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Parallel‐plate ionization chamber response in cobalt‐60 irradiated transition zones
Author(s) -
Kooy Hanne M.,
Simpson Larry D.,
McFaul James A.
Publication year - 1988
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 - 10.1118/1.596251
Subject(s) - ionization chamber , monte carlo method , slab , materials science , polystyrene , imaging phantom , irradiation , dosimetry , ionization , cobalt 60 , absorbed dose , optics , percentage depth dose curve , electron , atomic physics , computational physics , nuclear medicine , physics , nuclear physics , ion , composite material , medicine , mathematics , statistics , quantum mechanics , geophysics , polymer
The authors study the acceptance of a Capintec parallel‐plate ionization chamber. The Capintec chamber is used for dose measurements in a lead and polystyrene slab phantom irradiated with cobalt‐60 γ rays. The authors define an enhancement ratio to quantify the dose measurements. The enhancement ratio equals the ratio of dose measured with the lead slab present to dose measured under equilibrium conditions in polystyrene at equal primary beam attenuation. The measured enhancement ratio at the exit side of the lead/polystyrene interface is 25% lower than the Monte Carlo predicted enhancement ratio. The authors propose that geometric acceptance limitations of the Capintec chamber to large‐angle, low‐energy electrons are the cause for this difference. A Monte Carlo simulation of the Capintec chamber acceptance confirms the hypothesis.