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Quantitative analysis of in-air output ratio

Output factor (S(cp)) is one of the important factors required to calculate monitor unit (MU), and is divided into two components: phantom scatter factor (S(p)) and in-air output ratio (S(c)). Generally, S(c) for arbitrary fields are calculated using several methods based on S(c) determined by the a...

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Autores principales: Miyashita, Hisayuki, Hatanaka, Shogo, Fujita, Yukio, Hashimoto, Shimpei, Myojyoyama, Atsushi, Saitoh, Hidetoshi
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Oxford University Press 2013
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3650743/
https://www.ncbi.nlm.nih.gov/pubmed/23292148
http://dx.doi.org/10.1093/jrr/rrs118
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author Miyashita, Hisayuki
Hatanaka, Shogo
Fujita, Yukio
Hashimoto, Shimpei
Myojyoyama, Atsushi
Saitoh, Hidetoshi
author_facet Miyashita, Hisayuki
Hatanaka, Shogo
Fujita, Yukio
Hashimoto, Shimpei
Myojyoyama, Atsushi
Saitoh, Hidetoshi
author_sort Miyashita, Hisayuki
collection PubMed
description Output factor (S(cp)) is one of the important factors required to calculate monitor unit (MU), and is divided into two components: phantom scatter factor (S(p)) and in-air output ratio (S(c)). Generally, S(c) for arbitrary fields are calculated using several methods based on S(c) determined by the absorbed dose measurement for several square fields. However, there are calculation errors when the treatment field has a large aspect ratio and the opening of upper and lower collimator are exchanged. To determine S(c) accurately, scattered photons from the treatment head and backscattered particles into the monitor chamber must be analyzed individually. In this report, a simulation model that agreed well with measured S(c) was constructed and dose variation by scattered photons from the treatment head and by backscattered particles into the monitor chamber was analyzed quantitatively. The results showed that the contribution of scattered photons from the primary collimator was larger than that of the flattening filter, and backscattered particles were affected by not only the upper jaw but also the lower jaw. In future work, a new S(c) determination algorism based on the result of this report will be proposed.
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spelling pubmed-36507432013-05-13 Quantitative analysis of in-air output ratio Miyashita, Hisayuki Hatanaka, Shogo Fujita, Yukio Hashimoto, Shimpei Myojyoyama, Atsushi Saitoh, Hidetoshi J Radiat Res Technology Output factor (S(cp)) is one of the important factors required to calculate monitor unit (MU), and is divided into two components: phantom scatter factor (S(p)) and in-air output ratio (S(c)). Generally, S(c) for arbitrary fields are calculated using several methods based on S(c) determined by the absorbed dose measurement for several square fields. However, there are calculation errors when the treatment field has a large aspect ratio and the opening of upper and lower collimator are exchanged. To determine S(c) accurately, scattered photons from the treatment head and backscattered particles into the monitor chamber must be analyzed individually. In this report, a simulation model that agreed well with measured S(c) was constructed and dose variation by scattered photons from the treatment head and by backscattered particles into the monitor chamber was analyzed quantitatively. The results showed that the contribution of scattered photons from the primary collimator was larger than that of the flattening filter, and backscattered particles were affected by not only the upper jaw but also the lower jaw. In future work, a new S(c) determination algorism based on the result of this report will be proposed. Oxford University Press 2013-05 2013-01-04 /pmc/articles/PMC3650743/ /pubmed/23292148 http://dx.doi.org/10.1093/jrr/rrs118 Text en © The Author 2013. Published by Oxford University Press on behalf of The Japan Radiation Research Society and Japanese Society for Therapeutic Radiology and Oncology. http://creativecommons.org/licenses/by-nc/3.0/ This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/), which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
spellingShingle Technology
Miyashita, Hisayuki
Hatanaka, Shogo
Fujita, Yukio
Hashimoto, Shimpei
Myojyoyama, Atsushi
Saitoh, Hidetoshi
Quantitative analysis of in-air output ratio
title Quantitative analysis of in-air output ratio
title_full Quantitative analysis of in-air output ratio
title_fullStr Quantitative analysis of in-air output ratio
title_full_unstemmed Quantitative analysis of in-air output ratio
title_short Quantitative analysis of in-air output ratio
title_sort quantitative analysis of in-air output ratio
topic Technology
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3650743/
https://www.ncbi.nlm.nih.gov/pubmed/23292148
http://dx.doi.org/10.1093/jrr/rrs118
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