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Purpose: To determine the reproducibility, accuracy, and predictors of accuracy of computed tomography (CT) angiography to detect and characterize coronary atherosclerotic plaque as compared with intravascular ultrasound. Methods: Ten ex vivo human coronary arteries were imaged in a moving phantom by dual-source CT (collimation: 0.6 mm, reconstructed slice thickness: 0.4 mm) and intravascular ultrasound (IVUS). Coregistered crosssections were assessed at 0.4 mm intervals for the presence and composition of atherosclerotic plaque (noncalcified, mixed, and calcified) on CT and IVUS by independent readers to determine reader agreement and diagnostic accuracy. Quantitative measurements of lumen and plaque area, plaque eccentricity, and intimal thickness on IVUS were used to determine predictors for the detection of noncalcified plaque by CT. Results: Within 1002 coregistered cross-sections, the interobserver agreement to detect plaque on CT was K = 0.48, K = 0.42, and K = 1.00 for noncalcified, mixed, and calcified plaque; respectively. The sensitivity and specificity of CT was 57% out of 84% for noncalcified, 32% of 92% for mixed, and 56% of 93% for calcified plaque when compared with IVUS; respectively. Misclassification occurred in 68% of mixed and 43% of noncalcified plaques. The odds of detecting noncalcified plaque in CT independently increased by 56% (95% CI: 47%-77%, P < 0.0001) with every 0.1 mm increase in maximum intimal thickness as measured by IVUS. Detection rate for noncalcified plaques was poor for plaques 1 mm maximal intimal thickness (90%). Conclusion: Reader agreement and diagnostic accuracy for the detection of coronary atherosclerotic plaque vary with plaque composition. Intimal thickness independently predicts detection of noncalcified plaque by CT with excellent sensitivity for >1 mm thick plaques.

There is ample evidence that the development of acute coronary syndrome is linked to the presence of lipid-core, necrotic plaque. However, there is little information on the natural history of lipid-core plaques in humans. A close link between structural changes of atherosclerotic plaques over time to the local shear stress conditions in the arterial system has been reported.1 Although low shear stress is recognized for its proatherogenic impact on the endothelium,1 its role in plaque composition, destabilization, and rupture is less clear. The current paradigm postulates that low shear stress is a necessary condition for plaque accumulation. However, once lumen narrowing occurs because of plaque, local shear stress increases.2 We describe an approach that allows studying the interaction of lipid-core plaque accumulation and local shear stress in a correct anatomic 3D reconstruction of coronary arteries in living patients. A 61-year-old man with a history of myocardial infarction and stenting of the right coronary …