LAUSR

ObjectivesTo intraindividually compare the diagnostic performance of CT and MRI in differentiating non-diffuse-type autoimmune pancreatitis (AIP) from pancreatic ductal adenocarcinoma (PDA).MethodsSixty-one patients with non-diffuse-type AIP and 122 patients with PDA, who underwent dynamic contrast-enhanced CT and MRI with MR pancreatography, were included. Two blinded radiologists independently rated their confidence in differentiating the two diseases on a 5-point scale, and the diagnostic performances of CT and MRI were compared. The presence of key imaging features to differentiate AIP and PDA were compared between CT and MRI.ResultsThe area under the receiver operating characteristic curve was significantly greater on MRI (0.993–0.995) than on CT (0.953–0.976) for both raters (p≤0.035). The sensitivities of MRI were higher than those of CT for the diagnosis of AIP (88.5–90.2% vs. 77–80.3%, p≤0.07) and PDA (97.5–99.2% vs. 91.8–94.3%, p≤0.031) for both raters, although the difference for AIP was statistically marginal (p=0.07) for rater 1. In AIP, multiple pancreatic masses, delayed homogeneous enhancement of the pancreatic mass, and multiple main pancreatic duct (MPD) strictures were observed significantly more frequently using MRI than CT (p≤0.008). In PDA, discrete pancreatic mass and MPD stricture were observed significantly more frequently using MRI than CT (p≤0.012).ConclusionsThe diagnostic performance of MRI is better for differentiating non-diffuse-type AIP from PDA, which is due to the superiority of MRI over CT in demonstrating the key distinguishing features of both diseases.Key Points• Imaging differential diagnosis of non-diffuse-type AIP and PDA is challenging.• MRI has better diagnostic performance than CT in differentiating non-diffuse-type AIP from PDA.• MRI is superior to CT in demonstrating key distinguishing features of non-diffuse-type AIP and PDA.