title: Head-scatter factors in rectangular photon fields.
abstract: Head-scatter factors were measured for a range of field sizes of rectangular shape from a linear accelerator that provides 6 and 25 MV photon beams. For a given field length and width, exchange of the inner and outer collimator pairs produces differences in the head-scatter factor of up to about 2% and 3% in open and wedged fields, respectively. Dependence on elongation deviates by up to 2% from that given by the equivalent squares. Such effects can easily be taken into account by using head-scatter data that have been directly measured in rectangular fields or by applying empirical corrections to values for square or equivalent square fields.
authors.affiliation: Department of Radiation Oncology, Roger Williams Medical Center, Brown University, Providence, Rhode Island 02908.
authors.forename: M
authors.initials: M
authors.lastname: Tatcher
authors.forename: B E
authors.initials: BE
authors.lastname: Bjarngard
mesh_terms: D055592:Biophysical Phenomena; D001703:Biophysics; D006801:Humans; D008961:Models, Structural; D010315:Particle Accelerators; D011827:Radiation; D011879:Radiotherapy Dosage; D011882:Radiotherapy, High-Energy / Q000706:statistics & numerical data*; D012542:Scattering, Radiation