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Clinically relevant investigation of flattening filter‐free skin dose
As flattening filter‐free (FFF) photon beams become readily available for treatment delivery in techniques such as SBRT, thorough investigation of skin dose from FFF photon beams is necessary under clinically relevant conditions. Using a parallel‐plate PTW Markus chamber placed in a custom water‐equ...
Autores principales: | , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
John Wiley and Sons Inc.
2016
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5690509/ https://www.ncbi.nlm.nih.gov/pubmed/27929489 http://dx.doi.org/10.1120/jacmp.v17i6.6307 |
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author | Guy, Christopher L. Karki, Kishor Sharma, Manju Kim, Siyong |
author_facet | Guy, Christopher L. Karki, Kishor Sharma, Manju Kim, Siyong |
author_sort | Guy, Christopher L. |
collection | PubMed |
description | As flattening filter‐free (FFF) photon beams become readily available for treatment delivery in techniques such as SBRT, thorough investigation of skin dose from FFF photon beams is necessary under clinically relevant conditions. Using a parallel‐plate PTW Markus chamber placed in a custom water‐equivalent phantom, surface‐dose measurements were taken at [Formula: see text] , and [Formula: see text] field sizes, at 80, 90, and 100 cm source‐to‐surface distances (SSDs), and with fields defined by jaws and multileaf collimator (MLC) using multiple beam energies (6X, 6XFFF, 10X, and 10XFFF). The same set of measurements was repeated with the chamber at a reference depth of 10 cm. Each surface measurement was normalized by its corresponding reference depth measurement for analysis. The FFF surface doses at 100 cm SSD were higher than flattened surface doses by 45% at [Formula: see text] to 13% at [Formula: see text] for 6 MV energy. These surface dose differences varied to a greater degree as energy increased, ranging from [Formula: see text] at [Formula: see text] to [Formula: see text] at [Formula: see text] for 10 MV. At small field sizes, higher energy increased FFF surface dose relative to flattened surface dose; while at larger field sizes, relative FFF surface dose was higher for lower energies. At both energies investigated, decreasing SSD caused a decrease in the ratios of FFF‐to‐flattened surface dose. Variability with SSD of FFF‐to‐flattened surface dose differences increased with field size and ranged from 0% to 6%. The field size at which FFF and flattened beams gave the same skin dose increased with decreasing beam energy. Surface dose was higher with MLC fields compared to jaw fields under most conditions, with the difference reaching its maximum at a field size between [Formula: see text] and [Formula: see text] for a given energy and SSD. This study conveyed the magnitude of surface dose in a clinically meaningful manner by reporting results normalized to 10 cm depth dose instead of depth of dose maximum. PACS number(s): 87.53.Bn, 87.53.Ly, 87.55.‐x, 87.55.N‐, 87.56.N‐ |
format | Online Article Text |
id | pubmed-5690509 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2016 |
publisher | John Wiley and Sons Inc. |
record_format | MEDLINE/PubMed |
spelling | pubmed-56905092018-04-02 Clinically relevant investigation of flattening filter‐free skin dose Guy, Christopher L. Karki, Kishor Sharma, Manju Kim, Siyong J Appl Clin Med Phys Radiation Oncology Physics As flattening filter‐free (FFF) photon beams become readily available for treatment delivery in techniques such as SBRT, thorough investigation of skin dose from FFF photon beams is necessary under clinically relevant conditions. Using a parallel‐plate PTW Markus chamber placed in a custom water‐equivalent phantom, surface‐dose measurements were taken at [Formula: see text] , and [Formula: see text] field sizes, at 80, 90, and 100 cm source‐to‐surface distances (SSDs), and with fields defined by jaws and multileaf collimator (MLC) using multiple beam energies (6X, 6XFFF, 10X, and 10XFFF). The same set of measurements was repeated with the chamber at a reference depth of 10 cm. Each surface measurement was normalized by its corresponding reference depth measurement for analysis. The FFF surface doses at 100 cm SSD were higher than flattened surface doses by 45% at [Formula: see text] to 13% at [Formula: see text] for 6 MV energy. These surface dose differences varied to a greater degree as energy increased, ranging from [Formula: see text] at [Formula: see text] to [Formula: see text] at [Formula: see text] for 10 MV. At small field sizes, higher energy increased FFF surface dose relative to flattened surface dose; while at larger field sizes, relative FFF surface dose was higher for lower energies. At both energies investigated, decreasing SSD caused a decrease in the ratios of FFF‐to‐flattened surface dose. Variability with SSD of FFF‐to‐flattened surface dose differences increased with field size and ranged from 0% to 6%. The field size at which FFF and flattened beams gave the same skin dose increased with decreasing beam energy. Surface dose was higher with MLC fields compared to jaw fields under most conditions, with the difference reaching its maximum at a field size between [Formula: see text] and [Formula: see text] for a given energy and SSD. This study conveyed the magnitude of surface dose in a clinically meaningful manner by reporting results normalized to 10 cm depth dose instead of depth of dose maximum. PACS number(s): 87.53.Bn, 87.53.Ly, 87.55.‐x, 87.55.N‐, 87.56.N‐ John Wiley and Sons Inc. 2016-11-08 /pmc/articles/PMC5690509/ /pubmed/27929489 http://dx.doi.org/10.1120/jacmp.v17i6.6307 Text en © 2016 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 Oncology Physics Guy, Christopher L. Karki, Kishor Sharma, Manju Kim, Siyong Clinically relevant investigation of flattening filter‐free skin dose |
title | Clinically relevant investigation of flattening filter‐free skin dose |
title_full | Clinically relevant investigation of flattening filter‐free skin dose |
title_fullStr | Clinically relevant investigation of flattening filter‐free skin dose |
title_full_unstemmed | Clinically relevant investigation of flattening filter‐free skin dose |
title_short | Clinically relevant investigation of flattening filter‐free skin dose |
title_sort | clinically relevant investigation of flattening filter‐free skin dose |
topic | Radiation Oncology Physics |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5690509/ https://www.ncbi.nlm.nih.gov/pubmed/27929489 http://dx.doi.org/10.1120/jacmp.v17i6.6307 |
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