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Title: Sci-Sat AM: Radiation Dosimetry and Practical Therapy Solutions - 06: Investigation of an absorbed dose to water formalism for a miniature low-energy x-ray source

Abstract

Purpose: We present a formalism for calculating the absorbed dose to water from a miniature x-ray source (The INTRABEAM system, Carl Zeiss), using a parallel-plate ionization chamber calibrated in terms of air-kerma. Monte Carlo calculations were performed to derive a chamber conversion factor (C{sub Q}) from reference air-kerma to dose to water for the INTRABEAM. C{sub Q} was investigated as a function of depth in water, and compared with the manufacturer’s reported value. The effect of chamber air cavity dimension tolerance was also investigated. Methods: Air-kerma (A{sub k}) from a reference beam was calculated using the EGSnrc user code cavity. Using egs-chamber, a model of a PTW 34013 parallel-plate ionization chamber was created according to manufacturer specifications. The dose to the chamber air cavity (D{sub gas}) was simulated both in-air (with reference beam) and in-water (with INTRABEAM source). Dose to a small water voxel (D{sub w}) was also calculated. C{sub Q} was derived from these quantities. Results: C{sub Q} was found to vary by up to 15% (1.30 vs 1.11) between chamber dimension extremes. The agreement between chamber C{sub Q} was found to improve with increasing depth in water. However, in all cases investigated, C{sub Q} was larger than themore » manufacturer reported value of 1.054. Conclusions: Our results show that cavity dimension tolerance has a significant effect on C{sub Q}, with differences as large as 15%. In all cases considered, C{sub Q} was found to be larger than the reported value of 1.054. This suggests that the recommended calculation underestimates the dose to water.« less

Authors:
;  [1]
  1. McGill University,
Publication Date:
OSTI Identifier:
22689385
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 43; Journal Issue: 8; Other Information: (c) 2016 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
61 RADIATION PROTECTION AND DOSIMETRY; 60 APPLIED LIFE SCIENCES; ABSORBED RADIATION DOSES; CAVITIES; DOSIMETRY; IONIZATION CHAMBERS; MANUFACTURERS; MONTE CARLO METHOD; WATER; X RADIATION; X-RAY SOURCES

Citation Formats

Watson, Peter, and Seuntjens, Jan. Sci-Sat AM: Radiation Dosimetry and Practical Therapy Solutions - 06: Investigation of an absorbed dose to water formalism for a miniature low-energy x-ray source. United States: N. p., 2016. Web. doi:10.1118/1.4961860.
Watson, Peter, & Seuntjens, Jan. Sci-Sat AM: Radiation Dosimetry and Practical Therapy Solutions - 06: Investigation of an absorbed dose to water formalism for a miniature low-energy x-ray source. United States. doi:10.1118/1.4961860.
Watson, Peter, and Seuntjens, Jan. Mon . "Sci-Sat AM: Radiation Dosimetry and Practical Therapy Solutions - 06: Investigation of an absorbed dose to water formalism for a miniature low-energy x-ray source". United States. doi:10.1118/1.4961860.
@article{osti_22689385,
title = {Sci-Sat AM: Radiation Dosimetry and Practical Therapy Solutions - 06: Investigation of an absorbed dose to water formalism for a miniature low-energy x-ray source},
author = {Watson, Peter and Seuntjens, Jan},
abstractNote = {Purpose: We present a formalism for calculating the absorbed dose to water from a miniature x-ray source (The INTRABEAM system, Carl Zeiss), using a parallel-plate ionization chamber calibrated in terms of air-kerma. Monte Carlo calculations were performed to derive a chamber conversion factor (C{sub Q}) from reference air-kerma to dose to water for the INTRABEAM. C{sub Q} was investigated as a function of depth in water, and compared with the manufacturer’s reported value. The effect of chamber air cavity dimension tolerance was also investigated. Methods: Air-kerma (A{sub k}) from a reference beam was calculated using the EGSnrc user code cavity. Using egs-chamber, a model of a PTW 34013 parallel-plate ionization chamber was created according to manufacturer specifications. The dose to the chamber air cavity (D{sub gas}) was simulated both in-air (with reference beam) and in-water (with INTRABEAM source). Dose to a small water voxel (D{sub w}) was also calculated. C{sub Q} was derived from these quantities. Results: C{sub Q} was found to vary by up to 15% (1.30 vs 1.11) between chamber dimension extremes. The agreement between chamber C{sub Q} was found to improve with increasing depth in water. However, in all cases investigated, C{sub Q} was larger than the manufacturer reported value of 1.054. Conclusions: Our results show that cavity dimension tolerance has a significant effect on C{sub Q}, with differences as large as 15%. In all cases considered, C{sub Q} was found to be larger than the reported value of 1.054. This suggests that the recommended calculation underestimates the dose to water.},
doi = {10.1118/1.4961860},
journal = {Medical Physics},
number = 8,
volume = 43,
place = {United States},
year = {Mon Aug 15 00:00:00 EDT 2016},
month = {Mon Aug 15 00:00:00 EDT 2016}
}