title: Comparison of MRI-based and CT/MRI fusion-based postimplant dosimetric analysis of prostate brachytherapy.
abstract: OBJECTIVE
  The aim of this study was to compare the outcomes between magnetic resonance imaging (MRI)-based and computed tomography (CT)/MRI fusion-based postimplant dosimetry methods in permanent prostate brachytherapy.
  
  
  METHODS
  Between October 2004 and March 2006, a total of 52 consecutive patients with prostate cancer were treated by brachytherapy, and postimplant dosimetry was performed using CT/MRI fusion. The accuracy and reproducibility were prospectively compared between MRI-based dosimetry and CT/MRI fusion-based dosimetry based on the dose-volume histogram (DVH) related parameters as recommended by the American Brachytherapy Society.
  
  
  RESULTS
  The prostate volume was 15.97+/-6.17 cc (mean+/-SD) in MRI-based dosimetry, and 15.97+/-6.02 cc in CT/MRI fusion-based dosimetry without statistical difference. The prostate V100 was 94.5% and 93.0% in MRI-based and CT/MRI fusion-based dosimetry, respectively, and the difference was statistically significant (p=0.002). The prostate D90 was 119.4% and 114.4% in MRI-based and CT/MRI fusion-based dosimetry, respectively, and the difference was statistically significant (p=0.004).
  
  
  CONCLUSIONS
  Our current results suggested that, as with fusion images, MR images allowed accurate contouring of the organs, but they tended to overestimate the analysis of postimplant dosimetry in comparison to CT/MRI fusion images. Although this MRI-based dosimetric discrepancy was negligible, MRI-based dosimetry was acceptable and reproducible in comparison to CT-based dosimetry, because the difference between MRI-based and CT/MRI fusion-based results was smaller than that between CT-based and CT/MRI fusion-based results as previously reported.
authors.affiliation: Department of Radiology, Gifu University School of Medicine, Gifu City, Japan. osa-mu@umin.ac.jp
authors.forename: Osamu
authors.initials: O
authors.lastname: Tanaka
authors.forename: Shinya
authors.initials: S
authors.lastname: Hayashi
authors.forename: Masayuki
authors.initials: M
authors.lastname: Matsuo
authors.forename: Kota
authors.initials: K
authors.lastname: Sakurai
authors.forename: Masahiro
authors.initials: M
authors.lastname: Nakano
authors.forename: Sunaho
authors.initials: S
authors.lastname: Maeda
authors.forename: Kimihiro
authors.initials: K
authors.lastname: Kajita
authors.forename: Takashi
authors.initials: T
authors.lastname: Deguchi
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Hoshi
mesh_terms: D001918:Brachytherapy; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D015588:Observer Variation; D011467:Prostate / Q000000981:diagnostic imaging* / Q000473:pathology*; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology* / Q000532:radiotherapy; D011879:Radiotherapy Dosage; D014057:Tomography, X-Ray Computed / Q000379:methods*