# Optimization of acquisition phase and acquisition time window of coronary artery CT angiography with different heart rates based on prospective ECG-gating

## TL;DR

This study finds optimal timing for coronary CT scans based on heart rate to reduce radiation without losing image quality.

## Contribution

Identifies heart rate-specific acquisition windows for CCTA that significantly reduce radiation dose while preserving image quality.

## Key findings

- Optimal reconstruction phases and acquisition time windows vary with heart rate.
- Group B had 42.6% lower radiation dose than Group A with no significant difference in image quality.
- Narrowing acquisition time using prospective ECG-gating reduces radiation without compromising results.

## Abstract

To determine the optimal reconstruction phase and acquisition time window of coronary computed tomography angiography (CCTA) in patients with different heart rates based on prospective ECG-gating and to compare the image quality and radiation dose between the whole cardiac cycle mode and optimized acquisition time window.

One thousand patients(536male, mean age ± standard deviation, 57.43 ± 11.73years) who underwent CCTA were divided into two groups, group A (n = 500)and group B(n = 500). According to the heart rate at the time of CCTA, the subjects were divided into subgroups A1 and B1 (< 51 bpm), A2 and B2 subgroups (51–55 bpm), A3 and B3 subgroups (56–60 bpm), A4 and B4 subgroups (61–65 bpm), A5 and B5 subgroups (66–70 bpm), A6 and B6 subgroups (71–75 bpm), A7 and B7 subgroups (76–80 bpm), and A8 and B8 subgroups (81–85 bpm), A9 and B9 subgroups (> 85 bpm). Group A individuals underwent CCTA within a single cardiac cycle and the optimal reconstruction phase at each heart rate was identified based on image quality. The ideal acquisition time window was determined by considering the 95% confidence interval of the best reconstruction phase, which was equivalent to the average value of the best reconstruction phase (standard deviation × 2). The individuals in group B were examined within the optimal collection time window. Compare the radiation doses and image quality of patients in groups A and B.

The findings indicated that the A1-A9 subgroups’ optimal reconstruction phase and acquisition time window were: 61%~85% RR interval; 68%~84% RR interval;70%~82% RR interval and 34%~46% RR interval; 70%~82%RR interval, and 34%~46% RR interval;70%~82% RR interval and 36%~48% RR interval; 65%~89% RR interval and 38%~50% RR interval;68%~84% RR interval and 36%~56%RR interval; 38%~54% RR interval; 38%~58% RR interval. No statistically significant difference was observed in terms of Signal-to-Noise Ratio(SNR), and Contrast-to-Noise Ratio(CNR) between group A and group B, (P > 0.05). The average effective radiation dose(ED) values in Group B were 42.6%, lower than in Group A, (P < 0.001).

Ideal acquisition phase and acquisition-time windows vary among individuals with varying heart rate(HR). Narrowing the acquisition timeframe based on prospective electrocardiogram(ECG)-gating can considerably lower the radiation dose of CCTA imaging while maintaining image quality.