Computed tomography detection of carotid calcium and subclinical carotid atherosclerosis

Computed tomography (CT) detection of coronary calcium has become a popular technique for assessing coronary atherosclerosis. Whether CT detection of carotid calcium could similarly assess carotid atherosclerosis is unknown. We thus performed a study evaluating the feasibility of carotid calcium scoring by CT. We also looked for an association between carotid calcium and subclinical carotid atherosclerosis. Subjects (n = 876) underwent non-contrast CT scanning of their carotid arteries. Carotid calcium was quantified by the Agatston method. Stenoses were detected by subsequent CT angiography. Significant subclinical atherosclerosis was defined by the presence of a ≥30% carotid stenosis. The frequency of a ≥30% carotid stenosis was then analyzed as a function of carotid calcium scores and various cardiovascular risk factors. CT detection of carotid calcium was feasible, robust, and reliable. Significant univariate associations for a ≥30% carotid stenosis included age (P < 0.001), diabetes (P = 0.02), hypertension (P = 0.01), and the carotid calcium score (P < 0.001). Those with a ≥30% carotid stenosis exhibited a median (25th, 75th percentile) carotid calcium score of 153 (19, 489), while those without a ≥30% carotid stenosis had a median (25th, 75th percentile) carotid calcium score of 0 (0, 89). Conversely, when no carotid calcium was detected, there was a low (1%) frequency of significant carotid atherosclerosis. The frequency of a ≥30% carotid stenosis increased as the carotid calcium score increased (P < 0.001 for trend). This association remained significant after adjustment for age, hypertension, diabetes, hyperlipidemia, and tobacco use. CT detection of carotid calcium can assess the burden of carotid atherosclerosis.