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

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 T₁-weighted imaging (CEFST₁)—for the presence of abscess. To compare the diagnostic performance for diagnosing abscess between NECI+DWI, and NECI+CEFST₁, 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+CEFST₁ in reader 1, whereas 77.5% and 88.6% for NECI+DWI, and 80.0% and 84.8% for NECI+CEFST₁ in reader 2, respectively. There was no significant difference in sensitivities and specificities between NECI+DWI and NECI+CEFST₁ (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+CEFST₁ (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+CEFST₁). 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.