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Evaluation of fluence‐based dose delivery incorporating the spatial variation of dosimetric leaf gap (DLG)

The Eclipse treatment planning system uses a single dosimetric leaf gap (DLG) value to retract all multileaf collimator leaf positions during dose calculation to model the rounded leaf ends. This study evaluates the dosimetric impact of the 2D variation of DLG on clinical treatment plans based on th...

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Autores principales: Kumaraswamy, Lalith K., Xu, Zhengzheng, Bailey, Daniel W., Schmitt, Jonathan D., Podgorsak, Matthew B.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: John Wiley and Sons Inc. 2016
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5690211/
https://www.ncbi.nlm.nih.gov/pubmed/26894361
http://dx.doi.org/10.1120/jacmp.v17i1.5883
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author Kumaraswamy, Lalith K.
Xu, Zhengzheng
Bailey, Daniel W.
Schmitt, Jonathan D.
Podgorsak, Matthew B.
author_facet Kumaraswamy, Lalith K.
Xu, Zhengzheng
Bailey, Daniel W.
Schmitt, Jonathan D.
Podgorsak, Matthew B.
author_sort Kumaraswamy, Lalith K.
collection PubMed
description The Eclipse treatment planning system uses a single dosimetric leaf gap (DLG) value to retract all multileaf collimator leaf positions during dose calculation to model the rounded leaf ends. This study evaluates the dosimetric impact of the 2D variation of DLG on clinical treatment plans based on their degree of fluence modulation. In‐house software was developed to retrospectively apply the 2D variation of DLG to 61 clinically treated VMAT plans, as well as to several test plans. The level of modulation of the VMAT cases were determined by calculating their modulation complexity score (MCS). Dose measurements were done using the MapCHECK device at a depth of 5.0 cm for plans with and without the 2D DLG correction. Measurements were compared against predicted dose planes from the TPS using absolute 3%/3 mm and 2%/2 mm gamma criteria for test plans and for VMAT cases, respectively. The gamma pass rate for the 2 mm, 4 mm, and 6 mm sweep test plans increased by 23.2%, 28.7%, and 26.0%, respectively, when the measurements were corrected with 2D variation of DLG. The clinical anal VMAT cases, which had very high MLC modulation, showed the most improvement. The majority of the improvement occurred for doses created by the 1.0 cm width leaves for both the test plans and the VMAT cases. The gamma pass rates for the highly modulated head and neck (H&N) cases, moderately modulated prostate and esophageal cases, and minimally modulated brain cases improved only slightly when corrected with 2D variation of DLG. This is because these cases did not employ the 1.0 cm width leaves for dose calculation and delivery. These data suggest that, at the very least, the TPS plans with highly modulated fluences created by the 1.0 cm fields require 2D DLG correction. Incorporating the 2D variation of DLG for the highly modulated clinical treatment plans improves their planar dose gamma pass rates, especially for fields employing the outer 1.0 cm width MLC leaves. This is because there are differences in DLG between the true DLG exhibited by the 1.0 cm width outer leaves and the constant DLG value modeled by the TPS for dose calculation. PACS numbers: 87.55.D, 87.55.Qr, 87.56.Fc, 87.56.N, 87.56.nk
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spelling pubmed-56902112018-04-02 Evaluation of fluence‐based dose delivery incorporating the spatial variation of dosimetric leaf gap (DLG) Kumaraswamy, Lalith K. Xu, Zhengzheng Bailey, Daniel W. Schmitt, Jonathan D. Podgorsak, Matthew B. J Appl Clin Med Phys Review Articles The Eclipse treatment planning system uses a single dosimetric leaf gap (DLG) value to retract all multileaf collimator leaf positions during dose calculation to model the rounded leaf ends. This study evaluates the dosimetric impact of the 2D variation of DLG on clinical treatment plans based on their degree of fluence modulation. In‐house software was developed to retrospectively apply the 2D variation of DLG to 61 clinically treated VMAT plans, as well as to several test plans. The level of modulation of the VMAT cases were determined by calculating their modulation complexity score (MCS). Dose measurements were done using the MapCHECK device at a depth of 5.0 cm for plans with and without the 2D DLG correction. Measurements were compared against predicted dose planes from the TPS using absolute 3%/3 mm and 2%/2 mm gamma criteria for test plans and for VMAT cases, respectively. The gamma pass rate for the 2 mm, 4 mm, and 6 mm sweep test plans increased by 23.2%, 28.7%, and 26.0%, respectively, when the measurements were corrected with 2D variation of DLG. The clinical anal VMAT cases, which had very high MLC modulation, showed the most improvement. The majority of the improvement occurred for doses created by the 1.0 cm width leaves for both the test plans and the VMAT cases. The gamma pass rates for the highly modulated head and neck (H&N) cases, moderately modulated prostate and esophageal cases, and minimally modulated brain cases improved only slightly when corrected with 2D variation of DLG. This is because these cases did not employ the 1.0 cm width leaves for dose calculation and delivery. These data suggest that, at the very least, the TPS plans with highly modulated fluences created by the 1.0 cm fields require 2D DLG correction. Incorporating the 2D variation of DLG for the highly modulated clinical treatment plans improves their planar dose gamma pass rates, especially for fields employing the outer 1.0 cm width MLC leaves. This is because there are differences in DLG between the true DLG exhibited by the 1.0 cm width outer leaves and the constant DLG value modeled by the TPS for dose calculation. PACS numbers: 87.55.D, 87.55.Qr, 87.56.Fc, 87.56.N, 87.56.nk John Wiley and Sons Inc. 2016-01-08 /pmc/articles/PMC5690211/ /pubmed/26894361 http://dx.doi.org/10.1120/jacmp.v17i1.5883 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 Review Articles
Kumaraswamy, Lalith K.
Xu, Zhengzheng
Bailey, Daniel W.
Schmitt, Jonathan D.
Podgorsak, Matthew B.
Evaluation of fluence‐based dose delivery incorporating the spatial variation of dosimetric leaf gap (DLG)
title Evaluation of fluence‐based dose delivery incorporating the spatial variation of dosimetric leaf gap (DLG)
title_full Evaluation of fluence‐based dose delivery incorporating the spatial variation of dosimetric leaf gap (DLG)
title_fullStr Evaluation of fluence‐based dose delivery incorporating the spatial variation of dosimetric leaf gap (DLG)
title_full_unstemmed Evaluation of fluence‐based dose delivery incorporating the spatial variation of dosimetric leaf gap (DLG)
title_short Evaluation of fluence‐based dose delivery incorporating the spatial variation of dosimetric leaf gap (DLG)
title_sort evaluation of fluence‐based dose delivery incorporating the spatial variation of dosimetric leaf gap (dlg)
topic Review Articles
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5690211/
https://www.ncbi.nlm.nih.gov/pubmed/26894361
http://dx.doi.org/10.1120/jacmp.v17i1.5883
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