A simple method to back-project isocenter dose of radiotherapy treatments using EPID transit dosimetry

Autores

  • Thiago Bernardino da Silveira Instituto Nacional de Câncer e Instituto de Radioproteção e Dosimetria ,
  • Bianca de Quadros Cerbaro Instituto de Radioproteção e Dosimetria image/svg+xml
  • Luiz Antônio Ribeiro da Rosa Instituto de Radioproteção e Dosimetria image/svg+xml

DOI:

https://doi.org/10.15392/bjrs.v5i3.319

Palavras-chave:

EPID, portal dosimetry, transit dosimetry, radiotherapy

Resumo

The aim of this work was to implement a simple algorithm to evaluate isocenter dose in a phantom using the back-projected transmitted dose acquired using an Electronic Portal Imaging Device (EPID) available in a Varian Trilogy accelerator with two nominal 6 and 10 MV photon beams. This algorithm was developed in MATLAB language, to calibrate EPID measured dose in absolute dose, using a deconvolution process, and to incorporate all scattering and attenuation contributions due to photon interactions with phantom. Modeling process was simplified by using empirical curve adjustments to describe the contribution of scattering and attenuation effects. The implemented algorithm and method were validated employing 19 patient treatment plans with 104 clinical irradiation fields projected on the phantom used. Results for EPID absolute dose calibration by deconvolution have showed percent deviations lower than 1%. Final method validation presented average percent deviations between isocenter doses calculated by back-projection and isocenter doses determined with ionization chamber of 1,86% (SD of 1,00%) and -0,94% (SD of 0,61%) for 6 and 10 MV, respectively. Normalized field by field analysis showed deviations smaller than 2% for 89% of all data for 6 MV beams and 94% for 10 MV beams. It was concluded that the proposed algorithm possesses sufficient accuracy to be used for in vivo dosimetry, being sensitive to detect dose delivery errors bigger than 3-4% for conformal and intensity modulated radiation therapy techniques.

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Referências

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Publicado

19-10-2017

Edição

v. 5 n. 3 (2017)

Seção

Artigos

Licença

Declaro que o presente artigo é original, não tendo sido submetido à publicação em qualquer outro periódico nacional ou internacional, quer seja em parte ou em sua totalidade. Declaro, ainda, que uma vez publicado na revista Brazilian Journal of Radiation Sciences, editada pela Sociedade Brasileira de Proteção Radiológica, o mesmo jamais será submetido por mim ou por qualquer um dos demais co-autores a qualquer outro periódico. Através deste instrumento, em meu nome e em nome dos demais co-autores, porventura existentes, cedo os direitos autorais do referido artigo à Sociedade Brasileira de Proteção Radiológica, que está autorizada a publicá-lo em meio impresso, digital, ou outro existente, sem retribuição financeira para os autores.

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Como Citar

A simple method to back-project isocenter dose of radiotherapy treatments using EPID transit dosimetry. Brazilian Journal of Radiation Sciences, Rio de Janeiro, Brazil, v. 5, n. 3, 2017. DOI: 10.15392/bjrs.v5i3.319. Disponível em: https://bjrs.org.br/revista/index.php/REVISTA/article/view/319. Acesso em: 18 jul. 2025.