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Title: Reference dosimetry at the Australian Synchrotron's imaging and medical beamline using free-air ionization chamber measurements and theoretical predictions of air kerma rate and half value layer

Abstract

Purpose: Novel, preclinical radiotherapy modalities are being developed at synchrotrons around the world, most notably stereotactic synchrotron radiation therapy and microbeam radiotherapy at the European Synchrotron Radiation Facility in Grenoble, France. The imaging and medical beamline (IMBL) at the Australian Synchrotron has recently become available for preclinical radiotherapy and imaging research with clinical trials, a distinct possibility in the coming years. The aim of this present study was to accurately characterize the synchrotron-generated x-ray beam for the purposes of air kerma-based absolute dosimetry. Methods: The authors used a theoretical model of the energy spectrum from the wiggler source and validated this model by comparing the transmission through copper absorbers (0.1-3.0 mm) against real measurements conducted at the beamline. The authors used a low energy free air ionization chamber (LEFAC) from the Australian Radiation Protection and Nuclear Safety Agency and a commercially available free air chamber (ADC-105) for the measurements. The dimensions of these two chambers are different from one another requiring careful consideration of correction factors. Results: Measured and calculated half value layer (HVL) and air kerma rates differed by less than 3% for the LEFAC when the ion chamber readings were corrected for electron energy loss and ion recombination.more » The agreement between measured and predicted air kerma rates was less satisfactory for the ADC-105 chamber, however. The LEFAC and ADC measurements produced a first half value layer of 0.405 {+-} 0.015 and 0.412 {+-} 0.016 mm Cu, respectively, compared to the theoretical prediction of 0.427 {+-} 0.012 mm Cu. The theoretical model based upon a spectrum calculator derived a mean beam energy of 61.4 keV with a first half value layer of approximately 30 mm in water. Conclusions: The authors showed in this study their ability to verify the predicted air kerma rate and x-ray attenuation curve on the IMBL using a simple experimental method, namely, HVL measurements. The HVL measurements strongly supports the x-ray beam spectrum, which in turn has a profound effect on x-ray dosimetry.« less

Authors:
;  [1];  [2];  [3];  [4];  [5];  [6];  [7]
  1. Department of Obstetrics and Gynaecology, University of Melbourne, The Royal Women's Hospital, Parkville, Victoria 3052 (Australia)
  2. CSIRO Materials Science and Engineering, Clayton, Victoria 3169 (Australia)
  3. Imaging and Medical Beamline, Australian Synchrotron, Clayton, Victoria 3168 (Australia)
  4. Australian Radiation Protection and Nuclear Safety Agency, Yallambie, Victoria 3085 (Australia)
  5. KTH Royal Institute of Technology, Stockholm SE-100 44 (Sweden)
  6. School of Physics, Monash University, Clayton, Victoria 3800 (Australia)
  7. Department of Medical Imaging and Radiation Sciences, Monash University, Clayton, Victoria 3800 (Australia)
Publication Date:
OSTI Identifier:
22121031
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 40; Journal Issue: 6; Other Information: (c) 2013 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; 62 RADIOLOGY AND NUCLEAR MEDICINE; CLINICAL TRIALS; ENERGY-LOSS SPECTROSCOPY; EUROPEAN SYNCHROTRON RADIATION FACILITY; IONIZATION CHAMBERS; RADIOTHERAPY; SYNCHROCYCLOTRONS; SYNCHROTRON RADIATION; SYNCHROTRONS; X RADIATION; X-RAY DOSIMETRY

Citation Formats

Crosbie, Jeffrey C., Rogers, Peter A. W., Stevenson, Andrew W., Hall, Christopher J., Lye, Jessica E., Nordstroem, Terese, Midgley, Stewart M., and Lewis, Robert A. Reference dosimetry at the Australian Synchrotron's imaging and medical beamline using free-air ionization chamber measurements and theoretical predictions of air kerma rate and half value layer. United States: N. p., 2013. Web. doi:10.1118/1.4803675.
Crosbie, Jeffrey C., Rogers, Peter A. W., Stevenson, Andrew W., Hall, Christopher J., Lye, Jessica E., Nordstroem, Terese, Midgley, Stewart M., & Lewis, Robert A. Reference dosimetry at the Australian Synchrotron's imaging and medical beamline using free-air ionization chamber measurements and theoretical predictions of air kerma rate and half value layer. United States. doi:10.1118/1.4803675.
Crosbie, Jeffrey C., Rogers, Peter A. W., Stevenson, Andrew W., Hall, Christopher J., Lye, Jessica E., Nordstroem, Terese, Midgley, Stewart M., and Lewis, Robert A. Sat . "Reference dosimetry at the Australian Synchrotron's imaging and medical beamline using free-air ionization chamber measurements and theoretical predictions of air kerma rate and half value layer". United States. doi:10.1118/1.4803675.
@article{osti_22121031,
title = {Reference dosimetry at the Australian Synchrotron's imaging and medical beamline using free-air ionization chamber measurements and theoretical predictions of air kerma rate and half value layer},
author = {Crosbie, Jeffrey C. and Rogers, Peter A. W. and Stevenson, Andrew W. and Hall, Christopher J. and Lye, Jessica E. and Nordstroem, Terese and Midgley, Stewart M. and Lewis, Robert A.},
abstractNote = {Purpose: Novel, preclinical radiotherapy modalities are being developed at synchrotrons around the world, most notably stereotactic synchrotron radiation therapy and microbeam radiotherapy at the European Synchrotron Radiation Facility in Grenoble, France. The imaging and medical beamline (IMBL) at the Australian Synchrotron has recently become available for preclinical radiotherapy and imaging research with clinical trials, a distinct possibility in the coming years. The aim of this present study was to accurately characterize the synchrotron-generated x-ray beam for the purposes of air kerma-based absolute dosimetry. Methods: The authors used a theoretical model of the energy spectrum from the wiggler source and validated this model by comparing the transmission through copper absorbers (0.1-3.0 mm) against real measurements conducted at the beamline. The authors used a low energy free air ionization chamber (LEFAC) from the Australian Radiation Protection and Nuclear Safety Agency and a commercially available free air chamber (ADC-105) for the measurements. The dimensions of these two chambers are different from one another requiring careful consideration of correction factors. Results: Measured and calculated half value layer (HVL) and air kerma rates differed by less than 3% for the LEFAC when the ion chamber readings were corrected for electron energy loss and ion recombination. The agreement between measured and predicted air kerma rates was less satisfactory for the ADC-105 chamber, however. The LEFAC and ADC measurements produced a first half value layer of 0.405 {+-} 0.015 and 0.412 {+-} 0.016 mm Cu, respectively, compared to the theoretical prediction of 0.427 {+-} 0.012 mm Cu. The theoretical model based upon a spectrum calculator derived a mean beam energy of 61.4 keV with a first half value layer of approximately 30 mm in water. Conclusions: The authors showed in this study their ability to verify the predicted air kerma rate and x-ray attenuation curve on the IMBL using a simple experimental method, namely, HVL measurements. The HVL measurements strongly supports the x-ray beam spectrum, which in turn has a profound effect on x-ray dosimetry.},
doi = {10.1118/1.4803675},
journal = {Medical Physics},
number = 6,
volume = 40,
place = {United States},
year = {Sat Jun 15 00:00:00 EDT 2013},
month = {Sat Jun 15 00:00:00 EDT 2013}
}