Added value of diffusion-weighted magnetic resonance imaging for the detection of pancreatic fluid collection infection

Objectives To investigate the added value of diffusion-weighted (DW) magnetic resonance (MR) imaging in the detection of infection in pancreatic fluid collections (PFC). Methods Forty-patients with PFC requiring endoscopic-transmural drainage underwent conventional-MR and DW-MR imaging (b = 1000 s/mm 2 ) before endoscopy. MR images were divided into two sets (set1, conventional-MR; set2, conventional-MR, DW-MR and ADC maps) and randomized. Two independent readers performed qualitative and quantitative (apparent diffusion coefficient, ADC) image analysis. Bacteriological analysis of PFC content was the gold standard. Non-parametric tests were used for comparisons. Sensitivity, specificity, negative predictive value (NPV), positive predictive value (PPV) and accuracy were calculated for the two sets for both readers. Receiver operating characteristic curves (ROC) were drawn to assess quantitative DW-MR imaging diagnostic performance. Results For both readers, sensitivity, specificity, NPV, PPV and accuracy for infected PFCs were higher for set2 ( P > .05). ADC were lower in infected versus non-infected PFCs ( P ≤ .031). Minimum ADC cut-off: 1,090×10 -3 mm 2 /s for reader 1 and 1,012×10 -3 mm 2 /s for reader 2 (sensitivity and specificity 67 % and 96 % for both readers). Conclusion Qualitative information provided by DW-MR may help to assess PFCs infection. Infected PFCs show significantly lower ADCs compared to non-infected ones. Key Points • DW improves MR diagnostic accuracy to detect infection of PFC • Infected PFCs show lower ADC compared to non-infected ones (P < .031) • DW-MR images are easy to interpret especially for non-experienced radiologist