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Characterization of gypsum attenuators for radiotherapy dose modification
Author(s) -
Arora V. R.,
Weeks K. J.
Publication year - 1994
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 - 10.1118/1.597364
Subject(s) - attenuation , attenuation coefficient , beam (structure) , optics , materials science , dosimetry , percentage depth dose curve , nuclear medicine , physics , ionization chamber , medicine , ion , quantum mechanics , ionization
Gypsum has significant value as a compensator material for use with high energy x rays in radiation therapy. Compensator thickness may be calculated by using an effective attenuation coefficient (μ eff ). Detailed measurements using narrow and broad beam geometry were collected to determine this effective attenuation coefficient as a function of energy (4–15 MV), field size, depth in tissue, and thickness of the compensator. An effective attenuation coefficient relation was defined using a least‐square method. It was then determined that extrapolating the broad beam data to a 0×0 cm 2 field size resulted in a good approximation to the measured narrow beam attenuation coefficient. The variations in surface dose produced by gypsum attenuators were compared to open beam results. For the energies studied, it was determined that the increase in surface dose was acceptable for clinical application.