Associations between pericarotid fat density and image-based risk characteristics of carotid plaque

•The associations between PFD and different carotid plaque risk characteristics were evaluated.•PFD was significantly associated with a high risk of AHA VI plaque, IPH, and TRFC.•The simplified PFD measurement may be used to predict the vulnerability of carotid plaque. In this study, we aimed to evaluate the associations between pericarotid fat density (PFD) and various risk characteristics of carotid plaque. We retrospectively evaluated consecutive patients who were subjected to both high-resolution MRI and carotid artery CT angiography CTA at our institution between January 2016 and April 2021. The section of the carotid artery with the most severe lumen stenosis was selected from each patient for analysis. Two separated regions of interest (ROI) (each with an area of 2.5 mm2 and located at least 1 mm from the outer margin of the carotid artery wall) were defined in the perivascular fat tissue. The mean value of PFD (mean HU) was measured on the plaque side and the same axial non-plaque side. Then, the bilateral difference (D-value HU) was calculated (plaque side mean HU minus non-plaque side mean HU). According to carotid plaque risk characteristics (American Heart Association VI type [AHA VI], intraplaque hemorrhage [IPH], thinning and/or rupture of the fibrous cap [TRFC], lipid-rich necrotic core [LRNC], and calcification [CA]), the associations between PFD and five different risk characteristic subgroups were analyzed. The Student’s t-test, Mann-Whitney U test, and Chi-square test were used to compare differences between different risk subgroups. Receiver operating characteristic (ROC) curve analysis was used to evaluate the predictive efficacy of PFD for carotid plaque risk characteristics. P