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The effect of ambient pressure on well chamber response: Monte Carlo calculated results for the HDR 1000 plus.

Publication ,  Journal Article
Bohm, TD; Griffin, SL; DeLuca, PM; DeWerd, LA
Published in: Med Phys
April 2005

The determination of the air kerma strength of a brachytherapy seed is necessary for effective treatment planning. Well ionization chambers are used on site at therapy clinics to determine the air kerma strength of seeds. In this work, the response of the Standard Imaging HDR 1000 Plus well chamber to ambient pressure is examined using Monte Carlo calculations. The experimental work examining the response of this chamber as well as other chambers is presented in a companion paper. The Monte Carlo results show that for low-energy photon sources, the application of the standard temperature pressure PTP correction factor produces an over-response at the reduced air densities/pressures corresponding to high elevations. With photon sources of 20 to 40 keV, the normalized PTP corrected chamber response is as much as 10% to 20% over unity for air densities/pressures corresponding to an elevation of 3048 m (10000 ft) above sea level. At air densities corresponding to an elevation of 1524 m (5000 ft), the normalized PTP-corrected chamber response is 5% to 10% over unity for these photon sources. With higher-energy photon sources (>100 keV), the normalized PTP corrected chamber response is near unity. For low-energy beta sources of 0.25 to 0.50 MeV, the normalized PTP-corrected chamber response is as much as 4% to 12% over unity for air densities/pressures corresponding to an elevation of 3048 m (10000 ft) above sea level. Higher-energy beta sources (>0.75 MeV) have a normalized PTP corrected chamber response near unity. Comparing calculated and measured chamber responses for common 103Pd- and 125I-based brachytherapy seeds show agreement to within 2.7% and 1.9%, respectively. Comparing MCNP calculated chamber responses with EGSnrc calculated chamber responses show agreement to within 3.1% at photon energies of 20 to 40 keV. We conclude that Monte Carlo transport calculations accurately model the response of this well chamber. Further, applying the standard PTP correction factor for this well chamber is insufficient in accounting for the change in chamber response with air pressure for low-energy (<100 keV) photon and low-energy (<0.75 MeV)beta sources.

Duke Scholars

Published In

Med Phys

DOI

ISSN

0094-2405

Publication Date

April 2005

Volume

32

Issue

4

Start / End Page

1103 / 1114

Location

United States

Related Subject Headings

  • Temperature
  • Software
  • Radiometry
  • Radioisotopes
  • Pressure
  • Photons
  • Palladium
  • Nuclear Medicine & Medical Imaging
  • Monte Carlo Method
  • Models, Statistical
 

Citation

APA
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ICMJE
MLA
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Bohm, T. D., Griffin, S. L., DeLuca, P. M., & DeWerd, L. A. (2005). The effect of ambient pressure on well chamber response: Monte Carlo calculated results for the HDR 1000 plus. Med Phys, 32(4), 1103–1114. https://doi.org/10.1118/1.1884905
Bohm, Tim D., Sheridan L. Griffin, Paul M. DeLuca, and Larry A. DeWerd. “The effect of ambient pressure on well chamber response: Monte Carlo calculated results for the HDR 1000 plus.Med Phys 32, no. 4 (April 2005): 1103–14. https://doi.org/10.1118/1.1884905.
Bohm TD, Griffin SL, DeLuca PM, DeWerd LA. The effect of ambient pressure on well chamber response: Monte Carlo calculated results for the HDR 1000 plus. Med Phys. 2005 Apr;32(4):1103–14.
Bohm, Tim D., et al. “The effect of ambient pressure on well chamber response: Monte Carlo calculated results for the HDR 1000 plus.Med Phys, vol. 32, no. 4, Apr. 2005, pp. 1103–14. Pubmed, doi:10.1118/1.1884905.
Bohm TD, Griffin SL, DeLuca PM, DeWerd LA. The effect of ambient pressure on well chamber response: Monte Carlo calculated results for the HDR 1000 plus. Med Phys. 2005 Apr;32(4):1103–1114.

Published In

Med Phys

DOI

ISSN

0094-2405

Publication Date

April 2005

Volume

32

Issue

4

Start / End Page

1103 / 1114

Location

United States

Related Subject Headings

  • Temperature
  • Software
  • Radiometry
  • Radioisotopes
  • Pressure
  • Photons
  • Palladium
  • Nuclear Medicine & Medical Imaging
  • Monte Carlo Method
  • Models, Statistical