title: MRI before and after external beam intensity-modulated radiotherapy of patients with prostate cancer: the feasibility of monitoring of radiation-induced tissue changes using a dynamic contrast-enhanced inversion-prepared dual-contrast gradient echo sequence.
abstract: OBJECTIVE
  To identify and quantify suitable pharmacokinetic MRI parameters for monitoring tissue changes after external beam intensity-modulated radiotherapy of prostate cancer.
  
  
  METHODS
  Six patients with biopsy-proven prostate cancer (initial PSA, 6.0-81.4 ng/ml) underwent MRI at 1.5 T using a combined endorectal/body phased-array coil and a dynamic contrast-enhanced inversion-prepared dual-contrast gradient echo sequence (T1/T2(*)w; 1.65 s temporal resolution). MRI was performed before and immediately after radiotherapy, at 3 months and at 1 year. Perfusion, blood volume, mean transit time, delay, dispersion, interstitial volume, and extraction coefficient were calculated in prostate cancer and normal prostate for all four time points using a sequential 3-compartment model.
  
  
  RESULTS
  Prostate cancer and normal prostate tissue showed a statistically significant decrease in perfusion (p=0.006, p=0.001) and increase in extraction coefficient (p=0.004, p<0.001). For prostate cancer, there was also a decrease in vascular volume (p=0.034). The other parameters investigated showed no statistically significant changes. Statistically significant differences between prostate cancer and normal prostate tissue were only observed before radiotherapy, when prostate cancer showed significantly higher perfusion (1.84 vs. 0.12 ml/cm(3)min, p=0.028) and a smaller extraction coefficient (0.42 vs. 0.64, p=0.028).
  
  
  CONCLUSIONS
  Two pharmacokinetic parameters, perfusion and extraction coefficient, appear to be suitable candidates for monitoring the response to percutaneous intensity-modulated radiotherapy of prostate cancer.
authors.affiliation: Department of Radiology, Charité-Universitätsmedizin Berlin, Germany. tobias.franiel@charite.de
authors.forename: Tobias
authors.initials: T
authors.lastname: Franiel
authors.forename: Lutz
authors.initials: L
authors.lastname: Lüdemann
authors.forename: Matthias
authors.initials: M
authors.lastname: Taupitz
authors.forename: Dirk
authors.initials: D
authors.lastname: Böhmer
authors.forename: Dirk
authors.initials: D
authors.lastname: Beyersdorff
mesh_terms: D000368:Aged; D003287:Contrast Media; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D017430:Prostate-Specific Antigen / Q000097:blood; D011471:Prostatic Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D050397:Radiotherapy, Intensity-Modulated / Q000009:adverse effects*
chemical_list: D003287:Contrast Media; D017430:Prostate-Specific Antigen