title: An algorithm for fast beam angle selection in intensity modulated radiotherapy.
abstract: OBJECTIVE
  This article aims to introduce a novel algorithm for fast beam angle selection in intensity modulated radiotherapy (IMRT).
  
  
  METHODS
  The algorithm models the optimization problem as a beam angle ranking problem and chooses suitable beam angles according to their rank. A new parameter called "beam intensity profile perturbation score (BIPPS)" is used for ranking the beam angles. The BIPPS-based beam angle ranking implicitly accounts for the dose-volume effects of the involved structures. A simulated phantom case with obvious optimal beam angles is used to verify the validity of the presented technique. In addition, the efficiency of the algorithm was examined in three clinical cases (prostate, pancreas, and head and neck) in terms of DVH and dose distribution. In all cases, the judgment of the algorithm's efficiency was based on the comparison between plans with equidistant beams (equal-angle-plan) and plans with beams obtained using the algorithm (suitable-angle-plan).
  
  
  RESULTS
  It is observed from the study that the beam angle ranking function over BIPPS instantly picks up a suitable set of beam angles for a specific case. It takes only about 15 min for choosing the suitable beam angles even for the most complicated cases. The DVHs and dose distributions confirm that the proposed algorithm can efficiently reduce the mean or maximum dose to OARs, while guaranteeing the target coverage and dose uniformity. On the average, about 17% reduction in the mean dose to critical organs, such as rectum, bladder, kidneys and parotids, is observed. Also, about 12% (averaged) reduction in the maximum dose to critical organs (spinal cord) is observed in the clinical cases presented in this study.
  
  
  CONCLUSIONS
  This study demonstrates that the algorithm can be effectively applied to IMRT scenarios to get fast and case specific beam angle configurations.
authors.affiliation: Healthcare Sector, Siemens Ltd., 403A, Senapati Bapat Road, Pune-411016, Maharashtra, India. vaithe1985@gmail.com
authors.forename: R
authors.initials: R
authors.lastname: Vaitheeswaran
authors.forename: V K Sathiya
authors.initials: VK
authors.lastname: Narayanan
authors.forename: Janhavi R
authors.initials: JR
authors.lastname: Bhangle
authors.forename: Amit
authors.initials: A
authors.lastname: Nirhali
authors.forename: Namitha
authors.initials: N
authors.lastname: Kumar
authors.forename: Sumit
authors.initials: S
authors.lastname: Basu
authors.forename: Vikram
authors.initials: V
authors.lastname: Maiya
mesh_terms: D000465:Algorithms; D006801:Humans; D008297:Male; D009369:Neoplasms / Q000532:radiotherapy; D019047:Phantoms, Imaging; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D013997:Time Factors