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Title: Film dosimetry calibration method for pulsed-dose-rate brachytherapy with an {sup 192}Ir source

Abstract

{sup 192}Ir sources have been widely used in clinical brachytherapy. An important challenge is to perform dosimetric measurements close to the source despite the steep dose gradient. The common, inexpensive silver halide film is a classic two-dimensional integrator dosimeter and would be an attractive solution for these dose measurements. The main disadvantage of film dosimetry is the film response to the low-energy photon. Since the photon energy spectrum is known to vary with depth, the sensitometric curves are expected to be dependent on depth. The purpose of this study is to suggest a correction method for silver halide film dosimetry that overcomes the response changes at different depths. Sensitometric curves have been obtained at different depths with verification film near a 1 Ci {sup 192}Ir pulsed-dose-rate source. The depth dependence of the film response was observed and a correction function was established. The suitability of the method was tested through measurement of the radial dose profile and radial dose function. The results were compared to Monte Carlo-simulated values according to the TG43 formalism. Monte Carlo simulations were performed separately for the beta and gamma source emissions, using the EGS4 code system, including the low-energy photon and electron transport optimization procedures.more » The beta source emission simulation showed that the beta dose contribution could be neglected and therefore the film-depth dependence could not be attributed to this part of the source radioactivity. The gamma source emission simulations included photon-spectra collection at several depths. The results showed a depth-dependent softening of the photon spectrum that can explain the film-energy dependence.« less

Authors:
;  [1]
  1. Department of Nuclear Engineering, Ben-Gurion University of the Negev, POB 653, 84105 Beer-Sheva (Israel)
Publication Date:
OSTI Identifier:
20951298
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 34; Journal Issue: 5; Other Information: DOI: 10.1118/1.2719366; (c) 2007 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
62 RADIOLOGY AND NUCLEAR MEDICINE; BETA SOURCES; BRACHYTHERAPY; CALIBRATION; COMPUTERIZED SIMULATION; DOSE RATES; DOSEMETERS; ENERGY SPECTRA; FILM DOSIMETRY; GAMMA RADIATION; GAMMA SOURCES; IRIDIUM 192; MONTE CARLO METHOD; PHANTOMS; PHOTONS; RADIATION DOSES

Citation Formats

Schwob, Nathan, and Orion, Itzhak. Film dosimetry calibration method for pulsed-dose-rate brachytherapy with an {sup 192}Ir source. United States: N. p., 2007. Web. doi:10.1118/1.2719366.
Schwob, Nathan, & Orion, Itzhak. Film dosimetry calibration method for pulsed-dose-rate brachytherapy with an {sup 192}Ir source. United States. doi:10.1118/1.2719366.
Schwob, Nathan, and Orion, Itzhak. Tue . "Film dosimetry calibration method for pulsed-dose-rate brachytherapy with an {sup 192}Ir source". United States. doi:10.1118/1.2719366.
@article{osti_20951298,
title = {Film dosimetry calibration method for pulsed-dose-rate brachytherapy with an {sup 192}Ir source},
author = {Schwob, Nathan and Orion, Itzhak},
abstractNote = {{sup 192}Ir sources have been widely used in clinical brachytherapy. An important challenge is to perform dosimetric measurements close to the source despite the steep dose gradient. The common, inexpensive silver halide film is a classic two-dimensional integrator dosimeter and would be an attractive solution for these dose measurements. The main disadvantage of film dosimetry is the film response to the low-energy photon. Since the photon energy spectrum is known to vary with depth, the sensitometric curves are expected to be dependent on depth. The purpose of this study is to suggest a correction method for silver halide film dosimetry that overcomes the response changes at different depths. Sensitometric curves have been obtained at different depths with verification film near a 1 Ci {sup 192}Ir pulsed-dose-rate source. The depth dependence of the film response was observed and a correction function was established. The suitability of the method was tested through measurement of the radial dose profile and radial dose function. The results were compared to Monte Carlo-simulated values according to the TG43 formalism. Monte Carlo simulations were performed separately for the beta and gamma source emissions, using the EGS4 code system, including the low-energy photon and electron transport optimization procedures. The beta source emission simulation showed that the beta dose contribution could be neglected and therefore the film-depth dependence could not be attributed to this part of the source radioactivity. The gamma source emission simulations included photon-spectra collection at several depths. The results showed a depth-dependent softening of the photon spectrum that can explain the film-energy dependence.},
doi = {10.1118/1.2719366},
journal = {Medical Physics},
number = 5,
volume = 34,
place = {United States},
year = {Tue May 15 00:00:00 EDT 2007},
month = {Tue May 15 00:00:00 EDT 2007}
}