Optimization of Retrospective Gated-ECG Coronary Computed Tomography Angiography by Dose Reduction in Patients with Different Body Mass Indexes.

Background: The reduction of patient radiation dose in coronary Computed Tomography Angiography (CCTA) with acceptable image quality is considered an important factor in the research.

Objective: This study aims to optimize the CCTA protocol using a retrospective Electrocardiogram (ECG)-gated axial scan protocol in patients with different Body Mass Indexes (BMIs).

Material and methods: In this cross-sectional study, 66 patients into three main groups: 80 kVp (Group A), 100 kVp (Group B), and 120 kVp (Group C), underwent CCTA. Each group was then divided into two subgroups of BMI<25 and >25 kg/m². Image noise, mean vascular attenuation at the aorta, signal-to-noise ratio (SNR), and Contrast-to-Noise Ratio (CNR) at five regions of coronary arteries, in which Coronary artery anomalies are common were qualitatively evaluated by subjective image quality analysis.

Results: At each kVp, there were no significant differences in CNR, SNR, noise level, and the effective dose between BMI>25 kg/m² and BMI<25 kg/m². The effective radiation dose of groups A, B, and C were 4.16, 8.46, and 14.3 mSv, respectively. Subjective image quality assessment scores were 3.18, 3.5, and 3.73 out of 4 in groups A, B, and C, respectively.

Conclusion: Patient radiation dose using retrospective ECG-gated CCTA can be reduced by about 70% at 80 kVp, which is almost close to the prospective CCTA dose ranges. The retrospective CCTA at 80 kVp can be optimized even in overweight patients (BMI>25 kg/m²).