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Authors
Advisor(s)
Abstract(s)
A radioterapia estereotáxica (SBRT) tem mostrado bons resultados no tratamento do cancro do pulmão. O movimento respiratório dos órgãos depende do doente, da posição dos braços e da imobilização. Esta pode ser feita com ou sem a ajuda de acessórios como o compressor abdominal que quando os tumores são localizados nos lobos inferiores e perto do diafragma se torna vantajoso, mas se for colocado com elevada pressão pode aumentar o movimento respiratório. O posicionamento sem acessórios rigidos de imobilização deve ser acompanhado de imagens diárias para minimizar os erros de set-up e ter uma elevada precisão no volume a irradiar. O objectivo deste estudo é fazer uma avaliação dosimétrica de planeamentos de SBRT com arcoterapia volumétrica de intensidade modulada (VMAT) em dois posicionamentos diferentes: braços para cima e braços ao longo do corpo. Numa amostra de quatro doentes, para cada posicionamento foram adquiridas imagens de Tomografia Computorizada (TC) e imagens de quarto Dimensões de Tomografia Computorizada (4DCT) e tendo sido foi feita uma reconstrução mid-ventilation. Foram estudadas várias variáveis, entre as quais, volumes e doses para os volumes-alvo e órgãos de risco e unidades monitor. Não foram encontradas diferenças significativas entre as variáveis estudadas. Podendo concluir-se que o posicionamento do doente deve ser escolhido de acordo com as suas dificuldades, devendo ser confortável, estável e reprodutível. Em alguns casos, e em doentes em que o movimento respiratório seja de grande amplitude, o posicionamento com os braços ao longo do corpo pode ter a vantagem de diminuir o movimento respiratório e consequentemente o volume alvo interno (ITV).
ABSTRACT - Stereotactic Body Radiation Therapy (SBRT) has been shown good results in lung cancer patients. Respiratory motion of internal organs depends on patient, arms position and the type of immobilization devices used. For patient immobilization can be used rigid fixation devices or not. Abdominal compression can be advantageous for lung tumors in lower lobe or close to diaphragm, but if placed with too much pressure it can increase tumor motion and target volume. Without rigid fixation devices daily images are important to minimize set up errors and have high precision in the irradiated volume. The aim of this study is to evaluate dosimetric SBRT plans with Volumetric Modulated Arc Therapy (VMAT) in different positions: arms up and arms down. Four SBRT lung cancer patients were included in the sample. A Computed Tomography (CT) and a four-Dimensional Computed Tomography (4DCT) was acquired and a mid-ventilation was reconstructed. The analyzed variables were volumes, doses – targets and oragans at risk – and total of monitor units (the sum of all arcs). No statistically significant differences were found between the studied variables. Patient position should be chosen according to patients’ difficulties and comfort in order to make a comfortable, stable and reproducible position. In patients with a large respiratory motion amplitude, position with arms down can have advantages because respiratory motion decreases, decreasing the margins for internal target volume (ITV).
ABSTRACT - Stereotactic Body Radiation Therapy (SBRT) has been shown good results in lung cancer patients. Respiratory motion of internal organs depends on patient, arms position and the type of immobilization devices used. For patient immobilization can be used rigid fixation devices or not. Abdominal compression can be advantageous for lung tumors in lower lobe or close to diaphragm, but if placed with too much pressure it can increase tumor motion and target volume. Without rigid fixation devices daily images are important to minimize set up errors and have high precision in the irradiated volume. The aim of this study is to evaluate dosimetric SBRT plans with Volumetric Modulated Arc Therapy (VMAT) in different positions: arms up and arms down. Four SBRT lung cancer patients were included in the sample. A Computed Tomography (CT) and a four-Dimensional Computed Tomography (4DCT) was acquired and a mid-ventilation was reconstructed. The analyzed variables were volumes, doses – targets and oragans at risk – and total of monitor units (the sum of all arcs). No statistically significant differences were found between the studied variables. Patient position should be chosen according to patients’ difficulties and comfort in order to make a comfortable, stable and reproducible position. In patients with a large respiratory motion amplitude, position with arms down can have advantages because respiratory motion decreases, decreasing the margins for internal target volume (ITV).
Description
Mestrado em Radiações Aplicadas às Tecnologias da Saúde - Ramo de especialização: Terapia com Radiações
Keywords
Radioterapia Radioterapia esterotáxica Cancro do pulmão Imobilização Posicionamento Radiotherapy SBRT Lung cancer Immobilization Patient position
Citation
Barreira CS. Stereotactic body radiation therapy in lung cancer patient positioning: arms up vs. arms down (a dosimetric evaluation) [Dissertation]. Lisboa: Escola Superior de Tecnologia da Saúde de Lisboa/Instituto Politécnico de Lisboa; 2016.
Publisher
Instituto Politécnico de Lisboa, Escola Superior de Tecnologia da Saúde de Lisboa