title: Pancreatic duct "Icicle sign" on MRI for distinguishing autoimmune pancreatitis from pancreatic ductal adenocarcinoma in the proximal pancreas.
abstract: OBJECTIVE
  To determine reliable MRI features of autoimmune pancreatitis (AIP) in the proximal pancreas that could allow its differentiation from pancreatic ductal adenocarcinoma (PDAC).
  
  
  METHODS
  Twenty-three patients with AIP and 61 patients with PDAC in the proximal pancreas underwent MRI. Two observers analyzed MRI for lesion morphology, hypointensity degree on T1-weighted images, enhancement pattern during dynamic phases, capsule-like rim, presence of cysts and duct penetrating sign, morphology of bile duct, and icicle appearance and tortuosity of the upstream pancreatic duct. Sensitivity and specificity for the diagnosis of AIP were calculated for each category or combined.
  
  
  RESULTS
  When isointensity on the portal and late phase of MRI and/or the icicle sign of pancreatic duct are applied, 100 % sensitivity for the diagnosis of AIP in the proximal pancreas was achieved. Applying both mild T1 hypointensity similar to the spleen and the icicle sign enabled 100 % specificity for the diagnosis of AIP by differentiating it from PDAC.
  
  
  CONCLUSIONS
  The combination of the icicle sign in the upstream pancreatic duct and mild T1 hypointensity or isointensity on portal and late phase of dynamic MRI could be reliable MR features for the diagnosis of AIP in the proximal pancreas by allowing its differentiation from PDAC.
  
  
  CONCLUSIONS
  • The icicle sign of the pancreatic duct is useful for diagnosing AIP. • Mild T1 hypointensity similar to the spleen is useful for diagnosing AIP. • Isointensity on portal and late phases MRI is useful for diagnosing AIP.
authors.affiliation: Department of Radiology and Center for Imaging Science, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea.
authors.forename: Hae Jin
authors.initials: HJ
authors.lastname: Kim
authors.forename: Young Kon
authors.initials: YK
authors.lastname: Kim
authors.forename: Woo Kyoung
authors.initials: WK
authors.lastname: Jeong
authors.forename: Won Jae
authors.initials: WJ
authors.lastname: Lee
authors.forename: Dongil
authors.initials: D
authors.lastname: Choi
mesh_terms: D000230:Adenocarcinoma / Q000473:pathology; D000328:Adult; D000368:Aged; D001327:Autoimmune Diseases / Q000175:diagnosis*; D001652:Bile Ducts / Q000473:pathology; D021441:Carcinoma, Pancreatic Ductal / Q000175:diagnosis*; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D010183:Pancreatic Ducts / Q000473:pathology*; D010190:Pancreatic Neoplasms / Q000175:diagnosis*; D010195:Pancreatitis / Q000175:diagnosis*; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D055815:Young Adult