title: Inverse planning--a comparative intersystem and interpatient constraint study.
abstract: OBJECTIVE
  To compare commercial treatment-planning systems (TPS) for inverse planning (IP) and to assess constraint variations for specific IMRT indications.
  
  
  METHODS
  For IP, OTP, XiO and BrainSCAN were used and step-and-shoot intensity-modulated radiotherapy (IMRT) delivery was assumed. Based on identical constraints, IP was performed for a prostate, head and neck, brain, and gynecologic case. IMRT plans were compared in terms of conformity/homogeneity, dose-volume histograms (DVHs), and delivery efficiency. For ten patients each of a class of indications, constraint variations were evaluated.
  
  
  RESULTS
  IMRT plans were comparable concerning minimum target dose, homogeneity, conformity, and maximum doses to organs at risk. Larger differences were seen in dose gradients outside the target, monitor units, and segment number. Using help structures proved efficient to shape isodoses and to reduce segmentation workload. For IMRT class solutions, IP constraint variations depended on anatomic site.
  
  
  CONCLUSIONS
  IP systems requiring doses as input and having objective functions based on physical parameters had a very similar performance. Constraint templates can be established for a class of IMRT indications.
authors.affiliation: Department of Radiotherapy and Radiobiology, AKH Vienna, Medical University of Vienna, Vienna, Austria. Dietmar.Georg@akhwien.at
authors.forename: Dietmar
authors.initials: D
authors.lastname: Georg
authors.forename: Bernhard
authors.initials: B
authors.lastname: Kroupa
authors.forename: Petra
authors.initials: P
authors.lastname: Georg
authors.forename: Peter
authors.initials: P
authors.lastname: Winkler
authors.forename: Joachim
authors.initials: J
authors.lastname: Bogner
authors.forename: Karin
authors.initials: K
authors.lastname: Dieckmann
authors.forename: Richard
authors.initials: R
authors.lastname: Pötter
mesh_terms: D001932:Brain Neoplasms / Q000532:radiotherapy*; D005260:Female; D005918:Glomus Tumor / Q000532:radiotherapy*; D006801:Humans; D008297:Male; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000295:instrumentation / Q000379:methods; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D014067:Tonsillar Neoplasms / Q000532:radiotherapy*; D002583:Uterine Cervical Neoplasms / Q000532:radiotherapy*