Assessment of image quality and radiation dose in prospective ECG-triggered coronary CT angiography compared with retrospective ECG-gated coronary CT angiography

We sought to determine the cut-off point of the average heart rate (HR) and HR differences in obtaining diagnostic image quality using prospective electrocardiographically-triggered (PT) coronary computed tomographic angiography (CCTA) and to compare image quality and radiation dose for CCTA obtained with PT CCTA and retrospective electrocardiographically-gated (RG) CCTA. A total of 178 patients who were referred for CCTA were enrolled in the study. Two independent radiologists evaluated subjective image quality. The non-diagnostic coronary segments were 32 of 1,226 segments (2.6%) for PT CCTA and 12 of 1,346 segments (0.9%) for RG CCTA (P < 0.001). The mean image quality scores for PT CCTA and RG CCTA were 3.82 +/- 0.29 and 3.93 +/- 0.14, respectively. The mean radiation dose of patients that underwent PT CCTA was 3.83 +/- 0.84 mSv and RG CCTA 10.7 +/- 2.70 mSv. For patients who underwent PT CCTA, image quality was inversely related to HR (56.5 +/- 4.3 bpm; r = 0.38; P < 0.001) and HR differences (2.8 +/- 2.7 bpm; r = 0.49; P < 0.001). With the use of receiver operator characteristic analysis, a cut-off HR of 57 bpm (58% sensitivity, 67% specificity) and HR difference of 6 bpm (93% sensitivity, 46% specificity) were the best threshold for the prediction of diagnostic image quality. In patients with a regular, low HR, PT CCTA offers diagnostic image quality and substantially reduces effective radiation compared with the use of RG CCTA with dose modulation.