Assessment of Radiation Dose and Image Quality in Coronary Computed Tomography Angiography Using Adaptive Statistical Iterative Reconstruction and a Body Mass Index-adapted Protocol

Adaptive statistical iterative reconstruction (ASI R) is a new method for reduction of the radiation dose in CT scans. We aimed to evaluate the radiation dose and image quality after employing ASIR and a body mass index-adapted protocol in coronary CT angiography.We evaluated 66 patients who underwent coronary CTA using 50% ASIR. The tube voltage (100~120 kVp), current (300~550 mA) and filter (Bowtie small and large) were chosen according to body mass index (BMI). Patients with a sinus rhythm and a heart beat≦65 beats/min underwent a prospective gating (PG) scan, and the others underwent a retrospective gating (RG) scan. The image noise, signal-to-noise ratio (SNR) and effective dose were measured and calculated. The objective image quality was evaluated according to the image noise and SN R, and the subjective image quality was assessed on a 5-point scale for the coronary segments.The mean effective dose in the PG group was 1. 8 ± 0.7 mSv (range: 0.3 - 3.2 mSv), while that in the RG group was 8.6 ± 2.4 mSv (range: 3.8 - 14.3 mSV). The effective dose was correlated with BMI (r = 0.52, p ＜ 0.00 1). There was neither a significant correlation between BMI and image noise (r = 0.12, P = 0.362) nor between BMI and SNR (r = -0.15, p = 0.226). Of 864 segments, 851 (98.5%) were of a diagnostic image quality (score 1-3). The mean score of the subjective image quality according to the 5-point scale was 1.6 ± 0.4. The subjective image quality was not correlated with BMI (r = 0.019, p = 0.88 1).By using ASIR and BM I-based scanning paral11eters, the radiation dose was effectively lowered in comparison with previous studies of coronary CTA. The image noise and study interpretability were also preserved.

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