管电流调制技术在多层螺旋CT胸部检查中的应用评价

Attenuation-based online tube current modulation applied to multislice CT of the chest

目的评价管电流调制技术降低多层螺旋CT(MSCT)胸部扫描剂量的程度,以及对CT图像质量的影响。方法将100例受检者随机等分成两组(管电流调制组和管电流恒定组)。分别统计CT剂量权重指数(CTDIw)、剂量长度乘积(DLP)及有效毫安秒(mAs)。图像质量分为优、良、差三级进行评判,并记录评价结果。数据资料采用成组t检验和秩和检验进行统计分析。结果管电流调制组有效mAs为(87.69±2.74)mAs,较恒定组(100mAs)降低约12%(P<0.001)。管电流调制组CTDIw(6.16±0.23mGy),明显低于恒定组(7.0mGy)(P<0.001)。管电流调制组DLP(202.03±18.27mGy·cm)约为恒定组(230.13mGy·cm)的87.7%(P<0.001)。相同扫描条件和图像后处理方式下,管电流调制组的图像质量不仅未降低,而且还可选择性地改善(P>0.05)。结论管电流调制技术可有效降低CT剂量,并不牺牲图像质量,有较好的临床应用前景。

Objective To evaluate the radiation dose saved by attenuation-based online tube current modulation applied to multislice CT （MSCT） of the chest, and impact on the quality of CT images. Methods One hundred patients who underwent MSCT of the chest were classified randomly two groups （attenuation-based online tube current modulation group and constant tube current）. Consecutive acquisitions including weighted-CT-dose index （CTDWI）, dose long product （DLP） and effective mAs were obtained in each patient and compared for each group. Three experienced chest radiologists who were unaware of the CT technique reviewed CT images for overall image quality using a 3-grade scale （excellent, good and worst）. The data were analyzed using the unpaired t test and Wilcoxon＇s signed rank test. Results Mean effective mAs （87.69±2.74 mAs） reduction was 12% for the chest scan in attenuation-based online tube current modulation group. CTDWI （6.16 ± 0.23 mGy） and DLP （202.03±18.27 mGy ·cm） reduction were obviously less than the constant tube current group. The differences were statistically significant （P〈0. 001）. The assessment of image quality showed no significant differences under same protocol and post-processing technique （Wilcoxon＇s signed rank test, P〉0.05）. Conclusion Attenuation-based online tube current modulation used with MSCT should be considered as a promising technique because it saves as much as 13% of the radiation dose on chest scan and don＇t impair the image quality.