title: Dynamic susceptibility contrast perfusion imaging of radiation effects in normal-appearing brain tissue: changes in the first-pass and recirculation phases.
abstract: OBJECTIVE
  To identify radiation-induced changes in the cerebral vasculature of healthy tissue in the first four months following radiotherapy through the analysis of dynamic-susceptibility contrast perfusion imaging.
  
  
  METHODS
  Dynamic gradient-echo imaging was performed on 22 patients during injection of a bolus of Gd-DTPA contrast. The relative cerebral blood volume (rCBV), maximum DeltaR2* of the first passage of the bolus, and a recirculation parameter were derived from gamma-variate fits of the dynamic data. The white matter (WM) rCBV and peak heights were estimated through correlation with segmented T1-weighted images. A percent recovery to baseline was also computed to further describe the recirculation phase.
  
  
  RESULTS
  A significant elevation of the recirculation phase was observed at doses>15 Gy at two months following radiotherapy. This was reflected in an increased recirculation parameter in the fitted curves in the 15-30, 30-45, and >45 Gy dose groups to 2.8%, 3.8%, and 2.4% above the <15 Gy voxels, as well as in a decline in percent recovery to baseline. A trend toward lower rCBV and peak heights was observed at that same time point.
  
  
  CONCLUSIONS
  The observed results suggest a dose-dependent decline in vessel density and increase in vascular permeability and/or tortuosity in irradiated normal-appearing brain tissue at two months following radiotherapy.
authors.affiliation: Department of Radiology, University of California-San Francisco, San Francisco, California 94143-2532, USA. Michael.Lee@mrsc.ucsf.edu
authors.forename: Michael C
authors.initials: MC
authors.lastname: Lee
authors.forename: Soonmee
authors.initials: S
authors.lastname: Cha
authors.forename: Susan M
authors.initials: SM
authors.lastname: Chang
authors.forename: Sarah J
authors.initials: SJ
authors.lastname: Nelson
mesh_terms: D000328:Adult; D000368:Aged; D001810:Blood Volume / Q000528:radiation effects*; D001921:Brain / Q000098:blood supply / Q000528:radiation effects*; D001932:Brain Neoplasms / Q000503:physiopathology / Q000532:radiotherapy*; D002560:Cerebrovascular Circulation; D003287:Contrast Media; D004307:Dose-Response Relationship, Radiation; D005260:Female; D019786:Gadolinium DTPA; D005910:Glioma / Q000503:physiopathology / Q000532:radiotherapy*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D008875:Middle Aged; D009010:Monte Carlo Method; D018709:Statistics, Nonparametric
chemical_list: D003287:Contrast Media; D019786:Gadolinium DTPA