications.To emulate the attenuation and scatter
             properties of the human thorax across a range of sizes, the
             study employed pediatric and adult geometric chest imaging
             phantoms designed for use in the FDA/CDRH Nationwide
             Evaluation of X-Ray Trends (NEXT) program and a third
             phantom configuration designed to represent the bariatric
             population. The MTF for each phantom configuration was
             measured using images of an opaque edge device placed at the
             nominal surface of each phantom and at a common reference
             point. For each phantom, the NNPS was measured in a uniform
             region within the phantom image acquired at an exposure
             level determined from a prior phototimed acquisition.
             Scatter measurements were made using a beam-stop technique.
             These quantities were used along with measures of phantom
             attenuation and estimates of x-ray flux, to compute the eDQE
             at the beam-entrance surface of the phantoms, reflecting the
             presence of scatter, grid, magnification, and focal spot
             blur. The MTF results showed notable degradation due to
             focal spot blurring enhanced by geometric magnification,
             with increasing phantom size. Measured scatter fractions
             were 33%, 34% and 46% for the pediatric, adult, and
             bariatric phantoms, respectively. Correspondingly, the
             measured narrow beam transmission fractions were 16%, 9%,
             and 3%. The eDQE results for the pediatric and adult
             phantoms correlate well at low spatial frequencies but show
             degradation in the eDQE at increasing spatial frequencies
             for the adult phantom in comparison to the pediatric
             phantom. The results for the bariatric configuration showed
             a marked decrease in eDQE in comparison to the adult phantom
             results, across all spatial frequencies, attributable to the
             combined differences in geometric magnification, and
             scatter. The eDQE metric has been demonstrated to be
             sensitive to body habitus suggesting its usefulness in
             assessing system response across a range of chest sizes and
             potentially making it a useful factor in protocol assessment
             and optimization.©2009 SPIE.},
   Doi = {10.1117/12.813779},
   Key = {fds269362}
}

@article{fds269424,
   Author = {Samei, E and Saunders, RS and Badea, CT and Ghaghada, KB and Hedlund,
             LW and Qi, Y and Yuan, H and Bentley, RC and Mukundan,
             S},
   Title = {Micro-CT imaging of breast tumors in rodents using a
             liposomal, nanoparticle contrast agent.},
   Journal = {International journal of nanomedicine},
   Volume = {4},
   Pages = {277-282},
   Year = {2009},
   ISSN = {1178-2013},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/20011244},
   Keywords = {Animals • Cell Line, Tumor • Contrast Media •
             Female • Iopamidol • Liposomes • Mammary
             Neoplasms, Animal • Mammography • Nanoparticles
             • Radiographic Image Enhancement • Rats •
             Rats, Inbred F344 • Tomography, X-Ray Computed •
             chemistry* • diagnostic use* • methods* •
             radiography*},
   Abstract = {A long circulating liposomal, nanoscale blood pool agent
             encapsulating traditional iodinated contrast agent (65 mg
             I/mL) was used for micro-computed tomography (CT) imaging of
             rats implanted with R3230AC mammary carcinoma.
             Three-dimensional vascular architecture of tumors was imaged
             at 100-micron isotropic resolution. The image data showed
             good qualitative correlation with pathologic findings. The
             approach holds promise for studying tumor angiogenesis and
             for evaluating anti-angiogenesis therapies.},
   Language = {eng},
   Key = {fds269424}
}

@article{fds269430,
   Author = {Li, X and Samei, E and Segars, WP and Sturgeon, GM and Colsher, JG and Frush, DP},
   Title = {Patient-specific dose estimation for pediatric chest
             CT.},
   Journal = {Medical physics},
   Volume = {35},
   Number = {12},
   Pages = {5821-5828},
   Year = {2008},
   Month = {December},
   ISSN = {0094-2405},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/19175138},
   Keywords = {Adolescent • Child • Child, Preschool •
             Female • Humans • Infant • Infant, Newborn
             • Male • Monte Carlo Method • Pediatrics
             • Phantoms, Imaging* • Radiation Dosage •
             Radiography, Thoracic • Radiometry • Tomography,
             X-Ray Computed • methods • methods*},
   Abstract = {Current methods for organ and effective dose estimations in
             pediatric CT are largely patient generic. Physical phantoms
             and computer models have only been developed for
             standard/limited patient sizes at discrete ages (e.g., 0, 1,
             5, 10, 15 years old) and do not reflect the variability of
             patient anatomy and body habitus within the same size/age
             group. In this investigation, full-body computer models of
             seven pediatric patients in the same size/protocol group
             (weight: 11.9-18.2 kg) were created based on the patients'
             actual multi-detector array CT (MDCT) data. Organs and
             structures in the scan coverage were individually segmented.
             Other organs and structures were created by morphing
             existing adult models (developed from visible human data) to
             match the framework defined by the segmented organs,
             referencing the organ volume and anthropometry data in ICRP
             Publication 89. Organ and effective dose of these patients
             from a chest MDCT scan protocol (64 slice LightSpeed VCT
             scanner, 120 kVp, 70 or 75 mA, 0.4 s gantry rotation period,
             pitch of 1.375, 20 mm beam collimation, and small body scan
             field-of-view) was calculated using a Monte Carlo program
             previously developed and validated to simulate radiation
             transport in the same CT system. The seven patients had
             normalized effective dose of 3.7-5.3 mSv/100 mAs
             (coefficient of variation: 10.8%). Normalized lung dose and
             heart dose were 10.4-12.6 mGy/100 mAs and 11.2-13.3 mGy/100
             mAs, respectively. Organ dose variations across the patients
             were generally small for large organs in the scan coverage
             (<7%), but large for small organs in the scan coverage
             (9%-18%) and for partially or indirectly exposed organs
             (11%-77%). Normalized effective dose correlated weakly with
             body weight (correlation coefficient: r=-0.80). Normalized
             lung dose and heart dose correlated strongly with mid-chest
             equivalent diameter (lung: r=-0.99, heart: r=-0.93); these
             strong correlation relationships can be used to estimate
             patient-specific organ dose for any other patient in the
             same size/protocol group who undergoes the chest scan. In
             summary, this work reported the first assessment of dose
             variations across pediatric CT patients in the same
             size/protocol group due to the variability of patient
             anatomy and body habitus and provided a previously
             unavailable method for patient-specific organ dose
             estimation, which will help in assessing patient risk and
             optimizing dose reduction strategies, including the
             development of scan protocols.},
   Language = {eng},
   Doi = {10.1118/1.3026593},
   Key = {fds269430}
}

@article{fds269463,
   Author = {Samei, E and Ranger, NT and MacKenzie, A and Honey, ID and Dobbins, JT and Ravin, CE},
   Title = {Detector or system? Extending the concept of detective
             quantum efficiency to characterize the performance of
             digital radiographic imaging systems.},
   Journal = {Radiology},
   Volume = {249},
   Number = {3},
   Pages = {926-937},
   Year = {2008},
   Month = {December},
   ISSN = {1527-1315},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/19011189},
   Keywords = {Efficiency • Phantoms, Imaging • Radiographic
             Image Enhancement • Radiography, Thoracic •
             Scattering, Radiation • instrumentation* •
             standards • standards*},
   Abstract = {PURPOSE: To develop an experimental method for measuring the
             effective detective quantum efficiency (eDQE) of digital
             radiographic imaging systems and evaluate its use in select
             imaging systems. MATERIALS AND METHODS: A geometric phantom
             emulating the attenuation and scatter properties of the
             adult human thorax was employed to assess eight imaging
             systems in a total of nine configurations. The noise power
             spectrum (NPS) was derived from images of the phantom
             acquired at three exposure levels spanning the operating
             range of the system. The modulation transfer function (MTF)
             was measured by using an edge device positioned at the
             anterior surface of the phantom. Scatter measurements were
             made by using a beam-stop technique. All measurements,
             including those of phantom attenuation and estimates of
             x-ray flux, were used to compute the eDQE. RESULTS: The MTF
             results showed notable degradation owing to focal spot blur.
             Scatter fractions ranged between 11% and 56%, depending on
             the system. The eDQE(0) results ranged from 1%-17%,
             indicating a reduction of up to one order of magnitude and
             different rank ordering and performance among systems,
             compared with that implied in reported conventional
             detective quantum efficiency results from the same systems.
             CONCLUSION: The eDQE method was easy to implement, yielded
             reproducible results, and provided a meaningful reflection
             of system performance by quantifying image quality in a
             clinically relevant context. The difference in the magnitude
             of the measured eDQE and the ideal eDQE of 100% provides a
             great opportunity for improving the image quality of
             radiographic and mammographic systems while reducing patient
             dose.},
   Language = {eng},
   Doi = {10.1148/radiol.2492071734},
   Key = {fds269463}
}

@article{fds269436,
   Author = {Saunders, RS and Samei, E},
   Title = {The effect of breast compression on mass conspicuity in
             digital mammography.},
   Journal = {Medical physics},
   Volume = {35},
   Number = {10},
   Pages = {4464-4473},
   Year = {2008},
   Month = {October},
   ISSN = {0094-2405},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/18975694},
   Keywords = {Breast • Compressive Strength • Humans •
             Mammography • Palpation • Radiographic Image
             Enhancement • Radiographic Image Interpretation,
             Computer-Assisted • Reproducibility of Results •
             Sensitivity and Specificity • methods* •
             physiology*},
   Abstract = {This study analyzed how the inherent quality of diagnostic
             information in digital mammography could be affected by
             breast compression. A digital mammography system was modeled
             using a Monte Carlo algorithm based on the Penelope program,
             which has been successfully used to model several medical
             imaging systems. First, the Monte Carlo program was
             validated against previous measurements and simulations.
             Once validated, the Monte Carlo software modeled a digital
             mammography system by tracking photons through a voxelized
             software breast phantom, containing anatomical structures
             and breast masses, and following photons until they were
             absorbed by a selenium-based flat-panel detector.
             Simulations were performed for two compression conditions
             (standard compression and 12.5% reduced compression) and
             three photon flux conditions (constant flux, constant
             detector signal, and constant glandular dose). The results
             showed that reduced compression led to higher scatter
             fractions, as expected. For the constant photon flux
             condition, decreased compression also reduced glandular
             dose. For constant glandular dose, the SdNR for a 4 cm
             breast was 0.60 +/- 0.11 and 0.62 +/- 0.11 under standard
             and reduced compressions, respectively. For the 6 cm case
             with constant glandular dose, the SdNR was 0.50 +/- 0.11 and
             0.49 +/- 0.10 under standard and reduced compressions,
             respectively. The results suggest that if a particular
             imaging system can handle an approximately 10% increase in
             total tube output and 10% decrease in detector signal,
             breast compression can be reduced by about 12% in terms of
             breast thickness with little impact on image quality or
             dose.},
   Language = {eng},
   Doi = {10.1118/1.2977600},
   Key = {fds269436}
}

@article{fds269438,
   Author = {Singh, S and Tourassi, GD and Baker, JA and Samei, E and Lo,
             JY},
   Title = {Automated breast mass detection in 3D reconstructed
             tomosynthesis volumes: a featureless approach.},
   Journal = {Medical physics},
   Volume = {35},
   Number = {8},
   Pages = {3626-3636},
   Year = {2008},
   Month = {August},
   ISSN = {0094-2405},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/18777923},
   Keywords = {Algorithms • Breast • Breast Neoplasms •
             False Positive Reactions • Female • Humans •
             Mammography • Pattern Recognition, Automated •
             Radiographic Image Interpretation, Computer-Assisted •
             Sensitivity and Specificity • methods* • pathology
             • pathology* • radiography},
   Abstract = {The purpose of this study was to propose and implement a
             computer aided detection (CADe) tool for breast
             tomosynthesis. This task was accomplished in two stages-a
             highly sensitive mass detector followed by a false positive
             (FP) reduction stage. Breast tomosynthesis data from 100
             human subject cases were used, of which 25 subjects had one
             or more mass lesions and the rest were normal. For stage 1,
             filter parameters were optimized via a grid search. The CADe
             identified suspicious locations were reconstructed to yield
             3D CADe volumes of interest. The first stage yielded a
             maximum sensitivity of 93% with 7.7 FPs/breast volume.
             Unlike traditional CADe algorithms in which the second stage
             FP reduction is done via feature extraction and analysis,
             instead information theory principles were used with mutual
             information as a similarity metric. Three schemes were
             proposed, all using leave-one-case-out cross validation
             sampling. The three schemes, A, B, and C, differed in the
             composition of their knowledge base of regions of interest
             (ROIs). Scheme A's knowledge base was comprised of all the
             mass and FP ROIs generated by the first stage of the
             algorithm. Scheme B had a knowledge base that contained
             information from mass ROIs and randomly extracted normal
             ROIs. Scheme C had information from three sources of
             information-masses, FPs, and normal ROIs. Also, performance
             was assessed as a function of the composition of the
             knowledge base in terms of the number of FP or normal ROIs
             needed by the system to reach optimal performance. The
             results indicated that the knowledge base needed no more
             than 20 times as many FPs and 30 times as many normal ROIs
             as masses to attain maximal performance. The best overall
             system performance was 85% sensitivity with 2.4 FPs per
             breast volume for scheme A, 3.6 FPs per breast volume for
             scheme B, and 3 FPs per breast volume for scheme
             C.},
   Language = {eng},
   Doi = {10.1118/1.2953562},
   Key = {fds269438}
}

@article{fds269441,
   Author = {Williams, MB and Raghunathan, P and More, MJ and Seibert, JA and Kwan,
             A and Lo, JY and Samei, E and Ranger, NT and Fajardo, LL and McGruder, A and McGruder, SM and Maidment, ADA and Yaffe, MJ and Bloomquist, A and Mawdsley, GE},
   Title = {Optimization of exposure parameters in full field digital
             mammography.},
   Journal = {Medical physics},
   Volume = {35},
   Number = {6},
   Pages = {2414-2423},
   Year = {2008},
   Month = {June},
   ISSN = {0094-2405},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/18649474},
   Keywords = {Environmental Exposure* • Mammography • Phantoms,
             Imaging • Radiation Dosage* • Radiographic Image
             Enhancement • Societies • methods*},
   Abstract = {Optimization of exposure parameters (target, filter, and
             kVp) in digital mammography necessitates maximization of the
             image signal-to-noise ratio (SNR), while simultaneously
             minimizing patient dose. The goal of this study is to
             compare, for each of the major commercially available full
             field digital mammography (FFDM) systems, the impact of the
             selection of technique factors on image SNR and radiation
             dose for a range of breast thickness and tissue types. This
             phantom study is an update of a previous investigation and
             includes measurements on recent versions of two of the FFDM
             systems discussed in that article, as well as on three FFDM
             systems not available at that time. The five commercial FFDM
             systems tested, the Senographe 2000D from GE Healthcare, the
             Mammomat Novation DR from Siemens, the Selenia from Hologic,
             the Fischer Senoscan, and Fuji's 5000MA used with a Lorad
             M-IV mammography unit, are located at five different
             university test sites. Performance was assessed using all
             available x-ray target and filter combinations and nine
             different phantom types (three compressed thicknesses and
             three tissue composition types). Each phantom type was also
             imaged using the automatic exposure control (AEC) of each
             system to identify the exposure parameters used under
             automated image acquisition. The figure of merit (FOM) used
             to compare technique factors is the ratio of the square of
             the image SNR to the mean glandular dose. The results show
             that, for a given target/filter combination, in general FOM
             is a slowly changing function of kVp, with stronger
             dependence on the choice of target/filter combination. In
             all cases the FOM was a decreasing function of kVp at the
             top of the available range of kVp settings, indicating that
             higher tube voltages would produce no further performance
             improvement. For a given phantom type, the exposure
             parameter set resulting in the highest FOM value was system
             specific, depending on both the set of available
             target/filter combinations, and on the receptor type. In
             most cases, the AECs of the FFDM systems successfully
             identified exposure parameters resulting in FOM values near
             the maximum ones, however, there were several examples where
             AEC performance could be improved.},
   Language = {eng},
   Doi = {10.1118/1.2912177},
   Key = {fds269441}
}

@article{fds269443,
   Author = {Pollard, BJ and Chawla, AS and Delong, DM and Hashimoto, N and Samei,
             E},
   Title = {Object detectability at increased ambient lighting
             conditions.},
   Journal = {Medical physics},
   Volume = {35},
   Number = {6},
   Pages = {2204-2213},
   Year = {2008},
   Month = {June},
   ISSN = {0094-2405},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/18649449},
   Keywords = {Clinical Medicine • Diagnostic Imaging • Light
             • Lighting • Ocular Physiological Phenomena •
             Psychophysics • Time Factors •
             methods*},
   Abstract = {Under typical dark conditions encountered in diagnostic
             reading rooms, a reader's pupils will contract and dilate as
             the visual focus intermittently shifts between the high
             luminance display and the darker background wall, resulting
             in increased visual fatigue and the degradation of
             diagnostic performance. A controlled increase of ambient
             lighting may, however, reduce the severity of these
             pupillary adjustments by minimizing the difference between
             the luminance level to which the eyes adapt while viewing an
             image (L(adp)) and the luminance level of diffusely
             reflected light from the area surrounding the display
             (L(s)). Although ambient lighting in reading rooms has
             conventionally been kept at a minimum to maintain the
             perceived contrast of film images, proper Digital Imaging
             and Communications in Medicine (DICOM) calibration of modern
             medical-grade liquid crystal displays can compensate for
             minor lighting increases with very little loss of image
             contrast. This paper describes two psychophysical studies
             developed to evaluate and refine optimum reading room
             ambient lighting conditions through the use of observational
             tasks intended to simulate real clinical practices. The
             first study utilized the biologic contrast response of the
             human visual system to determine a range of representative
             L(adp) values for typical medical images. Readers identified
             low contrast horizontal objects in circular foregrounds of
             uniform luminance (5, 12, 20, and 30 cd/m2) embedded within
             digitized mammograms. The second study examined the effect
             of increased ambient lighting on the detection of subtle
             objects embedded in circular foregrounds of uniform
             luminance (5, 12, and 35 cd/m2) centered within a constant
             background of 12 cd/m2 luminance. The images were displayed
             under a dark room condition (1 lux) and an increased ambient
             lighting level (50 lux) such that the luminance level of the
             diffusely reflected light from the background wall was
             approximately equal to the image L(adp) value of 12 cd/m2.
             Results from the first study demonstrated that observer true
             positive and false positive detection rates and true
             positive detection times were considerably better while
             viewing foregrounds at 12 and 20 cd/m2 than at the other
             foreground luminance levels. Results from the second study
             revealed that under increased room illuminance, the average
             true positive detection rate improved a statistically
             significant amount from 39.3% to 55.6% at 5 cd/m2 foreground
             luminance. Additionally, the true positive rate increased
             from 46.4% to 56.6% at 35 cd/m2 foreground luminance, and
             decreased slightly from 90.2% to 87.5% at 12 cd/m2
             foreground luminance. False positive rates at all foreground
             luminance levels remained approximately constant with
             increased ambient lighting. Furthermore, under increased
             room illuminance, true positive detection times declined at
             every foreground luminance level, with the most considerable
             decrease (approximately 500 ms) at the 5 cd/m2 foreground
             luminance. The first study suggests that L(adp) of typical
             mammograms lies between 12 and 20 cd/m2, leading to an
             optimum reading room illuminance of approximately 50-80 lux.
             Findings from the second study provide psychophysical
             evidence that ambient lighting may be increased to a level
             within this range, potentially improving radiologist
             comfort, without deleterious effects on diagnostic
             performance.},
   Language = {eng},
   Doi = {10.1118/1.2907566},
   Key = {fds269443}
}

@article{fds269450,
   Author = {Fetterly, KA and Blume, HR and Flynn, MJ and Samei,
             E},
   Title = {Introduction to grayscale calibration and related aspects of
             medical imaging grade liquid crystal displays.},
   Journal = {Journal of Digital Imaging},
   Volume = {21},
   Number = {2},
   Pages = {193-207},
   Year = {2008},
   Month = {June},
   ISSN = {0897-1889},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/17333412},
   Keywords = {Calibration • Data Display* • Diagnostic Imaging
             • Humans • Lighting • Liquid Crystals* •
             Luminescence • Optics and Photonics • Radiographic
             Image Enhancement • instrumentation •
             methods*},
   Abstract = {Consistent presentation of digital radiographic images at
             all locations within a medical center can help ensure a high
             level of patient care. Currently, liquid crystal displays
             (LCDs) are the electronic display technology of choice for
             viewing medical images. As the inherent luminance (and
             thereby perceived contrast) properties of different LCDs can
             vary substantially, calibration of the luminance response of
             these displays is required to ensure that observer
             perception of an image is consistent on all displays. The
             digital imaging and communication in medicine (DICOM)
             grayscale standard display function (GSDF) defines the
             luminance response of a display such that an observer's
             perception of image contrast is consistent throughout the
             pixel value range of a displayed image. The main purpose of
             this work is to review the theoretical and practical aspects
             of calibration of LCDs to the GSDF. Included herein is a
             review of LCD technology, principles of calibration, and
             other practical aspects related to calibration and observer
             perception of images presented on LCDs. Both grayscale and
             color displays are considered, and the influence of ambient
             light on calibration and perception is discussed.},
   Language = {eng},
   Doi = {10.1007/s10278-007-9022-y},
   Key = {fds269450}
}

@article{fds269439,
   Author = {Samei, E and Ranger, NT and Delong, DM},
   Title = {A comparative contrast-detail study of five medical
             displays.},
   Journal = {Medical physics},
   Volume = {35},
   Number = {4},
   Pages = {1358-1364},
   Year = {2008},
   Month = {April},
   ISSN = {0094-2405},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/18491530},
   Keywords = {Computer Terminals* • Contrast Sensitivity* • Data
             Display* • Humans • Phantoms, Imaging •
             Reproducibility of Results • Sensitivity and
             Specificity • Tomography, X-Ray Computed •
             User-Computer Interface* • instrumentation* •
             methods},
   Abstract = {The objective of this study was to compare the
             contrast-detail performance of five different commercial
             liquid crystal displays (LCDs) to other LCD and cathode-ray
             tube (CRT) displays for medical applications. A
             contrast-detail phantom, supplemented with 5 in. of acrylic,
             was imaged on a commercial digital radiographic system using
             techniques comparable to chest radiography. The phantom
             design enabled observer evaluation by a four-alternative
             forced choice paradigm. The acquired images were
             independently scored by five observers on five medical
             display devices: a 5 megapixel monochrome LCD, a 3 megapixel
             monochrome LCD, a 9 megapixel color LCD, a 5 megapixel
             monochrome CRT, and a mammographic-grade monochrome CRT. The
             data were analyzed using the method suggested by the
             manufacturer based on a nearest neighbor correction
             technique. They were further analyzed using a logistic
             regression response model with a natural threshold using an
             overall chi-square test for display type followed by
             pairwise comparisons for individual display performance. The
             differences between the display devices were small. The
             standard analysis of the results based on the
             manufacturer-recommended method did not yield any
             statistically discernible trend among displays. The logistic
             regression analysis, however, indicated that the 5 megapixel
             monochrome LCD was statistically significantly (p <0.0001)
             superior to the others, followed by the 3 megapixel
             monochrome LCD (p<0.0001). The three other displays
             exhibited lower but generally similar performance
             characteristics. The findings suggest that 5 and 3 megapixel
             monochrome LCDs provide comparable but subtly superior
             contrast detectability than other tested displays, with the
             former performing slightly better in the detection of subtle
             and fine details.},
   Language = {eng},
   Doi = {10.1118/1.2868780},
   Key = {fds269439}
}

@article{fds269442,
   Author = {Chawla, AS and Samei, E and Saunders, RS and Lo, JY and Baker,
             JA},
   Title = {A mathematical model platform for optimizing a
             multiprojection breast imaging system.},
   Journal = {Medical physics},
   Volume = {35},
   Number = {4},
   Pages = {1337-1345},
   Year = {2008},
   Month = {April},
   ISSN = {0094-2405},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/18491528},
   Keywords = {Algorithms* • Breast Neoplasms • Computer
             Simulation • Female • Humans • Imaging,
             Three-Dimensional • Mammography • Models,
             Biological • Radiographic Image Enhancement •
             Radiographic Image Interpretation, Computer-Assisted •
             Reproducibility of Results • Sensitivity and
             Specificity • Software • Subtraction Technique
             • methods* • radiography*},
   Abstract = {Multiprojection imaging is a technique in which a plurality
             of digital radiographic images of the same patient are
             acquired within a short interval of time from slightly
             different angles. Information from each image is combined to
             determine the final diagnosis. Projection data are either
             reconstructed into slices as in the case of tomosynthesis or
             analyzed directly as in the case of multiprojection
             correlation imaging technique, thereby avoiding
             reconstruction artifacts. In this study, the authors
             investigated the optimum geometry of acquisitions of a
             multiprojection breast correlation imaging system in terms
             of the number of projections and their total angular span
             that yield maximum performance in a task that models
             clinical decision. Twenty-five angular projections of each
             breast from 82 human subjects in our breast tomosynthesis
             database were each supplemented with a simulated 3 mm mass.
             An approach based on Laguerre-Gauss channelized Hotelling
             observer was developed to assess the detectability of the
             mass in terms of receiver operating characteristic (ROC)
             curves. Two methodologies were developed to integrate
             results from individual projections into one combined ROC
             curve as the overall figure of merit. To optimize the
             acquisition geometry, different components of acquisitions
             were changed to investigate which one of the many possible
             configurations maximized the area under the combined ROC
             curve. Optimization was investigated under two acquisition
             dose conditions corresponding to a fixed total dose
             delivered to the patient and a variable dose condition,
             based on the number of projections used. In either case, the
             detectability was dependent on the number of projections
             used, the total angular span of those projections, and the
             acquisition dose level. In the first case, the detectability
             approximately followed a bell curve as a function of the
             number of projections with the maximum between 8 and 16
             projections spanning angular arcs of about 23 degrees-45
             degrees, respectively. In the second case, the detectability
             increased with the number of projections approaching an
             asymptote at 11-17 projections for an angular span of about
             45 degrees. These results indicate the inherent information
             content of the multi-projection image data reflecting the
             relative role of quantum and anatomical noise in
             multiprojection breast imaging. The optimization scheme
             presented here may be applied to any multiprojection imaging
             modalities and may be extended by including reconstruction
             in the case of digital breast tomosynthesis and breast
             computed tomography.},
   Language = {eng},
   Doi = {10.1118/1.2885367},
   Key = {fds269442}
}

@article{fds269440,
   Author = {Schindera, ST and Nelson, RC and Mukundan, S and Paulson, EK and Jaffe,
             TA and Miller, CM and DeLong, DM and Kawaji, K and Yoshizumi, TT and Samei,
             E},
   Title = {Hypervascular liver tumors: low tube voltage, high tube
             current multi-detector row CT for enhanced
             detection--phantom study.},
   Journal = {Radiology},
   Volume = {246},
   Number = {1},
   Pages = {125-132},
   Year = {2008},
   Month = {January},
   ISSN = {1527-1315},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/18096533},
   Keywords = {Electricity • Liver Neoplasms • Models, Anatomic*
             • Prospective Studies • Radiation Dosage •
             Tomography, X-Ray Computed • blood supply* •
             methods* • radiography*},
   Abstract = {PURPOSE: To prospectively evaluate, for the depiction of
             simulated hypervascular liver lesions in a phantom, the
             effect of a low tube voltage, high tube current computed
             tomographic (CT) technique on image noise, contrast-to-noise
             ratio (CNR), lesion conspicuity, and radiation dose.
             MATERIALS AND METHODS: A custom liver phantom containing 16
             cylindric cavities (four cavities each of 3, 5, 8, and 15 mm
             in diameter) filled with various iodinated solutions to
             simulate hypervascular liver lesions was scanned with a
             64-section multi-detector row CT scanner at 140, 120, 100,
             and 80 kVp, with corresponding tube current-time product
             settings at 225, 275, 420, and 675 mAs, respectively. The
             CNRs for six simulated lesions filled with different
             iodinated solutions were calculated. A figure of merit (FOM)
             for each lesion was computed as the ratio of CNR2 to
             effective dose (ED). Three radiologists independently graded
             the conspicuity of 16 simulated lesions. An anthropomorphic
             phantom was scanned to evaluate the ED. Statistical analysis
             included one-way analysis of variance. RESULTS: Image noise
             increased by 45% with the 80-kVp protocol compared with the
             140-kVp protocol (P < .001). However, the lowest ED and the
             highest CNR were achieved with the 80-kVp protocol. The FOM
             results indicated that at a constant ED, a reduction of tube
             voltage from 140 to 120, 100, and 80 kVp increased the CNR
             by factors of at least 1.6, 2.4, and 3.6, respectively (P <
             .001). At a constant CNR, corresponding reductions in ED
             were by a factor of 2.5, 5.5, and 12.7, respectively (P <
             .001). The highest lesion conspicuity was achieved with the
             80-kVp protocol. CONCLUSION: The CNR of simulated
             hypervascular liver lesions can be substantially increased
             and the radiation dose reduced by using an 80-kVp, high tube
             current CT technique.},
   Language = {eng},
   Doi = {10.1148/radiol.2461070307},
   Key = {fds269440}
}

@article{fds269342,
   Author = {Shafer, CM and Samei, E and Saunders, RS and Zerhouni, M and Lo,
             JY},
   Title = {Toward quantification of breast tomosynthesis
             imaging},
   Journal = {Proceedings of SPIE},
   Volume = {6913},
   Year = {2008},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.772753},
   Abstract = {Due to the high prevalence of breast cancer among women,
             much is being done to detect breast cancer earlier and more
             accurately. In current clinical practice, the most
             widely-used mode of breast imaging is mammography. Its main
             advantages are high sensitivity and low patient dose,
             although it is still merely a two-dimensional projection of
             a three-dimensional object. In digital breast tomosynthesis,
             a three-dimensional image of the breast can be
             reconstructed, but x-ray projection images of the breast are
             taken over a limited angular span. However, the breast
             tomosynthesis device itself is more similar to a digital
             mammography system and thus is a feasible replacement for
             mammography. Because of the angular undersampling in breast
             tomosynthesis, the reconstructed images are not considered
             quantitative, so a worthwhile question to answer would be
             whether the voxel values (VVs) in breast tomosynthesis
             images can be made to indicate tissue type as Hounsfield
             units do in CT. through some image processing scheme. To
             investigate this, simple phantoms were imaged consisting of
             layers of uniform, tissue-equivalent plastic for the
             background sandwiching a layer of interest containing
             multiple, small cuboids of tissue-equivalent plastic. After
             analyzing the reconstructed tomosynthesis images, it was
             found that the VV in each lesion increases linearly with
             tissue glandularity. However, for the two different x-ray
             tube energies and for the two different beam exposure levels
             tested, the trend-lines all have different slopes and
             y-intercepts. Thus, breast tomosynthesis has a definite
             potential to be quantitative, and it would be worthwhile to
             study other possible dependent parameters (phantom
             thickness, overall density, etc.) as well as alternative
             reconstruction algorithms.},
   Doi = {10.1117/12.772753},
   Key = {fds269342}
}

@article{fds269343,
   Author = {Singh, S and Tourassi, GD and Chawla, AS and Saunders, RS and Samei, E and Lo, JY},
   Title = {Computer aided detection of breast masses in tomosynthesis
             reconstructed volumes using information-theoretic similarity
             measures},
   Journal = {Proceedings of SPIE},
   Volume = {6915},
   Year = {2008},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.772978},
   Abstract = {The purpose of this project is to study two Computer Aided
             Detection (CADe) systems for breast masses for digital
             tomosynthesis using reconstructed slices. This study used
             eighty human subject cases collected as part of on-going
             clinical trials at Duke University. Raw projections images
             were used to identify suspicious regions in the algorithm's
             high sensitivity, low specificity stage using a Difference
             of Gaussian filter. The filtered images were thresholded to
             yield initial CADe hits that were then shifted and added to
             yield a 3D distribution of suspicious regions. The initial
             system performance was 95% sensitivity at 10 false positives
             per breast volume. Two CADe systems were developed. In
             system A, the central slice located at the centroid depth
             was used to extract a 256× 256 Regions of Interest (ROI)
             database centered at the lesion coordinates. For system B, 5
             slices centered at the lesion coordinates were summed before
             the extraction of 256× 256 ROIs. To avoid issues associated
             with feature extraction, selection, and merging, information
             theory principles were used to reduce false positives for
             both the systems resulting in a classifier performance of
             0.81 and 0.865 Area Under Curve (AUC) with
             leave-one-case-out sampling. This resulted in an overall
             system performance of 87% sensitivity with 6.1 FPs/volume
             and 85% sensitivity with 3.8 FPs/ volume for systems A and B
             respectively. This system therefore has the potential to
             detect breast masses in tomosynthesis data
             sets.},
   Doi = {10.1117/12.772978},
   Key = {fds269343}
}

@article{fds269344,
   Author = {Chawla, AS and Samei, E and Saunders, RS and Lo, JY and Singh,
             S},
   Title = {Optimized acquisition scheme for multi-projection
             correlation imaging of breast cancer},
   Journal = {Proceedings of SPIE},
   Volume = {6915},
   Year = {2008},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.773174},
   Abstract = {We are reporting the optimized acquisition scheme of
             multi-projection breast Correlation Imaging (CI) technique,
             which was pioneered in our lab at Duke University. CI is
             similar to tomosynthesis in its image acquisition scheme.
             However, instead of analyzing the reconstructed images, the
             projection images are directly analyzed for pathology.
             Earlier, we presented an optimized data acquisition scheme
             for CI using mathematical observer model. In this article,
             we are presenting a Computer Aided Detection (CADe)-based
             optimization methodology. Towards that end, images from 106
             subjects recruited for an ongoing clinical trial for
             tomosynthesis were employed. For each patient, 25 angular
             projections of each breast were acquired. Projection images
             were supplemented with a simulated 3 mm 3D lesion. Each
             projection was first processed by a traditional CADe
             algorithm at high sensitivity, followed by a reduction of
             false positives by combining geometrical correlation
             information available from the multiple images. Performance
             of the CI system was determined in terms of free-response
             receiver operating characteristics (FROC) curves and the
             area under ROC curves. For optimization, the components of
             acquisition such as the number of projections, and their
             angular span were systematically changed to investigate
             which one of the many possible combinations maximized the
             sensitivity and specificity. Results indicated that the
             performance of the CI system may be maximized with 7-11
             projections spanning an angular arc of 44.8°, confirming
             our earlier findings using observer models. These results
             indicate that an optimized CI system may potentially be an
             important diagnostic tool for improved breast cancer
             detection.},
   Doi = {10.1117/12.773174},
   Key = {fds269344}
}

@article{fds269345,
   Author = {Shafer, CM and Samei, E and Mertelmeier, T and Saunders, RS and Zerhouni, M and Lo, JY},
   Title = {Assessment of low energies and slice depth in the
             quantification of breast tomosynthesis},
   Journal = {Lecture notes in computer science},
   Volume = {5116 LNCS},
   Pages = {530-536},
   Year = {2008},
   ISSN = {0302-9743},
   url = {http://dx.doi.org/10.1007/978-3-540-70538-3_74},
   Abstract = {This study attempts to assess the quantitative potential of
             breast tomosynthesis imaging. Tomosynthesis might be a
             feasible replacement for digital mammography, so it is
             worthwhile to consider whether it can be quantitative like
             computed tomography (CT), where the image pixel values are
             expressed in Hounsfield units. For this investigation,
             plastic tissue-equivalent breast phantoms with 10 lesions of
             varying density in the center along with a small density
             calibration phantom of 5 density-varying lesions were imaged
             under several different conditions. The measured voxel value
             for each lesion from a reconstructed slice was linearly
             rescaled based on the calibration phantom and then plotted
             against the known glandular fraction of each lesion. It was
             found that the two different energies and the three
             different lesion depths all produced linear voxel values
             versus glandularity relationships. Therefore, tomosynthesis
             has quantitative potential. However, in order to convert
             each 3D image's voxel values to values that can be
             interpreted as a certain glandular fraction, one must
             consider the x-ray tube energy, slice depth, and many other
             factors of the imaging system and the breast. © 2008
             Springer-Verlag Berlin Heidelberg.},
   Doi = {10.1007/978-3-540-70538-3_74},
   Key = {fds269345}
}

@article{fds269346,
   Author = {Tourassi, GD and Sharma, AC and Singh, S and Saunders, RS and Lo, JY and Samei, E and Harrawood, BP},
   Title = {Knowledge transfer across breast cancer screening
             modalities: A pilot study using an information-theoretic
             CADe system for mass detection},
   Journal = {Lecture notes in computer science},
   Volume = {5116 LNCS},
   Pages = {292-298},
   Year = {2008},
   ISSN = {0302-9743},
   url = {http://dx.doi.org/10.1007/978-3-540-70538-3_41},
   Abstract = {We have performed a series of experiments to assess whether
             a featureless, knowledge-based CADe system that relies on
             information theoretic principles is capable of transferring
             knowledge across cases acquired with different imaging
             modalities. Typical feature-based CADe systems are developed
             and carefully optimized for a specific imaging modality and
             platform, namely for screen-film mammograms (SFMs) digitized
             with a specific digitizer, or for full-field digital
             mammograms (FFDMs), or for the newly introduced digital
             breast tomosynthesis (DBT) modality. Multiplatform
             application of such CADe systems is often limited due to
             image processing steps that are tailored to the imaging
             modality and acquisition protocol. It is desirable however
             to develop CADe systems with the ability to adapt to a
             dynamically changing environment (i.e., imaging modality)
             and provide an accurate decision while capitalizing on
             knowledge acquired at different, yet related environments.
             Working towards this goal, we present a pilot study using a
             knowledge-based CADe system for mass detection that uses
             information theory to assess the similarity between a query
             and a knowledge case. We evaluate the system's ability to
             transfer knowledge across three imaging modalities (SFMs
             digitized with two different digitizers, FFDMs, and DBTs)
             when performing the detection task. Overall our study showed
             that although blind translation of the system in a new
             modality for which no prior knowledge exists results in
             reduced performance, the system is still able to operate at
             a very decent level. When the system operated with a
             knowledge database of mixed cases, its performance was
             robust and comparable to what observed independently. ©
             2008 Springer-Verlag Berlin Heidelberg.},
   Doi = {10.1007/978-3-540-70538-3_41},
   Key = {fds269346}
}

@article{fds269347,
   Author = {Chawla, AS and Samei, E and Lo, JY and Mertelmeier,
             T},
   Title = {Multi-projection correlation imaging as a new diagnostic
             tool for improved breast cancer detection},
   Journal = {Lecture notes in computer science},
   Volume = {5116 LNCS},
   Pages = {635-642},
   Year = {2008},
   ISSN = {0302-9743},
   url = {http://dx.doi.org/10.1007/978-3-540-70538-3_88},
   Abstract = {Multi-projection imaging technique offers an advantage over
             single projection imaging techniques in rendering pathology
             that may be surrounded by a complex cloud of anatomical
             structures. The process of harnessing the geometrical and
             statistical dependences between the multiple images
             available in a multi-projection system to determine the
             final diagnosis is termed Correlation Imaging (CI). In this
             study, we are investigating the potential improvement in
             breast cancer detection via CI. As a key step towards that,
             the acquisition scheme of CI was first optimized to maximize
             its diagnostic performance. Toward that end, first a
             clinically-realistic task was designed and each component of
             acquisition, namely, the acquisition dose level, the number
             of projections, and their angular span was systematically
             changed to determine a specific combination that yielded
             maximum performance in that task. Finally, the performance
             of the optimized system was compared with that of standard
             planar mammography. The results indicated that the
             performance of CI may potentially be optimized between 15-17
             projections spanning an angular arc of 45 o . This optimum
             performance further improved with increasing dose levels;
             however, at dose level comparable to mammography, CI
             provided a factor of 1.1 improvement over mammography. The
             framework developed in this study to evaluate
             multi-projections system may be applied to any other
             multi-projection imaging modality, and by including
             reconstruction, may be extended to digital breast
             tomosynthesis and breast computed tomography. © 2008
             Springer-Verlag Berlin Heidelberg.},
   Doi = {10.1007/978-3-540-70538-3_88},
   Key = {fds269347}
}

@article{fds269271,
   Author = {Shafer, CM and Samei, E and Saunders, RS and Zerhouni, M and Lo,
             JY},
   Title = {Toward quantification of breast tomosynthesis
             imaging},
   Journal = {Proceedings of SPIE - The International Society for Optical
             Engineering},
   Volume = {6913},
   Year = {2008},
   ISSN = {0277-786X},
   url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000256660300156&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
   Doi = {10.1117/12.772753},
   Key = {fds269271}
}

@article{fds269320,
   Author = {Pollard, BJ and Chawla, AS and Hashimoto, N and Samei,
             E},
   Title = {The effect of increased ambient lighting on detection
             accuracy in uniform and anatomical backgrounds},
   Journal = {Proceedings of SPIE},
   Volume = {6919},
   Year = {2008},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.772932},
   Abstract = {Under typical dark conditions found in reading rooms, a
             reader's pupils will contract and dilate as the visual focus
             intermittently shifts between the high luminance monitor and
             the darker background wall, resulting in increased visual
             fatigue and the degradation of diagnostic performance. A
             controlled increase of ambient lighting may, however,
             minimize these visual adjustments and potentially improve
             reader comfort and accuracy. This paper details results from
             two psychophysical studies designed to determine the effect
             of a controlled ambient lighting increase on observer
             detection of subtle objects and lesions viewed on a
             DICOM-calibrated medical-grade LCD. The first study examined
             the effect of increased ambient lighting on detection of
             subtle objects embedded within a uniform background, while
             the second study examined observer detection performance of
             subtle cancerous lesions in mammograms and chest
             radiographs. In both studies, observers were presented with
             images under a dark room condition (1 lux) and an increased
             room illuminance level (50 lux) for which the luminance
             level of the diffusely reflected light from the background
             wall was approximately equal to that of the displayed image.
             The display was calibrated to an effective luminance ratio
             of 409 for both lighting conditions. Observer detection
             performance under each room illuminance condition was then
             compared. Identification of subtle objects embedded within
             the uniform background improved from 59% to 67%, while
             detection time decreased slightly with additional
             illuminance. An ROC analysis of the anatomical image results
             revealed that observer AUC values remained constant while
             detection time decreased under increased illuminance. The
             results provide evidence that an ambient lighting increase
             may be possible without compromising diagnostic
             efficacy.},
   Doi = {10.1117/12.772932},
   Key = {fds269320}
}

@article{fds269321,
   Author = {Huda, W and Ogden, KM and Samei, E and Scalzetti, EM and Lavallee, RL and Roskopf, ML},
   Title = {Inter-reader variability in Alternate Forced Choice
             studies},
   Journal = {Proceedings of SPIE},
   Volume = {6917},
   Year = {2008},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.770618},
   Abstract = {In this study, we investigated differences in detection
             performance for twelve observers who each generated a CT
             contrast detail curve. An anthropomorphic newborn phantom's
             abdomen was imaged using a GE Light Speed CT scanner
             (4-slice). Alternate Forced Choice (AFC) experiments were
             performed with lesions sizes ranging from 2.5 to 12.5 mm to
             determine the intensity needed to achieve 92% correct
             (I92%). Following training, twelve readers consisting of (2
             technologists, 4 college students, 4 medical students, and 2
             radiology residents) generated a single contrast detail
             curve. Eight readers produced approximately linear contrast
             detail curves while the remaining four readers required a
             second order polynomial fit because of reduced performance
             when detecting the largest (i.e., 12.5 mm) lesion. For the
             three smallest lesions, the coefficient of variation between
             the twelve readers was ∼12%, which increases with
             increasing lesion size to ∼23% for 12.5 mm lesion size.
             The ratio of the maximum I92%.to minimum I92% values was
             ∼1.6 for the smallest lesions, which increased to a factor
             of ∼2.1 for the 12.5 mm lesion. Our results show that
             minimizing inter-reader variability in our AFC experiments
             could be achieved by eliminating the largest lesion that
             cause detection problems in one third of observers. The
             combined experimental data showed that the slope of the
             contrast detail curve was -0.42, lower than the value of
             -1.0 predicted by the Rose model, suggesting that the noise
             texture in CT associated with both quantum mottle and
             anatomic structure is an important factor affecting
             detection of these lesions.},
   Doi = {10.1117/12.770618},
   Key = {fds269321}
}

@article{fds269322,
   Author = {Castella, C and Kinkel, K and Eckstein, MP and Abbey, CK and Verdun, FR and Saunders, RS and Samei, E and Bochud, FO},
   Title = {Mass detection on mammograms: Signal variations and
             performance changes for human and model observers},
   Journal = {Proceedings of SPIE},
   Volume = {6917},
   Year = {2008},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.769415},
   Abstract = {We studied the influence of signal variability on human and
             model observer performances for a detection task with
             mammographic backgrounds and computer generated clustered
             lumpy backgrounds (CLB). We used synthetic yet realistic
             masses and backgrounds that have been validated by
             radiologists during previous studies, ensuring conditions
             close to the clinical situation. Four trained non-physician
             observers participated in two-alternative forced-choice
             (2-AFC) experiments. They were asked to detect synthetic
             masses superimposed on real mammographic backgrounds or CLB.
             Separate experiments were conducted with sets of benign and
             malignant masses. Results under the signal-known-exactly
             (SKE) paradigm were compared with signal-known-statistically
             (SKS) experiments. In the latter case, the signal was chosen
             randomly for each of the 1,400 2-AFC trials (image pairs)
             among a set of 50 masses with similar dimensions, and the
             observers did not know which signal was present. Human
             observers' results were then compared with model observers
             (channelized Hotelling with Difference-of-Gaussian and Gabor
             channels) in the same experimental conditions. Results show
             that the performance of the human observers does not differ
             significantly when benign masses are superimposed on real
             images or on CLB with locally matched gray level mean and
             standard deviation. For both benign and malignant masses,
             the performance does not differ significantly between SKE
             and SKS experiments, when the signals' dimensions do not
             vary throughout the experiment. However, there is a
             performance drop when the SKS signals' dimensions vary from
             5.5 to 9.5 mm in the same experiment. Noise level in the
             model observers can be adjusted to reproduce human
             observers' proportion of correct answers in the 2-AFC task
             within 5% accuracy for most conditions.},
   Doi = {10.1117/12.769415},
   Key = {fds269322}
}

@article{fds269323,
   Author = {Huda, W and Ogden, KM and Samei, E and Scalzetti, EM and Lavallee, RL and Roskopf, ML and Groat, GE},
   Title = {Reconstruction filters and contrast detail curves in
             CT},
   Journal = {Proceedings of SPIE},
   Volume = {6917},
   Year = {2008},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.770530},
   Abstract = {In this study, we investigated the effect of CT
             reconstruction filters in abdominal CT images of a male
             anthropomorphic phantom. A GE Light Speed CT 4-slice scanner
             was used to scan the abdomen of an adult Rando phantom.
             Cross sectional images of the phantom were reconstructed
             using four reconstruction filters: (1) soft tissue with the
             lowest noise; (2) detail (relative noise 1.7); (3) bone
             (relative noise 4.5); and (4) edge (relative noise 7.7). A
             two Alternate Forced Choice (AFC) experimental paradigm was
             used to estimate the intensity needed to achieve 92% correct
             (i.e., I92%) Four observers measured detection performance
             for five lesions with size ranging from 2.5 to 12.5 mm for
             each of these four reconstruction filters. Contrast detail
             curves obtained in images of an anthropomorphic phantom were
             not straight lines, but best fitted to a second order
             polynomial. Results from four readers show similar trends
             with modest inter-observer differences with the measured
             coefficient of variation of the absolute performance levels
             of ∼22%. All reconstruction filters had similar shaped
             contrast detail curves except for smallest details where the
             frequency response of filters differed most significantly.
             Increasing the noise level always reduced detection
             performance, and a doubling of image noise resulted in an
             average drop in detection performance of ∼20%. The key
             findings of this study are that (a) the Rose model can
             provide reasonable predictions as to how changes in lesion
             size affect observer detection; (b) the shape of CT contrast
             detail curves is affected only very slightly with
             reconstruction filter; (c) changes in reconstruction filter
             noise can predict qualitative changes in observer detection
             performance, but are poor direct predictors of the
             quantitative changes of imaging performance.},
   Doi = {10.1117/12.770530},
   Key = {fds269323}
}

@article{fds269324,
   Author = {Pollard, BJ and Chawla, AS and Hashimoto, N and Samei,
             E},
   Title = {Breast mass detection under increased ambient
             lighting},
   Journal = {Lecture notes in computer science},
   Volume = {5116 LNCS},
   Pages = {243-248},
   Year = {2008},
   ISSN = {0302-9743},
   url = {http://dx.doi.org/10.1007/978-3-540-70538-3_34},
   Abstract = {Under typical dark conditions found in mammography reading
             rooms, a reader's pupils will contract and dilate as the
             visual focus moves between the high luminance display and
             the darker background wall, potentially resulting in visual
             fatigue and degraded diagnostic performance. A controlled
             increase of ambient lighting can, however, minimize this
             luminance discrepancy, potentially reducing pupillary action
             while improving reader comfort and detection ability. A
             psychophysical study was conducted to determine the effect
             of a controlled ambient lighting increase on observer
             detection of subtle masses within mammograms viewed on a
             DICOM-calibrated medical-grade LCD. Four mammographers read
             86 mammograms (43 normal and 43 with cancerous masses) under
             a dark room condition (1 lux) and an elevated room
             illuminance level (50 lux). Results show generally constant
             or decreased average selection times and decreased average
             observer performance under elevated illuminance.
             Differences, however, were not statistically significant,
             and of the same magnitude as interobserver variability. ©
             2008 Springer-Verlag Berlin Heidelberg.},
   Doi = {10.1007/978-3-540-70538-3_34},
   Key = {fds269324}
}

@article{fds269353,
   Author = {Xiang, L and Samei, E and DeLong, DM and Jones, RP and Colsher, JG and Frush, DP},
   Title = {Towards assessing the diagnostic influence of dose reduction
             in pediatric CT: A study based on simulated lung
             nodules},
   Journal = {Proceedings of SPIE},
   Volume = {6913},
   Year = {2008},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.772089},
   Abstract = {The purpose of this study is to evaluate the effect of
             reduced tube current, as a surrogate for radiation dose, on
             lung nodule detection in pediatric chest multi-detector CT
             (MDCT). Normal chest MDCT images of 13 patients aged 1 to 7
             years old were used as templates for this study. The
             original tube currents were between 70 mA and 180 mA. Using
             proprietary noise addition software, noise was added to the
             images to create 13 cases at the lowest common mA (i.e. 70
             mA), 13 cases at 35 mA (50% reduction), and 13 cases at 17.5
             mA (75% reduction). Three copies of each case were made for
             a total of 117 series for simulated nodule insertion. A
             technique for three-dimensional simulation of small lung
             nodules was developed, validated through an observer study,
             and used to add nodules to the series. Care was taken to
             ensure that each of three lung zones (upper, middle, lower)
             contained 0 or 1 nodule. The series were randomized and the
             presence of a nodule in each lung zone was rated
             independently and blindly by three pediatric radiologists on
             a continuous scale between 0 (definitely absent) and 100
             (definitely present). Receiver operating characteristic
             analysis of the data showed no general significant
             difference in diagnostic accuracy between the reduced mA
             values and 70 mA, suggesting a potential for dose reduction
             with preserved diagnostic quality. To our knowledge, this
             study is the first controlled, systematic, and task-specific
             assessment of the influence of dose reduction in pediatric
             chest CT.},
   Doi = {10.1117/12.772089},
   Key = {fds269353}
}

@article{fds269370,
   Author = {Saunders, R and Samei, E and Badea, C and Yuan, H and Ghaghada, K and Qi,
             Y and Hedlund, LW and Mukundan, S},
   Title = {Optimization of dual energy contrast enhanced breast
             tomosynthesis for improved mammographic lesion detection and
             diagnosis},
   Journal = {Proceedings of SPIE},
   Volume = {6913},
   Year = {2008},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.772042},
   Abstract = {Dual-energy contrast-enhanced breast tomosynthesis has been
             proposed as a technique to improve the detection of
             early-stage cancer in young, high-risk women. This study
             focused on optimizing this technique using computer
             simulations. The computer simulation used analytical
             calculations to optimize the signal difference to noise
             ratio (SdNR) of resulting images from such a technique at
             constant dose. The optimization included the optimal
             radiographic technique, optimal distribution of dose between
             the two single-energy projection images, and the optimal
             weighting factor for the dual energy subtraction.
             Importantly, the SdNR included both anatomical and quantum
             noise sources, as dual energy imaging reduces anatomical
             noise at the expense of increases in quantum noise. Assuming
             a tungsten anode, the maximum SdNR at constant dose was
             achieved for a high energy beam at 49 kVp with 92.5 μm
             copper filtration and a low energy beam at 49 kVp with 95
             μm tin filtration. These analytical calculations were
             followed by Monte Carlo simulations that included the
             effects of scattered radiation and detector properties.
             Finally, the feasibility of this technique was tested in a
             small animal imaging experiment using a novel iodinated
             liposomal contrast agent. The results illustrated the
             utility of dual energy imaging and determined the optimal
             acquisition parameters for this technique. This work was
             supported in part by grants from the Komen Foundation
             (PDF55806), the Cancer Research and Prevention Foundation,
             and the NIH (NCI R21 CA124584-01). CIVM is a NCRR/NCI
             National Resource under P41-05959/U24-CA092656.},
   Doi = {10.1117/12.772042},
   Key = {fds269370}
}

@article{fds269371,
   Author = {Badea, CT and Samei, E and Ghaghada, K and Saunders, R and Yuan, H and Qi,
             Y and Hedlund, LW and Mukundan, S},
   Title = {Utility of a prototype liposomal contrast agent for x-ray
             imaging of breast cancer: A proof of concept using micro-CT
             in small animals},
   Journal = {Proceedings of SPIE},
   Volume = {6913},
   Year = {2008},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.772307},
   Abstract = {Imaging tumor angiogenesis in small animals is extremely
             challenging due to the size of the tumor vessels.
             Consequently, both dedicated small animal imaging systems
             and specialized intravascular contrast agents are required.
             The goal of this study was to investigate the use of a
             liposomal contrast agent for high-resolution micro-CT
             imaging of breast tumors in small animals. A liposomal blood
             pool agent encapsulating iodine with a concentration of 65.5
             mg/ml was used with a Duke Center for In Vivo Microscopy
             (CIVM) prototype micro-computed tomography (micro-CT) system
             to image the R3230AC mammary carcinoma implanted in rats.
             The animals were injected with equivalent volume doses (0.02
             ml/kg) of contrast agent. Micro-CT with the liposomal blood
             pool contrast agent ensured a signal difference between the
             blood and the muscle higher than 450 HU allowing the
             visualization of the tumors 3D vascular architecture in
             exquisite detail at 100-micron resolution. The micro-CT data
             correlated well with the histological examination of tumor
             tissue. We also studied the ability to detect vascular
             enhancement with limited angle based reconstruction, i.e.
             tomosynthesis. Tumor volumes and their regional vascular
             percentage were estimated. This imaging approach could be
             used to better understand tumor angiogenesis and be the
             basis for evaluating anti-angiogenic therapies.},
   Doi = {10.1117/12.772307},
   Key = {fds269371}
}

@article{fds269437,
   Author = {Saunders, RS and Baker, JA and Delong, DM and Johnson, JP and Samei,
             E},
   Title = {Does image quality matter? Impact of resolution and noise on
             mammographic task performance.},
   Journal = {Medical physics},
   Volume = {34},
   Number = {10},
   Pages = {3971-3981},
   Year = {2007},
   Month = {October},
   ISSN = {0094-2405},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/17985642},
   Keywords = {Artifacts • Data Display • Humans • Image
             Processing, Computer-Assisted • Mammography •
             Observer Variation • Radiographic Image Enhancement
             • Radiographic Magnification • Radiology •
             Reproducibility of Results • Subtraction Technique
             • methods* • standards*},
   Abstract = {The purpose of this study was to examine the effects of
             different resolution and noise levels on task performance in
             digital mammography. This study created an image set with
             images at three different resolution levels, corresponding
             to three digital display devices, and three different noise
             levels, with noise magnitudes similar to full clinical dose,
             half clinical dose, and quarter clinical dose. The images
             were read by five experienced breast imaging radiologists.
             The data were then analyzed to compute two accuracy
             statistics (overall classification accuracy and lesion
             detection accuracy) and performance at four diagnostic tasks
             (detection of microcalcifications, benign masses, malignant
             masses, and discrimination of benign and malignant masses).
             Human observer results showed decreasing display resolution
             had little effect on overall classification accuracy and
             individual diagnostic task performance, but increasing noise
             caused overall classification accuracy to decrease by a
             statistically significant 21% as the breast dose went to one
             quarter of its normal clinical value. The noise effects were
             most prominent for the tasks of microcalcification detection
             and mass discrimination. When the noise changed from full
             clinical dose to quarter clinical dose, the
             microcalcification detection performance fell from 89% to
             67% and the mass discrimination performance decreased from
             93% to 79%, while malignant mass detection performance
             remained relatively constant with values of 88% and 84%,
             respectively. As a secondary aim, the image set was also
             analyzed by two observer models to examine whether their
             performance was similar to humans. Observer models differed
             from human observers and each other in their sensitivity to
             resolution degradation and noise. The primary conclusions of
             this study suggest that quantum noise appears to be the
             dominant image quality factor in digital mammography,
             affecting radiologist performance much more profoundly than
             display resolution.},
   Language = {eng},
   Doi = {10.1118/1.2776253},
   Key = {fds269437}
}

@article{fds269445,
   Author = {Chawla, AS and Samei, E and Saunders, R and Abbey, C and Delong,
             D},
   Title = {Effect of dose reduction on the detection of mammographic
             lesions: a mathematical observer model analysis.},
   Journal = {Medical physics},
   Volume = {34},
   Number = {8},
   Pages = {3385-3398},
   Year = {2007},
   Month = {August},
   ISSN = {0094-2405},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/17879801},
   Keywords = {Algorithms • Area Under Curve • Computer
             Simulation • Humans • Image Processing,
             Computer-Assisted • Mammography • Models,
             Theoretical • Observer Variation • ROC Curve
             • Radiographic Image Interpretation, Computer-Assisted
             • Radiometry • Reproducibility of Results •
             Sensitivity and Specificity • methods*},
   Abstract = {The effect of reduction in dose levels normally used in
             mammographic screening procedures on the detection of breast
             lesions were analyzed. Four types of breast lesions were
             simulated and inserted into clinically-acquired digital
             mammograms. Dose reduction by 50% and 75% of the original
             clinically-relevant exposure levels were simulated by adding
             corresponding simulated noise into the original mammograms.
             The mammograms were converted into luminance values
             corresponding to those displayed on a clinical soft-copy
             display station and subsequently analyzed by Laguerre-Gauss
             and Gabor channelized Hotelling observer models for
             differences in detectability performance with reduction in
             radiation dose. Performance was measured under a signal
             known exactly but variable detection task paradigm in terms
             of receiver operating characteristics (ROC) curves and area
             under the ROC curves. The results suggested that luminance
             mapping of digital mammograms affects performance of model
             observers. Reduction in dose levels by 50% lowered the
             detectability of masses with borderline statistical
             significance. Dose reduction did not have a statistically
             significant effect on detection of microcalcifications. The
             model results indicate that there is room for optimization
             of dose level in mammographic screening procedures.},
   Language = {eng},
   Doi = {10.1118/1.2756607},
   Key = {fds269445}
}

@article{fds269245,
   Author = {Li, X and Samei, E and Thomas, A and Colsher, J and Toth, T and Frush,
             D},
   Title = {Evaluation of a noise addition software for simulating low
             dose MDCT images},
   Journal = {Medical physics},
   Volume = {34},
   Number = {6},
   Pages = {2344-2344},
   Year = {2007},
   Month = {June},
   ISSN = {0094-2405},
   url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000247479600119&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
   Doi = {10.1118/1.2760405},
   Key = {fds269245}
}

@article{fds269253,
   Author = {Bowsher, J and Yin, F and Chawla, A and Greer, K and Song, H and Samei, E and Willett, C},
   Title = {TH-D-M100F-01: An Evaluation of Noise in Radiotracer
             Emission Imaging Using Flat-Panel Detectors},
   Journal = {Medical physics},
   Volume = {34},
   Number = {6Part23},
   Pages = {2636-2636},
   Year = {2007},
   Month = {June},
   ISSN = {0094-2405},
   url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000247479601307&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
   Doi = {10.1118/1.2761701},
   Key = {fds269253}
}

@article{fds269265,
   Author = {Williams, M and Raghunathan, P and Seibert, JA and Kwan, A and Lo, J and Samei, E and Ranger, N and Fajardo, L and McGruder, A and Maxwell, S and Maidment, A and Yaffe, M and Bloomquist, A and Mawdsley,
             G},
   Title = {Optimizing mammography image quality and dose: X-ray
             spectrum and exposure parameter selection},
   Journal = {Medical physics},
   Volume = {34},
   Number = {6},
   Pages = {2540-2541},
   Year = {2007},
   Month = {June},
   ISSN = {0094-2405},
   url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000247479600938&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
   Doi = {10.1118/1.2761315},
   Key = {fds269265}
}

@article{fds269270,
   Author = {Samei, E},
   Title = {Image quality measurement workshop},
   Journal = {Medical physics},
   Volume = {34},
   Number = {6},
   Pages = {2570-2571},
   Year = {2007},
   Month = {June},
   ISSN = {0094-2405},
   url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000247479601056&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
   Doi = {10.1118/1.2761436},
   Key = {fds269270}
}

@article{fds269275,
   Author = {Lo, JY and Singh, S and III, DJT and Samei, E},
   Title = {New developments in digital breast tomosynthesis},
   Journal = {Medical physics},
   Volume = {34},
   Number = {6},
   Pages = {2518-2518},
   Year = {2007},
   Month = {June},
   ISSN = {0094-2405},
   url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000247479600854&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
   Doi = {10.1118/1.2761222},
   Key = {fds269275}
}

@article{fds269448,
   Author = {Ranger, NT and Samei, E and Dobbins, JT and Ravin,
             CE},
   Title = {Assessment of detective quantum efficiency: intercomparison
             of a recently introduced international standard with prior
             methods.},
   Journal = {Radiology},
   Volume = {243},
   Number = {3},
   Pages = {785-795},
   Year = {2007},
   Month = {June},
   ISSN = {0033-8419},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/17517933},
   Keywords = {Equipment Failure Analysis • Internationality* •
             Practice Guidelines as Topic* • Radiographic Image
             Enhancement • Reference Standards •
             Reproducibility of Results • Sensitivity and
             Specificity • instrumentation* • methods* •
             standards*},
   Abstract = {PURPOSE: To prospectively evaluate the recently introduced
             international standard method for measurement of the
             detective quantum efficiency (DQE) of digital radiography
             systems, in comparison with representative prior methods.
             MATERIALS AND METHODS: A recently introduced international
             standard method (International Electrotechnical Commission
             [IEC] 62220-1, 2003) for DQE measurement and two previously
             described DQE evaluation methods were considered. In
             addition to an overall comparison, evaluations of the
             following method factors were performed: beam quality,
             beam-limiting devices (apertures or collimators), noise
             power spectrum (NPS) analysis algorithms and parameters
             (area, region of interest size, background detrending), and
             modulation transfer function (MTF) test devices and methods.
             RESULTS: Overall, at low to middle frequencies, the IEC
             method yielded DQE estimates that were 3.3% and 6.5% lower
             than the values yielded by the two previous methods.
             Averaged over the frequency range of 1.5-2.5 mm(-1), the DQE
             estimate derived by using the IEC method was 7.1% lower and
             12.4% higher than the estimates derived by using the other
             two methods. Results obtained with the two previous DQE
             evaluation methods agreed well (within 2.0%) in the low- to
             middle-frequency range but diverged by up to 10% at higher
             frequencies. When the DQE method factors were evaluated
             separately, the largest percentage deviations in DQE were
             associated with (in order of decreasing influence) the MTF
             analysis method ( approximately 11%), the beam limitation
             (about 7%-10%), the beam quality ( approximately 9%), and
             the NPS analysis method ( approximately 3%). CONCLUSION:
             Comparison of DQE estimates obtained by using the recently
             introduced international standard technique with those
             obtained by using prior methods revealed that the overall
             measurement method can affect the DQE estimate by as much as
             12%. Findings further suggest that both beam limitation
             achieved by means of internal collimation (rather than
             external apertures) and use of a radio-opaque edge MTF
             device yield a more accurate estimation of the
             DQE.},
   Language = {eng},
   Doi = {10.1148/radiol.2433060485},
   Key = {fds269448}
}

@article{fds327280,
   Author = {Ranger, N and Mackenzie, A and Honey, I and Dobbins, J and Ravin, C and Samei, E},
   Title = {TU-EE-A4-06: Experimental Evaluation of Effective Detective
             Quantum Efficiency for Digital Radiographic Imaging
             Systems},
   Journal = {Medical physics},
   Volume = {34},
   Number = {6Part18},
   Pages = {2564-2564},
   Year = {2007},
   Month = {June},
   url = {http://dx.doi.org/10.1118/1.2761409},
   Abstract = {Purpose: To develop and evaluate an experimental methodology
             for measuring the effective detective quantum efficiency
             (eDQE) of digital radiographic systems which reflects the
             actual signal‐to‐noise performance of the system per
             unit exposure. Method and Materials: A NEXT phantom,
             simulating the scatter and attenuation properties of an
             adult human thorax was used to measure the resolution,
             noise, and scatter performance of a digital radiographic
             system (GE xQi) under conditions approximating those seen in
             clinical chest radiography. The resolution was measured in
             terms of the modulation transfer function (MTF) using an
             edge device placed at the phantom surface closest to the
             x‐ray tube. The noise was measured in terms of the noise
             power spectrum (NPS) of the region corresponding to the
             phantom center, acquired at three exposure levels. The
             scatter fraction (SF) was evaluated using a beam‐stop
             technique. These measurements along with measures of phantom
             attenuation and estimates of x‐ray flux and exposure were
             incorporated in the computation of the effective Detective
             Quantum Efficiency (eDQE). Results: The phantom exhibited a
             broad‐beam transmission fraction of 18.65%. The measured
             scatter fraction in the presence of grid and phantom was
             33%. The MTF of the system dropped by 25% at 1.0 cycles/mm
             when the edge was placed at the phantom surface due to
             scatter and focal spot blurring. The computed eDQE was
             assessed to be 0.038 and 0.028 at 0.5 and 1.0 cycles/mm,
             respectively (for E= 5.6 mR). Conclusion: Conventional DQE
             measurements performed under relatively idealized conditions
             do not accurately represent the relative performance of
             digital radiographic imaging systems in routine clinical
             use. A more appropriate metric, the eDQE, measured under
             conditions that reasonably approximate those encountered
             clinically reflects the additional contributions from
             scatter, grid, and focal spot blurring, and provides a
             better estimate of the relative clinical performance of
             digital radiographic imaging systems. © 2007, American
             Association of Physicists in Medicine. All rights
             reserved.},
   Doi = {10.1118/1.2761409},
   Key = {fds327280}
}

@article{fds269444,
   Author = {Samei, E and Poolla, A and Ulissey, MJ and Lewin,
             JM},
   Title = {Digital mammography: comparative performance of color LCD
             and monochrome CRT displays.},
   Journal = {Academic Radiology},
   Volume = {14},
   Number = {5},
   Pages = {539-546},
   Year = {2007},
   Month = {May},
   ISSN = {1076-6332},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/17434067},
   Keywords = {Analysis of Variance • Breast Neoplasms • Data
             Display* • Female • Humans • Liquid Crystals
             • Mammography • ROC Curve • Radiographic
             Image Enhancement • User-Computer Interface* •
             methods* • radiography*},
   Abstract = {RATIONALE AND OBJECTIVES: To evaluate the comparative
             performance of high-fidelity liquid crystal display (LCD)
             and cathode ray tube (CRT) devices for mammography
             applications, and to assess the impact of LCD viewing angle
             on detection accuracy. MATERIALS AND METHODS: Ninety 1 k x 1
             k images were selected from a database of digital
             mammograms: 30 without any abnormality present, 30 with
             subtle masses, and 30 with subtle microcalcifications. The
             images were used with waived informed consent, Health
             Insurance Portability and Accountability Act compliance, and
             Institutional Review Board approval. With postprocessing
             presentation identical to those of the commercial
             mammography system used, 1 k x 1 k sections of images were
             viewed on a monochrome CRT and a color LCD in native
             grayscale, and with a grayscale representative of images
             viewed from a 30 degrees or 50 degrees off-normal viewing
             angle. Randomized images were independently scored by four
             experienced breast radiologists for the presence of lesions
             using a 0-100 grading scale. To compare diagnostic
             performance of the display modes, observer scores were
             analyzed using receiver operating characteristic (ROC) and
             analysis of variance. RESULTS: For masses and
             microcalcifications, the detection rate in terms of the area
             under the ROC curve (A(z)) showed a 2% increase and a 4%
             decrease from CRT to LCD, respectively. However, differences
             were not statistically significant (P > .05). The viewing
             angle data showed better microcalcification detection but
             lower mass detection at 30 degrees viewing orientation. The
             overall results varied notably from observer to observer
             yielding no statistically discernible trends across all
             observers, suggesting that within the 0-50 degrees viewing
             angle range and in a controlled observer experiment, the
             variation in the contrast response of the LCD has little or
             no impact on the detection of mammographic lesions.
             CONCLUSIONS: Although CRTs and LCDs differ in terms of
             angular response, resolution, noise, and color, these
             characteristics seem to have little influence on the
             detection of mammographic lesions. The results suggest
             comparable performance in clinical applications of the two
             devices.},
   Language = {eng},
   Doi = {10.1016/j.acra.2007.01.022},
   Key = {fds269444}
}

@article{fds269446,
   Author = {Samei, E and Stebbins, SA and Dobbins, JT and McAdams, HP and Lo,
             JY},
   Title = {Multiprojection correlation imaging for improved detection
             of pulmonary nodules.},
   Journal = {AJR. American journal of roentgenology},
   Volume = {188},
   Number = {5},
   Pages = {1239-1245},
   Year = {2007},
   Month = {May},
   ISSN = {1546-3141},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/17449766},
   Keywords = {Aged • Algorithms • Cost-Benefit Analysis •
             Female • Humans • Imaging, Three-Dimensional
             • Lung Neoplasms • Male • Middle Aged •
             Phantoms, Imaging • Radiation Dosage •
             Radiographic Image Interpretation, Computer-Assisted* •
             economics • radiography*},
   Abstract = {OBJECTIVE: The purpose of this study was the development and
             preliminary evaluation of multiprojection correlation
             imaging with 3D computer-aided detection (CAD) on chest
             radiographs for cost- and dose-effective improvement of
             early detection of pulmonary nodules. SUBJECTS AND METHODS:
             Digital chest radiographs of 10 configurations of a chest
             phantom and of seven human subjects were acquired in
             multiple angular projections with an acquisition time of 11
             seconds (single breath-hold) and total exposure comparable
             with that of a posteroanterior chest radiograph. An initial
             2D CAD algorithm with two difference-of-gaussians filters
             and multilevel thresholds was developed with an independent
             database of 44 single-view chest radiographs with confirmed
             lesions. This 2D CAD algorithm was used on each projection
             image to find likely suspect nodules. The CAD outputs were
             reconstructed in 3D, reinforcing signals associated with
             true nodules while simultaneously decreasing false-positive
             findings produced by overlapping anatomic features. The
             performance of correlation imaging was tested on two to 15
             projection images. RESULTS: Optimum performance of
             correlation imaging was attained when nine projection images
             were used. Compared with conventional, single-view CAD,
             correlation imaging decreased as much as 79% the frequency
             of false-positive findings in phantom cases at a sensitivity
             level of 65%. The corresponding reduction in false-positive
             findings in the cases of human subjects was 78%. CONCLUSION:
             Although limited by a relatively simple CAD implementation
             and a small number of cases, the findings suggest that
             correlation imaging performs substantially better than
             single-view CAD and may greatly enhance identification of
             subtle solitary pulmonary nodules on chest
             radiographs.},
   Language = {eng},
   Doi = {10.2214/AJR.06.0843},
   Key = {fds269446}
}

@article{fds269464,
   Author = {Badea, CT and Hedlund, LW and De Lin and M and Mackel, JSB and Samei, E and Johnson, GA},
   Title = {Tomographic digital subtraction angiography for lung
             perfusion estimation in rodents.},
   Journal = {Medical physics},
   Volume = {34},
   Number = {5},
   Pages = {1546-1555},
   Year = {2007},
   Month = {May},
   ISSN = {0094-2405},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/17555236},
   Keywords = {Angiography, Digital Subtraction • Animals •
             Female • Lung • Magnetic Resonance Angiography
             • Perfusion • Radiographic Image Enhancement
             • Rats • Rats, Inbred F344 • Tomography,
             X-Ray Computed • blood supply • methods •
             methods* • radiography*},
   Abstract = {In vivo measurements of perfusion present a challenge to
             existing small animal imaging techniques such as magnetic
             resonance microscopy, micro computed tomography, micro
             positron emission tomography, and microSPECT, due to
             combined requirements for high spatial and temporal
             resolution. We demonstrate the use of tomographic digital
             subtraction angiography (TDSA) for estimation of perfusion
             in small animals. TDSA augments conventional digital
             subtraction angiography (DSA) by providing three-dimensional
             spatial information using tomosynthesis algorithms. TDSA is
             based on the novel paradigm that the same time density
             curves can be reproduced in a number of consecutive
             injections of microL volumes of contrast at a series of
             different angles of rotation. The capabilities of TDSA are
             established in studies on lung perfusion in rats. Using an
             imaging system developed in-house, we acquired data for
             four-dimensional (4D) imaging with temporal resolution of
             140 ms, in-plane spatial resolution of 100 microm, and slice
             thickness on the order of millimeters. Based on a structured
             experimental approach, we optimized TDSA imaging providing a
             good trade-off between slice thickness, the number of
             injections, contrast to noise, and immunity to artifacts.
             Both DSA and TDSA images were used to create parametric maps
             of perfusion. TDSA imaging has potential application in a
             number of areas where functional perfusion measurements in
             4D can provide valuable insight into animal models of
             disease and response to therapeutics.},
   Language = {eng},
   Doi = {10.1118/1.2717384},
   Key = {fds269464}
}

@article{fds269466,
   Author = {Samei, E and Saunders, RS and Baker, JA and Delong,
             DM},
   Title = {Digital mammography: effects of reduced radiation dose on
             diagnostic performance.},
   Journal = {Radiology},
   Volume = {243},
   Number = {2},
   Pages = {396-404},
   Year = {2007},
   Month = {May},
   ISSN = {0033-8419},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/17356178},
   Keywords = {Breast Neoplasms • Calcinosis • Dose-Response
             Relationship, Radiation • Female • Humans •
             Mammography • Observer Variation • Radiation
             Dosage • Radiographic Image Enhancement •
             Reproducibility of Results • Sensitivity and
             Specificity • methods* • radiography*},
   Abstract = {PURPOSE: To experimentally determine the relationship
             between radiation dose and observer accuracy in the
             detection and discrimination of simulated lesions for
             digital mammography. MATERIALS AND METHODS: This
             HIPAA-compliant study received institutional review board
             approval; the informed consent requirement was waived. Three
             hundred normal craniocaudal images were selected from an
             existing database of digital mammograms. Simulated
             mammographic lesions that mimicked benign and malignant
             masses and clusters of microcalcifications (3.3-7.4 cm in
             diameter) were then superimposed on images. Images were
             rendered without and with added radiographic noise to
             simulate effects of reducing the radiation dose to one half
             and one quarter of the clinical dose. Images were read by
             five experienced breast imaging radiologists. Results were
             analyzed to determine effects of reduced dose on overall
             interpretation accuracy, detection of microcalcifications
             and masses, discrimination between benign and malignant
             masses, and interpretation time. RESULTS: Overall accuracy
             decreased from 0.83 with full dose to 0.78 and 0.62 with
             half and quarter doses, respectively. The decrease
             associated with transition from full dose to quarter dose
             was significant (P < .01), primarily because of an effect on
             detection of microcalcifications (P < .01) and
             discrimination of masses (P < .05). The level of dose
             reduction did not significantly affect detection of
             malignant masses (P > .5). However, reduced dose resulted in
             an increased mean interpretation time per image by 28% (P <
             .0001). CONCLUSION: These findings suggest that dose
             reduction in digital mammography has a measurable but modest
             effect on diagnostic accuracy. The small magnitude of the
             effect in response to the drastic reduction of dose suggests
             potential for modest dose reductions in digital
             mammography.},
   Language = {eng},
   Doi = {10.1148/radiol.2432061065},
   Key = {fds269466}
}

@article{fds269467,
   Author = {Ruschin, M and Timberg, P and Båth, M and Hemdal, B and Svahn, T and Saunders, RS and Samei, E and Andersson, I and Mattsson, S and Chakrabort, DP and Tingber, A},
   Title = {Dose dependence of mass and microcalcification detection in
             digital mammography: free response human observer
             studies.},
   Journal = {Medical physics},
   Volume = {34},
   Number = {2},
   Pages = {400-407},
   Year = {2007},
   Month = {February},
   ISSN = {0094-2405},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/17388156},
   Keywords = {Breast Neoplasms • Calcinosis • Dose-Response
             Relationship, Radiation • Image Enhancement •
             Image Interpretation, Computer-Assisted • Mammography
             • Observer Variation • Precancerous Conditions
             • Radiation Dosage • Radiographic Image
             Enhancement • Reproducibility of Results •
             Sensitivity and Specificity • methods* •
             radiography*},
   Abstract = {The purpose of this study was to evaluate the effect of dose
             reduction in digital mammography on the detection of two
             lesion types-malignant masses and clusters of
             microcalcifications. Two free-response observer studies were
             performed-one for each lesion type. Ninety screening images
             were retrospectively selected; each image was originally
             acquired under automatic exposure conditions, corresponding
             to an average glandular dose of 1.3 mGy for a standard
             breast (50 mm compressed breast thickness with 50%
             glandularity). For each study, one to three simulated
             lesions were added to each of 40 images (abnormals) while 50
             were kept without lesions (normals). Two levels of simulated
             system noise were added to the images yielding two new image
             sets, corresponding to simulated dose levels of 50% and 30%
             of the original images (100%). The manufacturer's standard
             display processing was subsequently applied to all images.
             Four radiologists experienced in mammography evaluated the
             images by searching for lesions and marking and assigning
             confidence levels to suspicious regions. The search data
             were analyzed using jackknife free-response (JA-FROC)
             methodology. For the detection of masses, the mean
             figure-of-merit (FOM) averaged over all readers was 0.74,
             0.71, and 0.68 corresponding to dose levels of 100%, 50%,
             and 30%, respectively. These values were not statistically
             different from each other (F= 1.67, p=0.19) but showed a
             decreasing trend. In contrast, in the microcalcification
             study the mean FOM was 0.93, 0.67, and 0.38 for the same
             dose levels and these values were all significantly
             different from each other (F = 109.84, p < 0.0001). The
             results indicate that lowering the present dose level by a
             factor of two compromised the detection of
             microcalcifications but had a weaker effect on mass
             detection.},
   Language = {eng},
   Doi = {10.1118/1.2405324},
   Key = {fds269467}
}

@article{fds269453,
   Author = {Chawla, AS and Samei, E},
   Title = {Ambient illumination revisited: a new adaptation-based
             approach for optimizing medical imaging reading
             environments.},
   Journal = {Medical physics},
   Volume = {34},
   Number = {1},
   Pages = {81-90},
   Year = {2007},
   Month = {January},
   ISSN = {0094-2405},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/17278493},
   Keywords = {Data Display* • Diagnostic Imaging • Environment*
             • Humans • Image Enhancement • Image
             Interpretation, Computer-Assisted • Lighting •
             Observer Variation • Quality Control •
             Reproducibility of Results • Sensitivity and
             Specificity • Task Performance and Analysis •
             Visual Perception • methods* •
             physiology*},
   Abstract = {Ambient lighting in soft-copy reading rooms is currently
             kept at low values to preserve contrast rendition in the
             dark regions of a medical image. Low illuminance levels,
             however, create inadequate viewing conditions and may also
             cause eye strain. This eye strain may be potentially
             attributed to notable variations in the luminance adaptation
             state of the reader's eyes when moving the gaze
             intermittently between the brighter display and darker
             surrounding surfaces. This paper presents a methodology to
             minimize this variation and optimize the lighting conditions
             of reading rooms by exploiting the properties of liquid
             crystal displays (LCDs) with low diffuse reflection
             coefficients and high luminance ratio. First, a
             computational model was developed to determine a global
             luminance adaptation value, Ladp, when viewing a medical
             image on display. The model is based on the diameter of the
             pupil size, which depends on the luminance of the observed
             object. Second, this value was compared with the luminance
             reflected off surrounding surfaces, Ls, under various
             conditions of room illuminance, E, different values of
             diffuse reflection coefficients of surrounding surfaces, Rs,
             and calibration settings of a typical LCD. The results
             suggest that for typical luminance settings of current LCDs,
             it is possible to raise ambient illumination to minimize
             differences in eye adaptation, potentially reducing visual
             fatigue while also complying with the TG18 specifications
             for controlled contrast rendition. Specifically, room
             illumination in the 75-150 lux range and surface diffuse
             reflection coefficients in the practical range of 0.13-0.22
             sr(-1) provide an ideal setup for typical LCDs. Future LCDs
             with lower diffuse reflectivity and with higher inherent
             luminance ratios can provide further improvement of
             ergonomic viewing conditions in reading rooms.},
   Language = {eng},
   Doi = {10.1118/1.2402583},
   Key = {fds269453}
}

@article{fds269283,
   Author = {Bowsher, JE and Yin, F and Greer, KL and Chawla, A and Samei, E and Willett, CG},
   Title = {An anger-camera study of scatter effects in
             single-photon-emission imaging with flat-panel
             detectors},
   Journal = {International Journal of Radiation Oncology, Biology,
             Physics},
   Volume = {69},
   Number = {3},
   Pages = {S727-S727},
   Year = {2007},
   ISSN = {0360-3016},
   url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000249950201621&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
   Doi = {10.1016/j.ijrobp.2007.07.2124},
   Key = {fds269283}
}

@article{fds269340,
   Author = {Johnson, JP and Lo, J and Mertelmeier, T and Nafziger, JS and Timberg,
             P and Samei, E},
   Title = {Visual image quality metrics for optimization of breast
             tomosynthesis acquisition technique},
   Journal = {Proceedings of SPIE},
   Volume = {6515},
   Year = {2007},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.712343},
   Abstract = {Breast tomosynthesis is currently an investigational imaging
             technique requiring optimization of its many combinations of
             data acquisition and image reconstruction parameters for
             optimum clinical use. In this study, the effects of several
             acquisition parameters on the visual conspicuity of
             diagnostic features were evaluated for three breast
             specimens using a visual discrimination model (VDM).
             Acquisition parameters included total exposure, number of
             views, full resolution and binning modes, and lag
             correction. The diagnostic features considered in these
             specimens were mass margins, microcalcifications, and mass
             spicules. Metrics of feature contrast were computed for each
             image by defining two regions containing the selected
             feature (Signal) and surrounding background (Noise), and
             then computing the difference in VDM channel metrics between
             Signal and Noise regions in units of just-noticeable
             differences (JNDs). Scans with 25 views and exposure levels
             comparable to a standard two-view mammography exam produced
             higher levels of feature contrast. The effects of binning
             and lag correction on feature contrast were found to be
             generally small and isolated, consistent with our visual
             assessments of the images. Binning produced a slight loss of
             spatial resolution which could be compensated in the
             reconstruction filter. These results suggest that good image
             quality can be achieved with the faster and therefore more
             clinically practical 25-view scans with binning, which can
             be performed in as little as 12.5 seconds. Further work will
             investigate other specimens as well as alternate figures of
             merit in order to help determine optimal acquisition and
             reconstruction parameters for clinical trials.},
   Doi = {10.1117/12.712343},
   Key = {fds269340}
}

@article{fds269341,
   Author = {Jr, RSS and Samei, E and Majdi-Nasab, N and Lo, JY},
   Title = {Initial human subject results for breast Bi-plane
             correlation imaging technique},
   Journal = {Proceedings of SPIE},
   Volume = {6514},
   Number = {PART 2},
   Year = {2007},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.713722},
   Abstract = {Computer aided detection (CADe) systems often present
             multiple false-positives per image in projection mammography
             due to overlapping anatomy. To reduce the number of such
             false-positives, we propose performing CADe on image pairs
             acquired using a bi-plane correlation imaging (BCI)
             technique. In this technique, images are acquired of each
             breast at two different projection angles. A traditional
             CADe algorithm operates on each image to identify suspected
             lesions. The suspicious areas from both projections are then
             geometrically correlated, eliminating any lesion that is not
             identified on both views. Proof of concept studies showed
             that that the BCI technique reduced the numbers of
             false-positives per case up to 70%. (This work was supported
             in part by grants from the Department of Defense (USAMRMC
             W81XWH-04-1-0323), Komen Foundation (PDF55806), NIH
             (R01-CA-109074 and R01-CA-112437), Cancer Research and
             Prevention Foundation, and a research agreement with Siemens
             Medical Solutions.).},
   Doi = {10.1117/12.713722},
   Key = {fds269341}
}

@article{fds269361,
   Author = {Chen, Y and Lo, JY and Ranger, NT and Samei, E and III,
             JTD},
   Title = {Methodology of NEQ (f) analysis for optimization and
             comparison of digital breast tomosynthesis acquisition
             techniques and reconstruction algorithms},
   Journal = {Proceedings of SPIE},
   Volume = {6510},
   Number = {PART 1},
   Year = {2007},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.713737},
   Abstract = {As a new three-dimensional imaging technique, digital breast
             tomosynthesis allows the reconstruction of an arbitrary set
             of planes in the breast from a limited-angle series of
             projection images. Though several tomosynthesis algorithms
             have been proposed, no complete optimization and comparison
             of different tomosynthesis acquisition techniques for
             available methods has been conducted as of yet. This paper
             represents a methodology of noise-equivalent quanta NEQ (f)
             analysis to optimize and compare the efficacy of
             tomosynthesis algorithms and imaging acquisition techniques
             for digital breast tomosynthesis. It combines the modulation
             transfer function (MTF) of system signal performance and the
             noise power spectrum (NPS) of noise characteristics. It
             enables one to evaluate the performance of different
             acquisition parameters and algorithms for comparison and
             optimization purposes. An example of this methodology was
             evaluated on a selenium-based direct-conversion flat-panel
             Siemens Mammomat Novation prototype system. An edge method
             was used to measure the presampled MTF of the detector. The
             MTF associated with the reconstruction algorithm and
             specific acquisition technique was investigated by
             calculating the Fourier Transform of simulated impulse
             responses. Flat field tomosynthesis projection sequences
             were acquired and then reconstructed. A mean-subtracted NPS
             on the reconstructed plane was studied to remove fixed
             pattern noise. An example of the application of this
             methodology was illustrated in this paper using a
             point-by-point Back Projection correction (BP)
             reconstruction algorithm and an acquisition technique of 25
             projections with 25 degrees total angular tube
             movement.},
   Doi = {10.1117/12.713737},
   Key = {fds269361}
}

@article{fds269316,
   Author = {McKinley, RL and Tornai, MP and Floyd, CE and Samei,
             E},
   Title = {A contrast-detail comparison of computed mammotomography and
             digital mammography},
   Journal = {Proceedings of SPIE},
   Volume = {6510},
   Number = {PART 1},
   Year = {2007},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.713032},
   Abstract = {We use a contrast-detail observer study to compare
             performance of a novel 3D computed mammotomography (CmT)
             system with a commercially developed full-field digital
             mammography (FFDM) system. A contrast-detail phantom
             comprised of uniform acrylic spheres of various diameters
             was developed and placed in a variety of mediums including
             uniform water (simulating low contrast lesions within a
             uniform background), water and acrylic yarn (simulating low
             contrast lesions with over/under-lying structure), oil only
             (simulating higher contrast lesions in a uniform
             background), and oil and acrylic yarn (simulating higher
             contrast lesions with over/under-lying structure). For CmT,
             the phantom was placed in a 14.6 cm diameter uncompressed
             breast phantom and projections acquired using a simple
             circular orbit, W-target tube, 60 kVp tube potential, 0.05
             cm Ce filtration, 4 mAs per projection, and a CsI(Tl)
             digital x-ray detector. Reconstructions used an iterative
             OSTR algorithm. For FFDM, the phantom was placed in a
             5.3-cm-thick compressed breast phantom. Single CC-view
             mammograms were acquired using a clinical W-target tube with
             50 um Rh filtration, 28 kVp, photo-timed mAs per our
             clinical mammography operation, and a Selenium-based
             flat-panel detector (Mammomat Novation, Siemens). Six
             observers evaluated the images in terms of the number of
             detectable spheres. FFDM performed significantly better for
             the low contrast lesions in uniform water background
             (p&lt;0.05). However, CmT performed significantly better for
             all other cases (p&lt;0.05). Results indicate that CmT shows
             significant advantage in soft tissue detection over FFDM in
             otherwise low contrast dense breasts.},
   Doi = {10.1117/12.713032},
   Key = {fds269316}
}

@article{fds269317,
   Author = {Peppler, W and Hong, W and Steinhauser, R and Whiting, B and Samei, E and Flynn, M and Don, S and Corradini, N},
   Title = {Validation of software for QC assessment of MTF and
             NPS},
   Journal = {Proceedings of SPIE},
   Volume = {6510},
   Number = {PART 3},
   Year = {2007},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.713434},
   Abstract = {Modulation transfer function (MTF), noise power spectrum
             (NPS), and detective quantum efficiency (DQE) are widely
             accepted measures of digital radiographic system
             performance. However the implementation of these measurement
             methodologies has been limited to a handful of researchers
             using an assortment of techniques. A prototype edge tool and
             easy-to-use software program, which can generate MTF, NPS,
             and DQE results quickly and easily in the field, have been
             developed. The edge tool consists of 1mm or 250 μ thick
             tungsten with two polished edges. Edge and NPS data were
             obtained and analyzed by 3 investigators using three
             analysis methods: Method A, the software under development
             for this report; Method B, code available on the web site of
             one of the investigators [Saunders and Samei, Med. Phys. 33,
             308-319 (2006)]; and Method C, code developed by two other
             of the investigators [Samei and Flynn, Med Phy. 30, 608-622,
             (2003)]. In all cases the differences between the results
             using Method B and Method A were less than 1%. The
             differences between Method A and Method C were larger, up to
             5.26%. NPS were calculated using Method A and B. The results
             were very close, with average errors less than 2.5% for
             exposures of 27.3, 9.3, and 2.7 uGy. Analysis of data for a
             10 cm misalignment shows no significant error for either the
             250μ or 1mm edge. The method developed gives results that
             correlate closely with results obtained from established
             methods. The software is easy-to-use and flexible in its
             application. The Edge Tool developed has the necessary
             precision to accurately determine the MTF values of the
             system. Further validation of NPS and DQE is
             ongoing.},
   Doi = {10.1117/12.713434},
   Key = {fds269317}
}

@article{fds269318,
   Author = {Chawla, AS and Samei, E},
   Title = {Geometrical repeatability and motion blur analysis of a new
             multi-projection X-ray imaging system},
   Journal = {IEEE Nuclear Science Symposium Conference
             Record},
   Volume = {5},
   Pages = {3170-3173},
   Year = {2007},
   ISSN = {1095-7863},
   url = {http://dx.doi.org/10.1109/NSSMIC.2006.356548},
   Abstract = {We report on the reproducibility and tests for possible
             motion blur artifacts of a new high frame-rate prototype
             x-ray multi-projection system recently installed in the
             Radiology Department of Duke University. The system, which
             has a translating x-ray tube but a stationary detector, is
             capable of acquiring oblique-angled full field projection
             images along both the vertical and horizontal axes at
             variable speeds and acquisition frame rates. The angular
             span of the tube movement is +7.5° to -7.5° about the
             posterior-anterior (PA) orientation. To analyze the effect
             of possible blurring artifact due to motion of the x-ray
             tube, multi-angled projection images of an edge device were
             acquired. The Modulation Transfer Function (MTF) determined
             from the PA projection acquired with and without the tube in
             motion was compared to investigate blur artifacts that may
             be introduced due to motion of the x-ray tube. Geometrical
             precision of the system was assessed at two tube speeds by
             evaluating the recorded position coordinates as well as edge
             positions in repeated acquisitions. Excellent geometrical
             consistency was found in the tube motion. The positional
             errors at tube speeds of 1 and 2 in/sec were found to be
             within 1%. The possible effect on the MTF due to motion of
             the tube was found to be inconsequential. The system was
             deemed ready for actual clinical trials with these
             acquisition parameters. © 2006 IEEE.},
   Doi = {10.1109/NSSMIC.2006.356548},
   Key = {fds269318}
}

@article{fds269319,
   Author = {Chawla, AS and Boyce, S and Samei, E},
   Title = {Design of a new multi-projection imaging system for chest
             radiography},
   Journal = {IEEE Nuclear Science Symposium Conference
             Record},
   Volume = {4},
   Pages = {2996-2999},
   Year = {2007},
   ISSN = {1095-7863},
   url = {http://dx.doi.org/10.1109/NSSMIC.2007.4436764},
   Abstract = {Overlapping anatomical structures may confound detection of
             lung nodules in conventional projection chest radiography.
             To alleviate the visual clutter due to overlying anatomy, a
             dedicated digital multi-projection system for chest imaging
             was recently developed at the Radiology Department of Duke
             University. The system has a translating x-ray tube and
             acquires multiple projections of the same patient in rapid
             succession from slightly different angles about the
             posterioranterior (PA) orientation. Geometric correlation
             information across these multiple projections is used to
             positively identify suspicious nodules and reduce false
             alarms. The unique feature of this system is that it can
             acquire images along both the horizontal and vertical axes
             and is therefore capable of traversing an arbitrary
             trajectory on a plane parallel to the detector. We are
             reporting the physical design considerations in the
             development of the multi-projection imaging system and the
             initial performance in our ongoing clinical trials using the
             system. Future application in correlation imaging and
             stereoscopic imaging are also noted. © 2007
             IEEE.},
   Doi = {10.1109/NSSMIC.2007.4436764},
   Key = {fds269319}
}

@article{fds269352,
   Author = {Xiang, L and Samei, E and Yoshizumi, T and Colsher, JG and Jones, RP and Frush, DP},
   Title = {Experimental benchmarking of a Monte Carlo dose simulation
             code for pediatric CT},
   Journal = {Proceedings of SPIE},
   Volume = {6510},
   Number = {PART 2},
   Year = {2007},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.713728},
   Abstract = {In recent years, there has been a desire to reduce CT
             radiation dose to children because of their susceptibility
             and prolonged risk for cancer induction. Concerns arise,
             however, as to the impact of dose reduction on image quality
             and thus potentially on diagnostic accuracy. To study the
             dose and image quality relationship, we are developing a
             simulation code to calculate organ dose in pediatric CT
             patients. To benchmark this code, a cylindrical phantom was
             built to represent a pediatric torso, which allows
             measurements of dose distributions from its center to its
             periphery. Dose distributions for axial CT scans were
             measured on a 64-slice multidetector CT (MDCT) scanner (GE
             Healthcare, Chalfont St. Giles, UK). The same measurements
             were simulated using a Monte Carlo code (PENELOPE,
             Universität de Barcelona) with the applicable CT geometry
             including bowtie filter. The deviations between simulated
             and measured dose values were generally within 5%. To our
             knowledge, this work is one of the first attempts to compare
             measured radial dose distributions on a cylindrical phantom
             with Monte Carlo simulated results. It provides a simple and
             effective method for benchmarking organ dose simulation
             codes and demonstrates the potential of Monte Carlo
             simulation for investigating the relationship between dose
             and image quality for pediatric CT patients.},
   Doi = {10.1117/12.713728},
   Key = {fds269352}
}

@article{fds269383,
   Author = {Chawla, AS and Samei, E and Abbey, C},
   Title = {A mathematical model approach towards combining information
             from multiple image projections of the same
             patient},
   Journal = {Proceedings of SPIE},
   Volume = {6510},
   Number = {PART 1},
   Year = {2007},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.713651},
   Abstract = {The purpose of this study was to, i) use a mathematical
             observer model to combine information obtained from multiple
             angular projections of the same breast to determine the
             overall detectability of a simulated lesion in a
             multi-projection breast imaging system and, ii) determine
             the optimum acquisition parameters of such a system.
             Multi-projection imaging is similar to tomosynthesis, except
             that the raw projection images are directly analyzed instead
             of reconstructing those images, thereby avoiding
             reconstruction artifacts. 25 angular projections of each
             breast from 82 human subjects in our tomosynthesis clinical
             trials were supplemented with projections from a simulated 3
             mm 3D lesion. The lesion was assumed to be embedded in the
             compressed breast at a distance of 3 cm from the detector.
             The contrast of the lesion was determined taking into
             account the energy spectrum of the x-ray beam, properties of
             the digital detector, scatter fraction, and compressed
             breast thickness. A linear Hotelling observer with
             Laguerre-Gauss channels (LG CHO) was applied to each image.
             Detectability was analyzed in terms of ROC curves and the
             area under ROC curves (AUC). Three different methods were
             used to integrate ROCs from multiple (correlated) views to
             obtain one combined ROC as an overall metric of
             detectability. Specifically, 1) ROCs from different
             projections were simply averaged; 2) the test statistics
             from different projections were averaged; and 3) a Bayesian
             decision fusion rule was used. Finally, the number of
             angular projections, angular span and the acquisition dose
             level were optimized for highest AUC of the combined ROC as
             a parameter to maximize the performance of the system. It
             was found that the Bayesian decision fusion technique
             performs better than the other two techniques and likely
             offers the best approximation of the diagnostic process.
             Furthermore, if the total dose level is held constant at
             1/25 th of the standard dual-view mammographic screening
             dose, the highest detectability performance is observed when
             considering only two projections spread along an angular
             span of 11.4°.},
   Doi = {10.1117/12.713651},
   Key = {fds269383}
}

@article{fds269384,
   Author = {Chawla, AS and Pollard, B and Samei, E and Hashimoto,
             N},
   Title = {Effect of increased ambient lighting on detectability - A
             psychophysical study},
   Journal = {Proceedings of SPIE},
   Volume = {6516},
   Year = {2007},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.713559},
   Abstract = {Last year in this conference, we presented a theoretical
             analysis of how ambient lighting in dark reading rooms could
             be moderately increased without compromising the
             interpretation of images displayed on LCDs.' Based on that
             analysis, in this paper we present results of two
             psychophysical experiments which were designed to verify
             those theoretical predictions. The first experiment was
             designed to test how an increase in ambient lighting affects
             the detection of subtle objects at different luminance
             levels, particularly at lower luminance levels. Towards that
             end, images of targets consisting of low-contrast objects
             were shown to seven observers, first under a dark room
             illumination condition of 1 lux and then under a higher room
             illumination condition of 50 lux. The targets had three base
             luminance values of 1, 12 and 35 cd/m 2 and were embedded in
             a uniform background. The uniform background was set to 12
             cd/m 2 which enabled fixing L adp, the visual adaptation
             luminance value when looking at the display, to 12 cd/m 2.
             This value also matched the luminance value of about 12 cd/m
             2 reflected off the wall surrounding the LCD at the higher
             ambient lighting condition. The task of the observers was to
             detect and classify the displayed objects under the two room
             lighting conditions. The results indicated that the
             detection rate in dark area (base luminance of 1 cd/m 2)
             increased by 15% when the ambient illumination is increased
             from 1 to 50 lux. The increase was not conclusive for
             targets embedded in higher luminance regions, but there was
             no evidence to the contrary either. The second experiment
             was designed to investigate the adaptation luminance value
             of the eye when viewing typical mammograms. It was found
             that, for a typical display luminance calibration, this
             value might lie between 12 and 20 cd/m 2. Findings from the
             two experiments provide justification for a controlled
             increase of ambient lighting to improve ergonomic viewing
             conditions in darkly lit reading rooms while potentially
             improving diagnostic performance.},
   Doi = {10.1117/12.713559},
   Key = {fds269384}
}

@article{fds269456,
   Author = {McAdams, HP and Samei, E and Dobbins, J and Tourassi, GD and Ravin,
             CE},
   Title = {Recent advances in chest radiography.},
   Journal = {Radiology},
   Volume = {241},
   Number = {3},
   Pages = {663-683},
   Year = {2006},
   Month = {December},
   ISSN = {0033-8419},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/17114619},
   Keywords = {Data Display • Humans • Image Processing,
             Computer-Assisted • Radiographic Image Interpretation,
             Computer-Assisted • Radiography, Thoracic •
             Scattering, Radiation • Subtraction Technique •
             X-Ray Intensifying Screens • methods* •
             trends*},
   Abstract = {There have been many remarkable advances in conventional
             thoracic imaging over the past decade. Perhaps the most
             remarkable is the rapid conversion from film-based to
             digital radiographic systems. Computed radiography is now
             the preferred imaging modality for bedside chest imaging.
             Direct radiography is rapidly replacing film-based chest
             units for in-department posteroanterior and lateral
             examinations. An exciting aspect of the conversion to
             digital radiography is the ability to enhance the diagnostic
             capabilities and influence of chest radiography.
             Opportunities for direct computer-aided detection of various
             lesions may enhance the radiologist's accuracy and improve
             efficiency. Newer techniques such as dual-energy and
             temporal subtraction radiography show promise for improved
             detection of subtle and often obscured or overlooked lung
             lesions. Digital tomosynthesis is a particularly promising
             technique that allows reconstruction of multisection images
             from a short acquisition at very low patient dose.
             Preliminary data suggest that, compared with conventional
             radiography, tomosynthesis may also improve detection of
             subtle lung lesions. The ultimate influence of these new
             technologies will, of course, depend on the outcome of
             rigorous scientific validation.},
   Language = {eng},
   Doi = {10.1148/radiol.2413051535},
   Key = {fds269456}
}

@article{fds269470,
   Author = {Saunders, RS and Samei, E},
   Title = {Improving mammographic decision accuracy by incorporating
             observer ratings with interpretation time.},
   Journal = {British Journal of Radiology},
   Volume = {79 Spec No 2},
   Pages = {S117-S122},
   Year = {2006},
   Month = {December},
   ISSN = {1748-880X},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/17209116},
   Keywords = {Breast Neoplasms • Clinical Competence • Decision
             Making • Female • Humans • Mammography •
             Observer Variation • Patient Simulation •
             Sensitivity and Specificity • Time Factors •
             radiography* • standards*},
   Abstract = {Mammography is currently the most established technique for
             the early detection of breast cancer. However, mammography
             would benefit from further improvements as it does produce
             some errors, such as not finding all early-stage cancers.
             The objectives of this study were first, to measure the
             timing of correct and incorrect reading decisions in
             mammography and second, to exploit those dependencies to
             improve accuracy in mammographic interpretation. To address
             these objectives, an experiment was conducted where
             experienced breast imaging radiologists reviewed 400
             mammographic regions equally divided among images that
             contained simulated benign masses, malignant masses,
             malignant microcalcifications and no lesions. The experiment
             recorded the radiologists' decision as well as the length of
             time the mammogram was interpreted in. The experiment
             results showed that incorrect detection as well as incorrect
             classification decisions were associated with longer
             interpretation times (p<0.0001). The timing results were
             used to create a model that would flag cases for review that
             had a higher probability of error. The flagged cases had a
             median accuracy drop of 13% for detection decisions and 16%
             for classification decisions compared with unflagged cases.
             This suggests that interpretation time can be incorporated
             into mammographic decision-making in order to identify cases
             with higher probabilities of perceptual error that require
             further review.},
   Language = {eng},
   Doi = {10.1259/bjr/96931332},
   Key = {fds269470}
}

@article{fds269457,
   Author = {Lin, MD and Samei, E and Badea, CT and Yoshizumi, TT and Johnson,
             GA},
   Title = {Optimized radiographic spectra for small animal digital
             subtraction angiography.},
   Journal = {Medical physics},
   Volume = {33},
   Number = {11},
   Pages = {4249-4257},
   Year = {2006},
   Month = {November},
   ISSN = {0094-2405},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/17153403},
   Keywords = {Algorithms* • Angiography, Digital Subtraction •
             Animals • Image Enhancement • Image
             Interpretation, Computer-Assisted • Rats •
             Reproducibility of Results • Sensitivity and
             Specificity • Spectrometry, X-Ray Emission •
             instrumentation • methods* • veterinary*},
   Abstract = {The increasing use of small animals in basic research has
             spurred interest in new imaging methodologies. Digital
             subtraction angiography (DSA) offers a particularly
             appealing approach to functional imaging in the small
             animal. This study examines the optimal x-ray, molybdenum
             (Mo) or tungsten (W) target sources, and technique to
             produce the highest quality small animal functional
             subtraction angiograms in terms of contrast and
             signal-difference-to-noise ratio squared (SdNR2). Two
             limiting conditions were considered-normalization with
             respect to dose and normalization against tube loading.
             Image contrast and SdNR2 were simulated using an established
             x-ray model. DSA images of live rats were taken at two
             representative tube potentials for the W and Mo sources.
             Results show that for small animal DSA, the Mo source
             provides better contrast. However, with digital detectors,
             SdNR2 is the more relevant figure of merit. The W source
             operated at kVps >60 achieved a higher SdNR2. The highest
             SdNR2 was obtained at voltages above 90 kVp. However,
             operation at the higher potential results in significantly
             greater dose and tube load and reduced contrast
             quantization. A reasonable tradeoff can be achieved at tube
             potentials at the beginning of the performance plateau,
             around 70 kVp, where the relative gain in SdNR2 is the
             greatest.},
   Language = {eng},
   Doi = {10.1118/1.2356646},
   Key = {fds269457}
}

@article{fds269469,
   Author = {Saunders, RS and Samei, E and Baker, J and Delong, D and Soo, MS and Walsh,
             R and Pisano, E and Kuzmiak, CM and Pavic, D},
   Title = {Comparison of LCD and CRT displays based on efficacy for
             digital mammography.},
   Journal = {Academic Radiology},
   Volume = {13},
   Number = {11},
   Pages = {1317-1326},
   Year = {2006},
   Month = {November},
   ISSN = {1076-6332},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/17070449},
   Keywords = {Breast Neoplasms • Calcinosis • Clinical
             Competence • Computer Simulation • Data Display*
             • Equipment Design • Female • Humans •
             Liquid Crystals* • Mammography • Observer
             Variation • Radiographic Image Enhancement •
             Research Design • Sensitivity and Specificity •
             Task Performance and Analysis • User-Computer Interface
             • epidemiology • instrumentation •
             instrumentation* • pathology • pathology* •
             radiography • radiography*},
   Abstract = {RATIONALE AND OBJECTIVES: To compare two display
             technologies, cathode ray tube (CRT) and liquid crystal
             display (LCD), in terms of diagnostic accuracy for several
             common clinical tasks in digital mammography. MATERIALS AND
             METHODS: Simulated masses and microcalcifications were
             inserted into normal digital mammograms to produce an image
             set of 400 images. Images were viewed on one CRT and one LCD
             medical-quality display device by five experienced
             breast-imaging radiologists who rated the images using a
             categorical rating paradigm. The observer data were analyzed
             to determine overall classification accuracy, overall lesion
             detection accuracy, and accuracy for four specific
             diagnostic tasks: detection of benign masses, malignant
             masses, and microcalcifications, and discrimination of
             benign and malignant masses. RESULTS: Radiologists had
             similar overall classification accuracy (LCD: 0.83 +/- 0.01,
             CRT: 0.82 +/- 0.01) and lesion detection accuracy (LCD: 0.87
             +/- 0.01, CRT: 0.85 +/- 0.01) on both displays. The
             difference in accuracy between LCD and CRT for the detection
             of benign masses, malignant masses, and microcalcifications,
             and discrimination of benign and malignant masses was -0.019
             +/- 0.009, 0.020 +/- 0.008, 0.012 +/- 0.013, and 0.0094 +/-
             0.011, respectively. Overall, the two displays did not
             exhibit any statistically significant difference (P > .05).
             CONCLUSION: This study explored the suitability of two
             different soft-copy displays for the viewing of mammographic
             images. It found that LCD and CRT displays offer similar
             clinical utility for mammographic tasks.},
   Language = {eng},
   Doi = {10.1016/j.acra.2006.07.017},
   Key = {fds269469}
}

@article{fds269468,
   Author = {Badano, A and Schneider, S and Samei, E},
   Title = {Visual assessment of angular response in medical liquid
             crystal displays.},
   Journal = {Journal of Digital Imaging},
   Volume = {19},
   Number = {3},
   Pages = {240-248},
   Year = {2006},
   Month = {September},
   ISSN = {0897-1889},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/16741662},
   Keywords = {Computer Peripherals • Contrast Sensitivity • Data
             Display* • Humans • Liquid Crystals* •
             Luminescent Measurements • Observer Variation •
             Pattern Recognition, Visual • Predictive Value of Tests
             • Radiographic Image Enhancement • Reproducibility
             of Results • Task Performance and Analysis •
             Technology, Radiologic • Visual Perception*},
   Abstract = {In spite of having non-Lambertian emission, displays based
             on liquid crystal technology are becoming popular for
             medical diagnostic work stations. For all liquid crystal
             displays (LCDs), the contrast performance varies with
             viewing direction. Accurate measurements of the angular
             distribution of light emission require expensive
             instrumentation and extensive expertise. We investigated the
             possibility of using a test pattern to visually assess the
             angular response performance of LCDs. We found that this
             procedure offers the end user of displays a simple, fast,
             and relatively consistent technique to verify that the
             viewing angle performance of the display device is within
             certain acceptable limits.},
   Language = {eng},
   Doi = {10.1007/s10278-006-0633-5},
   Key = {fds269468}
}

@article{fds269454,
   Author = {Saunders, R and Samei, E and Baker, J and Delong,
             D},
   Title = {Simulation of mammographic lesions.},
   Journal = {Academic Radiology},
   Volume = {13},
   Number = {7},
   Pages = {860-870},
   Year = {2006},
   Month = {July},
   ISSN = {1076-6332},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/16777560},
   Keywords = {Breast Diseases • Breast Neoplasms • Calcinosis
             • Computer Simulation* • Female • Humans
             • Mammography* • Phantoms, Imaging* •
             instrumentation • radiography • radiography*
             • standards},
   Abstract = {RATIONALE AND OBJECTIVES: This study presents a method for
             generating breast masses and microcalcifications in
             mammography via simulation. This simulation method allows
             for the creation of large image datasets with particular
             lesions, which may serve as a useful tool for perception
             studies measuring imaging system performance. MATERIALS AND
             METHODS: The study first characterized the radiographic
             appearance of both masses and microcalcifications, examining
             the following five properties: contrast, edge gradient
             profile of masses, edge characteristics of masses, shapes of
             individual microcalcifications, and shapes of
             microcalcification distributions. The characterization
             results then guided the development of routines that created
             simulated masses and microcalcifications. The quality of the
             simulations was verified by experienced breast imaging
             radiologists who evaluated simulated and real lesions and
             rated whether a given lesion had a realistic appearance.
             RESULTS: The radiologists rated real and simulated lesions
             to have similarly realistic appearances. Using receiver
             operating characteristic analysis to characterize the degree
             of similarity, the results showed an A(z) of 0.68 +/- 0.07
             for benign masses, 0.65 +/- 0.07 for malignant masses, and
             0.62 +/- 0.07 for microcalcifications, thus showing notable
             overlap in the simulated and real lesion ratings.
             CONCLUSION: This research introduced a new approach for
             simulating breast masses and microcalcifications that relied
             on anatomic characteristics measured from real lesions.
             Results from an observer performance experiment indicate
             that our simulation routine produced realistic simulations
             of masses and microcalcifications as judged by expert
             radiologists.},
   Language = {eng},
   Doi = {10.1016/j.acra.2006.03.015},
   Key = {fds269454}
}

@article{fds269244,
   Author = {Bowsher, J and Yin, F and Greer, K and Jaszczak, R and Samei, E and Willett, C},
   Title = {TU-FF-A3-02: Preliminary Investigations Into Combined
             CT/SPECT Imaging Onboard Therapy Machines},
   Journal = {Medical physics},
   Volume = {33},
   Number = {6Part18},
   Pages = {2221-2221},
   Year = {2006},
   Month = {June},
   ISSN = {0094-2405},
   url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000238688502199&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
   Doi = {10.1118/1.2241651},
   Key = {fds269244}
}

@article{fds269261,
   Author = {Samei, E},
   Title = {Evaluation of medical displays},
   Journal = {Medical physics},
   Volume = {33},
   Number = {6},
   Pages = {2169-2169},
   Year = {2006},
   Month = {June},
   ISSN = {0094-2405},
   url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000238688502001&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
   Doi = {10.1118/1.2241446},
   Key = {fds269261}
}

@article{fds269264,
   Author = {Jr, SRS and Samei, E},
   Title = {Does image quality impact mammographic accuracy?},
   Journal = {Medical physics},
   Volume = {33},
   Number = {6},
   Pages = {2265-2266},
   Year = {2006},
   Month = {June},
   ISSN = {0094-2405},
   url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000238688502364&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
   Doi = {10.1118/1.2241844},
   Key = {fds269264}
}

@article{fds269267,
   Author = {Samei, E},
   Title = {Display evaluation demonstration workshop: Part
             II},
   Journal = {Medical physics},
   Volume = {33},
   Number = {6},
   Pages = {2176-2177},
   Year = {2006},
   Month = {June},
   ISSN = {0094-2405},
   url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000238688502032&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
   Doi = {10.1118/1.2241477},
   Key = {fds269267}
}

@article{fds269274,
   Author = {Ranger, NT and Samei, E and Dobbins, JT and Ravin,
             CE},
   Title = {Assessment of detective quantum efficiency: Inter-comparison
             of IEC 62220-1 with representative prior
             methods},
   Journal = {Medical physics},
   Volume = {33},
   Number = {6},
   Pages = {2007-2007},
   Year = {2006},
   Month = {June},
   ISSN = {0094-2405},
   url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000238688500148&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
   Doi = {10.1118/1.2240288},
   Key = {fds269274}
}

@article{fds269449,
   Author = {Borasi, G and Samei, E and Bertolini, M and Nitrosi, A and Tassoni,
             D},
   Title = {Contrast-detail analysis of three flat panel detectors for
             digital radiography.},
   Journal = {Medical physics},
   Volume = {33},
   Number = {6},
   Pages = {1707-1719},
   Year = {2006},
   Month = {June},
   ISSN = {0094-2405},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/16872078},
   Keywords = {Contrast Media • Humans • Models, Statistical
             • Neoplasms • Phantoms, Imaging •
             Radiographic Image Enhancement • Relative Biological
             Effectiveness • X-Ray Intensifying Screens* •
             analysis* • diagnosis* • instrumentation •
             methods* • pathology • radiography*},
   Abstract = {In this paper we performed a contrast detail analysis of
             three commercially available flat panel detectors, two based
             on the indirect detection mechanism (GE Revolution XQ/i,
             system A, and Trixell/Philips Pixium 4600, system B) and one
             based on the direct detection mechanism (Hologic DirectRay
             DR 1000, system C). The experiment was conducted using
             standard x-ray radiation quality and a widely used
             contrast-detail phantom. Images were evaluated using a four
             alternative forced choice paradigm on a diagnostic-quality
             softcopy monitor. At the low and intermediate exposures,
             systems A and B gave equivalent performances. At the high
             dose levels, system A performed better than system B in the
             entire range of target sizes, even though the pixel size of
             system A was about 40% larger than that of system B. At all
             the dose levels, the performances of the system C (direct
             system) were lower than those of system A and B (indirect
             systems). Theoretical analyses based on the Perception
             Statistical Model gave similar predicted SNRT values
             corresponding to an observer efficiency of about 0.08 for
             systems A and B and 0.05 for system C.},
   Language = {eng},
   Doi = {10.1118/1.2191014},
   Key = {fds269449}
}

@article{fds269455,
   Author = {Dobbins, JT and Samei, E and Ranger, NT and Chen,
             Y},
   Title = {Intercomparison of methods for image quality
             characterization. II. Noise power spectrum.},
   Journal = {Medical physics},
   Volume = {33},
   Number = {5},
   Pages = {1466-1475},
   Year = {2006},
   Month = {May},
   ISSN = {0094-2405},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/16752581},
   Keywords = {Algorithms* • Artifacts • Quality Assurance,
             Health Care • Radiographic Image Enhancement •
             Radiographic Image Interpretation, Computer-Assisted •
             Reproducibility of Results • Sensitivity and
             Specificity • Stochastic Processes •
             methods*},
   Abstract = {Second in a two-part series comparing measurement techniques
             for the assessment of basic image quality metrics in digital
             radiography, in this paper we focus on the measurement of
             the image noise power spectrum (NPS). Three methods were
             considered: (1) a method published by Dobbins et al. [Med.
             Phys. 22, 1581-1593 (1995)], (2) a method published by Samei
             et al. [Med. Phys. 30, 608-622 (2003)], and (3) a new method
             sanctioned by the International Electrotechnical Commission
             (IEC 62220-1, 2003), developed as part of an international
             standard for the measurement of detective quantum
             efficiency. In addition to an overall comparison of the
             estimated NPS between the three techniques, the following
             factors were also evaluated for their effect on the measured
             NPS: horizontal versus vertical directional dependence, the
             use of beam-limiting apertures, beam spectrum, and
             computational methods of NPS analysis, including the
             region-of-interest (ROI) size and the method of ROI
             normalization. Of these factors, none was found to
             demonstrate a substantial impact on the amplitude of the NPS
             estimates (< or = 3.1% relative difference in NPS averaged
             over frequency, for each factor considered separately).
             Overall, the three methods agreed to within 1.6% +/- 0.8%
             when averaged over frequencies > 0.15 mm(-1).},
   Language = {eng},
   Doi = {10.1118/1.2188819},
   Key = {fds269455}
}

@article{fds269471,
   Author = {Samei, E and Ranger, NT and Dobbins, JT and Chen,
             Y},
   Title = {Intercomparison of methods for image quality
             characterization. I. Modulation transfer
             function.},
   Journal = {Medical physics},
   Volume = {33},
   Number = {5},
   Pages = {1454-1465},
   Year = {2006},
   Month = {May},
   ISSN = {0094-2405},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/16752580},
   Keywords = {Algorithms* • Quality Assurance, Health Care •
             Radiographic Image Enhancement • Radiographic Image
             Interpretation, Computer-Assisted • Reproducibility of
             Results • Sensitivity and Specificity •
             methods*},
   Abstract = {The modulation transfer function (MTF) and the noise power
             spectrum (NPS) are widely recognized as the most relevant
             metrics of resolution and noise performance in radiographic
             imaging. These quantities have commonly been measured using
             various techniques, the specifics of which can have a
             bearing on the accuracy of the results. As a part of a study
             aimed at comparing the relative performance of different
             techniques, in this paper we report on a comparison of two
             established MTF measurement techniques: one using a slit
             test device [Dobbins et al., Med. Phys. 22, 1581-1593
             (1995)] and another using a translucent edge test device
             [Samei et al., Med. Phys. 25, 102-113 (1998)], with one
             another and with a third technique using an opaque edge test
             device recommended by a new international standard (IEC
             62220-1, 2003). The study further aimed to substantiate the
             influence of various acquisition and processing parameters
             on the estimated MTF. The slit test device was made of 2 mm
             thick Pb slabs with a 12.5 microm opening. The translucent
             edge test device was made of a laminated and polished
             Pt(0.9)Ir(0.1). alloy foil of 0.1 mm thickness. The opaque
             edge test device was made of a 2 mm thick W slab. All test
             devices were imaged on a representative indirect flat-panel
             digital radiographic system using three published beam
             qualities: 70 kV with 0.5 mm Cu filtration, 70 kV with 19 mm
             Al filtration, and 74 kV with 21 mm Al filtration
             (IEC-RQA5). The latter technique was also evaluated in
             conjunction with two external beam-limiting apertures (per
             IEC 62220-1), and with the tube collimator limiting the beam
             to the same area achieved with the apertures. The presampled
             MTFs were deduced from the acquired images by Fourier
             analysis techniques, and the results analyzed for relative
             values and the influence of impacting parameters. The
             findings indicated that the measurement technique has a
             notable impact on the resulting MTF estimate, with estimates
             from the overall IEC method 4.0% +/- 0.2% lower than that of
             Dobbins et al. and 0.7% +/- 0.4% higher than that of Samei
             et al. averaged over the zero to cutoff frequency range.
             Over the same frequency range, keeping beam quality and
             limitation constant, the average MTF estimate obtained with
             the edge techniques differed by up to 5.2% +/- 0.2% from
             that of the slit, with the opaque edge providing lower MTF
             estimates at lower frequencies than those obtained with the
             translucent edge or slit. The beam quality impacted the
             average estimated MTF by as much as 3.7% +/- 0.9% while the
             use of beam limiting devices alone increased the average
             estimated MTF by as much as 7.0% +/- 0.9%. While the slit
             method is inherently very sensitive to misalignment, both
             edge techniques were found to tolerate misalignments by as
             much as 6 cm. The results suggest the use of the opaque edge
             test device and the tube internal collimator for beam
             limitation in order to achieve an MTF result most reflective
             of the overall performance of the imaging system and least
             susceptible to misalignment and scattered radiation. Careful
             attention to influencing factors is warranted to achieve
             accurate results.},
   Language = {eng},
   Doi = {10.1118/1.2188816},
   Key = {fds269471}
}

@article{fds269452,
   Author = {Boyce, SJ and Samei, E},
   Title = {Imaging properties of digital magnification
             radiography.},
   Journal = {Medical physics},
   Volume = {33},
   Number = {4},
   Pages = {984-996},
   Year = {2006},
   Month = {April},
   ISSN = {0094-2405},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/16696475},
   Keywords = {Algorithms* • Equipment Design • Equipment Failure
             Analysis • Information Storage and Retrieval •
             Radiographic Image Enhancement • Radiographic Image
             Interpretation, Computer-Assisted • Reproducibility of
             Results • Sensitivity and Specificity • Signal
             Processing, Computer-Assisted* • Transducers •
             instrumentation • instrumentation* •
             methods*},
   Abstract = {Flat panel detectors exhibit improved signal-to-noise ratio
             (SNR) and display capabilities compared to film. This
             improvement necessitates a new evaluation of optimal
             geometry for conventional projection imaging applications
             such as digital projection mammography as well as for
             advanced x-ray imaging applications including cone-beam
             computed tomography (CT), tomosynthesis, and
             mammotomography. Such an evaluation was undertaken in this
             study to examine the effects of x-ray source distribution,
             inherent detector resolution, magnification, scatter
             rejection, and noise characteristics including noise
             aliasing. A model for x-ray image acquisition was used to
             develop generic results applicable to flat panel detectors
             with similar x-ray absorption characteristics. The model
             assumed a Gaussian distribution for the focal spot and a
             rectangular distribution for a pixel. A generic model for
             the modulated transfer function (MTF) of indirect flat panel
             detectors was derived by a nonlinear fit of empirical
             receptor data to the Burgess model for phosphor MTFs. Noise
             characteristics were investigated using a generic noise
             power spectrum (NPS) model for indirect phosphor-based
             detectors. The detective quantum efficiency (DQE) was then
             calculated from the MTF and NPS models. The results were
             examined as a function of focal spot size (0.1, 0.3, and 0.6
             mm) and pixel size (50, 100, 150, and 200 microm) for
             magnification ranges 1 to 3. Mammography, general
             radiography (also applicable to mammotomography), and chest
             radiography applications were explored using x-ray energies
             of 28, 74, and 120 kVp, respectively. Nodule detection was
             examined using the effective point source scatter model,
             effective DQE, and the Hotelling SNR2 efficiency. Results
             indicate that magnification can potentially improve the
             signal and noise performance of digital images. Results also
             show that a cross over point occurs in the spatial frequency
             above and below which the effects of magnification differ
             indicating that there are task dependent tradeoffs
             associated with magnification. The cross over point varies
             depending upon focal spot size, pixel size, x-ray energy,
             and source-to-image-distance (SID). For mammography, the
             cross over point occurs for a 0.3 mm focal spot while a 0.6
             mm focal spot indicates that magnification does not improve
             image quality due to focal spot blurring. Thus, the benefit
             of magnification may be limited. For general radiography (as
             well as mammotomography), and chest radiography, the cross
             over point changes with SID. For a system with a 0.3 mm
             focal spot, 100 microm pixel size, a 2 m SID, and the
             applicable tissue thickness and scatter components, optimal
             magnification improved SNR2 by approximately 1.2 times for
             mammography and 1.5 times for general radiography (and
             mammotomography). These results indicate that the optimal
             geometry can improve image quality without changing patient
             dose or otherwise reduce dose without compromising image
             quality.},
   Language = {eng},
   Doi = {10.1118/1.2174133},
   Key = {fds269452}
}

@article{fds269451,
   Author = {Samei, E and Wright, SL},
   Title = {Viewing angle performance of medical liquid crystal
             displays.},
   Journal = {Medical physics},
   Volume = {33},
   Number = {3},
   Pages = {645-654},
   Year = {2006},
   Month = {March},
   ISSN = {0094-2405},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/16878568},
   Keywords = {Beta Particles • Calibration • Contrast
             Sensitivity • Data Display* • Diagnostic Imaging
             • Lighting • Liquid Crystals* • Luminescence
             • Optics and Photonics • Radiographic Image
             Enhancement • Reproducibility of Results •
             Sensitivity and Specificity • instrumentation •
             methods*},
   Abstract = {Cathode-ray tube (CRT) and liquid crystal display (LCD) are
             currently two main technologies for displaying medical
             images. LCDs possess a number of advantages, but their
             performance varies as a function of viewing angle. Our
             purpose in this study was to characterize the angular
             response performance of five medical-grade LCDs, and to
             substantiate their impact on their compliance with the DICOM
             gray scale display function (GSDF). Furthermore, the study
             aimed to test a framework to define an angular acceptance
             range for medical LCDs based on the recent AAPM TG18
             guidelines. Measurements were made on five calibrated
             dual-domain LCDs, including two 3 megapixel monochrome LCDs,
             two 5 megapixel monochrome LCDs, and one 9 megapixel color
             LCD. The luminance performance of each display device was
             measured as a function of the viewing angle at 17 discrete
             levels using TG18-LN test patterns and a
             Fourier-optics-based luminance meter. The luminance data
             were analyzed according to the AAPM TG18 methodology. The
             displays showed notable variation in luminance and contrast
             performance as a function of the viewing angle, particularly
             in diagonal viewing orientations. Overall, the luminance
             ratio remained greater than 175 within +/-20 degrees and
             +/-33 degrees viewing angle cones (beta175 = 20 degrees-33
             degrees). Aiming to maintain a maximum deviation from the
             GSDF contrast less than 0.3, i.e., kappa17 < or = 0.3,
             acceptable viewing angle cones of +/-22 degrees and +/-35
             degrees were indicated (alpha 0.3= 22 degrees-35 degrees).
             The findings demonstrate the significant impact of angular
             response on image contrast, and the utility of alpha 0.3 and
             beta175 quantities for defining the viewing angle cones
             within which a medical LCD device can be effectively
             utilized.},
   Language = {eng},
   Doi = {10.1118/1.2168430},
   Key = {fds269451}
}

@article{fds269458,
   Author = {Saunders, RS and Samei, E},
   Title = {Resolution and noise measurements of five CRT and LCD
             medical displays.},
   Journal = {Medical physics},
   Volume = {33},
   Number = {2},
   Pages = {308-319},
   Year = {2006},
   Month = {February},
   ISSN = {0094-2405},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/16532935},
   Keywords = {Algorithms • Data Display* • Diagnostic Imaging
             • Humans • Image Interpretation, Computer-Assisted
             • Noise* • Radiographic Image Enhancement •
             instrumentation • methods*},
   Abstract = {The performance of soft-copy displays plays a significant
             role in the overall image quality of a digital radiographic
             system. In this work, we discuss methods to characterize the
             resolution and noise of both cathode ray tube (CRT) and
             liquid crystal display (LCD) devices. We measured the image
             quality of five different commercial display devices,
             representing both CRT and LCD technologies, using a
             high-quality charge-coupled device (CCD) camera. The
             modulation transfer function (MTF) was calculated using the
             line technique, correcting for the MTF of the CCD camera and
             the display pixel size. The normalized noise power spectrum
             (NPS) was computed from two-dimensional Fourier analysis of
             uniform images. To separate the effects of pixel structure
             from interpixel luminance variations, we created
             structure-free images by eliminating the pixel structures of
             the display device. The NPS was then computed from these
             structure-free images to isolate interpixel luminance
             variations. We found that the MTF of LCDs remained close to
             the theoretical limit dictated by their inherent pixel size
             (0.85 +/- 0.08 at Nyquist frequency), in contrast to the MTF
             for the two CRT displays, which dropped to 0.15 +/- 0.08 at
             the Nyquist frequency. However, the NPS of LCDs showed
             significant peaks due to the subpixel structure, while the
             NPS of CRT displays exhibited a nearly flat power spectrum.
             After removing the pixel structure, the structured noise
             peaks for LCDs were eliminated and the overall noise
             magnitude was significantly reduced. The average total
             noise-to-signal ratio for CRT displays was 6.55% +/- 0.59%,
             of which 6.03% +/- 0.24% was due to interpixel luminance
             variations, while LCD displays had total noise to signal
             ratios of 46.1% +/- 5.1% of which 1.50% +/- 0.41% were due
             to interpixel luminance variations. Depending on the extent
             of the blurring and prewhitening processes of the human
             visual system, the magnitude of the display noise (including
             pixel structure) potentially perceived by the observer was
             reduced to 0.43% +/- 0.01% (accounting for blurring only)
             and 0.40 +/- 0.01% (accounting for blurring and
             prewhitening) for CRTs, and 1.02% +/- 0.22% (accounting for
             blurring only) and 0.36% +/- 0.08% (accounting for blurring
             and prewhitening) for LCDs.},
   Language = {eng},
   Doi = {10.1118/1.2150777},
   Key = {fds269458}
}

@article{fds269459,
   Author = {Hoe, CL and Samei, E and Frush, DP and Delong, DM},
   Title = {Simulation of liver lesions for pediatric
             CT.},
   Journal = {Radiology},
   Volume = {238},
   Number = {2},
   Pages = {699-705},
   Year = {2006},
   Month = {February},
   ISSN = {0033-8419},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/16371579},
   Keywords = {Adolescent • Child • Child, Preschool •
             Computer Simulation* • Humans • Infant •
             Liver Diseases • Phantoms, Imaging* • Tomography,
             X-Ray Computed* • radiography*},
   Abstract = {PURPOSE: To develop and validate a technique based on
             characteristics of real lesions for simulating realistic
             small liver lesions on pediatric computed tomographic (CT)
             images. MATERIALS AND METHODS: The institutional review
             board provided exempt status for this study, determined that
             it was not subject to HIPAA compliance, and did not require
             informed consent. Patient identification information was
             removed from clinical images from contrast material-enhanced
             multi-detector row CT examinations performed in 10 children.
             Patients were infants or children up to 18 years old.
             Information about sex was not available. Children had one or
             more liver lesions of 2-6 mm in maximum transverse diameter.
             Images with more than one lesion were rendered multiple
             times, and each time, all but one of the lesions were
             digitally removed in sequence. This process provided images
             (n = 19) with a single real lesion. For consistency, the
             same image backgrounds (images with all real lesions
             removed) were used to create an identical number of images
             (n = 19), each with a single simulated lesion. Subsequently,
             three radiologists independently assessed images of real and
             simulated lesions that were presented in random order with a
             score on a continuous scale of 0 (definitely simulated) to
             100 (definitely real). Mixed-model analysis of variance was
             used to test the null hypothesis that the difference in
             population mean scores between the two lesion types was
             zero. RESULTS: The observer study did not reveal a
             significant difference in the ability of any radiologist to
             discriminate between real and simulated lesions (P > .31).
             The differences in mean scores for discrimination between
             real and simulated lesions for the three observers were -6,
             9, and -7, respectively. The estimated overall difference
             was -1. CONCLUSION: Mathematic simulation of liver lesions
             is a feasible technique for creating realistic lesions for
             image quality or dose reduction studies in pediatric
             CT.},
   Language = {eng},
   Doi = {10.1148/radiol.2381050477},
   Key = {fds269459}
}

@article{fds269249,
   Author = {Samei, E and Jr, SRS},
   Title = {The nature of the digital image},
   Journal = {Medical physics monograph},
   Number = {30},
   Pages = {103-123},
   Year = {2006},
   ISBN = {1-930524-21-8},
   ISSN = {0163-1802},
   url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000246488500003&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
   Key = {fds269249}
}

@article{fds269282,
   Author = {Bowsher, JE and Yin, F and Chawla, AS and Greer, KL and Jaszczak, RJ and Samei, E and Willett, CG},
   Title = {Combined SPECT/CT imaging onboard radiation-therapy
             machines: A comparison of flat-panel and anger-camera
             systems},
   Journal = {International Journal of Radiation Oncology, Biology,
             Physics},
   Volume = {66},
   Number = {3},
   Pages = {S147-S148},
   Year = {2006},
   ISSN = {0360-3016},
   url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000241221600247&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
   Doi = {10.1016/j.ijrobp.2006.07.297},
   Key = {fds269282}
}

@article{fds269155,
   Author = {Samei, E},
   Title = {Why Medical Image Perception?},
   Journal = {Journal of the American College of Radiology},
   Volume = {3},
   Number = {6},
   Pages = {400-401},
   Year = {2006},
   ISSN = {1546-1440},
   url = {http://dx.doi.org/10.1016/j.jacr.2006.02.017},
   Doi = {10.1016/j.jacr.2006.02.017},
   Key = {fds269155}
}

@article{fds269305,
   Author = {Chawla, AS and Saunders, R and Abbey, C and Delong, D and Samei,
             E},
   Title = {Analyzing the Effect of dose reduction on the detection of
             mammographic lesions using mathematical observer
             models},
   Journal = {Proceedings of SPIE},
   Volume = {6146},
   Year = {2006},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.656378},
   Abstract = {The purpose of this study was to determine the effect of
             dose reduction on the detectability of breast lesions in
             mammograms. Mammograms with dose levels corresponding to 50%
             and 25% of the original clinically-relevant exposure levels
             were simulated. Detection of masses and microcalicifications
             embedded in these mammograms was analyzed by four
             mathematical observer models, namely, the Hotelling
             Observer, Non-prewhitening Matched Filter with Eye Filter
             (NPWE), and Laguerre-Gauss and Gabor Channelized Hotelling
             Observers. Performance was measured in terms of ROC curves
             and Area under ROC Curves (AUC) under Signal Known Exactly
             but Variable Tasks (SKEV) paradigm. Gabor Channelized
             Hotelling Observer predicted deterioration in detectability
             of benign masses. The other algorithmic observers, however,
             did not indicate statistically significant differences in
             the detectability of masses and microcalcifications with
             reduction in dose. Detection of microcalcifications was
             affected more than the detection of masses. Overall, the
             results indicate that there is a potential for reduction of
             radiation dose level in mammographic screening procedures
             without severely compromising the detectability of
             lesions.},
   Doi = {10.1117/12.656378},
   Key = {fds269305}
}

@article{fds269306,
   Author = {Timberg, P and Ruschin, M and Båth, M and Hemdal, B and Andersson, I and Mattsson, S and Chakraborty, D and Saunders, R and Samei, E and Tingberg, A},
   Title = {Potential for lower absorbed dose in digital mammography: A
             JAFROC experiment using clinical hybrid images with
             simulated dose reduction},
   Journal = {Proceedings of SPIE},
   Volume = {6146},
   Year = {2006},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.653419},
   Abstract = {To determine how image quality linked to tumor detection is
             affected by reducing the absorbed dose to 50% and 30% of the
             clinical levels represented by an average glandular dose
             (AGO) level of 1.3 mGy for a standard breast according to
             European guidelines. Materials and methods: 90 normal,
             unprocessed images were acquired from the screening
             department using a full-field digital mammography (FFDM)
             unit Mammomat Novation (Siemens). Into 40 of these, one to
             three simulated tumors were inserted per image at various
             positions. These tumors represented irregular-shaped
             malignant masses. Dose reduction was simulated in all 90
             images by adding simulated quantum noise to represent images
             acquired at 50% and 30% of the original dose, resulting in
             270 images, which were subsequently processed for final
             display. Four radiologists participated in a free-response
             receiver operating characteristics (FROG) study in which
             they searched for and marked suspicious positions of the
             masses as well as rated their degree of suspicion of
             occurrence on a one to four scale. Using the jackknife FROG
             (JAFROC) method, a score between 0 and 1 (where 1 represents
             best performance), referred to as a figure-of-merit (FOM),
             was calculated for each dose level. Results: The FOM was
             0.73, 0.70, and 0.68 for the 100%, 50% and 30% dose levels,
             respectively. Using Analysis of the Variance (ANOVA) to test
             for statistically significant differences between any two of
             the three FOMs revealed that they were not statistically
             distinguishable (p-value of 0.26). Conclusion: For the
             masses used in this experiment, there was no significant
             change in detection by increasing quantum noise, thus
             indicating a potential for dose reduction.},
   Doi = {10.1117/12.653419},
   Key = {fds269306}
}

@article{fds269307,
   Author = {Huda, W and Ogden, KM and Scalzetti, EM and Lavallee, RL and Samei,
             E},
   Title = {X-ray tube voltage and image quality in adult and pediatric
             CT},
   Journal = {Proceedings of SPIE},
   Volume = {6142 II},
   Year = {2006},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.649279},
   Abstract = {The purpose of this study was to investigate how tissue
             x-ray attenuation coefficients, and their uncertainties,
             vary with x-ray tube voltage in different sized patients.
             Anthropomorphic phantoms (newborn, 10 year old, adult) were
             scanned a GE LightSpeed scanner at four x-ray tube voltages.
             Measurements were made of tissue attenuation in the head,
             chest and abdomen regions, as well as the corresponding
             noise values. Tissue signal to noise ratios (SNR) were
             obtained by dividing the average attenuation coefficient by
             the corresponding standard deviation. Soft tissue
             attenuation coefficients, relative to water, showed little
             variation with patient location or x-ray voltage (&lt;
             0.5%), but increasing the x-ray tube voltage from 80 to 140
             kV reduced bone x-ray attenuation by ∼14%. All tissues
             except adult bone showed a reduction of noise with
             increasing x-ray tube voltage (kV); the noise was found to
             be proportional to kV and the average value of n for all
             tissues was -1.19 ±0.57. In pediatric patients at a
             constant x-ray tube voltage, SNR values were approximately
             independent of the body region, but the adult abdomen soft
             tissue SNR values were ∼40% lower than the adult head. SNR
             values in the newborn were more than double the
             corresponding SNR soft tissue values in adults. SNR values
             for lung and bone were generally lower than those for soft
             tissues. For soft tissues, increasing the x-ray tube voltage
             from 80 to 140 kV increased the SNR by an average of ∼90%.
             Data in this paper can be used to help design CT imaging
             protocols that take into account patient size and diagnostic
             imaging task.},
   Doi = {10.1117/12.649279},
   Key = {fds269307}
}

@article{fds269308,
   Author = {Chawla, AS and Samei, E},
   Title = {A method for reduction of eye fatigue by optimizing the
             ambient light conditions in radiology reading
             rooms},
   Journal = {Proceedings of SPIE},
   Volume = {6145},
   Year = {2006},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.655688},
   Abstract = {Ambient lighting in soft-copy reading rooms are currently
             kept at low values to preserve contrast rendition in the
             dark regions of a medical image. Low illuminance levels,
             however, create inadequate viewing conditions and may also
             cause eye-strain. This eye-strain may be attributed to
             notable variations in luminance adaptation state of the
             reader's eyes when moving the gaze intermittently between
             the brighter display and darker surrounding surfaces. This
             paper presents a methodology to optimize the lighting
             conditions of reading rooms to reduce visual fatigue by
             minimizing this variation by exploiting the properties of
             LCDs with low diffuse reflection coefficients and high
             luminance ratio. First, a computational model was developed
             to determine a global luminance adaptation value, L adp,
             when viewing a medical image on display. The model is based
             on the diameter of the pupil size which depends on the
             luminance of the observed object. Second, this value was
             compared with the luminance reflected off surrounding
             surfaces, L s, under various conditions of room illuminance,
             E, different values of diffuse reflection coefficients of
             surrounding surfaces, R s, and calibration settings of a
             typical LCD. The results suggest that for typical luminance
             settings of current LCDs, it is possible to raise ambient
             illumination to minimize differences in eye adaptation,
             potentially reducing visual fatigue while also complying
             with the TG18 specifications for controlled contrast
             rendition. Specifically, room illumination in the 75-150 lux
             range and surface diffuse reflection coefficients in the
             practical range of 0.13-0.22 sr -1 provide an ideal setup
             for typical LCDs. Furthermore, displays with lower diffuse
             reflectivity and with higher inherent luminance ratio than
             currently possible in most LCDs can potentially help further
             decrease eye fatigue, providing an improved ergonomic
             viewing conditions in reading rooms.},
   Doi = {10.1117/12.655688},
   Key = {fds269308}
}

@article{fds269309,
   Author = {Cleland, EW and Samei, E},
   Title = {Performance evaluation of a commercial system for
             quantitative measurement of display resolution},
   Journal = {Proceedings of SPIE},
   Volume = {6141},
   Year = {2006},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.655675},
   Abstract = {One of the key metrics that carry information about image
             quality of medical displays is resolution. Until now, this
             property has been quantitatively assessed in laboratory
             settings. For the first time, a device consisting of a CCD
             camera and analysis software has been made commercially
             available for measuring the resolution of medical displays
             in a clinical setting. This study aimed to evaluate this new
             product in terms of accuracy and precision. In particular,
             attention was paid to determine whether the device is
             appropriate for clinical use. This work involved the
             measurement of the Modulation Transfer Function (MTF) of a
             medical Liquid Crystal Display (LCD) using the
             software/camera system. To check for accuracy, the results
             were compared with published values of the resolution for
             the same display. To assess the system's precision,
             measurements were made multiple times at the same setting.
             The performance of the system was also ascertained as a
             function of the focus setting of the camera. In terms of
             repeatability, the results indicate that when the camera is
             focused within ±0.64 mm of the optimum focus setting, the
             MTF values lie within approximately 14% of the best focus
             MTF at the Nyquist frequency and 11% of the optimum total
             sharpness (JMTF df). Similar results were obtained in the
             horizontal and vertical directions. Also, the MTF results
             track with luminance values as expected. In terms of
             accuracy, the device provides MTF figures within 10% to 20%
             of the previously measured values.},
   Doi = {10.1117/12.655675},
   Key = {fds269309}
}

@article{fds269310,
   Author = {Nasab, NM and Samei, E},
   Title = {The impact of angular separation on the performance of
             biplane correlation imaging for lung nodule
             detection},
   Journal = {Proceedings of SPIE},
   Volume = {6142 I},
   Year = {2006},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.652588},
   Abstract = {In this paper, we evaluate the performance of biplane
             correlation imaging (BCI) using a set of off-angle
             projections acquired from an anthropomorphic chest phantom.
             BCI reduces the effect of anatomical noise, which would
             otherwise impact the detection subtle lesions in planar
             images. BCI also minimizes the number of false positives
             (FPs) when used in conjunction with computer aided diagnosis
             (CAD) applied to a set of coronal chest x-ray projections by
             eliminating non-correlated nodule candidates. In BCI, two
             digital images of the chest are acquired within a short time
             interval from two slightly different posterior projections.
             The image data are then incorporated into the CAD algorithm
             in which nodules are detected by examining the geometrical
             correlation of the detected signals in the two views, thus
             largely "canceling" the impact of anatomical noise.
             Seventy-one low exposure posterior projections were acquired
             of an anthropomorphic chest phantom containing tissue
             equivalent lesions with small angular separations (0.32
             degree) over a range of 20 degrees, [-10°, +10°], along
             the vertical axis. The data were analyzed to determine the
             accuracy of the technique as a function of angular
             separation. The results indicated that the best performance
             was obtained when the angular separation of the projection
             pair was greater than 6 degrees. Within the range of optimum
             angular separation, the number of FPs per image, FPpI, was
             ∼1.1 with average sensitivity around 75% (supported by a
             grant from the NIH R01CA 109074).},
   Doi = {10.1117/12.652588},
   Key = {fds269310}
}

@article{fds269311,
   Author = {Jr, RSS and Samei, E},
   Title = {A Monte Carlo investigation on the impact of scattered
             radiation on mammographic resolution and
             noise},
   Journal = {Proceedings of SPIE},
   Volume = {6142 II},
   Year = {2006},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.653199},
   Abstract = {Scattered radiation plays a significant role in mammographic
             imaging, with scatter fractions over 50% for larger, denser
             breasts. For screen-film systems, scatter primarily affects
             the image contrast, reducing the conspicuity of subtle
             lesions. While digital systems can overcome contrast
             degradation, they remain susceptible to scatter's impact on
             the image resolution and noise. To better understand this
             impact, we have created a Monte Carlo model of a
             mammographic imaging system adaptable for different imaging
             situations. This model flags primary and scatter photons and
             therefore can produce primary-only, scatter-only, or primary
             plus scatter images. Resolution was assessed using the edge
             technique to compute the Modulation Transfer Function (MTF).
             The MTF of a selenium detector imaged with a 28 kVp Mo/Mo
             beam filtered through a 6 cm heterogeneous breast was 0.81,
             0.0002, and 0.65 at 5 mm -1 for the primary beam,
             scatter-only, and primary plus scatter beam, respectively.
             Noise was measured from flat-field images via the noise
             power spectrum (NNPS). The NNPS-exposure product using the
             same imaging conditions was 1.5-10 -5 mm 2·mR, 1.6-10 -5 mm
             2·mR, and 1.9-10 -5 mm 2·mR at 5 mm -1 for the primary,
             scatter, and primary plus scatter beam, respectively. The
             results show that scatter led to a notable low-frequency
             drop in the MTF and an increased magnitude of the
             NNPS-exposure product. (This work was supported in part by
             USAMRMC W81XWH-04-1-0323.).},
   Doi = {10.1117/12.653199},
   Key = {fds269311}
}

@article{fds269312,
   Author = {Borasi, G and Samei, E and Bertolini, M and Nitrosi, A and Tassoni,
             D},
   Title = {Erratum: Contrast-detail analysis of three flat panel
             detectors for digital radiography (Medical Physics (2006)
             33, (1707-1719))},
   Journal = {Medical physics},
   Volume = {33},
   Number = {9},
   Pages = {3580-},
   Year = {2006},
   ISSN = {0094-2405},
   url = {http://dx.doi.org/10.1118/1.2337636},
   Doi = {10.1118/1.2337636},
   Key = {fds269312}
}

@article{fds269313,
   Author = {Jr, RSS and Samei, E},
   Title = {Invited paper: Displaying your health: An overview of
             medical display research},
   Journal = {Proceedings of the Third Americas Display Engineering and
             Applications Conference, ADEAC 2006},
   Volume = {2006},
   Pages = {35-37},
   Year = {2006},
   Abstract = {Medical imaging has been moving from analog technologies
             (such as x-ray film) to digital ones in recent years. The
             quality of a digital image depends on the quality of the
             detector equipment used to capture the image, image
             processing applied to the image, and the medical display
             where the image is viewed. In light of the importance of the
             medical display, medical imaging research has begun to study
             the properties of these devices. This paper will explore
             physical measurements of several medical displays and
             examine how different displays affect diagnostic
             performance. © Copyright 2006 Society for Information
             Display.},
   Key = {fds269313}
}

@article{fds269314,
   Author = {Samei, E},
   Title = {Why Medical Image Perception?},
   Journal = {Journal of the American College of Radiology},
   Volume = {3},
   Number = {6},
   Pages = {400-401},
   Year = {2006},
   ISSN = {1546-1440},
   url = {http://dx.doi.org/10.1016/j.jacr.2006.02.017},
   Doi = {10.1016/j.jacr.2006.02.017},
   Key = {fds269314}
}

@article{fds269315,
   Author = {Roehrig, H and Gaskill, J and Fan, J and Martin, C and Greivenkamp, J and Samei, E},
   Title = {In-field evaluation of the modulation transfer function and
             the signal-to-noise ratio of electronic-display
             devices},
   Journal = {Journal of the Society for Information Display},
   Volume = {14},
   Number = {10},
   Pages = {847-860},
   Year = {2006},
   ISSN = {1071-0922},
   url = {http://dx.doi.org/10.1889/1.2372418},
   Abstract = {This paper describes a charged-coupled device (CCD) camera,
             which was developed for in-field evaluation of the image
             quality of electronic-display devices [such as cathode-ray
             tubes (CRTs) and liquid-crystal displays (LCDs)] used for
             medical applications. Contrary to traditional cameras for
             display-image-quality evaluation, this CCD camera does not
             require a sophisticated x-y-z translation stage for mounting
             and adjustment. Instead, it is handheld and pressed by
             gentle pressure against the display screen. It is controlled
             by a software package which was originally developed for
             display calibration according to the DICOM 14 gray-scale
             standard display function (CSDF).1 This software package
             controls the camera gain when measurements are made at
             different display luminance, display test patterns, performs
             image analysis and displays the results of the measurements
             and calculations. The work concentrated on the measurement
             of modulation transfer function (MTF) and of signal-to-noise
             ratio (SNR) per display pixel. The MTF is derived from the
             Fourier transform of the line spread function (LSF). The
             single-display-pixel SNR is derived from the integration of
             the noise power spectrum (NPS) of a camera image taken of a
             display with a uniform luminance. It is demonstrated that
             the device can produce repeatable results in terms of MTF
             and SNR. MTFs were measured on three monochrome CRTs and
             five monochrome LCDs in order to study repeatability and
             similar quantities. The MTF was measured on a 5-Mpixel LCD
             yielding values that lie within 3.5% of the average MTF at
             the Nyquist frequency and 4.0% of the maximum total
             sharpness (∫ MTF2 df). The MTF was also measured on a
             9-Mpixel LCD, yielding values that lie within 9.0% of the
             average MTF at the Nyquist frequency and 8.0% of the maximum
             total sharpness. The SNR was measured eight times on a
             3-Mpixel monochrome LCD at nine digital driving levels
             (DDLs). At a DDL of 185, the mean SNR was 15.694 and the
             standard deviation (Stdv) was 0.587. At a DDL of 65, the
             mean SNR was 5.675 and Stdv was 0.120. © Copyright 2006
             Society for Information Display.},
   Doi = {10.1889/1.2372418},
   Key = {fds269315}
}

@article{fds269339,
   Author = {Williams, MB and Raghunathan, P and Seibert, A and Kwan, A and Lo, J and Samei, E and Fajardo, L and Maidment, ADA and Yaffe, M and Bloomquist,
             A},
   Title = {Beam optimization for digital mammography -
             II},
   Journal = {Lecture notes in computer science},
   Volume = {4046 LNCS},
   Pages = {273-280},
   Year = {2006},
   ISSN = {0302-9743},
   Abstract = {Optimization of acquisition technique factors (target,
             filter, and kVp) in digital mammography is required for
             maximization of the image SNR, while minimizing patient
             dose. The goal of this study is to compare, for each of the
             major commercially available FFDM systems, the effect of
             various technique factors on image SNR and radiation dose
             for a range of breast thickness and tissue types. This
             phantom study follows the approach of an earlier
             investigation[1], and includes measurements on recent
             versions of two of the FFDM systems discussed in that paper,
             as well as on three FFDM systems not available at that time,
             The five commercial FFDM systems tested are located at five
             different university test sites and include all FFDM systems
             that are currently FDA approved. Performance was assessed
             using 9 different phantom types (three compressed
             thicknesses, and three tissue composition types) using all
             available x-ray target and filter combinations, The figure
             of merit (FOM) used to compare technique factors is the
             ratio of the square of the image SNR to the mean glandular
             dose (MGD). This FOM has been used previously by others in
             mammographic beam optimization studies [2],[3]. For selected
             examples, data are presented describing the change in SNR,
             MOD, and FOM with changing kVp, as well as with changing
             target and/or filter type. For all nine breast types the
             target/filter/kVp combination resulting in the highest FOM
             value is presented. Our results suggest that in general,
             technique combinations resulting in higher energy beams
             resulted in higher FOM values, for nearly all breast types.
             © Springer-Verlag Berlin Heidelberg 2006.},
   Key = {fds269339}
}

@article{fds269360,
   Author = {Nasab, NM and Samei, E and III, JTD},
   Title = {Biplane correlation imaging for lung nodule detection:
             Initial human subject results},
   Journal = {Proceedings of SPIE},
   Volume = {6144 I},
   Year = {2006},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.652582},
   Abstract = {In this paper, we present performance of biplane correlation
             imaging (BCI) on set of chest x-ray projections of human
             data. BCI significantly minimizes the number of false
             positives (FPs) when used in conjunction with computer aided
             detection (CAD) by eliminating non-correlated nodule
             candidates. Sixty-one low exposure posterior projections
             were acquired from more than 20 human subjects with small
             angular separations (0.32 degree) over a range of 20 degrees
             along the vertical axis. All patients were previously
             diagnosed for the presence of lung nodules based on computed
             tomography (CT) examination. Images were processed following
             two steps. First, all images were analyzed using our CAD
             routine for chest radiography. This process proceeded with a
             BCI processing in which the results of CAD on each single
             projection were examined in terms of their geometrical
             correlation with those found in the other 60 projections
             based on the predetermined shift of possible nodule
             locations in each projection. The suspect entities with a
             geometrical correlation that coincided with the known
             location of the lesions were selected as nodules; otherwise
             they were ignored. An expert radiologist with reference to
             the associated CT dataset determined the truth regarding
             nodule location and sizes, which were then used to determine
             if the found nodules are true positive or false positive.
             The preliminary results indicated that the best performance
             was obtained when the angular separation of the projection
             pair was greater than about 6.7 degrees. Within the range of
             optimum angular separation, the number of FPs per image was
             0-1 without impacting the number of true positives (TPs),
             averaged around 92%. (Supported by grants from the NIH:
             R01-CA80490 and R01CA109074).},
   Doi = {10.1117/12.652582},
   Key = {fds269360}
}

@article{fds269367,
   Author = {Madhav, P and McKinley, RL and Samei, E and Bowsher, JE and Tornai,
             MP},
   Title = {A novel method to characterize the MTF in 3D for computed
             mammotomography},
   Journal = {Proceedings of SPIE},
   Volume = {6142 II},
   Year = {2006},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.653393},
   Abstract = {A novel phantom has been developed to measure the modulation
             transfer function (MTF) in 3D for x-ray computed tomography.
             The phantom consists of three tungsten wires, positioned
             nearly orthogonal to each other. Simultaneous measurements
             of the MTF are taken at various locations along the three
             orthogonal reconstructed planes. Our computed
             mammotomography (CmT) system uses a Varian Paxscan 2520
             digital x-ray detector which can be positioned anywhere in
             ∼2pi steradian band and can have arbitrary trajectories,
             With a half-cone beam geometry and with the phantom
             positioned near the center of rotation, projection images
             are acquired over 360 degrees, Various 3D orbits are
             evaluated including vertical axis of rotation and saddle.
             Reconstructions were performed using an iterative
             ordered-subsets transmission algorithm on rebinned
             projection images, using various numbers of iterations.
             Rotation of reconstructed slices isolated each wire into its
             own plane. At various locations along the length of each
             wire, corresponding MTFs were calculated from 1D line spread
             functions. Through measurement, accuracy of wire method was
             verified by comparison of the projection MTFs computed from
             a wire and a standard edge device. Results indicated minor
             variations in MTF among the three orthogonal planes, which
             imply a high degree of uniform sampling in the imaged
             volume. Findings indicate that the phantom can be used to
             assess the intrinsic image resolution in 3D as well as
             potential degradative effects of measurements in various
             media.},
   Doi = {10.1117/12.653393},
   Key = {fds269367}
}

@article{fds269381,
   Author = {Fetterly, KA and Samei, E},
   Title = {A photographic technique for assessing the viewing-angle
             performance of liquid-crystal displays},
   Journal = {Journal of the Society for Information Display},
   Volume = {14},
   Number = {10},
   Pages = {867-872},
   Year = {2006},
   ISSN = {1071-0922},
   url = {http://dx.doi.org/10.1889/1.2372420},
   Abstract = {Liquid-crystal displays (LCDs) have notable variation in
             luminance and perceived contrast as a function of the angle
             from which they are viewed. Though this is an important
             performance issue for LCDs, most evaluation techniques for
             assessing this variation have been limited to laboratory
             settings. This study demonstrates the use of a photographic
             technique for such an evaluation. The technique is based on
             an actively cooled charge-coupled-device (CCD) detector in
             combination with a macro lens covering a circular angular
             range (8) of ±42.5°. The camera was used to evaluate the
             luminance and perceived contrast properties of an LCD.
             Uniform field images corresponding to 17 equally spaced
             gray-scale values in the digital driving level (DDL) range
             of the display system were acquired. The 12-bit gray-scale
             digital images produced by the camera were converted to
             luminance units (cd/m2) via the measured luminance vs. DDL
             response function of the camera. The changes in perceived
             contrast as a function of viewing angle were derived from
             the Barten model of the gray-scale response of the
             human-visual system using the methods proposed by the AAPM
             TC18 Report. The results of this photographic technique were
             compared to measurements acquired from a similar display
             using a Fourier-optics-based luminance meter. The results of
             the two methods generally agreed to within 5%. The
             photographic methods used were found to be accurate and
             robust for in-field assessment of the angular response of
             LCDs over the FOV of the camera. © Copyright 2006 Society
             for Information Display.},
   Doi = {10.1889/1.2372420},
   Key = {fds269381}
}

@article{fds269382,
   Author = {Samei, E and Cleland, E and Roehrig, H},
   Title = {In-field assessment of display resolution and noise:
             Performance evaluation of a commercial measurement
             system},
   Journal = {Journal of the Society for Information Display},
   Volume = {14},
   Number = {10},
   Pages = {839-845},
   Year = {2006},
   ISSN = {1071-0922},
   url = {http://dx.doi.org/10.1889/1.2372417},
   Abstract = {Two key metrics of image quality for high-fidelity displays,
             including medical displays, are resolution and noise. Until
             now, these properties have been primarily measured in
             laboratory settings. For the first time, a system consisting
             of a CCD camera and analysis software has been made
             commercially available for measuring the resolution and
             noise of medical displays in a clinical setting. This study
             aimed at evaluating this new product in terms of accuracy
             and precision. In particular, the project involved the
             measurement of the modulation transfer function (MTF) and
             the signal-to-noise ratio (SNR) of two medical imaging
             displays, one cathode-ray tube (CRT) display and one
             liquid-crystal display (LCD) using this camera/software
             system. To assess the system's precision, measurements were
             made multiple times at the same setting. To check for
             accuracy, the results were compared with published values of
             the MTF and noise for the same displays. The performance of
             the system was also ascertained as a function of the focus
             setting of the camera. The results indicated that for the
             LCD, when the camera is focused within ±0.6 mm of the
             optimum focus setting, the MTF values lie within
             approximately 14% of the best focus MTF at the Nyquist
             frequency and 11 % of the optimum overall sharpness (∫
             MTF2 df). Similar results were obtained in the horizontal
             and vertical directions. For the CRT, this focus produced
             vertical and horizontal MTF values at the Nyquist frequency
             within 15.2% and 61.2% of the optimum focus MTF,
             respectively. The figures in terms of overall sharpness were
             3.0% and 0.7%. The results for the noise measurements showed
             a repeatability of 3% for the LCD and 13% for the CRT and a
             relative (but not absolute) magnitude of the noise between
             the two displays reflective of prior measurements. Overall,
             the measurement system yielded reasonably precise resolution
             and noise results for both display devices. The accuracy was
             traceable to published results only for the MTF and for
             relative level of display noise with differences in the
             absolute magnitude of noise between current and prior
             measurements attributed to variations in the non-standard
             techniques applied for display noise measurements. ©
             Copyright 2006 Society for Information Display.},
   Doi = {10.1889/1.2372417},
   Key = {fds269382}
}

@article{fds269447,
   Author = {Siegel, E and Krupinski, E and Samei, E and Flynn, M and Andriole, K and Erickson, B and Thomas, J and Badano, A and Seibert, JA and Pisano,
             ED},
   Title = {Digital Mammography Image Quality: Image
             Display},
   Journal = {Journal of the American College of Radiology},
   Volume = {3},
   Number = {8},
   Pages = {615-627},
   Publisher = {Elsevier},
   Year = {2006},
   ISSN = {1546-1440},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/17412136},
   Keywords = {Breast Neoplasms • Data Display • Female •
             Humans • Image Interpretation, Computer-Assisted •
             Mammography • Radiographic Image Enhancement •
             Radiology Information Systems • diagnosis* •
             instrumentation • standards*},
   Abstract = {This paper on digital mammography image display is 1 of 3
             papers written as part of an intersociety effort to
             establish image quality standards for digital mammography.
             The information included in this paper is intended to
             support the development of an American College of Radiology
             (ACR) guideline on image quality for digital mammography.
             The topics of the other 2 papers are digital mammography
             image acquisition and digital mammography image storage,
             transmission, and retrieval. The societies represented in
             compiling this document were the Radiological Society of
             North America, the ACR, the American Association of
             Physicists in Medicine, and the Society for Computer
             Applications in Radiology. These papers describe in detail
             what is known to improve image quality for digital
             mammography and make recommendations about how digital
             mammography should be performed to optimize the
             visualization of breast cancers using this imaging tool.
             Through the publication of these papers, the ACR is seeking
             input from industry, radiologists, and other interested
             parties on their contents so that the final ACR guideline
             for digital mammography will represent the consensus of the
             broader community interested in these topics. © 2006
             American College of Radiology.},
   Language = {eng},
   Doi = {10.1016/j.jacr.2006.03.007},
   Key = {fds269447}
}

@article{fds269465,
   Author = {McKinley, RL and Tornai, MP and Brzymialkiewicz, C and Madhav, P and Samei, E and Bowsher, JE},
   Title = {Analysis of a novel offset cone-beam computed
             mammotomography system geometry for accomodating various
             breast sizes.},
   Journal = {Physica Medica},
   Volume = {21 Suppl 1},
   Pages = {48-55},
   Year = {2006},
   ISSN = {1120-1797},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/17645994},
   Abstract = {We evaluate a newly developed dedicated cone-beam
             transmission computed mammotomography (CmT) system
             configuration using an optimized quasi-monochromatic cone
             beam technique for attenuation correction of SPECT in a
             planned dual-modality emission and transmission system for
             pendant, uncompressed breasts. In this study, we perform
             initial CmT acquisitions using various sized breast phantoms
             to evaluate an offset cone-beam geometry. This offset
             geometry provides conjugate projections through a full 360
             degree gantry rotation, and thus yields a greatly increased
             effective field of view, allowing a much wider range of
             breast sizes to be imaged without truncation in
             reconstructed images. Using a tungsten X-ray tube and
             digital flat-panel X-ray detector in a compact geometry, we
             obtained initial CmT scans without shift and with the offset
             geometry, using geometrical frequency/resolution phantoms
             and two different sizes of breast phantoms. Acquired data
             were reconstructed using an ordered subsets transmission
             iterative algorithm. Projection images indicate that the
             larger, 20 cm wide, breast requires use of a half-cone-beam
             offset scan to eliminate truncation artifacts. Reconstructed
             image results illustrate elimination of truncation
             artifacts, and that the novel quasi-monochromatic beam
             yields reduced beam hardening. The offset geometry CmT
             system can indeed potentially be used for structural imaging
             and accurate attenuation correction for the functional
             dedicated breast SPECT system.},
   Language = {eng},
   Doi = {10.1016/S1120-1797(06)80024-4},
   Key = {fds269465}
}

@article{fds269247,
   Author = {McKinley, RL and Tornai, MP and Samei, E and Bradshaw,
             ML},
   Title = {Initial study of quasi-monochromatic X-ray beam performance
             for X-ray computed mammotomography},
   Journal = {IEEE Transactions on Nuclear Science},
   Volume = {52},
   Number = {5},
   Pages = {1243-1250},
   Year = {2005},
   Month = {October},
   ISSN = {0018-9499},
   url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000233780800003&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
   Doi = {10.1109/TNS.2005.0857629},
   Key = {fds269247}
}

@article{fds132496,
   Author = {E Samei and E Buhr and P Granfors and D Vandenbroucke and X
             Wang},
   Title = {Comparison of edge analysis techniques for the determination
             of the MTF of digital radiographic systems.},
   Journal = {Physics in medicine and biology},
   Volume = {50},
   Number = {15},
   Pages = {3613-25},
   Year = {2005},
   Month = {August},
   ISSN = {0031-9155},
   url = {http://dx.doi.org/10.1088/0031-9155/50/15/009},
   Keywords = {Algorithms* • Equipment Failure Analysis • Pattern
             Recognition, Automated • Phantoms, Imaging •
             Quality Assurance, Health Care • Radiographic Image
             Enhancement • Radiographic Image Interpretation,
             Computer-Assisted • Reproducibility of Results •
             Sensitivity and Specificity • instrumentation •
             instrumentation* • methods* • standards},
   Abstract = {The modulation transfer function (MTF) is well established
             as a metric to characterize the resolution performance of a
             digital radiographic system. Implemented by various
             laboratories, the edge technique is currently the most
             widespread approach to measure the MTF. However, there can
             be differences in the results attributed to differences in
             the analysis technique employed. The objective of this study
             was to determine whether comparable results can be obtained
             from different algorithms processing identical images
             representative of those of current digital radiographic
             systems. Five laboratories participated in a round-robin
             evaluation of six different algorithms including one
             prescribed in the International Electrotechnical Commission
             (IEC) 62220-1 standard. The algorithms were applied to two
             synthetic and 12 real edge images from different digital
             radiographic systems including CR, and direct- and
             indirect-conversion detector systems. The results were
             analysed in terms of variability as well as accuracy of the
             resulting presampled MTFs. The results indicated that
             differences between the individual MTFs and the mean MTF
             were largely below 0.02. In the case of the two simulated
             edge images, all algorithms yielded similar results within
             0.01 of the expected true MTF. The findings indicated that
             all algorithms tested in this round-robin evaluation,
             including the IEC-prescribed algorithm, were suitable for
             accurate MTF determination from edge images, provided the
             images are not excessively noisy. The agreement of the MTF
             results was judged sufficient for the measurement of the MTF
             necessary for the determination of the DQE.},
   Language = {eng},
   Doi = {10.1088/0031-9155/50/15/009},
   Key = {fds132496}
}

@article{fds328145,
   Author = {Ranger, NT and Samei, E and Dobbins, JT and Ravin,
             CE},
   Title = {Measurement of the detective quantum efficiency in digital
             detectors consistent with the IEC 62220-1 standard:
             Practical considerations regarding the choice of filter
             material.},
   Journal = {Medical physics},
   Volume = {32},
   Number = {7Part1},
   Pages = {2305-2311},
   Year = {2005},
   Month = {July},
   ISSN = {0094-2405},
   url = {http://dx.doi.org/10.1118/1.1929187},
   Keywords = {Equipment Failure Analysis • Filtration •
             Guidelines as Topic • Internationality • Quality
             Assurance, Health Care • Quantum Theory •
             Radiographic Image Enhancement • Reference Standards
             • Reproducibility of Results • Sensitivity and
             Specificity • Technology Assessment, Biomedical •
             Transducers* • X-Ray Intensifying Screens •
             instrumentation* • methods • standards •
             standards*},
   Abstract = {As part of a larger evaluation we attempted to measure the
             detective quantum efficiency (DQE) of an amorphous silicon
             flat-panel detector using the method described in the
             International Electrotechnical Commission standard 62220-1
             published in October 2003. To achieve the radiographic beam
             conditions specified in the standard, we purchased
             scientific-grade ultrahigh purity aluminum (99.999% purity,
             type-11999 alloy) filters in thicknesses ranging from 0.1
             through 10.0 mm from a well-known, specialty metals
             supplier. Qualitative evaluation of flat field images
             acquired at 71 kV (RQA5 beam quality) with 21 mm of
             ultrahigh purity aluminum filtration demonstrated a low
             frequency mottle that was reproducible and was not observed
             when the measurement was repeated at 74 kV (RQA5 beam
             quality) with 21 mm of lower-purity aluminum (99.0% purity,
             type-1100 alloy) filtration. This finding was ultimately
             attributed to the larger grain size (approximately 1-2 mm)
             of high purity aluminum metal, which is a well-known
             characteristic, particularly in thicknesses greater than 1
             mm. The impact of this low frequency mottle is to
             significantly overestimate the noise power spectrum (NPS) at
             spatial frequencies ⩽0.2mm-1, which in turn would cause an
             underestimation of the DQE in this range. A subsequent
             evaluation of ultrahigh purity aluminum, purchased from a
             second source, suggests, that reduced grain size can be
             achieved by the process of annealing. Images acquired with
             this sample demonstrated vertical striated nonuniformities
             that are attributed to the manufacturing method and which do
             not appear to appreciably impact the NPS at spatial
             frequencies ⩾0.5mm-1, but do result in an asymmetry in the
             x- and y-NPS at spatial frequencies ⩽0.2mm-1. Our
             observations of markedly visible nonuniformities in images
             acquired with high purity aluminum filtration suggest that
             the uniformity of filter materials should be carefully
             evaluated and taken into consideration when measuring the
             DQE.},
   Language = {eng},
   Doi = {10.1118/1.1929187},
   Key = {fds328145}
}

@article{fds269260,
   Author = {Samei, E},
   Title = {Display evaluation demonstration workshop},
   Journal = {Medical physics},
   Volume = {32},
   Number = {6},
   Pages = {2063-2063},
   Year = {2005},
   Month = {June},
   ISSN = {0094-2405},
   url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000229908601191&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
   Doi = {10.1118/1.1998280},
   Key = {fds269260}
}

@article{fds269266,
   Author = {Samei, E},
   Title = {Display evaluation demonstration workshop},
   Journal = {Medical physics},
   Volume = {32},
   Number = {6},
   Pages = {2073-2073},
   Year = {2005},
   Month = {June},
   ISSN = {0094-2405},
   url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000229908601224&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
   Doi = {10.1118/1.1998315},
   Key = {fds269266}
}

@article{fds269269,
   Author = {Krupinski, E and Samei, E and Eckstein, M},
   Title = {Advances in perception & visualization},
   Journal = {Medical physics},
   Volume = {32},
   Number = {6},
   Pages = {2142-2142},
   Year = {2005},
   Month = {June},
   ISSN = {0094-2405},
   url = {http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000229908601491&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=47d3190e77e5a3a53558812f597b0b92},
   Doi = {10.1118/1.1999741},
   Key = {fds269269}
}

@article{fds132487,
   Author = {E Samei and JY Lo and TT Yoshizumi and JL Jesneck and JT Dobbins 3rd and CE
             Floyd Jr and HP McAdams and CE Ravin},
   Title = {Comparative scatter and dose performance of slot-scan and
             full-field digital chest radiography systems.},
   Journal = {Radiology},
   Volume = {235},
   Number = {3},
   Pages = {940-9},
   Year = {2005},
   Month = {June},
   ISSN = {0033-8419},
   url = {http://dx.doi.org/10.1148/radiol.2353040516},
   Keywords = {Phantoms, Imaging • Radiation Dosage •
             Radiographic Image Enhancement* • Radiography, Thoracic
             • methods • standards*},
   Abstract = {OBJECTIVE: To evaluate the scatter, dose, and effective
             detective quantum efficiency (DQE) performance of a
             slot-scan digital chest radiography system compared with
             that of a full-field digital radiography system. METHODS:
             Scatter fraction of a slot-scan system was measured for an
             anthropomorphic and a geometric phantom by using a posterior
             beam-stop technique at 117 and 140 kVp. Measurements were
             repeated with a full-field digital radiography system with
             and without a 13:1 antiscatter grid at 120 and 140 kVp. For
             both systems, the effective dose was measured on
             posteroanterior and lateral views for standard clinical
             techniques by using dosimeters embedded in a female phantom.
             The effective DQEs of the two systems were assessed by
             taking into account the scatter performance and the DQE of
             each system. The statistical significance of all the
             comparative differences was ascertained by means of t test
             analysis. RESULTS: The slot-scan system and the full-field
             system with grid yielded scatter fractions of 0.13-0.14 and
             0.42-0.48 in the lungs and 0.30-0.43 and 0.69-0.78 in the
             mediastinum, respectively. The sum of the effective doses
             for posteroanterior and lateral views for the slot-scan
             system (0.057 mSv +/- 0.003 [+/- standard deviation]) was
             34% lower than that for the full-field system (0.086 mSv +/-
             0.001, P < .05) at their respective clinical peak voltages
             (140 and 120 kVp, respectively). The effective DQE of the
             slot-scan system was equivalent to that of the full-field
             system in the lung region but was 37% higher in the dense
             regions (P < .05). CONCLUSIONS: The slot-scan design leads
             to marked scatter reduction compared with the more
             conventional full-field geometries with a grid. The improved
             scatter performance of a slot-scan geometry can effectively
             compensate for low DQE and lead to improved image
             quality.},
   Language = {eng},
   Doi = {10.1148/radiol.2353040516},
   Key = {fds132487}
}

@article{fds269482,
   Author = {Samei, E and Badano, A and Chakraborty, D and Compton, K and Cornelius,
             C and Corrigan, K and Flynn, MJ and Hemminger, B and Hangiandreou, N and Johnson, J and Moxley-Stevens, DM and Pavlicek, W and Roehrig, H and Rutz, L and Shepard, J and Uzenoff, RA and Wang, J and Willis, CE and AAPM
             TG18},
   Title = {Assessment of display performance for medical imaging
             systems: executive summary of AAPM TG18 report.},
   Journal = {Medical physics},
   Volume = {32},
   Number = {4},
   Pages = {1205-1225},
   Year = {2005},
   Month = {April},
   ISSN = {0094-2405},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/15895604},
   Abstract = {Digital imaging provides an effective means to
             electronically acquire, archive, distribute, and view
             medical images. Medical imaging display stations are an
             integral part of these operations. Therefore, it is vitally
             important to assure that electronic display devices do not
             compromise image quality and ultimately patient care. The
             AAPM Task Group 18 (TG18) recently published guidelines and
             acceptance criteria for acceptance testing and quality
             control of medical display devices. This paper is an
             executive summary of the TG18 report. TG18 guidelines
             include visual, quantitative, and advanced testing
             methodologies for primary and secondary class display
             devices. The characteristics, tested in conjunction with
             specially designed test patterns (i.e., TG18 patterns),
             include reflection, geometric distortion, luminance, the
             spatial and angular dependencies of luminance, resolution,
             noise, glare, chromaticity, and display artifacts. Geometric
             distortions are evaluated by linear measurements of the
             TG18-QC test pattern, which should render distortion
             coefficients less than 2%/5% for primary/secondary displays,
             respectively. Reflection measurements include specular and
             diffuse reflection coefficients from which the maximum
             allowable ambient lighting is determined such that contrast
             degradation due to display reflection remains below a 20%
             limit and the level of ambient luminance (Lamb) does not
             unduly compromise luminance ratio (LR) and contrast at low
             luminance levels. Luminance evaluation relies on visual
             assessment of low contrast features in the TG18-CT and
             TG18-MP test patterns, or quantitative measurements at 18
             distinct luminance levels of the TG18-LN test patterns. The
             major acceptable criteria for primary/ secondary displays
             are maximum luminance of greater than 170/100 cd/m2, LR of
             greater than 250/100, and contrast conformance to that of
             the grayscale standard display function (GSDF) of better
             than 10%/20%, respectively. The angular response is tested
             to ascertain the viewing cone within which contrast
             conformance to the GSDF is better than 30%/60% and LR is
             greater than 175/70 for primary/secondary displays, or
             alternatively, within which the on-axis contrast thresholds
             of the TG18-CT test pattern remain discernible. The
             evaluation of luminance spatial uniformity at two distinct
             luminance levels across the display faceplate using TG18-UNL
             test patterns should yield nonuniformity coefficients
             smaller than 30%. The resolution evaluation includes the
             visual scoring of the CX test target in the TG18-QC or
             TG18-CX test patterns, which should yield scores greater
             than 4/6 for primary/secondary displays. Noise evaluation
             includes visual evaluation of the contrast threshold in the
             TG18-AFC test pattern, which should yield a minimum of 3/2
             targets visible for primary/secondary displays. The
             guidelines also include methodologies for more quantitative
             resolution and noise measurements based on MTF and NPS
             analyses. The display glare test, based on the visibility of
             the low-contrast targets of the TG18-GV test pattern or the
             measurement of the glare ratio (GR), is expected to yield
             scores greater than 3/1 and GRs greater than 400/150 for
             primary/secondary displays. Chromaticity, measured across a
             display faceplate or between two display devices, is
             expected to render a u',v' color separation of less than
             0.01 for primary displays. The report offers further
             descriptions of prior standardization efforts, current
             display technologies, testing prerequisites, streamlined
             procedures and timelines, and TG18 test patterns.},
   Doi = {10.1118/1.1861159},
   Key = {fds269482}
}

@article{fds132495,
   Author = {E Samei and A Badano and D Chakraborty and K Compton and C Cornelius and K
             Corrigan, MJ Flynn and B Hemminger and N Hangiandreou and J Johnson and DM Moxley-Stevens and W Pavlicek and H Roehrig and L Rutz and J Shepard and RA Uzenoff and J Wang and CE Willis and AAPM TG18},
   Title = {Assessment of display performance for medical imaging
             systems: executive summary of AAPM TG18 report.},
   Journal = {Medical physics},
   Volume = {32},
   Number = {4},
   Pages = {1205-25},
   Year = {2005},
   Month = {April},
   ISSN = {0094-2405},
   Keywords = {Computer Graphics • Computer Terminals •
             Diagnostic Imaging • Guidelines as Topic • Humans
             • Quality Control • Radiographic Image Enhancement
             • Radiology Information Systems • Reference
             Standards • Signal Processing, Computer-Assisted •
             Software • User-Computer Interface •
             instrumentation* • methods* • standards •
             standards*},
   Abstract = {Digital imaging provides an effective means to
             electronically acquire, archive, distribute, and view
             medical images. Medical imaging display stations are an
             integral part of these operations. Therefore, it is vitally
             important to assure that electronic display devices do not
             compromise image quality and ultimately patient care. The
             AAPM Task Group 18 (TG18) recently published guidelines and
             acceptance criteria for acceptance testing and quality
             control of medical display devices. This paper is an
             executive summary of the TG18 report. TG18 guidelines
             include visual, quantitative, and advanced testing
             methodologies for primary and secondary class display
             devices. The characteristics, tested in conjunction with
             specially designed test patterns (i.e., TG18 patterns),
             include reflection, geometric distortion, luminance, the
             spatial and angular dependencies of luminance, resolution,
             noise, glare, chromaticity, and display artifacts. Geometric
             distortions are evaluated by linear measurements of the
             TG18-QC test pattern, which should render distortion
             coefficients less than 2%/5% for primary/secondary displays,
             respectively. Reflection measurements include specular and
             diffuse reflection coefficients from which the maximum
             allowable ambient lighting is determined such that contrast
             degradation due to display reflection remains below a 20%
             limit and the level of ambient luminance (Lamb) does not
             unduly compromise luminance ratio (LR) and contrast at low
             luminance levels. Luminance evaluation relies on visual
             assessment of low contrast features in the TG18-CT and
             TG18-MP test patterns, or quantitative measurements at 18
             distinct luminance levels of the TG18-LN test patterns. The
             major acceptable criteria for primary/ secondary displays
             are maximum luminance of greater than 170/100 cd/m2, LR of
             greater than 250/100, and contrast conformance to that of
             the grayscale standard display function (GSDF) of better
             than 10%/20%, respectively. The angular response is tested
             to ascertain the viewing cone within which contrast
             conformance to the GSDF is better than 30%/60% and LR is
             greater than 175/70 for primary/secondary displays, or
             alternatively, within which the on-axis contrast thresholds
             of the TG18-CT test pattern remain discernible. The
             evaluation of luminance spatial uniformity at two distinct
             luminance levels across the display faceplate using TG18-UNL
             test patterns should yield nonuniformity coefficients
             smaller than 30%. The resolution evaluation includes the
             visual scoring of the CX test target in the TG18-QC or
             TG18-CX test patterns, which should yield scores greater
             than 4/6 for primary/secondary displays. Noise evaluation
             includes visual evaluation of the contrast threshold in the
             TG18-AFC test pattern, which should yield a minimum of 3/2
             targets visible for primary/secondary displays. The
             guidelines also include methodologies for more quantitative
             resolution and noise measurements based on MTF and NPS
             analyses. The display glare test, based on the visibility of
             the low-contrast targets of the TG18-GV test pattern or the
             measurement of the glare ratio (GR), is expected to yield
             scores greater than 3/1 and GRs greater than 400/150 for
             primary/secondary displays. Chromaticity, measured across a
             display faceplate or between two display devices, is
             expected to render a u',v' color separation of less than
             0.01 for primary displays. The report offers further
             descriptions of prior standardization efforts, current
             display technologies, testing prerequisites, streamlined
             procedures and timelines, and TG18 test patterns.},
   Language = {eng},
   Key = {fds132495}
}

@article{fds269460,
   Author = {Samei, E},
   Title = {AAPM/RSNA physics tutorial for residents: technological and
             psychophysical considerations for digital mammographic
             displays.},
   Journal = {Radiographics : a review publication of the Radiological
             Society of North America, Inc},
   Volume = {25},
   Number = {2},
   Pages = {491-501},
   Year = {2005},
   Month = {March},
   ISSN = {1527-1323},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/15798066},
   Keywords = {Artifacts • Mammography • Psychophysics •
             instrumentation* • methods*},
   Abstract = {Digital mammography is gradually replacing screen-film
             analog mammography, a transition driven by a desire to
             improve the efficiency and possibly the quality of the
             interpretation of mammograms. Digital mammography involves
             the use of electronic display devices to display the
             mammograms. Currently, two electronic technologies are used
             to display digital mammograms: the cathode-ray tube (CRT)
             and liquid crystal display (LCD). CRT and LCD devices have
             imaging characteristics markedly different from those of
             transilluminated film, which has conventionally been used to
             display analog mammograms. Consequently, the transition to
             digital mammography necessitates consideration of a number
             of psychophysical factors pertaining to effective display of
             mammograms. Some of these factors are related to specific
             performance characteristics of the display devices, whereas
             others are related to inherent characteristics of the human
             visual system. The main psychophysical factors that affect
             the interpretation of medical images are contrast,
             resolution, and noise. Optimal display of mammograms is
             achieved by taking these factors into consideration and by
             using time-efficient, intuitive, and reader-specific user
             interfaces. Because display devices are susceptible to
             variations in hardware and calibration and to degradation
             over time, acceptance testing and quality control testing
             are necessary to maintain an adequate level of display
             quality.},
   Language = {eng},
   Doi = {10.1148/rg.252045185},
   Key = {fds269460}
}

@booklet{Saunders05,
   Author = {Saunders, RS and Samei, E and Jesneck, JL and Lo,
             JY},
   Title = {Physical characterization of a prototype selenium-based full
             field digital mammography detector.},
   Journal = {Medical physics},
   Volume = {32},
   Number = {2},
   Pages = {588-599},
   Year = {2005},
   Month = {February},
   ISSN = {0094-2405},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/15789606},
   Abstract = {The purpose of this study was to measure experimentally the
             physical performance of a prototype mammographic imager
             based on a direct detection, flat-panel array design
             employing an amorphous selenium converter with 70 microm
             pixels. The system was characterized for two different anode
             types, a molybdenum target with molybdenum filtration
             (Mo/Mo) and a tungsten target with rhodium filtration
             (W/Rh), at two different energies, 28 and 35 kVp, with
             approximately 2 mm added aluminum filtration. To measure the
             resolution, the presampled modulation transfer function
             (MTF) was measured using an edge method. The normalized
             noise power spectrum (NNPS) was measured by two-dimensional
             Fourier analysis of uniformly exposed mammograms. The
             detective quantum efficiencies (DQEs) were computed from the
             MTFs, the NNPSs, and theoretical ideal signal to noise
             ratios. The MTF was found to be close to its ideal limit and
             reached 0.2 at 11.8 mm(-1) and 0.1 at 14.1 mm(-1) for images
             acquired at an RQA-M2 technique (Mo/Mo anode, 28 kVp, 2 mm
             Al). Using a tungsten technique (MW2; W/Rh anode, 28 kVp, 2
             mm Al), the MTF went to 0.2 at 11.2 mm(-1) and to 0.1 at
             13.3 mm(-1). The DQE reached a maximum value of 54% at 1.35
             mm(-1) for the RQA-M2 technique at 1.6 microC/kg and
             achieved a peak value of 64% at 1.75 mm(-1) for the tungsten
             technique (MW2) at 1.9 microC/kg. Nevertheless, the DQE
             showed strong exposure and frequency dependencies. The
             results indicated that the detector offered high MTFs and
             DQEs, but structured noise effects may require improved
             calibration before clinical implementation.},
   Doi = {10.1118/1.1855033},
   Key = {Saunders05}
}

@article{fds132491,
   Author = {RS Saunders Jr and E Samei and JL Jesneck and JY Lo},
   Title = {Physical characterization of a prototype selenium-based full
             field digital mammography detector.},
   Journal = {Medical physics},
   Volume = {32},
   Number = {2},
   Pages = {588-99},
   Year = {2005},
   Month = {February},
   ISSN = {0094-2405},
   Keywords = {Equipment Design • Equipment Failure Analysis •
             Feasibility Studies • Mammography • Phantoms,
             Imaging • Pilot Projects • Radiation Dosage •
             Radiographic Image Enhancement • Radiometry •
             Selenium • Signal Processing, Computer-Assisted •
             Transducers • X-Ray Intensifying Screens* •
             chemistry* • instrumentation* • methods •
             radiation effects*},
   Abstract = {The purpose of this study was to measure experimentally the
             physical performance of a prototype mammographic imager
             based on a direct detection, flat-panel array design
             employing an amorphous selenium converter with 70 microm
             pixels. The system was characterized for two different anode
             types, a molybdenum target with molybdenum filtration
             (Mo/Mo) and a tungsten target with rhodium filtration
             (W/Rh), at two different energies, 28 and 35 kVp, with
             approximately 2 mm added aluminum filtration. To measure the
             resolution, the presampled modulation transfer function
             (MTF) was measured using an edge method. The normalized
             noise power spectrum (NNPS) was measured by two-dimensional
             Fourier analysis of uniformly exposed mammograms. The
             detective quantum efficiencies (DQEs) were computed from the
             MTFs, the NNPSs, and theoretical ideal signal to noise
             ratios. The MTF was found to be close to its ideal limit and
             reached 0.2 at 11.8 mm(-1) and 0.1 at 14.1 mm(-1) for images
             acquired at an RQA-M2 technique (Mo/Mo anode, 28 kVp, 2 mm
             Al). Using a tungsten technique (MW2; W/Rh anode, 28 kVp, 2
             mm Al), the MTF went to 0.2 at 11.2 mm(-1) and to 0.1 at
             13.3 mm(-1). The DQE reached a maximum value of 54% at 1.35
             mm(-1) for the RQA-M2 technique at 1.6 microC/kg and
             achieved a peak value of 64% at 1.75 mm(-1) for the tungsten
             technique (MW2) at 1.9 microC/kg. Nevertheless, the DQE
             showed strong exposure and frequency dependencies. The
             results indicated that the detector offered high MTFs and
             DQEs, but structured noise effects may require improved
             calibration before clinical implementation.},
   Language = {eng},
   Key = {fds132491}
}

@article{fds37902,
   Author = {R.S. Saunders and E. Samei and J. Johnson and J.A.
             Baker},
   Title = {Effect of display resolution on the detection of
             mammographic lesions},
   Volume = {5749},
   Pages = {243-250},
   Booktitle = {Proc. SPIE Medical Imaging},
   Year = {2005},
   Key = {fds37902}
}

@article{fds37907,
   Author = {R.L. McKinley and M.P. Tornai and C.N. Brzymialkiewicz and E.
             Samei},
   Title = {Investigation of cone-beam acquisitions implemented using a
             novel dedicated mammotomography system with unique arbitrary
             orbit capability},
   Booktitle = {Proc. SPIE},
   Year = {2005},
   Key = {fds37907}
}

@article{fds269366,
   Author = {Tornai, MP and McKinley, RL and Brzymialkiewicz, CN and Madhav, P and Cutler, SJ and Crotty, DJ and Bowsher, JE and Samei, E and Jr,
             CEF},
   Title = {Design and development of a fully-3D dedicated x-ray
             computed mammotomography system},
   Journal = {Proceedings of SPIE},
   Volume = {5745},
   Number = {I},
   Pages = {189-197},
   Booktitle = {Proc. SPIE},
   Year = {2005},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.595636},
   Abstract = {Our effort to implement a volumetric x-ray computed
             mammotomography (CmT) system dedicated to imaging breast
             disease comprises: demonstrated development of a
             quasi-monochromatic x-ray beam providing minimal dose and
             other optimal imaging figures of merit; new development of a
             compact, variable field-of-view, fully-3D acquisition gantry
             with a digital flat-panel detector facilitating more nearly
             complete sampling of frequency space and the physical breast
             volume; incorporation of iterative ordered-subsets
             transmission (OSTR) image reconstruction allowing modeling
             of the system matrix. Here, we describe the prototype 3D
             gantry and demonstrate initial system performance. Data
             collected on the prototype gantry demonstrate the
             feasibility of using OSTR with realistic reconstruction
             times. The gantry consists of a rotating W-anode x-ray tube
             using ultra-thick K-edge filtration, and an ∼20×25cm 2
             digital flat-panel detector located at &lt;60cm SID. This
             source/detector combination can be shifted laterally
             changing the location of the central ray relative to the
             system center-of-rotation, hence changing the effective
             imaging field-of-view, and is mounted on a goniometric
             cradle allowing &lt;50° polar tilt, then on a 360°
             azimuthal rotation stage. Combined, these stages provide for
             positioning flexibility in a banded region about a sphere,
             facilitating simple circle-plus-arc-like trajectories, as
             well as considerably more complex 3D trajectories. Complex
             orbits are necessary to avoid physical hindrances from the
             patient while acquiring the largest imaging volume of the
             breast. The system capabilities are demonstrated with
             fully-3D reconstructed images of geometric sampling and
             resolution phantoms, a fabricated breast phantom containing
             internal features of interest, and a cadaveric breast
             specimen. This compact prototype provides flexibility in
             dedicated, fully-SD CmT imaging of healthy and diseased
             breasts.},
   Doi = {10.1117/12.595636},
   Key = {fds269366}
}

@article{fds269483,
   Author = {Samei, E},
   Title = {Technological and psychophysical considerations for digital
             mammographic displays},
   Journal = {Radiographics},
   Volume = {25},
   Number = {2},
   Pages = {491-501},
   Year = {2005},
   Abstract = {Digital mammography is gradually replacing screen-film
             analog mammography, a transition driven by a desire to
             improve the efficiency and possibly the quality of the
             interpretation of mammograms. Digital mammography involves
             the use of electronic display devices to display the
             mammograms. Currently, two electronic technologies are used
             to display digital mammograms: the cathode-ray tube (CRT)
             and liquid crystal display (LCD). CRT and LCD devices have
             imaging characteristics markedly different from those of
             transilluminated film, which has conventionally been used to
             display analog mammograms. Consequently, the transition to
             digital mammography necessitates consideration of a number
             of psychophysical factors pertaining to effective display of
             mammograms. Some of these factors are related to specific
             performance characteristics of the display devices, whereas
             others are related to inherent characteristics of the human
             visual system. The main psychophysical factors that affect
             the interpretation of medical images are contrast,
             resolution, and noise. Optimal display of mammograms is
             achieved by taking these factors into consideration and by
             using time-efficient, intuitive, and reader-specific user
             interfaces. Because display devices are susceptible to
             variations in hardware and calibration and to degradation
             over time, acceptance testing and quality control testing
             are necessary to maintain an adequate level of display
             quality. ©RSNA, 2005.},
   Key = {fds269483}
}

@article{fds269304,
   Author = {McKinley, RL and Toraai, MP and Samei, E and Bradshaw,
             ML},
   Title = {Initial study of quasi-monochromatic x-ray beam performance
             for x-ray computed mammotomography},
   Journal = {IEEE Transactions on Nuclear Science},
   Volume = {52},
   Number = {5 I},
   Pages = {1243-1250},
   Year = {2005},
   ISSN = {0018-9499},
   url = {http://dx.doi.org/10.1109/TNS.2005.857629},
   Abstract = {We evaluate the feasibility, benefits, and operating
             parameters of a quasimonochromatic beam for a newly
             developed x-ray cone beam computed mammotomography
             application. The value of a near monochromatic x-ray source
             for fully 3D dedicated mammotomography is the expected
             improved ability to separate tissues with very small
             differences in attenuation coefficients while maintaining
             dose levels at or below that of existing dual view
             mammography. In previous studies, simulations for a range of
             tungsten tube potentials, K-edge filter materials, filter
             thicknesses, and a 12 cm uncompressed breast, with a digital
             flat-panel CsI(Tl) detector model, indicated that thick,
             rare earth filter materials may provide optimized image
             quality. Figures of merit computed included: lesion contrast
             under different filtering conditions; ratio of measured
             lesion contrast with and without filtering; and exposure
             efficiency (SNR 2/exposure). Initial experiments are
             performed with a custom built x-ray mammotomography system,
             cerium foil filters, and plastic breast and lesion
             tissue-equivalent slabs. Simulation results showed that tube
             potentials of 50-70 kVp with filters of Z = 57-63 yielded
             quasimonochromatic x-ray spectra with improved FOMs. Initial
             experimental measurements corroborate simulation results in
             that, relative trends and rank order of contrast ratios and
             exposure efficiency were in agreement. These studies show
             that this approach can be implemented practically with
             simple hardware and yield improved exposure efficiency
             versus the unfiltered or minimally filtered case. © 2005
             IEEE.},
   Doi = {10.1109/TNS.2005.857629},
   Key = {fds269304}
}

@article{fds269338,
   Author = {Jesneck, JL and Saunders, RS and Samei, E and Xia, JQ and Lo,
             JY},
   Title = {Detector evaluation of a prototype amorphous selenium-based
             full field digital mammography system},
   Journal = {Proceedings of SPIE},
   Volume = {5745},
   Number = {I},
   Pages = {478-485},
   Year = {2005},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.596087},
   Abstract = {This study evaluated the physical performance of a
             selenium-based direct full-field digital mammography
             prototype detector (Siemens Mammomat Novation DR), including
             the pixel value vs. exposure linearity, the modulation
             transfer function (MTF), the normalized noise power spectrum
             (NNPS), and the detective quantum efficiency (DQE). The
             current detector is the same model which received an
             approvable letter from FDA for release to the US market. The
             results of the current prototype are compared to those of an
             earlier prototype. Two IEC standard beam qualities (RQA-M2:
             Mo/Mo, 28 kVp, 2 mm Al; RQA-M4: Mo/Mo, 35 kVp, 2 mm Al) and
             two additional beam qualities (MW2: W/Rh, 28 kVp, 2 mm Al;
             MW4: W/Rh, 35 kVp, 2 mm Al) were investigated. To calculate
             the modulation transfer function (MTF), a 0.1 mm Pt-Ir edge
             was imaged at each beam quality. Detector pixel values
             responded linearly against exposure values (R 2 0.999). As
             before, above 6 cycles/mm Mo/Mo MTF was slightly higher
             along the chest-nipple axis compared to the left-right axis.
             MTF was comparable to the previously reported prototype,
             with slightly reduced resolution. The DQE peaks ranged from
             0.71 for 3.31 μC/kg (12.83 mR) to 0.4 for 0.48 μC/kg (1.86
             mR) at 1.75 cycles/mm for Mo/Mo at 28 kVp. The DQE range for
             W/Rh at 28 kVP was 0.81 at 2.03 μC/kg (7.87 mR) to 0.50 at
             0.50 μC/kg (1.94 mR) at 1 cycle/mm. NNPS tended to increase
             with greater exposures, while all exposures had a
             significant low-frequency component. Bloom and detector edge
             artifacts observed previously were no longer present in this
             prototype. The new detector shows marked noise improvement,
             with slightly reduced resolution. There remain artifacts due
             to imperfect gain calibration, but at a reduced magnitude
             compared to a prototype detector.},
   Doi = {10.1117/12.596087},
   Key = {fds269338}
}

@article{fds269369,
   Author = {Jr, RSS and Samei, E and Johnson, J and Baker, J},
   Title = {Effect of display resolution on the detection of
             mammographie lesions},
   Journal = {Proceedings of SPIE},
   Volume = {5749},
   Pages = {243-250},
   Year = {2005},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.595682},
   Abstract = {For diagnosis of breast cancer by mammography, the
             mammograms must be viewed by a radiologist. The purpose of
             this study was to determine the effect of display resolution
             on the specific clinical task of detection of breast lesions
             by a human observer. Using simulation techniques, this study
             proceeded through four stages. First, we inserted simulated
             masses and calcifications into raw digital mammograms. The
             resulting images were processed according to standard image
             processing techniques and appropriately windowed and
             leveled. The processed images were blurred according to MTFs
             measured from a clinical Cathode Ray Tube display.
             JNDMetrix, a Visual Discrimination Model, examined the
             images to estimate human detection. The model results
             suggested that detection of masses and calcifications
             decreased under standard CRT resolution. Future work will
             confirm these results with human observer studies. (This
             work was supported by grants NIH R21-CA95308 and USAMRMC
             W81XWH-04-1-0323.).},
   Doi = {10.1117/12.595682},
   Key = {fds269369}
}

@article{fds269376,
   Author = {Fetterly, KA and Samei, E},
   Title = {Photographic measurement of the effects of viewing angle on
             the luminance and contrast of liquid crystal
             displays},
   Journal = {Proceedings of SPIE},
   Volume = {5744},
   Number = {I},
   Pages = {263-270},
   Year = {2005},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.595772},
   Abstract = {An actively cooled charge couple device detector in
             combination with a 4 mm focal length lens (camera) was used
             to evaluate the luminance and perceived contrast properties
             of a liquid crystal display (LCD). The circular field of
             view (FOV) of the camera occupied an angular range (9) of
             ±42.5° from normal in all directions. Uniform field images
             corresponding to 17 equally spaced grayscale values in the 8
             bit digital driving level (DDL) range of the display system
             were acquired. The 12 bit grayscale digital images produced
             by the camera were converted to luminance (cd/m 2) units via
             the measured DDL vs. luminance response of the camera. The
             Barten model of the grayscale response of the human visual
             system was used to compute the perceived contrast of the
             display within the angular FOV of the camera and throughout
             the 8-bit DDL range of the display. 1D profiles were
             extracted from the 2D measurements and compared to
             measurements acquired from a similar display using a
             Fourier-optics-based luminance meter and published methods.
             The results of the two methods generally agreed to within
             5%. Greater discrepancy was realized for the lowest portion
             of the DDL range. The photographic methods used were
             straightforward and resulted in accurate display assessment
             measurements over a FOV that is relevant for the clinical
             use of LCDs.},
   Doi = {10.1117/12.595772},
   Key = {fds269376}
}

@article{fds269377,
   Author = {Boyce, SJ and Chawla, A and Samei, E},
   Title = {Physical evaluation of a high frame rate, extended dynamic
             range flat panel detector for real-time cone beam computed
             tomography applications},
   Journal = {Proceedings of SPIE},
   Volume = {5745},
   Number = {I},
   Pages = {591-599},
   Year = {2005},
   ISSN = {1605-7422},
   url = {http://dx.doi.org/10.1117/12.593881},
   Abstract = {The use of flat panel detectors in computed tomography (CT)
             systems can improve resolution, reduce system cost, and add
             operational flexibility by combining fluoroscopy and
             radiography applications within CT systems. However, some
             prior studies have suggested that flat panel detectors would
             not perform well in CT applications due to their lack of
             high dynamic range, lag artifacts, and inadequate frame
             rate. The purpose of this study was to perform a physical
             evaluation of a prototype flat panel detector capable of
             high frame rates and extended dynamic range. The flat panel
             detector used had a pixel size of 194 microns and a matrix
             size of 2048x1536. The detector could be configured for
             several combinations of frame rate and matrix size up to 750
             frames per second for a 512×16 matrix size with 4×4
             binning. The evaluation was performed in terms of the MTF
             and DQE as a function of frame rate and exposure at the IEC
             RQA5 (∼75 kVp, 21 mm Al) beam quality. The image lag was
             evaluated in terms of temporal-frequency dependent transfer
             function. Offset shift were also evaluated. Preliminary
             results indicate 0.1 MTF at 0.92 cycles/mm and DQE(0) of
             approximately 0.8, 0.6, 0.4, and 0.22 at 0.144, 0.065,
             0.035, and 0.008 mR per frame exposures. The temporal MTF
             exhibited a low-frequency drop and a value of 0.5 at the
             Nyquist frequency. Offset shift was negligible. Considering
             high frame rate capabilities of the new detector, the
             results suggest that the detector has potential for use in
             real-time CT applications including CT angiography.},
   Doi = {10.1117/12.593881},
   Key = {fds269377}
}

@article{fds269378,
   Author = {Poolla, A and Suri, JS and Samei, E and Pisano, ED and Minyard, T and Woodward, R and Schleupen, KR and Wright, S and Coley, S and Janer,
             R},
   Title = {MTF and NPS study of high-resolution LCDs and CRTs for
             mammography},
   Journal = {Digest of Technical Papers},
   Volume = {36},
   Number = {1},
   Pages = {196-199},
   Year = {2005},
   ISSN = {0097-966X},
   url = {http://dx.doi.org/10.1889/1.2036402},
   Abstract = {This paper presents a closer look on the link between the
             physical parameters (MTF and NPS) that characterize the
             performance of a liquid crystal display (LCD) and the
             architecture that generates the images. Understanding the
             major architectural difference between the cathode ray tube
             (CRT) and LCD displays can lead to better image quality
             analysis and characterization of the LCD displays. The aim
             of this research is to quantify two major image quality
             control parameters namely, modulation transfer function
             (MTF) and noise power spectrum (NPS) and understand their
             significance with respect to the architecture of the LCD and
             CRT displays. The experimentation was performed at Fischer
             Imaging Corporation research and development division in
             Denver, CO. We conclude the following: (1) The MTF of LCD is
             higher than that of CRT, and (2) LCD has higher NPS. The
             results thus infer that the LCD is better suitable display
             compared to CRT displays for mammography applications
             particularly considering its superior resolution. © 2005
             SID.},
   Doi = {10.1889/1.2036402},
   Key = {fds269378}
}

@article{fds269379,
   Author = {Poolla, A and Suri, JS and Sun, Y and Guo, Y and Samei, E and Pisano, E and Woodward, R and Minyard, T and Schleupen, K and Wright, S and Coley, S and Janer, R},
   Title = {A study of CRT (5-Mpixel) vs. LCD (9-Mpixel) displays for
             breast lesion detection in full-field digital mammography
             and ultrasound (FFDMUS) data sets via image-enhancement
             algorithms},
   Journal = {Digest of Technical Papers},
   Volume = {36},
   Number = {1},
   Pages = {368-371},
   Year = {2005},
   ISSN = {0097-966X},
   url = {http://dx.doi.org/10.1889/1.2036448},
   Abstract = {The latest technological changes are fast replacing the
             conventional cathode ray tube (CRT) displays with liquid
             crystal displays (LCDs). It is thus important to understand
             and evaluate them. The novelty of our evaluation strategy
             comes from the usage of computer aided diagnostics-based on
             pixel intensities. This evaluation system combines both
             lesion segmentation and quantification. Hence it is an
             integrated approach. The FFDMUS ultrasound data was acquired
             and then displayed on LCD and CRT displays. The FFDMUS
             ultrasound images were segmented using the signal-to-noise
             ratio (SNR) algorithm. We use Hausdoff distance measure
             (HDM) and polyline distance metric (PDM) for performance
             evaluation. Our results using the HDM method on FFDMUS
             ultrasound images show that lesions quantified from LCD
             images show a 29% improvement compared to lesions quantified
             from CRT images. A similar behavior was observed using PDM
             method. Hence we conclude that use of LCD displays for
             mammography applications with image enhancement techniques
             will have a greater diagnostic accuracy compared to the CRT
             displays. © 2005 SID.},
   Doi = {10.1889/1.2036448},
   Key = {fds269379}
}

@article{fds269380,
   Author = {Poolla, A and Sun, Y and Samei, E and Suri, J},
   Title = {Studying the effect of physics-based-enhancement on LCDs
             (IBM's 9.2 MP) and CRTs (Barco's 5 MP) on X=ray Mammograms
             acquired using Full Field Digital Mammography and Ultrasound
             (FFDMUS) System},
   Journal = {SID Conference Record of the International Display Research
             Conference},
   Pages = {162-165},
   Year = {2005},
   ISSN = {1083-1312},
   Abstract = {The latest technological changes In diagnostic radiology are
             fast replacing the conventional cathode ray tube (CRT)
             displays with liquid crystal displays (LCDs). Even though
             LCDs offer considerable advantages over conventional CRTs,
             the pixelated pattern of LCDs can obscure the
             micro-calcifications. It is thus important to understand and
             evaluate them. Our evaluation strategy is based on
             computer-aided diagnostics using physics-based enhancement
             and deformable models. This evaluation system combines both
             lesion segmentation and quantification. Hence, it is an
             integrated approach. The Full Field Digital Mammography
             (FFDM) 50 μm, X-ray images were acquired using Fischer's
             Full Field Digital Mammography and Ultrasound System
             (FFDMUS). These images were then enhanced to improve the
             contrast resolution using physics based strategy. The
             enhanced lesion images were displayed on LCD and CRT
             displays. We then segmented the lesions using gradient
             vector flow (GVF)-based deformable model and quantify them
             using the Hausdorff distance measure (HDM) and polyline
             distance metric (PDM). Our results using the PDM method on
             FFDMUS X-ray images show that lesions quantified from LCD
             images show a 12.5% improvement over lesions quantified from
             CRT images. A similar behavior was observed using HDM method
             where the result was 8.7% better on LCDs compared to CRTs.
             Hence we conclude that use of LCD displays for mammography
             applications with image enhancement techniques will have a
             better diagnostic accuracy when compared to the CRT
             displays. © Copyright 2005 Society for Information
             Display.},
   Key = {fds269380}
}

@article{fds132494,
   Author = {E Samei and JT Dobbins 3rd and JY Lo and MP Tornai},
   Title = {A framework for optimising the radiographic technique in
             digital X-ray imaging.},
   Journal = {Radiation protection dosimetry},
   Volume = {114},
   Number = {1-3},
   Pages = {220-9},
   Year = {2005},
   ISSN = {0144-8420},
   url = {http://dx.doi.org/10.1093/rpd/nch562},
   Keywords = {Bone and Bones • Cesium • Computers •
             Equipment Design • Humans • Iodides •
             Mammography • Models, Statistical • Radiation
             Dosage • Radiographic Image Enhancement •
             Radiographic Image Interpretation, Computer-Assisted •
             Radiography • Radiography, Thoracic • Radiology
             • Scattering, Radiation • Software • Tungsten
             • X-Ray Intensifying Screens • X-Rays* •
             chemistry • instrumentation* • methods •
             methods* • radiography},
   Abstract = {The transition to digital radiology has provided new
             opportunities for improved image quality, made possible by
             the superior detective quantum efficiency and
             post-processing capabilities of new imaging systems, and
             advanced imaging applications, made possible by rapid
             digital image acquisition. However, this transition has
             taken place largely without optimising the radiographic
             technique used to acquire the images. This paper proposes a
             framework for optimising the acquisition of digital X-ray
             images. The proposed approach is based on the signal and
             noise characteristics of the digital images and the applied
             exposure. Signal is defined, based on the clinical task
             involved in an imaging application, as the difference
             between the detector signal with and without a target
             present against a representative background. Noise is
             determined from the noise properties of uniformly acquired
             images of the background, taking into consideration the
             absorption properties of the detector. Incident exposure is
             estimated or otherwise measured free in air, and converted
             to dose. The main figure of merit (FOM) for optimisation is
             defined as the signal-difference-to-noise ratio (SdNR)
             squared per unit exposure or (more preferably) dose. This
             paper highlights three specific technique optimisation
             studies that used this approach to optimise the radiographic
             technique for digital chest and breast applications. In the
             first study, which was focused on chest radiography with a
             CsI flat-panel detector, a range of kV(p) (50-150) and
             filtration (Z = 13-82) were examined in terms of their
             associated FOM as well as soft tissue to bone contrast, a
             factor of importance in digital chest radiography. The
             results indicated that additive Cu filtration can improve
             image quality. A second study in digital mammography using a
             selenium direct flat-panel detector indicated improved SdNR
             per unit exposure with the use of a tungsten target and a
             rhodium filter than conventional molybdenum
             target/molybdenum filter techniques. Finally, a third study
             focusing on cone-beam computed tomography of the breast
             using a CsI flat-panel detector indicated that high Z
             filtration of a tungsten target X-ray beam can notably
             improve the signal and noise characteristics of the image.
             The general findings highlight the fact that the techniques
             that are conventionally assumed to be optimum may need to be
             revisited for digital radiography.},
   Language = {eng},
   Doi = {10.1093/rpd/nch562},
   Key = {fds132494}
}

@article{fds269478,
   Author = {Page, ESIBD},
   Title = {New DICOM elements promise better image quality},
   Journal = {Diagnostic Imaging Online},
   Year = {2004},
   Month = {December},
   url = {http://www.dimag.com/pacsweb/},
   Key = {fds269478}
}

@booklet{Samei04,
   Author = {Samei, E and Rowberg, A and Avraham, E and Cornelius,
             C},
   Title = {Toward clinically relevant standardization of image
             quality.},
   Journal = {Journal of Digital Imaging},
   Volume = {17},
   Number = {4},
   Pages = {271-278},
   Year = {2004},
   Month = {December},
   ISSN = {0897-1889},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/15551103},
   Abstract = {In recent years, notable progress has been made on
             standardization of medical image presentations in the
             definition and implementation of the Digital Imaging and
             Communications in Medicine (DICOM) Grayscale Standard
             Display Function (GSDF). In parallel, the American
             Association of Physicists in Medicine (AAPM) Task Group 18
             has provided much needed guidelines and tools for visual and
             quantitative assessment of medical display quality. In spite
             of these advances, however, there are still notable gaps in
             the effectiveness of DICOM GSDF to assure consistent and
             high-quality display of medical images. In additions the
             degree of correlation between display technical data and
             diagnostic usability and performance of displays remains
             unclear. This article proposes three specific steps that
             DICOM, AAPM, and ACR may collectively take to bridge the gap
             between technical performance and clinical use: (1) DICOM
             does not provide means and acceptance criteria to evaluate
             the conformance of a display device to GSDF or to address
             other image quality characteristics. DICOM can expand beyond
             luminance response, extending the measurable, quantifiable
             elements of TG18 such as reflection and resolution. (2) In a
             large picture archiving and communication system (PACS)
             installation, it is critical to continually track the
             appropriate use and performance of multiple display devices.
             DICOM may help with this task by adding a Device Service
             Class to the standard to provide for communication and
             control of image quality parameters between applications and
             devices, (3) The question of clinical significance of image
             quality metrics has rarely been addressed by prior efforts.
             In cooperation with AAPM, the American College of Radiology
             (ACR), and the Society for Computer Applications in
             Radiology (SCAR), DICOM may help to initiate research that
             will determine the clinical consequence of variations in
             image quality metrics (eg, GSDF conformance) and to define
             what constitutes image quality from a diagnostic
             perspective. Implementation of these three initiatives may
             further the reach and impact of DICOM toward quality
             medicine.},
   Doi = {10.1007/s10278-004-1031-5},
   Key = {Samei04}
}

@article{fds132484,
   Author = {E Samei and A Rowberg and E Avraham and C Cornelius},
   Title = {Toward clinically relevant standardization of image
             quality.},
   Journal = {Journal of digital imaging},
   Volume = {17},
   Number = {4},
   Pages = {271-8},
   Year = {2004},
   Month = {December},
   ISSN = {0897-1889},
   url = {http://dx.doi.org/10.1007/s10278-004-1031-5},
   Keywords = {Data Display • Diagnostic Imaging • Humans •
             Medical Informatics Computing • Radiology Information
             Systems* • standards*},
   Abstract = {In recent years, notable progress has been made on
             standardization of medical image presentations in the
             definition and implementation of the Digital Imaging and
             Communications in Medicine (DICOM) Grayscale Standard
             Display Function (GSDF). In parallel, the American
             Association of Physicists in Medicine (AAPM) Task Group 18
             has provided much needed guidelines and tools for visual and
             quantitative assessment of medical display quality. In spite
             of these advances, however, there are still notable gaps in
             the effectiveness of DICOM GSDF to assure consistent and
             high-quality display of medical images. In additions the
             degree of correlation between display technical data and
             diagnostic usability and performance of displays remains
             unclear. This article proposes three specific steps that
             DICOM, AAPM, and ACR may collectively take to bridge the gap
             between technical performance and clinical use: (1) DICOM
             does not provide means and acceptance criteria to evaluate
             the conformance of a display device to GSDF or to address
             other image quality characteristics. DICOM can expand beyond
             luminance response, extending the measurable, quantifiable
             elements of TG18 such as reflection and resolution. (2) In a
             large picture archiving and communication system (PACS)
             installation, it is critical to continually track the
             appropriate use and performance of multiple display devices.
             DICOM may help with this task by adding a Device Service
             Class to the standard to provide for communication and
             control of image quality parameters between applications and
             devices, (3) The question of clinical significance of image
             quality metrics has rarely been addressed by prior efforts.
             In cooperation with AAPM, the American College of Radiology
             (ACR), and the Society for Computer Applications in
             Radiology (SCAR), DICOM may help to initiate research that
             will determine the clinical consequence of variations in
             image quality metrics (eg, GSDF conformance) and to define
             what constitutes image quality from a diagnostic
             perspective. Implementation of these three initiatives may
             further the reach and impact of DICOM toward quality
             medicine.},
   Language = {eng},
   Doi = {10.1007/s10278-004-1031-5},
   Key = {fds132484}
}

@booklet{Mckinley04,
   Author = {Mckinley, RL and Tornai, MP and Samei, E and Bradshaw,
             ML},
   Title = {Simulation study of a quasi-monochromatic beam for x-ray
             computed mammotomography},
   Journal = {Medical Physics},
   Volume = {31},
   Number = {11},
   Pages = {800},
   Year = {2004},
   Month = {November},
   Key = {Mckinley04}
}

@booklet{Samei04d,
   Author = {Samei, E and Wright, SL},
   Title = {Luminance and contrast performance of liquid crystal
             displays for mammographic applications.},
   Journal = {Technology in cancer research & treatment},
   Volume = {3},
   Number = {5},
   Pages = {429-436},
   Year = {2004},
   Month = {October},
   ISSN = {1533-0346},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/15453807},
   Abstract = {Liquid crystal displays (LCDs) are gradually replacing
             cathode-ray tubes (CRTs) as the primary means of electronic
             display of digital radiographs. The transition from CRT to
             LCD is fueled by advantages of the LCD technology such as
             enhanced maximum luminance and smaller form factor. This
             transition is expected to extend to digital mammography as
             well. The purpose of this study was to report the on-axis
             luminance and contrast performance of five medical-grade
             LCDs in terms of compliance with the DICOM grayscale display
             function (GSDF) and AAPM TG18 guidelines. The display
             devices included two 3 Mpx monochrome LCDs (Planar Dome C3,
             and NDS 20.8" Nova), two 5 Mpx monochrome LCDs (NDS 21.3"
             Nova, and Totoku ME511L), and one 9 Mpx color LCD (IBM
             T221). The on-axis luminance values were measured at all
             8-bit driving levels using the TG18-LN test patterns and a
             baffled luminance meter and the results averaged. The
             luminance data were analyzed according to the AAPM TG18
             methodology. The measured L(min), L(max), mean
             DeltaJND/Deltap, and maximum local deviation in
             DeltaJND/Deltap from GSDF, kappa(256), ranged within
             0.43-0.87 cd/m(2), 263-715 cd/m(2), 2.15-2.72, and 0.79-1.46
             intervals, respectively. While the values varied notably
             between different devices, all devices conformed to the TG18
             criteria for primary class displays in terms of on-axis
             luminance response, and thus judged suitable for
             mammographic applications from on-axis luminance standpoint.
             Notwithstanding the findings, other factors such as matrix
             size, angular response, and color functionality should
             further be taken into consideration.},
   Doi = {10.1177/153303460400300503},
   Key = {Samei04d}
}

@article{fds132485,
   Author = {E Samei and SL Wright},
   Title = {Luminance and contrast performance of liquid crystal
             displays for mammographic applications.},
   Journal = {Technology in cancer research & treatment},
   Volume = {3},
   Number = {5},
   Pages = {429-36},
   Year = {2004},
   Month = {October},
   ISSN = {1533-0346},
   Keywords = {Breast Neoplasms • Female • Humans •
             Luminescent Measurements • Mammography •
             Radiographic Image Enhancement • Software •
             instrumentation • methods • methods* •
             radiography*},
   Abstract = {Liquid crystal displays (LCDs) are gradually replacing
             cathode-ray tubes (CRTs) as the primary means of electronic
             display of digital radiographs. The transition from CRT to
             LCD is fueled by advantages of the LCD technology such as
             enhanced maximum luminance and smaller form factor. This
             transition is expected to extend to digital mammography as
             well. The purpose of this study was to report the on-axis
             luminance and contrast performance of five medical-grade
             LCDs in terms of compliance with the DICOM grayscale display
             function (GSDF) and AAPM TG18 guidelines. The display
             devices included two 3 Mpx monochrome LCDs (Planar Dome C3,
             and NDS 20.8" Nova), two 5 Mpx monochrome LCDs (NDS 21.3"
             Nova, and Totoku ME511L), and one 9 Mpx color LCD (IBM
             T221). The on-axis luminance values were measured at all
             8-bit driving levels using the TG18-LN test patterns and a
             baffled luminance meter and the results averaged. The
             luminance data were analyzed according to the AAPM TG18
             methodology. The measured L(min), L(max), mean
             DeltaJND/Deltap, and maximum local deviation in
             DeltaJND/Deltap from GSDF, kappa(256), ranged within
             0.43-0.87 cd/m(2), 263-715 cd/m(2), 2.15-2.72, and 0.79-1.46
             intervals, respectively. While the values varied notably
             between different devices, all devices conformed to the TG18
             criteria for primary class displays in terms of on-axis
             luminance response, and thus judged suitable for
             mammographic applications from on-axis luminance standpoint.
             Notwithstanding the findings, other factors such as matrix
             size, angular response, and color functionality should
             further be taken into consideration.},
   Language = {eng},
   Key = {fds132485}
}

@booklet{Samei04e,
   Author = {E. Samei and R.S. Saunders and J.Y. Lo and J.T. Dobbins and J. L.
             Jesneck and C.E. Floyd and C.E. Ravin},
   Title = {Fundamental imaging characteristics of a slot-scan digital
             chest radiographic system},
   Journal = {Medical Physics},
   Volume = {31},
   Number = {9},
   Pages = {2687-2698},
   Year = {2004},
   Month = {September},
   Key = {Samei04e}
}

@article{fds269485,
   Author = {Samei, E and Saunders, RS and Lo, JY and Dobbins, JT and Jesneck, JL and Floyd, CE and Ravin, CE},
   Title = {Fundamental imaging characteristics of a slot-scan digital
             chest radiographic system.},
   Journal = {Medical physics},
   Volume = {31},
   Number = {9},
   Pages = {2687-2698},
   Year = {2004},
   Month = {September},
   ISSN = {0094-2405},
   url = {http://www.ncbi.nlm.nih.gov/pubmed/15487752},
   Keywords = {Equipment Design • Equipment Failure Analysis* •
             Humans • Phantoms, Imaging • Radiographic Image
             Enhancement • Radiography, Thoracic •
             Reproducibility of Results • Scattering, Radiation
             &bull