Carotid Plaque Calcification Attenuation Characteristics are Associated with Intraplaque Hemorrhage Volumes: A 3D Segmentation-Based Analysis

Background and PurposeDespite the high prevalence of plaque calcifications in carotid atherosclerosis, the association between morphologic and attenuation features of calcifications and intraplaque hemorrhage (IPH) remains unclear. MethodsCarotid bifurcation calcific plaques were identified on neck CTAs from patients with unilateral anterior circulation ischemic stroke consistent with embolic stroke of undetermined source. Plaque calcifications were manually segmented using 3D Slicer to measure volume, surface area, shape, and attenuation (Hounsfield Units (HU)) characteristics. IPH volume (IPHvol) was quantified using a semi-automated software. A linear mixed regression model evaluated associations between calcification features and IPHvol, adjusting for sex, age, and cardiovascular risk factors. An interaction term between calcification volume and attenuation was included after dichotomizing attenuation (>924HU) and volume (>30mm3) as high versus low based on median values. ResultsFrom 70 patients (median age 68 years, 50% female), 116 calcific plaques containing 269 plaque calcifications were analyzed. Adjusting for age, cardiovascular risk factors and plaque calcification features, being female showed lower IPHvols compared to males (mean ratio 0.34, p=0.002). A significant interaction between calcification volume and attenuation emerged (p=0.042). Among plaques with low volumes (<30mm3) of plaque calcifications, plaques with low-attenuation (<924HU) calcifications showed 5.53 times higher IPHvols than plaques with high-attenuation calcifications (p=0.003). Among plaques with high-attenuation calcifications (>924HU), plaques with high volumes of these calcifications showed 4.40 times higher IPHvols compared to low-volumes of high-attenuation calcifications (p=0.011). ConclusionsPlaque calcification attenuation characteristics are associated with IPHvols. Beyond presence or volumes of plaque calcifications, calcification attenuation characteristics should be considered when evaluating unstable plaque components.