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A new sigmoidal function describing the small field dose profile data from a linear accelerator
Author(s) -
Lam Chan F.
Publication year - 1995
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.597554
Subject(s) - collimator , sigmoid function , interpolation (computer graphics) , dosimetry , linear particle accelerator , radiosurgery , function (biology) , mathematics , beam (structure) , optics , physics , mathematical analysis , geometry , nuclear medicine , radiation therapy , classical mechanics , computer science , motion (physics) , medicine , machine learning , evolutionary biology , artificial neural network , biology
Dose profile data from small circular fields have been used in treatment dose planning for stereotactic radiosurgery. Generally, a two‐dimensional interpolation of the measured beam profiles from circular collimators is used to calculate the dose at any axial depth and radial distance from the central axis. Instead, the dose profile data can be transformed into a sigmoidal form. A new three parameter sigmoidal function was developed to fit the transformed (sigmoidal) dose profile data. The values of the three estimated parameters were found to follow either linearly or exponentially as a function of axial depth. Thus, instead of linear interpolation, these formulas can be used to calculate dose at any axial depth and radial distance from the central axis for circular collimators of various diameters. This new sigmoidal function provides another formula to describe dose profile data from circular collimator of small fields.