title: Patient-specific 3D pretreatment and potential 3D online dose verification of Monte Carlo-calculated IMRT prostate treatment plans.
abstract: OBJECTIVE
  Fast and reliable comprehensive quality assurance tools are required to validate the safety and accuracy of complex intensity-modulated radiotherapy (IMRT) plans for prostate treatment. In this study, we evaluated the performance of the COMPASS system for both off-line and potential online procedures for the verification of IMRT treatment plans.
  
  
  METHODS
  COMPASS has a dedicated beam model and dose engine, it can reconstruct three-dimensional dose distributions on the patient anatomy based on measured fluences using either the MatriXX two-dimensional (2D) array (offline) or a 2D transmission detector (T2D) (online). For benchmarking the COMPASS dose calculation, various dose-volume indices were compared against Monte Carlo-calculated dose distributions for five prostate patient treatment plans. Gamma index evaluation and absolute point dose measurements were also performed in an inhomogeneous pelvis phantom using extended dose range films and ion chamber for five additional treatment plans.
  
  
  RESULTS
  MatriXX-based dose reconstruction showed excellent agreement with the ion chamber (<0.5%, except for one treatment plan, which showed 1.5%), film (∼100% pixels passing gamma criteria 3%/3 mm) and mean dose-volume indices (<2%). The T2D based dose reconstruction showed good agreement as well with ion chamber (<2%), film (∼99% pixels passing gamma criteria 3%/3 mm), and mean dose-volume indices (<5.5%).
  
  
  CONCLUSIONS
  The COMPASS system qualifies for routine prostate IMRT pretreatment verification with the MatriXX detector and has the potential for on-line verification of treatment delivery using T2D.
authors.affiliation: Department of Radiation Oncology, University Medical Centre Mannheim, University of Heidelberg, Mannheim, Germany. ramesh.boggula@umm.de
authors.forename: Ramesh
authors.initials: R
authors.lastname: Boggula
authors.forename: Lennart
authors.initials: L
authors.lastname: Jahnke
authors.forename: Hansjoerg
authors.initials: H
authors.lastname: Wertz
authors.forename: Frank
authors.initials: F
authors.lastname: Lohr
authors.forename: Frederik
authors.initials: F
authors.lastname: Wenz
mesh_terms: D000465:Algorithms; D019985:Benchmarking / Q000592:standards*; D006801:Humans; D008297:Male; D009010:Monte Carlo Method; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000295:instrumentation / Q000379:methods / Q000592:standards*; D050397:Radiotherapy, Intensity-Modulated / Q000295:instrumentation / Q000379:methods / Q000592:standards*