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Use of low‐pressure tissue equivalent proportional counters for the dosimetry of neutron beams used in BNCT and BNCEFNT
Author(s) -
Kota Chandrasekhar,
Maughan Richard L.,
Tattam David,
Bey T. Derek
Publication year - 2000
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 - 10.1118/1.598921
Subject(s) - dosimetry , neutron , neutron capture , monte carlo method , neutron radiation , equivalent dose , absorbed dose , materials science , beam (structure) , ionization chamber , imaging phantom , percentage depth dose curve , neutron source , neutron temperature , radiation , nuclear physics , nuclear medicine , radiochemistry , physics , ion , optics , chemistry , medicine , mathematics , statistics , quantum mechanics , ionization
The absorbed dose in a phantom or patient in boron neutron capture therapy (BNCT) and boron neutron capture enhanced fast neutron therapy (BNCEFNT) is deposited by gamma rays, neutrons of a range of energies and the10 B reaction products. These dose components are commonly measured with paired (TE/Mg) ion chambers and foil activation technique. In the present work, we have investigated the use of paired tissue equivalent (TE) andTE + 10 B proportional counters as an alternate and complementary dosimetry technique for use in these neutron beams. We first describe various aspects of counter operation, uncertainties in dose measurement, and interpretation of the data. We then present measurements made in the following radiation fields: An epithermal beam at the University of Birmingham in the United Kingdom, a d ( 48.5 ) + Be fast neutron therapy beam at Harper Hospital in Detroit, and a252 Cf radiation field. In the epithermal beam, our measured gamma and neutron dose rates compare very well with the values calculated using Monte Carlo methods. The measured10 B dose rates show a systematic difference of ∼35% when compared to the calculations. The measured neutron + gamma dose rates in the fast neutron beam are in good agreement with those measured using a calibrated A‐150 TEP (tissue equivalent plastic) ion chamber. The measured10 B dose rates compare very well with those measured using other methods. In the252 Cf radiation field, the measured dose rates for all three components agree well with other Monte Carlo calculations and measurements. Based on these results, we conclude that the paired low‐pressure proportional counters can be used to establish an independent technique of dose measurement in these radiation fields.