Iterative Reconstructions versus Filtered Back-Projection for Urinary Stone Detection in Low-Dose CT

Rationale and Objectives To evaluate prospectively, in patients with suspected or known urinary stone disease, the image quality and diagnostic confidence of nonenhanced abdominal low-dose computed tomography (CT) with iterative reconstruction (IR) compared to filtered back-projection (FBP). Materials and Methods Fifty consecutive patients with suspected ( n  = 33) or known ( n  = 17) urinary stone disease underwent nonenhanced abdominal low-dose CT (120 kVp, 30 effective mAs, 1.6 ± 0.5 mSv). Reconstructions were performed with sinogram-affirmed IR and with FBP. Attenuation (in Hounsfield units) was measured in subcutaneous fat and urinary bladder; image noise was determined. Two readers assessed image quality, number and location of urinary calculi were recorded, and diagnostic confidence was assessed. Statistical analyses included Mann-Whitney, Friedman's two-way, Wilcoxon signed rank, Pearson's, and Spearman's rank order correction tests. Results Attenuation of urinary bladder ( P  = .208, reader 1; P  = .123, reader 2) and fat ( P  = .568, reader 1; P  = .834, reader 2) was similar among FBP and IR datasets. Image noise was reduced in IR datasets by 40.1% ( P P P P  = .102, reader 1; P  = .059, reader 2). Diagnostic confidence regarding identification of urinary calculi improved with IR ( P P Conclusion IR improves image quality and confidence for diagnosing urinary stone disease in abdominal low-dose CT.