Cargando…

Characteristics of non-coplanar IMRT in the presence of target-embedded organs at risk

BACKGROUND: The aim is to analyze characteristics and to study the potentials of non-coplanar intensity modulated radiation therapy (IMRT) techniques. The planning study applies to generalized organ at risk (OAR) – planning target volume (PTV) geometries. METHODS: The authors focus on OARs embedded...

Descripción completa

Detalles Bibliográficos
Autores principales: Bratengeier, Klaus, Holubyev, Kostyantyn
Formato: Online Artículo Texto
Lenguaje:English
Publicado: BioMed Central 2015
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5480416/
https://www.ncbi.nlm.nih.gov/pubmed/26458947
http://dx.doi.org/10.1186/s13014-015-0494-5
_version_ 1783245288628027392
author Bratengeier, Klaus
Holubyev, Kostyantyn
author_facet Bratengeier, Klaus
Holubyev, Kostyantyn
author_sort Bratengeier, Klaus
collection PubMed
description BACKGROUND: The aim is to analyze characteristics and to study the potentials of non-coplanar intensity modulated radiation therapy (IMRT) techniques. The planning study applies to generalized organ at risk (OAR) – planning target volume (PTV) geometries. METHODS: The authors focus on OARs embedded in the PTV. The OAR shapes are spherically symmetric (A), cylindrical (B), and bended (C). Several IMRT techniques are used for the planning study: a) non-coplanar quasi-isotropic; b) two sets of equidistant coplanar beams, half of beams incident in a plane perpendicular to the principal plane; c) coplanar equidistant (reference); d) coplanar plus one orthogonal beam. The number of beam directions varies from 9 to 16. The orientation of the beam sets is systematically changed; dose distributions resulting from optimal fluence are explored. A selection of plans is optimized with direct machine parameter optimization (DMPO) allowing 120 and 64 segments. The overall plan quality, PTV coverage, and OAR sparing are evaluated. RESULTS: For all fluence based techniques in cases A and C, plan quality increased considerably if more irradiation directions were used. For the cylindrically symmetric case B, however, only a weak beam number dependence was observed for the best beam set orientation, for which non-coplanar directions could be found where OAR- and PTV-projections did not overlap. IMRT plans using quasi-isotropical distributed non-coplanar beams showed stable results for all topologies A, B, C, as long as 16 beams were chosen; also the most unfavorable beam arrangement created results of similar quality as the optimally oriented coplanar configuration. For smaller number of beams or application in the trunk, a coplanar technique with additional orthogonal beam could be recommended. Techniques using 120 segments created by DMPO could qualitatively reproduce the fluence based results. However, for a reduced number of segments the beam number dependence declined or even reversed for the used planning system and the plan quality degraded substantially. CONCLUSIONS: Topologies with targets encompassing sensitive OAR require sufficient number of beams of 15 or more. For the subgroup of topologies where beam incidences are possible which cover the whole PTV without direct OAR irradiation, the quality dependence on the number of beams is much less pronounced above 9 beams. However, these special non-coplanar beam directions have to be found. On the basis of this work the non-coplanar IMRT techniques can be chosen for further clinical planning studies. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s13014-015-0494-5) contains supplementary material, which is available to authorized users.
format Online
Article
Text
id pubmed-5480416
institution National Center for Biotechnology Information
language English
publishDate 2015
publisher BioMed Central
record_format MEDLINE/PubMed
spelling pubmed-54804162017-06-23 Characteristics of non-coplanar IMRT in the presence of target-embedded organs at risk Bratengeier, Klaus Holubyev, Kostyantyn Radiat Oncol Research BACKGROUND: The aim is to analyze characteristics and to study the potentials of non-coplanar intensity modulated radiation therapy (IMRT) techniques. The planning study applies to generalized organ at risk (OAR) – planning target volume (PTV) geometries. METHODS: The authors focus on OARs embedded in the PTV. The OAR shapes are spherically symmetric (A), cylindrical (B), and bended (C). Several IMRT techniques are used for the planning study: a) non-coplanar quasi-isotropic; b) two sets of equidistant coplanar beams, half of beams incident in a plane perpendicular to the principal plane; c) coplanar equidistant (reference); d) coplanar plus one orthogonal beam. The number of beam directions varies from 9 to 16. The orientation of the beam sets is systematically changed; dose distributions resulting from optimal fluence are explored. A selection of plans is optimized with direct machine parameter optimization (DMPO) allowing 120 and 64 segments. The overall plan quality, PTV coverage, and OAR sparing are evaluated. RESULTS: For all fluence based techniques in cases A and C, plan quality increased considerably if more irradiation directions were used. For the cylindrically symmetric case B, however, only a weak beam number dependence was observed for the best beam set orientation, for which non-coplanar directions could be found where OAR- and PTV-projections did not overlap. IMRT plans using quasi-isotropical distributed non-coplanar beams showed stable results for all topologies A, B, C, as long as 16 beams were chosen; also the most unfavorable beam arrangement created results of similar quality as the optimally oriented coplanar configuration. For smaller number of beams or application in the trunk, a coplanar technique with additional orthogonal beam could be recommended. Techniques using 120 segments created by DMPO could qualitatively reproduce the fluence based results. However, for a reduced number of segments the beam number dependence declined or even reversed for the used planning system and the plan quality degraded substantially. CONCLUSIONS: Topologies with targets encompassing sensitive OAR require sufficient number of beams of 15 or more. For the subgroup of topologies where beam incidences are possible which cover the whole PTV without direct OAR irradiation, the quality dependence on the number of beams is much less pronounced above 9 beams. However, these special non-coplanar beam directions have to be found. On the basis of this work the non-coplanar IMRT techniques can be chosen for further clinical planning studies. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s13014-015-0494-5) contains supplementary material, which is available to authorized users. BioMed Central 2015-10-12 /pmc/articles/PMC5480416/ /pubmed/26458947 http://dx.doi.org/10.1186/s13014-015-0494-5 Text en © Bratengeier and Holubyev. 2016 Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
spellingShingle Research
Bratengeier, Klaus
Holubyev, Kostyantyn
Characteristics of non-coplanar IMRT in the presence of target-embedded organs at risk
title Characteristics of non-coplanar IMRT in the presence of target-embedded organs at risk
title_full Characteristics of non-coplanar IMRT in the presence of target-embedded organs at risk
title_fullStr Characteristics of non-coplanar IMRT in the presence of target-embedded organs at risk
title_full_unstemmed Characteristics of non-coplanar IMRT in the presence of target-embedded organs at risk
title_short Characteristics of non-coplanar IMRT in the presence of target-embedded organs at risk
title_sort characteristics of non-coplanar imrt in the presence of target-embedded organs at risk
topic Research
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5480416/
https://www.ncbi.nlm.nih.gov/pubmed/26458947
http://dx.doi.org/10.1186/s13014-015-0494-5
work_keys_str_mv AT bratengeierklaus characteristicsofnoncoplanarimrtinthepresenceoftargetembeddedorgansatrisk
AT holubyevkostyantyn characteristicsofnoncoplanarimrtinthepresenceoftargetembeddedorgansatrisk