Relative output factors of asymmetric megavoltage beams.
A new method for calculating output factors of asymmetric therapy fields is presented. The method uses the output factors of symmetric fields, as well as off-axis ratios measured in air, to calculate the output factor for an arbitrary asymmetric field. Calculations have been checked by measurements in four photon beams (4-18 MV) of three different linear accelerators. The accuracy between the theory and the measurements is generally better than 1%. According to the preliminary results the method may also be suitable for megavoltage electron beams.
Tenhunen
M
M
Department of Radiotherapy and Oncology, Kuopio University Hospital, Finland.
Lahtinen
T
T
D000465:Algorithms; D004583:Electrons; D006801:Humans; D008954:Models, Biological; D010315:Particle Accelerators; D017785:Photons; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D011882:Radiotherapy, High-Energy / Q000295:instrumentation / Q000379:methods*; D012542:Scattering, Radiation