Assessment of atherosclerotic plaques in a rabbit model by delayed-phase contrast-enhanced CT angiography: Comparison with histopathology

The aim of this study was to compare delayed-phase computed tomography angiography (CTA) attenuation values with histopathology, in ability to differentiate between fibrous and lipid-rich plaques in an experimental rabbit model. Twelve atherosclerotic rabbits underwent CTA of the abdominal aorta. The scan protocol included early-phase scans (EP), delayed scans at 90 s after contrast injection (DP _90s), delayed scans at 10 min after contrast injection (DP _10min), and delayed scan with saline infusion (DP _Saline). Plaque composition was analyzed by histopathology (% of lipid-rich, fibrous and macrophage areas) and CT attenuation values in Hounsfield units. Using histopathology as the reference standard (n = 119), the overall sensitivity, specificity and accuracy of 64-slice CTA for the detection of plaques was 59, 100 and 79% for the EP scans; 88, 100 and 94% for the DP _90s scans; 81, 100 and 90% for the DP _10min scans; and 53, 100 and 76% for the DP _Saline scans. CT density measurements showed a substantial overlap between fibrous and lipid-rich plaques, and poor correlations with the percentage of macrophage areas in both fibrous and lipid-rich plaques (r = 0.408, and r = 0.333). In delayed-phase 64-slice CTA, DP _90s images have the best diagnostic performance for the detection of aortic plaques.