title: Analysis of tissue-maximum ratio/scatter-maximum ratio model relative to the prediction of tissue-maximum ratio in asymmetrically collimated fields.
abstract: The tissue-maximum ratio/scatter-maximum ratio model has been examined as an empirical model capable of predicting the variation in tissue-maximum ratio observed in fields shifted off-axis by independent collimators. This model has been assessed for its sensitivity to the necessary extrapolation of percentage depth dose data and phantom-scatter factors to zero field size and to large field sizes. This model was found to yield good results for both 6- and 24-MV x rays and to be relatively insensitive to the assumptions made regarding unmeasurable beam parameters.
authors.affiliation: Radiation Therapy, Marshfield Clinic, Wisconsin 54449.
authors.forename: D D
authors.initials: DD
authors.lastname: Loshek
mesh_terms: D055592:Biophysical Phenomena; D001703:Biophysics; D006801:Humans; D008962:Models, Theoretical; D011879:Radiotherapy Dosage; D012542:Scattering, Radiation