Imaging characteristics of autoimmune pancreatitis:MRI versus CT

Abstract

Objective To compare CT and MRI for demonstrating imaging characteristics of autoimmune pancreatitis (AIP). Methods Both CT and MR imaging were performed on 23 patients with AIP, proved histopathologicaUy or clinically by corticosteroid trial. Findings including presence of pancreatic enlargement, density or signal intensity abnormalities on unenhanced CT or MRI, decreased enhancement on arterial phase, moderate enhancement on delayed phase, capsule-like rim, diffuse irregular narrowing of main pancreatic duct and common bile duct stricture were retrospectively analyzed. The frequencies of demonstrating these imaging features were compared between CT and MRJ, using the paired Chi-square tests.Results Of the 23 cases, CT and Mill both showed pancreatic enlargement in 21 cases, diffuse (n=16) and focal (n=5). Density or signal intensity abnormalities on non-enhanced scans (CT vs MR/ : 4 vs 23), moderate enhancement on delayed images (CT vs MRI : 10 vs 19), capsule-like rim (CT vs MRI : 5 vs 16) and diffuse irregular narrowing of main pancreatic duct (CT vs MRI : 0 vs 8) were more frequently seen on MRI than on CT with statistically significant difference (X2 were 17. 05,7. 11,9. 09,6. 12 respectively, P 0. 05). Conclusion For demonstrating density or signal intensity abnormalities on non-enhanced scans, enhancement on delayed phase, capsule-like rim and irregular narrowing of pancreatic duct, MRI is superior to CT. As for other imaging features, especially pancreatic enlargement, MRI is comparable to CT. Key words: Pancreatitis ; Autoimmune diseases; Tomography; X-ray computed; Magnetic resonance imaging