title: Subtraction color map of contrast-enhanced and unenhanced CT for the prediction of pancreatic necrosis in early stage of acute pancreatitis.
abstract: OBJECTIVE
  The objective of our study was to evaluate the accuracy of subtraction color-map images created from contrast-enhanced CT (CECT) and unenhanced CT for the diagnosis of pancreatic necrosis in the early stage of acute pancreatitis.
  
  
  METHODS
  Forty-eight patients underwent unenhanced CT and CECT within 72 hours from the onset of acute pancreatitis. Subtraction color-map images were created from unenhanced CT and CECT using a 3D nonrigid registration method. Three radiologists reviewed two image sets: CECT alone and subtraction color-map images in conjunction with CECT. Readers evaluated each image set for the presence of pancreatic necrosis. The reference standard for pancreatic necrosis was CT or MRI 1 week or more after the onset of acute pancreatitis. The performance of each image set for the prediction of pancreatic necrosis was calculated and compared using the McNemar test.
  
  
  RESULTS
  Eleven of the 48 patients developed pancreatic necrosis. There were no technical failures creating the subtraction images. The sensitivity, specificity, and accuracy for predicting pancreatic necrosis with CECT were 64%, 97%, and 90%, respectively, for reader 1; 73%, 87%, and 83% for reader 2; and 73%, 87%, and 83% for reader 3. The sensitivity, specificity, and accuracy for predicting pancreatic necrosis with the subtraction color maps were 100%, 100%, and 100%, respectively, for reader 1; 100%, 95%, and 96% for reader 2; and 82%, 92%, and 90% for reader 3. Accuracy significantly improved with the addition of subtraction color maps compared with CECT alone for reader 1 (p = 0.03) and reader 2 (p = 0.02) but not for reader 3 (p = 0.37).
  
  
  CONCLUSIONS
  A subtraction color map is accurate in the diagnosis of pancreatic necrosis in the early stage of acute pancreatitis.
authors.affiliation: 1 Department of Radiology, Mayo Clinic, 200 First St SW, Rochester, MN 55905.
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Tsuji
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: Brendan P
authors.initials: BP
authors.lastname: McMenomy
authors.forename: David M
authors.initials: DM
authors.lastname: Lewis
authors.forename: Santhi S
authors.initials: SS
authors.lastname: Vege
authors.forename: Suresh T
authors.initials: ST
authors.lastname: Chari
authors.forename: Cynthia H
authors.initials: CH
authors.lastname: McCollough
authors.forename: Katharine L
authors.initials: KL
authors.lastname: Grant
authors.forename: Ernst
authors.initials: E
authors.lastname: Klotz
mesh_terms: D018806:APACHE; D003116:Color; D003287:Contrast Media; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D007472:Iohexol; D007902:Length of Stay / Q000706:statistics & numerical data; D008297:Male; D008875:Middle Aged; D009336:Necrosis; D010195:Pancreatitis / Q000000981:diagnostic imaging* / Q000401:mortality / Q000473:pathology; D011237:Predictive Value of Tests; D011857:Radiographic Image Interpretation, Computer-Assisted; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D013382:Subtraction Technique; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D003287:Contrast Media; D007472:Iohexol