个体化低剂量扫描在64排CT冠状动脉成像中的临床研究

The Clinical Study of Individualized and Dose-Reducted Scan on Coronary Angiography with 64-Row Multidetector Computed Tomography

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 determine the optimal scan protocols of Computed Tomography Coronary Angiography（CTCA） for 64 row multidetector computed tomography（64-MDCT） and to reduce the radiation dose significantly on the premise of consistent image quality.Materials and Methods One hundred and twenty consecutive patients who underwent CTCA using 64 MDCT were divided into 4 groups according to the heart rate.The heart rates of the first and third groups were less than 65 beats per minute（bpm） while those of the second and forth groups were between 65 to 75 bpm.The tube current and voltage was determined by Body Mass Index（BMI）.Prospective ECG gated CT angiography protocol was performed with step and shoot axial scanning direction in the first and second groups.We set the padding time on 0 ms and exposure time for 75% cardiac phases of the R R interval in the first group,the padding time on 200 ms and set exposure time for 60% cardiac phases of the R R interval in the second group.Retrospective ECG gated CT angiography was performed with helical scanning direction in the third and forth groups after using ECG automatic tube current modulation technique.The peak tube current was set for 70%-80% cardiac phases of the R R interval in the third group,which is 40%-80% in the forth group.After scanning,we split phases between 40% and 80% R R interval by 5% cardiac phases.The image quality and effective Dose（ED） of 1-3 groups,2-4 groups,1-2 groups,3-4 groups are compared respectively.P0.05 for difference was statistically significant.Results There are no statistical differences in image quality between 1-3 groups,2-4 groups.Compared with the third group,the ED value of the first group was decreased by 76%.Compared with the forth group,the ED value of the second group was decreased by 54%.Conclusion The best individualized low dose scanning protocol is prospective ECG gated CT scanning protocol which demands the heart rate of less than 65 BPM.