title: A phantom for beam positioning and visualization.
abstract: OBJECTIVE
  A system was developed which uses the light field on the simulator to allow easy visualization of the treatment field in the sagittal plane of a phantom for complex treatment geometries.
  
  
  METHODS
  The phantom consists of a plastic shell with a vertical metallic plate in the sagittal plane. Magnetic strips attach to the plate to mark the lateral field while the anterior field is marked by a special pointer.
  
  
  CONCLUSIONS
  This method is useful for teaching and technique development by showing how the field is distorted after gantry, collimator, and couch rotations, as well as any overlap or gap in field matching for certain treatment techniques. It could be modified for actual patient setup.
authors.affiliation: Department of Medical Physics, Toronto-Bayview Regional Cancer Center, Ontario, Canada.
authors.forename: M K
authors.initials: MK
authors.lastname: Woo
authors.forename: S
authors.initials: S
authors.lastname: Wong
mesh_terms: D006801:Humans; D008961:Models, Structural; D009369:Neoplasms / Q000532:radiotherapy*; D011878:Radiotherapy / Q000295:instrumentation / Q000379:methods; D013679:Technology, Radiologic