1 Department of Radiology, Hôpital Erasme, Université Libre de Bruxelles, Route de Lennik 808, Brussels B-1070, Belgium.
2 Department of Pneumology, Hôpital Erasme, Université Libre de Bruxelles, Brussels, Belgium.
AJR Am J Roentgenol. 2018 Feb;210(2):358-363. doi: 10.2214/AJR.17.18091. Epub 2017 Nov 22.
The objective of our study was to evaluate in vivo urinary calculus characterization with third-generation dual-source dual-energy CT (DECT) at reduced versus standard radiation dose.
One hundred fifty-three patients requiring unenhanced CT for suspected or known urolithiasis were prospectively included in our study. They underwent two acquisitions at reduced-dose CT (90 kV and 50 mAs; Sn150 kV and 31 mAs, where Sn denotes the interposition of a tin filter in the high-energy beam) and standard-dose CT (90 kV and 50 mAs; Sn150 kV and 94 mAs). One radiologist interpreted the reduced-dose examinations before the standard-dose examinations during the same session. Among 103 patients (23 women, 80 men; mean age ± SD, 50 ± 15 years; age range, 18-82 years) with urolithiasis, dedicated DECT software measured the maximal diameter and CT numbers, calculated the DECT number ratio, and labeled with a color code each calculus visualized by the radiologist as uric acid (UA) or non-UA. Volume CT dose index (CTDI) and dose-length product (DLP) were recorded.
The radiologist visualized 279 calculi on standard-dose CT and 262 on reduced-dose CT; 17 calculi were missed on reduced-dose CT, all of which were ≤ 3 mm. Among the 262 calculi visualized at both doses, the CT number ratio was obtained with the software for 227 calculi and was not different between the doses (p = 0.093). Among these 262 calculi, 197 were labeled at both doses; 194 of the 197 labeled calculi were labeled with the same color code. Among the 65 remaining calculi, 48 and 61 (all ≤ 5 mm) were not labeled at standard-dose and reduced-dose CT (p = 0.005), respectively. At reduced-dose CT, the mean CTDI was 2.67 mGy and the mean DLP was 102.2 mGy × cm.
With third-generation dual-source DECT, a larger proportion of calculi ≤ 5 mm are not characterized as UA or non-UA at a reduced dose.
本研究旨在评估第三代双源双能 CT（DECT）在降低与标准辐射剂量下对体内尿结石的特征描述能力。
本前瞻性研究共纳入 153 例疑似或已知尿路结石需行 CT 平扫的患者。他们分别行低剂量 CT（90kV 和 50mAs；Sn150kV 和 31mAs，其中 Sn 表示在高能束中插入锡滤器）和标准剂量 CT（90kV 和 50mAs；Sn150kV 和 94mAs）两次扫描。一位放射科医生在同一次检查中，先阅读低剂量扫描结果，再阅读标准剂量扫描结果。在 103 例（23 名女性，80 名男性；平均年龄 ± 标准差，50 ± 15 岁；年龄范围 18-82 岁）尿路结石患者中，专用 DECT 软件测量了结石的最大直径和 CT 值，计算了 DECT 比值，并根据放射科医生将每个结石标记为尿酸（UA）或非-UA，用颜色代码进行标记。记录容积 CT 剂量指数（CTDI）和剂量长度乘积（DLP）。
放射科医生在标准剂量 CT 上共观察到 279 个结石，在低剂量 CT 上共观察到 262 个结石；低剂量 CT 漏诊了 17 个结石，均<3mm。在两个剂量均能观察到的 262 个结石中，软件获得了 227 个结石的 CT 值比值，且两个剂量间无差异（p=0.093）。在这 262 个结石中，有 197 个在两个剂量上都有标记；197 个标记结石中有 194 个标记了相同的颜色代码。在其余 65 个结石中，48 个（均<5mm）和 61 个（均<5mm）分别在标准剂量和低剂量 CT 上未被标记（p=0.005）。在低剂量 CT 上，平均 CTDI 为 2.67mGy，平均 DLP 为 102.2mGy×cm。
使用第三代双源 DECT，在较低剂量下，比例较大的<5mm 结石不能被特征化为 UA 或非-UA。
