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

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 ± 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.