title: Sector analysis of dosimetry of prostate cancer patients treated with low-dose-rate brachytherapy.
abstract: OBJECTIVE
  Brachytherapy is an effective single treatment modality for low- and intermediate-risk prostate cancer. Here, we compare the radiation doses in different prostate sectors between the preimplant planning images and the postimplant dosimetry.
  
  
  METHODS
  Two hundred fifteen consecutive patients treated for prostate cancer by (125)I seed brachytherapy were assessed. Pretreatment plans using transrectal ultrasound images of the prostate were compared with the dose calculated on posttreatment MRI and CT scans obtained 1 month after seed implantation. Twelve sectors were generated by dividing the prostate base, midgland, and apex into four quadrants each. Pretreatment and posttreatment dosimetry were compared between the 12 different sectors of the prostate.
  
  
  RESULTS
  Average V100 (percentage of prostate volume that receives 100% of the prescribed dose) in the preimplant planning images of the prostate was 99.9 ± 0.25% compared with postimplant V100 of 94.8 ± 3.77% (p < 0.0001). Prostate V100 in the postimplant dosimetry was >91% in all sectors, except the anterior base sector, in which it was 64.87 ± 20.96%. Average 1-month D90 (the dose to 90% of the prostate volume) was 114.5 ± 10.55%. D90 at 1 month compared with preimplant planning was lower in the prostate base and higher in the prostate apex (p < 0.001).
  
  
  CONCLUSIONS
  Our results show that in (125)I seed brachytherapy, prostate base receives a lower dose and apex receives a higher dose compared with preimplant planned dose coverage.
authors.affiliation: Department of Radiation Oncology, Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, Ontario, Canada; Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Nicola J
authors.initials: NJ
authors.lastname: Nasser
authors.affiliation: Department of Radiation Physics, Princess Margaret Cancer Centre, Toronto, Ontario, Canada.
authors.forename: Yinkun
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Radiation Physics, Princess Margaret Cancer Centre, Toronto, Ontario, Canada.
authors.forename: Jette
authors.initials: J
authors.lastname: Borg
authors.affiliation: Department of Radiation Oncology, Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, Ontario, Canada; Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada. Electronic address: saibish.elantholi@rmp.uhn.on.ca.
authors.forename: Elantholi P
authors.initials: EP
authors.lastname: Saibishkumar
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001918:Brachytherapy / Q000379:methods*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D011467:Prostate / Q000000981:diagnostic imaging; D011471:Prostatic Neoplasms / Q000175:diagnosis / Q000532:radiotherapy*; D011874:Radiometry; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed; D014463:Ultrasonography; D055815:Young Adult
keywords: Cancer; Dosimetry; Prostate; Sector analysis