Prospective versus retrospective ECG gating for 320-detector CT of the coronary arteries: comparison of image quality and patient radiation dose

Abstract

Purpose To compare image quality and patient radiation dose in a group of patients who underwent 320-detector computed tomography coronary angiography performed with prospective electrocardiogram (ECG) gating with image quality and radiation dose in a group of patients matched for clinical features who underwent 320-detector computed tomographic (CT) coronary angiography performed with retrospective ECG gating. Materials and Methods This study was approved by our institutional human research committee. All patients had clinical indications for coronary computed tomography angiography (CTA). Two independent reviewers separately scored coronary artery segment image quality for 480 cardiac CT studies in prospective group and retrospective group (240 in each group). Reviewer variability was calculated. Estimated effective radiation dose was compared for prospective versus retrospective ECG gating. Results The two groups matched well for clinical characteristics and CT parameters. There was good agreement for coronary artery segment image quality scores between the independent reviewers ( k=0.73). Of the 6408 coronary artery segments scored, there were no coronary artery segments that could not be evaluated in each group. Image quality scores were not significantly different ( P>.05). Mean patient radiation dose was 76.50% lower for prospective gating (4.2 mSv) than for retrospective gating (18.1 mSv) ( P<.01). Conclusion Use of 320-detector CT coronary angiography performed with prospective ECG gating has similar subjective image quality scores but 76.50% lower patient radiation dose when compared with use of retrospective ECG gating.