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PURPOSE - To evaluate the effect of scanner type and calcium measure on the reproducibility of calcium measurements.
MATERIALS AND METHODS - This investigation was approved by the institutional review boards of each study site and by the Institutional Review Board of the Los Angeles Biomedical Research Institute. Informed consent for scanning and participation was obtained from all participants. The study was Health Insurance Portability and Accountability Act compliant. The Multi-Ethnic Study of Atherosclerosis (MESA) is a multicenter observational study of 6814 participants undergoing demographic, risk factor, and subclinical disease evaluations. Coronary artery calcium was measured by using duplicate CT scans. Three study centers used electron-beam computed tomography (CT), and three used multi-detector row CT. Coronary artery calcium was detected in 3355 participants. Three calcium measurement methods-Agatston score, calcium volume, and interpolated volume score-were evaluated. Mean absolute differences between calcium measures on scans 1 and 2, excluding cases for which both scans had a measure of zero, was modeled by using linear regression to compare reproducibility between scanner types. A repeated measures analysis of variance test was used to compare reproducibility across calcium measures, with mean percentage absolute difference as the outcome measure. Rescan reproducibility in relation to misregistrations, noise, and motion artifacts was also examined. Variables were log transformed to create a more normal distribution.
RESULTS - Concordance for presence of calcium between duplicate scans was high and similar for both electron-beam and multi-detector row CT (96%, kappa = 0.92). Mean absolute difference between calcium scores for the two scans was 15.8 for electron-beam and 16.9 for multi-detector row CT scanners (P = .06). Mean relative differences were 20.1 for Agatston score, 18.3 for calcium volume, and 18.3 for interpolated volume score (P < .01). Reproducibility was lower for scans with versus those without image misregistrations or motion artifacts (P < .01 for both).
CONCLUSION - Electron-beam and multi-detector row CT scanners have equivalent reproducibility for measuring coronary artery calcium. Calcium volumes and interpolated volume scores are slightly more reproducible than Agatston scores. Reproducibility is lower for scans with misregistrations or motion artifacts.