Detection of soft‐tissue abscess: Comparison of diffusion‐weighted imaging to contrast‐enhanced MRI

Abstract

Purpose To compare the diagnostic performances of diffusion‐weighted imaging (DWI)‐combined magnetic resonance imaging (MRI) performed without intravenous contrast material with gadolinium contrast material‐enhanced (CE) MRI for diagnosing soft‐tissue abscesses. Materials and Methods In all, 119 patients (mean age: 56 years) with skin and soft‐tissue infection who underwent contrast‐enhanced MRI with DWI ( b = 0‐800) were included. Two readers independently reviewed both image sets—nonenhanced conventional MR images (NECI)+DWI, and NECI+contrast enhanced fat‐suppressed T 1 ‐weighted imaging (CEFS T 1 )—for the presence of abscess. To compare the diagnostic performance for diagnosing abscess between NECI+DWI, and NECI+CEFS T 1 , McNemar tests for sensitivity and specificity, and areas under the receiver‐operating characteristic curves (AUC) analyses, were performed. Interobserver agreements (κ) were calculated for each image set. Results Forty of 119 patients were confirmed with abscess. Sensitivity and specificity were 90.0% and 88.6% for NECI+DWI, and 82.5% and 89.9% for NECI+CEFS T 1 in reader 1, whereas 77.5% and 88.6% for NECI+DWI, and 80.0% and 84.8% for NECI+CEFS T 1 in reader 2, respectively. There was no significant difference in sensitivities and specificities between NECI+DWI and NECI+CEFS T 1 (reader 1: P = 0.453, P = 0.999, reader 2: P = 0.999, P = 0.453, respectively). Likewise, AUC analyses demonstrated no significant difference between NECI+DWI and NECI+CEFS T 1 ( P = 0.53 in reader 1, P = 0.97 in reader 2). Interobserver agreement between the two readers was substantial in both image sets: 0.80 (NECI+DWI), and 0.76 (NECI+CEFS T 1 ). Conclusion Noncontrast‐enhanced MRI with DWI has comparable diagnostic performance to contrast‐enhanced MRI for diagnosing soft‐tissue abscesses. Level of Evidence: 3 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;47:60–68.