Coronary CT Angiography and the Napkin-ring Sign Indicates High-Risk Atherosclerotic Lesions

Coronary computed tomography angiography (CCTA) is used extensively nowa‐ days as a non-invasive imaging method for the evaluation of patients suspected of coronary artery disease, providing data on calcium burden, the presence of coro‐ nary artery stenoses, but also, more recently, on coronary atherosclerotic plaque morphology and composition. Plaque morphology analysis by CCTA aims to accu‐ rately identify vulnerable plaques, in an attempt to reduce the number of ischemic events triggered by high-risk atherosclerotic lesions. Recent research provides CCTA descriptions of vulnerable plaques and a particular radiological sign shows promising perspectives. The napkin-ring sign refers to a rupture-prone plaque in a coronary artery, comprising a necrotic core covered by a thin cap fibro-atheroma. The napkin-ring sign is described on CCTA in cross-sectional images of coronary arteries as a central low-attenuation area surrounded by an open ring area of high attenuation, having a high specificity and positive predictive value for the presence of advanced lesions. These lesions have been designated as vulnerable plaques, in‐ dicating an increased probability of rupture, and were shown to correlate with a higher incidence of cardiovascular events. In acute coronary syndromes, the loca‐ tion of the napkin-ring sign was shown to correspond to the culprit lesions. The aim of the current paper is to provide an overview of the current literature on available methods for quantitative measurement of atherosclerotic plaque features from CCTA and to discuss the clinical implications of the napkin-ring sign as detected by CCTA.