Assessment of coronary atherosclerosis using intravascular ultrasound and multidetector computed tomography.

摘要

This work describes four contributions to the assessment of coronary atherosclerosis in humans using intravascular ultrasound (IVUS) and multidetector computed tomography (MDCT). First, an automated segmentation system for IVUS is presented. Second, a fully automated analysis system for MDCT, including segmentation and plaque analysis, is presented. Third, a quantitative comparison of the lumen, vessel, and plaque indices measured by IVUS and MDCT is detailed. Lastly, a proof-of-concept study investigating whether coronary vasodilation may be measured by MDCT is documented.;The IVUS segmentation system uses a globally optimal, three-dimensional approach in which multiple levels of knowledge are combined and optimized using a graph cut technique. The combination of cost function terms allows for a robust segmentation, with the ability to learn from previous and future examples. A fully functional software tool using the described algorithms has been implemented, and requires no user interaction to obtain a result.;The MDCT analysis system segments the lumen and vessel wall with subvoxel accuracy, after which a plaque characterization algorithm identifies locations of noncalcified and calcified plaques in the vessel wall. The plaque characterization process accurately identifies a high percentage of known plaques and is one of the first utilities of its kind. This group of tools was also built into a fully functional software tool, and the analysis runs completely independent of user input.;Analysis of quantitative indices generated by both analysis programs leads to the conclusion that luminal measurements are quite reproducible. While generally good, the measurements of vessel and plaque size do not reproduces as well. The reasons for the weaker reproducibility of the vessel and plaque indices are not completely understood at this time, but may be related to the resolution of the scanner, the selection of patients used for testing, or a combination of these and other factors.;Vasodilation was shown to be visible and quantifiable using MDCT in an ovine model. Statistically significant increases in lumen size were measured using the developed analysis techniques. This success, if translated to human subjects, may become a useful noninvasive diagnostic for nonocclusive coronary heart disease and early atherosclerosis.