Purpose: To compare image quality and patient radiation dose in a group of patients who underwent 64-detector computed tomography (CT) coronary angiography performed with prospective electrocardiographic (ECG) gating with image quality and radiation dose in a group of patients matched for clinical features who underwent 64-detector CT coro-nary angiography performed with retrospective ECG gating.
Materials and Methods: Institutional review board approval was obtained for this HIPAA-compliant study, and the informed consent re-quirement was waived due to the retrospective study de-sign. Two independent reviewers separately scored coro-nary artery segment image quality and overall image qual-ity for 100 cardiac CT studies (50 in each group). Interobserver variability was calculated. Patient radiation dose for the actual examination z-axis length was re-corded, and a normalized dose was calculated for a 12-cm z-axis length of a typical heart.
Results: The two groups matched well for clinical characteristics and CT parameters. There was good agreement for coro-nary artery segment image quality scores between the independent reviewers (K = 0.72). Of the 1253 coronary artery segments scored, the number of coronary artery segments that could not be evaluated in each group was similar (1.1% [seven of 614] in the prospective group vs 1.5% [10 of 647] in the retrospective group, P = .53). Image quality scores were not significantly different when matched for chest cross-sectional area (P > .05). Mean patient radiation dose was 77% lower for prospective gat-ing (4.2 mSv) than for retrospective gating (18.1 mSv) (P< .01).
Conclusion: Use of 64-detector CT coronary angiography performed with prospective ECG gating has similar subjective image quality scores but 77% lower patient radiation dose when compared with use of retrospective ECG gating.