title: The use of mixed-integer programming for inverse treatment planning with pre-defined field segments.
abstract: Complex intensity patterns generated by traditional beamlet-based inverse treatment plans are often very difficult to deliver. In the approach presented in this work the intensity maps are controlled by pre-defining field segments to be used for dose optimization. A set of simple rules was used to define a pool of allowable delivery segments and the mixed-integer programming (MIP) method was used to optimize segment weights. The optimization problem was formulated by combining real variables describing segment, weights with a set of binary variables, used to enumerate voxels in targets and critical structures. The MIP method was compared to the previously used Cimmino projection algorithm. The field segmentation approach was compared to an inverse planning system with a traditional beamlet-based beam intensity optimization. In four complex cases of oropharyngeal cancer the segmental inverse planning produced treatment plans, which competed with traditional beamlet-based IMRT plans. The mixed-integer programming provided mechanism for imposition of dose-volume constraints and allowed for identification of the optimal solution for feasible problems. Additional advantages of the segmental technique presented here are: simplified dosimetry, quality assurance and treatment delivery.
authors.affiliation: Department of Radiation Oncology, Kimmel Cancer Center of the Jefferson Medical College, Thomas Jefferson University, Philadelphia, PA 19107, USA. Greg.Bednarz@mail.tju.edu
authors.forename: Greg
authors.initials: G
authors.lastname: Bednarz
authors.forename: Darek
authors.initials: D
authors.lastname: Michalski
authors.forename: Chris
authors.initials: C
authors.lastname: Houser
authors.forename: M Saiful
authors.initials: MS
authors.lastname: Huq
authors.forename: Ying
authors.initials: Y
authors.lastname: Xiao
authors.forename: Pramila Rani
authors.initials: PR
authors.lastname: Anne
authors.forename: James M
authors.initials: JM
authors.lastname: Galvin
mesh_terms: D000465:Algorithms; D003198:Computer Simulation; D004307:Dose-Response Relationship, Radiation; D006801:Humans; D021621:Imaging, Three-Dimensional; D009959:Oropharyngeal Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D011786:Quality Control; D011859:Radiography; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D020266:Radiotherapy, Conformal; D012680:Sensitivity and Specificity