The use of tetrahedral mesh geometries in Monte Carlo simulation of applicator based brachytherapy dose distributions

Autor(es)

Fonseca, Gabriel Paiva ^{[1, 2]} ; Landry, Guillaume ^{[2, 3]} ; White, Shane ^[2] ; D'Amours, Michel ^{[4, 5, 6, 7]} ; Yoriyaz, Helio ^[1] ; Beaulieu, Luc ^{[4, 5, 6, 7]} ; Reniers, Brigitte ^{[8, 2]} ; Verhaegen, Frank ^{[2, 9]}

Afiliação do(s) autor(es)

^[1] Inst Pesquisas Energet & Nucl IPEN CNEN SP, Sao Paulo - Brazil

^[2] Maastricht Univ, Med Ctr, GROW Sch Oncol & Dev Biol, Dept Radiat Oncol MAASTRO, Maastricht - Netherlands

^[3] Univ Munich, Fac Phys, Dept Med Phys, Munich - Germany

^[4] Univ Laval, Dept Phys Genie Phys & Opt, Quebec City, PQ - Canada

^[5] CHU Quebec, Dept Radiooncol, Quebec City, PQ - Canada

^[6] CHU Quebec, Ctr Rech, Quebec City, PQ - Canada

^[7] Univ Laval, Ctr Rech Cancerol, Quebec City, PQ - Canada

^[8] Hasselt Univ, CMK, Res Grp NuTeC, B-3590 Diepenbeek - Belgium

^[9] McGill Univ, Med Phys Unit, Montreal, PQ - Canada

• Tipo de documento: Artigo Científico
• Fonte: Physics in Medicine and Biology; v. 59, n. 19, p. 5921-5935, OCT 7 2014.
• Citações Web of Science: 4

Resumo

Accounting for brachytherapy applicator attenuation is part of the recommendations from the recent report of AAPM Task Group 186. To do so, model based dose calculation algorithms require accurate modelling of the applicator geometry. This can be non-trivial in the case of irregularly shaped applicators such as the Fletcher Williamson gynaecological applicator or balloon applicators with possibly irregular shapes employed in accelerated partial breast irradiation (APBI) performed using electronic brachytherapy sources (EBS). While many of these applicators can be modelled using constructive solid geometry (CSG), the latter may be difficult and time-consuming. Alternatively, these complex geometries can be modelled using tessellated geometries such as tetrahedral meshes (mesh geometries (MG)). Recent versions of Monte Carlo (MC) codes Geant4 and MCNP6 allow for the use of MG. The goal of this work was to model a series of applicators relevant to brachytherapy using MG. Applicators designed for Ir-192 sources and 50 kV EBS were studied; a shielded vaginal applicator, a shielded Fletcher Williamson applicator and an APBI balloon applicator. All applicators were modelled in Geant4 and MCNP6 using MG and CSG for dose calculations. CSG derived dose distributions were considered as reference and used to validate MG models by comparing dose distribution ratios. In general agreement within 1% for the dose calculations was observed for all applicators between MG and CSG and between codes when considering volumes inside the 25% isodose surface. When compared to CSG, MG required longer computation times by a factor of at least 2 for MC simulations using the same code. MCNP6 calculation times were more than ten times shorter than Geant4 in some cases. In conclusion we presented methods allowing for high fidelity modelling with results equivalent to CSG. To the best of our knowledge MG offers the most accurate representation of an irregular APBI balloon applicator. (AU)

• Processo FAPESP: 11/22778-8 - Dosimetria 3D baseada em imagens médicas e códigos de Monte Carlo com aplicação em braquiterapia
• Beneficiário: Hélio Yoriyaz
• Modalidade de apoio: Auxílio à Pesquisa - Regular
• Processo FAPESP: 11/23765-7 - Comparação e análise de sistemas de planejamento de tratamento para braquiterapia 3D, utilizando o mcnp5, brachyvision e nucletron
• Beneficiário: Gabriel Paiva Fonseca
• Modalidade de apoio: Bolsas no Exterior - Estágio de Pesquisa - Doutorado
• Processo FAPESP: 11/01913-4 - Modelagem pelo método de Monte Carlo do paciente e das complexidades dos tratamentos braquiterápicos com alta taxa de dose
• Beneficiário: Gabriel Paiva Fonseca
• Modalidade de apoio: Bolsas no Brasil - Doutorado