title: Geometrical pre-planning for conformal radiotherapy.
abstract: The optimum selection of beams and arcs in conformal techniques is of the outmost importance in modern radiotherapy. In this work we give a description of an analytic method to aid optimum selection, which is based on minimizing the intersection between beams and organs at risk (OAR) and on minimizing the intersection between the beam and the planning target volume (PTV). An arc-selection function that permits selection of irradiation arcs based on individual beam feasibility is introduce. The method simulates the treatment process by defining a computed beam feasibility, for every possible set of gantry-table angles, by taking into account accurately computer intersection volumes between the OAR and beams. The beams are shaped to conform the target using realistic parameters for the treatment process. The results are displayed on a virtual sphere centred at the isocenter with color-coded regions indicating beam feasibility. Arcs selections are performed by searching the map for successive gantry positions at a certain table angle, with feasibility values greater than a user-specified threshold. The accuracy of the method was confirmed by using geometrical regular shapes, as well as real clinical cases.
authors.affiliation: Medical Physics Department, Medical School, University Hospital, University of Thessaly, Greece. jtsoug@med.uth.gr
authors.forename: Ioannis
authors.initials: I
authors.lastname: Tsougos
authors.forename: Eduard
authors.initials: E
authors.lastname: Schreibmann
authors.forename: Michael
authors.initials: M
authors.lastname: Lahanas
authors.forename: Kiki
authors.initials: K
authors.lastname: Theodorou
authors.forename: Constantin
authors.initials: C
authors.lastname: Kappas
authors.forename: Dimos
authors.initials: D
authors.lastname: Baltas
mesh_terms: D001932:Brain Neoplasms / Q000532:radiotherapy; D006801:Humans; D019047:Phantoms, Imaging; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D020266:Radiotherapy, Conformal / Q000592:standards*; D012004:Rectal Neoplasms / Q000532:radiotherapy; D015203:Reproducibility of Results; D001749:Urinary Bladder Neoplasms / Q000532:radiotherapy