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Comparison between TG‐51 and TG‐21: Calibration of photon and electron beams in water using cylindrical chambers
A new calibration protocol, developed by the AAPM Task Group 51 (TG‐51) to replace the TG‐21 protocol, is based on an absorbed‐dose to water standard and calibration factor [Formula: see text] , while the TG‐21 protocol is based on an exposure (or air‐kerma) standard and calibration factor [Formula:...
Autores principales: | , , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
John Wiley and Sons Inc.
2000
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5726169/ https://www.ncbi.nlm.nih.gov/pubmed/11674825 http://dx.doi.org/10.1120/jacmp.v1i3.2643 |
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author | Cho, S. H. Lowenstein, J. R. Balter, P. A. Wells, N. H. Hanson, W. F. |
author_facet | Cho, S. H. Lowenstein, J. R. Balter, P. A. Wells, N. H. Hanson, W. F. |
author_sort | Cho, S. H. |
collection | PubMed |
description | A new calibration protocol, developed by the AAPM Task Group 51 (TG‐51) to replace the TG‐21 protocol, is based on an absorbed‐dose to water standard and calibration factor [Formula: see text] , while the TG‐21 protocol is based on an exposure (or air‐kerma) standard and calibration factor [Formula: see text]. Because of differences between these standards and the two protocols, the results of clinical reference dosimetry based on TG‐51 may be somewhat different from those based on TG‐21. The Radiological Physics Center has conducted a systematic comparison between the two protocols, in which photon and electron beam outputs following both protocols were compared under identical conditions. Cylindrical chambers used in this study were selected from the list given in the TG‐51 report, covering the majority of current manufacturers. Measured ratios between absorbed‐dose and air‐kerma calibration factors, derived from the standards traceable to the NIST, were compared with calculated values using the TG‐21 protocol. The comparison suggests that there is roughly a 1% discrepancy between measured and calculated ratios. This discrepancy may provide a reasonable measure of possible changes between the absorbed‐dose to water determined by TG‐51 and that determined by TG‐21 for photon beam calibrations. The typical change in a 6 MV photon beam calibration following the implementation of the TG‐51 protocol was about 1%, regardless of the chamber used, and the change was somewhat smaller for an 18 MV photon beam. On the other hand, the results for 9 and 16 MeV electron beams show larger changes up to 2%, perhaps because of the updated electron stopping power data used for the TG‐51 protocol, in addition to the inherent 1% discrepancy presented in the calibration factors. The results also indicate that the changes may be dependent on the electron energy. PACS number(s): 87.66.–a, 87.53.–j |
format | Online Article Text |
id | pubmed-5726169 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2000 |
publisher | John Wiley and Sons Inc. |
record_format | MEDLINE/PubMed |
spelling | pubmed-57261692018-04-02 Comparison between TG‐51 and TG‐21: Calibration of photon and electron beams in water using cylindrical chambers Cho, S. H. Lowenstein, J. R. Balter, P. A. Wells, N. H. Hanson, W. F. J Appl Clin Med Phys Radiation Measurements A new calibration protocol, developed by the AAPM Task Group 51 (TG‐51) to replace the TG‐21 protocol, is based on an absorbed‐dose to water standard and calibration factor [Formula: see text] , while the TG‐21 protocol is based on an exposure (or air‐kerma) standard and calibration factor [Formula: see text]. Because of differences between these standards and the two protocols, the results of clinical reference dosimetry based on TG‐51 may be somewhat different from those based on TG‐21. The Radiological Physics Center has conducted a systematic comparison between the two protocols, in which photon and electron beam outputs following both protocols were compared under identical conditions. Cylindrical chambers used in this study were selected from the list given in the TG‐51 report, covering the majority of current manufacturers. Measured ratios between absorbed‐dose and air‐kerma calibration factors, derived from the standards traceable to the NIST, were compared with calculated values using the TG‐21 protocol. The comparison suggests that there is roughly a 1% discrepancy between measured and calculated ratios. This discrepancy may provide a reasonable measure of possible changes between the absorbed‐dose to water determined by TG‐51 and that determined by TG‐21 for photon beam calibrations. The typical change in a 6 MV photon beam calibration following the implementation of the TG‐51 protocol was about 1%, regardless of the chamber used, and the change was somewhat smaller for an 18 MV photon beam. On the other hand, the results for 9 and 16 MeV electron beams show larger changes up to 2%, perhaps because of the updated electron stopping power data used for the TG‐51 protocol, in addition to the inherent 1% discrepancy presented in the calibration factors. The results also indicate that the changes may be dependent on the electron energy. PACS number(s): 87.66.–a, 87.53.–j John Wiley and Sons Inc. 2000-06-01 /pmc/articles/PMC5726169/ /pubmed/11674825 http://dx.doi.org/10.1120/jacmp.v1i3.2643 Text en © 2000 The Authors. This is an open access article under the terms of the Creative Commons Attribution (http://creativecommons.org/licenses/by/3.0/) License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. |
spellingShingle | Radiation Measurements Cho, S. H. Lowenstein, J. R. Balter, P. A. Wells, N. H. Hanson, W. F. Comparison between TG‐51 and TG‐21: Calibration of photon and electron beams in water using cylindrical chambers |
title | Comparison between TG‐51 and TG‐21: Calibration of photon and electron beams in water using cylindrical chambers |
title_full | Comparison between TG‐51 and TG‐21: Calibration of photon and electron beams in water using cylindrical chambers |
title_fullStr | Comparison between TG‐51 and TG‐21: Calibration of photon and electron beams in water using cylindrical chambers |
title_full_unstemmed | Comparison between TG‐51 and TG‐21: Calibration of photon and electron beams in water using cylindrical chambers |
title_short | Comparison between TG‐51 and TG‐21: Calibration of photon and electron beams in water using cylindrical chambers |
title_sort | comparison between tg‐51 and tg‐21: calibration of photon and electron beams in water using cylindrical chambers |
topic | Radiation Measurements |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5726169/ https://www.ncbi.nlm.nih.gov/pubmed/11674825 http://dx.doi.org/10.1120/jacmp.v1i3.2643 |
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