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

Abstract

[한글]

[영문]Non-invasive imaging tools that enable to detect and characterize the composition of plaques are clinically desirable. Recently, it was known that atherosclerotic plaque shows enhancement on CT angiography (CTA) after contrast administration. The purpose of this study was to assess the capability of multi-phase CTA in the characterization and quantification of atherosclerotic plaques of aorta in comparison with histopathology in an experimental rabbit model. Twelve atherosclerotic rabbits underwent multi-phase CTA of the abdominal aorta. The scan protocol included early phase scan (EP), delayed scan at 90 sec after contrast injection (DP90s), delayed scan at 10 min after contrast injection (DP10min) and delayed scan with saline infusion (DPSaline). Plaque composition was analyzed according to histopathology (% of lipid-rich, fibrous and macrophage areas) and CT attenuation values (Hounsfield Unit [HU]). For each plaque, the maximum area of lumen, vessel, and plaque were measured. The correlation between CTA and histopathologic measurements was determined using Pearson’s correlation coefficient.Using histopathology as the reference standard (n=119, aortic plaques), the overall sensitivity, specificity and accuracy of 64-slice CTA for the detection of plaques were 59%, 100% and 79% for the EP scan, 88%, 100%, and 94% for the DP90s scan, 81%, 100% and 90% for the DP10min scan and 53%, 100% and 76% for the DPSaline scan, respectively. CT density measurements were significantly different between fibrous plaques and lipid-rich plaques (p < 0.05). However, the CT density measurements showed substantial overlap between fibrous and lipid-rich plaques. When we divided aortic plaques into two groups according to the percentage of macrophage area using a cut-off value of 50%, the CT density values were not significantly different between the macrophage-rich plaques and the macrophage-poor plaques (69 ± 15 HU versus 64 ± 11 HU, p = 0.294). The correlation coefficients for the measurements of the lumen, vessel wall, and plaque area between the CTA and histopathologic results were 0.767, 0.783, and 0.739, respectively.In conclusion, among the phases of 64-slice CTA, DP90s imaging has the best diagnostic performance in the detection of aortic plaques and allows quantification of aortic plaques. However, further classification of non-calcified plaques into vulnerable or stable plaques by CT density measurements is not reliable.