Correlation between MDCTA and Carotid Plaque Histological Heterogeneity: A Pilot Study.

Abstract

The aim of this pilot study was to identify multidetector computed tomography angiography (MDCTA) features that may help identify carotid atherosclerotic plaques (CAPs) with severe histological heterogeneity. Thirty-one CAPs (9 symptomatic) were evaluated histologically using a semiquantitative scale. The CAPs were assessed for the presence of ulceration, lipids, fibrosis, thrombotic deposits, haemorrhage, neovascularisation, and inflammation. A CAP presenting at least five of these histological features was defined as a severe heterogeneous plaque (Group A); in all other cases it was defined as a mild to moderate heterogeneous plaque (Group B). The non-calcified plaque tissue was segmented in pre-operative MDCTA. Median and mean intensity and percentages of soft tissue voxels with a value smaller than or equal to certain thresholds (from 20 HU to 200 HU with a constant distance of 20 HU) were calculated. Comparison of intensity measurements was analysed by Mann-Whitney U test and receiver operating characteristic (ROC) analysis. In order to assess the method reliability, values showing better performance were compared using the Wilcoxon signed rank test and k-Cohen test according to ROC analysis. According to histological analysis 18 CAPs were classified as belonging to Group B and 13 to Group A. The percentages of soft tissue with density ≤ 40 (TH_40), 60 (TH_60), 80 (TH_80), and 100 HU (TH_100) were statistically significantly greater in plaques of Group A (respectively p = .016, p = .002, p = .001, p = .007). The mean (p = .025) and median (p = .014) intensity were statistically significantly lower in the plaques of Group A. TH_60 and TH_80 showed the greatest accuracy (0.81) with similar performance in term of AUC and sensitivity/specificity (TH_60: 0.82, 0.62, 0.94; TH_80: 0.83, 0.69, 0.89, respectively, for AUC, sensitivity and specificity). Reliability analysis showed good repeatability and reproducibility of these measurements. The findings have demonstrated lower density of the non-calcified tissue in the plaques of Group A with higher TH_60 and TH_80 soft tissue percentages with respect to CAPs of Group B.