title: A generic off-axis energy correction for linac photon beam dosimetry.
abstract: Cooperative clinical trial group protocols frequently require off-axis point dose calculations. The Radiological Physics Center uses the calculative technique developed by Hanson et al. [Med. Phys. 7, 145-146 (1980); 7, 147-150 (1980)] to verify these calculations. In order to correct for off-axis energy changes, this technique requires off-axis half-value layer data, HVL, as a function of off-axis ray angle for the specific beam. This paper presents a formulism based on HVL mesurements on a limited number of therapy beams, which allows the calculation of an off-axis energy-correction factor for any clinical photon beam created by a linear accelerator using conventional flattening filters.
authors.affiliation: Department of Radiation Physics, University of Texas, M. D. Anderson Cancer Center, Houston 77030, USA.
authors.forename: R C
authors.initials: RC
authors.lastname: Tailor
authors.forename: V M
authors.initials: VM
authors.lastname: Tello
authors.forename: C B
authors.initials: CB
authors.lastname: Schroy
authors.forename: M
authors.initials: M
authors.lastname: Vossler
authors.forename: W F
authors.initials: WF
authors.lastname: Hanson
mesh_terms: D002985:Clinical Protocols; D004867:Equipment Design; D006801:Humans; D010315:Particle Accelerators; D019047:Phantoms, Imaging; D017785:Photons; D011137:Polystyrenes; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted
chemical_list: D011137:Polystyrenes; C024075:styrofoam