Rationale and Objectives. The purpose of this prospective study was to assess image noise and variability in repeated coronary artery calcium (CAC) scoring on low-dose prospective electrocardiographically-triggered 64-slice multidetector computed tomography.
Materials and Methods. Patients (n = 115) suspected of having coronary artery disease were scanned twice, using a tube current of 10 X body mass index mA. The standard deviation (SD) of the computed tomographic value in the ascending aorta and (mean + 2 X SD) were obtained. Repeated CAC scores (Agatston, volume, and mass) were measured by two observers, and the interscan and interobserver variability were determined.
Results. The mean tube current used was 246 � 36 mA. The mean tube current-time product and mean estimated effec�tive dose were 57 � 8 mA and 0.9 � 0.2 mSv, respectively. The SD and (mean + 2 X SD) computed tomographic val�ues in the ascending aorta were 16 � 3 and 75 � 10 Hounsfield units, respectively. Repeated CAC scores were correlated (r2 = 0.995-0.998). The interscan variability for observer 1 and observer 2, respectively, were 13% and 13% for Agatston score, 12% and 11% for volume, and 11% and 11% for mass. The interobserver variability for scan 1 and scan 2, respec�tively, were 3% and 3% for Agatston score, 5% and 3% for volume, and 3% and 3% for mass.
Conclusion. Low-dose prospective electrocardiographically-triggered 64-slice multidetector computed tomography shows low interscan and interobserver variability on CAC scoring while maintaining low image noise.