title: Regional treatment margins for prostate brachytherapy.
abstract: OBJECTIVE
  This study quantified the treatment margin (TM) around the prostate that received 100% of the prescribed dose and analyzed postimplant dosimetry in different regions of the prostate for (125)I seed implants.
  
  
  METHODS
  An average target volume (ATV) was created from postoperative MRI scan contours drawn independently by five radiation oncologists in 40 patients. The MRI was fused with the postoperative CT for dosimetry purposes. The TM, defined as the radial distance between the ATV and the 100% isodose line, was measured at 16 points at the base, midgland, and apex. The ATV was divided into four quadrants: anterior-superior, posterior-superior, anterior-inferior, and posterior-inferior quadrants. The values of the dose that covers 90% of the ATV (D90) and the percentage of the ATV receiving the prescribed dose (V100) received by the whole prostate and its four quadrants were documented.
  
  
  RESULTS
  The range of the mean TM, in millimeter, was -8.88 to 3.68, 1.12 to 10.42, and 6.27 to 18.25 at the base, midgland, and apex, respectively. The mean D90 was 135.8, 162.8, 191.0, and 194.6 Gy for the anterior-superior, posterior-superior, anterior-inferior, and posterior-inferior quadrants, respectively.
  
  
  CONCLUSIONS
  Despite having a relatively uniform preoperative planning target volume, this study identified variable TMs postoperatively in different regions of the prostate. In particular, the anterior base is most underdosed, whereas the lateral regions of the midgland and apex have generous TMs. Postimplant dosimetric parameters were lowest in the anterior-inferior quadrant.
authors.affiliation: Department of Oncology, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Noha
authors.initials: N
authors.lastname: Jastaniyah
authors.forename: Ron
authors.initials: R
authors.lastname: Sloboda
authors.forename: Wafa
authors.initials: W
authors.lastname: Kamal
authors.forename: Harrison
authors.initials: H
authors.lastname: Moore
authors.forename: Sunita
authors.initials: S
authors.lastname: Ghosh
authors.forename: Nadeem
authors.initials: N
authors.lastname: Pervez
authors.forename: John
authors.initials: J
authors.lastname: Pedersen
authors.forename: Don
authors.initials: D
authors.lastname: Yee
authors.forename: Brita
authors.initials: B
authors.lastname: Danielson
authors.forename: Albert
authors.initials: A
authors.lastname: Murtha
authors.forename: John
authors.initials: J
authors.lastname: Amanie
authors.forename: Nawaid
authors.initials: N
authors.lastname: Usmani
mesh_terms: D000368:Aged; D001706:Biopsy; D001918:Brachytherapy / Q000379:methods*; D005500:Follow-Up Studies; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging / Q000379:methods*; D011467:Prostate / Q000000981:diagnostic imaging / Q000473:pathology; D011471:Prostatic Neoplasms / Q000175:diagnosis / Q000532:radiotherapy*; D011874:Radiometry; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D014057:Tomography, X-Ray Computed
keywords: Postimplant dosimetry; Prostate brachytherapy; Treatment margin