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目的选择最佳的64排螺旋CT(multidetector computed tomography,64-MDCT)冠状动脉CT成像(compu-ted tomography coronary angiography,CTCA)扫描技术,在保证图像质量的前提下,最大限度地降低辐射剂量。资料与方法连续选取行64-MDCT CTCA检查的患者120例,根据心率将患者分为4组:第1、3组心率<65次/min,第2、4组心率控制范围在65～75次/min之间。根据患者的体重指数(body mass index,BMI)确定管电流及管电压。第1、2组采用前瞻性心电门控扫描,将Padding time及曝光期相分别设定为:0 ms,75%R-R间期;200 ms,60%R-R间期。第3、4组采用回顾性心电门控扫描,最大毫安分别设定为70%～80%R-R间期、40%～80%R-R间期。扫描结束后,将第2、4组图像数据以5%为间隔,在40%～80%R-R间期之间拆分期相。对1、3组,2、4组,1、2组,3、4组之间的图像质量、有效剂量(effective dose,ED)行统计学分析;P<0.05为差异有统计学意义。结果 1、3组之间及2、4组之间的图像质量差异均无统计学意义。第1组的ED值比第3组降低了76%,第2组的ED值比第4组降低了54%。结论最佳的个体化低剂量扫描方案为:将心率降至65次/min以下,采用个体化的前瞻性心电门控扫描。
Objective To select the best 64-MDCT coronary angiography (CTCA) scanning technique to minimize the radiation dose while ensuring the image quality. Materials and Methods 120 consecutive patients undergoing 64-MDCT CTCA were selected. The patients were divided into 4 groups according to heart rate: group 1, group 3 heart rate <65 beats / min, group 2, group 4 heart rate control range 65-75 / min. The tube current and tube voltage were determined based on the patient’s body mass index (BMI). Groups 1 and 2 were prospectively gated with gate-gated ECG and the Padding time and exposure phase were set as 0 ms, 75% R-R interval, 200 ms, 60% R-R interval, respectively. The third and fourth groups were retrospectively ECG-gated with maximal mA of 70% -80% R-R interval and 40% -80% R-R interval, respectively. After the scanning, the second and fourth sets of image data are separated by 5% intervals between 40% and 80% R-R intervals. The image quality and effective dose (ED) between 1, 3, 4, 1, 2, 3 and 4 groups were statistically analyzed. P <0.05 was considered statistically significant. Results There was no significant difference in image quality between groups 1 and 3 and between groups 2 and 4. The first group had a 76% lower ED value than the third group and the second group had a 54% lower ED value than the fourth group. Conclusion The best individualized, low-dose scan protocol was to reduce heart rate below 65 beats / min using an individualized prospective ECG gated scan.