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Master's Dissertation
DOI
10.11606/D.43.1987.tde-28022014-144037
Document
Author
Full name
Martha Aurelia Aldred
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 1987
Supervisor
Committee
Watanabe, Shigueo (President)
Dias Neto, Alipio Luiz
Robilotta, Cecil Chow
Title in Portuguese
Estudo "in vivo" da influência de heterogeneidade de tecidos na distribuição de dose em terapias com raios x de alta energia
Keywords in Portuguese
Dosimetria TL
Heterogeneidade de tecidos
Medidas \"in vivo\"
Radioterapia
Abstract in Portuguese
O estudo dos efeitos da heterogeneidade de tecidos nas doses administradas em radioterapia tem sido alvo de diversos trabalhos. A maioria deles mostra medidas "in vitro" em fantomas homogêneos nos quais são introduzidos materiais que simulam a presença de ossos ou de cavidades de ar. No presente trabalho optou-se por um estudo "in vivo" para o qual utilizou-se como instrumento de medida a dosimetria termoluminescente, bastante apropriada por motivos bem conhecidos. Foram escolhidos oito pacientes com tumor na região pélvica, tratados com raios x do Acelerador Linear de 4 MeV do Instituto de Radioterapia Osvaldo Cruz. A relação entre as doses medidas na entrada e na saída do feixe quando comparada ao valor previsto para fantomas homogêneos, indica a influência da heterogeneidade na distribuição da dose. A análise das medidas efetuadas nos oito pacientes, mostrou que a dose administrada ao centro do tumor pode ser 8% menor do que aquela planejada sem levar-se em conta a referida heterogeneidade.
Title in English
In vivo study of the influence of tissue inhomogeneity on dose distribution in high energy X ray therapy
Keywords in English
Radiotherapy
Tissue heterogeneity
TL dosimetry
\"In vivo\" measures
Abstract in English
Several authors investigated the effect of the heterogeneity of tissue in the dose distribution in a radiation therapy. Practically all of them carried out "in vitro" measurements using a solid body immersed in a water phantom, in order to simulate the inhomogeneity, such as bone, air cavity, etc. In the present work, "in vivo" measurements were performed utilizing thermoluminescent dosimeters, whose appropriateness and convenience are well known. Eight patients at Instituto de Radioterapia Oswaldo Cruz were selected, that were under irradiation treatments in their pelvic region. The ratio between body entry radiation dose and the corresponding exit dose, when compared to the same ratio for a homogeneous phantom, gives the influence of the heterogeneity of the tissue the radiation crosses. The results found in those eight patients have shown that "in vivo" measurements present a ratio about 8% smaller than in homogenous phantom case.
 
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Publishing Date
2014-02-28
 
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