Coronary Artery Calcium Scoring on Dedicated Cardiac CT and Noncardiac CT Scans

Coronary artery calcium (CAC) is a specific marker of subclinical coronary atherosclerosis and is strongly associated with short- and long-term atherosclerotic cardiovascular disease (ASCVD) risk. Although noncontrast electrocardiographically gated cardiac CT is the reference standard for quantification of CAC (approximately 1 mSv), studies have shown that CAC can also be qualitatively interpreted and quantified on noncardiac chest CT scans with similar prognostic value. While use of dedicated CAC scans is increasing, measurement of incidental CAC represents a major untapped opportunity for ASCVD prevention, given that nearly 20 times more chest CT examinations are performed annually in the United States than dedicated CAC scans. Incidental measurement of CAC at chest CT incurs no additional cost or radiation for patients and can identify those with significant CAC burden who may be inadequately treated with ASCVD risk reduction therapies. This review outlines the fundamentals of CAC scoring, with a focus on detection and quantification of incidental CAC. It details the technical approaches and challenges of incidental CAC assessment and provides recommendations for routine reporting, clinical advisories, and subsequent patient management. The review also presents first-hand experiences from a large academic medical center's initiative to standardize incidental CAC reporting. Future directions include the use of artificial intelligence to automate both basic and advanced CAC interpretation.