title: Effect of formalin fixation on biexponential modeling of diffusion decay in prostate tissue.
abstract: OBJECTIVE
  To evaluate the effect of formalin fixation on biexponential modeling of diffusion decay in prostate tissue.
  
  
  METHODS
  Three whole prostate specimens were imaged unfixed immediately postsurgery, and again after formalin fixation. Diffusion-weighted imaging was performed over an extended range of b-values and a biexponential model fitted to the signal decay curves.
  
  
  RESULTS
  Tissue fixation resulted in a 35%, 20%, and 20% reduction in mean apparent diffusion coefficient of the higher diffusivity fit component for the three organs, respectively, and a 64%, 57%, and 45% reduction in mean apparent diffusion coefficient of the lower diffusivity component. The mean signal fraction of the higher diffusivity component was increased by 23%, 5%, and 1%, respectively. The effect of fixation did not appear to vary according to tissue type or glandular zone.
  
  
  CONCLUSIONS
  Formalin fixed tissue appears to provide a stable model for detailed investigation of the microscopic biophysical basis of diffusion phenomena observed in vivo. Diffusivity changes that result from fixation may provide information about the microscopic environments of the biexponential components.
authors.affiliation: Discipline of Medical Radiation Sciences, Faculty of Health Sciences, University of Sydney, Sydney, New South Wales, Australia.
authors.forename: Roger
authors.initials: R
authors.lastname: Bourne
authors.forename: Andre
authors.initials: A
authors.lastname: Bongers
authors.forename: Ned
authors.initials: N
authors.lastname: Charles
authors.forename: Carl
authors.initials: C
authors.lastname: Power
authors.forename: Paul
authors.initials: P
authors.lastname: Sved
authors.forename: Geoffrey
authors.initials: G
authors.lastname: Watson
mesh_terms: D003198:Computer Simulation; D005404:Fixatives / Q000737:chemistry*; D005557:Formaldehyde / Q000737:chemistry*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D008954:Models, Biological; D011467:Prostate / Q000737:chemistry* / Q000473:pathology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D016707:Tissue Fixation / Q000379:methods*
chemical_list: D005404:Fixatives; D005557:Formaldehyde