First Experience with 320-row Multidetector CT Coronary Angiography Scanning with Prospective Electrocardiogram Gating to Reduce Radiation Dose

Background: The 320-row multidetector CT (MDCT) provides the capability for prospective electrocardiogram-gated cardiac CT angiography.

Objective: We assessed the effective radiation doses of MDCT with a 320-row detector volume scanner.

Methods: Two 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 > or =80 beats/min were scanned with either 2- or 3-heart beat acquisitions, respectively. Patients with arrhythmias were not excluded.

Results: The 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.

Conclusions: Low 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.