PURPOSE To determine whether a modified non-contrast very low-dose computed tomography (VLD-CT) protocol is applicable for confirmation of known urolithiasis. METHODS AND MATERIALS Consecutive adult patients with a CT scan showing urinary tract stone(s) between 6/2017-12/2018 were included. They were referred to a modified VLD-CT protocol if stone presence was equivocal or if stone location needed reassessment before an endourological interventional procedure. The scanned area was limited to the level of initial stone location caudally. Data on patients' demographics andbody mass index, were collected. The scanned length and radiation dose were calculated. Images were reviewed by two radiologists who assessed stone size and location. Follow-up reference standard included stone passage, surgical removal, and other imaging and clinical information. RESULTS Sixty-three patients [63 stones, mean BMI 28.7 (range 19-41.9)] were included. VLD-CTs revealed 31 stones in 31 patients, with a mean stone length of 5.5 mm. Fifteen stones remained at the same location, and 16 had migrated, of which two appeared in the bladder. Thirty-two stones were not observed on VLD-CT. The mean span scanned on the VLD-CT was 274 mm (± 80). The average radiation exposure was 1.47 mGy (range 1.09-3.3), and the absorbed dose was 0.77 mSv (range 0.39-1.43), compared to 10.24 mGy (range 1.75-28.9) and 7.87 mSv (range 1.44-18.5) in the previous scan. The mean radiation dose reduction between scans was 89%. On follow-up, all VLD-CT findings were confirmed. CONCLUSION A modified imaging protocol is applicable for confirmation of stone presence and location by utilizing very low-dose radiation exposure.

中文翻译：

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用于确认泌尿系结石存在的极低剂量计算机断层扫描。

目的 确定改良的非对比剂极低剂量计算机断层扫描 (VLD-CT) 协议是否适用于确认已知的尿石症。方法和材料 包括在 6/2017-12/2018 之间进行 CT 扫描显示尿路结石的连续成年患者。如果结石存在模棱两可，或者在泌尿外科介入手术前需要重新评估结石位置，则将他们转诊至修改后的 VLD-CT 方案。扫描区域仅限于尾部初始结石位置的水平。收集了有关患者人口统计学和体重指数的数据。计算扫描长度和辐射剂量。图像由评估结石大小和位置的两名放射科医生审查。随访参考标准包括结石排出、手术切除、以及其他影像和临床信息。结果 包括 63 名患者 [63 颗结石，平均 BMI 28.7（范围 19-41.9）]。VLD-CT 显示 31 名患者有 31 颗结石，平均结石长度为 5.5 mm。15 块结石留在同一位置，16 块已迁移，其中 2 块出现在膀胱中。VLD-CT 未观察到 32 颗结石。VLD-CT 扫描的平均跨度为 274 mm (± 80)。平均辐射暴露量为 1.47 mGy（范围 1.09-3.3），吸收剂量为 0.77 mSv（范围 0.39-1.43），而之前为 10.24 mGy（范围 1.75-28.9）和 7.87 mSv（范围 1.44-18）。扫描。两次扫描之间的平均辐射剂量降低为 89%。在随访中，所有 VLD-CT 结果均得到证实。