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Title: Poster — Thur Eve — 42: Radiochromic film calibration for low-energy seed brachytherapy dose measurement

Abstract

The purpose of this study was to investigate the accuracy of radiochromic film calibration procedures used in external beam radiotherapy when applied to I-125 brachytherapy sources delivering higher doses, and to determine any necessary modifications to achieve similar accuracy in absolute dose measurements. GafChromic EBT3 film was used to measure radiation doses upwards of 35 Gy from 6 MV, 75 kVp and (∼28 keV) I-125 photon sources. A custom phantom was used for the I-125 irradiations to obtain a larger film area with nearly constant dose to reduce the effects of film heterogeneities on the optical density (OD) measurements. RGB transmission images were obtained with an Epson 10000XL flatbed scanner, and calibration curves relating OD and dose using a rational function were determined for each colour channel and at each energy using a non-linear least square minimization method. Differences found between the 6 MV calibration curve and those for the lower energy sources are large enough that 6 MV beams should not be used to calibrate film for low-energy sources. However, differences between the 75 kVp and I-125 calibration curves were quite small; indicating that 75 kVp is a good choice. Compared with I-125 irradiation, this gives the advantages ofmore » lower type B uncertainties and markedly reduced irradiation time. To obtain high accuracy calibration for the dose range up to 35 Gy, two-segment piece-wise fitting was required. This yielded absolute dose measurement accuracy above 1 Gy of ∼2% for 75 kVp and ∼5% for I-125 seed exposures.« less

Authors:
; ;  [1];  [2]
  1. Department of Medical Physics, Cross Cancer Institute, Edmonton, Alberta T6G 1Z2 (Canada)
  2. (Canada)
Publication Date:
OSTI Identifier:
22407664
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 41; Journal Issue: 8; Other Information: (c) 2014 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
60 APPLIED LIFE SCIENCES; ACCURACY; BRACHYTHERAPY; CALIBRATION; IODINE 125; OPACITY; PHANTOMS; RADIATION DOSES

Citation Formats

Morrison, H, Menon, G, Sloboda, R, and Department of Oncology, University of Alberta, Edmonton, Alberta T6G 2R3. Poster — Thur Eve — 42: Radiochromic film calibration for low-energy seed brachytherapy dose measurement. United States: N. p., 2014. Web. doi:10.1118/1.4894902.
Morrison, H, Menon, G, Sloboda, R, & Department of Oncology, University of Alberta, Edmonton, Alberta T6G 2R3. Poster — Thur Eve — 42: Radiochromic film calibration for low-energy seed brachytherapy dose measurement. United States. doi:10.1118/1.4894902.
Morrison, H, Menon, G, Sloboda, R, and Department of Oncology, University of Alberta, Edmonton, Alberta T6G 2R3. Fri . "Poster — Thur Eve — 42: Radiochromic film calibration for low-energy seed brachytherapy dose measurement". United States. doi:10.1118/1.4894902.
@article{osti_22407664,
title = {Poster — Thur Eve — 42: Radiochromic film calibration for low-energy seed brachytherapy dose measurement},
author = {Morrison, H and Menon, G and Sloboda, R and Department of Oncology, University of Alberta, Edmonton, Alberta T6G 2R3},
abstractNote = {The purpose of this study was to investigate the accuracy of radiochromic film calibration procedures used in external beam radiotherapy when applied to I-125 brachytherapy sources delivering higher doses, and to determine any necessary modifications to achieve similar accuracy in absolute dose measurements. GafChromic EBT3 film was used to measure radiation doses upwards of 35 Gy from 6 MV, 75 kVp and (∼28 keV) I-125 photon sources. A custom phantom was used for the I-125 irradiations to obtain a larger film area with nearly constant dose to reduce the effects of film heterogeneities on the optical density (OD) measurements. RGB transmission images were obtained with an Epson 10000XL flatbed scanner, and calibration curves relating OD and dose using a rational function were determined for each colour channel and at each energy using a non-linear least square minimization method. Differences found between the 6 MV calibration curve and those for the lower energy sources are large enough that 6 MV beams should not be used to calibrate film for low-energy sources. However, differences between the 75 kVp and I-125 calibration curves were quite small; indicating that 75 kVp is a good choice. Compared with I-125 irradiation, this gives the advantages of lower type B uncertainties and markedly reduced irradiation time. To obtain high accuracy calibration for the dose range up to 35 Gy, two-segment piece-wise fitting was required. This yielded absolute dose measurement accuracy above 1 Gy of ∼2% for 75 kVp and ∼5% for I-125 seed exposures.},
doi = {10.1118/1.4894902},
journal = {Medical Physics},
number = 8,
volume = 41,
place = {United States},
year = {Fri Aug 15 00:00:00 EDT 2014},
month = {Fri Aug 15 00:00:00 EDT 2014}
}