目的探讨不同心率在640层螺 旋CT冠状动脉CTCA中对血管图像质量的 影响以及辐射剂量变化。方法 选取91例 患者，男性51例，女性40例，平均年龄 58岁。分成三组，A组30例，心率≤65次 /分；B组30例，65次/分＜心率≤80次/ 分；C组31例，心率＞80次/分。扫描完成 后选取最佳时相进行容积再现(VR)、最大 密度投影(MIP)、多平面重建(MPR)及曲面 重建(CPR)进行血管重建，根据4分法对血 管图像质量分级并进行统计学分析，记录 各组的辐射剂量程度乘积(DLP)。结果 三 组的血管图像质量在可评价比例及优良率 无统计学意义，心率与血管图像质量等级 呈负相关。A组DLP为(3.37±2.12) mGy. cm，B组为(4.78±1.92)mGy.cm，C组为 (6.11±2.79)mGy.cm，三组的辐射剂量有 差异，经检验，有统计学意义，心率与辐 射剂量呈正相关。结论 640层螺旋CT冠状 动脉CTCA在高心率患者能较好的显示图 像，同时辐射剂量也增加，应该在情况允 许的条件下尽可能降低心率至65次/分以 下，在获得优良血管图像质量的同时降低 辐射剂量，有利于冠状动脉CTCA的可持续 发展，以便让更多患者从中获益。

Objective To investigate the influence of heart rate and blood vessel image quality and radiation dose changes in 640 slice spiral CT coronary artery imaging. Methods A total of 91 patients, male 51 cases, female 40 cases, average age is 58 years old. Divided into three groups, 30 cases in group A whose heart rate was equal or greater than 65 beats per minute; 30 cases in group B and the heart rate of them was greater than 65beats per minute but less than 80 beats per minute; 31 cases in group C whose heart rate was greater 80 beats per minute. After the scan completed, the most optimum phase was chosen for volume rendering (VR), maximum intensity projection (MIP), multi planar reconstruction (MPR) and curved planar reconstruction (CPR) to have vascular reconstruction, vascular image quality was classified according to the 4 points method and it was statistically analyzed. We recorded the radiation dose product of each group(DLP). Results The blood vessel image quality evaluation and the excellent and good rate in the proportion of the three groups had no statistical significance, the heart rate was negatively correlated with the quality grade of blood vessel image. A group DLP was (3.37±2.12) mGy.cm, B group was (4.78±1.92) mGy.cm, C group was (6.11±2.79) mGy.cm, radiation dose of three groups was statistically significant, the heart rate is positively correlated with the radiation dose. Conclusion 640 slice spiral CT coronary angiography can show the image better in patients with high heart rate, but also increase the radiation dose, we should reduced heart rate to 65 beats per minute below as far as possible with the condition permitted. To obtain excellent vascular image quality by lower radiation dose at the same time, is conducive to the sustainable development of coronary artery CT angiography imaging, so that more patients can be benefitted from it.