Variability of Repeated Coronary Artery Calcium Scoring and Radiation Dose on 64-slice and 16-slice CT by Prospective Electrocardiograph-triggered Axial and Retrospective Electrocardiograph-gated Spiral CT : A Phantom Study
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Rationale and Objectives: To compare coronary artery calcium scores, the variability and radiation doses on 64-slice and 16-slice CT scanners by both prospective electrocardiograph (ECG)-triggered and retrospective ECG-gated scans.
Materials and Methods: Coronary artery models (n=3) with different plaque CT densities (~240 HU, ~600 HU and ~1000 HU) of four sizes (1 mm, 3 mm, 5 mm and 10 mm in length) on a cardiac phantom were scanned three times in 5 heart rate sequences. The tube current-time-products were set to almost the same on all four protocols (32.7 mAs for 64-slice prospective and retrospective scans, 33.3 mAs for 16-slice prospective and retrospective scans). Slice-thickness was set to 2.5 mm in order to keep the radiation dose low. Overlapping reconstruction with 1.25 mm increment was applied on the retrospective ECG-gated scan.
Results: The coronary artery calcium scores were not different between the four protocols (one-factor ANOVA, Agatston; p=0.32, volume; p=0.19 and mass; p=0.09). Two-factor factorial ANOVA test revealed that the interscan variability was different between protocols (p<0.01) and scoring algorithms (p<0.01). The average variability of Agatston/volume/mass scoring and effective doses were 64-slice prospective scan: 16%/15%/11% and 0.5 mSv, 64-slice retrospective scan: 11%/11%/8% and 3.7 mSv, 16-slice prospective scan: 20%/18%/13% and 0.6 mSv & 16-slice retrospective scan: 16%/15%/11% and 2.9 to 3.5 mSv (depending on the pitch).
Conclusions: Retrospective ECG-gated 64-slice CT showed the lowest variability. Prospective ECG-triggered 64-slice CT, with low radiation dose, shows low variability on coronary artery calcium scoring comparable to retrospective ECG-gated 16-slice CT.
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Copyright (c) 2008 AUR Published by Elsevier Inc.