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Absolute neutron dosimetry: Effects of ionization chamber wall thickness
Author(s) -
Ten Haken Randall K.,
Awschalom Miguel,
Rosenberg Ivan
Publication year - 1985
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 - 10.1118/1.595734
Subject(s) - ionization chamber , dosimetry , imaging phantom , percentage depth dose curve , materials science , neutron , ionization , absorbed dose , beam (structure) , extrapolation , irradiation , attenuation , atomic physics , nuclear physics , optics , nuclear medicine , chemistry , physics , ion , medicine , mathematical analysis , mathematics , organic chemistry
To assess the effect of ionization chamber wall thickness on absolute neutron absorbed dose determinations, measurements were made of the charge collected by an A‐150 tissue‐equivalent plastic ionization chamber irradiated by a p (66)Be(49) neutron therapy beam as a function of chamber wall thickness both in air and in four different media: tissue‐equivalent solution, water, motor oil, and glycerin. Wall thicknesses ranged from 1 to 31 mm, where isolation of the chamber gas volume from protons originating outside the chamber wall was assured. The in‐air measurements compare favorably with earlier buildup measurements performed with an A‐150 extrapolation chamber in an A‐150 phantom. The in‐phantom results may be explained if the effect of charged particles reaching the gas volume from the medium and the wall as well as the differences in neutron attenuation by the wall and the medium displaced by the wall are taken into account. The errors in absolute absorbed dose determination caused by ignoring the above processes are assessed.