title: Beam orientation selection for intensity-modulated radiation therapy based on target equivalent uniform dose maximization.
abstract: OBJECTIVE
  To develop an automated beam-orientation selection procedure for intensity-modulated radiotherapy (IMRT), and to determine if a small number of beams picked by this automated procedure can yield results comparable to a large number of manually placed orientations.
  
  
  METHODS
  The automated beam selection procedure maximizes an unconstrained objective function composed of target equivalent uniform dose (EUD) and critical structure dose-volume histogram (DVH) constraints. Beam orientations are selected from a large feasible set of directions through a series of alternating fluence optimization and orientation alteration steps, until convergence to a stable orientation set. The fluence optimization step adjusts fluences to maximize the objective function. The orientation alteration step substitutes beams in the orientation set currently under consideration with beams of the parent set in the immediate angular vicinity; the altered orientation set is deemed current if it produces a higher objective function value in the fluence optimization step.
  
  
  CONCLUSIONS
  It is demonstrated, for prostate IMRT planning, that a modest number of appropriately selected beam orientations (3 or 5) can provide dose distributions as satisfactory as those produced by a large number of unselected equispaced orientations. Such selected beam orientations can reduce overall treatment time, thus making IMRT more clinically practical.
authors.affiliation: Department of Radiation Oncology, Duke University Medical Center, Durham, NC 27710, USA. shiva@radonc.duke.edu
authors.forename: Shiva
authors.initials: S
authors.lastname: Das
authors.forename: Timothy
authors.initials: T
authors.lastname: Cullip
authors.forename: Gregg
authors.initials: G
authors.lastname: Tracton
authors.forename: Sha
authors.initials: S
authors.lastname: Chang
authors.forename: Lawrence
authors.initials: L
authors.lastname: Marks
authors.forename: Mitchell
authors.initials: M
authors.lastname: Anscher
authors.forename: Julian
authors.initials: J
authors.lastname: Rosenman
mesh_terms: D000465:Algorithms; D005270:Femur Head / Q000528:radiation effects; D006801:Humans; D008297:Male; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D011879:Radiotherapy Dosage; D020266:Radiotherapy, Conformal / Q000379:methods*