双源CT冠状动脉成像辐射剂量的优化

An optimized radiation dose on dual-source CT coronary angiography

目的：探讨使用更窄的曝光时间窗对双源CT冠状动脉成像图像质量和辐射剂量的影响。方法：选择心律稳定、配合屏气在本院行冠状动脉CTA检查者共360例，按心率及扫描方案随机分为5组：当心率＜65次/分时，行回顾性心电门控扫描，用70％-80％曝光时间窗成像冠状动脉（A组）；窄窗方案根据前瞻性心电门控平扫所获得的最佳时相，选择此时相为中心总长1％作为曝光时间窗，行前瞻心电性门控冠状动脉成像（B组）。当心率≥65次/时，行回顾性心电门控扫描，常规使用30％-80％曝光时间窗成像冠状动脉（C组）；窄窗方案根据前瞻性心电门控平扫所获得的最佳时相，以此时相为中心选择总长10％的曝光时间窗，分别用前瞻性心电门控（D 组）和低剂量回顾性心电门控行冠状动脉成像（E组）；分别计算各组平均有效辐射剂量以及冠状动脉图像质量（4分制评分），并作统计学分析。结果：A 组[（8．11±1．54）mSv]和B组[（3．63±0．82）mSv]，C 组[（10．56±2．51）mSv]和 D 组[（4．42±1．16）mSv]，D 组[（4．42±1．16）mSv]和E组[（5．43±1．14）mSv]的辐射剂量相比较均有统计学差异（P＜0．05），采用窄窗方案前瞻性心电门控技术的辐射剂量最少；而各组间图像质量，均无统计学差异（P＞0．05）。结论：前瞻性心电门控通过平扫获得最佳时相，当心率＜65次/分时，选择曝光总长1％的时间窗，而当心率≥65次/分时，选择曝光总长10％的时间窗，能获得高质量的、满足诊断要求的图像，并可有效地降低辐射量。

Objective：To evaluate the image quality and radiation dose of dual-source CT coronary angiography （CT-CA）with a more narrow exposure window.Methods：In all,360 cases underwent dual-source CTCA and were randomly divided into five groups according to the heart rate and scanning protocol.Group A,retrospective ECG-gated scan of the patients with heart rate 〈65 beats per minute （bpm）was performed from 70% to 80%of the R-R interval to reconstruct coronary artery;Group B,prospective ECG-gated scan of the patients with heart rate 〈65bpm was performed with 1% of the total length of the exposure window;Group C,retrospective ECG-gated scan of the patients with heart rate ≥65bpm was performed from 30% to 80% of the R-R interval to reconstruct coronary artery;Group D,prospective ECG-gated scan of the patients with heart rate ≥65bpm was performed with 10% exposure window;Group E,low dose retrospective ECG-gated scan of the patients with heart rate ≥65bpm was performed.The average effective radiation dose and image quality of coronary arteries （4-point scale）were calculated for each group,and statistical analysis was done.Results：Difference of radiation dose between each group was statistically significant （P〈0.05）.A narrowed scan window on prospective ECG gated dual-source CTCA could reduce the radiation dose;while there was no significant difference in the image quality between the groups （P〉0.05）.Conclusion：Prospective ECG-gated dual-source CTCA can reduce the radiation dose while maintaining good image quality by selecting 1% of the total length of the exposure window（heart rate 〈65bpm）,and 10% of the total length of the exposure window （heart rate ≥65bpm）after obtaining the optimal interval by plain scan.