Validation of a Monte Carlo framework for out-of-field dose calculations in proton therapy

De Saint-Hubert, Marijke; Verbeek, Nico; Bäumer, Christian; Esser, Johannes; Wulff, Jörg; Nabha, Racell; Van Hoey, Olivier; Dabin, Jérémie; Stuckmann, Florian; Vasi, Fabiano; Radonic, Stephan; Boissonnat, Guillaume; Schneider, Uwe; Rodriguez, Miguel; Timmermann, Beate; Thierry-Chef, Isabelle; Brualla, Lorenzo

Validation of a Monte Carlo framework for out-of-field dose calculations in proton therapy

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dc.contributor.author De Saint-Hubert, Marijke
dc.contributor.author Verbeek, Nico
dc.contributor.author Bäumer, Christian
dc.contributor.author Esser, Johannes
dc.contributor.author Wulff, Jörg
dc.contributor.author Nabha, Racell
dc.contributor.author Van Hoey, Olivier
dc.contributor.author Dabin, Jérémie
dc.contributor.author Stuckmann, Florian
dc.contributor.author Vasi, Fabiano
dc.contributor.author Radonic, Stephan
dc.contributor.author Boissonnat, Guillaume
dc.contributor.author Schneider, Uwe
dc.contributor.author Rodriguez, Miguel
dc.contributor.author Timmermann, Beate
dc.contributor.author Thierry-Chef, Isabelle
dc.contributor.author Brualla, Lorenzo
dc.date.accessioned 2022-12-02T07:11:31Z
dc.date.available 2022-12-02T07:11:31Z
dc.date.issued 2022
dc.description.abstract Proton therapy enables to deliver highly conformed dose distributions owing to the characteristic Bragg peak and the finite range of protons. However, during proton therapy, secondary neutrons are created, which can travel long distances and deposit dose in out-of-field volumes. This out-of-field absorbed dose needs to be considered for radiation-induced secondary cancers, which are particularly relevant in the case of pediatric treatments. Unfortunately, no method exists in clinics for the computation of the out-of-field dose distributions in proton therapy. To help overcome this limitation, a computational tool has been developed based on the Monte Carlo code TOPAS. The purpose of this work is to evaluate the accuracy of this tool in comparison to experimental data obtained from an anthropomorphic phantom irradiation. An anthropomorphic phantom of a 5-year-old child (ATOM, CIRS) was irradiated for a brain tumor treatment in an IBA Proteus Plus facility using a pencil beam dedicated nozzle. The treatment consisted of three pencil beam scanning fields employing a lucite range shifter. Proton energies ranged from 100 to 165 MeV. A median dose of 50.4 Gy(RBE) with 1.8 Gy(RBE) per fraction was prescribed to the initial planning target volume (PTV), which was located in the cerebellum. Thermoluminescent detectors (TLDs), namely, Li-7-enriched LiF : Mg, Ti (MTS-7) type, were used to detect gamma radiation, which is produced by nuclear reactions, and secondary as well as recoil protons created out-of-field by secondary neutrons. Li-6-enriched LiF : Mg,Cu,P (MCP-6) was combined with Li-7-enriched MCP-7 to measure thermal neutrons. TLDs were calibrated in Co-60 and reported on absorbed dose in water per target dose (μGy/Gy) as well as thermal neutron dose equivalent per target dose (μSv/Gy). Additionally, bubble detectors for personal neutron dosimetry (BD-PND) were used for measuring neutrons (>50 keV), which were calibrated in a Cf-252 neutron beam to report on neutron dose equivalent dose data. The Monte Carlo code TOPAS (version 3.6) was run using a phase-space file containing 1010 histories reaching an average standard statistical uncertainty of less than 0.2% (coverage factor k = 1) on all voxels scoring more than 50% of the maximum dose. The primary beam was modeled following a Fermi-Eyges description of the spot envelope fitted to measurements. For the Monte Carlo simulation, the chemical composition of the tissues represented in ATOM was employed. The dose was tallied as dose-to-water, and data were normalized to the target dose (physical dose) to report on absorbed doses per target dose (mSv/Gy) or neutron dose equivalent per target dose (μSv/Gy), while also an estimate of the total organ dose was provided for a target dose of 50.4 Gy(RBE). Out-of-field doses showed absorbed doses that were 5 to 6 orders of magnitude lower than the target dose. The discrepancy between TLD data and the corresponding scored values in the Monte Carlo calculations involving proton and gamma contributions was on average 18%. The comparison between the neutron equivalent doses between the Monte Carlo simulation and the measured neutron doses was on average 8%. Organ dose calculations revealed the highest dose for the thyroid, which was 120 mSv, while other organ doses ranged from 18 mSv in the lungs to 0.6 mSv in the testes. The proposed computational method for routine calculation of the out-of-the-field dose in proton therapy produces results that are compatible with the experimental data and allow to calculate out-of-field organ doses during proton therapy.
dc.description.sponsorship The presented research has been funded by the HARMONIC project. The HARMONIC project (Health effects of cArdiac fluoRoscopy and MOderN radIotherapy in paediatriCs) has received funding from the Euratom research and training program 2014-2018 under grant agreement No 847707. MR acknowledges funding from the Sistema Nacional de Investigación de Panamá. IT-C acknowledges support from the Spanish Ministry of Science and Innovation and State Research Agency through the “Centro de Excelencia Severo Ochoa 2019-2023” Program (CEX2018-000806-S) and support from the Generalitat de Catalunya through the CERCA Program.
dc.format.mimetype application/pdf
dc.identifier.citation De Saint-Hubert M, Verbeek N, Bäumer C, Esser J, Wulff J, Nabha R, Van Hoey O, Dabin J, Stuckmann F, Vasi F, Radonic S, Boissonnat G, Schneider U, Rodriguez M, Timmermann B, Thierry-Chef I, Brualla L. Validation of a Monte Carlo framework for out-of-field dose calculations in proton therapy. Front Oncol. 2022 Jun 8;12:882489. DOI: 10.3389/fonc.2022.882489
dc.identifier.doi http://dx.doi.org/10.3389/fonc.2022.882489
dc.identifier.issn 2234-943X
dc.identifier.uri http://hdl.handle.net/10230/55074
dc.language.iso eng
dc.publisher Frontiers
dc.relation.ispartof Front Oncol. 2022 Jun 8;12:882489
dc.relation.projectID info:eu-repo/grantAgreement/EC/H2020/847707
dc.rights © 2022 De Saint-Hubert, Verbeek, Bäumer, Esser, Wulff, Nabha, Van Hoey, Dabin, Stuckmann, Vasi, Radonic, Boissonnat, Schneider, Rodriguez, Timmermann, Thierry-Chef and Brualla. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
dc.rights.accessRights info:eu-repo/semantics/openAccess
dc.rights.uri http://creativecommons.org/licenses/by/4.0/
dc.subject.keyword Monte Carlo simulation
dc.subject.keyword TLD
dc.subject.keyword Anthropomorphic pediatric phantom
dc.subject.keyword Bubble detector
dc.subject.keyword Out-of-field dosimetry
dc.subject.keyword Proton therapy
dc.title Validation of a Monte Carlo framework for out-of-field dose calculations in proton therapy
dc.type info:eu-repo/semantics/article
dc.type.version info:eu-repo/semantics/publishedVersion

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