Cross-Sectional Validation of a Novel Computed Tomography-Based Carotid Mean Calcium Density Measurement

BACKGROUND: The purpose of this study was to validate a technique for measuring mean calcium density and to determine associations of cardiovascular risk factors with carotid calcium density. METHODS AND RESULTS: We performed a cross-sectional study in a random sample of 100 stroke-free participants from the population-based Rotterdam Study. The mean calcium density of the combined left and right carotid bifurcations was quan-tified with a threshold of 130 Hounsfield Units (HU) using a novel density technique. To validate the methodology, carotid calcium volumes acquired using the technique in the current study were compared with measurements computed using dedicated clinical software (semiautomatic technique based on a threshold of ≥130 HU). Next, we investigated the associations of participant demographics, total calcium volume, and known cardiovascular risk factors (hypertension, diabetes, hypercholesterolemia, obesity, and smoking status) with the newly derived mean carotid calcium density measurement using linear regression analyses. Calcium volumes obtained with the 2 methods showed a high agreement (intraclass correlation coefficient=0.99, P<0.001), underlining the validity of the density technique. The total calcium volume was statistically significantly associated with the mean calcium density (cardiovascular risk factors adjusted model (B: 0.48 [95% CI, 0.30– 0.66], P<0.001). We also found an association between hypercholesterolemia and mean calcium density (0.46 [0.09– 0.83], P=0.017). No other significant associations were found between participant demographics or cardiovascular risk factors and mean carotid calcium density. CONCLUSIONS: We demonstrated the feasibility of a carotid calcium density measurement technique. The data warrant a subsequent longitudinal study to determine the association between carotid calcium density and the risk of cerebrovascular events.