Biomedical Engineering : Publications since January 2008
List all publications in the database. :chronological combined listing:
%% Barr, Roger C
@article{2573262,
Author = {DiPersio, D.A. and Barr, R.C.},
Title = {Evaluation of the fan method of adaptive sampling on human
electrocardiograms},
Journal = {Med. Biol. Eng. Comput. (UK)},
Volume = {23},
Number = {5},
Pages = {401 - 10},
Keywords = {electrocardiography;},
Abstract = {The fan is a method of adaptive sampling that selects
samples from electrocardiograms more rapidly during periods
of rapid waveform change and more slowly otherwise. One
attribute of the fan is the guarantee that the original
waveform can be reconstructed within tolerance ε. Many
questions about the particulars of the fan's performance on
human ECGs have been undocumented, e.g, what ε choice
leads to good quality recording, how does the choice of
ε effect visual quality, and what average sampling
rates occur? The paper provides answers to these and other
questions. It is based on retrospective analysis of 20700
human ECG waveforms from subjects of all ages. The results
show, for example, that ε=10 μV leads to high
quality waveforms sampled at an average rate of 266 samples
s<sup>-1</sup> with maximum errors only 1/24 th the maximum
errors using uniform sampling at 250 samples s<sup>-1</sup>,
and that ε=30 μV leads to waveforms showing all
deflections at an average rate of 45 samples s<sup>-1</sup>
with maximum errors only 1/57 th of the maximum errors from
uniform sampling at 45 samples s<sup>-1</sup>},
Key = {2573262}
}
@article{4035817,
Author = {Plonsey, R. and Barr, R.C. and Witkowski,
F.X.},
Title = {One-dimensional model of cardiac defibrillation},
Journal = {Med. Biol. Eng. Comput. (UK)},
Volume = {29},
Number = {5},
Pages = {465 - 9},
Keywords = {bioelectric phenomena;biomembranes;cardiology;cellular
biophysics;physiological models;},
Abstract = {The response of a single strand of cardiac cells to a
uniform defibrillatory shock assuming steady-state linear
conditions is examined. It is argued that the effect of this
current is quantitatively described by the induced
transmembrane potential even under passive conditions. The
characteristics of the single strand are those that would
exist if the heart was a system of equivalent parallel
pathways from apex to base. It is shown that essentially
every cell is both hyperpolarised and depolarised from the
shock by an amount proportional to the stimulus intensity
and the intercellular junctional resistance. For
physiological values of model parameters the evaluated
depolarisations are consistent with levels necessary to
affect electrophysiological behaviour},
Key = {4035817}
}
@article{3042774,
Author = {Di Persio and D.A. and Barr, R.C.},
Title = {A prototype inverse solution in one-dimension to find the
origin of excitation, strand radius, intracellular
resistivity, or distance from the surface},
Journal = {IEEE Trans. Biomed. Eng. (USA)},
Volume = {BME-34},
Number = {9},
Pages = {681 - 91},
Keywords = {bioelectric phenomena;cardiology;cellular
biophysics;},
Abstract = {A computer simulation of a strand 11.8 mm long was used to
examine whether extracellular waveforms from a
one-dimensional strand can be used to find the site of
origin of excitation (<i>x</i><sub>s0</sub>), strand radius
(<i>a</i><sub>0</sub>), intracellular resistivity
(<i>R</i><sub>i0</sub>), or distance of the electrodes from
the strand (<i>b</i><sub>0</sub>). The Ebihara-Johnson
equations were used to model the membrane's behavior.
Extracellular waveforms simulated at two of 60 points along
the strand were used as `measurements'. The inverse
calculations had the objective of finding one or two of the
variables <i>x</i><sub>s0</sub>, <i>a</i><sub>0</sub>,
<i>R</i><sub>i0</sub>, or <i>b</i><sub>0</sub> with the
others known. The solution procedure compared the `measured'
waveforms to trial waveforms obtained by varying all unknown
parameters through their physiological range. The error
curves were frequently found to have several relative
minima. In general, however, no combination of unknowns
other than the correct one led to rms errors within
experimental noise levels, a result in marked contrast to
that of most other inverse calculations in
electrocardiography},
Key = {3042774}
}
@article{1266888,
Author = {Hersh, L.T. and Barr, R.C. and Spach, M.S.},
Title = {An analysis of transfer coefficients calculated directly
from epicardial and body surface potential measurements in
the intact dog},
Journal = {IEEE Trans. Biomed. Eng. (USA)},
Volume = {BME-25},
Number = {5},
Pages = {446 - 61},
Keywords = {bioelectric potentials;biological techniques and
instruments;electrocardiography;},
Abstract = {The study considered the feasibility of obtaining transfer
coefficients directly from sequences of epicardial and body
surface measurements of ventricular excitation and
repolarisation potential distributions, rather than from
measurements of the geometry of the volume conductor. The
transfer coefficients were calculated from the measured
potentials via the mathematical method of using a Bayes
estimator. The merit of this approach was that it offered
the possibility of accurately representing the
characteristics of the volume conductor without directly
measuring either the volume conductor's geometry or its
inhomogeneities. The experimental protocol made use of
measurements from two dogs},
Key = {1266888}
}
@article{8123233,
Author = {Mossop, B.J. and Barr, R.C. and Zaharoff, D.A. and Fan
Yuan},
Title = {Electric fields within cells as a function of membrane
resistivity-a model study},
Journal = {IEEE Trans. Nanobiosc. (USA)},
Volume = {3},
Number = {3},
Pages = {225 - 31},
url = {http://dx.doi.org/10.1109/TNB.2004.833703},
Keywords = {bioelectric potentials;biological effects of
fields;biomembranes;cellular effects of radiation;physiological
models;},
Abstract = {Externally applied electric fields play an important role in
many therapeutic modalities, but the fields they produce
inside cells remain largely unknown. This study makes use of
a three-dimensional model to determine the electric field
that exists in the intracellular domain of a 10-μm
spherical cell exposed to an applied field of 100 V/cm. The
transmembrane potential resulting from the applied field was
also determined and its change was compared to those of the
intracellular field. The intracellular field increased as
the membrane resistance decreased over a wide range of
values. The results showed that the intracellular electric
field was about 1.1 mV/cm for R<sub>m</sub> of 10 000
Ω·cm<sup>2</sup>, increasing to about 111 mV/cm
as R<sub>m</sub> decreased to 100 Ω·cm<sup>2</sup>.
Over this range of R<sub>m</sub> the transmembrane potential
was nearly constant. The transmembrane potential declined
only as R<sub>m</sub> decreased below 1 Ω·cm<sup>2</sup>.
The simulation results suggest that intracellular electric
field depends on R<sub>m</sub> in its physiologic range, and
may not be negligible in understanding some mechanisms of
electric field-mediated therapies},
Key = {8123233}
}
%% Bass, Cameron R. 'Dale'
@booklet{Salzar09,
Author = {R. S. Salzar and C. R. Bass and D. Lessley and J. R.
Crandall and R. W. Kent and J. R. Bolton},
Title = {Viscoelastic Response of the Thorax under Dynamic Belt
Loading},
Journal = {Traffic Injury Prevention},
Volume = {10},
Number = {3},
Pages = {290 -- 296},
Year = {2009},
ISSN = {1538-9588},
Abstract = {Objective: Three postmortem human surrogates (PMHS) were
positioned and rigidly mounted through the spine to a
tabletop test fixture for the purpose of characterizing
thoracic response to diagonal belt loading with well-defined
boundary conditions. Methods: These PMHS were mounted to a
stationary apparatus that supported the spine and shoulders
in a configuration comparable to that seen in a 48 km/h
automobile sled test at the time of maximum chest
deformation. A belt restraint was positioned across the
anterior torso with attachments at D-ring and buckle
locations based on the geometry of a mid-sized sedan. The
belt was attached to a trolley driven by a hydraulic ram
linked to a universal test machine. Ramp and hold
experiments were conducted at rates of 0.5, 0.9, and 1.2 m/s
and hold times of 60 s. Ramp-hold displacement waveforms of
up to 20 percent of the chest depth were applied to the
chest while the resulting belt loads and spinal reaction
loads were recorded. These data were used to identify
parameters in a seven-parameter thoracic structural model
mathematically analogous to a viscoelastic material model. A
final test with 40 percent deflection was performed at the
completion of the loading sequence. Results: Model fits to
ramps of different magnitudes indicated that the assumption
of temporal linearity was reasonable over the range of
inputs in this study. In agreement with previous studies,
the spatial (force-deflection) response was only slightly
nonlinear, indicating that a fully linear model would be
reasonable up to the deflection levels used here.
Conclusions: Pronounced variability in the instantaneous
elastic behavior was observed among the three test subjects,
whereas the relaxation behavior exhibited less
variability.},
Key = {Salzar09}
}
@booklet{Salzar09a,
Author = {R. S. Salzar and D. Genovese and C. R. Bass and J. R. Bolton and H. Guillemot and A. M. Damon and J. R.
Crandall},
Title = {Load path distribution within the pelvic structure under
lateral loading},
Journal = {International Journal Of Crashworthiness},
Volume = {14},
Number = {1},
Pages = {99 -- 110},
Year = {2009},
ISSN = {1358-8265},
Abstract = {Lateral loading of the pelvis occurs for both vehicle
occupants struck during side impacts as well as pedestrians.
This research investigated the load distribution through the
anterior (i.e. pubic symphysis) and posterior (i.e. sacrum)
aspects of the pelvis for both acetabular and iliac loading.
Sixteen male post-mortem human surrogate pelves were tested
in quasi-static (n = 4) anddynamic (n = 12) conditions. On
the basis of finite element model simulations of a
pedestrian being struck at 40 km/hr, a velocity profile for
the dynamic tests was prescribed that began at rest (v = 0
m/s) and then achieved apeak velocity of the struck pelvis
moving relative to the midline at 4.5 m/s. The average
anterior load at fracture from a high - rate acetabulumimp
act was 1911 929 N compared to the posterior load averaging
1022 630 N. The average anterior load at fracture from a
high - rate iliumimpact was 418 388 N compared to the
posterior load averaging 3107 1473 N.},
Key = {Salzar09a}
}
@booklet{Bass08,
Author = {C. R. Bass and K. A. Rafaels and R. S. Salzar},
Title = {Pulmonary injury risk assessment for short-duration
blasts},
Journal = {Journal Of Trauma-injury Infection And Critical
Care},
Volume = {65},
Number = {3},
Pages = {604 -- 615},
Year = {2008},
Month = {September},
ISSN = {0022-5282},
Abstract = {Background: Blast injuries are becoming more common in
modern war and terrorist action. This increasing threat
underscores the importance of understanding and evaluating
blast effects. Methods: For this study, data on more than
2,550 large animal experiments were collected from more than
50 experimental studies on blast. From this dataset, over
1,100 large animal experiments were selected with positive
phase overpressure durations of 30 milliseconds or less. A
two variable nonlinear logistic regression was performed on
the experimental data for threshold injury and lethality in
terms of pressure and duration. The effects of mass,
pressure, and duration scaling were all evaluated. Results:
New injury risk assessment curves were analyzed for both
incident and reflected pressure conditions. Position
dependent injury risk curves were also analyzed and were
found to be unnecessary, at least for prone and side on
conditions. Conclusions: The injury risk assessment showed
good correlation to some of the existing injury assessments.
It also showed good correspondence to a reported human case
of blast exposure. Pressure scaling was analyzed to be
unnecessary for these short duration exposures. Recommended
injury assessments for various orientations relative to the
incoming blast wave are included.},
Key = {Bass08}
}
@booklet{Lucas08,
Author = {S. R. Lucas and C. R. Bass and R. S. Salzar and M. L. Oyen and C. Planchak and A. Ziemba and B. S. Shender and G.
Paskoff},
Title = {Viscoelastic properties of the cervical spinal ligaments
under fast strain-rate deformations},
Journal = {Acta Biomaterialia},
Volume = {4},
Number = {1},
Pages = {117 -- 125},
Year = {2008},
Month = {January},
ISSN = {1742-7061},
Abstract = {The mechanical response of ligaments under fast strain-rate
deformations is a necessary input into computational models
that are used for injury assessment. However, this
information frequently is not available for the ligaments
that are routinely injured in fast-rate loading scenarios.
In the current study, experiments were conducted at fast
strain rates for the cervical spinal ligaments: the anterior
longitudinal ligament, the posterior longitudinal ligament
and the ligamentum flavum. Bone-ligament-bone complexes at
three spine levels were harvested for mechanical testing.
Displacement-controlled sub-failure uniaxial tensile tests
were performed in both load-relaxation and sinusoidal
conditions. A nonlinear (separable) viscoelastic model was
used to examine the experimental data. An unexpected result
of the modeling was that the instantaneous elastic functions
could be approximated as linear for these strain rates. A
five-parameter model was sufficient to characterize the
ligament viscoelastic responses and had good predictive
capacity under different applied loading conditions. (C)
2007 Acta Materialia Inc. Published by Elsevier Ltd. All
rights reserved.},
Key = {Lucas08}
}
%% Bursac, Nenad
@booklet{Pedrotty09,
Author = {D. M. Pedrotty and R. Y. Klinger and R. D. Kirkton and N.
Bursac},
Title = {Cardiac fibroblast paracrine factors alter impulse
conduction and ion channel expression of neonatal rat
cardiomyocytes},
Journal = {Cardiovascular Research},
Volume = {83},
Number = {4},
Pages = {688 -- 697},
Year = {2009},
Month = {September},
ISSN = {0008-6363},
Abstract = {The pathological proliferation of cardiac fibroblasts (CFs)
in response to heart injury results in fibrosis, which
correlates with arrhythmia generation and heart failure.
Here we systematically examined the effect of
fibroblast-derived paracrine factors on electrical
propagation in cardiomyocytes. Neonatal rat cardiac
monolayers were exposed for 24 h to media conditioned by
CFs. Optical mapping, sharp microelectrode recordings,
quantitative RT-PCR, and immunostaining were used to assess
the changes in the propagation and shape of the action
potential and underlying changes in gene and protein
expression. The fibroblast paracrine factors produced a 52\%
reduction in cardiac conduction velocity, a 217\%
prolongation of action potential duration, a 64\% decrease
of maximum capture rate, a 21\% increase in membrane resting
potential, and an 80\% decrease of action potential upstroke
velocity. These effects were dose dependent and partially
reversible with removal of the conditioned media. No
fibroblast proliferation, cardiomyocyte apoptosis, or
decreased connexin-43 expression, phosphorylation, and
function were found in conditioned cardiac cultures. In
contrast, the expression of the fast sodium, inward
rectifying potassium, and transient outward potassium
channels were, respectively, reduced 3.8-, 6.6-fold, and to
undetectable levels. The expression of beta-myosin heavy
chain increased 17.4-fold. No electrophysiological changes
were observed from media conditioned by CFs in the presence
of cardiomyocytes. Paracrine factors from neonatal CFs alone
produced significant electrophysiological changes in
neonatal rat cardiomyocytes resembling those found in
several cardiac pathologies.},
Key = {Pedrotty09}
}
@booklet{Mcspadden09,
Author = {L. C. Mcspadden and R. D. Kirkton and N.
Bursac},
Title = {Electrotonic loading of anisotropic cardiac monolayers by
unexcitable cells depends on connexin type and expression
level},
Journal = {American Journal Of Physiology-cell Physiology},
Volume = {297},
Number = {2},
Pages = {C339 -- C351},
Year = {2009},
Month = {August},
ISSN = {0363-6143},
Abstract = {McSpadden LC, Kirkton RD, Bursac N. Electrotonic loading of
anisotropic cardiac monolayers by unexcitable cells depends
on connexin type and expression level. Am J Physiol Cell
Physiol 297: C339-C351, 2009. First published June 3, 2009;
doi: 10.1152/ajpcell.00024.2009. Understanding how
electrotonic loading of cardiomyocytes by unexcitable cells
alters cardiac impulse conduction may be highly relevant to
fibrotic heart disease. In this study, we optically mapped
electrical propagation in confluent, aligned neonatal rat
cardiac monolayers electrotonically loaded with cardiac
fibroblasts, control human embryonic kidney (HEK-293) cells,
or HEK-293 cells genetically engineered to overexpress the
gap junction proteins connexin-43 or connexin-45. Gap
junction expression and function were assessed by
immunostaining, immunoblotting, and fluorescence recovery
after photobleaching and were correlated with the optically
mapped propagation of action potentials. We found that
neonatal rat ventricular fibroblasts negative for the
myofibroblast marker smooth muscle alpha-actin expressed
connexin-45 rather than connexin-43 or connexin-40, weakly
coupled to cardiomyocytes, and, without significant
depolarization of cardiac resting potential, slowed cardiac
conduction to 75\% of control only at high ($>$60\%)
coverage densities, similar to loading effects found from
HEK-293 cells expressing similar levels of connexin-45. In
contrast, HEK-293 cells with connexin-43 expression similar
to that of cardiomyocytes significantly decreased cardiac
conduction velocity and maximum capture rate to as low as
22\% and 25\% of control values, respectively, while
increasing cardiac action potential duration to 212\% of
control and cardiac resting potential from -71.6 +/- 4.9 mV
in controls to -65.0 +/- 3.8 mV. For all unexcitable cell
types and coverage densities, velocity anisotropy ratio
remained unchanged. Despite the induced conduction slowing,
none of the loading cell types increased the proportion of
spontaneously active monolayers. These results signify
connexin isoform and expression level as important
contributors to potential electrical interactions between
unexcitable cells and myocytes in cardiac
tissue.},
Key = {Mcspadden09}
}
@booklet{Badie09,
Author = {N. Badie and N. Bursac},
Title = {Novel Micropatterned Cardiac Cell Cultures with Realistic
Ventricular Microstructure},
Journal = {Biophysical Journal},
Volume = {96},
Number = {9},
Pages = {3873 -- 3885},
Year = {2009},
Month = {May},
ISSN = {0006-3495},
Abstract = {Systematic studies of cardiac structure-function
relationships to date have been hindered by the intrinsic
complexity and variability of in vivo and ex vivo model
systems. Thus, we set out to develop a reproducible cell
culture system that can accurately replicate the realistic
microstructure of native cardiac tissues. Using cell
micropatterning techniques, we aligned cultured
cardiomyocytes at micro- and macroscopic spatial scales to
follow local directions of cardiac fibers in murine
ventricular cross sections, as measured by high-resolution
diffusion tensor magnetic resonance imaging. To elucidate
the roles Of ventricular tissue microstructure in
macroscopic impulse conduction, we optically mapped membrane
potentials in micropatterned cardiac cultures with realistic
tissue boundaries and natural cell orientation, cardiac
cultures with realistic tissue boundaries but random cell
orientation, and standard isotropic monolayers. At 2 Hz
pacing, both microscopic changes in cell orientation and
ventricular tissue boundaries independently and
synergistically increased the spatial dispersion of
conduction velocity, but not tie action potential duration.
The realistic variations in intramural microstructure
created unique spatial signatures in micro- and macroscopic
impulse propagation within ventricular cross-section
cultures. This novel in vitro model system is expected to
help bridge the existing gap between experimental
structure-function studies in standard cardiac monolayers
and intact hear: tissues.},
Key = {Badie09}
}
@booklet{Bian09,
Author = {W. N. Bian and N. Bursac},
Title = {Engineered skeletal muscle tissue networks with controllable
architecture},
Journal = {Biomaterials},
Volume = {30},
Number = {7},
Pages = {1401 -- 1412},
Year = {2009},
Month = {March},
ISSN = {0142-9612},
Abstract = {The engineering of functional skeletal muscle tissue
substitutes holds promise for the treatment of various
muscular diseases and injuries. However, no tissue
fabrication technology currently exists for the generation
of a relatively large and thick bioartificial muscle made of
densely packed, uniformly aligned, and differentiated
myofibers. In this study, we describe a versatile
cell/hydrogel micromolding approach where
polydimethylsiloxane (PDMS) molds containing an array of
elongated posts were used to fabricate relatively large
neonatal rat skeletal muscle tissue networks with
reproducible and controllable architecture. By combining
cell-mediated fibrin gel compaction and precise
microfabrication of mold dimensions including the length and
height of the PDMS posts, we were able to simultaneously
support high cell viability, guide cell alignment along the
microfabricated tissue pores, and reproducioly control the
overall tissue porosity, size, and thickness. The
interconnected muscle bundles within file porous tissue
networks were composed of densely packed, aligned, and
highly differentiated myofibers. The formed myofibers
expressed myogenin, developed abundant cross-striations, and
generated spontaneous tissue contractions at the macroscopic
spatial scale. The proliferation of non-muscle cells was
significantly reduced compared to monolayer cultures. The
more complex muscle tissue architectures were fabricated by
controlling the spatial distribution and direction of the
PDMS posts. (c) 2008 Elsevier Ltd. All rights
reserved.},
Key = {Bian09}
}
@booklet{Badle08,
Author = {N. Badle and N. Bursac},
Title = {Micropatterned Ventricular Slice: Role of Realistic Tissue
Microstructure In Impulse Conduction},
Journal = {Circulation},
Volume = {118},
Number = {18},
Pages = {S493 -- S493},
Year = {2008},
Month = {October},
ISSN = {0009-7322},
Key = {Badle08}
}
@booklet{Klinger08,
Author = {R. Klinger and N. Bursac},
Title = {In Vitro Cellular Implantation Assay To Quantitatively
Compare The Ability Of Different Donor Cells To Electrically
Conduct Within Cardiac Tissue},
Journal = {Circulation},
Volume = {118},
Number = {18},
Pages = {S395 -- S395},
Year = {2008},
Month = {October},
ISSN = {0009-7322},
Key = {Klinger08}
}
@booklet{Pedrotty08,
Author = {D. M. Pedrotty and R. Y. Klinger and N. Badie and S. Hinds and A. Kardashian and N. Bursac},
Title = {Structural coupling of cardiomyocytes and noncardiomyocytes:
quantitative comparisons using a novel micropatterned cell
pair assay},
Journal = {American Journal Of Physiology-heart And Circulatory
Physiology},
Volume = {295},
Number = {1},
Pages = {H390 -- H400},
Year = {2008},
Month = {July},
ISSN = {0363-6135},
Abstract = {Well-controlled studies of the structural and functional
interactions between cardiomyocytes and other cells are
essential for understanding heart pathophysiology and for
the further development of safe and efficient cell
therapies. We established a novel in vitro assay composed of
a large number of individual micropatterned cell pairs with
reproducible shape, size, and region of cell-cell contact.
This assay was applied to quantify and compare the frequency
of expression and distribution of electrical (connexin43)
and mechanical (N-cadherin) coupling proteins in 5,000 cell
pairs made of cardiomyocytes (CMs), cardiac fibroblasts
(CFs), skeletal myoblasts (SKMs), and mesenchymal stem cells
(MSCs). We found that for all cell pair types, side-side
contacts between two cells formed 4.5-14.3 times more often
than end-end contacts. Both connexin43 and N- cadherin were
expressed in all homotypic CM pairs but in only 13.4-91.6\%
of pairs containing noncardiomyocytes, where expression was
either junctional (at the site of cell-cell contact) or
diffuse (inside the cytoplasm). CM expression was
exclusively junctional in homotypic pairs but predominantly
diffuse in heterotypic pairs. Noncardiomyocyte homotypic
pairs exhibited diffuse expression 1.7-8.7 times more often
than junctional expression, which was increased 2.6-4.4
times in heterotypic pairs. Junctional connexin43 and N-
cadherin expression, respectively, were found in 38.6 +/-
7.3 and 39.6 +/- 6.2\% of CM-MSC pairs, 21.9 +/- 5.0 and
13.6 +/- 1.9\% of CM-SKM pairs, and in only 3.8-9.6\% of
CM-CF pairs. Measured frequencies of protein expression and
distribution were stable for at least 4 days. Described
studies in micropatterned cell pairs shed new light on
cellular interactions relevant for cardiac function and cell
therapies.},
Key = {Pedrotty08}
}
%% Chen, Jun
@article{fds71256,
Author = {Boyd LM and Richardson WJ and Allen KD and Flahiff CM and Jing L and Li Y and Chen J and Setton LA},
Title = {Early onset degeneration of the intervertebral disc and
vertebral endplate in mice deficient in type IX
collagen},
Journal = {Arthritis and Rheumatism},
Volume = {58},
Pages = {in press},
Year = {2008},
Key = {fds71256}
}
%% Chilkoti, Ashutosh
@booklet{Nettles09,
Author = {D. L. Nettles and A. Chilkoti and L. A. Setton},
Title = {Early Metabolite Levels Predict Long-Term Matrix
Accumulation for Chondrocytes in Elastin-like Polypeptide
Biopolymer Scaffolds},
Journal = {Tissue Engineering Part A},
Volume = {15},
Number = {8},
Pages = {2113 -- 2121},
Year = {2009},
Month = {August},
ISSN = {1937-3341},
Abstract = {The development of cartilage tissue engineering scaffolds
could greatly benefit from methods to evaluate the
interactions of cells with scaffolds that are rapid, are
nondestructive, and can be carried out at early culture
times. Motivated by this rationale, the objective of the
current study was to evaluate whether the concentration of
metabolites in scaffold-cell cultures at early culture times
could predict matrix synthesis in the same samples at longer
culture times. Metabolite and matrix synthesis were measured
for 16 different formulations of cell-laden elastin-like
polypeptide hydrogels. Metabolites were measured at days 4
and 7 of culture, while matrix accumulation was evaluated at
day 28. Four of the 16 formulations resulted in molar ratios
of lactate: glucose near 2, indicating anaerobic metabolism
of glucose, which resulted in collagen: glycosaminoglycan
accumulation ratios near those of native tissue. Lactate and
pyruvate concentrations were found to significantly
correlate with both sulfated glycosaminoglycan and
hydroxyproline accumulation, with better fits for the
latter. Lactate was found to be the strongest predictor of
both matrix components, suggesting that measuring this
metabolite at very early culture times may be useful for
evaluating the status of tissue engineering constructs in a
rapid and nondestructive manner.},
Key = {Nettles09}
}
@booklet{Christensen09,
Author = {T. Christensen and M. Amiram and S. Dagher and K.
Trabbic-carlson and M. F. Shamji and L. A. Setton and A.
Chilkoti},
Title = {Fusion order controls expression level and activity of
elastin-like polypeptide fusion proteins},
Journal = {Protein Science},
Volume = {18},
Number = {7},
Pages = {1377 -- 1387},
Year = {2009},
Month = {July},
ISSN = {0961-8368},
Abstract = {We have previously developed a method to purify recombinant
proteins, termed inverse transition cycling (ITC) that
eliminates the need for column chromatography. ITC exploits
the inverse solubility phase transition of an elastin-like
polypeptide (ELP) that is fused to a protein of interest. In
ITC, a recombinant ELP fusion protein is cycled through its
phase transition, resulting in separation of the ELP fusion
protein from other Escherichia coli contaminants. Herein, we
examine the role of the position of the ELP in the fusion
protein on the expression levels and yields of purified
protein for four recombinant ELP fusion proteins. Placing
the ELP at the C-terminus of the target protein
(protein-ELP) results in a higher expression level for the
four ELP fusion proteins, which also translates to a greater
yield of purified protein. The position of the fusion
protein also has a significant impact on its specific
activity, as ELP-protein constructs have a lower specific
activity than protein-ELP constructs for three out of the
four proteins. Our results show no difference in mRNA levels
between protein-ELP and ELP-protein fusion constructs.
Instead, we suggest two possible explanations for these
results: first, the translational efficiency of mRNA may
differ between the fusion protein in the two orientations
and second, the lower level of protein expression and lower
specific activity is consistent with a scenario that
placement of the ELP at the N-terminus of the fusion protein
increases the fraction of misfolded, and less active
conformers, which are also preferentially degraded compared
to fusion proteins in which the ELP is present at the
C-terminal end of the protein.},
Key = {Christensen09}
}
@booklet{Hucknall09a,
Author = {A. Hucknall and A. J. Simnick and R. T. Hill and A. Chilkoti and A. Garcia and M. S. Johannes and R. L. Clark and S.
Zauscher and B. D. Ratner},
Title = {Versatile synthesis and micropatterning of nonfouling
polymer brushes on the wafer scale},
Journal = {Biointerphases},
Volume = {4},
Number = {2},
Pages = {FA50 -- FA57},
Year = {2009},
Month = {June},
ISSN = {1559-4106},
Abstract = {In this article, the authors describe new approaches to
synthesize and pattern surfaces with poly[oligo(ethylene
glycol) methyl methacrylate] (POEGMA) polymer brushes
synthesized by surface-initiated atom transfer radical
polymerization. These patterned coatings confer "nonfouling"
properties protein and cell resistance-to the surface in a
biological milieu. The versatile routes for the synthesis of
POEGMA demonstrated here offer clear advantages over other
techniques previously used in terms of their simplicity,
reliability, and ability to pattern large-area substrates.
They also demonstrate that POEGMA polymer brushes can be
patterned directly by photolithography, plasma ashing, and
reactive ion etching to create patterns at the micro- and
nanoscale over large areas with high throughput and
repeatability, while preserving the protein and cell
resistance of the POEGMA brush.},
Key = {Hucknall09a}
}
@booklet{Hucknall09,
Author = {A. Hucknall and S. Rangarajan and A. Chilkoti},
Title = {In Pursuit of Zero: Polymer Brushes that Resist the
Adsorption of Proteins},
Journal = {Advanced Materials},
Volume = {21},
Number = {23},
Pages = {2441 -- 2446},
Year = {2009},
Month = {June},
ISSN = {0935-9648},
Abstract = {Protein resistant or "non-fouling" surface are of great
interest for a variety of biomedical and biotechnology
applications. This article briefly reviews the development
of protein resistant surface, followed by recent research on
a new methodology to fabricate non-fouling surface by
surface-initiated polymerization. We show that polymer
brushes synthesized by surface-initiated polymerization that
present short oligo(ethylene glycol) side chains are
exceptionally resistant to protein adsorption and cell
adhesion. The importance of the protein and cell resistance
conferred by these polymer brushes is illustrated by their
use as substrates for the fabrication of antibody
microarrays that exhibit femtomolar limits of detection in
complex fluids such as serum and blood with relaxed
requirements for intermediate wash steps. This example
highlights the important point that the reduction in
background noise afforded by protein-resistant surface can
greatly simply the development of ultrasensitive
heterogeneous, surface-based clinical and proteomic assays
with increased sensitivity and utility.},
Key = {Hucknall09}
}
@booklet{Zauscher09,
Author = {S. Zauscher and A. Chilkoti},
Title = {Biological Applications of Polymer Brushes},
Journal = {Biointerphases},
Volume = {4},
Number = {2},
Pages = {FA1 -- FA2},
Year = {2009},
Month = {June},
ISSN = {1559-4106},
Key = {Zauscher09}
}
@booklet{Hucknall09b,
Author = {A. Hucknall and D. H. Kim and S. Rangarajan and R. T. Hill and W. M. Reichert and A. Chilkoti},
Title = {Simple Fabrication of Antibody Microarrays on Nonfouling
Polymer Brushes with Femtomolar Sensitivity for Protein
Analytes in Serum and Blood},
Journal = {Advanced Materials},
Volume = {21},
Number = {19},
Pages = {1968 -- 1971},
Year = {2009},
Month = {May},
ISSN = {0935-9648},
Abstract = {A multianalyte antibody array that is spotted on a
poly(oligo(ethylene glycol) methacrylate) brush 100 nm
thick, grown on glass via surface-initiated atom transfer
radical polymerization, has femtomolar limit-of-detection
(LOD) of cytokines in serum and whole blood, and a dynamic
range of six orders of magnitude for a range of protein
analytes.},
Key = {Hucknall09b}
}
@booklet{Nusz09,
Author = {G. J. Nusz and A. C. Curry and S. M. Marinakos and A. Wax and A. Chilkoti},
Title = {Rational Selection of Gold Nanorod Geometry for Label-Free
Plasmonic Biosensors},
Journal = {Acs Nano},
Volume = {3},
Number = {4},
Pages = {795 -- 806},
Year = {2009},
Month = {April},
ISSN = {1936-0851},
Abstract = {We present the development of an analytical model that can
be used for the rational design of a biosensor based on
shifts in the local surface plasmon resonance (LSPR) of
individual gold nanoparticles. The model relates the peak
wavelength of light scattered by an individual plasmonic
nanoparticle to the number of bound analyte molecules and
provides an analytical formulation that predicts relevant
figures-of-merit of the sensor such as the molecular
detection limit (MDL) and dynamic range as a function of
nanoparticle geometry and detection system parameters. The
model calculates LSPR shifts for individual molecules bound
by a nanorod, so that the MDL is defined as the smallest
number of bound molecules that is measurable by the system,
and the dynamic range is defined as the maximum number of
molecules that can be detected by a single nanorod. This
model is useful because it will allow a priori design of an
LSPR sensor with figures-of-merit that can be optimized for
the target analyte. This model was used to design an LSPR
sensor based on biotin-functionalized gold nanorods that
offers the lowest MDL for this class of sensors. The model
predicts a MDL of 18 streptavidin molecules for this sensor,
which is in good agreement with experiments and estimates.
Further, we discuss how the model can be utilized to guide
the development of future generations of LSPR
biosensors.},
Key = {Nusz09}
}
@booklet{Wu09,
Author = {Y. Q. Wu and J. A. Mackay and J. R. Mcdaniel and A. Chilkoti and R. L. Clark},
Title = {Fabrication of Elastin-Like polypeptide Nanoparticles for
Drug Delivery by Electrospraying},
Journal = {Biomacromolecules},
Volume = {10},
Number = {1},
Pages = {19 -- 24},
Year = {2009},
Month = {January},
ISSN = {1525-7797},
Abstract = {The development of environmentally responsive drug carriers
requires new methods for assembling stimuli-responsive
nanoparticulates. This communication describes a novel
application of electrospray to construct bioresponsive
peptide-based particulates, which can encapsulate drugs.
These particles are composed from genetically engineered
elastin-like polypeptides (ELPs), a biodegradable,
biocompatible, and bioresponsive polymer. To generate
nanoparticles (300-400 nm in diameter), ELPs and drugs are
codissolved in organic solvent, accelerated across a voltage
gradient, dried by evaporation during transit, and collected
from a target surface. These findings indicate that particle
diameter, polydispersity, and morphology are strong
functions of the solvent concentration, spraying voltage,
and polymer molecular weight. Surprisingly, the loading of
drug at 20 w/w\% did not influence particle morphology;
furthermore, drug release from these particles correlated
with the pH-dependent solubility of the parent ELPs. These
studies suggest that electrospray is an efficient and
flexible method for generating stimuli-responsive drug
particles.},
Key = {Wu09}
}
@booklet{Kim08,
Author = {B. Kim and A. Chilkoti},
Title = {Allosteric Actuation of Inverse Phase Transition of a
Stimulus-Responsive Fusion Polypeptide by Ligand
Binding},
Journal = {Journal Of The American Chemical Society},
Volume = {130},
Number = {52},
Pages = {17867 -- 17873},
Year = {2008},
Month = {December},
ISSN = {0002-7863},
Abstract = {We report herein a biopolymer actuator with a modular design
that allosterically transduces ligand binding into an
aqueous demixing phase transition. The biopolymer actuator
consists of two modular domains: a ligand binding protein
domain, calmodulin (CaM), that is fused to a transducer
domain, a stimulus-responsive elastin-like polypeptide (ELP)
that exhibits a reversible lower critical solution
temperature (LCST) phase transition. We demonstrate that
binding of calcium to CaM spontaneously triggers the phase
transition of the attached ELP, leading to formation of
meso-microscale particles depending on the chain length of
the ELP. This behavior is reversible as chelation of the
bound calcium results in dissolution of the assembled
particles, is selective for calcium as opposed to magnesium,
and is abolished by the binding of a peptide ligand that is
specific to calcium-bound CaM. These results are, to our
knowledge, the first demonstration of biomolecular
recognition-triggered, allosteric regulation of the LCST
phase transition of a polymer and are significant because
they expand the available triggers of the LCST transition of
stimulus-responsive polymers to biochemical ligand binding.
The ability to allosterically trigger the LCST transition of
ELPs by biomolecular recognition will be useful for
developing "smart" polymer actuators that capitalize upon
the myriad ligand-protein pairs that are available from
biology and for application in the design of selective
pull-down assays in proteomics, drug delivery, and nanoscale
biomolecular devices.},
Key = {Kim08}
}
@booklet{Cho08,
Author = {Y. H. Cho and Y. J. Zhang and T. Christensen and L. B. Sagle and A. Chilkoti and P. S. Cremer},
Title = {Effects of Hofmeister Anions on the Phase Transition
Temperature of Elastin-like Polypeptides},
Journal = {Journal Of Physical Chemistry B},
Volume = {112},
Number = {44},
Pages = {13765 -- 13771},
Year = {2008},
Month = {November},
ISSN = {1520-6106},
Abstract = {The modulation of the lower critical solution temperature
(LCST) of two elastin-like polypeptides (ELPs) was
investigated in the presence of 11 sodium salts that span
the Hoftneister series for anions. It was found that the
hydrophobic collapse/aggregation of these ELPs generally
followed the series. Specifically, kosmotropic anions
decreased the LCST by polarizing interfacial water molecules
involved in hydrating amide groups on the ELPs. On the other
hand, chaotropic anions lowered the LCST through a surface
tension effect. Additionally, chaotropic anions showed
salting-in properties at low salt concentrations that were
related to the saturation binding of anions with the
biopolymers. These overall mechanistic effects were similar
to those previously found for the hydrophobic collapse and
aggregation of poly(N-isopropylacrylamide), PNIPAM. There
is, however, a crucial difference between PNIPAM and ELPs.
Namely, PNIPAM undergoes a two-step collapse process as a
function of temperature in the presence of sufficient
concentrations of kosmotropic salts. By contrast, ELPs
undergo collapse in a single step in all cases studied
herein. This suggests that the removal of water molecules
from around the amide moieties triggers the removal of
hydrophobic hydration waters in a highly coupled process.
There are also some key differences between the LCST
behavior of the two ELPs. Specifically, the more hydrophilic
ELP V(5)A(2)G(3)-120 construct displays collapse/aggregation
behavior that is consistent with a higher concentration of
anions partitioning to polymer/aqueous interface as compared
to the more hydrophobic ELP V-5-120. It was also found that
larger anions could bind with ELP V(5)A(2)G(3)-120 more
readily in comparison with ELP V-5-120. These latter results
were interpreted in terms of relative binding site
accessibility of the anion for the ELP.},
Key = {Cho08}
}
@booklet{Xu08,
Author = {F. Xu and H. M. Joon and K. Trabbic-carlson and A. Chilkoti and W. Knoll},
Title = {Surface plasmon optical study of the interfacial phase
transition of elastinlike polypeptide grafted on
gold},
Journal = {Biointerphases},
Volume = {3},
Number = {3},
Pages = {66 -- 74},
Year = {2008},
Month = {September},
ISSN = {1559-4106},
Abstract = {The conformational changes in elastinlike polypeptides
(ELPs) grafted to a solid/solution interface via different
architectures were studied using surface plasmon resonance
spectroscopy and surface plasmon field-enhanced fluorescence
spectroscopy (SPFS). SPFS provides a simple and convenient
optical method to study the influence of the grafting method
and the graft density on the conformational changes in ELPs
at the solid-solution interface as a function of
environmental variables. A typical response of the ELP,
consistent with its stimuli responsiveness, was a gradual
collapse upon increasing the ionic strength; this effect was
inversely correlated with the surface graft density of the
ELP. (C) 2008 American Vacuum Society. [DOI:
10.1116/1.2965133]},
Key = {Xu08}
}
@booklet{Chow08,
Author = {D. Chow and M. L. Nunalee and D. W. Lim and A. J. Simnick and A. Chilkoti},
Title = {Peptide-based biopolymers in biomedicine and
biotechnology},
Journal = {Materials Science \& Engineering R-reports},
Volume = {62},
Number = {4},
Pages = {125 -- 155},
Year = {2008},
Month = {September},
ISSN = {0927-796X},
Abstract = {Peptides are emerging as a new class of biomaterials due to
their unique chemical, physical, and biological properties.
The development of peptide-based biomaterials is driven by
the convergence of protein engineering and macromolecular
self-assembly. This review covers the basic principles,
applications, and prospects of peptide-based biomaterials.
We focus on both chemically synthesized and genetically
encoded peptides, including poly-amino acids, elastin-like
polypeptides, silk-like polymers, and other biopolymers
based on repetitive peptide motifs. Applications of these
engineered biomolecules in protein purification, controlled
drug delivery, tissue engineering, and biosurface
engineering are discussed. (C) 2008 Elsevier B.V. All rights
reserved.},
Key = {Chow08}
}
@booklet{Mock08,
Author = {J. J. Mock and R. T. Hill and A. Degiron and S. Zauscher and A. Chilkoti and D. R. Smith},
Title = {Distance-dependent plasmon resonant coupling between a gold
nanoparticle and gold film},
Journal = {Nano Letters},
Volume = {8},
Number = {8},
Pages = {2245 -- 2252},
Year = {2008},
Month = {August},
ISSN = {1530-6984},
Abstract = {We present an experimental analysis of the plasmonic
scattering properties of gold nanoparticles controllably
placed nanometers away from a gold metal film. We show that
the spectral response of this system results from the
interplay between the localized plasmon resonance of the
nanoparticle and the surface plasmon polaritons of the gold
film, as previously predicted by theoretical studies. In
addition, we report that the metal film induces a
polarization to the single nanoparticle light scattering,
resulting in a doughnut-shaped point spread function when
imaged in the far-field. Both the spectral response and the
polarization effects are highly sensitive to the
nanoparticle-film separation distance. Such a system shows
promise in potential biometrology and diagnostic
devices.},
Key = {Mock08}
}
@booklet{Valiaev08,
Author = {A. Valiaev and D. W. Lim and S. Schmidler and R. L. Clark and A. Chilkoti and S. Zauscher},
Title = {Hydration and conformational mechanics of single,
end-tethered elastin-like polypeptides},
Journal = {Journal Of The American Chemical Society},
Volume = {130},
Number = {33},
Pages = {10939 -- 10946},
Year = {2008},
Month = {August},
ISSN = {0002-7863},
Abstract = {We investigated the effect of temperature, ionic strength,
solvent polarity, and type of guest residue on the
force-extension behavior of single, end-tethered
elastin-like polypeptides (ELPs), using single molecule
force spectroscopy (SMFS). ELPs are stimulus-responsive
polypeptides that contain repeats of the five amino acids
Val-Pro-Gly-Xaa-Gly (VPGXG), where Xaa is a guest residue
that can be any amino acid with the exception of proline. We
fitted the force-extension data with a freely jointed chain
(FJC) model which allowed us to resolve small differences in
the effective Kuhn segment length distributions that largely
arise from differences in the hydrophobic hydration behavior
of ELP. Our results agree qualitatively with predictions
from recent molecular dynamics simulations and demonstrate
that hydrophobic hydration modulates the molecular
elasticity for ELPs. Furthermore, our results show that
SMFS, when combined with our approach for data analysis, can
be used to study the subtleties of polypeptide-water
interactions and thus provides a basis for the study of
hydrophobic hydration in intrinsically unstructured
biomacromolecules.},
Key = {Valiaev08}
}
@booklet{Shamji08,
Author = {M. F. Shamji and J. Chen and A. H. Friedman and W. J.
Richardson and A. Chilkoti and L. A. Setton},
Title = {Synthesis and characterization of a thermally-responsive
tumor necrosis factor antagonist},
Journal = {Journal Of Controlled Release},
Volume = {129},
Number = {3},
Pages = {179 -- 186},
Year = {2008},
Month = {August},
ISSN = {0168-3659},
Abstract = {Numerous antagonists of tumor necrosis factor alpha (TNF
alpha) have been developed to attenuate inflammation and
accompanying pain in many disease processes. Soluble TNF
receptor type II (sTNFRII) is one such antagonist that
sequesters TNF alpha away from target receptors and
attenuates its activity. Systemic delivery of soluble TNF
receptors or other antagonists may have deleterious side
effects associated with immune suppression, so that
strategies for locally targeted drug delivery are of
interest. Elastin-like polypeptides (ELPs) are biopolymers
capable of in situ drug depot formation through
thermally-driven supramolecular complexes at physiological
temperatures. A recombinant fusion protein between ELP and
sTNFRII was designed and evaluated for retention of bivalent
functionality. Thermal sensitivity was observed by formation
of supramolecular submicron-sized particles at 32 degrees C,
with gradual resolubilization from the depot observed at
physiological temperatures. In vitro refolding of the
sTNFRII domain was required and the purified product
exhibited an equilibrium dissociation constant for
interacting with TNF alpha that was seven-fold higher than
free sTNFRII Furthermore, anti-TNF activity was observed in
inhibiting TNR alpha-mediated cytotoxicity in the murine
L929 fibrosarcoma assay. Potential advantages of this
ELP-sTNFRII fusion protein as an anti-TNFa drug depot
include facility of injection, in situ depot formation, low
endotoxin content, and functionality against TNF alpha. (C)
2008 Elsevier B.V. All rights reserved.},
Key = {Shamji08}
}
@booklet{Nettles08,
Author = {D. L. Nettles and K. Kitaoka and N. A. Hanson and C. M.
Flahiff and B. A. Mata and E. W. Hsu and A. Chilkoti and L.
A. Setton},
Title = {In situ crosslinking elastin-like polypeptide gels for
application to articular cartilage repair in a goat
osteochondral defect model},
Journal = {Tissue Engineering Part A},
Volume = {14},
Number = {7},
Pages = {1133 -- 1140},
Year = {2008},
Month = {July},
ISSN = {1937-3341},
Abstract = {The objective of this study was to evaluate an injectable,
in situ crosslinkable elastin-like polypeptide (ELP) gel for
application to cartilage matrix repair in critically sized
defects in goat knees. One cylindrical, osteochondral defect
in each of seven animals was filled with an aqueous solution
of ELP and a biocompatible, chemical crosslinker, while the
contralateral defect remained unfilled and served as an
internal control. Joints were sacrificed at 3 (n=3) or 6
(n=4) months for MRI, histological, and gross evaluation of
features of biomaterial performance, including integration,
cellular infiltration, surrounding matrix quality, and new
matrix in the defect. At 3 months, ELP-filled defects scored
significantly higher for integration by histological and
gross grading compared to unfilled defects. ELP did not
impede cell infiltration but appeared to be partly degraded.
At 6 months, new matrix in unfilled defects outpaced that in
ELP-filled defects and scored significantly better for MRI
evidence of adverse changes, as well as integration and
proteoglycan-containing matrix via gross and histological
grading. The ELP-crosslinker solution was easily delivered
and formed stable, well-integrated gels that supported cell
infiltration and matrix synthesis; however, rapid
degradation suggests that ELP formulation modifications
should be optimized for longer-term benefits in cartilage
repair applications.},
Key = {Nettles08}
}
@booklet{Shamji08a,
Author = {M. F. Shamji and L. Whitlatch and A. H. Friedman and W. J.
Richardson and A. Chilkoti and L. A. Setton},
Title = {An injectable and in situ-gelling biopolymer for sustained
drug release following perineural administration},
Journal = {Spine},
Volume = {33},
Number = {7},
Pages = {748 -- 754},
Year = {2008},
Month = {April},
ISSN = {0362-2436},
Abstract = {Study Design. This study evaluated whether the aggregation
behavior of a thermally responsive elastin-like polypeptide
(ELP) prolongs protein residence time at the dorsal root
ganglion (DRG). This work involves development of a
sustained-release drug delivery vehicle to provide high and
sustained levels of biologic therapeutics to the dorsal root
ganglion while minimizing systemic exposure. Objective. To
study the potential of the ELP biopolymer to sustain release
and lower systemic exposure of bioactive peptides following
perineural administration. Summary of Background Data.
Anticytokine treatment for lumbar radiculopathy may offer
clinical improvement, but exposes patients to systemic
toxicities of immunosuppression. ELPs are environmentally
responsive polypeptides that undergo a phase transition on
heating to form an insoluble aggregate. Drug conjugates with
ELP exhibit both temperature-sensitivity and in vitro
bioactivity. Monomer resolubilization yields solution-phase
molecules, and this reversible aggregation behavior may
create a perineural drug depot to sustain drug delivery to
an inflamed nerve. Methods. This experiment involved 48 rats
in which radiolabeled ELPs (aggregating or soluble) were
injected overlying the L5 dorsal root ganglion. Animals were
killed at 6 different time points, and radioactivity
associated with the injected segment, serum, and other
tissues was evaluated. Results. The aggregating ELP
demonstrated a 7-fold longer perineural half-life compared
with the soluble ELP. This supports the hypothesis that the
aggregating ELP forms a depot from which slow
resolubilization and clearance provides sustained, local
protein release. Furthermore, serum radioactivity reached a
lower peak for the aggregating group, demonstrating slower
absorption of the aggregating protein into the systemic
circulation. Conclusion. These results suggest that ELP
aggregation confer the benefit of perineural compartment
longevity for bioactive therapeutics delivered fused with
this carrier. This may sustain release of potent
immunomodulator therapeutics to treat local
neuroinflammation. Desirable features include delivery of
high local doses and protection against systemic exposure
and associated toxicity.},
Key = {Shamji08a}
}
@booklet{Nusz08,
Author = {G. J. Nusz and S. M. Marinakos and A. C. Curry and A. Dahlin and F. Hook and A. Wax and A. Chilkoti},
Title = {Label-free plasmonic detection of biomolecular binding by a
single gold nanorod},
Journal = {Analytical Chemistry},
Volume = {80},
Number = {4},
Pages = {984 -- 989},
Year = {2008},
Month = {February},
ISSN = {0003-2700},
Abstract = {We report the use of individual gold nanorods as plasmonic
transducers to detect the binding of streptavidin to
individual biotin-conjugated nanorods in real time on a
surface. Label-free detection at the single-nanorod level
was performed by tracking the wavelength shift of the
nanorod-localized surface plasmon resonant scattering
spectrum using a dark-field microspectroscopy system. The
lowest streptavidin concentration that was experimentally
measured was 1 nM, which is a factor of 1000-fold lower than
the previously reported detection limit for streptavidin
binding by biotinylated single plasmonic nanostructures. We
believe that the current optical setup is able to reliably
measure wavelength shifts as small as 0.3 nm. Binding of
streptavidin at 1 nM concentration induces a mean resonant
wavelength shift of 0.59 nm suggesting that we are currently
operating at close to the limit of detection of the
system.},
Key = {Nusz08}
}
@booklet{Lim08,
Author = {D. W. Lim and D. L. Nettles and L. A. Setton and A.
Chilkoti},
Title = {In situ cross-linkinig of elastin-like polypeptide block
copolymers for tissue repair},
Journal = {Biomacromolecules},
Volume = {9},
Number = {1},
Pages = {222 -- 230},
Year = {2008},
Month = {January},
ISSN = {1525-7797},
Abstract = {Rapid cross-linking of elastin-like polypeptides (ELPs) with
hydroxymethylphosphines (HMPs) in aqueous solution is
attractive for minimally invasive in vivo implantation of
biomaterials and tissue engineering scaffolds. In order to
examine the independent effect of the location and number of
reactive sites on the chemical cross-linking kinetics of
ELPs and the mechanical properties of the resulting
hydrogels, we have designed ELP block copolymers comprised
of cross-linkable, hydrophobic ELP blocks with periodic Lys
residues (A block) and aliphatic, hydrophilic ELP blocks
with no cross-linking sites (B block); three different block
architectures, A, ABA, and BABA were synthesized in this
study. All ELP block copolymers were rapidly cross-linked
with HMPs within several minutes under physiological
conditions. The inclusion of the un-cross-linked hydrophilic
block, its length relative to the cross-linkable hydrophobic
block, and the block copolymer architecture all had a
significant effect on swelling ratios of the cross-linked
hydrogels, their microstructure, and mechanical properties.
Fibroblasts embedded in the ELP hydrogels survived the
cross-linking process and remained viable for at least 3
days in vitro when the gels were formed from an equimolar
ratio of HMPs and Lys residues of ELPs. DNA quantification
of the embedded cells indicated that the cell viability
within triblock ELP hydrogels was statistically greater than
that in the monoblock gels at day 3. These results suggest
that the mechanical properties of ELP hydrogels and the
microenvironment that they present to cells can be tuned by
the design of the block copolymer architecture.},
Key = {Lim08}
}
@booklet{Dreher08,
Author = {M. R. Dreher and A. J. Simnick and K. Fischer and R. J.
Smith and A. Patel and M. Schmidt and A.
Chilkoti},
Title = {Temperature triggered self-assembly of polypeptides into
multivalent spherical micelles},
Journal = {Journal Of The American Chemical Society},
Volume = {130},
Number = {2},
Pages = {687 -- 694},
Year = {2008},
Month = {January},
ISSN = {0002-7863},
Abstract = {We report herein thermally responsive elastin-like
polypeptides (ELPs) in a linear AB diblock architecture with
an N-terminal peptide ligand that self-assemble into
spherical micelles when heated slightly above body
temperature. A series of 10 ELP block copolymers (ELPBC's)
with different molecular weights and hydrophilic-to-hydrophobic
block ratios were genetically synthesized by recursive
directional ligation. The self-assembly of these polymers
from unimers into micelles was investigated by light
scattering, fluorescence spectroscopy, and cryo-TEM. These
ELPBC's undergo two phase transitions as a function of
solution temperature: a unimer-to-spherical micelle
transition at an intermediate temperature and a
micelle-to-bulk aggregate transition at a higher temperature
when the. hydrophilic-to-hydrophobic block ratio is between
1:2 and 2:1. The critical micelle temperature is controlled
by the length of the hydrophobic block, and the size of the
micelle is controlled by both the total ELPBC length and
hydrophilic-to-hydrophobic block ratio. These polypeptide
micelles display a critical micelle concentration in the
range 4-8 mu M demonstrating the high stability of these
structures. These studies have also identified a subset of
ELPBC's bearing terminal peptide ligands that are capable of
forming multivalent spherical micelles that present multiple
copies of the ligand on their corona in the clinically
relevant temperature range 37-42 degrees C and target cancer
cells. These ELPBC's may be useful for drug targeting" by
thermally triggered multivalency. More broadly, the design
rules uncovered by this study should be applicable to the
design of other thermally reversible nanoparticles for
diverse applications in medicine and biology.},
Key = {Dreher08}
}
@booklet{Mackay08,
Author = {J. A. Mackay and A. Chilkoti},
Title = {Temperature sensitive peptides: Engineering
hyperthermia-directed therapeutics},
Journal = {International Journal Of Hyperthermia},
Volume = {24},
Number = {6},
Pages = {483 -- 495},
Year = {2008},
ISSN = {0265-6736},
Abstract = {Purpose. Recent progress suggests that short peptide motifs
can be engineered into biopolymers with specific temperature
dependent behavior. This review discusses peptide motifs
capable of thermo-responsive behavior, and broadly
summarizes design approaches that exploit these peptides as
drug carriers. This review focuses on one class of thermally
responsive peptide-based biopolymers, elastin-like
polypeptides in greater detail. Analysis. Four peptide
motifs are presented based on leucine zippers, human
collagen, human elastin, and silkworm silk that are
potential building blocks for thermally responsive
biopolymers. When these short motifs (7 amino acids) are
repeated many times, they generate biopolymers with higher
order structure and complex temperature triggered behaviors.
These structures are thermodynamically modulated, making
them intrinsically temperature sensitive. These four motifs
can be categorized by the directionality and reversibility
of association. Elastin-like polypeptides (ELPs) are one
promising motif that reversibly associates during heating.
ELPs aggregate sharply above an inverse phase transition
temperature, which depends on polymer hydrophobicity,
molecular weight, and concentration. ELPs can be modified
with chemotherapeutics, are biodegradable, are
biocompatible, have low immunogenicity, and have terminal
pharmacokinetic half-lives 8 h. ELP block copolymers can
reversibly form micelles in response to hyperthermia, and
this behavior can modulate the binding avidity of peptide
ligands. When high molecular weight ELPs are systemically
administered to mice they accumulate in tumors; furthermore,
hyperthermia can initiate the ELP phase transition and
double the concentration of peptide in the tumor.
Conclusions. Temperature sensitive peptides are a powerful
engineering platform that will enable new strategies for
hyperthermia-directed drug delivery.},
Key = {Mackay08}
}
@booklet{Pyhtila06,
Author = {J. W. Pyhtila and H. W. Ma and A. J. Simnick and A. Chilkoti and A. Wax},
Title = {Analysis of long range correlations due to coherent light
scattering from in-vitro cell arrays using angle-resolved
low coherence interferometry},
Journal = {Journal Of Biomedical Optics},
Volume = {11},
Number = {3},
Year = {2006},
ISSN = {1083-3668},
Abstract = {Angle-resolved low coherence interferometry (a/LCl) enables
depth-resolved measurements of scattered light that can be
used to recover subsurface structural information, such as
the size of cell nuclei. Measurements of nuclear morphology,
however, can be complicated by coherent scattering between
adjacent cell nuclei. Previous studies have eliminated this
component by applying a window filter to Fourier transformed
angular data, based on the justification that the coherent
scattering must necessarily occur over length scales greater
than the cell size. To fully study this effect, results of
experiments designed to test the validity of this approach
are now presented. The a/LCl technique is used to examine
light scattered by regular cell arrays, created using
stamped adhesive micropatterned substrates. By varying the
array spacing, it is demonstrated that cell-to-cell
correlations have a predictable effect on light scattering
distributions. These results are compared to image analysis
of fluorescence micrographs of the cell array samples. The
a/LCI results show that the impact of coherent scattering on
nuclear morphology measurements can be eliminated through
data filtering. (c) 2006 Society of Photo-Optical
Instrumentation Engineers.},
Key = {Pyhtila06}
}
@article{4003475,
Author = {Leggett, G.J. and Chilkoti, A. and Castner, D.G. and Ratner,
B.D. and Vickerman, J.C.},
Title = {Direct emission of molecular fragments during the sputtering
of poly(4-hydroxystyrene) and determination of ion
structures using tandem secondary ion mass
spectrometry},
Journal = {Int. J. Mass Spectrom. Ion Process. (Netherlands)},
Volume = {108},
Number = {1},
Pages = {29 - 39},
Year = {2},
url = {http://dx.doi.org/10.1016/0168-1176(91)87004-K},
Keywords = {polymers;secondary ion mass spectra;sputtering;},
Abstract = {Poly(4-hydroxystyrene) (P4HS) has been studied using a
tandem secondary ion mass spectrometer under static
conditions. The secondary ion mass spectrometry (SIMS)
spectrum of P4HS exhibits few ions which are not observed in
the SIMS spectrum of polystyrene. The fragmentation of these
oxygen-containing ions has been investigated in detail and
the relevant neutral losses have been deduced. These ions
are found to have structures based upon either the
tropyllium ion or the styrene ion. The absence of other
oxygen-containing ions is explained in terms of the ready
loss of oxygen-containing neutral fragments from P4HS
compared with the loss of hydrocarbon fragments. The
oxygen-containing tropyllium and styrene ions are, in
contrast, readily formed, and in these cases the energy
barrier to formation of the oxygen-containing ion is less
than the energy barrier to expulsion of oxygen-containing
neutral species},
Key = {4003475}
}
%% Clark, Robert L
@booklet{Wulff08,
Author = {K. D. Wulff and D. G. Cole and R. L. Clark},
Title = {An adaptive system identification approach to optical trap
calibration},
Journal = {Optics Express},
Volume = {16},
Number = {7},
Pages = {4420 -- 4425},
Year = {2008},
Month = {March},
ISSN = {1094-4087},
Key = {Wulff08}
}
@booklet{Wu08,
Author = {Y. Q. Wu and M. S. Johannes and R. L. Clark},
Title = {AFM-based voltage assisted nanoelectro spinning},
Journal = {Materials Letters},
Volume = {62},
Number = {4-5},
Pages = {699 -- 702},
Year = {2008},
Month = {February},
ISSN = {0167-577X},
Key = {Wu08}
}
@article{fds146110,
Author = {Cox, D.E. and G. P. Gibs and R.L. Clark and J.S.
Vipperman},
Title = {Experimental Robust Control of Structural Acoustic
Control},
Journal = {ASME Journal of Vibration and Acoustics},
Volume = {121},
Number = {4},
Pages = {433-440},
Year = {2008},
Key = {fds146110}
}
@article{fds146106,
Author = {Ma, H. and M. Textor and R.L. Clark and A. Chilkoti},
Title = {Real time monitoring of surface initiated atom transfer
radical polymerization by quartz crystal microbalance with
dissipation},
Journal = {Biointerphases},
Volume = {1},
Number = {35-39},
Year = {2008},
Key = {fds146106}
}
@article{fds146107,
Author = {Chow, D.C. and M.S. Johannes and W. Lee and R.L. Clark and S. Zauscher and A. Chilkoti},
Title = {Nanofabrication with biomolecules},
Journal = {Materials Today},
Volume = {8},
Number = {Suppl 1},
Pages = {30-39},
Year = {2008},
Key = {fds146107}
}
@article{fds146108,
Author = {Henry, James K. and R.L. Clark},
Title = {Active control of sound transmission through a curved panel
into a cylindrical enclosure},
Journal = {Journal of Sound and Vibration},
Volume = {249},
Number = {2},
Pages = {325-349},
Year = {2008},
Key = {fds146108}
}
@article{fds146104,
Author = {Wu, Y.Q. and R.L. Clark},
Title = {Electrohydrodynamic atomization: a versatile process for
preparing materials for biomedical applications},
Journal = {J. Biomater. Sci. Polymer Edn.},
Volume = {19},
Number = {5},
Pages = {573-601},
Year = {2008},
Key = {fds146104}
}
@article{fds146109,
Author = {Lane, Steven A. and R.L. Clark and Southward, Steven
C.},
Title = {Active Control of Low Frequency Modes in an Aircraft
Fuselage Using Spatially Weighted Arrays},
Journal = {ASME Journal of Vibration and Acoustics},
Volume = {123},
Number = {3},
Pages = {227-234},
Year = {2008},
Key = {fds146109}
}
@article{fds146105,
Author = {serpe, M.J. and Rivera, M. and Kersey, F.R. and R.L. Clark and S.L.
Craig},
Title = {Time and distance dependence of reversible polymer bridging
followed by single molecule force spectroscopy},
Journal = {Langmuir},
Volume = {24},
Number = {9},
Pages = {4738-4742},
Year = {2008},
Key = {fds146105}
}
@article{fds146113,
Author = {R.L. Clark and Saunders, W.R.},
Title = {An intelligent systems approach to active structural
acoustic control},
Journal = {1993 Transactions of the SAE},
Year = {2008},
Key = {fds146113}
}
@article{fds146114,
Author = {Clark, R. L. and Burdisso, R. A. and Fuller,
C.R.},
Title = {Design approaches for shaping polyvinylidene fluoride
sensors in active structural acoustic control},
Journal = {Journal of Intelligent Materials Systems and
Structures},
Volume = {1993},
Number = {4},
Pages = {354-365},
Year = {2008},
Key = {fds146114}
}
@article{fds146115,
Author = {Clark, R.L. and Fuller C.R.},
Title = {Active Structural Acoustic Control with Adaptive Structures
Including Wavenumber Considerations},
Journal = {Journal of Intelligent Systems and Structures},
Volume = {3},
Number = {2},
Pages = {296-315},
Year = {2008},
Key = {fds146115}
}
@article{fds146116,
Author = {Snyder, S. D. and R.L. Clark and Hansen, D.
H.},
Title = {Convergence Characteristics of the Multiple Input, Multiple
Output LMS Algorithm},
Journal = {Journal of Intelligent Materials Systems and
Structures},
Volume = {3},
Number = {1},
Pages = {115-133},
Year = {2008},
Key = {fds146116}
}
@article{fds146117,
Author = {Clark, R. L. and Fuller, C. R. and Wicks, A.},
Title = {Control of Sound Radiation with Adaptive
Structures},
Journal = {Juornal of the Acoustical Society of America},
Volume = {2},
Number = {3},
Pages = {431-452},
Year = {2008},
Key = {fds146117}
}
@booklet{Mcever07,
Author = {M. A. Mcever and E. V. Ardelean and D. G. Cole and R. L.
Clark},
Title = {Active control and closed-loop identification of flutter
instability in typical section airfoil},
Journal = {Journal Of Guidance Control And Dynamics},
Volume = {30},
Number = {3},
Pages = {733 -- 740},
Year = {2007},
ISSN = {0731-5090},
Key = {Mcever07}
}
@booklet{Ardelean06,
Author = {E. V. Ardelean and M. A. Mcever and D. G. Cole and R. L.
Clark},
Title = {Active flutter control with V-stack piezoelectric flap
actuator},
Journal = {Journal Of Aircraft},
Volume = {43},
Number = {2},
Pages = {482 -- 486},
Year = {2006},
ISSN = {0021-8669},
Key = {Ardelean06}
}
@booklet{Dowell03,
Author = {E. H. Dowell and D. B. Bliss and R. L. Clark},
Title = {Aeroelastic wing with leading- and trailing-edge control
surfaces},
Journal = {Journal Of Aircraft},
Volume = {40},
Number = {3},
Pages = {559 -- 565},
Year = {2003},
ISSN = {0021-8669},
Key = {Dowell03}
}
@booklet{Clark01,
Author = {R. L. Clark},
Title = {Adaptive structures: Compensators by design},
Journal = {Noise Control Engineering Journal},
Volume = {49},
Number = {1},
Pages = {15 -- 20},
Year = {2001},
ISSN = {0736-2501},
Key = {Clark01}
}
@booklet{Rule01,
Author = {J. A. Rule and R. E. Richard and R. L. Clark},
Title = {Design of an aeroelastic delta wing model for active flutter
control},
Journal = {Journal Of Guidance Control And Dynamics},
Volume = {24},
Number = {5},
Pages = {918 -- 924},
Year = {2001},
ISSN = {0731-5090},
Key = {Rule01}
}
@booklet{Lane01,
Author = {S. A. Lane and J. D. Kemp and S. Griffin and R. L.
Clark},
Title = {Active acoustic control of a rocket fairing using spatially
weighted transducer arrays},
Journal = {Journal Of Spacecraft And Rockets},
Volume = {38},
Number = {1},
Pages = {112 -- 119},
Year = {2001},
ISSN = {0022-4650},
Key = {Lane01}
}
@booklet{Frampton00,
Author = {K. D. Frampton and R. L. Clark},
Title = {Experiments on control of limit-cycle oscillations in a
typical section},
Journal = {Journal Of Guidance Control And Dynamics},
Volume = {23},
Number = {5},
Pages = {956 -- 960},
Year = {2000},
ISSN = {0731-5090},
Key = {Frampton00}
}
@booklet{Clark00,
Author = {R. L. Clark and D. E. Cox},
Title = {Multi-input, multi-output, band-limited transducer selection
for disturbance rejection},
Journal = {Journal Of Guidance Control And Dynamics},
Volume = {23},
Number = {5},
Pages = {903 -- 906},
Year = {2000},
ISSN = {0731-5090},
Key = {Clark00}
}
@booklet{Clark00b,
Author = {R. L. Clark and E. H. Dowell and K. D. Frampton},
Title = {Control of a three-degree-of-freedom airfoil with
limit-cycle behavior},
Journal = {Journal Of Aircraft},
Volume = {37},
Number = {3},
Pages = {533 -- 536},
Year = {2000},
ISSN = {0021-8669},
Key = {Clark00b}
}
@booklet{Smith00a,
Author = {G. C. Smith and R. L. Clark},
Title = {Technical note: Performance measures for active control;
passive insertion loss (PIL), active insertion loss (AIL),
and total insertion loss (TIL)},
Journal = {Noise Control Engineering Journal},
Volume = {48},
Number = {2},
Pages = {67 -- 69},
Year = {2000},
ISSN = {0736-2501},
Key = {Smith00a}
}
@booklet{Vipperman99a,
Author = {J. S. Vipperman and J. M. Barker and R. L. Clark and G. J.
Balas},
Title = {Comparison of mu- and H-2-synthesis controllers on an
experimental typical section},
Journal = {Journal Of Guidance Control And Dynamics},
Volume = {22},
Number = {2},
Pages = {278 -- 285},
Year = {1999},
ISSN = {0731-5090},
Key = {Vipperman99a}
}
@booklet{Clark99a,
Author = {R. L. Clark and D. E. Cox},
Title = {Band-limited actuator and sensor selection for disturbance
rejection},
Journal = {Journal Of Guidance Control And Dynamics},
Volume = {22},
Number = {5},
Pages = {740 -- 743},
Year = {1999},
ISSN = {0731-5090},
Key = {Clark99a}
}
@booklet{Vipperman98,
Author = {J. S. Vipperman and R. L. Clark and M. Conner and E. H.
Dowell},
Title = {Experimental active control of a typical section using a
trailing-edge flap},
Journal = {Journal Of Aircraft},
Volume = {35},
Number = {2},
Pages = {224 -- 229},
Year = {1998},
ISSN = {0021-8669},
Key = {Vipperman98}
}
@booklet{Frampton96b,
Author = {K. D. Frampton and R. L. Clark and E. H.
Dowell},
Title = {State-space modeling for aeroelastic panels with linearized
potential flow aerodynamic loading},
Journal = {Journal Of Aircraft},
Volume = {33},
Number = {4},
Pages = {816 -- 822},
Year = {1996},
ISSN = {0021-8669},
Key = {Frampton96b}
}
@booklet{Frampton96a,
Author = {K. D. Frampton and R. L. Clark and E. H.
Dowell},
Title = {Active control of panel flutter with piezoelectric
transducers},
Journal = {Journal Of Aircraft},
Volume = {33},
Number = {4},
Pages = {768 -- 774},
Year = {1996},
ISSN = {0021-8669},
Key = {Frampton96a}
}
%% Collins, Leslie M
@booklet{Stohl09,
Author = {J. S. Stohl and C. S. Throckmorton and L. M.
Collins},
Title = {Investigating the effects of stimulus duration and context
on pitch perception by cochlear implant users},
Journal = {Journal Of The Acoustical Society Of America},
Volume = {126},
Number = {1},
Pages = {318 -- 326},
Year = {2009},
Month = {July},
ISSN = {0001-4966},
Abstract = {Cochlear implant sound processing strategies that use
time-varying pulse rates to transmit fine structure
information are one proposed method for improving the
spectral representation of a sound with the eventual goal of
improving speech recognition in noisy conditions, speech
recognition in tonal languages, and music identification and
appreciation. However, many of the perceptual phenomena
associated with time-varying rates are not well understood.
In this study, the effects of stimulus duration on both the
place and rate-pitch percepts were investigated via
psychophysical experiments. Four Nucleus CI24 cochlear
implant users participated in these experiments, which
included a short-duration pitch ranking task and three
adaptive pulse rate discrimination tasks. When duration was
fixed from trial-to-trial and rate was varied adaptively,
results suggested that both the place-pitch and rate-pitch
percepts may be independent of duration for durations above
10 and 20 ms, respectively. When duration was varied and
pulse rates were fixed, performance was highly variable
within and across subjects. Implications for multi-rate
sound processing strategies are discussed.},
Key = {Stohl09}
}
@booklet{Tantum09,
Author = {S. L. Tantum and Q. Zhu and P. A. Torrione and L. M.
Collins},
Title = {Modeling position error probability density functions for
statistical inversions using a Goff-Jordan rough surface
model},
Journal = {Stochastic Environmental Research And Risk
Assessment},
Volume = {23},
Number = {2},
Pages = {155 -- 167},
Year = {2009},
Month = {February},
ISSN = {1436-3240},
Abstract = {Buried unexploded ordnance (UXO) continues to be a difficult
remediation problem from both a sensing and a discrimination
point of view. Modern approaches to both the sensing and
discrimination problems utilize high bandwidth
electromagnetic induction (EMI) sensors to collect
geo-referenced data which is then inverted, or fit, using a
forward model in order to obtain features that can be
directly interpreted using the physics associated with
electromagnetic induction-based sensing. These features are
then used in a variety of classification architectures. One
aspect of this process that has captured recent interest is
that uncertainty in the positions at which data was
collected can degrade the inversion performance and thus the
subsequent classification. Several mechanisms to address
this issue have been explored that range from filtering and
prediction of actual positions to exploiting Bayesian
approaches for uncertainty mitigation. In the Bayesian
approach, a statistical model of the position errors is used
as a prior for integrating over the uncertainty in the
inversion process. In this study, we demonstrate that errors
in the statistical priors used in this process can
negatively impact subsequent classification performance,
thus highlighting the need for an accurate statistical model
for the position errors. Next, we propose a mechanism by
which to obtain such models. Specifically, we utilize a
Goff-Jordan rough surface model and simulate the sensor data
collection system motion over the simulated ground or ocean
surfaces to calculate errors and generate statistical
models. Our results suggest that this approach can be used
to develop the statistical models necessary for mitigating
uncertain position information.},
Key = {Tantum09}
}
@booklet{Morton08,
Author = {K. D. Morton and P. A. Torrione and C. S. Throckmorton and L. M. Collins},
Title = {Mandarin Chinese tone identification in cochlear implants:
Predictions from acoustic models},
Journal = {Hearing Research},
Volume = {244},
Number = {1-2},
Pages = {66 -- 76},
Year = {2008},
Month = {October},
ISSN = {0378-5955},
Abstract = {It has been established that current cochlear implants do
not supply adequate spectral information for perception of
tonal languages. Comprehension of a tonal language, such as
Mandarin Chinese, requires recognition of lexical tones. New
strategies of cochlear stimulation such as variable
stimulation rate and current steering may provide the means
of delivering more spectral information and thus may provide
the auditory fine-structure required for tone recognition.
Several cochlear implant signal processing strategies are
examined in this study, the continuous interleaved sampling
(CIS) algorithm, the frequency amplitude modulation encoding
(FAME) algorithm, and the multiple carrier frequency
algorithm (MCFA). These strategies provide different types
and amounts of spectral information. Pattern recognition
techniques can be applied to data from Mandarin Chinese tone
recognition tasks using acoustic models as a means of
testing the abilities of these algorithms to transmit the
changes in fundamental frequency indicative of the four
lexical tones. The ability of processed Mandarin Chinese
tones to be correctly classified may predict trends in the
effectiveness of different signal processing algorithms in
cochlear implants. The proposed techniques can predict
trends in performance of the signal processing techniques in
quiet conditions but fail to do so in noise. (C) 2008
Elsevier B.V. All rights reserved.},
Key = {Morton08}
}
@booklet{Stohl08,
Author = {J. S. Stohl and C. S. Throckmorton and L. M.
Collins},
Title = {Assessing the pitch structure associated with multiple rates
and places for cochlear implant users},
Journal = {Journal Of The Acoustical Society Of America},
Volume = {123},
Number = {2},
Pages = {1043 -- 1053},
Year = {2008},
Month = {February},
ISSN = {0001-4966},
Abstract = {Cochlear implant subjects continue to experience difficulty
understanding speech in noise and performing pitch-based
musical tasks. Acoustic model studies have suggested that
transmitting additional fine structure via multiple
stimulation rates is a potential mechanism for addressing
these issues [Nie et al., IEEE Trans. Biomed. Eng. 52, 64-73
(2005); Throckmorton et al., Hear. Res. 218, 30-42 (2006)];
however, results from preliminary cochlear implant studies
have been less compelling. Multirate speech processing
algorithms previously assumed a place-dependent pitch
structure in that a basal electrode would always elicit a
higher pitch percept than an apical electrode, independent
of stimulation rate. Some subjective evidence contradicts
this assumption [H. J. McDermott and C. M. McKay, J. Acoust.
Soc. Am. 101, 1622-1630 (1997); R. V. Shannon, Hear. Res. 11
157-189 (1983)]. The purpose of this study is to test the
hypothesis that the introduction of multiple rates may
invalidate the tonotopic pitch structure resulting from
place-pitch alone. The SPEAR3 developmental speech processor
was used to collect psychophysical data from five cochlear
implant users to assess the tonotopic structure for stimuli
presented at two rates on all active electrodes. Pitch
ranking data indicated many cases where pitch percepts
overlapped across electrodes and rates. Thus, the results
from this study suggest that pitch-based tuning across rate
and electrode may be necessary to optimize performance of a
multirate sound processing strategy in cochlear implant
subjects. (c) 2008.},
Key = {Stohl08}
}
@booklet{Remus08,
Author = {J. J. Remus and L. M. Collins},
Title = {Comparison of adaptive psychometric procedures motivated by
the Theory of Optimal Experiments: Simulated and
experimental results},
Journal = {Journal Of The Acoustical Society Of America},
Volume = {123},
Number = {1},
Pages = {315 -- 326},
Year = {2008},
Month = {January},
ISSN = {0001-4966},
Abstract = {The wide use of psychometric assessments and the time
necessary to conduct comprehensive psychometric tests has
motivated significant research into the development of
psychometric testing procedures that will provide accurate
and efficient estimates of the parameters of interest. One
potential framework for developing adaptive psychometric
procedures is the Theory of Optimal Experiments. The Theory
of Optimal Experiments provides several metrics for
determining informative stimulus values based on a model of
the Psychometric function to be provided by the
investigator. In this study, two methods based on a previous
implementation of the Theory of Optimal Experiments are
presented for comparison to two fixed step size staircase
methods and also an existing adaptive method that utilizes a
Bayesian framework. The psychometric procedures were used to
measure detection thresholds and discrimination limens on
two separate psychoacoustic tasks with normal-hearing
subjects. Computer simulations were performed based on the
outcomes of the experimental psychoacoustic detection task
to analyze performance over a large sample size in the case
of known truth. Results suggest that the proposed stimulus
selection rules motivated by the Theory of Optimal
Experiments perform better than previous techniques and also
extend estimation to. multiple parameters. (c) 2008
Acoustical Society of America.},
Key = {Remus08}
}
@booklet{Tantum08,
Author = {S. L. Tantum and Y. L. Yu and L. M. Collins},
Title = {Bayesian mitigation of sensor position errors to improve
unexploded ordnance detection},
Journal = {Ieee Geoscience And Remote Sensing Letters},
Volume = {5},
Number = {1},
Pages = {103 -- 107},
Year = {2008},
Month = {January},
ISSN = {1545-598X},
Abstract = {Phenomenological modeling coupled with statistical signal
processing has been shown to significantly improve
capabilities for discriminating unexploded ordnance (UXO)
from benign clutter using electromagnetic induction (EMI)
sensor data. The general premise underlying the majority of
these coupled approaches is that a phenomenological model is
fit to the measured data, and the parameters estimated from
this model inversion, which characterize the interrogated
target, are utilized in subsequent statistical signal
processing algorithms to classify the target as either UXO
or clutter. A potential limitation of this coupled approach
is that the inversion has been shown to be sensitive to
uncertainty associated with the sensor positions. When the
measurement positions are uncertain, the inversion results
are more variable, and consequently, discrimination
performance degrades. In this letter, a Bayesian methodology
is applied to estimate the desired features from the
measured data. This method explicitly acknowledges that
uncertainty in the sensor positions exists and incorporates
this knowledge to find the maximum-likelihood feature
estimates by integrating over the uncertain measurement
positions. Due to the high dimensionality of the
integration, Monte Carlo integration, a statistical
technique to estimate the value of an integral, is employed.
Simulation results show that this Bayesian approach in
mitigating sensor position uncertainty produces features
with lower variability and, therefore, provides improved
discrimination performance.},
Key = {Tantum08}
}
%% Dahl, Jeremy J
@article{8629454,
Author = {Dahl, J.J. and Soo, M.S. and Trahey, G.E.},
Title = {Spatial and temporal aberrator stability for real-time
adaptive imaging},
Journal = {IEEE Trans. Ultrason. Ferroelectr. Freq. Control
(USA)},
Volume = {52},
Number = {9},
Pages = {1504 - 17},
url = {http://dx.doi.org/10.1109/TUFFC.2005.1516023},
Keywords = {biological tissues;biomedical ultrasonics;gynaecology;liver;phantoms;},
Abstract = {Reported real-time adaptive imaging systems use near-field
phase correction techniques, which are desired because of
their simple implementation and their compatibility with
current system architectures. Aberrator stability is
important to adaptive imaging because it defines the spatial
and temporal limits for which the near-field phase estimates
are valid. Spatial aberrator stability determines the
required spatial sampling of the aberrator, and temporal
aberrator stability determines the length of time for which
the aberration profile can be used. In this study, the
spatial and temporal stability of clinically measured
aberrations is reported for breast, liver, and thyroid
tissue. Cross correlations between aberration estimates
revealed aberrators to have azimuthal isoplanatic patch
sizes of 0.44, 0.28, and 0.20 mm for breast, liver, and
thyroid tissue, respectively, at 80% correlation. Axial
isoplanatic patch sizes were 1.26, 0.76, and 1.80 mm for the
same tissue, respectively, at 80% correlation. Temporal
stability at 80% correlation was determined to be greater
than 1.5 seconds for breast and thyroid tissue, and 0.65
seconds for the liver. The effects of noise, motion, and
target nonuniformity on aberrator stability are
characterized by simulations and experiments in tissue
mimicking phantoms},
Key = {8629454}
}
%% Dewhirst, Mark W
@article{3072705,
Author = {Engler, M.J. and Dewhirst, M.W. and Winget, J.M. and Oleson,
J.R.},
Title = {Automated temperature scanning for hyperthermia treatment
monitoring},
Journal = {Int. J. Radiat. Oncol. Biol. Phys. (UK)},
Volume = {13},
Number = {9},
Pages = {1377 - 82},
Keywords = {biomedical equipment;biothermics;computerised
monitoring;patient monitoring;patient treatment;},
Abstract = {Ideal descriptors of hyperthermia treatments will most
likely depend on complete target temperature distributions.
Although these distributions can be modeled numerically, the
accuracy of models is limited by the sparseness of
temperatures measured in vivo. Thus, the strategy of
monitoring temperatures may play a key role in improving
hyperthermia therapy. Scanning temperatures by manual
translations of thermometers was found to be excessively
time consuming. Consequently an automated system was
developed consisting of linear actuators, outriggers, guide
tubes, thermometry catheters, personal computer, and
dedicated hardware and software. During treatments, scan
patterns were created with algorithms using temperatures
measured preceding each thermometer translation. Measurement
position had a noteworthy influence on thermal dose
estimated by current models. Relative to manual scanning,
automated scanning increased measurement efficiency, reduced
probe position uncertainty, reduced operator time, and
provided improved data for modeling bioheat transfer and
thermal dose},
Key = {3072705}
}
@article{3735541,
Author = {Samulski, T.V. and Grant, W.J. and Oleson, J.R. and Leopold,
K.A. and Dewhirst, M.W. and Vallario, P. and Blivin,
J.},
Title = {Clinical experience with a multi-element ultrasonic
hyperthermia system: analysis of treatment
temperatures},
Journal = {Int. J. Hyperth. (UK)},
Volume = {6},
Number = {5},
Pages = {909 - 22},
Keywords = {biomedical ultrasonics;biothermics;radiation
therapy;},
Abstract = {A summary of tumour temperature data obtained from 31
patients who underwent 147 hyperthermia treatments with the
Sonotherm 1000 ultrasonic system is presented. The treatment
goal was to achieve a minimum of 42.0°C in tumour for 60
min duration with normal tissues remaining below 43.0°C.
In 83% of treatments at least one measured tumour
temperature reached or exceeded 42.0°C at some time
during the treatment. Nineteen per cent of these treatments
had a time- and spatial-averaged temperature (measured in
tumour)⩾42.0°C. A variety of anatomical sites were
treated and these were grouped into four categories:
groin/trunk, axilla, breast/chest wall and head/neck.
Measured temperatures in tumours located in the groin and
trunk sites were significantly higher (22%⩾42°C)
than other locations. The head and neck treatment
temperatures were significantly lower (8% of measured points
⩾42°C)},
Key = {3735541}
}
@article{6712701,
Author = {Thrall, D.E. and Rosner, G.L. and Azuma, C. and Larue, S.M. and Case, B.C. and Samulski, T. and Dewhirst,
M.W.},
Title = {Using units of CEM 43°C T90, local
hyperthermia thermal dose can be delivered as
prescribed},
Journal = {Int. J. Hyperth. (UK)},
Volume = {16},
Number = {5},
Pages = {415 - 28},
url = {http://dx.doi.org/10.1080/026567300416712},
Keywords = {hyperthermia;tumours;units (measurement);},
Abstract = {A randomized study was designed in dogs with spontaneous
soft tissue sarcomas to gain information about the
relationship between hyperthermia dose and outcome. The
study compared two levels of thermal dose applied to dogs
with heatable tumours, so it was necessary to deliver either
a low (2-5 CEM 43°C T<sub>90</sub>) or high (20-50 CEM
43°C T<sub>90</sub>) thermal dose as precisely as
possible. It was also desirable to have similar numbers of
hyperthermia treatments in each thermal dose group.
Identification of heatable tumours and randomization to:
high or low heat dose group was done during the first
hyperthermia treatment. This was readily accomplished using
mapping of temperatures in thermometry catheters, manual
recording of thermal data, and visual inspection of raw
thermal data with subsequent adjustment of the duration of
the hyperthermia treatment. An analysis of precision of
thermal dose delivery was conducted after approximately 50%
of projected accrual had been met in a randomized phase III
assessment of thermal dose effect. Fifty-four dogs were
eligible for randomization; in 48 dogs the tumour was deemed
heatable according to predetermined temperature criteria
applied during the first heat treatment. Twenty-four dogs
were randomized to the high heat dose group, and 24 to the
low heat dose group. Median (range) total thermal dose for
dogs in the high dose group was 43.5 CEM 43°C
T<sub>90</sub> (16.4-66.6) compared to 3.2 CEM 43°C
T<sub>90</sub> (2.1-4.6) for dogs in the low dose group.
There was no overlap of thermal doses between groups. Thus,
thermal dose could be delivered accurately, being within the
predetermined range in 47 of the 48 dogs. Thermal dose
quantified as CEM 43°C T50, however, did overlap between
groups and the clinical significance of this finding will
not be known until outcome data are analysed. Most dogs in
both groups received five hyperthermia treatments. Median
(range) treatment duration for dogs in the high dose group
was 300 min (147-692) compared to 111 min (51-381) for dogs
in the low dose group. Relatively simple but accurate
methods of delivering prescribed thermal dose as described
herein will aid the translation of clinical hyperthermia
from the research setting into more general practice once
the characteristics of the relationship between hyperthermia
dose and outcome are understood},
Key = {6712701}
}
@article{7918178,
Author = {Vujaskovic, Z. and Rosen, E.L. and Blackwell, K.L. and Jones, E.L. and Brizel, D.M. and Prosnitz, L.R. and Samulski, T.V. and Dewhirst, M.W.},
Title = {Ultrasound guided pO2 measurement of breast
cancer reoxygenation after neoadjuvant chemotherapy and
hyperthermia treatment},
Journal = {Int. J. Hyperth. (UK)},
Volume = {19},
Number = {5},
Pages = {498 - 506},
url = {http://dx.doi.org/10.1080/0265673031000121517},
Keywords = {biomedical electrodes;biomedical measurement;biomedical
optical imaging;biomedical ultrasonics;blood
vessels;cancer;hyperthermia;mammography;oxygen;polarography;surgery;tumours;},
Abstract = {The objective of this study was to determine whether
neoadjuvant chemotherapy in combination with hyperthermia
(HT) would improve oxygenation in locally advanced breast
tumours. The study describes a new optimized ultrasound
guided technique of pO<sub>2</sub> measurement using
Eppendorf polarographic oxygen probes in 18 stage IIB-III
breast cancer patients. Prior to treatment, tumour hypoxia
(median pO<sub>2</sub><10mmHg) was present in 11/18
patients (average median pO<sub>2</sub>=3.2 mmHg). Seven
patients had well oxygenated tumours (median pO<sub>2</sub>
of 48.3 mmHg). Eight patients with hypoxic tumours prior to
treatment had a significant improvement (p=0.0008) in tumour
pO<sub>2</sub>after treatment (pO<sub>2</sub> increased to
19.2 mmHg). In three patients, tumours remained hypoxic
(average median pO<sub>2</sub>=4.5mmHg). The advantages of
the ultrasound guided pO<sub>2</sub> probe are in the
accuracy of the Eppendorf electrode placement in tumour
tissue, the ability to monitor electrode movement through
the tumour tissue during the measurement and the ability to
avoid electrode placement near or in large blood vessels by
using colour Doppler imaging. The results of this
preliminary study suggest that the combination of
neoadjuvant chemotherapy and hyperthermia improves
oxygenation in locally advanced breast tumours that are
initially hypoxic},
Key = {7918178}
}
@article{6406702,
Author = {Kong, G. and Dewhirst, M.W.},
Title = {Hyperthermia and liposomes},
Journal = {Int. J. Hyperth. (UK)},
Volume = {15},
Number = {5},
Pages = {345 - 70},
url = {http://dx.doi.org/10.1080/026567399285558},
Keywords = {biomembranes;cancer;hyperthermia;reviews;tumours;},
Abstract = {Hyperthermia and liposomal drug delivery are treatment
modalities that have been used to treat cancer over the last
two decades. More recently, the two therapies have been used
together in an attempt to exploit their mutual interactions
against cancer. The goal of this review is to explore the
literature related to combined hyperthermia and liposomal
drug delivery for cancer therapy. The motivation behind
combining hyperthermia and liposomal drug delivery is
discussed from a physical chemical and physiological
standpoint. Two types of therapeutic ratios were calculated
for in vivo studies from across the literature. These ratios
compared the results obtained from hyperthermia and
liposomes to hyperthermia and free drug as well as to
liposomes without hyperthermia. These two therapeutic ratios
were applied to both tumour drug uptake and tumour growth
delay studies. In all studies reviewed, hyperthermia in
combination with liposomal drug showed an enhanced
therapeutic effect compared to either treatment modality
alone or hyperthermia and free drug. Future work needs to be
focused on optimizing thermosensitive liposomes and
understanding the effect of thermal dose on liposomal drug
delivery. Though not currently used in the clinic, this
combination therapy seems to hold great promise towards
improving current cancer therapeutic regimens},
Key = {6406702}
}
@article{6406703,
Author = {Thrall, D.E. and Larue, S.M. and Powers, B.E. and Page, R.L. and Johnson, J. and George, S.L. and Kornegay, J.N. and McEntee, M.C. and Levesque, D.C. and Smith, M. and Case,
B.C. and Dewhirst, M.W. and Gillette, E.L.},
Title = {Use of whole body hyperthermia as a method to heat
inaccessible tumours uniformly: a phase III trial in canine
brain masses},
Journal = {Int. J. Hyperth. (UK)},
Volume = {15},
Number = {5},
Pages = {383 - 98},
url = {http://dx.doi.org/10.1080/026567399285576},
Keywords = {brain;hyperthermia;tumours;},
Abstract = {In this study, whole body hyperthermia (WBH) was assessed as
a means of heating intracranial tumours uniformly.
Twenty-five dogs received radiation therapy and 20 the
combination of radiation and WBH. Total radiation dose was
randomly assigned and was either 44, 48, 52, 56 or 60 Gy.
Because of WBH toxicity, intercurrent disease or tumour
progression, 7 of the 45 dogs received less than the
prescribed radiation dose. For WBH, the target rectal
temperature was 42°C for 2 h and 3 treatments were
planned. In 5 of the 20 dogs randomized to receive WBH, only
one WBH treatment was given because of toxicity. WBH
toxicity was severe in 6 dogs, and resulted in death or
interruption in treatment. Most tumours did not undergo a
complete response, making it impossible to differentiate
tumour recurrence from brain necrosis as a cause of
progressive neuropathy. Therefore, survival was the major
study endpoint. There was no survival difference between
groups. One-year survival probability (95% CI) for dogs
receiving radiation therapy alone was 0.44 (0.25, 0.63)
versus 0.40 (0.19, 0.63) for dogs receiving radiation and
WBH. There was no difference in the incidence of brain
necrosis in the 2 treatment groups. Results suggest that use
of WBH alone to increase the temperature of intracranial
tumours as a means to improve radiation therapy outcome is
not a successful strategy},
Key = {6406703}
}
@article{4496016,
Author = {Prescott, D.M. and Charles, H.C. and Sostman, H.D. and Page,
R.L. and Thrall, D.E. and Moore, D. and Oleson, J.R. and Dewhirst, M.W.},
Title = {Manipulation of intra- and extracellular pH in spontaneous
canine tumours by use of hyperglycaemia [hyperthermia
efficacy improvement]},
Journal = {Int. J. Hyperth. (UK)},
Volume = {9},
Number = {5},
Pages = {745 - 54},
Keywords = {biothermics;cellular biophysics;pH;},
Abstract = {The authors evaluated the use of hyperglycaemia to reduce
tumour pH in dogs with spontaneous tumours. Dogs were
randomized to two groups: control and glucose. Intravenous
administration of 20% glucose was used to induce and
maintain hyperglycaemia. Extra and intracellular tumour pH
were measured using interstitial pH microelectrodes and
<sup>31</sup>P-MRS, respectively. During the administration
of glucose, the mean (± SEM) blood glucose
concentration was 419.8 (±32.8) and 121.1
(±8.0) mg/dI for the glucose and control groups,
respectively. The mean extracellular tumour pH before and
following 90 min of hyperglycaemia was 7.15 (±0.08)
and 7.15 (±0.09). During consecutive measurements,
intracellular tumour pH did not change significantly for the
control group or the group subjected to hyperglycaemic
manipulation. In contradistinction to previous rodent
studies, the authors' results demonstrate that
hyperglycaemia alone is not sufficient to manipulate either
intra- (pH<sub>i</sub>) or extracellular (pH<sub>e</sub>)
hydrogen ion concentration in spontaneous canine soft tissue
tumours},
Key = {4496016}
}
%% Dobbins III, James T
@article{2398373,
Author = {Dobbins, J.T., III and Pedersen, P.L. and Mazess, R.B. and Cameron, J.R. and Hansen, J.L. and Hefner,
L.V.},
Title = {A scanning-slit X-ray videoabsorptiometric technique for
bone mineral measurement},
Journal = {Med. Phys. (USA)},
Volume = {11},
Number = {5},
Pages = {582 - 8},
url = {http://dx.doi.org/10.1118/1.595554},
Keywords = {biomedical measurement;bone;diagnostic radiography;},
Abstract = {An X-ray videoabsorptiometric technique was developed for
measurement of bone mineral content (BMC) in vivo. The
principle utility of this technique is the precise
measurement of commonly fractured bones, such as the femoral
neck, that are difficult to measure by other techniques
because of repositioning problems. Scanning slits reduce
scattered radiation and improve linearity of measurements.
Heavily filtered, high-kVp beams are used to minimize errors
from beam hardening, and data renormalization is employed to
compensate for spatial nonuniformities of the beam and
detector. Linearity of measured BMC over the range 0.8 to 5
g/cm<sup>2</sup> is very good (<i>r</i>=0.998) and compares
well to single- and dual-photon absorptiometry. A 1.6%
change in measured BMC is observed for a 10% change (~2 cm)
in tissue thickness while a 10% change in marrow type causes
a 0.6%-0.8% change in BMC. Manual repositioning of a femur
phantom revealed a variation of 0.84% over ten measurements
when femur values were referenced to standards. A computer
repositioning algorithm provides much easier identification
of the region for analysis and yields comparable variation
(0.9%)},
Key = {2398373}
}
@article{8104164,
Author = {Samei, E. and Saunders, R.S. and Lo, J.Y. and Dobbins, J.T. and Jesneck, J.L. and Floyd, C.E. and Ravin,
C.E.},
Title = {Fundamental imaging characteristics of a slot-scan digital
chest radiographic system},
Journal = {Med. Phys. (USA)},
Volume = {31},
Number = {9},
Pages = {2687 - 98},
url = {http://dx.doi.org/10.1118/1.1783531},
Keywords = {aluminium;diagnostic radiography;flat panel displays;image
resolution;lung;medical image processing;phantoms;},
Abstract = {Our purpose in this study was to evaluate the fundamental
image quality characteristics of a new slot-scan digital
chest radiography system (ThoraScan, Delft Imaging
Systems/Nucletron, Veenendaal, The Netherlands). The
linearity of the system was measured over a wide exposure
range at 90, 117, and 140 kVp with added Al filtration.
System uniformity and reproducibility were established with
an analysis of images from repeated exposures. The
modulation transfer function (MTF) was evaluated using an
established edge method. The noise power spectrum (NPS) and
the detective quantum efficiency (DQE) of the system were
evaluated at the three kilo-voltages over a range of
exposures. Scatter fraction (SF) measurements were made
using a posterior beam stop method and a geometrical chest
phantom. The system demonstrated excellent linearity, but
some structured nonuniformities. The 0.1 MTF values occurred
between 3.3-3.5 mm<sup>-1</sup>. The DQE(0.15) and DQE(2.5)
were 0.21 and 0.07 at 90 kVp, 0.18 and 0.05 at 117 kVp, and
0.16 and 0.03 at 140 kVp, respectively. The system exhibited
remarkably lower SFs compared to conventional full-field
systems with anti-scatter grid, measuring 0.13 in the lungs
and 0.43 in the mediastinum. The findings indicated that the
slot-scan design provides marked scatter reduction leading
to high effective DQE (DQE<sub>eff</sub>) of the system and
reduced patient dose required to achieve high image
quality},
Key = {8104164}
}
%% Erickson, Harold P
@article{fds156445,
Author = {D Popp and M Iwasa and A Narita and HP Erickson and Y
Maéda},
Title = {FtsZ condensates: An in vitro electron microscopy
study.},
Journal = {Biopolymers},
Year = {2009},
Month = {January},
ISSN = {0006-3525},
Abstract = {In vivo cell division protein FtsZ from E.coli forms rings
and spirals which have only been observed by low resolution
light microscopy. We show that these suprastructures are
likely formed by molecular crowding which is a predominant
factor in prokaryotic cells and enhances the weak lateral
bonds between protofilaments.While FtsZ assembles into
single protofilaments in dilute aqueous buffer, with
crowding agents above a critical concentration, it forms
polymorphic supramolecular structures including rings and
toroids (with multiple protofilaments) about 200 nm in
diameter, similar in appearance to DNA toroids and helices
with pitches of several hundred nm as well as long, linear
bundles. Helices resemble those observed in vivo, whereas
the rings and toroids may represent a novel energy minimized
state of FtsZ, at a later stage of Z-ring constriction.We
shed light on the molecular arrangement of FtsZ filaments
within these suprastructures using high resolution electron
microscopy. (c) 2009 Wiley Periodicals, Inc. Biopolymers,
2009.},
Key = {fds156445}
}
@article{fds156446,
Author = {J Xu and E Bae and Q Zhang and DS Annis and HP Erickson and DF
Mosher},
Title = {Display of cell surface sites for fibronectin assembly is
modulated by cell adherence to (1)F3 and C-terminal modules
of fibronectin.},
Journal = {PLoS ONE, United States},
Volume = {4},
Number = {1},
Pages = {e4113},
Year = {2009},
ISSN = {1932-6203},
Keywords = {Animals Cell Adhesion Cells, Cultured Fibronectins Focal
Adhesions Humans Mice Mice, Knockout Peptide Fragments
Recombinant Proteins Vinculin chemistry chemistry* genetics
metabolism metabolism* physiology*},
Abstract = {BACKGROUND: Fibronectin-null cells assemble soluble
fibronectin shortly after adherence to a substrate coated
with intact fibronectin but not when adherent to the
cell-binding domain of fibronectin (modules (7)F3-(10)F3).
Interactions of adherent cells with regions of adsorbed
fibronectin other than modules (7)F3-(10)F3, therefore, are
required for early display of the cell surface sites that
initiate and direct fibronectin assembly.
METHODOLOGY/PRINCIPAL FINDINGS: To identify these regions,
coatings of proteolytically derived or recombinant pieces of
fibronectin containing modules in addition to (7)F3-(10)F3
were tested for effects on fibronectin assembly by adherent
fibronectin-null fibroblasts. Pieces as large as one
comprising modules (2)F3-(14)F3, which include the
heparin-binding and cell adhesion domains, were not
effective in supporting fibronectin assembly. Addition of
module (1)F3 or the C-terminal modules to modules
(2)F3-(14)F3 resulted in some activity, and addition of both
(1)F3 and the C-terminal modules resulted in a construct,
(1)F3-C, that best mimicked the activity of a coating of
intact fibronectin. Constructs (1)F3-C V0, (1)F3-C V64, and
(1)F3-C Delta(V(15)F3(10)F1) were all able to support
fibronectin assembly, suggesting that (1)F3 through (11)F1
and/or (12)F1 were important for activity. Coatings in which
the active parts of (1)F3-C were present in different
proteins were much less active than intact (1)F3-C.
CONCLUSIONS: These results suggest that (1)F3 acts together
with C-terminal modules to induce display of fibronectin
assembly sites on adherent cells.},
Key = {fds156446}
}
@article{fds156450,
Author = {M Osawa and DE Anderson and HP Erickson},
Title = {Reconstitution of contractile FtsZ rings in
liposomes.},
Journal = {Science (New York, N.Y.), United States},
Volume = {320},
Number = {5877},
Pages = {792-4},
Year = {2008},
Month = {May},
ISSN = {1095-9203},
Keywords = {Bacterial Proteins Cell Membrane Cytoskeletal Proteins
Escherichia coli Escherichia coli Proteins Liposomes
Membrane Proteins Protein Binding Protein Transport
Recombinant Proteins genetics physiology*},
Abstract = {FtsZ is a tubulin homolog and the major cytoskeletal protein
in bacterial cell division. It assembles into the Z ring,
which contains FtsZ and a dozen other division proteins, and
constricts to divide the cell. We have constructed a
membrane-targeted FtsZ (FtsZ-mts) by splicing an amphipathic
helix to its C terminus. When mixed with lipid vesicles,
FtsZ-mts was incorporated into the interior of some tubular
vesicles. There it formed multiple Z rings that could move
laterally in both directions along the length of the
liposome and coalesce into brighter Z rings. Brighter Z
rings produced visible constrictions in the liposome,
suggesting that FtsZ itself can assemble the Z ring and
generate a force. No other proteins were needed for assembly
and force generation.},
Key = {fds156450}
}
@article{fds156449,
Author = {Y Chen and HP Erickson},
Title = {In vitro assembly studies of FtsZ/tubulin-like proteins
(TubZ) from Bacillus plasmids: evidence for a capping
mechanism.},
Journal = {The Journal of biological chemistry, United
States},
Volume = {283},
Number = {13},
Pages = {8102-9},
Year = {2008},
Month = {March},
ISSN = {0021-9258},
Keywords = {Bacillus anthracis Bacillus thuringiensis Bacterial Proteins
Cytoskeletal Proteins Escherichia coli Proteins GTP
Phosphohydrolases Guanosine Triphosphate Microscopy,
Electron Plasmids Tubulin genetics genetics* metabolism
metabolism* ultrastructure},
Abstract = {Proteins with a weak sequence similarity to tubulin and FtsZ
are expressed from large plasmids of Bacillus anthracis and
Bacillus thuringiensis and are probably involved in plasmid
segregation. Previously designated RepX and TubZ, we
designate them here as TubZ-Ba and TubZ-Bt. We have
expressed and purified the proteins for in vitro studies.
TubZ-Ba and TubZ-Bt share only 21% amino acid identity, but
they have remarkably similar biochemical properties. They
both assemble into two-stranded filaments and larger bundles
above a critical concentration, and they hydrolyze GTP at a
very high rate, approximately 20 GTP min(-1) TubZ(-1).
Assembly is also supported by GTPgammaS. A tiny amount of
GTPgammaS stabilizes polymers assembled in GTP and inhibits
the GTPase by a mechanism involving cooperativity. The
nucleotide in the polymers is almost 100% GDP, which is
similar to microtubules but very different from the 20-30%
GDP in FtsZ polymers. This suggests that the TubZ polymers
have a capping mechanism that may be related to the GTP cap
that produces dynamic instability of microtubules.},
Key = {fds156449}
}
%% Friedman, Morton H
@booklet{Ateshian09,
Author = {G. A. Ateshian and M. H. Friedman},
Title = {Integrative biomechanics: A paradigm for clinical
applications of fundamental mechanics},
Journal = {Journal Of Biomechanics},
Volume = {42},
Number = {10},
Pages = {1444 -- 1451},
Year = {2009},
Month = {July},
ISSN = {0021-9290},
Abstract = {Integrative biomechanics uses biomechanics knowledge and
methods at multiple scales and among biological entities to
address fundamental and clinical problems at the tissue and
organ level. Owing to the large ranges of scale involved,
integrative biomechanics is intrinsically multidisciplinary,
extending from molecular biophysics to contemporary
engineering descriptions of kinematics and bulk constitutive
properties. Much of this integration is accomplished through
multiscale models of the interactions of interest.
Applications can range from the development of new
biological knowledge to the creation of new technologies for
clinical application. In this white paper, the historical
background of, and the rationale behind, integrative
biomechanics are reviewed, followed by a sampling of
clinical advances that were developed using the integrative
approach. Refinements of many of these advances are still
needed, and unsolved problems remain, in genomic
applications, developing improved interventional procedures
and protocols, and personalized medicine. Challenges to
achieve these goals include the need for better models and
the acquisition and organization of the data needed to
parameterize, validate and apply them. These challenges will
be overcome, because the advances in characterizing disease
risk, personalization of care, and therapeutics that will
follow, demand that we continue to move forward in this
exciting field. (C) 2009 Elsevier Ltd. All rights
reserved.},
Key = {Ateshian09}
}
@booklet{Zhu09,
Author = {H. Zhu and Z. H. Ding and R. N. Piana and T. R. Gehrig and M. H. Friedman},
Title = {Cataloguing the geometry of the human coronary arteries: A
potential tool for predicting risk of coronary artery
disease},
Journal = {International Journal Of Cardiology},
Volume = {135},
Number = {1},
Pages = {43 -- 52},
Year = {2009},
Month = {June},
ISSN = {0167-5273},
Abstract = {Background: The non-uniform distribution of atherosclerosis
in the human vasculature suggests that local fluid dynamics
or wall mechanics may be involved in atherogenesis. Thus
certain aspects of vascular geometry, which mediates both
fluid dynamics and wall mechanics, might be risk factors for
coronary atherosclerosis. Cataloguing the geometry of normal
human coronary arteries and its variability is a first step
toward identifying specific geometric features that increase
vascular susceptibility to the disease. Methods: Images of
angiographically normal coronary arteries, including 32 left
anterior descending ( LAD) and 35 right coronary arteries
(RCA), were acquired by clinical biplane cineangiography
from 52 patients. The vessel axes in end diastole were
reconstructed and geometric parameters that included
measures of curvature, torsion and tortuosity were
quantified for the proximal, middle and distal segments of
the arteries. Results: Statistical analysis shows that ( 1)
in the LAD, curvature, torsion and tortuosity are generally
highest in the distal portion, ( 2) in the RCA, these
parameters are smallest in the middle segment, ( 3) the LAD
exhibits significant higher torsion than the RCA
(P$<$0.005), and (4) $>$80\% of the variability of coronary
arterial geometry can be expressed in terms of two factors,
one dominated by the curvature measures and tortuosity, and
the other emphasizing the torsion parameters. Conclusions:
This study has comprehensively documented the normal
arterial geometry of the LAD and RCA in end diastole. This
information may be used to guide the identification of
geometric features that might be atherogenic risk factors.
(C) 2008 Elsevier Ireland Ltd. All rights
reserved.},
Key = {Zhu09}
}
@booklet{Friedman09,
Author = {M. H. Friedman},
Title = {Variability of arterial wall shear stress, its dependence on
vessel diameter and implications for Murray's
Law},
Journal = {Atherosclerosis},
Volume = {204},
Number = {1},
Pages = {18 -- 19},
Year = {2009},
Month = {May},
ISSN = {0021-9150},
Key = {Friedman09}
}
@booklet{Friedman09a,
Author = {M. H. Friedman},
Title = {Variability of arterial wall shear stress, its dependence on
vessel diameter and implications for Murray's
Law},
Journal = {Atherosclerosis},
Volume = {203},
Number = {1},
Pages = {47 -- 48},
Year = {2009},
Month = {March},
ISSN = {0021-9150},
Key = {Friedman09a}
}
@booklet{Liang08a,
Author = {Y. Liang and H. Zhu and M. H. Friedman},
Title = {Estimation of the transverse strain tensor in the arterial
wall using ivus image registration},
Journal = {Ultrasound In Medicine And Biology},
Volume = {34},
Number = {11},
Pages = {1832 -- 1845},
Year = {2008},
Month = {November},
ISSN = {0301-5629},
Abstract = {Intravascular ultrasound (IVUS) elastography is an imaging
technique that obtains the local mechanical properties of
the artery wall and atherosclerotic plaques through strain
measurements using IVUS. Knowledge of these mechanical
properties may provide crucial information that can help in
estimating plaque composition and its vulnerability. Here,
we present a new method to estimate the transverse strain
tensor of the arterial wall based on nonrigid image
registration using IVUS images. This method registers a pair
of images acquired at a vessel site under different levels
of luminal pressure. The 2-D displacement field in the
vessel cross-section is estimated from image registration;
then the displacement field is used to calculate the 2-D
local strain tensor. From the strain tensor, the strain in
any direction in the cross-section can be obtained; here,
the radial and circumferential strain distributions are
presented. This strain estimation method has been validated
with synthetic motion IVUS images and evaluated using the
IVUS images of a polyvinyl alcohol cryogel phantom. The
accuracy of the estimated strain and the ability of the
method to overcome IVUS system noise are demonstrated.
(E-mail: mhfriedm@duke.edu) (C) 2008 World Federation for
Ultrasound in Medicine \& Biology.},
Key = {Liang08a}
}
@booklet{Liang08,
Author = {Y. Liang and H. Zhu and T. Gehrig and M. H.
Friedman},
Title = {Measurement of the transverse strain tensor in the coronary
arterial wall from clinical intravascular ultrasound
images},
Journal = {Journal Of Biomechanics},
Volume = {41},
Number = {14},
Pages = {2906 -- 2911},
Year = {2008},
Month = {October},
ISSN = {0021-9290},
Abstract = {Atherosclerotic plaque rupture is the major cause of acute
coronary syndromes. Currently, there is no reliable
diagnostic tool to predict plaque rupture. Knowledge of
plaque mechanical properties based on local artery wall
strain measurements would be useful for characterizing its
composition and predicting its vulnerability. Due to cardiac
motion, strain estimation in clinical intravascular
ultrasound (IVUS) images is extremely challenging. A method
is presented to estimate cross-sectional coronary artery
wall strain in response to cardiac pulsatile pressure using
clinically acquired IVUS images, which are acquired in
continuous pullback mode. First, cardiac phase information
is retrieved retrospectively from an IVUS image sequence
using an image-based gating method, and image sub-sequences
at systole and diastole are extracted. Then, images at
branch sites are used as landmarks to align the two image
subsequences. Finally, the paired images at each site are
registered to measure the 2D strain tensor of the coronary
artery cross-section. This method has been successfully
applied to IVUS images of a left anterior descending (LAD)
coronary artery acquired clinically during a standard
procedure. Such complete strain information should be useful
for identifying vulnerable plaque. (c) 2008 Elsevier Ltd.
All rights reserved.},
Key = {Liang08}
}
@booklet{Zhang08,
Author = {J. Zhang and K. A. Burridge and M. H. Friedman},
Title = {In vivo differences between endothelial transcriptional
profiles of coronary and iliac arteries revealed by
microarray analysis},
Journal = {American Journal Of Physiology-heart And Circulatory
Physiology},
Volume = {295},
Number = {4},
Pages = {H1556 -- H1561},
Year = {2008},
Month = {October},
ISSN = {0363-6135},
Abstract = {Endothelial cells (ECs) from different vascular beds display
a remarkable heterogeneity in both structure and function.
Phenotypic heterogeneity among arterial ECs is particularly
relevant to atherosclerosis since the disease occurs
predominantly in major arteries, which vary in their
atherosusceptibility. To explore EC heterogeneity between
typical atheroprone and atheroresistant arteries, we used
DNA microarrays to compare gene expression profiles of
freshly harvested porcine coronary (CECs) and iliac artery
(IECs) ECs. Statistical analysis revealed 51 genes that were
differentially expressed in CECs relative to IECs at a false
discovery rate of 5\%. Seventeen of these genes are known to
be involved in atherogenesis. Consistent with coronary
arteries being more atherosusceptible, almost all putative
atherogenic genes were overexpressed in CECs, whereas all
atheroprotective genes were downregulated, relative to IECs.
A subset of the identified genes was validated by
quantitative polymerase chain reaction (PCR). PCR results
suggest that the differences in expression levels between
CECs and IECs for the HOXA10 and HOXA9 genes were $>$
100-fold. Gene ontology (GO) and biological pathway analysis
revealed a global expression difference between CECs and
IECs. Genes in twelve GO categories, including complement
immune activation, immunoglobulin-mediated response, and
system development, were significantly upregulated in CECs.
CECs also overexpressed genes involved in several
inflammatory pathways, including the classical pathway of
complement activation and the IGF-1-mediated pathway. The in
vivo transcriptional differences between CECs and IECs found
in this study may provide new insights into the factors
responsible for coronary artery atherosusceptibility.},
Key = {Zhang08}
}
@article{2149516,
Author = {Friedman, M.H. and Srivastava, Y.N.},
Title = {Gauge theories with composite bosons},
Journal = {Phys. Rev. D, Part. Fields (USA)},
Volume = {28},
Number = {6},
Pages = {1491 - 5},
Year = {15},
url = {http://dx.doi.org/10.1103/PhysRevD.28.1491},
Keywords = {boson systems;fermion systems;gauge field
theory;renormalisation;},
Abstract = {The authors develop an approach for introducing bosons into
gauge theories as composite states of fermions. It is scale
and gauge invariant from the outset and utilizes invariant
regularization procedures. This results in the acquisition
of gauge-covariant kinetic energy by the bosons and the
growth of coupling constants and masses. Relationships among
the coupling constants and masses are derived},
Key = {2149516}
}
@article{457428,
Author = {Nath, P. and Arnowitt, R. and Friedman, M.H.},
Title = {Broken scale invariance, current algebra, and massive
`gravitation. I. General formulation},
Journal = {Phys. Rev. D, Part. Fields (USA)},
Volume = {6},
Number = {6},
Pages = {1572 - 87},
Year = {15},
url = {http://dx.doi.org/10.1103/PhysRevD.6.1572},
Keywords = {current algebra;meson interactions;},
Abstract = {A general analysis is given of the interaction of mesons of
<i>J</i><sup>P</sup>=0<sup>±</sup>,
1<sup>±</sup>, and 2<sup>+</sup> obeying the
principles of broken scale invariance in the tree and
seagull approximations. Broken scale invariance is
introduced through a new postulate which requires that the
improved Belinfante stress tensor and its trace play a
fundamental role as sources of the <i>J</i><sup>P</sup>=2<sup>+</sup>,
0<sup>+</sup> mesons with a universal coupling strength. The
universality also leads to new relations of the type
<i>g</i><sub>f</sub>=<i>F</i><sub>σ</sub><i>m</i><sub>f</sub><sup>2</sup>,
etc., between the <i>f</i>- and σ-meson interpolating
constants which resemble the Kawarabayashi-Suzuki-Riazuddin-Fayyazuddin-type
relations in current algebra. The form of the vector current
in the presence of broken scale invariance is derived. The
condition of scale breaking implies that the vector current
has canonical scale dimension 3, and the apparent conflict
of conservation of vector current with the <i>f</i>
couplings is resolved. Experimental tests of the present
formalism are indicated},
Key = {457428}
}
@article{629512,
Author = {Friedman, M.H. and Tanner, J.T.},
Title = {A system for the automated acquisition and reduction of
neutron activation analysis data},
Journal = {Trans. Am. Nucl. Soc. (USA)},
Volume = {17},
Pages = {126 -},
Address = {San Francisco, CA, USA},
Keywords = {chemical analysis by nuclear reactions and scattering;data
acquisition;data reduction and analysis;},
Abstract = {A system is described, based on a multiple element language
MTELMT which can automatically search a spectrum, find the
resolved peaks, and output the energies and areas of the
peaks; make linear or semilogarithmic CAL COMP plots; and
provide an accurate energy calibration},
Key = {629512}
}
@article{5701956,
Author = {Friedman, M.H. and Srivastava, Y. and Widom,
A.},
Title = {Fermions in an external SU(2) magnetic field},
Journal = {J. Phys. G, Nucl. Part. Phys. (UK)},
Volume = {23},
Number = {9},
Pages = {1061 - 4},
url = {http://dx.doi.org/10.1088/0954-3899/23/9/005},
Keywords = {eigenvalues and eigenfunctions;fermions;gauge field
theory;SU(2) theory;},
Abstract = {We consider fermions in a constant and uniform external
SU(2) magnetic field. We find that the results for the
energy levels depend on the choice of gauge. Choosing a
Landau-type gauge yields results analagous to those of
Abelian theories. On the other hand, using another gauge
potential one obtains a different continuous eigenvalue
spectrum},
Key = {5701956}
}
@article{5488610,
Author = {Friedman, M.H. and Srivastava, Y. and Widom,
A.},
Title = {The physical states of QCD},
Journal = {Phys. Essays (Canada)},
Volume = {9},
Number = {3},
Pages = {429 - 33},
Keywords = {quantum chromodynamics;},
Abstract = {We use the constraint imposed by Gauss's law to argue that
the color charged states of SU(3) [quantum chromodynamics
(QCD)] are not physical. We further show that the matrix
elements of products of gluon field and quark current
operators at different space-time points vanish when taken
between physical states. This is true even if the operators
are combined to make up color singlet objects. These results
are in keeping with experimental observation},
Key = {5488610}
}
@article{581494,
Author = {Friedman, M.H.},
Title = {Unsteady transport and hydration dynamics in the in vivo
cornea},
Journal = {Biophys. J. (USA)},
Volume = {13},
Number = {9},
Pages = {890 - 910},
Keywords = {eye;},
Abstract = {The unsteady response of the rabbit cornea to the normal
periodic variations in tear tonicity which accompany the
sleep-wake cycle is examined quantitatively in terms of a
physical description of corneal mechanics and transport. Two
different sets of experimental epithelial and endothelial
flow conductivities and reflection coefficients are used,
and the effect of variations in epithelial solute
permeability and sodium pump rate is examined},
Key = {581494}
}
@article{1187032,
Author = {Mark, F.F. and Bargeron, C.B. and Deters, O.J. and Friedman,
M.H.},
Title = {Experimental investigations of steady and pulsatile laminar
flow in a 90° branch},
Journal = {Trans. ASME, E, J. Appl. Mech. (USA)},
Volume = {44},
Number = {3},
Pages = {372 - 7},
Keywords = {haemodynamics;laminar flow;pulsatile flow;shear
flow;},
Abstract = {Velocity measurements are reported for steady and unsteady
flow in a rectangular cross-section Y-branch of high aspect
ratio. Good agreement is found between the experimental
results and two-dimensional calculations. Emphasis is placed
on flow velocities near and parallel to the outer wall
inasmuch as their gradients are proportional to wall
shearing stress which may be of influence in atherogenesis.
Large variation in flow velocities and hence shearing stress
are found in the immediate vicinity of the corner. The
results in this region could support theories which propose
either high or low shearing stress as an important
consideration in the etiology of arteriosclerosis},
Key = {1187032}
}
%% Gauthier, Daniel J.
@article{fds50289,
Author = {D.J. Gauthier},
Title = {Superluminal communication in quantum mechanics},
Booktitle = {an invited article in Compendium of Quantum Physics:
Concepts, Experiments, History and Philosophy},
Publisher = {Springer},
Editor = {B. Falkenburg and D. Greenberger and K. Hentschel and F.
Weinert},
Year = {2009},
Key = {fds50289}
}
@article{fds151772,
Author = {R.W. Boyd and D.J. Gauthier and P. Narum},
Title = {Causality in superluminal pulse propagation},
Booktitle = {an invited chapter in Time in Quantum Mechanics
II},
Publisher = {Springer},
Address = {Berlin},
Editor = {J. G. Muga},
Year = {2009},
Key = {fds151772}
}
@article{fds154286,
Author = {Recent advancements in SBS Slow Light},
Title = {E. Cabrera-Granado and D.J. Gauthier},
Journal = {an invited article in Opt. Pura Apl.},
Volume = {41},
Pages = {313},
Year = {2008},
Month = {December},
url = {http://www.phy.duke.edu/research/photon/qelectron/pubs/OptPuraApl41_313_2008.pdf},
Key = {fds154286}
}
@article{fds154992,
Author = {J.A. Greenberg and D.J. Gauthier},
Title = {Transient dynamics and momentum redistribution in cold atoms
via recoil-induced resonances},
Journal = {Phys. Rev. A},
Year = {2008},
Month = {December},
Key = {fds154992}
}
@article{fds151769,
Author = {X. Zhao and D.G. Schaeffer and C.M. Berger and W. Krassowska and D.J. Gauthier},
Title = {`Cardiac alternans arising from an unfolded border-collision
bifurcation},
Journal = {J. Comput. Nonlinear Dynam.},
Volume = {3},
Pages = {041004},
Year = {2008},
Month = {October},
url = {http://www.phy.duke.edu/research/photon/qelectron/pubs/JComputNonlinearDynam3_041004_2008.pdf},
Key = {fds151769}
}
@article{fds151771,
Author = {A.A. Juarez and R. Vilaseca and Z. Zhu and D.J.
Gauthier},
Title = {Room-temperature spectral hole burning in an engineered
inhomogeneously-broadened resonance},
Journal = {Opt. Lett.},
Volume = {33},
Pages = {2374},
Year = {2008},
Month = {October},
url = {http://www.phy.duke.edu/research/photon/qelectron/pubs/OptLett33_2374_2008.pdf},
Key = {fds151771}
}
@article{fds151770,
Author = {E. Cabrera-Granado and O.G. Calderón and Sonia Melle and D.J.
Gauthier},
Title = {Observation of large 10-Gb/s SBS slow light delay with low
distortion using an optimized gain profile},
Journal = {Opt. Express},
Volume = {16},
Number = {16032},
Year = {2008},
Month = {September},
url = {http://www.phy.duke.edu/research/photon/qelectron/pubs/OptExpress16_16032_2008.pdf},
Key = {fds151770}
}
@article{fds151768,
Author = {D.W. Evertson and M.R. Holcomb and M.D.C. Eames and M.A.P. Bray and V.Y.
Sidorov, J. Xu and H. Wingard and H.M. Dobrovolny and M.C. Woods and D.J. Gauthier and J.P. Wikswo},
Title = {`High-resolution high-speed panoramic cardiac imaging
system},
Journal = {IEEE Trans. Biomed. Eng.},
Number = {55},
Pages = {1241},
Year = {2008},
Month = {March},
url = {http://www.phy.duke.edu/research/photon/qelectron/pubs/IEEETransBME55_1241_2008.pdf},
Key = {fds151768}
}
@article{fds151767,
Author = {R. Pant and M.D. Stenner and M.A. Neifeld and D.J.
Gauthier},
Title = {Optimal pump profile designs for broadband SBS slow-light
systems},
Journal = {Opt. Express},
Volume = {16},
Pages = {2764},
Year = {2008},
Month = {February},
url = {http://www.phy.duke.edu/research/photon/qelectron/pubs/OptExpress16_2764_2008.pdf},
Key = {fds151767}
}
@article{fds151766,
Author = {A.M.C. Dawes and L. Illing and J.A. Greenberg and D.J.
Gauthier},
Title = {All-Optical Switching with Transverse Optical
Patterns},
Journal = {Phys. Rev. A},
Volume = {77},
Pages = {013833},
Year = {2008},
Month = {January},
url = {http://www.phy.duke.edu/research/photon/qelectron/pubs/Switching_PRA_77_013833.pdf},
Key = {fds151766}
}
@article{fds151776,
Author = {A.M.C. Dawes and D.J. Gauthier},
Title = {`Using Transverse Patterns for All-Optical
Switching},
Booktitle = {Coherence and Quantum Optics IX},
Year = {2008},
Key = {fds151776}
}
@article{fds151777,
Author = {A.M.C. Dawes and D.J. Gauthier and S. Schumacher and N.H. Kwong and R.
Binder and A.L. Smirl},
Title = {Transverse optical patters for ultra-low-light-level
all-optical switching},
Journal = {an invited article in Laser & Photonics Rev.},
Year = {2008},
Key = {fds151777}
}
@article{fds151775,
Author = {Z. Zhu and D.J. Gauthier and A.L. Gaeta and R.W.
Boyd},
Title = {Slow light in optical waveguides},
Booktitle = {an invited chapter in Slow Light: Science and
Applications},
Publisher = {CRC Press},
Address = {Boca Raton},
Editor = {J. Khurgin},
Year = {2008},
Key = {fds151775}
}
@article{fds151778,
Author = {C.J. Broadbent and P.K. Vudyasetu and R.M. Camacho and D.J. Gauthier and J.C. Howell},
Title = {Pseudo-thermal slow light},
Journal = {Phys. Rev. Lett.},
Year = {2008},
Key = {fds151778}
}
@article{fds151774,
Author = {G.M. Gehring and R.W. Boyd and A.L. Gaeta and D.J. Gauthier and A.E.
Willner},
Title = {Fiber-Based Slow-Light Technologies},
Journal = {J. Lightwave Tech.},
Year = {2008},
Key = {fds151774}
}
@article{fds139716,
Author = {L. Illing and D. J. Gauthier and J. N. Blakely},
Title = {Controlling fast chaos in opto-electronic delay dynamical
systems},
Pages = {407-425},
Booktitle = {Handbook of Chaos Control, 2nd Ed.},
Publisher = {WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim,
Germany},
Editor = {E. Schöll and H. G. Schuster},
Year = {2008},
ISBN = {978-3-527-40605-0},
url = {http://www.phy.duke.edu/research/photon/qelectron/pubs/IllingChaosHandbookPreprint2006.pdf},
Key = {fds139716}
}
%% Gersbach, Charles A
@article{fds157868,
Author = {R.M. Gordley and C.A. Gersbach and C.F. Barbas,
III},
Title = {Synthesis of programmable integrases},
Journal = {Proceedings of the National Academy of Sciences
USA},
Volume = {106},
Number = {13},
Pages = {5053-8},
Year = {2009},
Key = {fds157868}
}
%% Glower, Donald D
@article{fds151753,
Author = {B Jungwirth and DB Adams and JP Mathew and M Swaminathan and DD Glower and GB Mackensen},
Title = {Mitral valve prolapse and systolic anterior motion
illustrated by real time three-dimensional transesophageal
echocardiography.},
Journal = {Anesthesia and analgesia, United States},
Volume = {107},
Number = {6},
Pages = {1822-4},
Year = {2008},
Month = {December},
ISSN = {1526-7598},
Key = {fds151753}
}
@article{fds151749,
Author = {CA Milano and MA Daneshmand and JS Rankin and E Honeycutt and ML
Williams, M Swaminathan and L Linblad and LK Shaw and DD Glower and PK
Smith},
Title = {Survival prognosis and surgical management of ischemic
mitral regurgitation.},
Journal = {The Annals of thoracic surgery, Netherlands},
Volume = {86},
Number = {3},
Pages = {735-44},
Year = {2008},
Month = {September},
ISSN = {1552-6259},
Keywords = {Age Factors Aged Comorbidity Coronary Artery Bypass Coronary
Disease Female Heart Valve Prosthesis Humans Male Middle
Aged Mitral Valve Insufficiency Prognosis Survival Rate
complications mortality* surgery*},
Abstract = {BACKGROUND: Ischemic mitral regurgitation (IMR) has an
adverse prognosis, but survival characteristics and
management are controversial. This study reviewed a 20-year
series of IMR patients managed with multiple approaches to
assess and refine surgical strategies. METHODS: Patients
having surgery for primary coronary disease from 1986 to
2006 were divided into group 1 (no IMR; bypass grafting
only; n = 16,209), group 2a (IMR; bypass only; n = 3,181),
group 2b (IMR; mitral repair; n = 416), and group 2c (IMR;
mitral replacement; n = 106). Cox proportional hazards
modeling adjusted for baseline differences, and therapeutic
adequacy was quantified by area under each survival curve
expressed as a percentage of group 1. RESULTS: Group 2
patients were older than group 1 patients and had worse
baseline characteristics. Group 2a had less severe MR and
group 2b had the most comorbidity. Assuming group 1 provided
the best adjusted outcome at a given baseline risk, group 2a
achieved 97.7%, 2b achieved 93.7%, and 2c achieved 79.1% of
potential survival (hazard ratio 1.1, 1.4, and 1.6,
respectively; p < 0.003). Most of the survival difference
was perioperative. CONCLUSIONS: Worse baseline risk is a
major factor reducing long-term survival in IMR. Current
algorithms in which mild to moderate IMR is managed with
bypass only (group 2a) generally produced good late results.
In patients with moderate and severe IMR, repair achieved
93.7% of full survival potential; valve replacement was less
satisfactory, primarily owing to higher operative mortality.
Future therapeutic refinement, emphasizing reparative
procedures and better perioperative care, could enhance the
surgical prognosis of IMR.},
Key = {fds151749}
}
@article{fds151750,
Author = {RH Mehta and JD Grab and SM O'Brien and DD Glower and CK Haan and JS
Gammie, ED Peterson and on Behalf of the Society of Thoracic
Surgeons National Cardiac Database Investigators},
Title = {Clinical Characteristics and In-Hospital Outcomes of
Patients With Cardiogenic Shock Undergoing Coronary Artery
Bypass Surgery. Insights From the Society of Thoracic
Surgeons National Cardiac Database.},
Journal = {Circulation},
Year = {2008},
Month = {February},
ISSN = {1524-4539},
Abstract = {BACKGROUND: -There exist few studies that characterize
contemporary clinical features and outcomes or risk factors
for operative mortality in cardiogenic shock (CS) patients
undergoing coronary artery bypass grafting (CABG). Methods
and Results-We evaluated data of 708 593 patients with and
without CS undergoing CABG enrolled in the Society of
Thoracic Surgeons National Cardiac Database (2002-2005).
Clinical, angiographic, and operative features and
in-hospital outcomes were evaluated in patients with and
without CS. Logistic regression was used to identify
predictors of operative mortality and to estimate weights
for an additive risk score. Patients with preoperative CS
constituted 14 956 (2.1%) of patients undergoing CABG yet
accounted for 14% of all CABG deaths. Operative mortality in
CS patients was high and surgery specific, rising from 20%
for isolated CABG to 33% for CABG plus valve surgery and 58%
for CABG plus ventricular septal repair. Although mortality
for CABG surgery overall declined significantly over time (P
for trend <0.0001), mortality for CS patients undergoing
CABG did not change significantly during the 4-year study
period (P=0.07). Factors associated with higher death risk
for CS patients undergoing CABG were identified by
multivariable analysis and summarized into a simple bedside
risk score (c statistic=0.74) that accurately stratified
those with low (<10%) to very high (>60%) mortality risk.
Conclusions-Patients with CS represent a minority of those
undergoing CABG yet have persistently high operative risks,
accounting for 14% of deaths in CABG patients. Estimation of
patient-specific risk of mortality is feasible with the
simplified additive risk tool developed in our study with
the use of routinely available preprocedural
data.},
Key = {fds151750}
}
@article{fds151758,
Title = {Feldman T, Glower D. Patient selection for percutaneous
mitral valve repair: insight from early clinical trial
applications. Nat Clin Pract Cardiovasc Med. 5:84-90,
2008 },
Year = {2008},
Key = {fds151758}
}
%% Goldberg, Richard L
@article{4775546,
Author = {Goldberg, R.L. and Smith, S.W.},
Title = {Multilayer piezoelectric ceramics for two-dimensional array
transducers},
Journal = {IEEE Trans. Ultrason. Ferroelectr. Freq. Control
(USA)},
Volume = {41},
Number = {5},
Pages = {761 - 71},
url = {http://dx.doi.org/10.1109/58.308512},
Keywords = {acoustic delay lines;biomedical ultrasonics;capacitance;ceramics;electric
impedance;focusing;lead compounds;piezoelectric
materials;ultrasonic delay lines;ultrasonic
transducers;},
Abstract = {In medical ultrasound imaging, 2-D array transducers have
become essential to implement dynamic focusing and
phase-correction in the elevation dimension as well as
real-time volumetric scanning. Unfortunately, the small size
of a 2-D array element results in a small clamped
capacitance and a large electrical impedance near resonance.
These elements have poor sensitivity because their impedance
is much higher than the electrical impedance of the transmit
and receive circuitry. Sensitivity can be improved by using
an N layer structure of PZT ceramic with the layers
connected acoustically in series and electrically in
parallel. For the multilayer ceramic (MLC), the damped
capacitance is multiplied by a factor of N<sup>2</sup> and
the electrical impedance by 1/N<sup>2</sup> compared to a
single layer element of the same dimensions. A 3×43
phased-array transducer has been fabricated using 3 layer
PZT-5H material. Each element had a thickness of 0.66 mm and
an area of 0.37×3.5 mm. The MLC was manufactured using
thick film technology with plated-through vias to
electrically interconnect the electrode layers. The
completed transducer was compared to a single layer control
array of similar dimensions. With a light epoxy backing and
a λ/4 matching layer, the MLC array elements had an
impedance of 100 Ω at series resonance of 2.25 MHz,
compared to 800 Ω for the control elements. The lower
impedance of the MLC elements resulted in a minimum
round-trip insertion loss of 24.0 dB, compared to an 34.1 dB
for the control array elements. These results were
consistent with KLM modeling. B-scan images were made of
cysts in a tissue-mimicking phantom and of the left kidney
in vivo. The images clearly showed a higher signal-to-noise
ratio for the MLC array compared to the control. As a
result, 2-D arrays made of multilayer ceramics can be used
to form images at a higher frequency and greater range than
single layer arrays},
Key = {4775546}
}
%% Grill, Warren M
@booklet{Lemay09,
Author = {M. A. Lemay and D. Grasse and W. M. Grill},
Title = {Hindlimb Endpoint Forces Predict Movement Direction Evoked
by Intraspinal Microstimulation in Cats},
Journal = {Ieee Transactions On Neural Systems And Rehabilitation
Engineering},
Volume = {17},
Number = {4},
Pages = {379 -- 389},
Year = {2009},
Month = {August},
ISSN = {1534-4320},
Abstract = {We measured the forces produced at the cat's hindpaw by
microstimulation of the lumbar spinal cord and the movements
resulting from those forces. We also measured the forces and
movements produced by co- and sequential activation of two
intraspinal sites. Isometric force responses were measured
at nine limb configurations with the paw attached to a force
transducer. The active forces elicited at different limb
configurations were summarized as patterns representing the
sagittal plane component of the forces produced at the paw
throughout the workspace. The force patterns divided into
the same distinct types found with the femur fixed. The
responses during simultaneous activation of two spinal sites
always resembled the response for activation of one of the
two sites, i.e., winner-take-all, and we did not observe
vectorial summation of the forces produced by activation of
each site individually as reported in chronic spinal
animals. The movements produced by activation of each of the
sites were consistent with the force orientations, and
different movements could be created by varying the sequence
of activation of individual sites. Our results highlight the
absence of a vectorial summation phenomenon during
intraspinal microstimulation in decerebrate animals, and the
preservation during movement of the orientation of isometric
forces.},
Key = {Lemay09}
}
@booklet{Woock09,
Author = {J. P. Woock and P. B. Yoo and W. M. Grill},
Title = {Intraurethral Stimulation Evokes Bladder Responses via 2
Distinct Reflex Pathways},
Journal = {Journal Of Urology},
Volume = {182},
Number = {1},
Pages = {366 -- 373},
Year = {2009},
Month = {July},
ISSN = {0022-5347},
Abstract = {Purpose: Recent animal studies have shown that selective
activation of pudendal nerve branches can evoke bladder
responses through 2 distinct reflex pathways. We examined
intraurethral electrical stimulation as a minimally invasive
means of selectively activating these pathways in the cat.
Materials and Methods: Bladder responses evoked by
intraurethral electrical stimulation were measured in
a-chloralose anesthetized male cats at different stimulation
frequencies, stimulation intensities and intraurethral
locations. Results: Intraurethral electrical stimulation
evoked inhibitory and excitatory bladder reflexes depending
on stimulation frequency and location. Stimulation in the
penile urethra 0 to 3 cm. from the urethral meatus at 33 Hz
evoked bladder contraction and at 10 Hz it evoked bladder
relaxation. These responses were abolished after bilateral
transection of the dorsal penile nerves. Stimulation in the
membranous urethra 5 to 7 cm from the urethral meatus at 2,
10 and 33 Hz evoked bladder contractions. These responses
were abolished after bilateral transection of the cranial
sensory nerves. Following acute spinal cord transection
bladder contractions were still evoked by 33 Hz stimulation
in the penile urethra but not by stimulation at any
frequency in the membranous urethra. Conclusions:
Intraurethral electrical stimulation selectively evoked
bladder responses by activating 2 distinct pudendal afferent
pathways. Responses depended on stimulation frequency and
location. Intraurethral electrical stimulation is a valid
means of determining the pathways involved in bladder
responses evoked by pudendal nerve stimulation.},
Key = {Woock09}
}
@booklet{Mahnam09,
Author = {A. Mahnam and S. M. R. Hashemi and W. M.
Grill},
Title = {Measurement of the current-distance relationship using a
novel refractory interaction technique},
Journal = {Journal Of Neural Engineering},
Volume = {6},
Number = {3},
Year = {2009},
Month = {June},
ISSN = {1741-2560},
Abstract = {It is important to know the spatial extent of neural
activation around the stimulating electrodes when using
extracellular electrical stimulation for the determination
of the structure and function of neural Circuit connections
or for the restoration Of function. The current-distance
relationship quantifies the relationship between the
threshold current for excitation of a neuron, I-th, and the
distance between the electrode and the neuron, r, with two
parameters: the offset, I-0, and the current-distance
constant, k, with a quadratic equation, I-th(r) = I-0 +
kr(2). We proposed a new method to determine the parameters
of the current-distance relationship, and thereby estimate
the spatial extent of activation, based on the refractory
interaction technique. Refractory interaction is a method
that exploits the interaction between the regions of
activation produced by two electrodes, when the second
stimulus is delivered while neurons activated by the first
electrode are in their refractory period. Computer
simulations of electrical stimulation of a population of
nerve fibers were used to determine the accuracy of the
method. The mean relative error in k was 19\% and in I-0 was
17\%, and the spatial extent of stimulation could be
determined with an absolute error of 19 mu m and a relative
error less than 11\%. Subsequently, the method was applied
to measure the current-distance properties of peripheral
motor nerve fibers and indicated that k = 27 mu A mm(-2) and
I-0 = 49 mu A. This method provided robust estimates of the
current-distance properties, and provides a means to
determine the spatial extent of activation by extracellular
stimulation.},
Key = {Mahnam09}
}
@booklet{Cantrell09,
Author = {M. B. Cantrell and W. M. Grill and S. M.
Klein},
Title = {Computer-based Finite Element Modeling of Insulated Tuohy
Needles Used in Regional Anesthesia},
Journal = {Anesthesiology},
Volume = {110},
Number = {6},
Pages = {1229 -- 1234},
Year = {2009},
Month = {June},
ISSN = {0003-3022},
Abstract = {Background: Differences in needle design may impact nerve
localization. This study evaluates the electrical properties
of two insulated Tuohy needles using computational finite
element modeling. Methods: Three-dimensional geometric
computer-based models were created representing two
18-gauge, insulated Tuohy needles: (1) with an exposed metal
tip and (2) with an insulated tip. The models were projected
in simulated human tissue. Using finite element methodology,
distributions of current-density were calculated. Voltages
in die modeled medium were calculated, and activation
patterns of a model nerve fiber around the tip of each
needle were estimated using the activating function.
Results: Maximum current density on the exposed-tip needle
occurred along the edge of the distal tip; the distal edge
was 1.7 times larger than the side edges and 3.5 times
larger than the proximal edge. Conversely, maximum current
density occurred along the proximal edge of the
insulated-tip Tuohy opening; the proximal edge was 1.9 times
larger than the side edges of the opening and 3.5 times
larger than the distal edge of the opening. Voltages
generated by the exposed-tip needle were larger and had a
wider spatial distribution than that of the insulated-tip
needle, which restricted to the area immediately adjacent to
the opening. Different changes in threshold were predicted
to excite a nerve fiber as the needles were rotated or
advanced toward the modeled nerve. Conclusions: The needles
displayed different asymmetric distributions of current
density and positional effects on threshold. If this
analysis is validated clinically, it may prove useful in
testing stimulating needles before clinical
application.},
Key = {Cantrell09}
}
@booklet{Kuncel09,
Author = {A. M. Kuncel and D. A. Turner and L. J. Ozelius and P. E.
Greene and W. M. Grill and M. A. Stacy},
Title = {Myoclonus and tremor response to thalamic deep brain
stimulation parameters in a patient with inherited
myoclonus-dystonia syndrome},
Journal = {Clinical Neurology And Neurosurgery},
Volume = {111},
Number = {3},
Pages = {303 -- 306},
Year = {2009},
Month = {April},
ISSN = {0303-8467},
Abstract = {We present a 74-year-old woman with inherited
myoclonus-dystonia, with predominant myoclonus and a novel
mutation in the E-sarcoglycan gene. The patient reports a
life-long history of rapid,jerking movements, most severe in
the upper extremities as well as a postural and action
tremor. Bilateral deep brain stimulation (DBS) of the
ventral intermediate nucleus of the thalamus was performed,
and the patient demonstrated moderate clinical improvement
in myoclonus. We studied the effects on myoclonus and tremor
of varying DBS frequency and amplitude. The frequency tuning
curve for myoclonus was similar to that of tremor,
suggesting similar mechanisms by which DBS alleviates both
disorders. (C) 2008 Elsevier B.V. All rights
reserved.},
Key = {Kuncel09}
}
@article{fds163249,
Author = {Grill WM and Norman SE and Bellamkonda RV},
Title = {Implanted neural interfaces: biochallenges and engineered
solutions},
Journal = {Annual Review of Biomedical Engineering},
Volume = {11},
Pages = {1-24},
Year = {2009},
Key = {fds163249}
}
@booklet{Yoo08,
Author = {P. B. Yoo and J. P. Woock and W. M. Grill},
Title = {Somatic innervation of the feline lower urinary
tract},
Journal = {Brain Research},
Volume = {1246},
Pages = {80 -- 87},
Year = {2008},
Month = {December},
ISSN = {0006-8993},
Abstract = {Electrical stimulation of pudendal nerve sensory pathways
can evoke excitatory bladder reflexes. However, the precise
peripheral innervation pattern of these somatic fibers
remains unclear. in adult male cats, we investigated
pudendal nerve innervation of the lower urinary tract (LUT)
by employing anatomical (Sihler's stain) and
electrophysiological (selective electrical nerve
stimulation) techniques. The stained specimens revealed
differential innervation of the proximal and distal urethrae
by fibers derived from the sensory branch of the pudendal
nerve. Cranial sensory branch fibers penetrated the prostate
to terminate along the intraluminal surface of the urethra,
whereas the dorsal nerve of the penis primarily innervated
the glans penis. Further examination of the proximal urethra
showed a separate pathway (deep perineal nerve) that
inserted directly into the external urethral sphincter.
These observations were confirmed electrophysiologically by
the measured urethral sphincter activity evoked in response
to selective nerve stimulation. Electrical activation of the
sensory pathway evoked only reflex (latency=8.9 +/- 1.1 ms)
contractions of the urethral muscle, whereas stimulation of
the perineal pathway elicited direct (latency=1.3 +/- 0.1
ms) responses. Our findings identify specific pudendal nerve
sensory pathways that can be used potentially to restore
bladder function in persons with spinal cord injury and also
treat LUT symptoms such as urinary retention. (C) 2008
Elsevier B.V. All rights reserved.},
Key = {Yoo08}
}
@booklet{Wongsarnpigoon08,
Author = {A. Wongsarnpigoon and W. M. Grill},
Title = {Computational modeling of epidural cortical
stimulation},
Journal = {Journal Of Neural Engineering},
Volume = {5},
Number = {4},
Pages = {443 -- 454},
Year = {2008},
Month = {December},
ISSN = {1741-2560},
Abstract = {Epidural cortical stimulation (ECS) is a developing therapy
to treat neurological disorders. However, it is not clear
how the cortical anatomy or the polarity and position of the
electrode affects current flow and neural activation in the
cortex. We developed a 3D computational model simulating ECS
over the precentral gyrus. With the electrode placed
directly above the gyrus, about half of the stimulus current
flowed through the crown of the gyrus while current density
was low alone, the banks deep in the sulci. Beneath the
electrode, neurons oriented perpendicular to the cortical
Surface were depolarized by anodic stimulation, and neurons
oriented parallel to the boundary were depolarized by
cathodic stimulation. Activation was localized to the crown
of the gyrus, and neurons on the banks deep in the sulci
were not polarized. During regulated voltage stimulation,
the magnitude of the activating function was inversely
proportional to the thickness of the CSF and dura. During
regulated Current stimulation, the activating function was
not sensitive to the thickness of the dura but was slightly
more sensitive than during regulated voltage stimulation to
the thickness of the CSF. Varying the width of the gyrus and
the position of the electrode altered the distribution of
the activating function due to changes in the orientation of
the neurons beneath the electrode. Bipolar stimulation,
although often used in clinical practice, reduced spatial
selectivity as well as selectivity for neuron
orientation.},
Key = {Wongsarnpigoon08}
}
@booklet{Dorval08,
Author = {A. D. Dorval and G. S. Russo and T. Hashimoto and W. Xu and W. M. Grill and J. L. Vitek},
Title = {Deep Brain Stimulation Reduces Neuronal Entropy in the
MPTP-Primate Model of Parkinson's Disease},
Journal = {Journal Of Neurophysiology},
Volume = {100},
Number = {5},
Pages = {2807 -- 2818},
Year = {2008},
Month = {November},
ISSN = {0022-3077},
Abstract = {Dorval AD, Russo GS, Hashimoto T, Xu W, Grill WM, Vitek JL.
Deep brain stimulation reduces neuronal entropy in the
MPTP-primate model of Parkinson's disease. J Neurophysiol
100: 2807-2818, 2008. First published September 10, 2008;
doi: 10.1152/jn.90763.2008. High-frequency stimulation (HFS)
of the subthalamic nucleus (STN) or internal segment of the
globus pallidus is a clinically successful treatment for the
motor symptoms of Parkinson's disease. However, the
mechanisms by which HFS alleviates these symptoms are not
understood. Whereas initial studies focused on HFS-induced
changes in neuronal firing rates, recent studies suggest
that changes in patterns of neuronal activity may correlate
with symptom alleviation. We hypothesized that effective STN
HFS reduces the disorder of neuronal firing patterns in the
basal ganglia thalamic circuit, minimizing the pathological
activity associated with parkinsonism. Stimulating leads
were implanted in the STN of two rhesus monkeys rendered
parkinsonian by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine
(MPTP). Action potentials were recorded from neurons of the
internal and external globus pallidus and the motor thalamus
(ventralis anterior, ventralis lateralis pars oralis, and
ventralis posterior lateralis pars oralis) during HFS that
reduced motor symptoms and during clinically ineffective
low-frequency stimulation (LFS). Firing pattern entropy was
calculated from the recorded spike times to quantify the
disorder of the neuronal activity. The firing pattern
entropy of neurons within each region of the pallidum and
motor thalamus decreased in response to HFS (n $>$= 18 and P
$<$= 0.02 in each region), whereas firing rate changes were
specific to pallidal neurons only. In response to LFS,
firing rates were unchanged, but firing pattern entropy
increased throughout the circuit (n $>$= 24 and P $<$=
10(-4) in each region). These data suggest that the clinical
effectiveness of HFS is correlated with, and potentially
mediated by, a regularization of the pattern of neuronal
activity throughout the basal ganglia thalamic
circuit.},
Key = {Dorval08}
}
@booklet{Cooper08,
Author = {S. E. Cooper and A. M. Kuncel and B. R. Wolgamuth and A. R.
Rezai and W. M. Grill},
Title = {A Model Predicting Optimal Parameters for Deep Brain
Stimulation in Essential Tremor},
Journal = {Journal Of Clinical Neurophysiology},
Volume = {25},
Number = {5},
Pages = {265 -- 273},
Year = {2008},
Month = {October},
ISSN = {0736-0258},
Abstract = {In nine patients with essential tremor (14 thalami), the
authors varied frequency, voltage, and pulsewidth of
thalamic deep brain stimulation, and quantified postural
tremor. Low frequency stimulation aggravated tremor: the
effect increased with increasing voltage. High frequency
stimulation had a U-shaped relation to voltage, with minimum
tremor at an optimal voltage characteristic of c the
individual thalamus and increases in voltage beyond the
optimum reduced tremor suppression. Based on the hypothesis
that tremor response to deep brain stimulation resulted
front two competing processes, the authors successfully
modeled the relationship of tremor to voltage and frequency
Of stimulation using a mathematical model. The optimum
voltage predicted by the model agreed with the empirically
measured value. Moreover, the model made accurate
predictions at high stimulation frequency based on
measurements trade at IOW stimulation frequency. Our results
indicate there is an optimal voltage for tremor Suppression
by thalamic deep brain stimulation in most patients with
essential tremor. The Optimum varies across patients, and
this is related to electrode position. A mathematical model
based oil "competing processes" successfully predicts
optimum voltage in individual patients. This supports a
competing processes model of deep brain stimulation
effects.},
Key = {Cooper08}
}
@booklet{Kuncel08,
Author = {A. M. Kuncel and S. E. Cooper and W. M. Grill},
Title = {A method to estimate the spatial extent of activation in
thalamic deep brain stimulation},
Journal = {Clinical Neurophysiology},
Volume = {119},
Number = {9},
Pages = {2148 -- 2158},
Year = {2008},
Month = {September},
ISSN = {1388-2457},
Abstract = {Objective: The goal of this study was to develop, evaluate,
and apply a method to quantity the unknown spatial extent of
activation in deep brain stimulation (DBS) of the ventral
intermedius nucleus (Vim) of the thalamus. Methods: The
amplitude-distance relationship and the threshold amplitudes
to elicit clinical responses were combined to estimate the
unknown amplitude-distance constant and the distance between
the electrode and the border between the Vim and the
ventrocaudal nucleus (Vc) of the thalamus. We tested the
sensitivity of the method to errors in the input parameters,
and subsequently applied the method to estimate the
amplitude-distance constant from clinically-measured
threshold amplitudes. Results: The method enabled estimation
of the amplitude-distance constant with a median squared
error of 0.07-0.23 V/mm(2) and provided an estimate of the
distance between the electrode and the Vc/Vim border with a
median squared error of 0.01-0.04 mm. Application of the
method to clinically-measured threshold amplitudes to elicit
paresthesias estimated the amplitude-distance constant to be
0.22 V/mm(2). Conclusions: The method enabled robust
quantification of the spatial extent of activation in
thalamic DBS and predicted that stimulation amplitudes of
1-3.5 V would produce a mean effective radius of activation
of 2.0-3.9 mm. Significance: Knowing the spatial extent of
activation may improve methods of electrode placement and
stimulation parameter selection in DBS. (C) 2008
International Federation of Clinical Neurophysiology.
Published by Elsevier Ireland Ltd. All rights
reserved.},
Key = {Kuncel08}
}
@booklet{Mahnam08,
Author = {A. Mahnam and S. M. R. Hashemi and W. M.
Grill},
Title = {Computational evaluation of methods for measuring the
spatial extent of neural activation},
Journal = {Journal Of Neuroscience Methods},
Volume = {173},
Number = {1},
Pages = {153 -- 164},
Year = {2008},
Month = {August},
ISSN = {0165-0270},
Abstract = {Knowing of the spatial extent of neural activation around
extracellular stimulating electrodes is necessary to ensure
that only the desired neurons are activated or to determine
which neurons are responsible for an observed response.
Various approaches have been used to estimate the
current-distance relationship and thereby the spatial extent
of activation resulting from extracellular stimulation.
However, these approaches all require underlying assumptions
and simplifications, and since the actual extent of
activation cannot be directly measured, the impact of
deviations from these assumptions cannot)e determined. We
implemented a computer-based model of excitation of a
population of nerve fibers and used the model to evaluate a
range of approaches proposed for measuring the spatial
extent of neural activation. The estimates with each method
were compared with measurements of the true spatial extent
of activation that were accessible in the simulations to
quantify the accuracy of the estimates and to determine the
dependence of accuracy on measurement parameters
(interelectrode distance, stimulation amplitude, noise). A
newly proposed method, based on the refractory interaction
technique, provided the most accurate and most robust
estimates of the spatial extent of neural activation. (C)
2008 Elsevier B.V. All rights reserved.},
Key = {Mahnam08}
}
@booklet{Yoo08a,
Author = {P. B. Yoo and J. P. Woock and W. M. Grill},
Title = {Bladder activation by selective stimulation of pudendal
nerve afferents in the cat},
Journal = {Experimental Neurology},
Volume = {212},
Number = {1},
Pages = {218 -- 225},
Year = {2008},
Month = {July},
ISSN = {0014-4886},
Abstract = {Bladder contractions evoked by pudendal nerve stimulation in
both spinal intact and spinal transected cats support the
possibility of restoring urinary function in persons with
chronic spinal cord injury (SCI). However, electrically
evoked bladder responses in persons with SCI were limited to
transient contractions at relatively low pressures. This
prompted the present study, which presents a detailed
quantification of the responses evoked by selective
stimulation of individual branches of the pudendal nerve at
different stimulation frequencies. In spinal intact cats
anesthetized with alpha-chloralose, selective
frequency-dependent electrical activation of the sensory (2
Hz $<$= f $<$= 550 Hz), cranial sensory (f $<$= 5 Hz),
dorsal genital (f $<$= 20 Hz) and rectal perineal (f $<$= 10
Hz) branches of the pudendal nerve evoked sustained bladder
contractions dependent on the stimulation frequency.
Contractions evoked by selective electrical Stimulation
resulted in significant increases in voiding efficiency
Compared to bladder emptying by distension-evoked
contractions (P-ANOVA$<$0.05). Acute spinal transection
abolished reflex bladder contractions evoked by low
frequency stimulation of the cranial sensory or rectal
perineal branches, whereas contractions evoked by high
frequency stimulation of the dorsal genital branch remained
intact. This study presents evidence for two distinct
micturition pathways (spino-bulbo-spinal vs. spinal
reflexes) activated by selective afferent pudendal nerve
stimulation, the latter of which may be applied to restore
bladder function in persons with SCI. (C) 2008 Elsevier Inc.
All rights reserved.},
Key = {Yoo08a}
}
@booklet{Woock08,
Author = {J. P. Woock and P. B. Yoo and W. M. Grill},
Title = {Activation and inhibition of the micturition reflex by
penile afferents in the cat},
Journal = {American Journal Of Physiology-regulatory Integrative And
Comparative Physiology},
Volume = {294},
Number = {6},
Pages = {R1880 -- R1889},
Year = {2008},
Month = {June},
ISSN = {0363-6119},
Abstract = {Coordination of the urinary bladder and the external
urethral sphincter is controlled by descending projections
from the pons and is also subject to modulation by segmental
afferents. We quantified the effects on the micturition
reflex of sensory inputs from genital afferents traveling in
the penile component of the somatic pudendal nerve by
electrical stimulation of the dorsal nerve of the penis
(DNP) in alpha-chloralose anesthetized male cats. Depending
on the frequency of stimulation (range, 1-40 Hz), activation
of penile afferents either inhibited contractions of the
bladder and promoted urine storage or activated the bladder
and produced micturition. Stimulation of the DNP at 5-10 Hz
inhibited distension-evoked contractions and increased the
maximum bladder capacity before incontinence. Conversely,
stimulation at 33 and 40 Hz augmented distension-evoked
contractions. When the bladder was filled above a threshold
volume (70\% of the volume necessary for distension-evoked
contractions), stimulation at 20-40 Hz activated de novo the
micturition reflex and elicited detrusor contractions that
increased voiding efficiency compared with distension-evoked
voiding. Electrical stimulation of the DNP with a cuff
electrode or percutaneous wire electrode produced similar
results. The ability to evoke detrusor contractions by
activation of the DNP was preserved following acute spinal
cord transection. These results demonstrate a clear role of
genital afferents in modulating the micturition reflex and
suggest the DNP as a potential target for functional
restoration of bladder control using electrical
stimulation.},
Key = {Woock08}
}
@booklet{Peng08,
Author = {C. W. Peng and J. J. J. Chen and C. L. Cheng and W. M.
Grill},
Title = {Improved bladder emptying in urinary retention by electrical
stimulation of pudendal afferents},
Journal = {Journal Of Neural Engineering},
Volume = {5},
Number = {2},
Pages = {144 -- 154},
Year = {2008},
Month = {June},
ISSN = {1741-2560},
Abstract = {Urinary retention is the inability to empty the bladder
completely, and may result from bladder hypocontractility,
increases in outlet resistance or both. Chronic urinary
retention can lead to several urological complications and
is often refractory to pharmacologic, behavioral and
surgical treatments. We sought to determine whether
electrical stimulation of sensory fibers in the pudendal
nerve could engage an augmenting reflex and thereby improve
bladder emptying in an animal model of urinary retention. We
measured the efficiency of bladder emptying with and without
concomitant electrical stimulation of pudendal nerve
afferents in urethane-anesthetized rats. Voiding efficiency
(VE = voided volume/initial volume) was reduced from 72 +/-
7\% to 29 +/- 7\% following unilateral transection of the
sensory branch of the pudendal nerve (UST) and from 70 +/-
5\% to 18 +/- 4\% following bilateral transection (BST).
Unilateral electrical stimulation of the proximal transected
sensory pudendal nerve during distention-evoked voiding
contractions significantly improved VE. Low-intensity
stimulation at frequencies of 1-50 Hz increased VE to
40-51\% following UST and to 39-49\% following,BST, while
high-intensity stimulation was ineffective at increasing VE.
The increase in VE was mediated by increases in the duration
of distention-evoked voiding bladder contractions, rather
than increases in contraction amplitude. These results are
consistent with an essential role for pudendal sensory
feedback in efficient bladder emptying, and raise the
possibility that electrical activation of pudendal nerve
afferents may provide a new approach to restore efficient
bladder emptying in persons with urinary
retention.},
Key = {Peng08}
}
@booklet{Birdno08,
Author = {M. J. Birdno and A. M. Kuncel and A. D. Dorval and D. A.
Turner and W. M. Grill},
Title = {Tremor varies as a function of the temporal regularity of
deep brain stimulation},
Journal = {Neuroreport},
Volume = {19},
Number = {5},
Pages = {599 -- 602},
Year = {2008},
Month = {March},
ISSN = {0959-4965},
Abstract = {The frequency of stimulation is one of the primary factors
determining the effectiveness of deep brain stimulation
(DBS) in relieving tremor. DBS efficacy, however, may depend
not only on the average frequency of stimulation, but also
on the temporal pattern of stimulation. We conducted
intraoperative measurements of the effect of temporally
irregular DBS (nonconstant interpulse intervals) on tremor.
As the coefficient of variation of irregular high frequency
DBS trains increased, they became less effective at reducing
tremor (mixed effects regression model, P$<$0.04). These
data provide evidence that the effects of DBS are dependent
not only on the average frequency of DBS, but also on the
regularity of the temporal spacing of DBS
pulses.},
Key = {Birdno08}
}
@booklet{Bossetti08,
Author = {C. A. Bossetti and M. J. Birdno and W. M.
Grill},
Title = {Analysis of the quasi-static approximation for calculating
potentials generated by neural stimulation},
Journal = {Journal Of Neural Engineering},
Volume = {5},
Number = {1},
Pages = {44 -- 53},
Year = {2008},
Month = {March},
ISSN = {1741-2560},
Abstract = {In models of electrical stimulation of the nervous system,
the electric potential is typically calculated using the
quasi-static approximation. The quasi-static approximation
allows Maxwell's equations to be simplified by ignoring
capacitive, inductive and wave propagation contributions to
the potential. While this simplification has been validated
for bioelectric sources, its application to rapid
stimulation pulses, which contain more high-frequency power,
may not be appropriate. We compared the potentials
calculated using the quasi-static approximation with those
calculated from the exact solution to the inhomogeneous
Helmholtz equation. The mean absolute errors between the two
potential calculations were limited to 5-13\% for pulse
widths commonly used for neural stimulation (25 mu s-1 ms).
We also quantified the excitation properties of
extracellular point source stimulation of a myelinated nerve
fiber model using potentials calculated from each method.
Deviations between the strength-duration curves for
potentials calculated using the quasi-static (sigma = 0. 105
S m(-1)) and Helmholtz approaches ranged from 3 to 16\%,
with the minimal error occurring for 100 its pulses.
Differences in the threshold-distance curves for the two
calculations ranged from 0 to 9\%, for the same value of
quasi-static conductivity. A sensitivity analysis of the
material parameters revealed that the potential was much
more strongly dependent on the conductivity than on the
permittivity. These results indicate that for commonly used
stimulus pulse parameters, the exact solution for the
potential can be approximated by quasi-static
simplifications only for appropriate values of
conductivity.},
Key = {Bossetti08}
}
@booklet{Peng08a,
Author = {C. W. Peng and J. J. J. Chen and C. L. Cheng and W. M.
Grill},
Title = {Role of pudendal afferents in voiding efficiency in the
rat},
Journal = {American Journal Of Physiology-regulatory Integrative And
Comparative Physiology},
Volume = {294},
Number = {2},
Pages = {R660 -- R672},
Year = {2008},
Month = {February},
ISSN = {0363-6119},
Abstract = {The reciprocal activities of the bladder and external
urethral sphincter (EUS) are coordinated by descending
projections from the pontine micturition center but are
subjected to modulation by peripheral afferent inputs.
Transection of the somatic pudendal nerve innervating the
striated EUS decreases voiding efficiency and increases
residual urine in the rat. The reduction in voiding
efficiency was attributed to the lack of phasic bursting
activity of the EUS following denervation. However,
transection of the pudendal nerve also eliminates somatic
sensory feedback that may play a role in voiding. We
hypothesized that feedback from pudendal afferents is
required for efficient voiding and that the loss of pudendal
sensory activity contributes to the observed reduction in
voiding efficiency following pudendal nerve transection.
Quantitative cystometry in urethane anesthetized female rats
following selective transection of pudendal nerve branches,
following chemical modulation of urethral afferent activity,
and following neuromuscular blockade revealed that pudendal
nerve afferents contributed to efficient voiding. Sensory
feedback augmented bladder contraction amplitude and
duration, thereby increasing the driving force for urine
expulsion. Second, sensory feedback was necessary to pattern
appropriately the EUS activity into alternating bursts and
quiescence during the bladder contraction. These findings
demonstrate that the loss of pudendal sensory activity
contributes to the reduction in voiding efficiency observed
following pudendal nerve transection, and illustrate the
importance of urethral sensory feedback in regulating
bladder function.},
Key = {Peng08a}
}
@booklet{Kayagil08,
Author = {T. A. Kayagil and J. P. Grimes and W. M.
Grill},
Title = {Mechanisms underlying reversal of motor unit activation
order in electrically evoked contractions after spinal cord
injury},
Journal = {Muscle \& Nerve},
Volume = {37},
Number = {2},
Pages = {210 -- 218},
Year = {2008},
Month = {February},
ISSN = {0148-639X},
Abstract = {Extracellular stimulation normally activates larger-diameter
axons, innervating motor units producing higher force, at
lower stimulation intensities than required to activate
small-diameter axons innervating motor units producing low
force. However, activation of weaker thenar motor units at
lower stimulation intensities than required to activate
strong motor units has been reported during extracellular
stimulation of the median nerve in persons with chronic
cervical spinal cord injury. We used a computational model
that reproduced this experiment to identify the potential
mechanisms for the observed reversal of the inverse
recruitment order, including preferential death of large
motoneurons, demyelination and remyelination, and
denervation and reinnervation of muscle fibers. Five sets of
simulations assessed these mechanisms with seven simulated
subjects. Preferential reinnervation, with small-diameter
axons reinnervating more abandoned muscle fibers than
larger-diameter axons, accounted for the apparent reversal
of the inverse recruitment order observed previously.
Preferential death of larger axons enhanced the reversal,
but alone could not account for the observed reversal.
Further, demyelination and remyelination, even in an extreme
case and when combined with preferential death of large
motoneurons, could not reproduce the reversal of inverse
recruitment order. Thus, the apparent reversal of the
inverse recruitment order was not a reversal of activation
order across different diameter nerve fibers, but rather was
a consequence of the redistributed force-generating capacity
of the motor units resulting from denervation and
reinnervation.},
Key = {Kayagil08}
}
@booklet{Grill08,
Author = {W. M. Grill and M. B. Cantrell and M. S.
Robertson},
Title = {Antidromic propagation of action potentials in branched
axons: implications for the mechanisms of action of deep
brain stimulation},
Journal = {Journal Of Computational Neuroscience},
Volume = {24},
Number = {1},
Pages = {81 -- 93},
Year = {2008},
Month = {February},
ISSN = {0929-5313},
Abstract = {Electrical stimulation of the central nervous system creates
both orthodromically propagating action potentials, by
stimulation of local cells and passing axons, and
antidromically propagating action potentials, by stimulation
of presynaptic axons and terminals. Our aim was to
understand how antidromic action potentials navigate through
complex arborizations, such as those of thalamic and basal
ganglia afferents-sites of electrical activation during deep
brain stimulation. We developed computational models to
study the propagation of antidromic action potentials past
the bifurcation in branched axons. In both unmyelinated and
myelinated branched axons, when the diameters of each axon
branch remained under a specific threshold (set by the
antidromic geometric ratio), antidromic propagation occurred
robustly; action potentials traveled both antidromically
into the primary segment as well as "re-orthodromically"
into the terminal secondary segment. Propagation occurred
across a broad range of stimulation frequencies, axon
segment geometries, and concentrations of extracellular
potassium, but was strongly dependent on the geometry of the
node of Ranvier at the axonal bifurcation. Thus, antidromic
activation of axon terminals can, through axon collaterals,
lead to widespread activation or inhibition of targets
remote from the site of stimulation. These effects should be
included when interpreting the results of functional imaging
or evoked potential studies on the mechanisms of action of
DBS.},
Key = {Grill08}
}
@booklet{Birdno08a,
Author = {M. J. Birdno and W. M. Grill},
Title = {Mechanisms of deep brain stimulation in movement disorders
as revealed by changes in stimulus frequency},
Journal = {Neurotherapeutics},
Volume = {5},
Number = {1},
Pages = {14 -- 25},
Year = {2008},
Month = {January},
ISSN = {1933-7213},
Abstract = {Deep brain stimulation (DBS) is an established treatment for
symptoms in movement disorders and is under investigation
for symptom management in persons with psychiatric disorders
and epilepsy. Nevertheless, there remains disagreement
regarding the physiological mechanisms responsible for the
actions of DBS, and this lack of understanding impedes both
the design of DBS systems for treating novel diseases and
the effective tuning of current DBS systems. Currently
available data indicate that effective DBS overrides
pathological bursts, low frequency oscillations,
synchronization, and disrupted firing patterns present in
movement disorders, and replaces them with more regularized
firing. Although it is likely that the specific mechanism(s)
by which DBS exerts its effects varies between diseases and
target nuclei, the overriding of pathological activity
appears to be ubiquitous. This review provides an overview
of changes in motor symptoms with changes in DBS frequency
and highlights parallels between the changes in motor
symptoms and the changes in cellular activity that appear to
underlie the motor symptoms.},
Key = {Birdno08a}
}
@booklet{Goldman08,
Author = {H. B. Goldman and C. L. Amundsen and J. Mangel and J. Grill and M. Bennett and K. J. Gustafson and W. M.
Grill},
Title = {Dorsal genital nerve stimulation for the treatment of
overactive bladder symptoms},
Journal = {Neurourology And Urodynamics},
Volume = {27},
Number = {6},
Pages = {499 -- 503},
Year = {2008},
ISSN = {0733-2467},
Abstract = {Aim: To evaluate percutaneous placement of electrodes
adjacent to the dorsal genital nerve (DGN) and measure the
effects of electrical stimulation on symptoms of urge
incontinence during 1 week of home use. Methods:
Prospective, multicenter study. Subjects with urge
incontinence underwent percutaneous placement of an
electrode using local anesthetic. Test stimulation was
applied to confirm electrode placement and cystometry was
conducted with and without application of electrical
stimulation. A 7-day testing period with the electrode
connected to an external pulse generator was performed and
was followed by a 3-day post-treatment test period. Bladder
diaries, 24 hr pad tests, and adverse event queries were
obtained. Results: Twenty-one women were enrolled with an
average age of 52.7 years and average duration of
incontinence of 6 years. Percutaneous electrode placement
required 5-10 min and was well tolerated. There was no
relationship between the acute effects of stimulation on
cystometry and the results during home use. Pad weight was
reduced by $>$= 50\% in 13 of 17 subjects (76\%) (4 did not
complete 24 hr pad testing) and 47\% of subjects reported
$>$= 50\% reduction in incontinence episodes. Of the
subjects who reported severe urgency at baseline, 81\%
experienced a 50\% or greater improvement. Seven subjects
experienced nine adverse events ranging from skin irritation
to pain and bruising around the electrode exit site.
Conclusions: Electrodes to stimulate the DGN can be placed
percutaneously and a home testing period showed a reduction
in overactive bladder symptoms with DGN stimulation.},
Key = {Goldman08}
}
@article{fds144840,
Author = {Birdno MJ and Kuncel AM and Dorval AD and Turner DA and Grill
WM},
Title = {Tremor varies as a function of the temporal regularity of
deep brain stimulation},
Journal = {NeuroReport},
Volume = {19},
Pages = {599-602},
Year = {2008},
Key = {fds144840}
}
@article{fds144841,
Author = {Peng CW and Chen JJ and Cheng CL and Grill WM},
Title = {Role of pudendal afferents in voiding efficiency in the
rat},
Journal = {American Journal of Physiology-Regulatory, Integrative, and
Comparative Physiology},
Volume = {294},
Pages = {660-672},
Year = {2008},
Key = {fds144841}
}
@article{fds144842,
Author = {Kayagil TA and Grimes JP and Grill WM},
Title = {Mechanisms underlying reversal of motor unit activation
order during electrically evoked contractions in spinal cord
injury},
Journal = {Muscle & Nerve},
Volume = {37},
Pages = {210-218},
Year = {2008},
Key = {fds144842}
}
@article{fds144843,
Author = {Grill WM and Cantrell MB and Robertson MS},
Title = {Antidromic propagation of action potential in branched
axons: implications for the mechanisms of action of deep
brain stimulation},
Journal = {Journal of Computational Neuroscience},
Volume = {24},
Pages = {81-93},
Year = {2008},
Key = {fds144843}
}
@article{fds144844,
Author = {Birdno MJ and Grill WM},
Title = {Mechanisms of deep brain stimulation in movement disorders
as revealed by changes in stimulus frequency},
Journal = {Neurotherapeutics},
Volume = {5},
Pages = {14-25},
Year = {2008},
Key = {fds144844}
}
@article{fds144845,
Author = {Bossetti CA and Birdno MJ and Grill WM},
Title = {Analysis of the quasi-static approximation for calculating
potentials generated by neural stimulation},
Journal = {Journal of Neural Engineering},
Volume = {5},
Pages = {44-53},
Year = {2008},
Key = {fds144845}
}
@article{8576752,
Author = {Wenzel, B.J. and Boggs, J.W. and Gustafson, K.J. and Grill,
W.M.},
Title = {Detecting the onset of hyper-reflexive bladder contractions
from the electrical activity of the pudendal
nerve},
Journal = {IEEE Trans. Neural Syst. Rehabil. Eng. (USA)},
Volume = {13},
Number = {3},
Pages = {428 - 35},
url = {http://dx.doi.org/10.1109/TNSRE.2005.848355},
Keywords = {bioelectric phenomena;medical signal detection;neurophysiology;},
Abstract = {Individuals with a spinal cord injury or neurological
disorders may develop involuntary bladder contractions at
low volumes (bladder hyper-reflexia), which can lead to
significant health problems. Present devices can inhibit
unwanted contractions through continuous stimulation, but do
not enable conditional stimulation only at the onset of
bladder contractions. The objectives of this study were to
determine the relationship between the electrical activity
of the pudendal nerve trunk (PNT) and bladder pressure
during hyper-reflexive bladder contractions and to determine
whether PNT activity could be used to detect the
contractions. Bladder pressure and PNT electroneurogram
(ENG) were recorded in eight adult male cats. The PNT ENG
activity increased at the onset of a bladder contraction and
the activity during bladder contractions was greater than
during the intercontraction interval (p<0.001). Three
algorithms were developed to detect the onset of a bladder
contraction from the PNT ENG activity. A cumulative sum
(CUSUM) algorithm performed better than either a constant
threshold or a dynamic threshold algorithm, and enabled
detection of reflex bladder contractions from the PNT ENG an
average of 1.2 s after the contraction started with an
average increase in pressure 7.1 cmH<sub>2</sub>·O
when evaluated on data not used to set detection parameters.
These data demonstrated that recordings from the PNT could
be used to detect hyper-reflexive bladder contractions and
provide a signal to control closed-loop inhibitory
stimulation},
Key = {8576752}
}
%% Guilak, Farshid
@article{7435933,
Author = {Flahiff, C.M. and Narmoneva, D.A. and Huebner, J.L. and Kraus, V.B. and Guilak, F. and Setton, L.A.},
Title = {Osmotic loading to determine the intrinsic material
properties of guinea pig knee cartilage},
Journal = {J. Biomech. (UK)},
Volume = {35},
Number = {9},
Pages = {1285 - 90},
url = {http://dx.doi.org/10.1016/S0021-9290(02)00079-9},
Keywords = {biochemistry;biological techniques;biological
tissues;biomechanics;elastic moduli;fluorescence;optical
microscopy;osmosis;swelling;},
Abstract = {Few methods exist to study cartilage mechanics in small
animal joints due to the difficulties associated with
handling small tissue samples. In this study, we apply an
osmotic loading method to quantify the intrinsic material
properties of articular cartilage in small animal joints.
Cartilage samples were studied from the femoral condyle and
tibial plateau of two-month old guinea pigs. Swelling
strains were measured using confocal fluorescence scanning
microscopy in samples subjected to osmotic loading. A
histochemical staining method was developed and calibrated
for quantification of negative fixed charge density in
guinea pig cartilage. Site-matched swelling strain data and
fixed charge density values were then used with a triphasic
theoretical model for cartilage swelling to determine the
uniaxial modulus of the cartilage solid matrix. Moduli
obtained in this study (7.2 MPa femoral condyle; 10.8 MPa,
tibial plateau) compare well with previously reported values
for the tensile moduli of human and other animal cartilages
determined from uniaxial tension experiments. This study
provides the first available data for material properties
and fixed charge density in cartilage from the guinea pig
knee and suggests a promising method for tracking changes in
cartilage mechanics in small animal models of
degeneration},
Key = {7435933}
}
%% Henriquez, Craig S
@booklet{Jacquemet09,
Author = {V. Jacquemet and C. S. Henriquez},
Title = {Genesis of complex fractionated atrial electrograms in zones
of slow conduction: A computer model of microfibrosis},
Journal = {Heart Rhythm},
Volume = {6},
Number = {6},
Pages = {803 -- 810},
Year = {2009},
Month = {June},
ISSN = {1547-5271},
Abstract = {BACKGROUND Complex fractionated atrial electrograms are used
as potential targets for catheter ablation therapy of atrial
fibrillation. Although fibrosis has been associated with the
presence of fractionated electrograms, characterizing the
substrate through the inspection of electrograms is
challenging. OBJECTIVE This study sought to determine how
progression of microfibrosis and slow conduction affect
electrogram morphology. METHODS A microstructure computer
model representing a monolayer of cardiac cells was
developed. Slow conduction was induced by: (1) sodium
channel blockade, (2) uniform reduction in cell-to-cell
coupling, and (3) microfibrosis incorporated as a set of
collagenous septa disconnecting transverse coupling. The
density (0 to 30\%) and length (30 to 945 mu m) of these
collagenous septa were varied. Unipolar and bipolar
electrograms were computed during paced rhythm for a set of
electrodes with different tip sizes. RESULTS The analysis of
unipolar electrograms with realistic temporal and spatial
filtering showed that increasing the density and length of
collagenous septa decreased conduction velocity by up to
75\% and increased the amount of fractionation (up to 14
deflections) and asymmetry of the electrograms. In contrast,
stow conduction induced by sodium channel blockade or
uniformly reduced coupling did not result in electrogram
fractionation. When a Larger electrode was used, electrogram
amplitude was smaller and fractionation increased in a
substrate-dependent way. CONCLUSION Microscale obstacles
cause significant changes to electrogram waveforms.
Conduction velocity and electrogram amplitude and degree of
fractionation can be used to discriminate the nature of the
substrate and characteristics of fibrosis, giving rise to
stow conduction.},
Key = {Jacquemet09}
}
@booklet{Kayagil09,
Author = {T. A. Kayagil and O. Bai and C. S. Henriquez and P. Lin and S. J. Furlani and S. Vorbach and M. Hallett},
Title = {A binary method for simple and accurate two-dimensional
cursor control from EEG with minimal subject
training},
Journal = {Journal Of Neuroengineering And Rehabilitation},
Volume = {6},
Year = {2009},
Month = {May},
ISSN = {1743-0003},
Abstract = {Background: Brain-computer interfaces (BCI) use
electroencephalography (EEG) to interpret user intention and
control an output device accordingly. We describe a novel
BCI method to use a signal from five EEG channels
(comprising one primary channel with four additional
channels used to calculate its Laplacian derivation) to
provide two-dimensional (2-D) control of a cursor on a
computer screen, with simple threshold-based binary
classification of band power readings taken over pre-defined
time windows during subject hand movement. Methods: We
tested the paradigm with four healthy subjects, none of whom
had prior BCI experience. Each subject played a game wherein
he or she attempted to move a cursor to a target within a
grid while avoiding a trap. We also present supplementary
results including one healthy subject using motor imagery,
one primary lateral sclerosis (PLS) patient, and one healthy
subject using a single EEG channel without Laplacian
derivation. Results: For the four healthy subjects using
real hand movement, the system provided accurate cursor
control with little or no required user training. The
average accuracy of the cursor movement was 86.1\% (SD
9.8\%), which is significantly better than chance (p =
0.0015). The best subject achieved a control accuracy of
96\%, with only one incorrect bit classification out of 47.
The supplementary results showed that control can be
achieved under the respective experimental conditions, but
with reduced accuracy. Conclusion: The binary method
provides naive subjects with real-time control of a cursor
in 2-D using dichotomous classification of synchronous EEG
band power readings from a small number of channels during
hand movement. The primary strengths of our method are
simplicity of hardware and software, and high accuracy when
used by untrained subjects.},
Key = {Kayagil09}
}
@booklet{Jacquemet09a,
Author = {V. Jacquemet and C. S. Henriquez},
Title = {Modulation of Conduction Velocity by Nonmyocytes in the Low
Coupling Regime},
Journal = {Ieee Transactions On Biomedical Engineering},
Volume = {56},
Number = {3},
Pages = {893 -- 896},
Year = {2009},
Month = {March},
ISSN = {0018-9294},
Abstract = {This paper explores the conditions under which nonmyocytes,
when electrically coupled to myocytes, act as a passive load
during the depolarization phase. Using theoretical arguments
and numerical simulations in a tissue incorporating
fibroblasts, the passive load approximation is shown to be
accurate at low coupling conductances ($<$2 nS). In this
case, the effect on conduction velocity can be expressed as
a function of the elevation in resting potential and the
coupling only.},
Key = {Jacquemet09a}
}
@booklet{Ying08,
Author = {W. J. Ying and D. J. Rose and C. S. Henriquez},
Title = {Efficient Fully Implicit Time Integration Methods for
Modeling Cardiac Dynamics},
Journal = {Ieee Transactions On Biomedical Engineering},
Volume = {55},
Number = {12},
Pages = {2701 -- 2711},
Year = {2008},
Month = {December},
ISSN = {0018-9294},
Abstract = {Implicit methods are well known to have greater stability
than explicit methods for stiff systems, but they often are
not used In practice due to perceived computational
complexity. This paper applies the backward Enter (BE)
method and a second-order one-step two-stage composite
backward differentiation formula (C-BDF2) for the monodomain
equations arising from mathematically modeling the
electrical activity of the heart. The C-BDF2 scheme is an
L-stable Implicit time integration method and easily
implementable. It uses the simplest forward Euler and BE
methods as fundamental building blocks. The nonlinear system
resulting from application of the BE method for the
monodomain equations is solved for the first time by a
nonlinear elimination method, which eliminates local and
nonsymmetric components by using a Jacobian-free Newton
solver, called Newton-Krylov solver. Unlike other fully
implicit methods proposed for the monodomain equations In
the literature, the Jacobian of the global system after the
nonlinear elimination has much smaller size, is symmetric
and possibly positive definite, which can be solved
efficiently by standard optimal solvers. Numerical results
are presented demonstrating that the C-BDF2 scheme can yield
accurate results with less CPU times than explicit methods
for both a single patch and spatially extended
domains.},
Key = {Ying08}
}
@booklet{Roberts08,
Author = {S. F. Roberts and J. G. Stinstra and C. S.
Henriquez},
Title = {Effect of nonuniform interstitial space properties on
impulse propagation: A discrete multidomain
model},
Journal = {Biophysical Journal},
Volume = {95},
Number = {8},
Pages = {3724 -- 3737},
Year = {2008},
Month = {October},
ISSN = {0006-3495},
Abstract = {This work presents a discrete multidomain model that
describes ionic diffusion pathways between connected cells
and within the interstitium. Unlike classical models of
impulse propagation, the intracellular and extracellular
spaces are represented as spatially distinct volumes with
dynamic/static boundary conditions that electrically couple
neighboring spaces. The model is used to investigate the
impact of nonuniform geometrical and electrical properties
of the interstitial space surrounding a fiber on conduction
velocity and action potential waveshape. Comparison of the
multidomain and bidomain models shows that although the
conduction velocity is relatively insensitive to cases that
con. ne 50\% of the membrane surface by narrow extracellular
depths ($>$= 2 nm), the action potential morphology varies
greatly around the fiber perimeter, resulting in changes in
the magnitude of extracellular potential in the tight
spaces. Results also show that when the conductivity of the
tight spaces is sufficiently reduced, the membrane adjacent
to the tight space is eliminated from participating in
propagation, and the conduction velocity increases. Owing to
its ability to describe the spatial discontinuity of cardiac
microstructure, the discrete multidomain can be used to
determine appropriate tissue properties for use in classical
macroscopic models such as the bidomain during normal and
pathophysiological conditions.},
Key = {Roberts08}
}
@booklet{Jacquemet08,
Author = {V. Jacquemet and C. S. Henriquez},
Title = {Loading effect of fibroblast-myocyte coupling on resting
potential, impulse propagation, and repolarization: insights
from a microstructure model},
Journal = {American Journal Of Physiology-heart And Circulatory
Physiology},
Volume = {294},
Number = {5},
Pages = {H2040 -- H2052},
Year = {2008},
Month = {May},
ISSN = {0363-6135},
Abstract = {The numerous nonmyocytes present within the myocardium may
establish electrical connections with myocytes through gap
junctions, formed naturally or as a result of a cell
therapy. The strength of the coupling and its potential
impact on action potential characteristics and conduction
are not well understood. This study used computer simulation
to investigate the load-induced electrophysiological
consequences of the coupling of myocytes with fibroblasts,
where the fibroblast resting potential, density,
distribution, and coupling strength were varied. Conduction
velocity (CV), upstroke velocity, and action potential
duration (APD) were analyzed for longitudinal and transverse
impulse propagation in a two-dimensional microstructure
tissue model, developed to represent a monolayer culture of
cardiac cells covered by a layer of fibroblasts. The results
show that 1) at weak coupling ($<$0.25 nS), the myocyte
resting potential was elevated, leading to CV up to 5\%
faster than control; 2) at intermediate coupling, the
myocyte resting potential elevation saturated, whereas the
current flowing from the myocyte to the fibroblast
progressively slowed down both CV and upstroke velocity; 3)
at strong couplings ($>$ 8 nS), all of the effects
saturated; and 4) APD at 90\% repolarization was usually
prolonged by 0-20 ms (up to 60-80 ms for high fibroblast
density and coupling) by the coupling to fibroblasts. The
changes in APD depended on the fibroblast resting potential.
This complex, coupling-dependent interaction of fibroblast
and myocytes also has relevance to the integration of other
nonmyocytes in the heart, such as those used in cellular
therapies.},
Key = {Jacquemet08}
}
@article{3781053,
Author = {Henriquez, C.S. and Plonsey, R.},
Title = {Simulation of propagation along a cylindrical bundle of
cardiac tissue. II. Results of simulation},
Journal = {IEEE Trans. Biomed. Eng. (USA)},
Volume = {37},
Number = {9},
Pages = {861 - 75},
url = {http://dx.doi.org/10.1109/10.58597},
Keywords = {bioelectric phenomena;cardiology;muscle;physiological
models;},
Abstract = {For pt.I see ibid., vol.37, no.9, p.850-60 (1990). Nonlinear
membrane kinetics are introduced into the bidomain membrane
and equal anisotropy ratios are assumed, permitting the
transmembrane potential to be computed and its behavior
examined at different depths in the bundle and for different
values of conductivity and bundle diameters. In contrast
with single-fiber models, the bundle model reveals that the
shape of the action potential is influenced by tissue
resistivities. In addition, the steady-state activation
wavefront through the cross section perpendicular to the
long axis of the bundle is not planar and propagates with a
velocity that lies between that of a single fiber in an
unbounded volume and a single-fiber in a restricted
extracellular space. In general, the bundle model is shown
to be significantly better than the classical single fiber
model in describing the behavior of real cardiac
tissue},
Key = {3781053}
}
@article{7402025,
Author = {Virag, N. and Jacquemet, V. and Henriquez, C.S. and Zozor,
S. and Blanc, O. and Vesin, J.-M. and Pruvot, E. and Kappenberger, L.},
Title = {Study of atrial arrhythmias in a computer model based on
magnetic resonance images of human atria},
Journal = {Chaos (USA)},
Volume = {12},
Number = {3},
Pages = {754 - 63},
url = {http://dx.doi.org/10.1063/1.1483935},
Keywords = {biomedical MRI;chaos;electrocardiography;physiological
models;wavelet transforms;},
Abstract = {The maintenance of multiple wavelets appears to be a
consistent feature of atrial fibrillation (AF). In this
paper, we investigate possible mechanisms of initiation and
perpetuation of multiple wavelets in a computer model of AF.
We developed a simplified model of human atria that uses an
ionic-based membrane model and whose geometry is derived
from a segmented magnetic resonance imaging data set. The
three-dimensional surface has a realistic size and includes
obstacles corresponding to the location of major vessels and
valves, but it does not take into account anisotropy. The
main advantage of this approach is its ability to simulate
long duration arrhythmias (up to 40 s). Clinically relevant
initiation protocols, such as single-site burst pacing, were
used. The dynamics of simulated AF were investigated in
models with different action potential durations and
restitution properties, controlled by the conductance of the
slow inward current in a modified Luo-Rudy model. The
simulation studies show that (1) single-site burst pacing
protocol can be used to induce wave breaks even in tissue
with uniform membrane properties, (2) the restitution-based
wave breaks in an atrial model with realistic size and
conduction velocities are transient, and (3) a significant
reduction in action potential duration (even with apparently
flat restitution) increases the duration of
AF},
Key = {7402025}
}
@article{3781052,
Author = {Henriquez, C.S. and Plonsey, R.},
Title = {Simulation of propagation along a cylindrical bundle of
cardiac tissue. I. Mathematical formulation},
Journal = {IEEE Trans. Biomed. Eng. (USA)},
Volume = {37},
Number = {9},
Pages = {850 - 60},
url = {http://dx.doi.org/10.1109/10.58596},
Keywords = {bioelectric phenomena;cardiology;muscle;physiological
models;},
Abstract = {A mathematical description, based on a three-dimensional
model for studying propagation in cardiac muscle is given.
The model makes use of the bidomain concept to construct a
representation of a cylindrical, multicellular bundle lying
in an extensive volume conductor. The equations for the
cylindrical bidomain are derived for different combinations
of boundary conditions and simplifying assumptions. The
analysis shows that an analytic model for propagation can be
set up if one assumes that the ratio of the intracellular
and interstitial bidomain conductivities in the radial and
axial direction are the same (i.e. equal anisotropy) and the
intracellular radial current density vanishes at the
surface. As a point of reference, the classical
one-dimensional cable model is also examined and the
expressions governing propagation are reformulated to
account for the extracellular medium, a factor ignored in
most simulation studies},
Key = {3781052}
}
@article{7741012,
Author = {Cherry, E.M. and Greenside, H.S. and Henriquez,
C.S.},
Title = {Efficient simulation of three-dimensional anisotropic
cardiac tissue using an adaptive mesh refinement
method},
Journal = {Chaos (USA)},
Volume = {13},
Number = {3},
Pages = {853 - 65},
url = {http://dx.doi.org/10.1063/1.1594685},
Keywords = {adaptive estimation;biomembrane transport;electrocardiography;},
Abstract = {A recently developed space-time adaptive mesh refinement
algorithm (AMRA) for simulating isotropic one- and
two-dimensional excitable media is generalized to simulate
three-dimensional anisotropic media. The accuracy and
efficiency of the algorithm is investigated for anisotropic
and inhomogeneous 2D and 3D domains using the Luo-Rudy 1
(LR1) and FitzHugh-Nagumo models. For a propagating wave in
a 3D slab of tissue with LR1 membrane kinetics and
rotational anisotropy comparable to that found in the human
heart, factors of 50 and 30 are found, respectively, for the
speedup and for the savings in memory compared to an
algorithm using a uniform space-time mesh at the finest
resolution of the AMRA method. For anisotropic 2D and 3D
media, we find no reduction in accuracy compared to a
uniform space-time mesh. These results suggest that the AMRA
will be able to simulate the 3D electrical dynamics of
canine ventricles quantitatively for 1 s using 32 1-GHz
Alpha processors in approximately 9 h},
Key = {7741012}
}
@article{7402040,
Author = {Sampson, K.J. and Henriquez, C.S.},
Title = {Interplay of ionic and structural heterogeneity on
functional action potential duration gradients: Implications
for arrhythmogenesis},
Journal = {Chaos (USA)},
Volume = {12},
Number = {3},
Pages = {819 - 28},
url = {http://dx.doi.org/10.1063/1.1497735},
Keywords = {chaos;electrocardiography;},
Abstract = {Action potential duration (APD) dispersion in the heart is
governed by the underlying cellular architecture and the
spatial distribution of the membrane properties.
Understanding the contribution of each factor is important
in designing more effective methods for the control of
arrhythmias. Recent experimental studies have shown that the
insertion of structural barriers in ionically heterogeneous
tissue facilitates the formation of unidirectional block and
discordant alternans. In this work, computational modeling
is used to examine the effect of internal obstacles on the
formation of functional APD gradients in ionically
heterogeneous tissue. Intrinsic APD differences are
introduced by assigning two discrete cell types to each half
of a square domain. The combined effect of structural and
ionic heterogeneities is shown to produce gradients in APD
that are oblique to both the intrinsic gradients in APD and
the physical boundary. Simulation results are presented that
show that the magnitude and spatial extent of the subsequent
APD gradients are modulated by the size and orientation of
the obstacle, the degree of anisotropy, and the location of
the pacing site. Long, thin internal obstacles are found to
produce the greatest dispersion in APD. The combination of
internal obstacles and ionic heterogeneities is shown to
produce a substrate for re-entrant excitation following a
pair of near threshold point stimuli},
Key = {7402040}
}
@article{3291272,
Author = {Miller, C.E. and Henriquez, C.S.},
Title = {Three-dimensional finite element solution for biopotentials:
erythrocyte in an applied field},
Journal = {IEEE Trans. Biomed. Eng. (USA)},
Volume = {35},
Number = {9},
Pages = {712 - 18},
url = {http://dx.doi.org/10.1109/10.7272},
Keywords = {blood;cellular biophysics;finite element
analysis;},
Abstract = {The use of the finite-element method in the analysis of
bioelectric phenomena is demonstrated. The problem studied
is three-dimensional steady current flow around an
erythrocyte in an extracellular medium. The finite-element
equations for the electrical field problem are derived and
mesh generation and the use of a heat-conduction code for
analysis are described. Spherical cell geometry, allowing an
analytical solution, is also modeled to guide in mesh
creation and error estimation for the case of erythrocyte
geometry. The results are shown as contour plots of
potential on the erythrocyte surface. The maximum
transmembrane potential calculated for the erythrocyte is
22% lower than that of the sphere, a significant finding
since spherical geometry is often used in studies involving
the effect of applied electrical fields on
cells},
Key = {3291272}
}
%% Idriss, Salim F
@article{fds160464,
Author = {AN Doshi and SF Idriss},
Title = {Relationship between extracellular T-wave height, T-wave
alternans amplitude, and tissue action potential alternans:
a 1-dimensional computer modeling study.},
Journal = {Journal of electrocardiology},
Year = {2009},
Month = {July},
ISSN = {1532-8430},
Abstract = {T-wave alternans (TWA) is a useful marker of cardiac
instability, but not much is known about the factors that
affect its measurement, such as electrode placement. We used
a 1-dimensional myocardial fiber computer model of alternans
to investigate the effect of electrode position on TWA
measurement. Results demonstrated that TWA amplitude and
T-wave amplitude change proportionally if both recording
electrodes are symmetrically moved toward or away from the
tissue. However, TWA amplitude and T-wave amplitude change
out of proportion to one another when one electrode is moved
while the other electrode remains stationary. These
disproportionate changes result from beatwise alternation in
the asymmetric potential field around the tissue. In
summary, nonlinear changes in tissue repolarization during
alternans result in nonlinear changes in T-wave amplitude
and TWA amplitude.},
Key = {fds160464}
}
@article{fds160463,
Author = {N Hakacova and AM Robinson and C Maynard and GS Wagner and SF
Idriss},
Title = {Determination of the mitral papillary muscle positions by
the septal-to-free wall arc ratio method.},
Journal = {Clinical physiology and functional imaging,
England},
Volume = {29},
Number = {3},
Pages = {181-6},
Year = {2009},
Month = {May},
ISSN = {1475-097X},
Keywords = {Adult Heart Ventricles Humans Image Interpretation,
Computer-Assisted* Magnetic Resonance Imaging* Middle Aged
Mitral Valve Observer Variation Papillary Muscles Predictive
Value of Tests Reproducibility of Results Ventricular Septum
anatomy & histology anatomy & histology*
ultrasonography},
Abstract = {BACKGROUND: Determination of mitral papillary muscle
positions is of increasing interest in wide spectrum of
clinical cardiology fields. Particularly, relative
positioning of the papillary muscles between the
inter-ventricular septum and the left ventricular free wall
is of interest. A reproducible method for determination of
papillary muscle positions has not been established. In this
study a new 'septal-to-free wall arc ratio' (SFAR) method
for measuring papillary muscle positions is presented. The
reproducibility of the SFAR method between echocardiographic
(ECHO) and magnetic resonance (MRI) modalities and between
observers is tested. METHODS: Twenty subjects with
structurally normal hearts in whom both MRI and ECHO were
performed in 2007 were included in the study. Papillary
muscle positions were determined using the SFAR method.
Inter-modality (ECHO and MRI) and inter-observer
reproducibility of the methods was assessed by calculating
correlation coefficients and the mean difference from
agreement. RESULTS: The inter-modality correlation of the
SFAR method was 0.80 (P < 0.0001) for both papillary
muscles. The mean difference of measurements from agreement
was 4% for the superior and 2% for the inferior papillary
muscle. The inter-observer correlation was 0.93 (P < 0.0001)
for superior and 0.90 (P = 0.0002) for inferior papillary
muscle. The mean inter-observer difference from agreement
was 2% for superior and 3% for inferior papillary muscle.
CONCLUSIONS: The SFAR method may be applied in wide range of
both scientific and clinical medical fields as a
reproducible method for determination of papillary muscle
positions with the benefit of estimation of relative
papillary muscle positions both from the septum and the free
wall.},
Key = {fds160463}
}
@article{fds160465,
Author = {C Ratnasamy and SF Idriss and MP Carboni and RJ Kanter},
Title = {Arrhythmias in children having a single left superior vena
cava and minimal structural heart disease.},
Journal = {Journal of cardiovascular electrophysiology, United
States},
Volume = {20},
Number = {2},
Pages = {182-6},
Year = {2009},
Month = {February},
ISSN = {1540-8167},
Keywords = {Adolescent Arrhythmias, Cardiac Atrial Fibrillation
Atrioventricular Block Child Child, Preschool
Echocardiography Exercise Tolerance Fatigue Female Heart
Defects, Congenital Humans Infant Infant, Newborn Male
Sinoatrial Block Syncope Tachycardia, Supraventricular Vena
Cava, Superior Wolff-Parkinson-White Syndrome abnormalities*
complications etiology etiology* physiology physiopathology
ultrasonography},
Abstract = {BACKGROUND: The presence of a single left superior vena cava
in the absence of complex congenital heart disease is
uncommon, and, in the absence of hemodynamic consequences,
it would not be expected to result in cardiovascular signs
or symptoms. Single case reports and our anecdotal
experience suggested to us that this anomaly is highly
associated with cardiac arrhythmias. OBJECTIVE: We sought to
describe the clinically important arrhythmias in a
population of young patients having this anomaly. METHODS: A
retrospective chart review was performed from all patients
<20 years old and who were determined by echocardiography
over an 11-year-period to have a single left superior vena
cava and minor or no coexisting congenital heart defects.
The prevalence of nonsinus pacemaker, age-corrected sinus
rate percentile, and prevalence of brady- or
tachyarrhythmias was compared with a control group of
patients having bilateral superior vena cavae. RESULTS:
Eight patients having a single left and 55 patients having
bilateral superior vena cava(e) were identified. The
existence of this anomaly tended to be associated with a
lower age-corrected sinus rate percentile (17.5% vs 75%, P =
0.09), and was associated with a higher prevalence of
arrhythmias (50% vs 7%, P = 0.014) compared with the control
group. In the study group, one patient each had clinically
relevant sinus node dysfunction, third-degree AV block,
Wolff-Parkinson-White syndrome and atrial fibrillation, and
AV nodal reentrant tachycardia. CONCLUSION: Even in the
absence of symptoms, patients found to have a single left
superior vena cava should be monitored long-term for
clinically important arrhythmias.},
Key = {fds160465}
}
@article{fds160467,
Author = {SF Idriss and JA Bell},
Title = {Cardiac repolarization instability during normal postnatal
development.},
Journal = {Journal of electrocardiology, United States},
Volume = {41},
Number = {6},
Pages = {474-9},
ISSN = {1532-8430},
Keywords = {Aging* Animals Arrhythmias, Cardiac Heart Conduction System
Rabbits diagnosis* physiopathology*},
Abstract = {Long QT syndrome is a disease characterized by abnormal
lengthening of the QT interval and by sudden cardiac death.
It is a disease of development, with the incidence of a
sudden event increasing during childhood. Repolarization
instability during postnatal development could make the
substrate susceptible to a fatal arrhythmia. Dynamic changes
in repolarization that occur on a beat-to-beat basis, known
as alternans, are a hallmark of electrical instability.
T-wave alternans (TWA) in the electrocardiogram correlates
with arrhythmia risk and long-term survival in adults. We
determined TWA properties longitudinally in vivo in 7
propofol-sedated New Zealand white rabbits using
transesophageal pacing weekly from 2 to 10 weeks of age.
Furthermore, TWA induction after the onset of rapid pacing
was characterized in vitro in 6 infant (2 weeks) and 6
adolescent (7 weeks) isolated, arterially perfused rabbit
hearts. In vivo, TWA amplitude was maximum at 2 weeks and
declined with age. Isoproterenol increased TWA at 8 weeks
(adolescence). In vitro, large-amplitude TWA was induced
with rapid pacing in both infant and adolescents but
decreased to low, steady-state levels in infants. We
conclude that TWA properties are age dependent in rabbit.
Significant TWA is induced in rabbit at the onset of rapid
pacing.},
Key = {fds160467}
}
@article{8010731,
Author = {Lee, W. and Idriss, S.F. and Wolf, P.D. and Smith,
S.W.},
Title = {Dual lumen transducer probes for real-time 3-D
interventional cardiac ultrasound},
Journal = {Ultrasound Med. Biol. (USA)},
Volume = {29},
Number = {9},
Pages = {1297 - 304},
url = {http://dx.doi.org/10.1016/S0301-5629(03)00952-9},
Keywords = {biological tissues;biomedical transducers;echocardiography;medical
image processing;surgery;ultrasonic imaging;ultrasonic
transducer arrays;},
Abstract = {We have developed dual lumen probes incorporating a
forward-viewing matrix array transducer with an integrated
working lumen for delivery of tools in real-time 3-D (RT3-D)
interventional echocardiography. The probes are of 14 Fr and
22 Fr sizes, with 112 channel 2-D arrays operating at 5 MHz.
We obtained images of cardiac anatomy and simultaneous
interventional device delivery with an in vivo sheep model,
including: manipulation of a 0.36-mm diameter guidewire into
the coronary sinus, guidance of a transseptal puncture using
a 1,2-mm diameter Brockenbrough needle, and guidance of a
right ventricular biopsy using 3 Fr biopsy forceps. We have
also incorporated the 22 Fr probe within a 6-mm surgical
trocar to obtain apical four-chamber ultrasound (US) scans
from a subcostal position. Combining the imaging catheter
with a working lumen in a single device may simplify cardiac
interventional procedures by allowing clinicians to easily
visualize cardiac structures and simultaneously direct
interventional tools in a RT3-D image},
Key = {8010731}
}
%% Izatt, Joseph A
@booklet{Davis09,
Author = {A. Davis and J. Izatt and F. Rothenerg},
Title = {Quantitative Measurement of Blood Flow Dynamics in Embryonic
Vasculature Using Spectral Doppler Velocimetry},
Journal = {Anatomical Record-advances In Integrative Anatomy And
Evolutionary Biology},
Volume = {292},
Number = {3},
Pages = {311 -- 319},
Year = {2009},
Month = {March},
ISSN = {1932-8486},
Abstract = {The biophysical effects of blood flow are known to influence
the structure and function of adult cardiovascular systems.
Similar effects on the maturation of the cardiovascular
system have been difficult to directly and non-invasively
measure due to the small size of the embryo. Optical
coherence tomography (OCT) has been shown to provide high
spatial and temporal structural imaging of the early
embryonic chicken heart. We have developed an extension of
Doppler OCT, called spectral Doppler velocimetry (SDV), that
will enable direct, non-invasive quantification of blood
flow and shear rate from the early embryonic cardiovascular
system. Using this technique, we calculated volumetric flow
rate and shear rate from chicken embryo vitelline vessels.
We present blood flow dynamics and spatial velocity profiles
from three different vessels in the embryo as well as
measurements from the outflow tract of the embryonic heart
tube. This technology can potentially provide spatial
mapping of blood flow and shear rate in embryonic
cardiovascular structures, producing quantitative
measurements that can be correlated with gene expression and
normal and abnormal morphology. Anat Rec, 292:311-319, 2009.
(C) 2009 Wiley-Liss, Inc.},
Key = {Davis09}
}
@booklet{Asrani08,
Author = {S. Asrani and M. Sarunic and C. Santiago and J.
Izatt},
Title = {Detailed visualization of the anterior segment using
Fourier-domain optical coherence tomography},
Journal = {Archives Of Ophthalmology},
Volume = {126},
Number = {6},
Pages = {765 -- 771},
Year = {2008},
Month = {June},
ISSN = {0003-9950},
Abstract = {Objective: To study details of the anterior chamber drainage
angle using Fourier-domain optical coherence tomography in
healthy subjects and patients with angle abnormalities.
Methods: A high-speed anterior segment optical coherence
tomography prototype was developed using a
1310-nm-wavelength swept light source. Six healthy subjects
and 6 patients with glaucoma were imaged in an observational
cross-sectional study. Results: Schlemm's canal and the
trabecular meshwork were visualized in all of the patients.
Fifteen-millimeter scans enabled entire anterior segment
visualization providing configuration details of the iris
with respect to the angle. Four-millimeter scans permitted
detailed views of the angle configuration and its
structures. Volumetric imaging was possible and Schlemm's
canal was visualized along part of its circumference.
Conclusion: Anterior segment Fourier-domain optical
coherence tomography permits detailed noncontact imaging of
the angle and its structures, providing a tool to improve
our understanding of the pathogenesis of narrow-angle
glaucoma.},
Key = {Asrani08}
}
@article{5728487,
Author = {Izatt, J.A. and Kulkami, M.D. and Yazdanfar, S. and Barton,
J.K. and Welch, A.J.},
Title = {In vivo bidirectional color Doppler flow imaging of
picoliter blood volumes using optical coherence
tomography},
Journal = {Opt. Lett. (USA)},
Volume = {22},
Number = {18},
Pages = {1439 - 41},
Year = {15},
Keywords = {biomedical imaging;blood flow measurement;Doppler
measurement;light coherence;light interferometry;optical
tomography;},
Abstract = {The authors describe a novel optical system for
bidirectional color Doppler imaging of flow in biological
tissues with micrometer-scale resolution and demonstrate its
use for in vivo imaging of blood flow in an animal model.
The authors' technique, color Doppler optical coherence
tomography (CDOCT), performs spatially localized optical
Doppler velocimetry by use of scanning low-coherence
interferometry. CDOCT is an extension of optical coherence
tomography (OCT), employing coherent signal-acquisition
electronics and joint time-frequency analysis algorithms to
perform flow imaging simultaneous with conventional OCT
imaging. Cross-sectional maps of blood flow velocity with
<50-μm spatial resolution and <0.6-mm/s velocity
precision were obtained through intact skin in living
hamster subdermal tissue. This technology has several
potential medical applications},
Key = {5728487}
}
@article{6049791,
Author = {Barton, J.K. and Welch, A.J. and Izatt, J.A.},
Title = {Investigating pulsed dye laser-blood vessel interaction with
color Doppler optical coherence tomography},
Journal = {Opt. Express (USA)},
Volume = {3},
Number = {6},
Year = {14},
Keywords = {backscatter;biological effects of laser radiation;biological
techniques;blood;Doppler measurement;dye lasers;light
coherence;optical tomography;reflectivity;skin;},
Abstract = {A noninvasive method of imaging laser irradiated blood
vessels has been achieved using Color Doppler Optical
Coherence Tomography (CDOCT). This method may increase
understanding of the mechanisms behind treatment of vascular
disorders. The CDOCT system used a 1280 nm center wavelength
superluminescent diode. A 585 nm, 360 μs pulsed dye laser
was used to irradiate hamster dorsal skin flap window
preparations. Irradiation sites were imaged with CDOCT prior
to, immediately after, and 24 hours after laser irradiation.
The processed CDOCT signal provided an estimate of the blood
flow velocity. An increase in the blood vessel backscattered
signal was observed as blood or vessel walls were
coagulated. A decrease in damaged blood vessel reflectivity
occurred after twenty four hours},
Key = {6049791}
}
@article{6049788,
Author = {Rollins, A.M. and Kulkarni, M.D. and Yazdanfar, S. and Ung-arunyawee, R. and Izatt, J.A.},
Title = {In vivo video rate optical coherence tomography},
Journal = {Opt. Express (USA)},
Volume = {3},
Number = {6},
Year = {14},
Keywords = {biological techniques;biomedical imaging;eye;Fourier
transform optics;light coherence;light interferometry;optical
tomography;skin;},
Abstract = {An optical coherence tomography system is described which
can image up to video rate. The system utilizes a high power
broadband source and real time image acquisition hardware
and features a high speed scanning delay line in the
reference arm based on Fourier-transform pulse shaping
technology. The theory of low coherence interferometry with
a dispersive delay line, and the operation of the delay line
are detailed and the design equations of the system are
presented. Real time imaging is demonstrated in vivo in
tissues relevant to early human disease diagnosis (skin,
eye) and in an important model in developmental biology
(Xenopus laevis)},
Key = {6049788}
}
@article{7909781,
Author = {Choma, M.A. and Sarunic, M.V. and Changhuei Yang and Izatt,
J.A.},
Title = {Sensitivity advantage of swept source and Fourier domain
optical coherence tomography},
Journal = {Opt. Express (USA)},
Volume = {11},
Number = {18},
Year = {8},
Keywords = {biomedical optical imaging;Fourier transform optics;optical
fibre theory;optical noise;optical tomography;photodiodes;sensitivity;superluminescent
diodes;},
Abstract = {We present theoretical and experimental results which
demonstrate the superior sensitivity of swept source (SS)
and Fourier domain (FD) optical coherence tomography (OCT)
techniques over the conventional time domain (TD) approach.
We show that SS- and FD-OCT have equivalent expressions for
system signal-to-noise ratio which result in a typical
sensitivity advantage of 20 to 30 dB over TD-OCT.
Experimental verification is provided using two novel
spectral discrimination (SD) OCT systems: a differential
fiber-based 800 nm FD-OCT system which employs deep-well
photodiode arrays, and a differential 1300 nm SS-OCT system
based on a swept laser with an 87 nm tuning
range},
Key = {7909781}
}
@article{8379200,
Author = {Changhuei Yang and McGuckin, L.E.L. and Simon, J.D. and Choma, M.A. and Applegate, B.E. and Izatt,
J.A.},
Title = {Spectral triangulation molecular contrast optical coherence
tomography with indocyanine green as the contrast
agent},
Journal = {Opt. Lett. (USA)},
Volume = {29},
Number = {17},
Pages = {2016 - 18},
Year = {1},
url = {http://dx.doi.org/10.1364/OL.29.002016},
Keywords = {bio-optics;biomedical optical imaging;dyes;light
scattering;molecular biophysics;optical tomography;},
Abstract = {We report a new molecular contrast optical coherence
tomography (MCOCT) implementation that profiles the contrast
agent distribution in a sample by measuring the agent's
spectral differential absorption. The method, spectra
triangulation MCOCT, can effectively suppress contributions
from spectrally dependent scatterings from the sample
without a priori knowledge of the scattering properties. We
demonstrate molecular imaging with this new MCOCT modality
by mapping the distribution of indocyanine green, a
FDA-approved infrared red dye, within a stage 54 Xenopus
laeuis},
Key = {8379200}
}
%% Jacquemet, Vincent
@article{7402025,
Author = {Virag, N. and Jacquemet, V. and Henriquez, C.S. and Zozor,
S. and Blanc, O. and Vesin, J.-M. and Pruvot, E. and Kappenberger, L.},
Title = {Study of atrial arrhythmias in a computer model based on
magnetic resonance images of human atria},
Journal = {Chaos (USA)},
Volume = {12},
Number = {3},
Pages = {754 - 63},
url = {http://dx.doi.org/10.1063/1.1483935},
Keywords = {biomedical MRI;chaos;electrocardiography;physiological
models;wavelet transforms;},
Abstract = {The maintenance of multiple wavelets appears to be a
consistent feature of atrial fibrillation (AF). In this
paper, we investigate possible mechanisms of initiation and
perpetuation of multiple wavelets in a computer model of AF.
We developed a simplified model of human atria that uses an
ionic-based membrane model and whose geometry is derived
from a segmented magnetic resonance imaging data set. The
three-dimensional surface has a realistic size and includes
obstacles corresponding to the location of major vessels and
valves, but it does not take into account anisotropy. The
main advantage of this approach is its ability to simulate
long duration arrhythmias (up to 40 s). Clinically relevant
initiation protocols, such as single-site burst pacing, were
used. The dynamics of simulated AF were investigated in
models with different action potential durations and
restitution properties, controlled by the conductance of the
slow inward current in a modified Luo-Rudy model. The
simulation studies show that (1) single-site burst pacing
protocol can be used to induce wave breaks even in tissue
with uniform membrane properties, (2) the restitution-based
wave breaks in an atrial model with realistic size and
conduction velocities are transient, and (3) a significant
reduction in action potential duration (even with apparently
flat restitution) increases the duration of
AF},
Key = {7402025}
}
%% Jaszczak, Ronald J
@article{fds164010,
Author = {R Ter-Antonyan and RJ Jaszczak and KL Greer and JE Bowsher and SD
Metzler, RE Coleman},
Title = {Combination of Converging Collimators for High-Sensitivity
Brain SPECT.},
Journal = {Journal of nuclear medicine : official publication, Society
of Nuclear Medicine},
Year = {2009},
Month = {August},
ISSN = {0161-5505},
Abstract = {The objective of this study, which is related to human brain
SPECT, was to increase the sensitivity of a triple-camera
SPECT system and reduce statistical noise in reconstructed
images using a combination of converging collimators. The
reason for combining collimators is to ensure both high
sensitivity and sufficient sampling without trading off
spatial resolution. METHODS: A high-sensitivity
half-cone-beam (HCB) collimator, designed specifically for
brain imaging, was combined with other collimators and
compared with conventional parallel-beam and fanbeam
circular orbit acquisitions. For comparison, previously
studied HCB collimation with a circle-and-helix data
acquisition trajectory was also included in this study.
Simulations of the Hoffman 3-dimensional brain phantom were
performed to calculate the efficiencies of collimators and
their combinations and to quantitatively evaluate
reconstruction bias, statistical noise, and signal-to-noise
ratios in the reconstructed images. Experimental brain
phantom data were also acquired and compared for different
acquisition types. Finally, a patient brain scan was
obtained with a combination of HCB and fanbeam collimators
and compared with a triple-fanbeam circular orbit
acquisition. RESULTS: A combination of 2 HCB collimators and
1 fanbeam collimator, compared with a triple-fanbeam
collimator, can increase the photon detection efficiency by
27% and by more than a factor of 2, compared with
triple-parallel-hole collimation, with equal spatial
resolution measured on the axis of rotation. Quantitative
analysis of reconstruction bias and visual analysis of the
images showed no signs of sampling artifacts. Reconstructed
images in the simulations, experimental brain phantom, and
patient brain scans showed improved quality with this
collimator combination due to increased sensitivity and
reduced noise. Lesion visibility was also improved, as
confirmed by signal-to-noise ratios. Alternatively,
triple-HCB circle-and-helix acquisition has also shown
competitive results, with a slight disadvantage in axial
sampling and implementation procedure. CONCLUSION: Combined
HCB and fanbeam collimation is a promising approach for
high-sensitivity brain SPECT.},
Key = {fds164010}
}
@article{fds164022,
Author = {J Zhang and J Ma and S Zhou and JL Hubbs and TZ Wong and RJ Folz and ES Evans and RJ Jaszczak and R Clough and LB Marks},
Title = {Radiation-Induced Reductions in Regional Lung Perfusion:
0.1-12 Year Data from a Prospective Clinical
Study.},
Journal = {International journal of radiation oncology, biology,
physics},
Year = {2009},
Month = {July},
ISSN = {1879-355X},
Abstract = {PURPOSE: To assess the time and regional dependence of
radiation therapy (RT)-induced reductions in regional lung
perfusion 0.1-12 years post-RT, as measured by single photon
emission computed tomography (SPECT) lung perfusion.
MATERIALS/METHODS: Between 1991 and 2005, 123 evaluable
patients receiving RT for tumors in/around the thorax
underwent SPECT lung perfusion scans before and serially
post-RT (0.1-12 years). Registration of pre- and post-RT
SPECT images with the treatment planning computed
tomography, and hence the three-dimensional RT dose
distribution, allowed changes in regional SPECT-defined
perfusion to be related to regional RT dose. Post-RT
follow-up scans were evaluated at multiple time points to
determine the time course of RT-induced regional perfusion
changes. Population dose response curves (DRC) for all
patients at different time points, different regions, and
subvolumes (e.g., whole lungs, cranial/caudal,
ipsilateral/contralateral) were generated by combining data
from multiple patients at similar follow-up times. Each DRC
was fit to a linear model, and differences statistically
analyzed. RESULTS: In the overall groups, dose-dependent
reductions in perfusion were seen at each time post-RT. The
slope of the DRC increased over time up to 18 months
post-RT, and plateaued thereafter. Regional differences in
DRCs were only observed between the ipsilateral and
contralateral lungs, and appeared due to tumor-associated
changes in regional perfusion. CONCLUSIONS: Thoracic RT
causes dose-dependent reductions in regional lung perfusion
that progress up to approximately 18 months post-RT and
persists thereafter. Tumor shrinkage appears to confound the
observed dose-response relations. There appears to be
similar dose response for healthy parts of the lungs at
different locations.},
Key = {fds164022}
}
@article{fds164016,
Author = {SD Metzler and S Vemulapalli and RJ Jaszczak and G Akabani and BB
Chin},
Title = {Feasibility of Whole-Body Functional Mouse Imaging Using
Helical Pinhole SPECT.},
Journal = {Molecular imaging and biology : MIB : the official
publication of the Academy of Molecular Imaging},
Year = {2009},
Month = {June},
ISSN = {1860-2002},
Abstract = {PURPOSE: Detailed in vivo whole-body biodistributions of
radiolabeled tracers may characterize the longitudinal
progression of disease, and changes with therapeutic
interventions. Small-animal imaging in mice is particularly
attractive due to the wide array of well characterized
genetically and surgically created models of disease. Single
Photon Emission Computed Tomography (SPECT) imaging using
pinhole collimation provides high resolution and
sensitivity, but conventional methods using circular
acquisitions result in severe image truncation and
incomplete sampling of data, which prevent the accurate
determination of whole-body radiotracer biodistributions.
This study describes the feasibility of helical acquisition
paths to mitigate these effects. PROCEDURES: Helical paths
of pinhole apertures were implemented using an external
robotic stage aligned with the axis of rotation (AOR) of the
scanner. Phantom and mouse scans were performed using
helical paths and either circular or bi-circular orbits at
the same radius of rotation (ROR). The bi-circular orbits
consisted of two 360-degree scans separated by an axial
shift to increase the axial field of view (FOV) and to
improve the complete-sampling properties. RESULTS:
Reconstructions of phantoms and mice acquired with helical
paths show good image quality and are visually free of both
truncation and axial-blurring artifacts. Circular orbits
yielded reconstructions with both artifacts and a limited
effective FOV. The bi-circular scans enlarged the axial FOV,
but still suffered from truncation and sampling artifacts.
CONCLUSIONS: Helical paths can provide complete sampling
data and large effective FOV, yielding 3D full-body in vivo
biodistributions while still maintaining a small distance
from the aperture to the object for good sensitivity and
resolution.},
Key = {fds164016}
}
@article{fds164019,
Author = {R Ter-Antonyan and RJ Jaszczak and JE Bowsher and KL Greer and SD
Metzler},
Title = {Quantitative Evaluation of Half-Cone-Beam Scan Paths in
Triple-Camera Brain SPECT.},
Journal = {IEEE transactions on nuclear science},
Volume = {55},
Number = {5},
Pages = {2518-2526},
Year = {2008},
Month = {October},
ISSN = {0018-9499},
Abstract = {In this study related to human brain SPECT imaging,
simulation of half-cone-beam (HCB) collimation with
different scan paths is performed and compared with
simulated fan-beam and parallel-hole circular orbit
acquisitions of disk-phantom projection data. Acquisition
types are quantitatively evaluated based on the photon
detection efficiency, the root-mean-squared error, contrast
and signal-to-noise ratio measurements of the reconstructed
images. We demonstrate that a triple-camera SPECT system
with half-cone-beam collimators and circle-and-helix scan
paths can offer up to a 26% efficiency increase over
fan-beam, and up to a 128% increase over parallel-hole
collimators for equal spatial resolutions, and display no
visible axial sampling artifacts in reconstructed
disk-phantom images. In addition, we perform qualitative
experimental evaluation of triple-HCB circle-and-helix
acquisition using a Hoffman 3D brain phantom. Reconstructed
brain phantom images show improved quality due to reduced
noise and no apparent sampling artifacts. Triple-HCB
circle-and-helix SPECT has a potential for improved brain
imaging, producing higher image quality with a smaller
reconstruction error and better lesion detectability due to
increased efficiency for equal spatial resolution compared
to conventional fan-beam and parallel-hole
SPECT.},
Key = {fds164019}
}
@article{6411347,
Author = {Garipagaoglu, M. and Munley, M.T. and Hollis, D. and Poulson, J.M. and Bentel, G.C. and Slbley, G. and Anscher,
M.S. and Ming Fan and Jaszczak, R.J. and Coleman, R.E. and Marks, L.B.},
Title = {The effect of patient-specific factors on radiation-induced
regional lung injury},
Journal = {Int. J. Radiat. Oncol. Biol. Phys. (USA)},
Volume = {45},
Number = {2},
Pages = {331 - 8},
Year = {1},
url = {http://dx.doi.org/10.1016/S0360-3016(99)00201-1},
Keywords = {biological effects of ionising radiation;haemorheology;lung;radiation
therapy;single photon emission computed tomography;},
Abstract = {The authors' purpose was to assess the impact of
patient-specific factors on radiation (RT)-induced
reductions in regional lung perfusion. Fifty patients (32
lung carcinoma, 7 Hodgkin's disease, 9 breast carcinoma and
2 other thoracic tumors) had pre-RT and ⩾24-week post-RT
single photon emission computed tomography (SPECT) perfusion
images to assess the dose dependence of RT-induced
reductions in regional lung perfusion. The SPECT data were
analyzed using a normalized and non-normalized approach.
Furthermore, 2 different mathematical methods were used to
assess the impact of patient-specific factors on the
dose-response curve (DRC). First, DRCs for different patient
subgroups were generated and compared. Second, in a more
formal statistical approach, individual DRCs for regional
lung injury for each patient were fit to a linear-quadratic
model (reduction=coefficient 1×dose+coefficient
2×dose<sup>2</sup>). Multiple patient-specific factors
including tobacco history, pre-RT diffusion capacity to
carbon monoxide (DLCO), transforming growth factor-beta
(TGF-β), chemotherapy exposure, disease type, and mean
lung dose were explored in a multivariate analysis to assess
their impact on the coefficients. None of the variables
tested had a consistent impact on the radiation sensitivity
of regional lung (i.e., the slope of the DRC). In the formal
statistical analysis, there was a suggestion of a slight
increase in radiation sensitivity in the dose range >40
Gy for nonsmokers (vs. smokers) and in those receiving
chemotherapy (vs. no chemotherapy). However, this finding
was very dependent on the specific statistical and
normalization method used. It is concluded that
patient-specific factors do not have a dramatic effect on
RT-induced reduction in regional lung perfusion. Additional
studies are underway to better clarify this issue. The
authors continue to postulate that patient-specific factors
will impact on how the summation of regional injury
translates into whole organ injury. Refinements in the
authors' methods to generate and compare SPECT scans are
needed},
Key = {6411347}
}
@article{2792839,
Author = {Floyd, C.E. and Jaszczak, R.J. and Coleman,
R.E.},
Title = {Image resampling on a cylindrical sector
grid},
Journal = {IEEE Trans. Med. Imaging (USA)},
Volume = {MI-5},
Number = {3},
Pages = {128 - 31},
Keywords = {computerised tomography;},
Abstract = {A cylindrical sensor image grid with equal area pixels for
representing tomographic images is described which offers
computational advantages for some algebraic and stochastic
reconstruction strategies. An evaluation is included for
techniques for resampling from the cylindrical
representation to the standard square pixel representation.
The resampling techniques of nearest-neighbors, bilinear,
cubic <i>B</i> splines, two high-resolution cubic spline,
and overlap weighting are evaluated by their noise
propagation, resolution recovery, noise power spectra, and
visual appearance. Visually, two techniques were superior:
bilinear interpolation, and overlap weighting. In a
comparison of resolution recovery vs. noise, the overlap
weighting provided lower noise and better resolution.
Examination of noise power spectra supported this
observation. With prestored values of the weighting,
computation time for all the techniques is approximately
equal},
Key = {2792839}
}
@article{4592251,
Author = {Zeng, G.L. and Gullberg, G.T. and Jaszczak, R.J. and Li,
J.},
Title = {Fan-beam reconstruction algorithm for a spatially varying
focal length collimator},
Journal = {IEEE Trans. Med. Imaging (USA)},
Volume = {12},
Number = {3},
Pages = {575 - 82},
url = {http://dx.doi.org/10.1109/42.241886},
Keywords = {computerised tomography;image reconstruction;radioisotope
scanning and imaging;},
Abstract = {Fan-beam collimators are used in single-photon-emission
computed tomography (SPECT) to improve the sensitivity for
imaging of small organs. The disadvantage of fan-beam
collimation is the truncation of projection data surrounding
the organ of interest or, in those cases of imaging large
patients, of the organ itself, producing reconstruction
artifacts. A spatially varying focal length fan-beam
collimator has been proposed to eliminate the truncation
problem and to maintain good sensitivity for the organ of
interest. The collimator is constructed so that the shortest
focal lengths are located at the center of the collimator
and the longest focal length is located at the periphery.
The focal length is assumed to increase monotonically toward
the edge of the collimator. A reconstruction algorithm for
this type of fan-beam collimation, expressed as an infinite
series of convolutions followed by one backprojection, is
presented. Simulations show that only a small number of N
terms in the series is needed to obtain high-quality
reconstructions. Computer simulations showed that if the
focal length function is smooth, the reconstructions are
free of artifacts},
Key = {4592251}
}
@article{4570588,
Author = {Turkington, T.G. and Jaszczak, R.J. and Pelizzari, C.A. and Harris, C.C. and MacFall, J.R. and Hoffman, J.M. and Coleman, R.E.},
Title = {Accuracy of registration of PET, SPECT and MR images of a
brain phantom},
Journal = {J. Nucl. Med. (USA)},
Volume = {34},
Number = {9},
Pages = {1587 - 94},
Keywords = {biomedical NMR;brain;computerised tomography;radioisotope
scanning and imaging;},
Abstract = {Accuracy of a surface-fitting algorithm for
three-dimensional (3D) image registration of single photon
emission computed tomography (SPECT), positron emission
tomography (PET), and magnetic resonance (MR) images was
tested using a 3D, water-fillable brain phantom. Multislice
or volume image sets were acquired for each modality. Small
fiducial markers were attached to assess accuracy of surface
fitting and provide an alternate fitting technique. A
maximum gradient technique was found to work well for SPECT
and PET edge detection. Transformation parameters for
translation, rotation and scaling were determined by surface
fit to match each SPECT and PET scan with MR images. Using
the markers, overall translation errors were found to be
<2 mm in each direction and rotational errors <2
degrees in every case. Errors for specific internal regions
were also determined to be <2 mm for most regions, with
only a few fits resulting in errors >3 mm for some
cortical regions. Results indicate surface fitting to be
sufficiently accurate for visual comparison of registered
images and for enhanced SPECT and PET region of interest
determination and image reconstruction},
Key = {4570588}
}
@article{3274735,
Author = {Floyd, C.E., Jr. and Jaszczak, R.J. and Coleman,
R.E.},
Title = {Scatter detection in SPECT imaging: dependence on source
depth, energy, and energy window},
Journal = {Phys. Med. Biol. (UK)},
Volume = {33},
Number = {9},
Pages = {1075 - 81},
url = {http://dx.doi.org/10.1088/0031-9155/33/9/006},
Keywords = {computerised tomography;Monte Carlo methods;radioisotope
scanning and imaging;},
Abstract = {The authors examine the dependence of the scatter fraction
on source depth, the energy window width and the emitted
photon energy, Monte Carlo calculations are presented of
scatter fractions for a line source of activity at eleven
depths in a water-filled cylinder acquired in seven energy
window widths for each of five primary photon energies
corresponding to radionuclides commonly used in nuclear
medicine studies},
Key = {3274735}
}
@article{3498737,
Author = {Liang, Z. and Jaszczak, R. and Greer, K.},
Title = {On Bayesian image reconstruction from projections: uniform
and nonuniform a priori source information},
Journal = {IEEE Trans. Med. Imaging (USA)},
Volume = {8},
Number = {3},
Pages = {227 - 35},
url = {http://dx.doi.org/10.1109/42.34711},
Keywords = {Bayes methods;computerised tomography;},
Abstract = {A method that incorporates a priori uniform or nonuniform
source distribution probabilistic information and data
fluctuations of a Poisson nature is presented. The source
distributions are modeled in terms of a priori source
probability density functions. Maximum a posteriori
probability solutions, as determined by a system of
equations, are given. Interactive Bayesian imaging
algorithms for the solutions are derived using an
expectation maximization technique. Comparisons of the a
priori uniform and nonuniform Bayesian algorithms to the
maximum-likelihood algorithm are carried out using
computer-generated noise-free and Poisson randomized
projections. Improvement in image reconstruction from
projections with the Bayesian algorithm is demonstrated.
Superior results are obtained using the a priori nonuniform
source distribution},
Key = {3498737}
}
@article{3645276,
Author = {Liang, Z. and Jaszczak, R. and Floyd, C. and Greer, K. and Coleman, R.},
Title = {Bayesian reconstruction for SPECT: validation with Monte
Carlo simulation, experimental phantom, and real patient
data},
Journal = {Int. J. Imaging Syst. Technol. (USA)},
Volume = {1},
Number = {2},
Pages = {149 - 68},
Keywords = {Bayes methods;computerised picture processing;computerised
tomography;data acquisition;medical diagnostic
computing;Monte Carlo methods;},
Abstract = {A method for Bayesian image reconstruction from projections
is applied to Monte Carlo simulation, experimental phantom,
and real patient data from a SPECT acquisition system. This
statistical image reconstruction method has three distinct
aspects: it uses a priori information about image density
distribution of a multinomial process; it considers a
spatial correlation of nearby image elements; and it
incorporates the Poisson nature of photon detection
fluctuation. The Monte Carlo simulation data are generated
by computer codes for selected mathematical phantoms
containing hot and cold rods. The experimental phantom data
are acquired with a Triad SPECT system using radioactive
phantoms containing hot and cold rods. The real patient data
are obtained from a patient brain scan using the Triad SPECT
system. A parallel beam geometry is used. The data are
acquired from 120 projection angles uniformly distributed
from 0 to 360 degrees. At each projection angle, a
128×128 projection image is measured. This
128×128 projection samples are equally spaced along
the axis of detector rotation and perpendicular to the axis,
respectively. Each image slice is reconstructed using a
128×128 pixel array. Comparisons between this Bayesian
method and maximum likelihood method and filtered
backprojection method are given. An improvement in noise
suppression is demonstrated using the Bayesian method while
image resolution is preserved},
Key = {3645276}
}
@article{4497530,
Author = {Huili Wang and Jaszczak, R.J. and Coleman,
R.E.},
Title = {A new composite model of objects for Monte Carlo simulation
of radiological imaging},
Journal = {Phys. Med. Biol. (UK)},
Volume = {38},
Number = {9},
Pages = {1235 - 62},
url = {http://dx.doi.org/10.1088/0031-9155/38/9/005},
Keywords = {modelling;Monte Carlo methods;radiology;},
Abstract = {A composite object model is proposed for Monte Carlo
simulation of radiological imaging systems. The composite
model contains four components: a set of regular and
`voxelized' primitives, a `modular' inclusion tree, a set of
designated constructive solid geometry (CSG) trees, and a
mapping from the set of CSG trees to the inclusion tree. The
voxelized primitive is a primitive containing a stack of
voxels whose intersections with a photon path are calculated
based on Siddon's method. The inclusion tree is employed to
describe the inclusion relationships of homogeneous
subregions of material characteristics in larger regions in
an object. The model is designed so that the
`divide-and-conquer' principle for modular software design
can be used to construct an inclusion tree for a complex
object. The designated CSG trees are used to model source
distributions},
Key = {4497530}
}
@article{2398382,
Author = {Harris, C.C. and Greer, K.L. and Jaszczak, R.J. and Floyd,
C.E., Jr. and Fearnow, E.C. and Coleman,
R.E.},
Title = {Tc-99m attenuation coefficients in water-filled
phantoms determined with gamma cameras},
Journal = {Med. Phys. (USA)},
Volume = {11},
Number = {5},
Pages = {681 - 5},
url = {http://dx.doi.org/10.1118/1.595623},
Keywords = {radioisotope scanning and imaging;},
Abstract = {Quantitative imaging with gamma cameras requires
compensation for attenuation of source photons. Some methods
of compensation make use of a constant or average estimated
attenuation coefficient μ. A value for μ of 0.15
cm<sup>-1</sup> for 140.5-keV photons in water or tissue is
commonly used. This value, however, neglects scattered
photons which are detected within the energy window in gamma
camera imaging. Values for μ of 0.12 cm<sup>-1</sup> used
in attenuation compensation of Tc-99<i>m</i> single-photon
emission computed tomography scans of uniform cylindrical
sources have been shown to give improved results compared
with use of μ=0.15 cm<sup>-1</sup>. In this study, gamma
cameras and a multichannel pulse-height analyzer were used
to determine effective values of μ for photons in water
as a function of energy window. Two cylindrical water-filled
phantoms, circular and elliptical, were used with a point
source of Tc-99<i>m</i> at depths up to 18 cm. Energy data
were integrated over the top half of the photopeak, and over
10%, 20%, and 30% windows centered on the photopeak.
Attenuation curves were exponential for all photopeak
windows with values of μ of 0.12±0.014
cm<sup>-1</sup> for all windows up to 20% and 0.1
cm<sup>-1</sup> for a 30% window. This study suggests that a
value of μ of 0.11-0.12 cm<sup>-1</sup> is, in fact,
appropriate for use in attenuation compensations where an
average is required},
Key = {2398382}
}
@article{4570586,
Author = {Jaszczak, R.J. and Gilland, D.R. and Hanson, M.W. and Jang,
S. and Greer, K.L. and Coleman, R.E.},
Title = {Fast transmission CT for determining attenuation maps using
a collimated line source, rotatable air-copper-lead
attenuators and fan-beam collimation},
Journal = {J. Nucl. Med. (USA)},
Volume = {34},
Number = {9},
Pages = {1577 - 86},
Keywords = {computerised tomography;radioisotope scanning and
imaging;},
Abstract = {Describes a technique using a line source and a rotatable
air-copper-lead (RACL) assembly to acquire gamma
transmission computed tomographic (TCT) data for determining
attenuation maps to compensate SPECT emission scans. The
technique minimizes problems associated with discriminating
<sup>99m</sup>Tc transmission and <sup>201</sup>Tl emission
photons and requires only a modest increase in total study
time. A <sup>99m</sup>Tc line source and a stacked foil
(“multislat”) collimator are placed near the
focal line of a fan-beam collimator (114 cm focal length)
mounted on 1 detector of a triple-camera SPECT system. The
authors acquired TCT data of plastic rod and anthropomorphic
thorax phantoms to investigate the capability of the line
source and RACL attenuators to determine attenuation maps.
The data were acquired with and without 5.4 MBq (145 μCi)
of <sup>201</sup>Tl placed in the myocardial chamber of the
thorax phantom. Phantoms also were scanned using a curved
transmission slab source mounted to a parallel-hole
collimator. Fan-beam TCT images have improved resolution
compared with parallel-beam TCT images. Two patient scans
also were performed to evaluate the clinical usefulness of
fan-beam TCT. The RACL attenuator method eliminates
contamination of emission data by transmission photons and
reduces spill-over of emission data into the transmission
energy window for some cases. Results show the feasibility
of using fast, sequential or interlaced transmission scans
of a line source within a RACL attenuator assembly to obtain
accurate attenuation maps for SPECT attenuation
compensation},
Key = {4570586}
}
@article{4293833,
Author = {Wang, H. and Jaszczak, R.J. and Coleman,
R.E.},
Title = {Solid geometry-based object model for Monte Carlo simulated
emission and transmission tomographic imaging
systems},
Journal = {IEEE Trans. Med. Imaging (USA)},
Volume = {11},
Number = {3},
Pages = {361 - 72},
url = {http://dx.doi.org/10.1109/42.158940},
Keywords = {computerised tomography;modelling;Monte Carlo
methods;radioisotope scanning and imaging;},
Abstract = {An object model based on combinations of object primitives
is proposed for Monte Carlo simulated emission and
transmission tomographic imaging systems. The primitives
include ellipsoids, elliptic cylinders, tapered elliptic
cylinders, rectangular solids, and their subsets: half,
quarter, and eighth. The probability of a photon surviving
interactions with the phantom medium is used as a weight for
variance reduction. Calculation of the probability can be
computationally intensive without properly organizing the
inclusion of subregions within larger regions. A tree data
structure is introduced to organize this inclusion
relationship and used as the basis for two computationally
efficient schemes for determining the intersection locations
of a photon path with primitives and for identifying the
attenuation coefficients for adjacent intersections for the
survival probability computation. The approach has been
validated by emission as well as transmission simulations. A
thorax phantom containing overlapped ellipsoids and a heart
composed of twelve overlapped quarter ellipsoids are
employed to demonstrate the capability of the
model},
Key = {4293833}
}
@article{5713584,
Author = {Gilland, D.R. and Jaszczak, R.J. and Riauka, T.A. and Coleman, R.E.},
Title = {Approximate 3D iterative reconstruction for
SPECT},
Journal = {Med. Phys. (USA)},
Volume = {24},
Number = {9},
Pages = {1421 - 9},
url = {http://dx.doi.org/10.1118/1.598030},
Keywords = {brain;image reconstruction;iterative methods;medical image
processing;single photon emission computed
tomography;},
Abstract = {Compared with slice-by-slice approaches for SPECT
reconstruction, three-dimensional iterative methods provide
a more accurate physical model and an improved SPECT image.
Clinical application of these methods, however, is limited
primarily by their computational demands. This paper
investigates methods for approximate 3D iterative
reconstruction that greatly reduce this demand by excluding
from the reconstruction the smaller magnitude elements of
the system matrix. A new method is described which is
designed to control the resulting bias in the SPECT image
for a given reduction in computation. The approximate
methods were compared to fully 3D iterative reconstruction
in terms of SPECT image bias and visual quality. All methods
were incorporated into the ML-EM algorithm and applied to
data from 3D mathematical and experimental brain phantoms.
The SPECT images reconstructed by the approximate methods
exhibited a positive bias throughout the image that was in
general smaller with the new method (in the range of 2%-6%).
The bias was smallest in locally hot regions and largest in
locally cold regions. The high quality brain phantom images
demonstrated the capability of the new method in realistic
imaging contexts. The time per iteration for an entire 3D
brain phantom on a modern workstation using the approximate
3D method was 7.9 s},
Key = {5713584}
}
%% Johnson, G. Allan
@article{fds161590,
Author = {GP Howles and JC Nouls and Y Qi and GA Johnson},
Title = {Rapid production of specialized animal handling devices
using computer-aided design and solid freeform
fabrication.},
Journal = {Journal of magnetic resonance imaging : JMRI, United
States},
Volume = {30},
Number = {2},
Pages = {466-71},
Year = {2009},
Month = {August},
ISSN = {1053-1807},
Abstract = {PURPOSE: To develop a process for rapidly and inexpensively
producing customized animal handling devices for small
animal imaging. MATERIALS AND METHODS: To meet the specific
needs of a particular imaging experiment, measurements are
taken from imaging data and the animal handling devices are
designed using 3D computer-aided design (CAD) software.
Parts are produced in a few days using solid freeform
fabrication (SFF, a.k.a. rapid prototyping). RESULTS: This
process is illustrated with the production of an animal
handling system for stereotaxically prescribed therapeutic
ultrasound and MRI of the mouse brain. The device provides
integrated head-fixation, anesthesia delivery, and
physiological monitoring in a modular system. Design and
production took approximately 1 week and the cost was a
small fraction of a traditional machine shop. CONCLUSION:
Commercial animal handling products typically have limited
functionality and are not integrated with other laboratory
infrastructure. However, using CAD and SFF, sophisticated
animal handling devices can be produced to meet the specific
experimental needs. This process is typically faster and
less expensive than using a traditional machine shop, and
the products are more robust than typical homemade devices.
Using high-quality purpose-built devices permits experiments
to be executed with greater consistency and higher
throughput.},
Key = {fds161590}
}
@article{fds161592,
Author = {A Badea and GA Johnson and RW Williams},
Title = {Genetic dissection of the mouse CNS using magnetic resonance
microscopy.},
Journal = {Current opinion in neurology, England},
Volume = {22},
Number = {4},
Pages = {379-86},
Year = {2009},
Month = {August},
ISSN = {1473-6551},
Abstract = {PURPOSE OF REVIEW: Advances in magnetic resonance microscopy
(MRM) make it practical to map gene variants responsible for
structural variation in brains of many species, including
mice and humans. We review results of a systematic genetic
analysis of MRM data using as a case study a family of well
characterized lines of mice. RECENT ADVANCES: MRM has
matured to the point that we can generate high contrast,
high-resolution images even for species as small as a mouse,
with a brain merely 1/3000th the size of humans. We
generated 21.5-micron data sets for a diverse panel of BXD
mouse strains to gauge the extent of genetic variation, and
as a prelude to comprehensive genetic and genomic analyses.
Here we review MRM capabilities and image segmentation
methods; heritability of brain variation; covariation of the
sizes of brain regions; and correlations between MRM and
classical histological data sets. SUMMARY: The combination
of high throughput MRM and genomics will improve our
understanding of the genetic basis of structure-function
correlations. Sophisticated mouse models will be critical in
converting correlations into mechanisms and in determining
genetic and epigenetic causes of differences in disease
susceptibility.},
Key = {fds161592}
}
@article{fds161594,
Author = {A Mackenzie-Graham and SK Tiwari-Woodruff and G Sharma and C Aguilar and KT Vo and LV Strickland and L Morales and B Fubara and M Martin and RE
Jacobs, GA Johnson and AW Toga and RR Voskuhl},
Title = {Purkinje cell loss in experimental autoimmune
encephalomyelitis.},
Journal = {NeuroImage},
Year = {2009},
Month = {July},
ISSN = {1095-9572},
Abstract = {Gray matter atrophy observed by brain MRI is an important
correlate to clinical disability and disease duration in
multiple sclerosis. The objective of this study was to link
brain atrophy visualized by neuroimaging to its underlying
neuropathology using the MS model, experimental autoimmune
encephalomyelitis (EAE). Volumetric changes in brains of EAE
mice, as well as matched healthy normal controls, were
quantified by collecting post-mortem high-resolution
T2-weighted magnetic resonance microscopy and actively
stained magnetic resonance histology images. Anatomical
delineations demonstrated a significant decrease in the
volume of the whole cerebellum, cerebellar cortex, and
molecular layer of the cerebellar cortex in EAE as compared
to normal controls. The pro-apoptotic marker caspase-3 was
detected in Purkinje cells and a significant decrease in
Purkinje cell number was found in EAE. Cross modality and
temporal correlations revealed a significant association
between Purkinje cell loss on neuropathology and atrophy of
the molecular layer of the cerebellar cortex by
neuroimaging. These results demonstrate the power of using
combined population atlasing and neuropathology approaches
to discern novel insights underlying gray matter atrophy in
animal models of neurodegenerative disease.},
Key = {fds161594}
}
@article{fds161591,
Author = {A Badea and GA Johnson and RW Williams},
Title = {Genetic dissection of the mouse brain using high-field
magnetic resonance microscopy.},
Journal = {NeuroImage, United States},
Volume = {45},
Number = {4},
Pages = {1067-79},
Year = {2009},
Month = {May},
ISSN = {1095-9572},
Keywords = {Animals Brain Magnetic Resonance Imaging Mice Mice, Inbred
C57BL Mice, Inbred DBA Mice, Inbred Strains Microscopy
Species Specificity anatomy & histology cytology* genetics*
methods* physiology*},
Abstract = {Magnetic resonance (MR) imaging has demonstrated that
variation in brain structure is associated with differences
in behavior and disease state. However, it has rarely been
practical to prospectively test causal models that link
anatomical and functional differences in humans. In the
present study we have combined classical mouse genetics with
high-field MR to systematically explore and test such
structure-functional relations across multiple brain
regions. We segmented 33 regions in two parental
strains-C57BL/6J (B) and DBA/2J (D)-and in nine BXD
recombinant inbred strains. All strains have been studied
extensively for more than 20 years using a battery of
genetic, functional, anatomical, and behavioral assays. We
compared levels of variation within and between strains and
sexes, by region, and by system. Average within-strain
variation had a coefficient of variation (CV) of 1.6% for
the whole brain; while the CV ranged from 2.3 to 3.6% for
olfactory bulbs, cortex and cerebellum, and up to
approximately 18% for septum and laterodorsal thalamic
nucleus. Variation among strain averages ranged from 6.7%
for cerebellum, 7.6% for whole brain, 9.0% for cortex, up to
approximately 26% for the ventricles, laterodorsal thalamic
nucleus, and the interpeduncular nucleus. Heritabilities
averaged 0.60+/-0.18. Sex differences were not significant
with the possible (and unexpected) exception of the pons (
approximately 20% larger in males). A correlation matrix of
regional volumes revealed high correlations among
functionally related parts of the CNS (e.g., components of
the limbic system), and several high correlations between
regions that are not anatomically connected, but that may
nonetheless be functionally or genetically
coupled.},
Key = {fds161591}
}
@article{fds161593,
Author = {J Song and Y Liu and SL Gewalt and G Cofer and GA Johnson and QH
Liu},
Title = {Least-square NUFFT methods applied to 2-D and 3-D radially
encoded MR image reconstruction.},
Journal = {IEEE transactions on bio-medical engineering, United
States},
Volume = {56},
Number = {4},
Pages = {1134-42},
Year = {2009},
Month = {April},
ISSN = {1558-2531},
Keywords = {Animals Computer Simulation Image Processing,
Computer-Assisted Least-Squares Analysis* Magnetic Resonance
Imaging Mice Models, Statistical Phantoms, Imaging
methods*},
Abstract = {Radially encoded MRI has gained increasing attention due to
its motion insensitivity and reduced artifacts. However,
because its samples are collected nonuniformly in the
k-space, multidimensional (especially 3-D) radially sampled
MRI image reconstruction is challenging. The objective of
this paper is to develop a reconstruction technique in high
dimensions with on-the-fly kernel calculation. It implements
general multidimensional nonuniform fast Fourier transform
(NUFFT) algorithms and incorporates them into a k-space
image reconstruction framework. The method is then applied
to reconstruct from the radially encoded k-space data,
although the method is applicable to any non-Cartesian
patterns. Performance comparisons are made against the
conventional Kaiser-Bessel (KB) gridding method for 2-D and
3-D radially encoded computer-simulated phantoms and
physically scanned phantoms. The results show that the NUFFT
reconstruction method has better accuracy-efficiency
tradeoff than the KB gridding method when the kernel weights
are calculated on the fly. It is found that for a particular
conventional kernel function, using its corresponding
deapodization function as a scaling factor in the NUFFT
framework has the potential to improve accuracy. In
particular, when a cosine scaling factor is used, the NUFFT
method is faster than KB gridding method since a closed-form
solution is available and is less computationally expensive
than the KB kernel (KB griding requires computation of
Bessel functions). The NUFFT method has been successfully
applied to 2-D and 3-D in vivo studies on small
animals.},
Key = {fds161593}
}
@article{fds161596,
Author = {X Zhang and C Badea and M Jacob and GA Johnson},
Title = {Development of a noncontact 3-D fluorescence tomography
system for small animal in vivo imaging.},
Journal = {Proceedings - Society of Photo-Optical Instrumentation
Engineers},
Volume = {7191},
Pages = {nihpa106691},
Year = {2009},
Month = {February},
ISSN = {1018-4732},
Abstract = {Fluorescence imaging is an important tool for tracking
molecular-targeting probes in preclinical studies. It offers
high sensitivity, but nonetheless low spatial resolution
compared to other leading imaging methods such CT and MRI.
We demonstrate our methodological development in small
animal in vivo whole-body imaging using fluorescence
tomography. We have implemented a noncontact fluid-free
fluorescence diffuse optical tomography system that uses a
raster-scanned continuous-wave diode laser as the light
source and an intensified CCD camera as the photodetector.
The specimen is positioned on a motorized rotation stage.
Laser scanning, data acquisition, and stage rotation are
controlled via LabVIEW applications. The forward problem in
the heterogeneous medium is based on a normalized Born
method, and the sensitivity function is determined using a
Monte Carlo method. The inverse problem (image
reconstruction) is performed using a regularized iterative
algorithm, in which the cost function is defined as a
weighted sum of the L-2 norms of the solution image, the
residual error, and the image gradient. The relative weights
are adjusted by two independent regularization parameters.
Our initial tests of this imaging system were performed with
an imaging phantom that consists of a translucent plastic
cylinder filled with tissue-simulating liquid and two
thin-wall glass tubes containing indocyanine green. The
reconstruction is compared to the output of a finite element
method-based software package NIRFAST and has produced
promising results.},
Key = {fds161596}
}
@article{fds161597,
Title = {A Petiet, GA Johnson, Active Staining of Mouse Embryos for
Magnetic Resonance Microscopy. In: Hewitson Tim D & Darby
Ian A (editors), Histology Protocols (Methods in Molecular
Biology), Springer- Humana Press. Totowa, NJ. USA, in press,
2009},
Year = {2009},
Key = {fds161597}
}
@article{fds157108,
Author = {CT Badea and M Drangova and DW Holdsworth and GA Johnson},
Title = {In vivo small-animal imaging using micro-CT and digital
subtraction angiography.},
Journal = {Physics in medicine and biology, England},
Volume = {53},
Number = {19},
Pages = {R319-50},
Year = {2008},
Month = {October},
ISSN = {0031-9155},
Keywords = {Angiography, Digital Subtraction Animals Humans X-Ray
Microtomography instrumentation methods*},
Abstract = {Small-animal imaging has a critical role in phenotyping,
drug discovery and in providing a basic understanding of
mechanisms of disease. Translating imaging methods from
humans to small animals is not an easy task. The purpose of
this work is to review in vivo x-ray based small-animal
imaging, with a focus on in vivo micro-computed tomography
(micro-CT) and digital subtraction angiography (DSA). We
present the principles, technologies, image quality
parameters and types of applications. We show that both
methods can be used not only to provide morphological, but
also functional information, such as cardiac function
estimation or perfusion. Compared to other modalities, x-ray
based imaging is usually regarded as being able to provide
higher throughput at lower cost and adequate resolution. The
limitations are usually associated with the relatively poor
contrast mechanisms and potential radiation damage due to
ionizing radiation, although the use of contrast agents and
careful design of studies can address these limitations. We
hope that the information will effectively address how x-ray
based imaging can be exploited for successful in vivo
preclinical imaging.},
Key = {fds157108}
}
@article{fds157081,
Author = {AE Petiet and MH Kaufman and MM Goddeeris and J Brandenburg and SA
Elmore, GA Johnson},
Title = {High-resolution magnetic resonance histology of the
embryonic and neonatal mouse: a 4D atlas and morphologic
database.},
Journal = {Proceedings of the National Academy of Sciences of the
United States of America, United States},
Volume = {105},
Number = {34},
Pages = {12331-6},
Year = {2008},
Month = {August},
ISSN = {1091-6490},
Keywords = {Anatomy, Cross-Sectional Animals Animals, Newborn Databases,
Factual Embryo, Mammalian Embryonic Development* Heart
Septal Defects Imaging, Three-Dimensional Magnetic Resonance
Imaging Mice Mice, Mutant Strains Mice, Transgenic
Microscopy Time Factors anatomy & histology* instrumentation
methods*},
Abstract = {Engineered mice play an ever-increasing role in defining
connections between genotype and phenotypic expression. The
potential of magnetic resonance microscopy (MRM) for
morphologic phenotyping in the mouse has previously been
demonstrated; however, applications have been limited by
long scan times, availability of the technology, and a
foundation of normative data. This article describes an
integrated environment for high-resolution study of normal,
transgenic, and mutant mouse models at embryonic and
neonatal stages. Three-dimensional images are shown at an
isotropic resolution of 19.5 microm (voxel volumes of 8 pL),
acquired in 3 h at embryonic days 10.5-19.5 (10 stages) and
postnatal days 0-32 (6 stages). A web-accessible atlas
encompassing this data was developed, and for critical
stages of embryonic development (prenatal days 14.5-18.5),
>200 anatomical structures have been identified and labeled.
Also, matching optical histology and analysis tools are
provided to compare multiple specimens at multiple
developmental stages. The utility of the approach is
demonstrated in characterizing cardiac septal defects in
conditional mutant embryos lacking the Smoothened receptor
gene. Finally, a collaborative paradigm is presented that
allows sharing of data across the scientific community. This
work makes magnetic resonance microscopy of the mouse embryo
and neonate broadly available with carefully annotated
normative data and an extensive environment for
collaborations.},
Key = {fds157081}
}
@article{fds157085,
Author = {M De Lin and G Toncheva and G Nguyen and S Kim and C Anderson-Evans and GA
Johnson, TT Yoshizumi},
Title = {Application of MOSFET detectors for dosimetry in small
animal radiography using short exposure times.},
Journal = {Radiation research, United States},
Volume = {170},
Number = {2},
Pages = {260-3},
Year = {2008},
Month = {August},
ISSN = {0033-7587},
Keywords = {Equipment Design Equipment Failure Analysis Radiation Dosage
Radiographic Image Enhancement Radiometry Sensitivity and
Specificity Transducers* Transistors* instrumentation*
methods},
Abstract = {Digital subtraction angiography (DSA) X-ray imaging for
small animals can be used for functional phenotyping given
its ability to capture rapid physiological changes at high
spatial and temporal resolution. The higher temporal and
spatial requirements for small-animal imaging drive the need
for short, high-flux X-ray pulses. However, high doses of
ionizing radiation can affect the physiology. The purpose of
this study was to verify and apply metal oxide semiconductor
field effect transistor (MOSFET) technology to dosimetry for
small-animal diagnostic imaging. A tungsten anode X-ray
source was used to expose a tissue-equivalent mouse phantom.
Dose measurements were made on the phantom surface and
interior. The MOSFETs were verified with thermoluminescence
dosimeters (TLDs). Bland-Altman analysis showed that the
MOSFET results agreed with the TLD results (bias, 0.0625).
Using typical small animal DSA scan parameters, the dose
ranged from 0.7 to 2.2 cGy. Application of the MOSFETs in
the small animal environment provided two main benefits: (1)
the availability of results in near real-time instead of the
hours needed for TLD processes and (2) the ability to
support multiple exposures with different X-ray techniques
(various of kVp, mA and ms) using the same MOSFET. This
MOSFET technology has proven to be a fast, reliable small
animal dosimetry method for DSA imaging and is a good system
for dose monitoring for serial and gene expression
studies.},
Key = {fds157085}
}
@article{fds157106,
Author = {S Shofer and C Badea and Y Qi and E Potts and WM Foster and GA
Johnson},
Title = {A micro-CT analysis of murine lung recruitment in
bleomycin-induced lung injury.},
Journal = {Journal of applied physiology (Bethesda, Md. : 1985), United
States},
Volume = {105},
Number = {2},
Pages = {669-77},
Year = {2008},
Month = {August},
ISSN = {8750-7587},
Keywords = {Animals Antibiotics, Antineoplastic* Bleomycin* Collagen
Female Image Processing, Computer-Assisted Lung Compliance
Lung Diseases Mice Pulmonary Alveoli Respiratory Function
Tests Respiratory Mechanics Tidal Volume Tomography, X-Ray
Computed chemically induced* metabolism pathology pathology*
physiology physiopathology},
Abstract = {The effects of lung injury on pulmonary recruitment are
incompletely understood. X-ray computed tomography (CT) has
been a valuable tool in assessing changes in recruitment
during lung injury. With the development of preclinical CT
scanners designed for thoracic imaging in rodents, it is
possible to acquire high-resolution images during the
evolution of a pulmonary injury in living mice. We
quantitatively assessed changes in recruitment caused by
intratracheal bleomycin at 1 and 3 wk after administration
using micro-CT in 129S6/SvEvTac mice. Twenty female mice
were administered 2.5 U of bleomycin or saline and imaged
with micro-CT at end inspiration and end expiration. Mice
were extubated and allowed to recover from anesthesia and
then reevaluated in vivo for quasi-static compliance
measurements, followed by harvesting of the lungs for
collagen analysis and histology. CT images were converted to
histograms and analyzed for mean lung attenuation (MLA). MLA
was significantly greater for bleomycin-exposed mice at week
1 for both inspiration (P<0.0047) and exhalation (P<0.0377)
but was not significantly different for week 3
bleomycin-exposed mice. However, week 3 bleomycin-exposed
mice did display significant increases in MLA shift from
expiration to inspiration compared with either group of
control mice (P<0.005), suggesting increased lung
recruitment at this time point. Week 1 bleomycin-exposed
mice displayed normal shifts in MLA with inspiration,
suggesting normal lung recruitment despite significant
radiographic and histological changes. Lung alveolar
recruitment is preserved in a mouse model of
bleomycin-induced parenchymal injury despite significant
changes in radiographic and physiological
parameters.},
Key = {fds157106}
}
@article{fds157091,
Author = {E Bucholz and K Ghaghada and Y Qi and S Mukundan and GA
Johnson},
Title = {Four-dimensional MR microscopy of the mouse heart using
radial acquisition and liposomal gadolinium contrast
agent.},
Journal = {Magnetic resonance in medicine : official journal of the
Society of Magnetic Resonance in Medicine / Society of
Magnetic Resonance in Medicine, United States},
Volume = {60},
Number = {1},
Pages = {111-8},
Year = {2008},
Month = {July},
ISSN = {0740-3194},
Keywords = {Animals Contrast Media Gadolinium Heart Liposomes Magnetic
Resonance Imaging Mice Microscopy anatomy & histology
diagnostic use methods methods* physiology*},
Abstract = {Magnetic resonance microscopy (MRM) has become an important
tool for small animal cardiac imaging. In relation to
competing technologies (microCT and ultrasound), MR is
limited by spatial resolution, temporal resolution, and
acquisition time. All three of these limitations have been
addressed by developing a four-dimensional (4D) (3D plus
time) radial acquisition (RA) sequence. The signal-to-noise
ratio (SNR) has been optimized by minimizing the echo time
(TE) (300 us). The temporal resolution and throughput have
been improved by center-out trajectories resulting in
repetition time (TR) <2.5 ms. The contrast has been enhanced
through the use of a liposomal blood pool agent that reduces
the T(1) of the blood to <400 ms. We have developed
protocols for three specific applications: 1)
high-throughput with spatial resolution of 87 x 87 x 352
um(3) (voxel volume = 2.7 nL) and acquisition time of 16
min; 2) high-temporal resolution with spatial resolution of
87 x 87 x 352 um(3) (voxel volume = 2.7 nL) and temporal
resolution at 4.8 ms and acquisition time of 32 minutes; and
3) high-resolution isotropic imaging at 87 x 87 x 87 um(3)
(voxel volume = 0.68 nL) and acquisition time of 31 min. The
4D image arrays allow direct measure of cardiac functional
parameters dependent on chamber volumes, e.g., ejection
fraction (EF), end diastolic volume (EDV), and end systolic
volume (ESV).},
Key = {fds157091}
}
@article{fds157101,
Author = {SM Johnston and GA Johnson and CT Badea},
Title = {Geometric calibration for a dual tube/detector micro-CT
system.},
Journal = {Medical physics, United States},
Volume = {35},
Number = {5},
Pages = {1820-9},
Year = {2008},
Month = {May},
ISSN = {0094-2405},
Keywords = {Algorithms Animals Artifacts Calibration Equipment Design
Humans Metals Mice Models, Statistical Models, Theoretical
Phantoms, Imaging Radiographic Image Interpretation,
Computer-Assisted Reproducibility of Results Tomography
Scanners, X-Ray Computed Tomography, X-Ray Computed X-Rays
instrumentation* methods methods*},
Abstract = {The authors describe a dual tube/detector micro-computed
tomography (micro-CT) system that has the potential to
improve temporal resolution and material contrast in small
animal imaging studies. To realize this potential, it is
necessary to precisely calibrate the geometry of a dual
micro-CT system to allow the combination of projection data
acquired with each individual tube/detector in a single
reconstructed image. The authors present a geometric
calibration technique that uses multiple projection images
acquired with the two imaging chains while rotating a
phantom containing a vertical array of regularly spaced
metallic beads. The individual geometries of the imaging
chains are estimated from the phantom projection images
using analytical methods followed by a refinement procedure
based on nonlinear optimization. The geometric parameters
are used to create the cone beam projection matrices
required by the reconstruction process for each imaging
chain. Next, a transformation between the two projection
matrices is found that allows the combination of projection
data in a single reconstructed image. The authors describe
this technique, test it with a series of computer
simulations, and then apply it to data collected from their
dual tube/detector micro-CT system. The results demonstrate
that the proposed technique is accurate, robust, and
produces images free of misalignment artifacts.},
Key = {fds157101}
}
@article{fds157112,
Author = {MM Goddeeris and S Rho and A Petiet and CL Davenport and GA Johnson and EN
Meyers, J Klingensmith},
Title = {Intracardiac septation requires hedgehog-dependent cellular
contributions from outside the heart.},
Journal = {Development (Cambridge, England), England},
Volume = {135},
Number = {10},
Pages = {1887-95},
Year = {2008},
Month = {May},
ISSN = {0950-1991},
Keywords = {Animals Fetal Heart Heart Atria Heart Septal Defects,
Ventricular Hedgehog Proteins Mesoderm Mice Mice, Mutant
Strains Mutation Signal Transduction cytology cytology*
embryology genetics metabolism*},
Abstract = {Septation of the mammalian heart into four chambers requires
the orchestration of multiple tissue progenitors.
Abnormalities in this process can result in potentially
fatal atrioventricular septation defects (AVSD). The
contribution of extracardiac cells to atrial septation has
recently been recognized. Here, we use a genetic marker and
novel magnetic resonance microscopy techniques to
demonstrate the origins of the dorsal mesenchymal protrusion
in the dorsal mesocardium, and its substantial contribution
to atrioventricular septation. We explore the functional
significance of this tissue to atrioventricular septation
through study of the previously uncharacterized AVSD
phenotype of Shh(-/-) mutant mouse embryos. We demonstrate
that Shh signaling is required within the dorsal mesocardium
for its contribution to the atria. Failure of this addition
results in severe AVSD. These studies demonstrate that AVSD
can result from a primary defect in dorsal mesocardium,
providing a new paradigm for the understanding of human
AVSD.},
Key = {fds157112}
}
@article{fds157097,
Author = {CT Badea and AW Wetzel and N Mistry and S Pomerantz and D Nave and GA
Johnson},
Title = {Left ventricle volume measurements in cardiac micro-CT: the
impact of radiation dose and contrast agent.},
Journal = {Computerized medical imaging and graphics : the official
journal of the Computerized Medical Imaging Society, United
States},
Volume = {32},
Number = {3},
Pages = {239-50},
Year = {2008},
Month = {April},
ISSN = {0895-6111},
Keywords = {Animals Contrast Media Heart Ventricles Imaging,
Three-Dimensional Mice Mice, Inbred C57BL Radiation Dosage
Radiographic Image Interpretation, Computer-Assisted
Tomography, X-Ray Computed administration & dosage methods*
radiography*},
Abstract = {Micro-CT-based cardiac function estimation in small animals
requires measurement of left ventricle (LV) volume at
multiple time points during the cardiac cycle. Measurement
accuracy depends on the image resolution, its signal and
noise properties, and the analysis procedure. This work
compares the accuracy of the Otsu thresholding and a region
sampled binary mixture approach, for live mouse LV volume
measurement using 100 microm resolution datasets. We
evaluate both analysis methods after varying the volume of
injected contrast agent and the number of projections used
for CT reconstruction with a goal of permitting reduced
levels of both X-ray and contrast agent doses.},
Key = {fds157097}
}
@article{fds157114,
Author = {JC Nouls and MG Izenson and HP Greeley and GA Johnson},
Title = {Design of a superconducting volume coil for magnetic
resonance microscopy of the mouse brain.},
Journal = {Journal of magnetic resonance (San Diego, Calif. : 1997),
United States},
Volume = {191},
Number = {2},
Pages = {231-8},
Year = {2008},
Month = {April},
ISSN = {1090-7807},
Keywords = {Animals Brain Electric Conductivity Equipment Design
Equipment Failure Analysis Magnetic Resonance Imaging
Magnetics Mice Microscopy Transducers cytology*
instrumentation* methods* veterinary veterinary*},
Abstract = {We present the design process of a superconducting volume
coil for magnetic resonance microscopy of the mouse brain at
9.4T. The yttrium barium copper oxide coil has been designed
through an iterative process of three-dimensional
finite-element simulations and validation against room
temperature copper coils. Compared to previous designs, the
Helmholtz pair provides substantially higher B(1)
homogeneity over an extended volume of interest sufficiently
large to image biologically relevant specimens. A
custom-built cryogenic cooling system maintains the
superconducting probe at 60+/-0.1K. Specimen loading and
probe retuning can be carried out interactively with the
coil at operating temperature, enabling much higher
through-put. The operation of the probe is a routine,
consistent procedure. Signal-to-noise ratio in a mouse brain
increased by a factor ranging from 1.1 to 2.9 as compared to
a room-temperature solenoid coil optimized for mouse brain
microscopy. We demonstrate images encoded at 10x10x20mum for
an entire mouse brain specimen with signal-to-noise ratio of
18 and a total acquisition time of 16.5h, revealing
neuroanatomy unseen at lower resolution. Phantom
measurements show an effective spatial resolution better
than 20mum.},
Key = {fds157114}
}
@article{fds157080,
Author = {EK Bucholz and J Song and GA Johnson and I Hancu},
Title = {Multispectral imaging with three-dimensional rosette
trajectories.},
Journal = {Magnetic resonance in medicine : official journal of the
Society of Magnetic Resonance in Medicine / Society of
Magnetic Resonance in Medicine, United States},
Volume = {59},
Number = {3},
Pages = {581-9},
Year = {2008},
Month = {March},
ISSN = {0740-3194},
Keywords = {Adipose Tissue Algorithms Artifacts Body Water Brain Mapping
Computer Simulation Humans Image Processing,
Computer-Assisted* Imaging, Three-Dimensional* Magnetic
Resonance Imaging anatomy & histology methods*},
Abstract = {Two-dimensional intersecting k-space trajectories have
previously been demonstrated to allow fast multispectral
imaging. Repeated sampling of k-space points leads to
destructive interference of the signal coming from the
off-resonance spectral peaks; on-resonance data
reconstruction yields images of the on-resonance peak, with
some of the off-resonance energy being spread as noise in
the image. A shift of the k-space data by a given
off-resonance frequency brings a second frequency of
interest on resonance, allowing the reconstruction of a
second spectral peak from the same k-space data. Given the
higher signal-to-noise per unit time characteristic of a 3D
acquisition, we extended the concept of intersecting
trajectories to three dimensions. A 3D, rosette-like pulse
sequence was designed and implemented on a clinical 1.5T
scanner. An iterative density compensation function was
developed to weight the 3D intersecting trajectories before
Fourier transformation. Three volunteers were scanned using
this sequence and separate fat and water images were
reconstructed from the same imaging dataset.},
Key = {fds157080}
}
@article{fds157083,
Author = {M de Lin and L Ning and CT Badea and NN Mistry and Y Qi and GA
Johnson},
Title = {A high-precision contrast injector for small animal x-ray
digital subtraction angiography.},
Journal = {IEEE transactions on bio-medical engineering, United
States},
Volume = {55},
Number = {3},
Pages = {1082-91},
Year = {2008},
Month = {March},
ISSN = {0018-9294},
Keywords = {Angiography, Digital Subtraction Animals Contrast Media
Equipment Design Equipment Failure Analysis Iopamidol Mice
Microinjections Radiographic Image Enhancement
Reproducibility of Results Sensitivity and Specificity
administration & dosage administration & dosage*
instrumentation* methods veterinary*},
Abstract = {The availability of genetically altered animal models of
human disease for basic research has generated great
interest in new imaging methodologies. Digital subtraction
angiography (DSA) offers an appealing approach to functional
imaging in small animals because of the high spatial and
temporal resolution, and the ability to visualize and
measure blood flow. The micro-injector described here meets
crucial performance parameters to ensure optimal vessel
enhancement without significantly increasing the total blood
volume or producing overlap of enhanced structures. The
micro-injector can inject small, reproducible volumes of
contrast agent at high flow rates with computer-controlled
timing synchronized to cardiopulmonary activity. Iterative
bench-top and live animal experiments with both rat and
mouse have been conducted to evaluate the performance of
this computer-controlled micro-injector, a first
demonstration of a new device designed explicitly for the
unique requirements of DSA in small animals. Injection
protocols were optimized and screened for potential
physiological impact. For the optimized protocols, we found
that changes in the time-density curves for representative
regions of interest in the thorax were due primarily to
physiological changes, independent of micro-injector
parameters.},
Key = {fds157083}
}
@article{fds157100,
Author = {NN Mistry and J Pollaro and J Song and M De Lin and GA
Johnson},
Title = {Pulmonary perfusion imaging in the rodent lung using dynamic
contrast-enhanced MRI.},
Journal = {Magnetic resonance in medicine : official journal of the
Society of Magnetic Resonance in Medicine / Society of
Magnetic Resonance in Medicine, United States},
Volume = {59},
Number = {2},
Pages = {289-97},
Year = {2008},
Month = {February},
ISSN = {0740-3194},
Keywords = {Animals Contrast Media Female Gadolinium DTPA Image
Processing, Computer-Assisted Lung Magnetic Resonance
Imaging Phantoms, Imaging Rats Rats, Inbred F344 blood
supply* methods* pharmacokinetics*},
Abstract = {With the development of various models of pulmonary disease,
there is tremendous interest in quantitative regional
assessment of pulmonary function. While ventilation imaging
has been addressed to a certain extent, perfusion imaging
for small animals has not kept pace. In humans and large
animals perfusion can be assessed using dynamic
contrast-enhanced (DCE) MRI with a single bolus injection of
a gadolinium (Gd)-based contrast agent. But the method
developed for the clinic cannot be translated directly to
image the rodent due to the combined requirements of higher
spatial and temporal resolution. This work describes a novel
image acquisition technique staggered over multiple,
repeatable bolus injections of contrast agent using an
automated microinjector, synchronized with image acquisition
to achieve dynamic first-pass contrast enhancement in the
rat lung. This allows dynamic first-pass imaging that can be
used to quantify pulmonary perfusion. Further improvements
are made in the spatial and temporal resolution by combining
the multiple injection acquisition method with Interleaved
Radial Imaging and "Sliding window-keyhole" reconstruction
(IRIS). The results demonstrate a simultaneous increase in
spatial resolution (<200 mum) and temporal resolution (<200
ms) over previous methods, with a limited loss in
signal-to-noise-ratio.},
Key = {fds157100}
}
@article{fds157093,
Author = {AA Sharief and A Badea and AM Dale and GA Johnson},
Title = {Automated segmentation of the actively stained mouse brain
using multi-spectral MR microscopy.},
Journal = {NeuroImage, United States},
Volume = {39},
Number = {1},
Pages = {136-45},
Year = {2008},
Month = {January},
ISSN = {1053-8119},
Keywords = {Algorithms Animals Artificial Intelligence* Brain Image
Enhancement Image Interpretation, Computer-Assisted Magnetic
Resonance Imaging Male Mice Mice, Inbred C57BL Microscopy
Pattern Recognition, Automated Reproducibility of Results
Sensitivity and Specificity Staining and Labeling
Subtraction Technique cytology* methods methods*},
Abstract = {Magnetic resonance microscopy (MRM) has created new
approaches for high-throughput morphological phenotyping of
mouse models of diseases. Transgenic and knockout mice serve
as a test bed for validating hypotheses that link genotype
to the phenotype of diseases, as well as developing and
tracking treatments. We describe here a Markov random fields
based segmentation of the actively stained mouse brain, as a
prerequisite for morphological phenotyping. Active staining
achieves higher signal to noise ratio (SNR) thereby enabling
higher resolution imaging per unit time than obtained in
previous formalin-fixed mouse brain studies. The
segmentation algorithm was trained on isotropic 43-mum T1-
and T2-weighted MRM images. The mouse brain was segmented
into 33 structures, including the hippocampus, amygdala,
hypothalamus, thalamus, as well as fiber tracts and
ventricles. Probabilistic information used in the
segmentation consisted of (a) intensity distributions in the
T1- and T2-weighted data, (b) location, and (c) contextual
priors for incorporating spatial information. Validation
using standard morphometric indices showed excellent
consistency between automatically and manually segmented
data. The algorithm has been tested on the widely used
C57BL/6J strain, as well as on a selection of six
recombinant inbred BXD strains, chosen especially for their
largely variant hippocampus.},
Key = {fds157093}
}
@booklet{Segars04,
Author = {W. P. Segars and B. M. W. Tsui and E. C. Frey and G. A.
Johnson and S. S. Berr},
Title = {Development of a 4-D digital mouse phantom for molecular
imaging research},
Journal = {Molecular Imaging And Biology},
Volume = {6},
Number = {3},
Pages = {149 -- 159},
Year = {2004},
Key = {Segars04}
}
@booklet{Hoverstad04,
Author = {T. R. Hoverstad and J. L. Gunsolus and G. A. Johnson and R.
R. King},
Title = {Risk-efficiency criteria for evaluating economics of
herbicide-based weed management systems in
corn},
Journal = {Weed Technology},
Volume = {18},
Number = {3},
Pages = {687 -- 697},
Year = {2004},
Key = {Hoverstad04}
}
@booklet{Sills04,
Author = {R. C. Sills and D. L. Morgan and D. W. Herr and P. B. Little and N. M. George and T. V. Ton and N. E. Love and R. R.
Maronpot and G. A. Johnson},
Title = {Contribution of magnetic resonance microscopy in the 12-week
neurotoxicity evaluation of carbonyl sulfide in Fischer 344
rats},
Journal = {Toxicologic Pathology},
Volume = {32},
Number = {5},
Pages = {501 -- 510},
Year = {2004},
Key = {Sills04}
}
@booklet{Fischer04,
Author = {D. W. Fischer and R. G. Harvey and T. T. Bauman and S.
Phillips and S. E. Hart and G. A. Johnson and J. J. Kells and P. Westra and J. Lindquist},
Title = {Common lambsquarters (Chenopodium album) interference with
corn across the northcentral United States},
Journal = {Weed Science},
Volume = {52},
Number = {6},
Pages = {1034 -- 1038},
Year = {2004},
Key = {Fischer04}
}
@booklet{Johnson02b,
Author = {G. A. Johnson and T. R. Hoverstad},
Title = {Effect of row spacing and herbicide application timing on
weed control and grain yield in corn (Zea
mays)},
Journal = {Weed Technology},
Volume = {16},
Number = {3},
Pages = {548 -- 553},
Year = {2002},
Key = {Johnson02b}
}
@booklet{Jefferies01,
Author = {B. Jefferies and G. A. Johnson},
Title = {Feynman's operational calculi for noncommuting operators:
Definitions and elementary properties},
Journal = {Russian Journal Of Mathematical Physics},
Volume = {8},
Number = {2},
Pages = {153 -- 171},
Year = {2001},
Key = {Jefferies01}
}
@booklet{Walsh01,
Author = {B. Walsh and G. A. Johnson},
Title = {Validation: Never an endpoint: A systems development life
cycle approach to good clinical practice},
Journal = {Drug Information Journal},
Volume = {35},
Number = {3},
Pages = {809 -- 817},
Year = {2001},
Key = {Walsh01}
}
@booklet{Lester00,
Author = {D. S. Lester and P. S. Pine and M. Delnomdedieu and J. N.
Johannessen and G. A. Johnson},
Title = {Virtual neuropathology: Three-dimensional visualization of
lesions due to toxic insult},
Journal = {Toxicologic Pathology},
Volume = {28},
Number = {1},
Pages = {100 -- 104},
Year = {2000},
Key = {Lester00}
}
@booklet{Wang00,
Author = {G. Y. Wang and G. A. Johnson and T. E. Spencer and F. W.
Bazer},
Title = {Isolation, immortalization, and initial characterization of
uterine cell lines: An in vitro model system for the porcine
uterus},
Journal = {In Vitro Cellular \& Developmental Biology-animal},
Volume = {36},
Number = {10},
Pages = {650 -- 656},
Year = {2000},
Key = {Wang00}
}
@booklet{Colbach00,
Author = {N. Colbach and F. Forcella and G. A. Johnson},
Title = {Spatial and temporal stability of weed populations over five
years},
Journal = {Weed Science},
Volume = {48},
Number = {3},
Pages = {366 -- 377},
Year = {2000},
Key = {Colbach00}
}
@booklet{Stahl99,
Author = {L. A. B. Stahl and G. A. Johnson and D. L. Wyse and D. D.
Buhler and J. L. Gunsolus},
Title = {Effect of tillage on timing of Setaria spp. emergence and
growth},
Journal = {Weed Science},
Volume = {47},
Number = {5},
Pages = {563 -- 570},
Year = {1999},
Key = {Stahl99}
}
@booklet{Benveniste99a,
Author = {H. Benveniste and H. Qui and L. W. Hedlund and P. C.
Huttemeier and S. M. Steele and G. A. Johnson},
Title = {In vivo diffusion-weighted magnetic resonance microscopy of
rat spinal cord: Effect of ischemia and intrathecal
hyperbaric 5\% lidocaine},
Journal = {Regional Anesthesia And Pain Medicine},
Volume = {24},
Number = {4},
Pages = {311 -- 318},
Year = {1999},
Key = {Benveniste99a}
}
@booklet{Smith99,
Author = {B. R. Smith and D. S. Huff and G. A. Johnson},
Title = {Magnetic resonance imaging of embryos: an Internet resource
for the study of embryonic development},
Journal = {Computerized Medical Imaging And Graphics},
Volume = {23},
Number = {1},
Pages = {33 -- 40},
Year = {1999},
Key = {Smith99}
}
@booklet{Johnson98d,
Author = {G. A. Johnson and T. R. Hoverstad and R. E.
Greenwald},
Title = {Integrated weed management using narrow corn row spacing,
herbicides, and cultivation},
Journal = {Agronomy Journal},
Volume = {90},
Number = {1},
Pages = {40 -- 46},
Year = {1998},
Key = {Johnson98d}
}
@booklet{Lindquist98,
Author = {J. L. Lindquist and J. A. Dieleman and D. A. Mortensen and G. A. Johnson and D. Y. Wyse-pester},
Title = {Economic importance of managing spatially heterogeneous weed
populations},
Journal = {Weed Technology},
Volume = {12},
Number = {1},
Pages = {7 -- 13},
Year = {1998},
Key = {Lindquist98}
}
@booklet{Griffin98,
Author = {W. P. Griffin and E. B. Savage and R. E. Clark and J. J.
Pacella and G. A. Johnson and J. A. Magovern and G. J.
Magovern},
Title = {AB-180 circulatory support system - Summary of development
and phase I clinical trial},
Journal = {Asaio Journal},
Volume = {44},
Number = {5},
Pages = {M719 -- M724},
Year = {1998},
Key = {Griffin98}
}
@booklet{Benveniste98,
Author = {H. Benveniste and H. Qui and L. W. Hedlund and F. D'ercole and G. A. Johnson},
Title = {Spinal cord neural anatomy in rats examined by in vivo
magnetic resonance microscopy},
Journal = {Regional Anesthesia And Pain Medicine},
Volume = {23},
Number = {6},
Pages = {589 -- 599},
Year = {1998},
Key = {Benveniste98}
}
@booklet{Cardina97,
Author = {J. Cardina and G. A. Johnson and D. H. Sparrow},
Title = {The nature and consequence of weed spatial
distribution},
Journal = {Weed Science},
Volume = {45},
Number = {3},
Pages = {364 -- 373},
Year = {1997},
Key = {Cardina97}
}
@booklet{Gerhards97,
Author = {R. Gerhards and D. Y. Wysepester and D. Mortensen and G. A.
Johnson},
Title = {Characterizing spatial stability of weed populations using
interpolated maps},
Journal = {Weed Science},
Volume = {45},
Number = {1},
Pages = {108 -- 119},
Year = {1997},
Key = {Gerhards97}
}
@booklet{Qiu97a,
Author = {H. Qiu and L. W. Hedlund and S. L. Gewalt and H. Benveniste and T. M. Bare and G. A. Johnson},
Title = {Progression of a focal ischemic lesion in rat brain during
treatment with a novel glycine/NMDA antagonist: An in vivo
three-dimensional diffusion-weighted MR microscopy
study},
Journal = {Jmri-journal Of Magnetic Resonance Imaging},
Volume = {7},
Number = {4},
Pages = {739 -- 744},
Year = {1997},
Key = {Qiu97a}
}
@booklet{Delnomdedieu96,
Author = {M. Delnomdedieu and L. W. Hedlund and G. A. Johnson and R.
R. Maronpot},
Title = {Magnetic resonance microscopy - A new tool for the
toxicologic pathologist},
Journal = {Toxicologic Pathology},
Volume = {24},
Number = {1},
Pages = {36 -- 44},
Year = {1996},
Key = {Delnomdedieu96}
}
@booklet{Johnson96c,
Author = {G. A. Johnson and D. A. Mortensen and C. A.
Gotway},
Title = {Spatial and temporal analysis of weed seedling populations
using geostatistics},
Journal = {Weed Science},
Volume = {44},
Number = {3},
Pages = {704 -- 710},
Year = {1996},
Key = {Johnson96c}
}
@booklet{Johnson96b,
Author = {G. A. Johnson and D. A. Mortensen and L. J. Young and A. R.
Martin},
Title = {Parametric sequential sampling based on multistage
estimation of the negative binomial parameter
k},
Journal = {Weed Science},
Volume = {44},
Number = {3},
Pages = {555 -- 559},
Year = {1996},
Key = {Johnson96b}
}
@booklet{Burvill96,
Author = {P. W. Burvill and G. A. Johnson and T. M. H. Chakera and E.
G. Stewartwynne and C. S. Anderson and K. D.
Jamrozik},
Title = {The place of site of lesion in the aetiology of post-stroke
depression},
Journal = {Cerebrovascular Diseases},
Volume = {6},
Number = {4},
Pages = {208 -- 215},
Year = {1996},
Key = {Burvill96}
}
@booklet{Smith96,
Author = {B. R. Smith and E. Linney and D. S. Huff and G. A.
Johnson},
Title = {Magnetic resonance microscopy of embryos},
Journal = {Computerized Medical Imaging And Graphics},
Volume = {20},
Number = {6},
Pages = {483 -- 490},
Year = {1996},
Key = {Smith96}
}
@booklet{Johnson95,
Author = {G. A. Johnson and D. A. Mortensen and L. J. Young and A. R.
Martin},
Title = {The stability of weed seedling population-models and
parameters in eastern nebraska corn (zea-mays) and soybean
(glycine-max) fields},
Journal = {Weed Science},
Volume = {43},
Number = {4},
Pages = {604 -- 611},
Year = {1995},
Key = {Johnson95}
}
@booklet{Baker94,
Author = {C. A. Baker and H. Uno and G. A. Johnson},
Title = {Minoxidil sulfation in the hair follicle},
Journal = {Skin Pharmacology},
Volume = {7},
Number = {6},
Pages = {335 -- 339},
Year = {1994},
Key = {Baker94}
}
@booklet{Nielsen94,
Author = {C. H. Nielsen and G. A. Johnson},
Title = {The experience of complete neuromuscular blockade in awake
patients},
Journal = {Journal Of Clinical Anesthesia},
Volume = {6},
Number = {5},
Pages = {450 -- 450},
Year = {1994},
Key = {Nielsen94}
}
@booklet{Johnson93a,
Author = {G. A. Johnson and M. S. Defelice and Z. R.
Helsel},
Title = {Cover crop management and weed-control in corn
(zea-mays)},
Journal = {Weed Technology},
Volume = {7},
Number = {2},
Pages = {425 -- 430},
Year = {1993},
Key = {Johnson93a}
}
@booklet{Zhou93,
Author = {X. H. Zhou and Z. P. Liang and G. P. Cofer and C. F.
Beaulieu and S. A. Suddarth and G. A. Johnson},
Title = {Reduction of ringing and blurring artifacts in fast
spin-echo imaging},
Journal = {Jmri-journal Of Magnetic Resonance Imaging},
Volume = {3},
Number = {5},
Pages = {803 -- 807},
Year = {1993},
Key = {Zhou93}
}
@booklet{Smith92,
Author = {B. R. Smith and E. L. Effmann and G. A. Johnson},
Title = {Mr microscopy of chick-embryo vasculature},
Journal = {Jmri-journal Of Magnetic Resonance Imaging},
Volume = {2},
Number = {2},
Pages = {237 -- 240},
Year = {1992},
Key = {Smith92}
}
@booklet{Banson92,
Author = {M. L. Banson and G. P. Cofer and L. W. Hedlund and G. A.
Johnson},
Title = {Surface coil imaging of rat spine at 7.0-t},
Journal = {Magnetic Resonance Imaging},
Volume = {10},
Number = {6},
Pages = {929 -- 934},
Year = {1992},
Key = {Banson92}
}
@booklet{Malisch91,
Author = {T. W. Malisch and L. W. Hedlund and S. A. Suddarth and G. A.
Johnson},
Title = {Mr microscopy at 7.0 t - effects of brain
iron},
Journal = {Jmri-journal Of Magnetic Resonance Imaging},
Volume = {1},
Number = {3},
Pages = {301 -- 305},
Year = {1991},
Key = {Malisch91}
}
@booklet{Maki91,
Author = {J. H. Maki and H. Benveniste and J. R. Macfall and C. A.
Piantadosi and G. A. Johnson},
Title = {Mr imaging of microcirculation in rat-brain - correlation
with carbon-dioxide - induced changes in
blood-flow},
Journal = {Jmri-journal Of Magnetic Resonance Imaging},
Volume = {1},
Number = {6},
Pages = {673 -- 681},
Year = {1991},
Key = {Maki91}
}
@booklet{Maki91a,
Author = {J. H. Maki and H. Benveniste and J. R. Macfall and G. A.
Johnson},
Title = {Maximization of contrast-to-noise ratio to distinguish
diffusion and microcirculatory flow},
Journal = {Jmri-journal Of Magnetic Resonance Imaging},
Volume = {1},
Number = {1},
Pages = {39 -- 46},
Year = {1991},
Key = {Maki91a}
}
@booklet{Cline89,
Author = {H. E. Cline and W. E. Lorensen and R. J. Herfkens and G. A.
Johnson and G. H. Glover},
Title = {Vascular morphology by 3-dimensional magnetic-resonance
imaging},
Journal = {Magnetic Resonance Imaging},
Volume = {7},
Number = {1},
Pages = {45 -- 54},
Year = {1989},
Key = {Cline89}
}
@booklet{Johnson87c,
Author = {G. A. Johnson},
Title = {Resolution limits in mr - mr microscopy},
Journal = {Medical Physics},
Volume = {14},
Number = {3},
Pages = {499 -- 499},
Year = {1987},
Key = {Johnson87c}
}
@booklet{Suddarth87,
Author = {S. A. Suddarth and G. A. Johnson and R. H. Sherrier and C.
E. Ravin},
Title = {Performance of high-resolution monitors for digital chest
imaging},
Journal = {Medical Physics},
Volume = {14},
Number = {2},
Pages = {253 -- 257},
Year = {1987},
Key = {Suddarth87}
}
@booklet{Brown87,
Author = {J. M. Brown and W. C. Fonteno and D. K. Cassel and G. A.
Johnson},
Title = {Computed tomographic analyses of water distribution in 3
porous foam media},
Journal = {Soil Science Society Of America Journal},
Volume = {51},
Number = {5},
Pages = {1121 -- 1125},
Year = {1987},
Key = {Brown87}
}
@booklet{Drayer86b,
Author = {B. Drayer and P. Burger and J. Cain and J. Leong and G. A.
Johnson and E. R. Heinz and S. Riederer and W. Djang and R.
Herfkens},
Title = {Mr imaging and perls stain of basal ganglia iron with normal
aging},
Journal = {American Journal Of Neuroradiology},
Volume = {7},
Number = {3},
Pages = {554 -- 555},
Year = {1986},
Key = {Drayer86b}
}
@booklet{Drayer86a,
Author = {B. Drayer and P. Burger and R. Darwin and S. Riederer and R.
Herfkens and G. A. Johnson},
Title = {Magnetic-resonance-imaging of brain iron},
Journal = {American Journal Of Neuroradiology},
Volume = {7},
Number = {3},
Pages = {373 -- 380},
Year = {1986},
Key = {Drayer86a}
}
@booklet{Hedlund86,
Author = {L. W. Hedlund and G. A. Johnson and J. P. Karis and E. L.
Effmann},
Title = {Mr microscopy of the rat thorax},
Journal = {Journal Of Computer Assisted Tomography},
Volume = {10},
Number = {6},
Pages = {948 -- 952},
Year = {1986},
Key = {Hedlund86}
}
@article{9082523,
Author = {Oldham, M. and Sakhalkar, H. and Oliver, T. and Ying Min
Wang and Kirpatrick, J. and Yiting Cao and Badea, C. and Johnson, G.A. and Dewhirst, M.},
Title = {Three-dimensional imaging of xenograft tumors using optical
computed and emission tomography},
Journal = {Med. Phys. (USA)},
Volume = {33},
Number = {9},
Pages = {3193 - 202},
url = {http://dx.doi.org/10.1118/1.2217109},
Keywords = {bio-optics;biomedical optical imaging;cancer;cellular
biophysics;computerised tomography;image
reconstruction;proteins;tumours;},
Abstract = {The physical basis and preliminary applications of optical
computed tomography (optical-CT) and optical emission
computed tomography (optical-ECT) are introduced, as new
techniques with potential to provide unique 3D information
on a variety of aspects of tumor structure and function. A
particular focus here is imaging tumor micro-vasculature,
and the spatial distribution of viable tumor cells, although
the techniques have the potential for much wider
application. The principle attractiveness of optical-CT and
optical-ECT are that high resolution (<20 μm) and high
contrast co-registered 3D images of structure and function
can be acquired for relatively large intact samples. The
unique combination of high contrast and resolution offers
advantages over micro-CT and micro-MRI, and the lack of
requirement for sectioning offers advantages over confocal
microscopy, conventional microscopy, and histological
sectioning techniques. Optical-CT/ECT are implemented using
in-house custom apparatus and a commercial dissecting
microscope capable of both transmission and fluorescence
imaging. Basic studies to characterize imaging performance
are presented. Negligible geometrical distortion and
accurate reconstruction of relative attenuation coefficients
was observed. Optical-CT and optical-ECT are investigated
here by application to high resolution imaging of HCT116
xenograft tumors, about 1 cc in dimension, which were
transfected with constitutive red fluorescent protein (RFP).
Tumor microvasculature was stained in vivo by tail vein
injection of either passive absorbing dyes or active
fluorescent markers (FITC conjugated lectin). Prior to
imaging, the tumors were removed (ex vivo) and optically
cleared in a key process to make the samples amenable to
light transmission. The cleared tumors were imaged in three
modes (i) optical-CT to image the 3D distribution of
microvasculature as indicated by absorbing dye, (ii)
optical-ECT using the FITC excitation and emission filter
set, to determine microvasculature as indicated by
lectin-endothelial binding, and (iii) optical-ECT using the
DSRed2 filter set to determine the 3D distribution of viable
tumor as indicated by RFP emission. A clear correlation was
observed between the independent vasculature imaging modes
(i) and (ii) and postimaging histological sections,
providing substantial validation of the optical-CT and
optical-ECT techniques. Strong correlation was also observed
between the RFP imaging of mode iii, and modes i and ii,
supporting the intuitive conclusion that well-perfused
regions contain significant viable tumor. In summary,
optical-CT and optical-ECT, when combined with new optical
clearing techniques, represent powerful new imaging
modalities with potential for providing unique information
on the structure and function of tumors},
Key = {9082523}
}
%% Katz, David F
@booklet{Gupta09,
Author = {K. M. Gupta and S. R. Barnes and R. A. Tangaro and M. C.
Roberts and D. H. Owen and D. F. Katz and P. F.
Kiser},
Title = {Temperature and pH Sensitive Hydrogels: An Approach Towards
Smart Semen-Triggered Vaginal Microbicidal Vehicles (vol 96,
pg 670, 2007)},
Journal = {Journal Of Pharmaceutical Sciences},
Volume = {98},
Number = {3},
Pages = {1198 -- 1198},
Year = {2009},
Month = {March},
ISSN = {0022-3549},
Key = {Gupta09}
}
@booklet{Szeri08,
Author = {A. J. Szeri and S. C. Park and S. Verguet and A. Weiss and D. F. Katz},
Title = {A model of transluminal flow of an anti-HIV microbicide
vehicle: Combined elastic squeezing and gravitational
sliding},
Journal = {Physics Of Fluids},
Volume = {20},
Number = {8},
Year = {2008},
Month = {August},
ISSN = {1070-6631},
Abstract = {Elastohydrodynamic lubrication over soft substrates is of
importance in a number of biomedical problems: From
lubrication of the eye surface by the tear film, to
lubrication of joints by synovial fluid, to lubrication
between the pleural surfaces that protect the lungs and
other organs. Such flows are also important for the drug
delivery functions of vehicles for anti-HIV topical
microbicides. These are intended to inhibit transmission
into vulnerable mucosa, e.g., in the vagina. First spread
after insertion and coat luminal generation prototype
microbicides have gel vehicles, which spread surfaces.
Effectiveness derives from potency of the active ingredients
and completeness and durability of coating. Delivery vehicle
rheology, luminal biomechanical properties, and the force
due to gravity influence the coating mechanics. We develop a
framework for understanding the relative importance of
boundary squeezing and body forces on the extent and speed
of the coating that results. A single dimensionless number,
independent of viscosity, characterizes the relative
influences of squeezing and gravitational acceleration on
the shape of spreading in the Newtonian case. A second
scale, involving viscosity, determines the spreading rate.
In the case of a shear-thinning fluid, the Carreau number
also plays a role. Numerical solutions were developed for a
range of the dimensionless parameter and compared well with
asymptotic theory in the limited case where such results can
be obtained. Results were interpreted with respect to
trade-offs between wall elasticity, longitudinal forces,
bolus viscosity, and bolus volume. These provide initial
insights of practical value for formulators of gel delivery
vehicles for anti-HIV microbicidal formulations. (C) 2008
American Institute of Physics.},
Key = {Szeri08}
}
@booklet{Lai08,
Author = {B. E. Lai and Y. Q. Xie and M. L. Lavine and A. J. Szeri and D. H. Owen and D. F. Katz},
Title = {Dilution of microbicide gels with vaginal fluid and semen
simulants: Effect on rheological properties and coating
flow},
Journal = {Journal Of Pharmaceutical Sciences},
Volume = {97},
Number = {2},
Pages = {1030 -- 1038},
Year = {2008},
Month = {February},
ISSN = {0022-3549},
Abstract = {Microbicides are agents applied topically to the vagina to
prevent HIV transmission. Microbicide products formulated as
semi-solid dosage forms or '' gels '' coat vulnerable tissue
to deliver active ingredients. Effective microbicide
delivery vehicles must have appropriate rheological
properties to ensure appropriate deployment in vivo.
Microbicide products become diluted by fluids in the vagina
after application; dilution affects vehicle rheological
properties and mechanics of vaginal distribution, thus
affecting efficacy. To simulate the changes that might occur
after application, this study analyzed the effects of small
dilutions (10 - 30\%) with vaginal fluid and semen simulants
on three semi-solid vaginal formulations: a cellulose
lubricant (KY Jelly), a polyacrylic acid moisturizer
(Replens), and a carrageenan prototype microbicide
(Carraguard). Rheological behavior was characterized using
cone-and-plate rheometry. Data were fitted to either the
power-law, Carreau, or Herschel - Bulkley model. Rheological
parameters from these fits were input to models of coating
flow due squeezing, and the simulated area coated output
from these models was used to compare the responses of the
different formulations to the two diluents for varying
degrees of dilution. There were differences in the responses
of the three materials to dilution. Even small dilutions
altered the rank order of vaginal coating rates compared to
the undiluted formulations. (c) 2007 Wiley-Liss,
Inc.},
Key = {Lai08}
}
@booklet{Braun06,
Author = {K. E. Braun and J. D. Boyer and M. H. Henderson and D. F.
Katz and A. Wax},
Title = {Label-free measurement of microbicidal gel thickness using
low-coherence interferometry},
Journal = {Journal Of Biomedical Optics},
Volume = {11},
Number = {2},
Year = {2006},
ISSN = {1083-3668},
Abstract = {Spectral-domain low-coherence interferometry (LCI) was used
to measure the thickness of microbicidal gels applied to a
cylindrical calibration test socket. Microbicides are
topical formulations containing active ingredients targeted
to inhibit specific pathogens that are currently under
development for application to the epithelial lining of the
lower female reproductive tract to combat sexually
transmitted infections such as HIV. Understanding the
deployment and drug delivery of these formulations is vital
to maximizing their effectiveness. Previously, in vivo
measurements of microbicidal formulation thickness were
assessed using fluorescence measurements of
fluorescein-labeled gels via an optical endoscope-based
device. Here we present an LCI-based device that measures
the thickness of a formulation without the use of any
exogenous agents by analyzing the interference pattern
generated between the reflections from the front and back
surface of the sample. Results are presented that validate
the effectiveness and performance of the LCI measurement in
a clinically relevant system as compared to an existing
fluorescence-based method. The impact of the new LCI-based
design on in vivo measurements is discussed. (c) 2006
Society of Photo-Optical Instrumentation
Engineers.},
Key = {Braun06}
}
@booklet{Owen05,
Author = {D. H. Owen and D. F. Katz},
Title = {A review of the physical and chemical properties of human
semen and the formulation of a semen simulant},
Journal = {Journal Of Andrology},
Volume = {26},
Number = {4},
Pages = {459 -- 469},
Year = {2005},
ISSN = {0196-3635},
Abstract = {A fluid medium was developed to simulate the salient
physical and chemical properties of human semen. The
composition of the medium was based upon an extensive review
of the literature on constituents of human semen. In
choosing the ingredients for this medium, the goal was to
emphasize properties that influence interactions of human
semen with topical contraceptive, prophylactic, or
therapeutic products. Among these properties, pH and
buffering capacity, osmolarity, ionic strength, and
rheological properties play dominant roles in the
physico-chemical processes that govern drug release kinetics
and delivery vehicle distribution.},
Key = {Owen05}
}
@booklet{Amann04,
Author = {R. P. Amann and D. F. Katz},
Title = {Reflections on CASA after 25 years},
Journal = {Journal Of Andrology},
Volume = {25},
Number = {3},
Pages = {317 -- 325},
Year = {2004},
ISSN = {0196-3635},
Key = {Amann04}
}
@booklet{Fulford98,
Author = {G. R. Fulford and D. F. Katz and R. L. Powell},
Title = {Swimming of spermatozoa in a linear viscoelastic
fluid},
Journal = {Biorheology},
Volume = {35},
Number = {4-5},
Pages = {295 -- 309},
Year = {1998},
ISSN = {0006-355X},
Abstract = {A modified resistive force theory is developed for a
spermatozoon swimming in a general linear viscoelastic
fluid. The theory is based on a Fourier decomposition of the
flagellar velocity, which leads to solving the Stokes flow
equations with a complex viscosity. We use a model
spermatozoon with a spherical head which propagates small
amplitude sinusoidal waves along its flagellum. Results are
obtained for the velocity of propulsion and the rate of
working for a free swimming spermatozoon and the thrust on a
fixed spermatozoon. There is no change in propulsive
velocity for a viscoelastic fluid compared to a Newtonian
fluid. The rate of working does change however, decreasing
with increasing elasticity of the fluid, for a Maxwell
fluid. Thus the theory predicts that a spermatozoon can swim
faster in a Maxwell fluid with the same expenditure of
energy for a Newtonian fluid.},
Key = {Fulford98}
}
@booklet{Katz97,
Author = {D. F. Katz and D. A. Slade and S. T. Nakajima},
Title = {Analysis of pre-ovulatory changes in cervical mucus
hydration and sperm penetrability},
Journal = {Advances In Contraception},
Volume = {13},
Number = {2-3},
Pages = {143 -- 151},
Year = {1997},
ISSN = {0267-4874},
Abstract = {Changes in cervical mucus occur during the proliferative
phase of the menstrual cycle and are known to correlate with
receptivity to sperm and to the endocrine milieu. Prior
studies, however, have often lacked biological incisiveness
and technical objectivity and precision. This study analyzed
daily changes in mucus water content (hydration) prior to
the LH surge (LH+0) in normal women, in relation to daily
levels of serum LH, FSH, estradiol and progesterone, and to
daily tests of sperm penetration of the mucus. Cervical
mucus was studied for 12 cycles in 10 ovulating women. Three
to ten mucus specimens were collected per cycle, over the
days LH-8 to LH+0. Each specimen was subjected to
measurement of both water content (hydration) and
penetration by spermatozoa from fresh specimens of normal
human semen. For the latter, a new microscale assay was
developed and applied, which was amenable to very small
volumes of mucus. The new technique determines objective
measures of both the numbers of penetrating sperm (motile
and non-motile) and the distance penetrated by the
forwardmost vanguard sperm. In these experiments, variations
in semen quality were controlled by performing a companion
penetration assay in an artificial 1.5\% polyacrylamide gel.
The patterns of change in mucus hydration varied
quantitatively among women, with preovulatory baseline
levels ranging from 93.8-96.5\%. All normal cycles (as
defined by endocrine profiles) displayed a significant
increase in hydration over a one-day period occurring 3-4
days before the LH peak. The magnitude of this shift varied
among women between 2 and 3\% (absolute hydration), a
distinction well within the precision of the hydration
assay. This quantum increase in hydration was more
pronounced than the corresponding increase in serum
estradiol on the same day. The change in mucus hydration,
and the associated increase in sperm penetrability, were
more consistent among cycles than the changes in
reproductive hormones. There was a strong but non-linear
correlation between mucus hydration and sperm penetrability.
Once the value of hydration rose above approximately 97.5\%,
there was a substantial increase in penetrability. This
'cut-off point' in sperm penetrability was in the middle of
the range of hydration values (across women) which preceded
the quantum jump in hydration - which, itself, preceded the
surge of LH. Hydration began to increase approximately 2
days before measurable increases in sperm penetration of the
mucus in vitro. These results demonstrate that mucus
hydration may be a valuable marker of the approach to
ovulation and delineation of the fertile period. They also
provide new methods for assessing sperm penetration into
both large periovulatory and very small samples of collected
mucus.},
Key = {Katz97}
}
@booklet{Fenster97,
Author = {L. Fenster and D. F. Katz and A. J. Wyrobek and C. Pieper and D. M. Rempel and D. Oman and S. H. Swan},
Title = {Effects of psychological stress on human semen
quality},
Journal = {Journal Of Andrology},
Volume = {18},
Number = {2},
Pages = {194 -- 202},
Year = {1997},
ISSN = {0196-3635},
Abstract = {We investigated the relationship between psychological
stress and sperm concentration, motility, and morphometry in
a prospective study of 157 volunteers who were enrolled in a
prepaid health plan. We measured psychological job stress
and life-event stress by telephone interview.
Sperm-kinematic and nuclear-morphometric variables were
measured using computer-assisted image analyses. Sperm
concentration, percent motility, and semen volume were
determined by objective visual methods. We performed
multiple linear regression for each semen variable to
examine its relationship to stress, controlling for
potential confounders. Stress at work and total number of
life events were not related to differences in semen
quality. However, the recent death of a close family member
was associated with a reduction in straight-line velocity (P
= 0.002) and percent of progressively motile sperm (P =
0.02); it was also marginally associated with an increase in
the fraction of sperm with larger and more tapered nuclei.
These findings suggest that the fecundity of men
experiencing the stress of a family member's death might be
temporarily diminished.},
Key = {Fenster97}
}
@booklet{Wyrobek97,
Author = {A. J. Wyrobek and S. M. Schrader and S. D. Perreault and L.
Fenster and G. Huszar and D. F. Katz and A. M. Osorio and V.
Sublet and D. Evenson},
Title = {Assessment of reproductive disorders and birth defects in
communities near hazardous chemical sites .3. Guidelines for
field studies of male reproductive disorders},
Journal = {Reproductive Toxicology},
Volume = {11},
Number = {2-3},
Pages = {243 -- 259},
Year = {1997},
ISSN = {0890-6238},
Abstract = {Exposures to environmental toxicants can have detrimental
effects on several aspects of human male reproduction:
fertility, sexual function, hormone status, and
pregnancy/birth outcomes. However, no simple prescreening
methods are available for reliably identifying potential
hazards; questionnaires alone are relatively imprecise and
inefficient in the absence of field data. Multidisciplinary
field studies are required that include detailed exposure
information, health and reproductive histories, physical
examinations, semen analyses, and possibly, hormone
analyses. Semen analysis is a critical component of field
studies for evaluating two aspects of male reproduction: 1)
changes in sperm or seminal content, which may be indicative
of adverse effects on the male reproductive system with
possible implications for fertility potential; and 2)
defects in sperm DNA or chromosomes, which may be associated
with subsequent changes in viability during embryonic
development and health risks to the offspring. Semen
analyses may be tiered: 1) initially, each semen study may
include conventional semen assays (concentration, motility,
and morphology) as well as specific biomarkers indicated by
the health effect of concern in the study cohort; and 2)
archived samples (i.e., frozen, videotaped, or smeared) mag
be utilized in later second-tier analyses to further
characterize specific findings. Before initiating any field
study, it is cost effective to critically evaluate the
suitability of the cohort by confirming exposure and
determining that there are adequate numbers of male
participants in each exposure category. Such evaluations
must be based on the statistical sensitivities of the
specific tissue biomarkers and health endpoints for
detecting changes. This article summarizes the components of
the ideal field study and identifies research needs for
improving field studies of mate effects and for
understanding the mechanisms of male reproductive toxicity.
Several promising semen methods currently under development
are also discussed. (C) 1997 Elsevier Science
Inc.},
Key = {Wyrobek97}
}
%% Klitzman, Bruce M
@article{fds148452,
Author = {HL Prichard and W Reichert and B Klitzman},
Title = {IFATS Series: Adipose-Derived Stromal Cells Improve The
Foreign Body Response.},
Journal = {Stem cells (Dayton, Ohio)},
Year = {2008},
Month = {April},
ISSN = {1549-4918},
Abstract = {Many implanted devices fail due to the formation of an
avascular capsule surrounding the device. Additionally, fat
has long been known to promote healing and vascularization.
The goals of this study were to identify potential
mechanisms of the provascular actions of adipose-derived
stromal cells (ASCs) and to improve implant
biocompatibility. First, adult ASCs and fibroblasts from
rats were attached to polyurethane and polystyrene in vitro
and their cytokine secretion profile was analyzed. Secretion
of VEGF from ASCs was 10-70 times higher than fibroblasts
after three and six days. Next, polyurethane, bare and with
cellular coatings, was implanted subcutaneously in rats. The
fibrous capsule surrounding bare polyurethane implants was
17-32% thicker and the amount of collagen was 27% greater
than the capsule surrounding ASC coated implants. Finally,
the microvessel density adjacent to ASC coated polyurethane
was approximately 50-80% higher than bare polyurethane. In
summary, ASCs attached to polyurethane have a dramatically
increased VEGF production compared to fibroblasts in vitro,
and these cells also produce an increased microvessel
density in the surrounding tissue when implanted
subcutaneously in rats.},
Key = {fds148452}
}
@article{fds148453,
Author = {HE Koschwanez and FY Yap and B Klitzman and WM Reichert},
Title = {In vitro and in vivo characterization of porous
poly-L-lactic acid coatings for subcutaneously implanted
glucose sensors.},
Journal = {Journal of biomedical materials research. Part
A},
Year = {2008},
Month = {January},
ISSN = {1552-4965},
Abstract = {The purpose of this study was to test the hypothesis that
porous poly-L-lactic acid (PLLA) sensor coatings reduce
fibrosis and promote blood microvessel formation in tissue
adjacent to the sensor surface. Porous PLLA coatings were
produced using ammonium bicarbonate as the gas foaming/salt
leaching agent, and deployed on functional and nonfunctional
sensors. The porous coatings minimally affected sensor
accuracy and response rate in vitro. Three-week subcutaneous
rat studies of nonfunctional glucose sensors showed the
anticipated effect of porous coatings enhancing vascularity
and decreasing collagen deposition. In contrast,
percutaneous functional sensors with and without porous
coatings showed no significant difference in terms of
histology or sensor response. In spite of the observation
that texturing increases the vascularity of the tissue that
surrounds implanted sensors, other factors such as the
additional mechanical stresses imposed by percutaneous
tethering may override the beneficial effects of the porous
coatings. (c) 2008 Wiley Periodicals, Inc. J Biomed Mater
Res, 2008.},
Key = {fds148453}
}
@article{fds148454,
Author = {SJ Kovach and KE Koger and B Klitzman and G Germann and LS
Levin},
Title = {Advantages of minimally invasive, balloon-dissector-assisted
tissue expander placement: a clinical and experimental
study.},
Journal = {Annals of plastic surgery, United States},
Volume = {60},
Number = {1},
Pages = {89-97},
Year = {2008},
Month = {January},
ISSN = {0148-7043},
Keywords = {Adolescent Adult Animals Child Child, Preschool Endoscopy
Female Humans Male Middle Aged Models, Animal Prosthesis
Implantation Retrospective Studies Swine Tissue Expansion
Tissue Expansion Devices* methods*},
Abstract = {BACKGROUND: Tissue expansion has been dependent upon healing
the access incision after placement. Delay can be reduced
with minimally placed expanders. Smaller, remote incisions
allow for earlier expansion. METHODS: Balloon-assisted
tissue expander placement was evaluated in a pig model and
compared with open placement. Open placement with delayed
expansion versus minimally invasive placement with immediate
expansion, and open placement with immediate expansion
versus balloon dissection with delayed expansion were
compared. Our clinical series with balloon dissector
tissue-expander placement was reviewed. Fifty-two tissue
expanders were placed minimally invasively and successfully
expanded. RESULTS: Use of balloon dissector in the pig model
yielded a shorter reconstructive period, faster expansion,
and greater flap advancement. Clinical results revealed no
infections, dehiscence, extrusion, or hematomas. All cases
had expansion begun intraoperatively and were successfully
expanded. CONCLUSIONS: Minimally invasively placed expanders
resulted in shorter expansion times, the ability to
institute immediate expansion, and improved expansion
compared with open placement.},
Key = {fds148454}
}
%% Laursen, Tod A
@booklet{Stanciulescu07,
Author = {I. Stanciulescu and L. N. Virgin and T. A.
Laursen},
Title = {Slender solar sail booms: Finite element
analysis},
Journal = {Journal Of Spacecraft And Rockets},
Volume = {44},
Number = {3},
Pages = {528 -- 537},
Year = {2007},
ISSN = {0022-4650},
Abstract = {Various aspects related to the numerical (finite element)
analysis of the support structure for solar sails are
analyzed. Static analyses of single booms (simple beam and
isogrid configurations) are presented and dynamic properties
are extracted before and beyond the buckling load. Numerical
difficulties associated with the case of buckling under
nonconservative loading are also explored using as a
reference example von Beck's problem, for which a
closed-form solution for comparison is available. A study of
the entire support structure for a square solar sail (four
connected booms) is also presented. In all analyses,
attention is focused on the prediction of the post-buckling
(large deflection) behavior, including dynamics.},
Key = {Stanciulescu07}
}
%% Leong, Kam W
@booklet{Prow08,
Author = {T. W. Prow and I. Bhutto and S. Y. Kim and R. Grebe and C.
Merges and D. S. Mcleod and K. Uno and M. Mennon and L.
Rodriguez and K. Leong and G. A. Lutty},
Title = {Ocular nanoparticle toxicity and transfection of the retina
and retinal pigment epithelium},
Journal = {Nanomedicine-nanotechnology Biology And Medicine},
Volume = {4},
Number = {4},
Pages = {340 -- 349},
Year = {2008},
Month = {December},
ISSN = {1549-9634},
Abstract = {Chitosan, PCEP (poly$\lbrace$[(cholesteryl oxocarbonylamido
ethyl) methyl bis(ethylene) ammonium iodide] ethyl
phosphate$\rbrace$), and magnetic nanoparticles (MNPs) were
evaluated for the safe delivery of genes in the eye. Rabbits
were injected with nanoparticles either intravitreally (IV)
or subretinally (SR) and sacrificed 7 days later. Eyes were
grossly evaluated for retinal pigment epithelium
abnormalities, retinal degeneration, and inflammation. All
eyes were cryopreserved and sectioned for analysis of
toxicity and expression of either enhanced green or red
fluorescent proteins. All of the nanoparticles were able to
transfect cells in vitro and in vivo. IV chitosan showed
inflammation in 12/13 eyes, whereas IV PCEP and IV MNPs were
not inflammatory and did not induce retinal pathology. SR
PCEP was nontoxic in the majority of cases but yielded poor
transfection, whereas SR MNPs were nontoxic and yielded good
transfection. Therefore, we conclude that the best
nanoparticle evaluated in vivo was the least toxic
nanoparticle tested, the MNP. (c) 2008 Elsevier Inc. All
rights reserved.},
Key = {Prow08}
}
@article{5095818,
Author = {Lu, H. and Leong, K.W. and Cleroux, M. and Puetz,
N.},
Title = {Singlemode operation over range -40-85°C in 1.55 μm
gain-coupled DFB lasers},
Journal = {Electron. Lett. (UK)},
Volume = {31},
Number = {19},
Pages = {1670 - 1},
Year = {14},
url = {http://dx.doi.org/10.1049/el:19951108},
Keywords = {distributed feedback lasers;laser modes;laser
transitions;quantum well lasers;},
Abstract = {Singlemode operation of 1.55 μm gain-coupled DFB lasers
with a large sidemode suppression ratio over a wide
temperature range of -40-85°C is reported. The structure
was based on eight compressively strained multiquantum wells
for high temperature operations and a first-order grating
partially etched into the quantum wells for lasing
wavelength control},
Key = {5095818}
}
@article{7442917,
Author = {Sheeja, D. and Tay, B.K. and Leong, K.W. and Lee,
C.H.},
Title = {Effect of film thickness on the stress and adhesion of
diamond-like carbon coatings},
Journal = {Diam. Relat. Mater. (Netherlands)},
Volume = {11},
Number = {9},
Pages = {1643 - 7},
url = {http://dx.doi.org/10.1016/S0925-9635(02)00109-7},
Keywords = {adhesion;amorphous state;carbon;delamination;friction;internal
stresses;Raman spectra;thin films;},
Abstract = {The important properties of thin films that are used for any
applications, especially tribological, are lower internal
stress and extremely good adhesive properties. The present
investigation examines the effect of film thickness on the
compressive stress, adhesive strength (critical load),
microstructure and coefficient of friction of diamond-like
carbon films prepared under floating conditions (no
substrate bias), on silicon substrates. The results show
that the compressive stress increases rapidly with thickness
in the lower thickness range of up to 50 nm, followed by a
slight decrease and thereafter it increases at a slower rate
before it delaminates at a thickness of approximately 190
nm. The adhesive strength in terms of critical load shows
that the critical load increases with increasing the film
thickness up to approximately 110 nm and thereafter it
decreases with thickness. The decrease in critical load with
thickness, for the films having thickness above 110 nm, is
due to the dominant effect of internal stress. The
tribological characterisation reveals that the substrate
influence on the coefficient of friction is relatively high
for the thinnest films ( ~<40 nm). We also discuss the
results of UV and visible Raman spectroscopy as a function
of thickness. It is suggested from the characterisation
results that appropriate thickness range of the film
(prepared under floating condition), is ~40-110
nm},
Key = {7442917}
}
@article{8589831,
Author = {Yim, E.K.F. and Reano, R.M. and Pang, S.W. and Yee, A.F. and Chen, C.S. and Leong, K.W.},
Title = {Nanopattern-induced changes in morphology and motility of
smooth muscle cells},
Journal = {Biomaterials (UK)},
Volume = {26},
Number = {26},
Pages = {5405 - 13},
url = {http://dx.doi.org/10.1016/j.biomaterials.2005.01.058},
Keywords = {biomechanics;biomedical materials;blood vessels;cellular
biophysics;muscle;nanopatterning;polymers;},
Abstract = {Cells are known to be surrounded by nanoscale topography in
their natural extracellular environment. The cell behavior,
including morphology, proliferation, and motility of bovine
pulmonary artery smooth muscle cells (SMC) were studied on
poly(methyl methacrylate) (PMMA) and poly(dimethylsiloxane)
(PDMS) surfaces comprising nanopatterned gratings with 350nm
linewidth, 700nm pitch, and 350nm depth. More than 90% of
the cells aligned to the gratings, and were significantly
elongated compared to the SMC cultured on non-patterned
surfaces. The nuclei were also elongated and aligned.
Proliferation of the cells was significantly reduced on the
nanopatterned surfaces. The polarization of microtubule
organizing centers (MTOC), which are associated with cell
migration, of SMC cultured on nanopatterned surfaces showed
a preference towards the axis of cell alignment in an in
vitro wound healing assay. In contrast, the MTOC of SMC on
non-patterned surfaces preferentially polarized towards the
wound edge. It is proposed that this nanoimprinting
technology will provide a valuable platform for studies in
cell-substrate interactions and for development of medical
devices with nanoscale features. [All rights reserved
Elsevier]},
Key = {8589831}
}
%% Lo, Joseph Y
@article{fds159363,
Author = {RS Saunders and E Samei and JY Lo and JA Baker},
Title = {Can compression be reduced for breast tomosynthesis? Monte
carlo study on mass and microcalcification conspicuity in
tomosynthesis.},
Journal = {Radiology, United States},
Volume = {251},
Number = {3},
Pages = {673-82},
Year = {2009},
Month = {June},
ISSN = {1527-1315},
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.},
Key = {fds159363}
}
@article{fds159367,
Author = {AS Chawla and RS Saunders and S Singh and JY Lo and E
Samei},
Title = {Towards optimized acquisition scheme for multiprojection
correlation imaging of breast cancer.},
Journal = {Academic radiology, United States},
Volume = {16},
Number = {4},
Pages = {456-63},
Year = {2009},
Month = {April},
ISSN = {1878-4046},
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.},
Key = {fds159367}
}
@article{fds159365,
Author = {JL Jesneck and S Mukherjee and Z Yurkovetsky and M Clyde, JR Marks and AE Lokshin and JY Lo},
Title = {Do serum biomarkers really measure breast
cancer?},
Journal = {BMC cancer, England},
Volume = {9},
Pages = {164},
Year = {2009},
ISSN = {1471-2407},
Abstract = {BACKGROUND: Because screening mammography for breast cancer
is less effective for premenopausal women, we investigated
the feasibility of a diagnostic blood test using serum
proteins. METHODS: This study used a set of 98 serum
proteins and chose diagnostically relevant subsets via
various feature-selection techniques. Because of significant
noise in the data set, we applied iterated Bayesian model
averaging to account for model selection uncertainty and to
improve generalization performance. We assessed
generalization performance using leave-one-out
cross-validation (LOOCV) and receiver operating
characteristic (ROC) curve analysis. RESULTS: The
classifiers were able to distinguish normal tissue from
breast cancer with a classification performance of AUC =
0.82 +/- 0.04 with the proteins MIF, MMP-9, and MPO. The
classifiers distinguished normal tissue from benign lesions
similarly at AUC = 0.80 +/- 0.05. However, the serum
proteins of benign and malignant lesions were
indistinguishable (AUC = 0.55 +/- 0.06). The classification
tasks of normal vs. cancer and normal vs. benign selected
the same top feature: MIF, which suggests that the
biomarkers indicated inflammatory response rather than
cancer. CONCLUSION: Overall, the selected serum proteins
showed moderate ability for detecting lesions. However, they
are probably more indicative of secondary effects such as
inflammation rather than specific for malignancy.},
Key = {fds159365}
}
@article{fds159368,
Author = {S Singh and GD Tourassi and JA Baker and E Samei and JY
Lo},
Title = {Automated breast mass detection in 3D reconstructed
tomosynthesis volumes: a featureless approach.},
Journal = {Medical physics, United States},
Volume = {35},
Number = {8},
Pages = {3626-36},
Year = {2008},
Month = {August},
ISSN = {0094-2405},
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.},
Key = {fds159368}
}
@article{fds159364,
Author = {MB Williams and P Raghunathan and MJ More and JA Seibert and A Kwan and JY
Lo, E Samei and NT Ranger and LL Fajardo and A McGruder and SM McGruder and AD Maidment and MJ Yaffe and A Bloomquist and GE Mawdsley},
Title = {Optimization of exposure parameters in full field digital
mammography.},
Journal = {Medical physics, United States},
Volume = {35},
Number = {6},
Pages = {2414-23},
Year = {2008},
Month = {June},
ISSN = {0094-2405},
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.},
Key = {fds159364}
}
@article{fds156860,
Author = {CE Floyd and AJ Kapadia and JE Bender and AC Sharma and JQ Xia and BP
Harrawood, GD Tourassi and JY Lo and AS Crowell and MR Kiser and CR
Howell},
Title = {Neutron-stimulated emission computed tomography of a
multi-element phantom.},
Journal = {Physics in medicine and biology, England},
Volume = {53},
Number = {9},
Pages = {2313-26},
Year = {2008},
Month = {May},
ISSN = {0031-9155},
Keywords = {Algorithms Diagnostic Imaging Equipment Design Gamma Rays
Humans Image Interpretation, Computer-Assisted Image
Processing, Computer-Assisted Models, Statistical Neoplasms
Neutrons* Phantoms, Imaging Scattering, Radiation
Spectrophotometry Tomography, Emission-Computed diagnosis
instrumentation* methods methods*},
Abstract = {This paper describes the implementation of
neutron-stimulated emission computed tomography (NSECT) for
non-invasive imaging and reconstruction of a multi-element
phantom. The experimental apparatus and process for
acquisition of multi-spectral projection data are described
along with the reconstruction algorithm and images of the
two elements in the phantom. Independent tomographic
reconstruction of each element of the multi-element phantom
was performed successfully. This reconstruction result is
the first of its kind and provides encouraging proof of
concept for proposed subsequent spectroscopic tomography of
biological samples using NSECT.},
Key = {fds156860}
}
@article{fds159369,
Author = {JQ Xia and JY Lo and K Yang and CE Floyd and JM Boone},
Title = {Dedicated breast computed tomography: volume image denoising
via a partial-diffusion equation based technique.},
Journal = {Medical physics, United States},
Volume = {35},
Number = {5},
Pages = {1950-8},
Year = {2008},
Month = {May},
ISSN = {0094-2405},
Keywords = {Algorithms Breast Computer Simulation Diffusion Equipment
Design Humans Image Processing, Computer-Assisted
Mammography Models, Statistical Models, Theoretical Quantum
Theory Radiographic Image Interpretation, Computer-Assisted
Sensitivity and Specificity Tomography, X-Ray Computed
X-Rays methods methods* pathology*},
Abstract = {Dedicated breast computed tomography (CT) imaging possesses
the potential for improved lesion detection over
conventional mammograms, especially for women with dense
breasts. The breast CT images are acquired with a glandular
dose comparable to that of standard two-view mammography for
a single breast. Due to dose constraints, the reconstructed
volume has a non-negligible quantum noise when thin section
CT slices are visualized. It is thus desirable to reduce
noise in the reconstructed breast volume without loss of
spatial resolution. In this study, partial diffusion
equation (PDE) based denoising techniques specifically for
breast CT were applied at different steps along the
reconstruction process and it was found that denoising
performed better when applied to the projection data rather
than reconstructed data. Simulation results from the
contrast detail phantom show that the PDE technique
outperforms Wiener denoising as well as adaptive trimmed
mean filter. The PDE technique increases its performance
advantage relative to Wiener techniques when the photon
fluence is reduced. With the PDE technique, the sensitivity
for lesion detection using the contrast detail phantom drops
by less than 7% when the dose is cut down to 40% of the
two-view mammography. For subjective evaluation, the PDE
technique was applied to two human subject breast data sets
acquired on a prototype breast CT system. The denoised
images had appealing visual characteristics with much lower
noise levels and improved tissue textures while maintaining
sharpness of the original reconstructed volume.},
Key = {fds159369}
}
@article{fds156861,
Author = {AS Chawla and E Samei and RS Saunders and JY Lo and JA
Baker},
Title = {A mathematical model platform for optimizing a
multiprojection breast imaging system.},
Journal = {Medical physics, United States},
Volume = {35},
Number = {4},
Pages = {1337-45},
Year = {2008},
Month = {April},
ISSN = {0094-2405},
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.},
Key = {fds156861}
}
@article{fds159366,
Author = {A Karellas and JY Lo and CG Orton},
Title = {Point/Counterpoint. Cone beam x-ray CT will be superior to
digital x-ray tomosynthesis in imaging the breast and
delineating cancer.},
Journal = {Medical physics, United States},
Volume = {35},
Number = {2},
Pages = {409-11},
Year = {2008},
Month = {February},
ISSN = {0094-2405},
Keywords = {Breast Neoplasms Forecasting Humans Mammography Radiographic
Image Enhancement Tomography, Spiral Computed Tomography,
X-Ray Computed radiography* trends*},
Key = {fds159366}
}
@article{fds159370,
Author = {MA Mazurowski and PA Habas and JM Zurada and JY Lo and JA Baker and GD
Tourassi},
Title = {Training neural network classifiers for medical decision
making: the effects of imbalanced datasets on classification
performance.},
Journal = {Neural networks : the official journal of the International
Neural Network Society, United States},
Volume = {21},
Number = {2-3},
Pages = {427-36},
ISSN = {0893-6080},
Keywords = {Algorithms Artificial Intelligence* Automatic Data
Processing Breast Neoplasms Computer Simulation Decision
Making* Diagnosis, Computer-Assisted Feedback* Humans Neural
Networks (Computer)* ROC Curve classification diagnosis
methods},
Abstract = {This study investigates the effect of class imbalance in
training data when developing neural network classifiers for
computer-aided medical diagnosis. The investigation is
performed in the presence of other characteristics that are
typical among medical data, namely small training sample
size, large number of features, and correlations between
features. Two methods of neural network training are
explored: classical backpropagation (BP) and particle swarm
optimization (PSO) with clinically relevant training
criteria. An experimental study is performed using simulated
data and the conclusions are further validated on real
clinical data for breast cancer diagnosis. The results show
that classifier performance deteriorates with even modest
class imbalance in the training data. Further, it is shown
that BP is generally preferable over PSO for imbalanced
training data especially with small data sample and large
number of features. Finally, it is shown that there is no
clear preference between oversampling and no compensation
approach and some guidance is provided regarding a proper
selection.},
Key = {fds159370}
}
@article{8104164,
Author = {Samei, E. and Saunders, R.S. and Lo, J.Y. and Dobbins, J.T. and Jesneck, J.L. and Floyd, C.E. and Ravin,
C.E.},
Title = {Fundamental imaging characteristics of a slot-scan digital
chest radiographic system},
Journal = {Med. Phys. (USA)},
Volume = {31},
Number = {9},
Pages = {2687 - 98},
url = {http://dx.doi.org/10.1118/1.1783531},
Keywords = {aluminium;diagnostic radiography;flat panel displays;image
resolution;lung;medical image processing;phantoms;},
Abstract = {Our purpose in this study was to evaluate the fundamental
image quality characteristics of a new slot-scan digital
chest radiography system (ThoraScan, Delft Imaging
Systems/Nucletron, Veenendaal, The Netherlands). The
linearity of the system was measured over a wide exposure
range at 90, 117, and 140 kVp with added Al filtration.
System uniformity and reproducibility were established with
an analysis of images from repeated exposures. The
modulation transfer function (MTF) was evaluated using an
established edge method. The noise power spectrum (NPS) and
the detective quantum efficiency (DQE) of the system were
evaluated at the three kilo-voltages over a range of
exposures. Scatter fraction (SF) measurements were made
using a posterior beam stop method and a geometrical chest
phantom. The system demonstrated excellent linearity, but
some structured nonuniformities. The 0.1 MTF values occurred
between 3.3-3.5 mm<sup>-1</sup>. The DQE(0.15) and DQE(2.5)
were 0.21 and 0.07 at 90 kVp, 0.18 and 0.05 at 117 kVp, and
0.16 and 0.03 at 140 kVp, respectively. The system exhibited
remarkably lower SFs compared to conventional full-field
systems with anti-scatter grid, measuring 0.13 in the lungs
and 0.43 in the mediastinum. The findings indicated that the
slot-scan design provides marked scatter reduction leading
to high effective DQE (DQE<sub>eff</sub>) of the system and
reduced patient dose required to achieve high image
quality},
Key = {8104164}
}
@article{6380590,
Author = {Munley, M.T. and Lo, J.Y. and Sibley, G.S. and Bentel, G.C. and Anscher, M.S. and Marks, L.B.},
Title = {A neural network to predict symptomatic lung
injury},
Journal = {Phys. Med. Biol. (UK)},
Volume = {44},
Number = {9},
Pages = {2241 - 9},
url = {http://dx.doi.org/10.1088/0031-9155/44/9/311},
Keywords = {biological effects of ionising radiation;dosimetry;health
hazards;lung;neural nets;radiation therapy;statistical
analysis;},
Abstract = {A nonlinear neural network that simultaneously uses
pre-radiotherapy (RT) biological and physical data was
developed to predict symptomatic lung injury. The input data
were pre-RT pulmonary function, three-dimensional treatment
plan doses and demographics. The output was a single value
between 0 (asymptomatic) and 1 (symptomatic) to predict the
likelihood that a particular patient would become
symptomatic. The network was trained on data from 97
patients for 400 iterations with the goal to minimize the
mean-squared error. Statistical analysis was performed on
the resulting network to determine the model's accuracy.
Results from the neural network were compared with those
given by traditional linear discriminate analysis and the
dose-volume histogram reduction (DVHR) scheme of Kutcher.
Receiver-operator characteristic (ROC) analysis was
performed on the resulting network which had
Az=0.833±0.04. (At is the area under the ROC curve.)
Linear discriminate multivariate analysis yielded an
Az=0.813±0.06. The DVHR method had
Az=0.521±0.08. The network was also used to rank the
significance of the input variables. Future studies will be
conducted to improve network accuracy and to include
functional imaging data},
Key = {6380590}
}
@article{fds133740,
Title = {Lo JY, Gavrielides MA, Markey MK, and Jesneck JL,
“Computer-aided classification of breast
microcalcification clusters: Merging of features from image
processing and radiologists,” Medical Imaging 2003: Image
Processing, Hanson KM, Ed., SPIE Medical Imaging 2003: Image
Processing, San Diego, CA, Proc. SPIE: (2003).},
Key = {fds133740}
}
%% Lobach, David F
@article{fds159420,
Author = {J O'Daniel and J Lucas and P Deverka and D Ermentrout and G Silvey and DF
Lobach, SB Haga},
Title = {Factors Influencing Uptake of Pharmacogenetic Testing in a
Diverse Patient Population.},
Journal = {Public health genomics},
Year = {2009},
Month = {May},
ISSN = {1662-8063},
Abstract = {Background: The successful integration of pharmacogenetic
(PGx) testing into clinical care will require attention to
patient attitudes. In this study, we aimed to identify the
major reasons why patients would or would not consider PGx
testing and whether these factors differed by race,
socioeconomic and insurance status, and medical history.
Methods: We developed and conducted a survey within the
adult patient population of the Duke Family Medicine Center.
Results: Of 75 completed surveys (65% African-American), 77%
indicated they were 'very likely' or 'somewhat likely' to
take a PGx test. Respondents who had experienced a side
effect were significantly more likely to indicate they would
take a PGx test and expressed greater interest in learning
more about testing than those who had not. Drug safety and
effectiveness were the major reasons to have PGx testing.
Privacy concerns and lack of insurance coverage for testing
were the major reasons to decline testing. Conclusions: We
found no differences in interest in PGx tests by race or
socioeconomic status, but found stronger interest from those
with a history of side effects and private insurance. While
the overall support of PGx testing is encouraging, greater
reassurance of medical privacy and development of
educational resources are needed.},
Key = {fds159420}
}
@article{fds164704,
Title = {Patwardhan MB, Kawamoto K, Lobach DF, Patel UD, Patchar DB.
Recommendations for a clinical decision support for the
management of individuals with chronic kidney disease. Clin
J Am Soc Nephrol, Feb. 2009; 4(2):273-83; Epub January
2009. },
Year = {2009},
Key = {fds164704}
}
@article{fds164705,
Title = {Sloane R, Snyder DC, Demark-Wahnefried W; Lobach D, Kraus
WE. Comparing the 7-day physical activity recall with a
triaxial accelerometer for measuring time in exercise. Med
Sci Sports Exerc, June 2009; 41(6):1334-40. },
Year = {2009},
Key = {fds164705}
}
@article{fds159421,
Author = {K Kawamoto and DF Lobach and HF Willard and GS Ginsburg},
Title = {A national clinical decision support infrastructure to
enable the widespread and consistent practice of genomic and
personalized medicine.},
Journal = {BMC medical informatics and decision making,
England},
Volume = {9},
Pages = {17},
Year = {2009},
ISSN = {1472-6947},
Keywords = {Databases as Topic Decision Making, Computer-Assisted
Decision Support Systems, Clinical Genome, Human Genomics*
Humans Information Systems Personal Health Services* United
States organization & administration organization &
administration* standards},
Abstract = {BACKGROUND: In recent years, the completion of the Human
Genome Project and other rapid advances in genomics have led
to increasing anticipation of an era of genomic and
personalized medicine, in which an individual's health is
optimized through the use of all available patient data,
including data on the individual's genome and its downstream
products. Genomic and personalized medicine could transform
healthcare systems and catalyze significant reductions in
morbidity, mortality, and overall healthcare costs.
DISCUSSION: Critical to the achievement of more efficient
and effective healthcare enabled by genomics is the
establishment of a robust, nationwide clinical decision
support infrastructure that assists clinicians in their use
of genomic assays to guide disease prevention, diagnosis,
and therapy. Requisite components of this infrastructure
include the standardized representation of genomic and
non-genomic patient data across health information systems;
centrally managed repositories of computer-processable
medical knowledge; and standardized approaches for applying
these knowledge resources against patient data to generate
and deliver patient-specific care recommendations. Here, we
provide recommendations for establishing a national decision
support infrastructure for genomic and personalized medicine
that fulfills these needs, leverages existing resources, and
is aligned with the Roadmap for National Action on Clinical
Decision Support commissioned by the U.S. Office of the
National Coordinator for Health Information Technology.
Critical to the establishment of this infrastructure will be
strong leadership and substantial funding from the federal
government. SUMMARY: A national clinical decision support
infrastructure will be required for reaping the full
benefits of genomic and personalized medicine. Essential
components of this infrastructure include standards for data
representation; centrally managed knowledge repositories;
and standardized approaches for leveraging these knowledge
repositories to generate patient-specific care
recommendations at the point of care.},
Key = {fds159421}
}
@article{fds159422,
Author = {EL Eisenstein and DF Lobach and K Kawamoto and R Edwards and JM Willis and GM Silvey and KJ Anstrom},
Title = {A randomized clinical trial of clinical decision support in
a rural community health network serving lower income
individuals: study design and baseline characteristics.},
Journal = {Studies in health technology and informatics,
Netherlands},
Volume = {143},
Pages = {220-6},
Year = {2009},
ISSN = {0926-9630},
Keywords = {Adolescent Adult Child, Preschool Community Networks*
Decision Support Systems, Clinical* Female Humans Infant
Male North Carolina Outcome Assessment (Health Care)
Poverty* Rural Population* Young Adult},
Abstract = {Lower income individuals in the US frequently experience
difficulties in obtaining access to needed health care
services. We describe a randomized clinical trial that seeks
to improve the quality of, and access to healthcare services
for medically underserved populations in five rural counties
of North Carolina. We propose to achieve these improvements
by implementing system-to-system integration via a
telehealth network with an asynchronous clinical decision
support system for health care providers.},
Key = {fds159422}
}
@article{fds150180,
Author = {CE Mosher and BF Fuemmeler and R Sloane and WE Kraus and DF Lobach and DC
Snyder, W Demark-Wahnefried},
Title = {Change in self-efficacy partially mediates the effects of
the FRESH START intervention on cancer survivors' dietary
outcomes.},
Journal = {Psycho-oncology},
Volume = {17},
Number = {10},
Pages = {1014-1023},
Year = {2008},
Month = {February},
ISSN = {1099-1611},
Abstract = {Objective: This study examined change in self-efficacy as a
mediator of the effects of a mailed print intervention on
the dietary and exercise practices of newly diagnosed breast
and prostate cancer survivors.Method: A total of 543 breast
and prostate cancer patients were recruited from 39 states
and two provinces within North America. Participants were
randomly assigned to receive a 10-month program of tailored
mailed print materials that aimed to increase fruit and
vegetable consumption, reduce fat intake, and/or increase
exercise or a 10-month program of publically available
materials on diet and exercise. Telephone surveys conducted
at baseline and 1 year assessed dietary practices, physical
activity, and self-efficacy for engaging in these health
behaviors.Results: Results indicated that changes in
self-efficacy for fat restriction and eating more fruits and
vegetables were significant mediators of the intervention's
effects on dietary outcomes at 1-year follow-up. The
intervention did not significantly affect self-efficacy for
exercise; however, a significant, positive relationship was
found between self-efficacy for exercise and exercise
duration at follow-up.Conclusions: Findings are largely
consistent with Social Cognitive Theory and support the use
of strategies to increase self-efficacy in health promotion
interventions for cancer survivors. Copyright (c) 2008 John
Wiley & Sons, Ltd.},
Key = {fds150180}
}
@article{fds164703,
Title = {Snyder DC, Sloane R, Lobach, DF, Lipkus IM, Peterson B,
Kraus W, Demar-Wahnefried W. Differences in baseline
characteristics and performance at one-and two-year
follow-up of cancer survivors accrued via self-referral
versus cancer registry in the FRESH START diet and exercise
trial. Cancer Epidemiol Biomarkers Prev. 2008;
17:1288-1294},
Year = {2008},
Key = {fds164703}
}
%% MacFall, James R
@article{1959228,
Author = {Goodman, J.A. and Ellsworth, R.W. and Ito, A.S. and MacFall,
J.R. and Siohan, F. and Streitmatter, R.E. and Tonar, S.C. and Viswanath, P.R. and Yodh, G.B.},
Title = {Delayed hadrons in extensive air showers: evidence for the
iron-group nuclei in primary cosmic-ray flux at energies
~1013-1015 eV},
Journal = {Phys. Rev. D, Part. Fields (USA)},
Volume = {26},
Number = {5},
Pages = {1043 - 60},
Year = {1},
url = {http://dx.doi.org/10.1103/PhysRevD.26.1043},
Keywords = {cosmic ray energy spectra;cosmic ray nuclei;cosmic ray
protons;cosmic ray showers and bursts;},
Abstract = {The distribution of arrival time of energetic hadrons in the
near-core region of air showers of energies
~10<sup>4</sup>-10<sup>6</sup> GeV relative to the shower
front has been studied experimentally at mountain altitude.
The observed rate of hadron events with (i) energy >50
GeV in the calorimeter, (ii) associated shower particle
density >18 m<sup>-2</sup>, and (iii) a signal ⩾5
equivalent particles in a plastic scintillator
<i>T</i><sub>3</sub> of area 0.54 m<sup>2</sup> placed under
220 g cm<sup>-2</sup> of absorber in the calorimeter is
found to be 1.85×10<sup>-3</sup> m<sup>-2</sup>
sr<sup>-1</sup> sec<sup>-1</sup>. Of these events a fraction
(0.55±0.05)% have shown the signal from
<i>T</i><sub>3</sub> to be delayed by 15 nsec or greater
relative to shower particles. Monte Carlo simulations of
experimental observations have shown that these requirements
on energy and shower density enhance the sensitivity of the
observed rate to the contributions due to showers initiated
by heavy nuclei. Calculations also show that observed
delayed hadrons are mostly associated with showers due to
heavy nuclei. For interpretation of observed features two
models for primary composition have been considered. In the
first model the power-law spectra for protons and lighter
nuclei are assumed to have spectral index
γ<sub>p</sub> and the heavy (iron group) nuclei the
index γ<sub>Fe</sub>. An agreement between the
expectation and observation requires the values of
γ<sub>p</sub> and γ<sub>Fe</sub> to be
significantly different as -2.68 and -2.39 in the energy
range ~10<sup>3</sup>-10<sup>6</sup> GeV. In the second
model the spectral index γ is assumed to be the same
for all components and the spectra steepen by 0.5 at the
same rigidity <i>R</i><sub>c</sub>. It is found that the
values of γ and <i>R</i><sub>c</sub> should be -2.55
and 10<sup>5</sup> GV/<i>c</i>, respectively, to match the
observations. It is concluded that a successful
understanding of experimental observations requires a
relative change between the energy spectra of protons and
heavy nuclei in the energy range ~10<sup>4</sup>-10<sup>6</sup>
GeV, which would make the proportion of iron-group nuclei
about 40% of the primary flux at these energies},
Key = {1959228}
}
@article{2796238,
Author = {Wehrli, F.W. and Shimakawa, A. and Gullberg, G.T. and MacFall, J.R.},
Title = {Time-of-flight MR flow imaging: selective saturation
recovery with gradient refocusing},
Journal = {Radiology (USA)},
Volume = {160},
Number = {3},
Pages = {781 - 5},
Keywords = {biomedical NMR;flow measurement;haemodynamics;patient
diagnosis;},
Abstract = {A novel magnetic resonance flow-imaging technique is
presented and its suitability evaluated for both qualitative
and quantitative imaging of flow. The method is derived from
a selective saturation-recovery scheme consisting of a
tagging and detection pulse followed by a bipolar read
gradient. The detrimental phase effects causing signal loss
at fast flow are shown to be greatly reduced because of the
absence of a 180° pulse and its associated
section-selection gradient. The second loss mechanism
intrinsic to 180° spin echoes, the washout of excited
spins between excitation and detection pulse, likewise is
not present with the discussed technique. Assuming a
parabolic flow profile, the authors calculated the signal
evolution curve and found it to be in agreement with the
experimental washout curve},
Key = {2796238}
}
@article{4570588,
Author = {Turkington, T.G. and Jaszczak, R.J. and Pelizzari, C.A. and Harris, C.C. and MacFall, J.R. and Hoffman, J.M. and Coleman, R.E.},
Title = {Accuracy of registration of PET, SPECT and MR images of a
brain phantom},
Journal = {J. Nucl. Med. (USA)},
Volume = {34},
Number = {9},
Pages = {1587 - 94},
Keywords = {biomedical NMR;brain;computerised tomography;radioisotope
scanning and imaging;},
Abstract = {Accuracy of a surface-fitting algorithm for
three-dimensional (3D) image registration of single photon
emission computed tomography (SPECT), positron emission
tomography (PET), and magnetic resonance (MR) images was
tested using a 3D, water-fillable brain phantom. Multislice
or volume image sets were acquired for each modality. Small
fiducial markers were attached to assess accuracy of surface
fitting and provide an alternate fitting technique. A
maximum gradient technique was found to work well for SPECT
and PET edge detection. Transformation parameters for
translation, rotation and scaling were determined by surface
fit to match each SPECT and PET scan with MR images. Using
the markers, overall translation errors were found to be
<2 mm in each direction and rotational errors <2
degrees in every case. Errors for specific internal regions
were also determined to be <2 mm for most regions, with
only a few fits resulting in errors >3 mm for some
cortical regions. Results indicate surface fitting to be
sufficiently accurate for visual comparison of registered
images and for enhanced SPECT and PET region of interest
determination and image reconstruction},
Key = {4570588}
}
@article{6065742,
Author = {Hsu, E.W. and Hedlund, L.W. and MacFall,
J.R.},
Title = {Functional MRI of the rat somatosensory cortex: effects of
hyperventilation},
Journal = {Magn. Reson. Med. (USA)},
Volume = {40},
Number = {3},
Pages = {421 - 6},
Keywords = {biomedical NMR;brain;haemodynamics;neurophysiology;somatosensory
phenomena;},
Abstract = {Functional mapping of the rat somatosensory cortex was
performed with T<sub>2</sub>*-sensitized MRI using a forepaw
electrical stimulation model in α-chloralose-anesthetized
rats at 7 T under both normocapnia and mild
hyperventilation-induced hypocapnia. A highly localized
activation area, consistent with the known somatosensory
cortical region, was detected in all seven animals studied
during hypocapnia and in five of the same animals during
normocapnia, Quantitatively, hypocapnia was found to
significantly increase both the size of the fMRI activation
area (3.4±0.6 mm<sup>2</sup> versus 1.5±0.6
mm<sup>2</sup> in normocapnia, mean±standard error,
n=7, P<0.03) and the average fMRI signal intensity
increase (3.4±0.6% versus 2.7±0.4%, n=5,
P<0.05). The increased sensitivity of fMRI to functional
activation may reflect a widened arterial-venous oxygenation
difference resulting from an increased effective oxygen
extraction during hyperventilation. The dependence of the
fMRI response on the ventilation state underscores the need
to control for physiological parameters in animal fMRI
studies},
Key = {6065742}
}
@article{4766650,
Author = {Zhengrong Liang and MacFall, J.R. and Harrington,
D.P.},
Title = {Parameter estimation and tissue segmentation from
multispectral MR images},
Journal = {IEEE Trans. Med. Imaging (USA)},
Volume = {13},
Number = {3},
Pages = {441 - 9},
url = {http://dx.doi.org/10.1109/42.310875},
Keywords = {biomedical NMR;brain;image segmentation;medical image
processing;parameter estimation;},
Abstract = {A statistical method is developed to classify tissue types
and to segment the corresponding tissue regions from
relaxation time T<sub>1</sub>, T<sub>2</sub>, and proton
density P<sub>D</sub> weighted magnetic resonance images.
The method assumes that the distribution of image
intensities associated with each tissue type can be
expressed as a multivariate likelihood function of three
weighted signal intensity values (T<sub>1</sub>,
T<sub>2</sub>, P<sub>D</sub>) at each location within that
tissue regions. The method further assumes that the
underlying tissue regions are piecewise contiguous and can
be characterized by a Markov random field prior. In
classifying the tissue types, the method models the
likelihood of realizing the images as a finite
multivariate-mixture function. The class parameters
associated with the tissue types (i.e. the weighted
intensity means, variances and correlation coefficients of
the multivariate function, as well as the number of voxels
within regions of the tissue types of are estimated by
maximum likelihood. The estimation fits the class parameters
to the image data via the expectation-maximization
algorithm. The number of classes associated with the tissue
types is determined by the information criterion of minimum
description length. The method segments the tissue regions,
given the estimated class parameters, by maximum a
posteriori probability. The prior is constructed by the
tissue-region membership of the first- and second-order
neighborhood. The method is tested by a few sets of
T<sub>1</sub>, T<sub>2</sub>, and P<sub>D</sub> weighted
images of the brain acquired with a 1.5 Tesla whole body
scanner. The number of classes and the associated class
parameters are automatically estimated. The regions of
different brain tissues are satisfactorily
segmented},
Key = {4766650}
}
@article{6428887,
Author = {Donnelly, L.F. and MacFall, J.R. and Page McAdams and H. and Majure, J.M. and Smith, J. and Frush, D.P. and Bogonad, P. and Charles, H.C. and Ravin, C.E.},
Title = {Cystic fibrosis: combined hyperpolarized
3He-enhanced and conventional proton MR imaging
in the lung-preliminary observations},
Journal = {Radiology (USA)},
Volume = {212},
Number = {3},
Pages = {885 - 9},
Address = {Chicago, IL, USA},
Keywords = {biomedical MRI;diseases;helium;lung;spin-spin
relaxation;},
Abstract = {Four patients with cystic fibrosis (CF) were examined with
combined hyperpolarized helium 3-enhanced and conventional
proton magnetic resonance (MR) imaging. After inhalation of
the polarized <sup>3</sup>He gas, single breath-hold,
gradient-echo images (resonant frequency of <sup>3</sup>He)
were obtained to depict lung ventilation. Conventional
T2-weighted fast spin-echo (hydrogen) images were also
obtained to depict morphologic abnormalities. <sup>3</sup>He
images were successfully and reproducibly generated that
showed both morphologic abnormalities and, often more
extensive, ventilation abnormalities. <sup>3</sup>He MR
imaging may provide a method for evaluating progression of
pulmonary disease in patients with CF},
Key = {6428887}
}
@article{3284223,
Author = {Jones, R.D. and MacFall, J.R.},
Title = {Computers in magnetic resonance imaging},
Journal = {Comput. Phys. (USA)},
Volume = {2},
Number = {5},
Pages = {25 - 30},
Keywords = {biomedical NMR;medical diagnostic computing;},
Abstract = {Most of modern medical imaging would not be possible without
compact, fast computer systems. This is particularly the
case for magnetic resonance imaging (MRI), in which many
complicated calculations must be carried out in order to
create an image from the approximately 8 million data
samples that are acquired during the typical patient
examination. The future of MRI will see interesting
architectural changes, as processor hardware costs decrease
and system bus bandwidth requirements increase. True
parallel processing arrangements will become more popular
and adaptable architectures that can be dynamically
configured for parallel, pipeline, or sequential operation
will become more common. Indeed, as with array processors
that are so important in existing MRI equipment, the bus
architectures of the entire system will become key to
performance},
Key = {3284223}
}
%% Malkin, Robert A.
@article{5749678,
Author = {Malkin, R.A. and Penzotti, J.E. and Juhlin, S.P. and Pilkington, T.C. and Plonsey, R.},
Title = {Statistical analysis of signals from an intracavitary probe
in a diseased heart},
Journal = {Med. Biol. Eng. Comput. (UK)},
Volume = {35},
Number = {5},
Pages = {462 - 6},
Keywords = {electrocardiography;medical signal processing;physiological
models;probes;statistical analysis;},
Abstract = {A model study introduces the use of statistical signal
processing to analyse the signals from an intracavitary
probe. A complete derivation is given for the detection of
one type of arrhythmogenic substrate, myocardial infarctions
(Mis). Both the use of statistical signal processing and the
detection of VT substrates, as opposed to activation maps,
are unique. A quasi-stationary electromagnetic model with
simplified geometry is presented. The model is used to
simulate ventricular pacing in the presence of MI. The
likelihood ratio is used for detection. A tabulation of the
results from this model shows that an intracavitary probe
can be used to detect Mis as small as 400 mm<sup>2</sup> in
1 mV of noise with a detectability index of 0.495, where 0.5
indicates perfect defection. Sensitivity to noise can be
reduced by analysing multiple heart beats. The results are
only slightly affected by changing the probe from a cage
frame design, which mechanically supports the electrodes on
thin spokes, to a balloon design, which supports the
electrodes on the surface of an insulating
balloon},
Key = {5749678}
}
%% Massoud, Hisham Z.
@article{4786538,
Author = {Mirabedini, M.R. and Goodwin-Johansson, S.H. and Massoud,
H.Z. and Fair, R.B.},
Title = {Subquarter-micrometre elevated source-and-drain MOSFET
structure using polysilicon spacers},
Journal = {Electron. Lett. (UK)},
Volume = {30},
Number = {19},
Pages = {1631 - 2},
Year = {15},
url = {http://dx.doi.org/10.1049/el:19941068},
Keywords = {capacitance;elemental semiconductors;insulated gate field
effect transistors;semiconductor device models;silicon;},
Abstract = {A novel subquarter-micrometre MOSFET with a selfaligned
source and drain structure is proposed with elevated sources
and drains formed by using polysilicon spacers. The spacers
can reduce the effective channel length by 50% compared to
the mask length, and reduce the junction capacitance by over
30% through a reduction in junction area, as shown by PISCES
simulations. A graded oxide spacer is used to decrease the
parasitic gate-to-drain capacitance},
Key = {4786538}
}
@article{4521124,
Author = {Sampson, R.K. and Massoud, H.Z.},
Title = {Resolution of silicon wafer temperature measurement by
in situ ellipsometry in a rapid thermal
processor},
Journal = {J. Electrochem. Soc. (USA)},
Volume = {140},
Number = {9},
Pages = {2673 - 8},
Keywords = {elemental semiconductors;ellipsometry;rapid thermal
processing;silicon;spectral methods of temperature
measurement;},
Abstract = {The application of ellipsometry as a technique for <i>in</i>
<i>situ</i> silicon wafer temperature measurement in a rapid
thermal processing environment was investigated. This
techinque is based on the ellipsometric measurement of the
refractive index of silicon, and then the determination of
the temperature from the known temperature dependence of the
refractive index. An algorithm was developed which enables
the determination of the resolution limits of this
technique. Within the temperature range from 0 to
1100°C, a worst-case temperature error of
±10°C can be expected for an ellipsometer
operating at a wavelength of 6328 Å and resolving
0.01° in the measured parameters ψ and Δ, and
in the angle of incidence φ. For an ellipsometer
operating at a wavelength of 4133 Å, the maximum error
improves to within ±1.4°C, for the temperature
range investigated from 0 to 700°C},
Key = {4521124}
}
@article{6417950,
Author = {Shanware, A. and Massoud, H.Z. and Vogel, E. and Henson, K. and Hauser, J.R. and Wortman, J.J.},
Title = {Modeling the trends in valence-band electron tunneling in
NMOSFETs with ultrathin SiO2 and
SiO2/Ta2O5 dielectrics with
oxide scaling},
Journal = {Microelectron. Eng. (Netherlands)},
Volume = {48},
Number = {1-4},
Pages = {295 - 8},
Address = {Koster Banz, Germany},
url = {http://dx.doi.org/10.1016/S0167-9317(99)00392-5},
Keywords = {conduction bands;MOSFET;semiconductor device models;silicon
compounds;tantalum compounds;tunnelling;valence
bands;},
Abstract = {Gate oxide scaling in NMOSFETs causes electrons to tunnel
from the conduction and valence bands of the silicon
substrate in the direct-tunneling regime. In NMOSFETs, the
tunneling of electrons from the substrate's valence band is
a source of the substrate current I<sub>B</sub> and
contributes to the gate current I<sub>G</sub>. Oxide
thickness scaling leads to an increase in the substrate
current I<sub>B</sub> and in the ratio I<sub>B</sub>/I<sub>G</sub>
of substrate to gate current. In this paper, we report the
trends in the I<sub>B</sub>/I<sub>G</sub> ratio due to oxide
thickness scaling in ultrathin SiO<sub>2</sub> and
SiO<sub>2</sub>/Ta<sub>2</sub>O<sub>5</sub> composite gate
dielectrics},
Key = {6417950}
}
@article{6417906,
Author = {Shiely, J.P. and Massoud, H.Z.},
Title = {Simulation of the drain-current characteristics of MOSFETs
with ultrathin oxides in the presence of direct
tunneling},
Journal = {Microelectron. Eng. (Netherlands)},
Volume = {48},
Number = {1-4},
Pages = {101 - 4},
Address = {Koster Banz, Germany},
url = {http://dx.doi.org/10.1016/S0167-9317(99)00347-0},
Keywords = {MOSFET;semiconductor device models;tunnel
transistors;},
Abstract = {Carrier tunneling in the gate dielectric, especially in the
direct-tunneling regime where large current densities flow
through the gate oxide, are known to result in substantial
changes in the drain-current characteristics of MOSFETs. In
this paper, we present simulation results of the
drain-current characteristics of MOSFETs with ultrathin
oxide using Tunnel-PISCES, a MOSFET tunneling simulator that
models electron tunneling through the gate dielectric in a
self-consistent manner with carrier transport by drift and
diffusion in the substrate. We are able to predict the
experimental trends reported for the dependence of the drain
current of ultrathin-oxide MOSFETs on gate-oxide thickness.
This tunneling simulation capability provides a means for
generating MOSFET sizing guidelines to avoid
tunneling-induced drain-current degradation},
Key = {6417906}
}
@article{6417892,
Author = {Shanware, A. and Massoud, H.Z. and Acker, A. and Li, V.Z.-Q. and Mirabedini, M.R. and Henson, K. and Hauser, J.R. and Wortman, J.J.},
Title = {The effects of Ge content in poly-Si1-xGe gate
material on the tunneling barrier in PMOS
devices},
Journal = {Microelectron. Eng. (Netherlands)},
Volume = {48},
Number = {1-4},
Pages = {39 - 42},
Address = {Koster Banz, Germany},
url = {http://dx.doi.org/10.1016/S0167-9317(99)00333-0},
Keywords = {conduction bands;Ge-Si alloys;interface states;MOSFET;semiconductor
device measurement;semiconductor materials;stoichiometry;tunnelling;valence
bands;},
Abstract = {The use of SiGe gates in MOSFET technology has promise as a
single-gate material for both n- and p-channel MOSFETs. The
Ge content in the gate, however, affects the gate energy
band diagram. While Ge in the SiGe gate does not affect the
conduction-band energy level, it is found to raise the
valence-band energy level and reduce the gate bandgap. This
change results in an increase in the gate current resulting
mainly from the tunneling of electrons from the valence band
of the gate in PMOSFETs. This paper reports on the effects
of Ge content in SiGe gates on the tunneling characteristics
of PMOSFETs},
Key = {6417892}
}
%% Myers, Barry S
@booklet{Dibb09,
Author = {A. T. Dibb and R. W. Nightingale and J. F. Luck and V. C.
Chancey and L. E. Fronheiser and B. S. Myers},
Title = {Tension and Combined Tension-Extension Structural Response
and Tolerance Properties of the Human Male Ligamentous
Cervical Spine},
Journal = {Journal Of Biomechanical Engineering-transactions Of The
Asme},
Volume = {131},
Number = {8},
Year = {2009},
Month = {August},
ISSN = {0148-0731},
Abstract = {Tensile loading of the human cervical spine results from
noncontact inertial loading of the head as well as
mandibular and craniofacial impacts. Current vehicle safety
standards include a neck injury criterion based on beam
theory that uses a linear combination of the normalized
upper cervical axial force and sagittal plane moment. This
study examines this criterion by imposing combined axial
tension and bending to postmortem human subject (PMHS)
ligamentous cervical spines. Tests were conducted on 20
unembalmed PMHSs. Nondestructive whole cervical spine
tensile tests with varying cranial end condition and
anteroposterior loading location were used to generate
response corridors for computational model development and
validation. The cervical spines were sectioned into three
functional spinal segments (Occiput-C2, C4-C5, and C6-C7)
for measurement of tensile structural response and failure
testing. The upper cervical spine (Occiput-C2) was found to
be significantly less stiff, absorb less strain energy, and
fail at higher loads than the lower cervical spine (C4-C5
and C6-C7). Increasing the moment arm of the applied tensile
load resulted in larger head rotations, larger moments, and
significantly higher tensile ultimate strengths in the upper
cervical spine. The strength of the upper cervical spine
when loaded through the head center of gravity (2417 +/- 215
N) was greater than when loaded over the occipital condyles
(2032 +/- 250 N), which is not predicted by beam theory.
Beam theory predicts that increased tensile loading
eccentricity results in decreased axial failure loads.
Analyses of the force-deflection histories suggest that
ligament loading in the upper cervical spine depends on the
amount of head rotation orientation, which may explain why
the neck is stronger in combined tension and
extension.},
Key = {Dibb09}
}
@booklet{Siegmund08,
Author = {G. P. Siegmund and M. B. Davis and K. P. Quinn and E. Hines and B. S. Myers and S. Ejima and K. Ono and K. Kamiji and T.
Yasuki and B. A. Winkelstein},
Title = {Head-turned postures increase the risk of cervical facet
capsule injury during whiplash},
Journal = {Spine},
Volume = {33},
Number = {15},
Pages = {1643 -- 1649},
Year = {2008},
Month = {July},
ISSN = {0362-2436},
Abstract = {Study Design. In vitro experiments using cadaveric cervical
spine motion segments to quantify facet capsular ligament
strain during whiplash-like loading. Objective. To quantify
facet capsule strains during whiplash-like loading with an
axial intervertebral prerotation simulating an initial
head-turned posture and to then compare these strains to
previously-published strains for partial failure and gross
failure of the facet capsule for these specimens. Summary of
Background Data. Clinical data have shown that a head-turned
posture at impact increases the severity and duration of
whiplash-related symptoms. Methods. Thirteen motion segments
were used from 7 women donors ( 50 +/- 10 years). Axial
pretorques (+/-1.5 Nm), axial compressive preloads ( 45,
197, and 325 N), and quasi-static shear loads (
posteriorly-directed horizontal forces from 0 to 135 N) were
applied to the superior vertebral body to simulate whiplash
kinematics with the head turned. Three-dimensional
displacements of markers placed on the right facet capsular
ligament were used to estimate the strain field in the
ligament during loading. The effects of pretorque direction,
compression, and posterior shear on motion segment motion
and maximum principal strain in the capsule were examined
using repeated-measures analyses of variance. Results. Axial
pretorque affected peak capsule strains more than axial
compression or posterior shear. Peak strains reached 34\%
+/- 18\% and were higher for pretorques toward rather than
away from the facet capsule (i.e., head rotation to the
right caused higher strain in the right facet capsule).
Conclusion. Compared to previously-reported data for these
specimens, peak capsule strains with a pretorque were double
those without a pretorque ( 17\% +/- 6\%) and not
significantly different from those at partial failure of the
ligament ( 35\% +/- 21\%). Thus a head-turned posture
increases facet capsular ligament strain compared to a
neutral head posture - a finding consistent with the greater
symptom severity and duration observed in whiplash patients
who have their head turned at impact.},
Key = {Siegmund08}
}
@booklet{Finan08,
Author = {J. D. Finan and R. W. Nightingale and B. S.
Myers},
Title = {The Influence of Reduced Friction on Head Injury Metrics in
Helmeted Head Impacts},
Journal = {Traffic Injury Prevention},
Volume = {9},
Number = {5},
Pages = {483 -- 488},
Year = {2008},
ISSN = {1538-9588},
Abstract = {Objective. Reducing surface friction has been shown to
reduce head injury risk in some scenarios. However, rigid
body mechanics suggests that other scenarios may exist in
which reducing surface friction increases head injury risk.
The goal of this study is to demonstrate that reducing
friction on the surface of a helmet decreases the rotational
acceleration of the head in some scenarios and increases it
in other scenarios and to discuss the implications for
helmet design. Methods. A series of drop tests were
conducted to simulate normal and oblique impacts and assess
head injury risk with conventional helmets and helmets that
had been modified to reduce friction. Results. The low
friction modification had little influence on peak linear
head acceleration or HIC. However, it decreased peak
rotational acceleration by 55\% in one oblique impact
scenario and increased it by 83\% in another oblique impact
scenario. In normal impacts, the low friction modification
had no effect on peak rotational acceleration. Conclusions.
The relationship between rotational acceleration and surface
friction is sensitive to the impact scenario. A single
oblique impact test may be misleading when assessing the
overall performance of a low friction helmet. The
implications of these findings for helmet design are
discussed.},
Key = {Finan08}
}
@booklet{Kliewer93,
Author = {M. A. Kliewer and L. Gray and J. Paver and W. D. Richardson and J. B. Vogler and J. H. Mcelhaney and B. S.
Myers},
Title = {Acute spinal ligament disruption - mr-imaging with anatomic
correlation},
Journal = {Jmri-journal Of Magnetic Resonance Imaging},
Volume = {3},
Number = {6},
Pages = {855 -- 861},
Year = {1993},
ISSN = {1053-1807},
Abstract = {Disruption of spinal ligaments can lead to instability that
jeopardizes the spinal cord and nerve roots. Magnetic
resonance (MR) imaging can directly image spinal ligaments;
however, the sensitivity with which this modality
demonstrates ligament injury has, to the authors' knowledge,
not been reported. On a biomechanical testing machine, 28
cadaveric spines were subjected to controlled injury that
resulted in ligament tears. The spines were then imaged with
plain radiography, computed tomography, and MR imaging (1.5
T). The images were analyzed for evidence of ligament injury
before dissection of the specimen. Forty-one of 52 (79\%)
ligament tears of various types were correctly identified at
MR imaging. Disruptions of the anterior and posterior
longitudinal ligaments were most conspicuous and were
detected in all seven cases in which they were present (no
false-positive or false-negative results); disruptions of
the ligamentum flavum, capsular ligaments, and interspinous
ligaments could also be identified but less reliably (three
false-positive and 11 false-negative results). That MR
imaging can reliably and directly allow assessment of spinal
ligament disruption In this in vitro model suggests its
potential utility for this assessment in
patients.},
Key = {Kliewer93}
}
%% Needham, David
@booklet{Yang09,
Author = {C. M. Yang and D. Plackett and D. Needham and H. M.
Burt},
Title = {PLGA and PHBV Microsphere Formulations and Solid-State
Characterization: Possible Implications for Local Delivery
of Fusidic Acid for the Treatment and Prevention of
Orthopaedic Infections},
Journal = {Pharmaceutical Research},
Volume = {26},
Number = {7},
Pages = {1644 -- 1656},
Year = {2009},
Month = {July},
ISSN = {0724-8741},
Abstract = {To develop and characterize the solid-state properties of
poly(DL-lactic-co-glycolic acid) (PLGA) and
poly(3-hydroxybutyric acid-co-3-hydroxyvaleric acid) (PHBV)
microspheres for the localized and controlled release of
fusidic acid (FA). The effects of FA loading and polymer
composition on the mean diameter, encapsulation efficiency
and FA released from the microspheres were determined. The
solid-state and phase separation properties of the
microspheres were characterized using DSC, XRPD, Raman
spectroscopy, SEM, laser confocal and real time recording of
single microspheres formation. Above a loading of 1\% (w/w)
FA phase separated from PLGA polymer and formed distinct
spherical FA-rich amorphous microdomains throughout the PLGA
microsphere. For FA-loaded PLGA microspheres, encapsulation
efficiency and cumulative release increased with initial
drug loading. Similarly, cumulative release from FA-loaded
PHBV microspheres was increased by FA loading. After the
initial burst release, FA was released from PLGA
microspheres much slower compared to PHBV microspheres. A
unique phase separation phenomenon of FA in PLGA but not in
PHBV polymers was observed, driven by coalescence of liquid
microdroplets of a DCM-FA-rich phase in the forming
microsphere.},
Key = {Yang09}
}
@booklet{Tashjian08,
Author = {J. A. Tashjian and M. W. Dewhirst and D. Needham and B. L.
Viglianti},
Title = {Rationale for and measurement of liposomal drug delivery
with hyperthermia using non-invasive imaging
techniques},
Journal = {International Journal Of Hyperthermia},
Volume = {24},
Number = {1},
Pages = {79 -- 90},
Year = {2008},
ISSN = {0265-6736},
Abstract = {The purpose of this review is to present an overview of the
state-of-the-art imaging modalities used to track drug
delivery from liposomal formulations into tumors during or
after hyperthermia treatment. Liposomes are a drug delivery
system comprised of a phospholipid bilayer surrounding an
aqueous core and have been shown to accumulate following
hyperthermia therapy. Use of contrast-containing liposomes
in conjunction with hyperthermia therapy holds great promise
to be able to directly measure drug dose concentrations as
well as to non-invasively describe patterns of drug
distribution with MR and PET/SPECT imaging modalities. We
will review the rationale for using this approach and the
potential advantages of having such information available
during and after treatment.},
Key = {Tashjian08}
}
@booklet{Chen08,
Author = {Q. Chen and A. Krol and A. Wright and D. Needham and M. W.
Dewhirst and F. Yuan},
Title = {Tumor microvascular permeability is a key determinant for
antivascular effects of doxorubicin encapsulated in a
temperature sensitive liposome},
Journal = {International Journal Of Hyperthermia},
Volume = {24},
Number = {6},
Pages = {475 -- 482},
Year = {2008},
ISSN = {0265-6736},
Abstract = {Previous data have demonstrated that doxorubicin (DOX)
released from a lysolecithin-containing thermosensitive
liposome (LTSL) can shut down blood flow in a human tumor
xenograft (FaDu) in mice when the treatment is combined with
hyperthermia (HT), suggesting that LTSL-DOX is a potential
antivascular agent. To further understand mechanisms of the
treatment, we investigated effects of LTSL-DOX (5 mg/kg body
weight) plus HT (42C, 1 h) on microcirculation in another
tumor (a murine mammary carcinoma, 4T07) implanted in mouse
dorsal skin-fold chambers and dose responses of tumor (FaDu
and 4T07) and endothelial cells to LTSL-DOX or free DOX with
or without HT. We observed that LTSL-DOX-HT could
significantly reduce blood flow and microvascular density in
4T07 tumors. The antivascular efficacy of LTSL-DOX-HT could
be enhanced through increasing tumor microvascular
permeability of liposomes by using platelet activating
factor (PAF). We also observed that the dose responses of
FaDu and 4T07 to DOX in vitro were similar to each other and
could be enhanced by HT. Taken together, these data
suggested that tumor microvascular permeability was more
critical than the sensitivity of tumor cells to DOX in
determining the antivascular efficacy of LTSL-DOX-HT
treatment.},
Key = {Chen08}
}
%% Neu, John C
@article{9337779,
Author = {Neu, J.C. and Krassowska, W.},
Title = {Singular perturbation analysis of the pore creation
transient},
Journal = {Phys. Rev. E, Stat. Nonlinear Soft Matter Phys.
(USA)},
Volume = {74},
Number = {3},
Pages = {31917 - 1},
url = {http://dx.doi.org/10.1103/PhysRevE.74.031917},
Keywords = {biodiffusion;bioelectric potentials;biomembrane
transport;cellular biophysics;DNA;drug delivery
systems;},
Abstract = {Electroporation, in which electric pulses create transient
pores in the cell membrane, is an important technique for
drug and DNA delivery. Electroporation kinetics is
mathematically described by an advection-diffusion boundary
value problem. This study uses singular perturbation to
derive a reduced description of the pore creation transient
in the form of a single integrodifferential equation for the
transmembrane voltage V(t). The number of pores and the
distribution of their radii are computed from V(t). The
analysis contains two nonstandard features: the use of the
voltage deviation to peel away the strong exponential
dependence of pore creation upon the transmembrane
potential, and the autonomous approximation of the pore
evolution. Comparing the predictions of the reduced equation
with the simulations of the original problem demonstrates
that this analysis allows one to predict with good accuracy
the number and distribution of pores as a function of the
electric pulse strength},
Key = {9337779}
}
%% Neu, Wanda K.
@booklet{Zhao08,
Author = {X. Zhao and D. G. Schaeffer and C. M. Berger and W.
Krassowska and D. J. Gauthier},
Title = {Cardiac Alternans Arising From an Unfolded Border-Collision
Bifurcation},
Journal = {Journal Of Computational And Nonlinear Dynamics},
Volume = {3},
Number = {4},
Year = {2008},
Month = {October},
ISSN = {1555-1423},
Abstract = {Following an electrical stimulus, the transmembrane voltage
of cardiac tissue rises rapidly anti remains at a constant
value before returning to the resting value, a phenomenon
known as an action potential. When the pacing rate of a
periodic train of stimuli is increased above a critical
value, the action potential undergoes a period-doubling
bifurcation, where the resulting alternation of the action
potential duration is known as alternans in medical
literature. Existing cardiac models treat alternans either
as a smooth or as a border-collision bifurcation. However,
recent experiments in paced cardiac tissue reveal that the
bifurcation to alternans exhibits hybrid smooth/nonsmooth
behaviors, which can be qualitatively described by a model
of so-called unfolded border-collision bifurcation. In this
paper, we obtain analytical solutions of the unfolded
border-collision model and use it to explore the crossover
between smooth and nonsmooth behaviors. Our analysis shows
that the hybrid smooth/nonsmooth behavior is due to large
variations in the system's properties over a small interval
of the bifurcation parameter providing guidance for the
development of future models. [DOI: 10.1115/1.2960467]},
Key = {Zhao08}
}
@article{6391846,
Author = {DeBruin, K.A. and Krassowska, W.},
Title = {Modeling electroporation in a single cell. I. Effects of
field strength and rest potential},
Journal = {Biophys. J. (USA)},
Volume = {77},
Number = {3},
Pages = {1213 - 24},
Keywords = {bioelectric phenomena;biological effects of fields;cellular
biophysics;electric field effects;electric
shocks;physiological models;},
Abstract = {This study develops a model for a single cell electroporated
by an external electric field and uses it to investigate the
effects of shock strength and rest potential on the
transmembrane potential V<sub>m</sub> and pore density N
around the cell. As compared to the induced potential
predicted by resistive-capacitive theory, the model of
electroporation predicts a smaller magnitude of
V<sub>m</sub> throughout the cell. Both V<sub>m</sub> and N
are symmetric about the equator with the same value at both
poles of the cell. Larger shocks do not increase the maximum
magnitude of V<sub>m</sub> because more pores form to shunt
the excess stimulus current across the membrane. In
addition, the value of the rest potential does not affect
V<sub>m</sub> around the cell because the electroporation
current is several orders of magnitude larger than the ionic
current that supports the rest potential. Once the field is
removed, the shock-induced V<sub>m</sub> discharges within 2
μs, but the pores persist in the membrane for several
seconds. Complete resealing to preshock conditions requires
approximately 20 s. These results agree qualitatively and
quantitatively with the experimental data reported by
Kinosita et al. for unfertilized sea urchin eggs exposed to
large electric fields},
Key = {6391846}
}
@article{9337779,
Author = {Neu, J.C. and Krassowska, W.},
Title = {Singular perturbation analysis of the pore creation
transient},
Journal = {Phys. Rev. E, Stat. Nonlinear Soft Matter Phys.
(USA)},
Volume = {74},
Number = {3},
Pages = {31917 - 1},
url = {http://dx.doi.org/10.1103/PhysRevE.74.031917},
Keywords = {biodiffusion;bioelectric potentials;biomembrane
transport;cellular biophysics;DNA;drug delivery
systems;},
Abstract = {Electroporation, in which electric pulses create transient
pores in the cell membrane, is an important technique for
drug and DNA delivery. Electroporation kinetics is
mathematically described by an advection-diffusion boundary
value problem. This study uses singular perturbation to
derive a reduced description of the pore creation transient
in the form of a single integrodifferential equation for the
transmembrane voltage V(t). The number of pores and the
distribution of their radii are computed from V(t). The
analysis contains two nonstandard features: the use of the
voltage deviation to peel away the strong exponential
dependence of pore creation upon the transmembrane
potential, and the autonomous approximation of the pore
evolution. Comparing the predictions of the reduced equation
with the simulations of the original problem demonstrates
that this analysis allows one to predict with good accuracy
the number and distribution of pores as a function of the
electric pulse strength},
Key = {9337779}
}
@article{6391847,
Author = {DeBruin, K.A. and Krassowska, W.},
Title = {Modeling electroporation in a single cell. II. Effects of
ionic concentrations},
Journal = {Biophys. J. (USA)},
Volume = {77},
Number = {3},
Pages = {1225 - 33},
Keywords = {bioelectric phenomena;biomembrane transport;electric
shocks;physiological models;},
Abstract = {For pt. I see ibid., vol. 77, p. 1213-24 (1999). This study
expands a previously developed model (described in pt. I) of
a single cell electroporated by an external electric field
by explicitly accounting for the ionic composition of the
electroporation current. The previous model with
non-specific electroporation current predicts that both the
transmembrane potential V<sub>m</sub> and the pore density N
are symmetric about the equator, with the same values at
either end of the cell. The new, ion-specific case predicts
that V<sub>m</sub> is symmetric and almost identical to the
profile from the non-specific case, but N has a profound
asymmetry with the pore density at the hyperpolarized end of
the cell twice the value at the depolarized end. These
modeling results agree with the experimentally observed
preferential uptake of marker molecules at the
hyperpolarized end of the cell as reported in the
literature. This study also investigates the changes in
intracellular ionic concentrations induced around an
electroporated single cell. For all ion species, the
concentrations near the membrane vary significantly, which
may explain the electrical disturbances observed
experimentally after large electric shocks are delivered to
excitable cells and tissues},
Key = {6391847}
}
%% Nicolelis, Miguel A
@article{7951637,
Author = {Wiest, M.C. and Nicolelis, M.A.L.},
Title = {Behavioral detection of tactile stimuli during 7-12 Hz
cortical oscillations in awake rats},
Journal = {Nat. Neurosci. (USA)},
Volume = {6},
Number = {9},
Pages = {913 - 14},
url = {http://dx.doi.org/10.1038/nn1107},
Keywords = {bioelectric potentials;biological techniques;brain;microelectrodes;neurophysiology;touch
(physiological);},
Abstract = {Prominent 7-12 Hz oscillations in the primary somatosensory
cortex (S1) of awake but immobile rats might represent a
seizure-like state1 in which neuronal burst firing renders
animals unresponsive to incoming tactile stimuli; others
have proposed that these oscillations are analogous to human
μ rhythm. To test whether rats can respond to tactile
stimuli during 7-12 Hz oscillatory activity, we trained
head-immobilized awake animals to indicate whether they
could detect the occurrence of transient whisker deflections
while we recorded local field potentials (LFPs) from
microelectrode arrays implanted bilaterally in the S1
whisker representation area. They responded rapidly and
reliably, suggesting that this brain rhythm represents
normal physiological activity that does not preclude
perception},
Key = {7951637}
}
%% Nightingale, Kathryn R
@booklet{Bing09,
Author = {K. F. Bing and G. P. Howles and Y. Qi and M. L. Palmeri and K. R. Nightingale},
Title = {Blood-brain barrier (bbb) disruption using a diagnostic
ultrasound scanner and definity (r) in mice},
Journal = {Ultrasound In Medicine And Biology},
Volume = {35},
Number = {8},
Pages = {1298 -- 1308},
Year = {2009},
Month = {August},
ISSN = {0301-5629},
Abstract = {The objective of this work was to determine whether
diagnostic ultrasound and contrast agent could be used to
transcranially and nondestructively disrupt the blood-brain
barrier (BBB) in mice under ultrasound image guidance and to
quantify that disruption using magnetic resonance imaging
(MRI) and magnetic resonance (MR) contrast agent. Each mouse
was placed under isoflurane anesthesia and the hair on top
of its skull was removed before treatment. A diagnostic
ultrasound transducer was placed in a water bag coupled with
gel on the mouse skull. Definity (ultrasound [US] contrast)
and Magnevist (MR contrast) were injected concurrent with
the start of a custom ultrasound transmission sequence. The
transducer was translated along the rostral-caudal axis to
insonify three spatial locations (2 mm apart) along one half
of the brain for each sequence. T1-weighted MR images were
used to quantify the volume of tissue over which the BBB
disruption allowed Magnevist to enter the brain, based upon
increases in MR contrast-to-noise ratio (CNR) compared with
the non-insonified portions of the brain. Ultrasonic
frequency, pressure and pulse duration, as well as Definity
dose and injection time were varied. Preliminary results
suggest that a threshold exists for BBB opening dependent
upon both pressure and pulse duration (consistent with
reports in the literature performed at lower frequencies). A
range of typical diagnostic frequencies (e.g., 5.0-8.0 MHz)
generated BBB disruption. Comparable BBB opening was noted
with varied delays between Definity injection and
insonification (0-2 min) for a range of Definity
concentrations (400-2400 mu L/kg). The low-pressure, custom
sequences (mechanical index [MI] $<$= 0.65) had minimal
blood cell extravasation as determined by histologic
evaluation. This study has shown the ability of a diagnostic
ultrasound system, in conjunction with Definity, to open the
BBB transcranially in a mouse model for molecules
approximately 0.5 kDa in size. Opening was achieved at
higher frequencies than previously reported and was
localized under ultrasound image guidance. A typical,
ultrasound imaging mode (pulsed wave [PW] Doppler) with
specific settings (transmit frequency = 5.7 MHz, gate size =
15 mm, pulse repetition frequency = 100 Hz, system power =
15\%) successfully opened the BBB, which facilitates
implementation using the most of commercially available
clinical diagnostic scanners. Localized opening of the BBB
may have potential clinical utility for the delivery of
diagnostic or therapeutic agents to the brain. (E-mail:
kdf2@duke.edu) (C) 2009 World Federation for Ultrasound in
Medicine \& Biology.},
Key = {Bing09}
}
@booklet{Palmeri08,
Author = {M. L. Palmeri and M. H. Wang and J. J. Dahl and K. D.
Frinkley and K. R. Nightingale},
Title = {Quantifying hepatic shear modulus in vivo using acoustic
radiation force},
Journal = {Ultrasound In Medicine And Biology},
Volume = {34},
Number = {4},
Pages = {546 -- 558},
Year = {2008},
Month = {April},
ISSN = {0301-5629},
Abstract = {The speed at which shear waves propagate in tissue can be
used to quantify the shear modulus of the tissue. As many
groups have shown, shear waves can be generated within
tissues using focused, impulsive, acoustic radiation force
excitations, and the resulting displacement response can be
ultrasonically tracked through time. The goals of the work
herein are twofold: (i) to develop and validate an algorithm
to quantify shear wave speed from radiation force-induced,
ultrasonically-detected displacement data that is robust in
the presence of poor displacement signal-to-noise ratio and
(ii) to apply this algorithm to in vivo datasets acquired in
human volunteers to demonstrate the clinical feasibility of
using this method to quantify the shear modulus of liver
tissue in longitudinal studies. The ultimate clinical
application of this work is noninvasive quantification of
liver stiffness in the setting of fibrosis and steatosis. In
the proposed algorithm, time-to-peak displacement data in
response to impulsive acoustic radiation force outside the
region of excitation are used to characterize the shear wave
speed of a material, which is used to reconstruct the
material's shear modulus. The algorithm is developed and
validated using finite element method simulations. By using
this algorithm on simulated displacement fields,
reconstructions for materials with shear moduli (mu) ranging
from 1.3-5 kPa are accurate to within 0.3 kPa, whereas
stiffer shear moduli ranging from 10-16 kPa are accurate to
within 1.0 kPa. Ultrasonically tracking the displacement
data, which introduces jitter in the displacement estimates,
does not impede the use of this algorithm to reconstruct
accurate shear moduli. By using in vivo data acquired
intercostally in 20 volunteers with body mass indices
ranging from normal to obese, liver shear moduli have been
reconstructed between 0.9 and 3.0 kPa, with an average
precision of +/- 0.4 kPa. These reconstructed liver moduli
are consistent with those reported in the literature (mu =
0.75-2.5 kPa) with a similar precision (+/- 0.3 kPa).
Repeated intercostal liver shear modulus reconstructions
were performed on nine different days in two volunteers over
a 105-day period, yielding an average shear modulus of 1.9
+/- 0.50 kPa (1.3-2.5 kPa) in the first volunteer and 1.8
+/- 0.4 kPa (1.1-3.0 kPa) in the second volunteer. The
simulation and in vivo data to date demonstrate that this
method is capable of generating accurate and repeatable
liver stiffness measurements and appears promising as a
clinical tool for quantifying liver stiffness.},
Key = {Palmeri08}
}
@booklet{Zhai08,
Author = {L. Zhai and M. L. Palmeri and R. R. Bouchard and R. W.
Nightingale and K. R. Nightingale},
Title = {An integrated indenter-ARFI imaging system for tissue
stiffness quantification},
Journal = {Ultrasonic Imaging},
Volume = {30},
Number = {2},
Pages = {95 -- 111},
Year = {2008},
Month = {April},
ISSN = {0161-7346},
Abstract = {The goal of this work is to develop and characterize an
integrated indenter-ARFI (acoustic radiation force impulse)
imaging system. This system is capable of acquiring matched
datasets of ARFI images and stiffness profiles from c x vivo
tissue samples, which will facilitate correlation of ARFI
images of tissue samples with independently-characterized
material properties. For large and homogeneous samples, the
indenter can be used to measure the Young's moduli by using
Boussinesq's solution for a load on the surface of a
semi-infinite isotropic elastic medium. Experiments and
finite element method (FEM) models were designed to
determine the maximum indentation depth and minimum sample
size for accurate modulus reconstruction using this
solution. Applying these findings, indentation measurements
were performed on three calibrated commercial
tissue-mimicking phantoms and the results were in good
agreement with the calibrated stiffness. For heterogeneous
tissue samples, indentation can be used independently to
characterize relative stiffness variation across the sample
Surface, which can then be used to validate the stiffness
variation in registered ARFI images. Tests were performed on
heterogeneous phantoms and freshly-excised colon cancer
specimens to detect the relative stiffness and lesion sizes
using the combined system. Normalized displacement curves
across the lesion surface were calculated and compared. Good
agreement of the lesion profiles was observed between
indentation and ARFI imaging.},
Key = {Zhai08}
}
@article{fds62247,
Author = {Palmeri ML and Wang MH and Dahl JJ and Frinkley KD and Nightingale
KR},
Title = {Quantifying hepatic shear modulus in vivo using acoustic
radiation force},
Journal = {Ultrasound Med. Biol.(USA)},
Volume = {34},
Number = {4},
Pages = {546-558},
Year = {2008},
Keywords = {biological tissues;biomechanics;biomedical ultrasonics;data
acquisition;phantoms;},
Key = {fds62247}
}
@article{fds62259,
Author = {Zhai L and Palmeri ML and Bouchard RR and Nightingale RW and Nightingale
KR},
Title = {An integrated indenter-ARFI imaging system for tissue
stiffness quantification},
Journal = {Ultrasonic Imaging (USA)},
Volume = {38},
Pages = {95-111},
Year = {2008},
Key = {fds62259}
}
%% Nightingale, Roger W
@article{ISI:000174829200012,
Author = {Nightingale, K and Soo, MS and Nightingale, R and Trahey,
G},
Title = {{Acoustic radiation force impulse imaging: In vivo
demonstration of clinical feasibility}},
Journal = {{ULTRASOUND IN MEDICINE AND BIOLOGY}},
Volume = {{28}},
Number = {{2}},
Pages = {{227-235}},
ISSN = {{0301-5629}},
Abstract = {{The clinical viability of a method of acoustic remote
palpation, capable of imaging local variations in the
mechanical properties of soft tissue using acoustic
radiation force impulse (ARFI) imaging, is investigated in
vivo. In this method, focused ultrasound (US) is used to
apply localized radiation force to small volumes of tissue
(2 mm(3)) for short durations (less than 1 ms) and the
resulting tissue displacements are mapped using ultrasonic
correlation-based methods. The tissue displacements are
inversely proportional to the stiffness of the tissue and,
thus, a stiffer region of tissue exhibits smaller
displacements than a more compliant region. Due to the short
duration of the force application, this method provides
information about the mechanical impulse response of the
tissue, which reflects variations in tissue viscoelastic
characteristics. In this paper, experimental results are
presented demonstrating that displacements on the order of
10 mum can be generated and detected in soft tissues in vivo
using a single transducer on a modified diagnostic US
scanner. Differences in the magnitude of displacement and
the transient response of tissue are correlated with tissue
structures in matched B-mode images. The results comprise
the first in vivo ARFI images, and support the clinical
feasibility of a radiation force-based remote palpation
imaging system. (C) 2002 World Federation for Ultrasound in
Medicine Biology.}},
Key = {ISI:000174829200012}
}
@article{ISI:000261931800012,
Author = {Finan, John D. and Nightingale, Roger W. and Myers, Barry
S.},
Title = {{The Influence of Reduced Friction on Head Injury Metrics in
Helmeted Head Impacts}},
Journal = {{TRAFFIC INJURY PREVENTION}},
Volume = {{9}},
Number = {{5}},
Pages = {{483-488}},
ISSN = {{1538-9588}},
Abstract = {{Objective. Reducing surface friction has been shown to
reduce head injury risk in some scenarios. However, rigid
body mechanics suggests that other scenarios may exist in
which reducing surface friction increases head injury risk.
The goal of this study is to demonstrate that reducing
friction on the surface of a helmet decreases the rotational
acceleration of the head in some scenarios and increases it
in other scenarios and to discuss the implications for
helmet design. Methods. A series of drop tests were
conducted to simulate normal and oblique impacts and assess
head injury risk with conventional helmets and helmets that
had been modified to reduce friction. Results. The low
friction modification had little influence on peak linear
head acceleration or HIC. However, it decreased peak
rotational acceleration by 55\% in one oblique impact
scenario and increased it by 83\% in another oblique impact
scenario. In normal impacts, the low friction modification
had no effect on peak rotational acceleration. Conclusions.
The relationship between rotational acceleration and surface
friction is sensitive to the impact scenario. A single
oblique impact test may be misleading when assessing the
overall performance of a low friction helmet. The
implications of these findings for helmet design are
discussed.}},
Key = {ISI:000261931800012}
}
@article{ISI:000247741300008,
Author = {Chancey, Valeta Carol and Ottaviano, Danielle and Myers,
Barry S. and Nightingale, Roger W.},
Title = {{A kinematic and anthropometric study of the upper cervical
spine and the occipital condyles}},
Journal = {{JOURNAL OF BIOMECHANICS}},
Volume = {{40}},
Number = {{9}},
Pages = {{1953-1959}},
ISSN = {{0021-9290}},
Abstract = {{The center of rotation (COR) of the upper cervical spine
(UCS) is an important biomechanical landmark that is used to
determine upper neck moment, particularly when evaluating
injury risk in the automotive environment. However, neither
the location of the UCS CORs nor the occipital condyles
(OCs), which are frequently the referenced landmark for UCS
CORs, have been measured with respect to known cranial
landmarks. This study determines the CORs using pure bending
(+/- 3.5Nm), 3D digitization, and image analysis. Landmarks
digitized included the OCs, external auditory meatus (EAM),
infraorbital foramen, zygion, nasion, and the foramen
magnum. The centroid of each occipital condylar surface
(area 301 +/- 29.8 mm(2); length 25.4 +/- 3.2 min) was
located 18.4 min posterior, 54.4 mm medial, and 3 1.0 mrn
inferior of the EAM. The UCS CORs were distinct: On average,
OC-C1 CORs (22.5 mm posterior and 22.6 mm inferior to the
left EAM) were superior and more posterior of OCs; C1-C2
CORs (7.4 mm posterior and 46.7 turn inferior to the left
EAM) were inferior and more anterior of OC; and OC-C2 CORs
(17.0 mm posterior and 33.1 mm inferior to the left EAM)
were aligned with OC. There was a statistically significant
difference between the percentage of UCS rotation in C1-C2
and OC-Cl; 45\% of the flexion and 71 \% of the extension
occurred in OC-C1. Details of an anatomical variant with two
pairs of distinct condylar surfaces are also presented. (C)
2006 Elsevier Ltd. All rights reserved.}},
Key = {ISI:000247741300008}
}
@article{ISI:000259558700003,
Author = {Zhai, Liang and Palmeri, Mark L. and Bouchard, Richard R. and Nightingale, Roger W. and Nightingale, Kathryn
R.},
Title = {{An integrated indenter-ARFI imaging system for tissue
stiffness quantification}},
Journal = {{ULTRASONIC IMAGING}},
Volume = {{30}},
Number = {{2}},
Pages = {{95-111}},
ISSN = {{0161-7346}},
Abstract = {{The goal of this work is to develop and characterize an
integrated indenter-ARFI (acoustic radiation force impulse)
imaging system. This system is capable of acquiring matched
datasets of ARFI images and stiffness profiles from c x vivo
tissue samples, which will facilitate correlation of ARFI
images of tissue samples with independently-characterized
material properties. For large and homogeneous samples, the
indenter can be used to measure the Young's moduli by using
Boussinesq's solution for a load on the surface of a
semi-infinite isotropic elastic medium. Experiments and
finite element method (FEM) models were designed to
determine the maximum indentation depth and minimum sample
size for accurate modulus reconstruction using this
solution. Applying these findings, indentation measurements
were performed on three calibrated commercial
tissue-mimicking phantoms and the results were in good
agreement with the calibrated stiffness. For heterogeneous
tissue samples, indentation can be used independently to
characterize relative stiffness variation across the sample
Surface, which can then be used to validate the stiffness
variation in registered ARFI images. Tests were performed on
heterogeneous phantoms and freshly-excised colon cancer
specimens to dete 
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