Electron-beam CT: The effect of using a correction function on coronary artery calcium quantitation

Purpose; The purpose of the study was to determine if use of a correction function derived from a phantom with known calcium density reduces variation in coronary artery calcium scores measured with electron-beam computed tomography (CT) and to evaluate the influence of body girth, as measured by body mass index (BMI), on coronary artery calcium-score variability in a clinical screening cohort. Materials and Methods. Two hundred fifty consecutive patients underwent two electron-beam CT examinations with a standardized phantom. Region-of-interest (ROI) measurements of the phantom were correlated with the patient BMI. In a subset of 28 patients with low but positive coronary artery calcium scores, ROI values of the phantom were used as a correction for signal attenuation. Results. Patient BMI was not significantly correlated to Signal attenuation. Application of a correction function resulted in a small but insignificant decrease in interscan coronary artery calcium-score variation, The interscan coronary artery calcium score variation was 24.5% +/- 23.9; it decreased to 24.3% +/- 21.6 with use of the 75 mg/cm(3) portion of the phantom and to 22.2% +/- 21.4 with use of the 150 mg/cm(3) portion of the phantom. Conclusion. The use of a coronary artery calcium phantom does not reduce interscan variation sufficiently to warrant regular clinical usage. Interscan variation in the coronary artery calcium score is not significantly influenced by patient BMI.