降低辐射剂量在下肢CTA中的可行性探讨

Reduce the Radiation Dose in the Lower Extremities to Explore the Feasibility of CTA

目的:比较多层螺旋CT(MSCT)不同的螺距(Pitch)与不同的球管旋转速度(s/r)优化搭配在下肢CTA中的图像质量与辐射剂量。资料与方法:前瞻性选择2012年至2013年间临床拟诊为下肢动脉血管病变的患者90例,根据不同的螺距与不同球管旋转速度优化搭配随机分为3组(n=30),A组:螺距0.516、0.6s/r;B组:螺距0.984、0.8s/r;C组:螺距1.375、1s/r;均采用相同的kV、mAs、注射速率、对比剂量及浓度行对比剂追踪手动触发扫描。扫描结束后记录CT容积剂量指数(CTDIvol)、剂量长度乘积(DLP)、射线有效利用率(Dose)及扫描时间(To-time)。将3组的图像质量、辐射剂量及扫描时间采用方差检验(F)进行统计学分析。结果:3组的平均扫描时间分别为(30.30±0.54)s、(21.30±0.44)s、(19.30±1.48)s,之间的差异具有统计学意义(P<0.05),C组的扫描时间最短;DLP分别为(4002.35±71.56)mGy·cm、(2106.25±62.14)mGy·cm、(1534.08±106.50)mGy·cm,3组之间的差异亦具有统计学意义(P<0.05);3组的ED分别为68.06mSv、35.81mSv、26.08mSv,B组比A组的每位患者ED降低了47.37%(32.23/68.04),C组比A组的每位患者ED明显降低了61.67%(41.96/68.04)、C组比B组降低了27.17%(9.73/35.81),3组之间的差异具有明显统计学意义(P<0.01);3组在腹主动脉远端、双侧髂外动脉、腘动脉、胫前动脉处的平均CT值为300.35Hu、302.49Hu、307.09Hu,之间的差异不具有统计学意义(P>0.05),重组血管清晰度及显示血管节段数均具有较好一致性;3组的Dose分别为94.94%、95.61%、95.61%。结论:3组的图像质量均达到诊断要求,但螺距1.375、1s/r搭配可以明显降低患者的辐射剂量,值得临床推广应用。

Objective： To contrast the multislice CT （MSCT） different pitch and the ball tube rotation speed optimization combination in the lower limbs CTA image quality and radiation dose. Materials and methods： The ninety patients with lower limb arterial diseases were contrast medium-tracking and manual-triggering scaned in the same condition （such as kV, mAs, injection rate, the concentration and dose of contrast medium） between 2012 and 2013. The different Pitch and ball tube rotation speed （s/r） composite were randomly divided into three groups （n = 30）, group A： Pitch： 0.516, the tube rotation speed： 0.6 s/r; Group B： pitch： 0.984, the tube rotation speed： 0.8 s/r; Group C： pitch： 1.375, the tube rotation speed： 1 s/r. The volume CT Dose index （CTDIvol）, Dose length product （DLP） and the effective utilization rate of radiation （dosed） were automatic acquired at the end of the scanning and the scanning time （To-time） were also recorded. Differences among groups were statistical analysised with variance test （F）. Results： Significant difference （P 〈 0.05） in mean scanning time among groups was found and the mean scanning time were （30.30＋0.54） s, （21.30~0.44） s, （19.30~ 1.48） s, respectively, which group C scanning time was shortest. Significant difference （P 〈 0.05） in DLP among groups was seen and DLP were （4 002.35 i 71.56）mGy. cm, （2 106.25 ~ 62.14）mGy. cm, （1 534.08 ~ 106.50）mGy ~ cm, respectively. Significant difference （P 〈 0.01） in ED among groups was also found and the ED were 76.05 mSv, 40.02 mSv, 29.17 mSv, respectively. The ED of group B was reduced by 47.37% （32.23/68.04） compared with group A, group C was reduced by 61.67% than group A （41.96/68.04） and group C was reduced by 27.17% （9.73/35.81） than group B. The mean CT value of the distal abdominal aorta and bilateral iliac artery, popliteal artery and tibialis artery were 300.35 Hu, 302.49 Hu, 307.09 Hu and also no difference （P〉 0.05） in mean CT value were seen. The restructuring clarity of vessel had a good consistency with displayed vascular segment numbers. The dosed in three groups were 94.94%, 95.61%, 95.61%, respectively. Conclusion： The image quality of 3 groups all satisfy the requirement of diagnosis, but the pitch 1.375, 1 s/r can significantly reduce the radiation dose of the patients, it is worthy of popularization and application.