Computed tomography analysis of vulnerable carotid atherosclerotic plaque and relationship to clinical characteristics

Objective The presence of atherosclerotic plaque components such as lipid rich necrotic core and intraplaque haemorrhage is associated with increased plaque vulnerability, and may be used to stratify the risk of future cerebrovascular events. Our aim was to investigate the relationship between selected carotid plaque components imaged with CTA, patient characteristics, and clinical outcomes. Methods Symptomatic patients underwent carotid CTA as part of the BIOVASC study. Images were analysed for plaque volume composition with a semi-automatic Hounsfield Unit (HU)-based algorithm. Plaque components were classified based on their attenuation values: lipids 131 HU. Parametric and non-parametric tests were performed to compare plaque measurements to clinical characteristics and outcomes. Results One-hundred and two symptomatic carotids were analysed (avg. age 69y, 54.9% Male, 29.4% severe stenosis). Mean plaque volume was 480±230 mm 3 , and the mean LRNC volume was 170±100 mm 3 . A difference in LRNC volume was identified between moderate and severe stenosis (190–150 mm 3 , p=0.012). Regression analysis showed that age and gender may predict increased plaque volume (p<0.001). A trend for reduced mean plaque LRNC was identified in patients receiving statins (130-210 mm 3 , p=0.08). Intra-reader reliability showed good agreement (0.62-0.78, p<0.001) between CTA plaque measurements. Conclusions In-vivo CTA plaque volume composition assessment is feasible with good intra-reader reliability. Our findings suggest that CTA-HU measurements may be used to provide improved mechanistic and diagnostic insights into atherosclerotic disease, and facilitate the quantification of selected plaque components whose presence may be associated with increased plaque vulnerability. Key Points Plaque CTA Hounsfield Unit (HU) measurement and segmentation techniques can provide improved mechanistic and diagnostic insights into atherosclerotic disease. Plaque components characterisation using CTA HU measurements may help clinicians to identify patients presenting with high-risk vulnerable plaque. CTA plaque volume composition assessment is feasible with good reliability observed between measurements taken at different time-points.