心电图调制电流对有波动心率的心脏CT扫描曝光剂量及图像质量影响的研究  

Evaluation on the influence of ECG mA modulated on image quality and exposure dosage of CT cardiac scan with fluctuant heart rate

作　　者：殷焱[1] 陈洁[1] 柴伟明[1] 华佳[1] 沈云[2] 许建荣[1] 

机构地区：[1]上海交通大学医学院附属仁济医院放射科,上海200127 [2]GE医疗集团CT实验室,北京100176

出　　处：《中国医学影像技术》2008年第6期946-949,共4页Chinese Journal of Medical Imaging Technology

摘　　要：目的利用心脏体模评估16层螺旋CT心脏扫描时的心率波动,开启或关闭心电图调制电流技术以及不同的心电图调制电流技术对图像质量是否有影响,并判断心电图调制电流技术是否能有效降低曝光剂量。方法将跳动的心脏模具设定为60bpm基础心率,并根据不同的心率波动情况分为6组,关闭心电图调制电流对心脏模具进行心脏扫描。扫描同时记录各扫描序列的曝光剂量,在采集到的图像中选取中心球囊结构均匀的部位,测量该部位的CT值及背景部位CT值的差值,并分别记录图像测量部位的标准差值(s值),然后根据二维及三维图像质量情况进行分级分析;随后开启心电图调制电流,分4组采用不同的心电图调制电流参数进行心脏CT扫描,分别重复上述扫描并记录曝光剂量,对采集到的图像进行相同测量和记录。将5次扫描所测得的数据进行统计分析。结果在心率波动情况下,5组图像的CT值差值及s值分别经检验证明图像信噪比无明显统计学差异(P>0.05),二维图像及三维图像质量经检验证明其无明显统计学差异(P>0.05)。心电图调制开启时比关闭时曝光剂量有明显减低,并且不同设置的心电图调制电流在曝光剂量的比较中也存在明显统计学差异(P<0.01)。在心率波动情况下,曝光剂量最多可减少45.0%,最少可以减少7.5%,平均剂量减小了25.4%。但心电图调制电流开启时,心率的波动与曝光剂量之间无明显的相关性,而当心率波动达到15bpm时曝光剂量将明显增加。结论16层螺旋CT心脏扫描时,即使心率存在一定的波动,开启心电图调制电流技术仍能够有效降低曝光剂量,同时对图像质量无明显影响。Objective To decide whether the ECG modulated current will effectively reduce the exposure dosage by making use of the cardiac phantom. Methods The cardiac pulsating phantom was set at 60 bprn as the basal heart rate, then the test was divided into 6 groups according to the fluctuant heart rate. The phantom was scanned with the 240 mA current, 120 kV tension, 16×0. 625 mm thickness and 0. 275 ： 1 pitch when the ECG modulated current was turned off, and the exposure dosage of each scan sequence was documented. The model of MSCT instrument was BrightSpeed Elite, GE medical systems. The quality of 2D and 3D images were divided into 4 classes. The results from the five groups with and without ECG modulated current were analyzed. Results Statistical analysis showed no significant difference （P〉0.05） among the SNR of images from the five groups when the heart rate was fluctuant, and there was also no significant difference （P〉0.05） between the quality of the 2D and 3D images with the rank sum test. The exposure dosage was remarkably reduced when the ECG modulated current was on than when it was off with the fluctuant heart rate. Furthermore,there were apparent significant difference （P〈0.01） among the different ECG modulated current parameter groups. The exposure dosage can be reduced from 45.0% to 7.5 % and the mean dosage reduction was 25.4 % under the situation that the heart rate was undulated. There was no obvious relativity between the fluctuation of the heart rate and the exposure dosage, but if the heart rate fluctuation was up to 15 bpm, the exposure dosage would increase obviously. Conclusion Scanning the heart with 16-slices spiral CT, the application of ECG modulated current can effectively reduce the exposure dosage without sacrificing the image quality even if heart rate was fluctuant.

关 键 词：心率 冠状动脉 体层摄影术 X线计算机 影像质量 

分 类 号：R331.36[医药卫生—人体生理学] R814.42[医药卫生—基础医学]