Coronary calcium quantification using various calibration phantoms and scoring thresholds

Rationale and Objectives: To compare scoring threshold and calibration method-dependent accuracy and variability of coronary calcium measurements by multidetector computed tomography (MDCT). Methods: Ninety-five subjects were scanned with MDCT. We calculated Agatston score and volume score. Mineral mass (MM) was calculated using patient-based and scanner-based calibration methods. Accuracy of calibration was validated using artificial calcium cylinders. Results: Patient-based and scanner-based calibration permitted accurate quantification of artificial calcium cylinders (bias: 0 mg and -2 mg). In the subjects, the mean relative difference of MM measurements performed at 90 and 130 Hounsfield units threshold (59%) was lower than for Agatston score (94%) and volume score (109%; P<0.05). Patient-based and scanner-based calibration yielded systematically different MM measurements (bias: 22%). Conclusions: MM lowers threshold-dependent variability of coronary calcium measurements. Patient-based and scanner-based calibration allows accurate calcium quantification ex vivo but reveal systematic differences in subjects. Patient-based calibration may better account for subject size and composition.