title: Prostate brachytherapy with oblique needles to treat large glands and overcome pubic arch interference.
abstract: OBJECTIVE
  First, to show that low-dose-rate prostate brachytherapy plans using oblique needle trajectories are more successful than parallel trajectories for large prostates with pubic arch interference (PAI); second, to test the accuracy of delivering an oblique plan by using a three-dimensional (3D) transrectal ultrasonography (TRUS)-guided mechatronic system.
  
  
  METHODS
  Prostates were contoured for 5 subjects' 3D TRUS images showing a maximum PAI of ≤1 cm and a prostate volume of <50 cc. Two planning studies were done. First, prostate contours were artificially enlarged to 45 to 80 cc in 5- to 10-cc increments for a single subject. Second, all subject prostate contours were enlarged to 60 cc. For each study, three types of plans were manually created for comparison: a parallel needle template (PT) plan, a parallel needle no-template (PNT) plan, and an oblique needle no-template (OBL) plan. Needle positions and angles were not discretized for nontemplate plans. European Society for Therapeutic Radiology and Oncology dose-volume histogram guidelines, iodine-125 (145-Gy prescription, 0.43 U), and needle angles of <15° were used. An OBL plan was delivered to a pubic arch containing a 60-cc prostate phantom that mimicked the anatomy of the subject with the greatest PAI (23% by volume).
  
  
  RESULTS
  In the increasing-prostate volume study, OBL plans were successful for prostates of ≤80 cc, and PT plans were successful for prostates of <65 cc. In paired, one-sided t tests for the 60-cc volume study, OBL plans showed dosimetric improvements for all organs compared to both of the parallel type plans (p < 0.05); PNT plans showed a benefit only in planning target volumes receiving more than 100 Gy compared to PT plans. A computed tomography scan of the phantom showed submillimeter seed placement accuracy in all directions.
  
  
  CONCLUSIONS
  OBL plans were significantly better than parallel plans, and an OBL plan was accurately delivered to a 60-cc prostate phantom with 23% PAI by volume.
authors.affiliation: Department of Physics and Astronomy, University of Western Ontario, London, Ontario, Canada.
authors.forename: Bon
authors.initials: B
authors.lastname: Ryu
authors.forename: Jeff
authors.initials: J
authors.lastname: Bax
authors.forename: Chandima
authors.initials: C
authors.lastname: Edirisinge
authors.forename: Craig
authors.initials: C
authors.lastname: Lewis
authors.forename: Jeff
authors.initials: J
authors.lastname: Chen
authors.forename: David
authors.initials: D
authors.lastname: D'Souza
authors.forename: Aaron
authors.initials: A
authors.lastname: Fenster
authors.forename: Eugene
authors.initials: E
authors.lastname: Wong
mesh_terms: D001918:Brachytherapy / Q000295:instrumentation / Q000379:methods*; D005240:Feasibility Studies; D006801:Humans; D008297:Male; D009339:Needles; D019047:Phantoms, Imaging; D011467:Prostate / Q000000981:diagnostic imaging; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D011630:Pubic Bone / Q000000981:diagnostic imaging; D061089:Radiotherapy, Image-Guided / Q000379:methods*; D012007:Rectum / Q000000981:diagnostic imaging; D012371:Robotics; D018084:Ultrasonography, Interventional / Q000379:methods; D014521:Urethra / Q000000981:diagnostic imaging