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Poster — Thur Eve — 67: Variations in Ion Chamber Response for Low‐ and Medium‐Energy X‐Rays
Author(s) -
Shen H
Publication year - 2010
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 - 10.1118/1.3476172
Subject(s) - ionization chamber , calibration , range (aeronautics) , physics , monte carlo method , ionizing radiation , energy (signal processing) , radiation , ionization , ion , calibration curve , atomic physics , computational physics , sensitivity (control systems) , optics , nuclear physics , irradiation , materials science , statistics , mathematics , quantum mechanics , detection limit , composite material , electronic engineering , engineering
The sensitivity of different models of ionization chambers used in radiation therapy varies substantially over the low‐ and medium‐energy x‐ray qualities in the effective energy (E eff ) range of 20 – 160 keV. Previous authors calculated some of these variations for 4 common models of ion chambers using EGSnrc Monte Carlo (MC) techniques 1 , but lacked sufficient experimental data to demonstrate the accuracy of their calculations. This work presents sets of measured calibration coefficients from a substantial number of each of 6 common models of ion chambers over this effective energy range. Measurements are based on calibrations performed with the primary standard beams at the X‐ray calibration laboratory of Ionizing Radiation Standards at NRC. This data demonstrates the degree that the response of commercially manufactured ion chambers varies between different models of chamber. In general, identical models follow the same shape of response curve over low‐ and medium‐energy x‐ray qualities in the E eff range of 20 – 160 keV. The general shape of the response curves for this energy range can be accurately modeled with EGSnrc.