自动管电流调节技术对下肢血管CTA图像质量和辐射剂量的影响

摘要

目的:探讨64排螺旋CT采用固定管电流和固定噪声指数(NI)的Z轴自动管电流调节(ATCM)技术对下肢血管CTA图像质量及辐射剂量的影响.方法:将60例行下肢血管CTA检查的患者随机分为A组(固定管电流250 mA)、B组(ATCM技术,50~380 mA,NI 12)各30例.其余扫描参数均一致.检查结束后分别对2组相同横断层面图像的股主动脉、腘动脉和胫后动脉图像噪声(SD)进行测量,并对重组后的三维图像进行质量评分,同时记录机器自动生成的CT剂量指数(CTDIvol)、相应剂量长度乘积(DLP),对比2组数据之间差异.结果:2组的血管图像噪声和图像质量评分差异均无统计学意义(均P<0.05),重组后的三维图像均能完整显示下肢动脉及其各级主要分支,满足诊断需要.B组的辐射剂量与A组比较,CTDIvol降低了51.72%(P=0.000,P<0.05)、DLP降低了47.87%(P=0.000,P<0.05)、有效辐射剂量(ED)下降了43.90%.结论:下肢血管CTA采用ATCM技术,在保证图像质量的同时可降低患者的辐射剂量.%Objective:To explore the influence of automatic tube current modulation(ATCM) with fixed noise index (NI) in 64 slice spiral computed tomography (MSCT) on the the image quality and radiation dose of lower limb CT angiography (CTA). Methods:60 patients performed lower limb CTA were randomly divided into two groups named A(250 mA) and B(ATCM,50~380 mA,NI=12). Other scanning parameters were same in the two groups. Data were measured and recorded in the two groups,including the standard deviation (SD) in images of femoral artery,popliteal artery and posterior tibial artery on the same cross section,the quality scores of reconstructed three-dimensional images,CTDIvol automatically generated by the instrument and DLP. The data difference in two groups were compared with the independent-samples t test. Results:The differences of SD and image quality scores in two groups were not significant (P>0.05),while all reconstructed three-dimensional images approached the diagnostic criteria by the whole demonstration of lower limb arteries and their main branches .Compared with group A ,CT-DIvol and DLP in group B reduced by 51.72% (P<0.05)and 47.87% (P<0.05) respectively. Effective Dose (ED) in group B reduced by 43.90%. Conclusion:Application of ATCM in lower limb CTA can not only ensure the quality of images but also reduce the radiation dose on patients.