title: DWI findings of autoimmune pancreatitis: comparison between symptomatic and asymptomatic patients.
abstract: OBJECTIVE
  To compare the MR findings including diffusion-weighted imaging (DWI) between symptomatic and asymptomatic patients with autoimmune pancreatitis (AIP) and to determine whether DWI can be used as an objective biomarker for symptomatic AIP, which is considered an indication for steroid therapy.
  
  
  METHODS
  This retrospective study was approved by our institutional review board. MRI scans from 37 patients with AIP (symptomatic, n = 19; asymptomatic, n = 18) were retrospectively evaluated. The imaging studies were performed on a 1.5 Tesla scanner and assessed for parenchymal enlargement, narrowing of the main pancreatic duct, hypointensity on fat-suppressed T1-weighted images (FS-T1WI), a capsule-like rim, extrapancreatic lesions, and hyperintensity on DWI. The findings were compared by univariate and multivariate logistic regression analysis. Apparent diffusion coefficient (ADC) values were also calculated.
  
  
  RESULTS
  Multivariate analysis showed that hyperintensity on DWI were most significantly associated with the symptoms of AIP (odds ratio = 28.2; P = 0.003). Interobserver agreement for DWI was also high. The ADC values were significantly lower in symptomatic than in asymptomatic patients (0.94 ± 0.17 versus 1.16 ± 0.16 × 10(-3) mm(2)/s, P < 0.001). Receiver operating characteristic curve analysis of the ADC values to differentiate between symptomatic and asymptomatic patients showed that sensitivity was 68.4%, specificity 83.3%, and AUC 0.74.
  
  
  CONCLUSIONS
  Signal intensity on DWI and ADC value were well correlated with the active symptoms of AIP patients. DWI may be useful as an objective biomarker for determining the indication for steroid therapy.
authors.affiliation: Department of Radiology, University of Occupational and Environmental Health, Yahatanishi-ku, Kitakyushu, Fukuoka, Japan.
authors.forename: Hodaka
authors.initials: H
authors.lastname: Oki
authors.forename: Yoshiko
authors.initials: Y
authors.lastname: Hayashida
authors.forename: Haruka
authors.initials: H
authors.lastname: Oki
authors.forename: Shingo
authors.initials: S
authors.lastname: Kakeda
authors.forename: Takatoshi
authors.initials: T
authors.lastname: Aoki
authors.forename: Masashi
authors.initials: M
authors.lastname: Taguchi
authors.forename: Masaru
authors.initials: M
authors.lastname: Harada
authors.forename: Yukunori
authors.initials: Y
authors.lastname: Korogi
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001327:Autoimmune Diseases / Q000175:diagnosis*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D010179:Pancreas / Q000473:pathology*; D010195:Pancreatitis / Q000175:diagnosis*; D012372:ROC Curve; D012189:Retrospective Studies; D012680:Sensitivity and Specificity
keywords: apparent diffusion coefficient; autoimmune pancreatitis; diffusion-weighted image; fat-suppressed T1-weighted images; magnetic resonance imaging