First experience with 320-row multidetector CT coronary angiography scanning with prospective electrocardiogram gating to reduce radiation dose

BackgroundThe 320-row multidetector CT (MDCT) provides the capability for prospective electrocardiogram-gated cardiac CT angiography.ObjectiveWe assessed the effective radiation doses of MDCT with a 320-row detector volume scanner.MethodsTwo hundred patients underwent clinically directed cardiac scanning (100 kVp, n = 9 or 120 kVp, n = 191; range, 300–580 mA). Effective radiation dose (in mSv) was estimated from extended dose-length product. For heart rates (HRs) <65 beats/min, exposure phase was 65% up to the end of R wave of the cardiac cycle, using a one-heart beat acquisition and half-scan reconstruction. HRs from 66 to 79 beats/min and ≥80 beats/min were scanned with either 2- or 3-heart beat acquisitions, respectively. Patients with arrhythmias were not excluded.ResultsThe mean effective dose was 5.7 ± 1.7 mSv (range, 1.6–11.1 mSv) for 151 patients (75%) scanned with a one-heart beat acquisition. Qualitative image quality was assessed to be in good to excellent range, and mottle image quality was in low-to-medium mottle range. For patients scanned with 2- or 3-heart beat acquisition, radiation dose was higher with mean exposures of 13.0 ± 3.3 mSv and 19.5 ± 5.3 mSv, respectively.ConclusionsLow effective radiation dose with acceptable image quality on 320-row MDCT can be achieved with one-heart beat scan acquisition when HR is <65 beats/min. Further reduction in dose can likely also be achieved by modification of the prospective-gated imaging parameters.