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Doctoral Thesis
Full name
Luciana Caminha Afonso
Knowledge Area
Date of Defense
São Paulo, 2011
Caldas, Linda Viola Ehlin (President)
Costa, Paulo Roberto
Hamada, Margarida Mizue
Nersissian, Denise Yanikian
Potiens, Maria da Penha Albuquerque
Title in Portuguese
Estudo da influência de partículas de ouro na dose absorvida em tecido mole utilizando dosimetria com gel polimérico
Keywords in Portuguese
aumento de dose
gel polimérico
Abstract in Portuguese
A presença de material de alto número atômico adjacente ao tecido mole aumenta localmente a dose absorvida pelo tecido quando submetido à radiação. Este efeito ocorre devido aos fotoelétrons ejetados do material de alto número atômico. Dosímetros de gel polimérico com partículas de ouro foram utilizados para investigar este efeito. Foram realizados cálculos analíticos para estimar o aumento de dose e simulações com o método de Monte Carlo. A irradiação de amostras de gel polimérico (GP) puro e com 0,005 gAu/gGP utilizando um feixe de raios X produzido por um potencial de 150 kV filtrado com 4 mmAl e 5 mmCu resultou em uma dose absorvida pelas amostras com ouro aproximadamente 20% maior que a dose absorvida pelas amostras de gel polimérico puro. Os cálculos analíticos e a simulação com o método de Monte Carlo resultaram em um aumento de aproximadamente 30% na dose absorvida.
Title in English
Study of the influence of gold particles on the absorbed dose in soft tissue using polymer gel dosimetry
Keywords in English
dose enhancement
polymer gel
radiation therapy
Abstract in English
The presence of high-Z material adjacent to soft tissue, when submitted to irradiation, enhances locally the absorbed dose in these soft tissues. Such effect occurs due to the outscattering of photoelectrons from the high-Z material. Polymer gel dosimeters have been used to investigate this effect. Analytic calculations to estimate the dose enhancement and Monte Carlo simulations have been performed. Samples containing polymer gel (PG) with 0.005 gAu/gPG and pure polymer gel have been irradiated using an X-rays beam produced by 150 kV, filtered with 4 mm Al and 5 mm Cu, which resulted in an approximately 20% higher absorbed dose in the samples with gold in comparison to those with pure polymer gel. The analytic calculations and the Monte Carlo simulation resulted in a dose enhancement factor of approximately 30%.
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