Abstract:
Despite much advancement, quantitative optimization of cardiac CT has remained an elusive challenge. The purpose of this study was to quantify the stenosis measurement variability introduced by the relative motion of coronary vessels in cardiac CT. Even with general motion vectors of normal coronary vasculature known, relative in-plane motion direction with respect to the source angle during acquisition can be random. The random motion direction results in varying degrees of image degradation and visualized vessel deformation. We simulated CT scans of coronary vessels in motion in both the parallel and orthogonal directions with respect to the x-ray source at the central projection angle. We measured the diameter of the visualized vessel from the reconstructed images using an automated adaptive threshold operator. On average, the variability of all measured vessel attributes (diameter, circularity and contrast) in dual-source acquisition modes were less variable than the vessel attributes for all single-source acquisition modes. This difference was most pronounced at the fastest simulated vessel velocity (16 mm/s). The measurement range for vessel diameter, circularity and contrast were all positively correlated with vessel velocity for the single-source half-scan mode. Motion induced vessel deformation was most extreme when relative motion was directed parallel to the central projection angle of the scan range. Dual-source acquisition remedied the directionally asymmetry by simultaneously acquiring orthogonal projections. The relative direction of vessel motion during cardiac CT remains a significant source of uncertainty in vessel characterization. The methodology enables optimization of CT acquisition and reconstruction for targeted cardiac quantification.
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