title: Autoimmune pancreatitis: differentiation from pancreatic carcinoma and normal pancreas on the basis of enhancement characteristics at dual-phase CT.
abstract: OBJECTIVE
  The purposes of this study were to define the pancreatic enhancement of autoimmune pancreatitis at dual-phase CT and to compare it with that of pancreatic carcinoma and a normal pancreas.
  
  
  METHODS
  Dual-phase CT scans of 101 patients (43 with autoimmune pancreatitis, 13 cases of which were focal; 33 with pancreatic carcinoma, and 25 with a normal pancreas) were evaluated. One radiologist measured the CT attenuation of the pancreatic parenchyma and pancreatic masses in both the pancreatic and hepatic phases of imaging. The mean CT attenuation value of the pancreatic parenchyma in patients with autoimmune pancreatitis was compared with that in patients with a normal pancreas. The mean CT attenuation value of the focal masses in the focal form of autoimmune pancreatitis was compared with that of carcinomas.
  
  
  RESULTS
  In the pancreatic phase, the mean CT attenuation value of the pancreatic parenchyma in patients with autoimmune pancreatitis was significantly lower than that in patients with a normal pancreas (autoimmune pancreatitis, 85 HU; normal pancreas, 104 HU; p < 0.05). In the hepatic phase, however, the mean CT attenuation values were not significantly different (autoimmune pancreatitis, 96 HU; normal pancreas, 89 HU; p = 0.6). In the pancreatic phase, the mean CT attenuation value of the mass in autoimmune pancreatitis was not significantly different from that of carcinoma (autoimmune pancreatitis, 71 HU; carcinoma, 59 HU; p = 0.06), but in the hepatic phase, the value was significantly higher than that of carcinoma (autoimmune pancreatitis, 90 HU; carcinoma, 64 HU; p < 0.001).
  
  
  CONCLUSIONS
  At dual-phase CT, the enhancement patterns of the pancreas and pancreatic masses in patients with autoimmune pancreatitis are different from those of pancreatic carcinoma and normal pancreas.
authors.affiliation: Department of Radiology, Mayo Clinic, 200 First St. SW, Rochester, MN 55905, USA.
authors.forename: Naoki
authors.initials: N
authors.lastname: Takahashi
authors.forename: Joel G
authors.initials: JG
authors.lastname: Fletcher
authors.forename: David M
authors.initials: DM
authors.lastname: Hough
authors.forename: Jeff L
authors.initials: JL
authors.lastname: Fidler
authors.forename: Akira
authors.initials: A
authors.lastname: Kawashima
authors.forename: Jayawant N
authors.initials: JN
authors.lastname: Mandrekar
authors.forename: Suresh T
authors.initials: ST
authors.lastname: Chari
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001327:Autoimmune Diseases / Q000000981:diagnostic imaging*; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010179:Pancreas / Q000000981:diagnostic imaging*; D010190:Pancreatic Neoplasms / Q000000981:diagnostic imaging*; D010195:Pancreatitis / Q000000981:diagnostic imaging*; D011856:Radiographic Image Enhancement; D014057:Tomography, X-Ray Computed / Q000379:methods*