title: Target volume uncertainty and a method to visualize its effect on the target dose prescription.
abstract: OBJECTIVE
  To consider the uncertainty in the construction of target boundaries for optimization, and to demonstrate how the principles of mathematical programming can be applied to determine and display the effect on the tumor dose of making small changes to the target boundary.
  
  
  METHODS
  The effect on the achievable target dose of making successive small shifts to the target boundary within its range of uncertainty was found by constructing a mixed-integer linear program that automated the placement of the beam angles using the initial target volume.
  
  
  RESULTS
  The method was demonstrated using contours taken from a nasopharynx case, with dose limits placed on surrounding structures. In the illustrated case, enlarging the target anteriorly to provide greater assurance of disease coverage did not force a sacrifice in the minimum or mean tumor doses. However, enlarging the margin posteriorly, near a critical structure, dramatically changed the minimum, mean, and maximum tumor doses.
  
  
  CONCLUSIONS
  Tradeoffs between the position of the target boundary and the minimum target dose can be developed using mixed-integer programming, and the results projected as a guide to contouring and plan selection.
authors.affiliation: Radiation Oncology, Indiana University, Indianapolis, IN 46202, USA.
authors.forename: Traci
authors.initials: T
authors.lastname: McCormick
authors.forename: Delal
authors.initials: D
authors.lastname: Dink
authors.forename: Seza
authors.initials: S
authors.lastname: Orcun
authors.forename: Joseph
authors.initials: J
authors.lastname: Pekny
authors.forename: Ron
authors.initials: R
authors.lastname: Rardin
authors.forename: Larry
authors.initials: L
authors.lastname: Baxter
authors.forename: Van
authors.initials: V
authors.lastname: Thai
authors.forename: Mark
authors.initials: M
authors.lastname: Langer
mesh_terms: D006801:Humans; D008962:Models, Theoretical; D009303:Nasopharyngeal Neoplasms / Q000532:radiotherapy*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D020266:Radiotherapy, Conformal / Q000379:methods*; D012680:Sensitivity and Specificity; D035501:Uncertainty