Radiation dose reduction and coronary assessability of prospective electrocardiogram-gated computed tomography coronary angiography: comparison with retrospective electrocardiogram-gated helical scan.

OBJECTIVES: The aim of this study was to evaluate radiation dose and coronary assessability of a prospective electrocardiogram (ECG)-gated scan by 64-slice multidetector (row) computed tomography (MDCT)-coronary angiography (CA) compared with a retrospective ECG-gated helical scan.

BACKGROUND: The 64-slice MDCT-CA has been widely used; however, a high radiation dose by 64-slice MDCT-CA has been reported. Prospective ECG-gated scan using "step-and-shoot" protocol can reduce radiation exposure effectively.

METHODS: MDCT-CA was performed in 229 consecutive patients. Fifty-six patients were excluded because of higher heart rates of >65 beats/min; of patients with heart rates
RESULTS: Coronary assessability of helical scan was 95.5% (1,303 of 1,364 segments), while that of prospective gating was 96.6% (1,053 of 1,089 segments), showing similar coronary assessability (p = 0.14). Sensitivity and specificity for coronary obstructive and occlusive lesions in the assessable segments were 97.0% (162 of 167) and 97.6% (1,109 of 1,136) by helical scan, while those of prospective gating were 96.4% (81 of 84, p = 0.84) and 98.5% (955 of 969, p = 0.12), respectively. Effective doses of helical scan and prospective gating were 21.1 +/- 6.7 mSv and 4.3 +/- 1.3 mSv, respectively (p < 0.0001), showing that prospective gating decreased radiation dose by 79% compared with that of helical scan.

CONCLUSIONS: MDCT-CA by prospective gating showed equivalent coronary assessability and diagnostic accuracy with decreased radiation dose in comparison with a retrospective ECG-gated helical scan with tube current modulation.