低剂量非增强多排螺旋CT扫描探查尿路结石:模型研究

目的:探讨将低剂量多排螺旋CT(MDCT)扫描技术应用我国成人尿路结石探查的可行性方案及其临床应用的可靠性。方法:参照228例体重75kg以下成人腹盆部骶髂关节水平的体径值制作含有各种组织成分并在其中植入2～5mm的草酸钙结石和7mm管径的水管模型;使用GE Lightspeed 16CT机对模型进行常规剂量和一系列低剂量扫描,筛选出可满足结石诊断要求的低剂量可行性扫描方案,并应用于临床探查尿路结石评价其可靠性。结果:辐射量CT-DIvol为2.67、2.99和3.4mGy的3个序列图像质量基本可满足诊断。选择其中CTDIvol为2.99的序列,扫描参数为120kV、60mA、扫描时间0.5s/r、扫描层厚5mm、螺距0.938应用于临床,检查病例104例,诊断尿路结石的灵敏度、特异度分别为96.67%和88.64%;常规剂量尿路结石检查病例100例,其灵敏度、特异度分别为98.18%和93.33%;比较两种方法的灵敏度与特异度的95%可信区间有重叠,表示两种方法的特异度与灵敏度无统计学差异。结论:应用合适的低剂量MDCT扫描序列探查成人尿路结石是可行、可靠的。

Study on low dose non-enhanced MDCT scanning for detection of urinary calculi: a phantom study

Objective：To discuss the feasibility and reliability of the clinical application of low dose MDCT scanning technique for detection of calculus in adult urinary collecting system. Methods： According to the average body dimensions at sacroiliac joint level of 228 adults with body weight below 75kg, a fresh pork model contained various tissue constituents with implantations of 2~5mm calcium oxalate calculi and water-filled plastic tube of 7ram in diameter was established. Rou- tine radiation dose and a series of low dose on GE lightspeed 16 CT were tested on the model and optimized to detect urinary calculi. Results：The image quality at the dose levels of CTDIvol 2.67,2.99 and 3.4mGy could basically satisfy the diagnos- tic requirement. On 104 cases,the sensitivity and specificity of diagnosing urinary calculus was 96.67% and 88.64%, re spectively, with CTDIvol 2.99mGy, 120kV, 60mA,0.5s per rotation, slice thickness 5mm and pitch 0. 938. On other 100 ca- ses, the sensitivity and specificity was 98.18% and 93.33 %, respectively, using routine dose and parameters. The 95 %con- fidence levels of sensitivity and specificity overlapped and indicated that there was no significant difference between the two methods. Conclusion：Application of proper low dose MDCT sequences for detection of adult urinary calculi is feasible and reliable.