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In water calibration of PDR 192Ir brachytherapy sources with an NE2571 ionization chamber

(1998) PHYSICS IN MEDICINE AND BIOLOGY. 43(8). p.2095-2107
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Abstract
An ionometric calibration procedure for Ir-192 PDR brachytherapy sources in terms of dose rate to water is presented. The calibration of the source is performed directly in a water phantom at short distances (1.0, 2.5 and 5.0 cm) using an NE2571 Farmer type ion chamber. To convert the measured air-kerma rate in water to dose rate to water a conversion factor (CF) was calculated by adapting the medium-energy, x-ray dosimetry protocol for a point source geometry (diverging beam). The obtained CF was verified using two different methods. Firstly, the CF was calculated by Monte Carlo simulations, where the source-ionization chamber geometry was modelled accurately. In a second method, a combination of Monte Carlo simulations and measurements of the air-kerma rate in water (at 1.0, 2.5 and 5.0 cm distance) and in air (1 m distance) was used to determine the CF. The obtained CFs were also compared with conversion factors calculated with the adapted dosimetry protocol for high-energy photons introduced by Tolli. All calculations were done for a Gammamed PDR Ir-192 source-NE2571 chamber geometry. The conversion factors obtained with the four different methods agree to within 1% at the three distances of interest. We obtained the following values (medium-energy x-ray protocol): CF(1 cm) = 1.458; CF(2.5 cm) = 1.162; CF(5.0 cm) = 1.112 (1 sigma = 0.7% for the three distances of interest). The obtained results were checked with TLD measurements. The values of the specific dose rate constant and the radial dose function calculated in this work are in accordance with the literature data.
Keywords
DOSIMETRY, MONTE-CARLO, BEAMS

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Chicago
Reynaert, Nick, Frans Verhaegen, and Hubert Thierens. 1998. “In Water Calibration of PDR 192Ir Brachytherapy Sources with an NE2571 Ionization Chamber.” Physics in Medicine and Biology 43 (8): 2095–2107.
APA
Reynaert, N., Verhaegen, F., & Thierens, H. (1998). In water calibration of PDR 192Ir brachytherapy sources with an NE2571 ionization chamber. PHYSICS IN MEDICINE AND BIOLOGY, 43(8), 2095–2107.
Vancouver
1.
Reynaert N, Verhaegen F, Thierens H. In water calibration of PDR 192Ir brachytherapy sources with an NE2571 ionization chamber. PHYSICS IN MEDICINE AND BIOLOGY. 1998;43(8):2095–107.
MLA
Reynaert, Nick, Frans Verhaegen, and Hubert Thierens. “In Water Calibration of PDR 192Ir Brachytherapy Sources with an NE2571 Ionization Chamber.” PHYSICS IN MEDICINE AND BIOLOGY 43.8 (1998): 2095–2107. Print.
@article{276541,
  abstract     = {An ionometric calibration procedure for Ir-192 PDR brachytherapy sources in terms of dose rate to water is presented. The calibration of the source is performed directly in a water phantom at short distances (1.0, 2.5 and 5.0 cm) using an NE2571 Farmer type ion chamber. To convert the measured air-kerma rate in water to dose rate to water a conversion factor (CF) was calculated by adapting the medium-energy, x-ray dosimetry protocol for a point source geometry (diverging beam). The obtained CF was verified using two different methods. Firstly, the CF was calculated by Monte Carlo simulations, where the source-ionization chamber geometry was modelled accurately. In a second method, a combination of Monte Carlo simulations and measurements of the air-kerma rate in water (at 1.0, 2.5 and 5.0 cm distance) and in air (1 m distance) was used to determine the CF. The obtained CFs were also compared with conversion factors calculated with the adapted dosimetry protocol for high-energy photons introduced by Tolli. All calculations were done for a Gammamed PDR Ir-192 source-NE2571 chamber geometry. The conversion factors obtained with the four different methods agree to within 1\% at the three distances of interest. We obtained the following values (medium-energy x-ray protocol): CF(1 cm) = 1.458; CF(2.5 cm) = 1.162; CF(5.0 cm) = 1.112 (1 sigma = 0.7\% for the three distances of interest).
The obtained results were checked with TLD measurements. The values of the specific dose rate constant and the radial dose function calculated in this work are in accordance with the literature data.},
  author       = {Reynaert, Nick and Verhaegen, Frans and Thierens, Hubert},
  issn         = {0031-9155},
  journal      = {PHYSICS IN MEDICINE AND BIOLOGY},
  keyword      = {DOSIMETRY,MONTE-CARLO,BEAMS},
  language     = {eng},
  number       = {8},
  pages        = {2095--2107},
  title        = {In water calibration of PDR 192Ir brachytherapy sources with an NE2571 ionization chamber},
  url          = {http://dx.doi.org/10.1088/0031-9155/43/8/008},
  volume       = {43},
  year         = {1998},
}

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