Utility of Dual-Layer Spectral Detector CTA to Characterize Carotid Atherosclerotic Plaque Components: An Imaging-Histopathology Comparison in Patients Undergoing Endarterectomy.

Abstract

<b>BACKGROUND.</b> The composition of noncalcified portions of carotid atherosclerotic plaque is an important marker of plaque vulnerability and ischemia risk. <b>OBJECTIVE.</b> The purpose of this study was to assess the utility of dual-layer spectral detector CTA (DLCTA) parameters for characterization of carotid plaque components with histologic results from carotid endarterectomy as the reference. <b>METHODS.</b> Seven patients (five men, two women; mean age, 61.6 ± 8.5 [SD] years) with carotid plaque awaiting carotid endarterectomy were prospectively enrolled and underwent preoperative supraaortic DLCTA. A neuroradiologist and pathologist performed joint slice-by-slice review of histologic slices of resected plaques and CTA images. With the use of anatomic landmarks, ROIs were placed on noncalcified components (lipid-rich necrotic core [LRNC], intraplaque hemorrhage [IPH], fibrous tissue, loose matrix) on CTA images and compared with corresponding histologic slices. For each ROI, attenuation was recorded for conventional polyenergetic images (CT_PI) and virtual monoenergetic images with energy ranging from 40 to 140 keV (CT_40-140keV), attenuation spectrum curve slope was calculated, and <i>Z</i>-effective value (representing effective atomic number) was recorded. DLCTA parameters were compared among plaque components. <b>RESULTS.</b> Seven plaques with a total of 65 slices and 364 ROIs (159 fibrous tissue, 96 LRNC, 86 loose matrix, 23 IPH) were analyzed. All parameters (CT_PI, CT_40-140keV, slope from 40 to 140 keV, <i>Z</i>-effective value) had significant differences between LRNC and the other components (all <i>p</i> < .001). For example, mean CT_PI was 37.1 ± 15.1 HU for LRNC, 58.4 ± 21.6 HU for IPH, 69.7 ± 20.5 HU for fibrous tissue, and 69.6 ± 19.6 HU for loose matrix. Mean CT_40keV was 28.1 ± 36.7 HU for LRNC, 87.5 ± 48.9 HU for IPH, 106.3 ± 47.5 HU for fibrous tissue, and 102.6 ± 48.0 HU for loose matrix. AUC for differentiating LRNC from other components was highest (0.945) for CT_40kev and decreased with higher energy; AUC for CT_PI was 0.908. CT_40kev also had highest accuracy (90.4%); at a cutoff of 55.7 HU, CT_40kev had 88.5% sensitivity and 91.0% specificity. For differentiating IPH from fibrous tissue and loose matrix, AUC was highest at 0.652 for CT_PI and 0.645 for CT_40kev. <b>CONCLUSION.</b> DLCTA showed strong performance in differentiating LRNC from other noncalcified plaque components; CT_40kev had highest accuracy, outperforming CT_PI. <b>CLINICAL IMPACT.</b> DLCTA parameters may help characterize carotid plaque composition as a marker of vulnerable plaque and ischemia risk.