title: Fibrosis and pancreatic lesions: counterintuitive behavior of the diffusion imaging-derived structural diffusion coefficient d.
abstract: BACKGROUND
  Stroma reaction leading to fibrosis is the most characteristic histopathological feature of both pancreatic carcinoma and chronic pancreatitis with increased fibrosis compared with healthy pancreatic tissue and further increased fibrosis during radiochemotherapy. Recent studies using intravoxel incoherent motion-derived parameters did not show differences for structural diffusion constant D between these 2 diseases. The aim of this study was to verify the hypothesis that D correlates with the histopathological grade of fibrosis in pancreatic lesions.
  
  
  METHODS
  We included 15 patients with histopathologically proven pancreatic carcinoma and 9 patients with histopathologically proven focal chronic pancreatitis. Diffusion-weighted magnetic resonance imaging was performed using 10 b values between 25 and 800 s/mm² before surgery. We calculated the apparent diffusion coefficient and the intravoxel incoherent motion-derived parameters D and f within tumors and focal chronic pancreatitis. The resected tissue was evaluated with regard to the grade of fibrosis.
  
  
  RESULTS
  Fourteen patients were found to have moderate fibrosis and 10 patients had severe fibrosis. The difference between the D values for the moderate and severe fibrosis was significant with mean (SD) D value of 1.02 × 10⁻³ (0.48 × 10⁻³ mm/s) and mean (SD) D of 1.22 × 10⁻³ (0.76 × 10⁻³) mm²/s. There were no significant differences for the f and ADC values.
  
  
  CONCLUSIONS
  Contrary to our hypothesis, D rises from moderate to severe fibrosis. It seems that cellular complexes surrounded by fibrosis provide more structural limitations than does fibrosis alone. Our data suggest that D is not intuitively related to the degree of fibrosis. Compared with healthy tissue, D is reduced in moderate fibrosis but increases when severe fibrosis is present.
authors.affiliation: Department of Diagnostic and Interventional Radiology, Faculty of Medicine Mannheim, University of Heidelberg, Germany.
authors.forename: Miriam
authors.initials: M
authors.lastname: Klauss
authors.forename: Matthias M
authors.initials: MM
authors.lastname: Gaida
authors.forename: Andreas
authors.initials: A
authors.lastname: Lemke
authors.forename: Katharina
authors.initials: K
authors.lastname: Grünberg
authors.forename: Dirk
authors.initials: D
authors.lastname: Simon
authors.forename: Moritz N
authors.initials: MN
authors.lastname: Wente
authors.forename: Stefan
authors.initials: S
authors.lastname: Delorme
authors.forename: Hans-Ulrich
authors.initials: HU
authors.lastname: Kauczor
authors.forename: Lars
authors.initials: L
authors.lastname: Grenacher
authors.forename: Bram
authors.initials: B
authors.lastname: Stieltjes
mesh_terms: D000368:Aged; D000465:Algorithms; D003937:Diagnosis, Differential; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D005355:Fibrosis; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D008875:Middle Aged; D010179:Pancreas / Q000473:pathology*; D010190:Pancreatic Neoplasms / Q000473:pathology*; D010195:Pancreatitis / Q000473:pathology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity