title: Characteristic magnetic resonance features of focal autoimmune pancreatitis useful for differentiation from pancreatic cancer.
abstract: OBJECTIVE
  To identify characteristic magnetic resonance (MR) features of focal autoimmune pancreatitis (f-AIP) useful for differentiation from pancreatic cancer (PC).
  
  
  METHODS
  We retrospectively analyzed MR imaging findings of 20 f-AIP lesions and 40 PC lesions smaller than 40 mm in diameter. On fat-suppressed T2-weighted images and dynamic contrast-enhanced fat-suppressed T1-weighted images (DCE-T1WI), we classified MR features of internal signal intensity for each lesion into homogeneous, speckled, or target type. We assessed the sensitivity, specificity, and accuracy of these findings in the diagnosis of f-AIP. We also investigated the incidence of previously reported findings for differentiation between f-AIP and PC.
  
  
  RESULTS
  Speckled enhancement within a hypointense or isointense lesion on pancreatic phase DCE-T1WI (speckled type) was observed more frequently in f-AIP than in PC, with high sensitivity, high specificity, and high accuracy. Hypointensity to hyperintensity surrounding a less enhanced focal area on DCE-T1WIs (target type) and upper stream main pancreatic duct dilatation were observed more frequently in PC than in f-AIP.
  
  
  CONCLUSIONS
  Speckled enhancement inside an f-AIP lesion on pancreatic phase DCE-T1WI was useful for differentiation from PC.
authors.affiliation: Department of Radiology, Shinshu University School of Medicine, 3-1-1 Asahi, Matsumoto, 390-8621, Japan. ysgym@shinshu-u.ac.jp
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Sugiyama
authors.forename: Yasunari
authors.initials: Y
authors.lastname: Fujinaga
authors.forename: Masumi
authors.initials: M
authors.lastname: Kadoya
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Ueda
authors.forename: Masahiro
authors.initials: M
authors.lastname: Kurozumi
authors.forename: Hideaki
authors.initials: H
authors.lastname: Hamano
authors.forename: Shigeyuki
authors.initials: S
authors.lastname: Kawa
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001327:Autoimmune Diseases / Q000473:pathology*; D049448:Cholangiopancreatography, Magnetic Resonance; D003287:Contrast Media; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D010190:Pancreatic Neoplasms / Q000473:pathology; D010195:Pancreatitis / Q000473:pathology*; D012189:Retrospective Studies; D012680:Sensitivity and Specificity
chemical_list: D003287:Contrast Media