摘要目的 利用心脏体模评估16层螺旋CT心脏扫描时,不同的心率波动对心电图调制技术降低曝光剂最能力的影响,以及不同的心电图调制电流参数对曝光剂量和图像质量的影响.方法 将跳动的心脏模具设定为60次/min(bpm)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,在采集到的图像中进行冠状面重建后选取中心层而测量球囊图像信噪比的标准差(SD)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,对图像信噪比分别进行方差分析,F检验及两样本比较的秩和检验.结果 采用宽期相(69%～99%)高mA输出,高心率波动(≥7.5 bpm)和低心率波动图像的图像信噪比SD值(分别为27.78与26.30),差异无统计学意义(P＞0.05),二维图像及三维图像质量经检验证明其差异无统计学意义(P＞0.05);仪在85%期相选择高mA输出,高心率波动(≥7.5 bpm)和低心率波动图像的图像信噪比SD值(分别为26.78与29.90)差异1竽在统计学意义(P＜0.01).在心率波动情况下,心电图调制开启时(0.47～0.79 mSv)比关闭时曝光剂昔(0.85 mSv)有明显减低,曝光剂量最多可减少44.7%,并且不同设置的心电图调制电流在曝光剂量的比较中差异也有统计学意义(P＜0.01).模具实验的散点图显示,心电图调制电流开启时,心率波动≤12.5 bpm时,曝光剂量随心率波动改变不明显(变化为0.1～1.1 mSy),但是当心率波动＞12.5 bpm时,曝光剂量将明显增加(达到0.6～1.7 mSv).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.

abstractsObjective To investigate the influence of electrocardiogram(ECG)-controlled dose modulation on exposure dosage and image quality of cardiac CT imaging in a cardiac phantom with simulated fluctuant heart rate.Methods The basal heart rate of the cardiac pulsating phantom was set as 60 bpm.the experimental situations were divided as 6 groups according to different heart rates.The cardiac imaging was performed on the cardiac phantom when the ECG-controlled dose modulation was firstly turned off.The exposure dosage of each scan sequence was documented.The standard deviation of the CT values of the phantom was measured on the central slice after coronal reformation of the raw data.The quality of 2D and 3D images were scored.Thell cardiac imaging was performed when ECG modulation was on and set as four groups according to different modulation parameters.All the data were documented as before.The results from the five groups with and without ECG modulation current were analyzed bv F test and comparative rank sum test using the statistical software SPSS 10.0.Results Statistical analysis showed no significant difference(P＞0.05)between the SNR of images(SD value was 27.78 and 26.30)from the groups that full mA output at wide reconstruction phase(69%～99%)when the heart rate was fluctuant(≥7.5 bpm).There was also no significant difference(P＞0.05)between the quality of the 2D and 3D images.But there was a significant difference(P＜0.01)between the SNR of images(SD value was 26.78 and 29.90)that full mA was only used at 85%reconstruction phase when the heart rate Was fluctuant(≥7.5 bpm).The exposure dosage was remarkably reduced when the ECG modulated current was on than when it Was off under fluctuant heart rate.Furthermore.there were significant difierence(P＜0.01)among the difierent ECG modulated current parameter groups.The exposure dosage can be reduced by 44.7%under the situation that the heart rate was fluctuant.Whell the fluctuation of the heart rate was≤12.5 bpm,there wag no obvious relationship between the fluctuation of the heart rate and the exposure dosage (the variation was from 0.1 to 1.1 mSv),but if the heart rate fluctuation was＞12.5 bpm,the exposure dosage would increase obviously (from 0.6 to 1.7 mSv).Conclusion For cardiac imaging with 16-slice row CT,the application of ECG modulated current can effectively reduce the exposure dosage without compromising the image quality even if heart rate was fluctuant.