title: Implementation of a dose gradient method into optimization of dose distribution in prostate cancer 3D-CRT plans.
abstract: OBJECTIVE
  The aim of this work is to present a method of beam weight and wedge angle optimization for patients with prostate cancer.
  
  
  BACKGROUND
  3D-CRT is usually realized with forward planning based on a trial and error method. Several authors have published a few methods of beam weight optimization applicable to the 3D-CRT. Still, none on these methods is in common use.
  
  
  METHODS
  Optimization is based on the assumption that the best plan is achieved if dose gradient at ICRU point is equal to zero. Our optimization algorithm requires beam quality index, depth of maximum dose, profiles of wedged fields and maximum dose to femoral heads. The method was tested for 10 patients with prostate cancer, treated with the 3-field technique. Optimized plans were compared with plans prepared by 12 experienced planners. Dose standard deviation in target volume, and minimum and maximum doses were analyzed.
  
  
  RESULTS
  The quality of plans obtained with the proposed optimization algorithms was comparable to that prepared by experienced planners. Mean difference in target dose standard deviation was 0.1% in favor of the plans prepared by planners for optimization of beam weights and wedge angles. Introducing a correction factor for patient body outline for dose gradient at ICRU point improved dose distribution homogeneity. On average, a 0.1% lower standard deviation was achieved with the optimization algorithm. No significant difference in mean dose-volume histogram for the rectum was observed.
  
  
  CONCLUSIONS
  Optimization shortens very much time planning. The average planning time was 5 min and less than a minute for forward and computer optimization, respectively.
authors.affiliation: Department of Medical Physics, Maria Sklodowska-Curie Memorial Cancer Centre and Institute of Oncology, Warsaw, Poland ; Biomedical Physics Division, Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Poland.
authors.forename: Marta K
authors.initials: MK
authors.lastname: Giżyńska
authors.affiliation: Department of Medical Physics, Maria Sklodowska-Curie Memorial Cancer Centre and Institute of Oncology, Warsaw, Poland.
authors.forename: Paweł F
authors.initials: PF
authors.lastname: Kukołowicz
authors.affiliation: Biomedical Physics Division, Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Poland.
authors.forename: Paweł
authors.initials: P
authors.lastname: Kordowski
keywords: 3D-CRT; Beam weights; Prostate; Wedges