Usefulness of Low-dose Nonenhanced Computed Tomography With Iterative Reconstruction for Evaluation of Urolithiasis: Diagnostic Performance and Agreement between the Urologist and the Radiologist

Abstract

OBJECTIVE To evaluate the efficacy of low-dose nonenhanced computed tomography (LDCT) with iterative reconstruction (IR) technique for urologists to detect urolithiasis by comparing diagnostic performance and interobserver agreement between the urologist and the uroradiologist. PATIENTS AND METHODS We evaluated the 116 patients with urinary stones (n = 197) using both conventional-dose nonenhanced computed tomography (CT) using filtered back projection (CDCT-FBP) and LDCT-IR. Scans were interpreted for stone characteristics, objective image noise, and subjective image assessment. Diagnostic performance and interobserver agreement of LDCT-IR were assessed between 1 urologist and 1 radiologist. RESULTS There were no significant differences in all stones. The average effective dose (mSV) in the all size groups was 5.92 (CDCT-FBP) and 1.39 (LDCT-IR), respectively (P < .001). The average effective dose reduction rate was 76.6%, allowing minimal additional radiation exposure from simultaneous CT. Objective image noise was higher in LDCT-IR (20.0-26.2; P < .01), but there was no significant difference in the Hounsfield unit between both CT protocols (52.3 and 56.7; P = .103). There were no cases of any unacceptable images in subjective image assessment. The sensitivity and specificity of LDCT-IR were 99.1%-100.0% with a diagnostic accuracy of 99.1%-100% for stones >= 3 mm. Diagnostic performance was similar between the urologist and the radiologist. Interobserver agreement of LDCT-IR between the 2 reviewers was high with kappa values (0.901-1.000). CONCLUSION LDCT-IR provided an excellent diagnostic performance and interobserver agreement between the urologist and the uroradiologist, reducing radiation exposure significantly; in real settings, the urologist should consider replacing LDCT-IR as the standard examination for detecting urolithiasis. (C) 2015 Elsevier Inc.