16层螺旋CT低剂量平扫诊断肾及输尿管结石

The diagnosis of nephrolithiasis and ureterolithiasis using low-dose unenhanced 16-detector helical CT

目的评价16层螺旋CT低剂量平扫对肾及输尿管结石的诊断价值。方法收集65例临床拟诊肾及输尿管结石病例,每一病例在常规标准剂量(120 KV,160 mAs)扫描后再行低剂量扫描,在低剂量扫描中,管电流下降到60 mAs,其余参数及扫描范围均保持不变。三位高年资医师分别观察、记录:结石的有无、大小、位置、数目及结石的继发梗阻征象,分别记录放射剂量。结果在低剂量平扫中发现33例肾结石,17例输尿管结石,结石数目75个,肾积水24例,输尿管扩张16例。与标准剂量扫描结果比较,低剂量扫描发现肾及输尿管结石的敏感性及准确率分别为100%、97%,发现肾积水及输尿管扩张的准确率100%。与标准剂量扫描比较,低剂量扫描放射剂量下降62%,两者差异有统计学意义(P<0.05)。结论对于体重<90 kg的病人,在16层螺旋CT,管电流为60 mAs的低剂量平扫诊断肾及输尿管结石能够获得高的准确率,并且明显降低病人的放射剂量。

Objective To determine the accuracy of low-dose unenhanced 16-detector helical computed tomography（CT） in the detection of nephrolithiasis and ureterolithiasis. Methods Sixty-five patients with suspected nephrolithiasis and ureterolithiasis were collected. Followed by standard-dose helical CT scans with 2-mm-thick section, 120kv, 160mAs, low-dose scan was carried out with the tube current reduced to 60 mAs. All other technical parameters and anatomic coverage remained constant. The location, size and number of calculi, the secondary signs of obstruction, and the radiation dose were observed by three senior-experienced physicians. Results With the low-dose scan, 33 cases were detected with renal calculi and 17 cases with ureteral calculi. Totally 75 stones were detected. There were 24 patients had pelvicaliectasis and 16 had ureteral dilatation. The sensitivity and accuracy rates of the detection of nephrolithiasis and ureterolithiasis on the low-dose scan were 100% and 97% respectively, and those of the detection of pelvicaliectasis and ureteral dilatation were all 100%. Compared with the standard-dose scan, the radiation dose was decreased by 62% in the low-dose scan, with significant difference （ P 〈 0. 05）. Conclusion High accuracy for the detection of nephrolithiasis and ureterelithiasis is obtained and the radiation dose is significantly decreased by using unenhanced 16-detector helical CT performed at a reduced tube current of 60 mAs for the patients less than 90 kg.