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Authors
Advisor(s)
Abstract(s)
Procedimentos em radioterapia visam alcançar a entrega de dose com alta exatidão. Este trabalho aborda algumas considerações sobre incertezas associadas a erros sistemáticos e aleatórios em tratamentos com radioterapia conformacional de câncer de próstata que podem comprometer a entrega de dose prescrita no planeamento. Sugestões sobre como minimizar as incertezas são apresentadas nos relatórios e diretrizes da Agência Internacional de Energia Atómica (IAEA), Comissão Internacional de Unidades e Medidas Radiológicas (ICRU) e o Instituto Britânico de Radiologia (BIR), tais sugestões são amplamente discutidas e confrontadas com observações clínicas em tratamento radioterápico. Os erros geométricos e incertezas estão intimamente relacionados com a dose de radiação fornecida ao paciente. Portanto, a descoberta de margens ideais de CTV-PTV permite uma maior exatidão em entrega de dose ao tumor e preserva os órgãos circundantes os quais são altamente sensíveis à radiação. Para o entendimento dos fundamentos relacionados à sobre e subdosagem em tratamento radioterápico de câncer de próstata, deve-se levar em consideração a mudança de forma geométrica relativa às variações anatômicas do volume tratado (TV) e dos órgãos em risco (OAR). Assim como a precisão das técnicas de delineamento de CTV-PTV tal qual o uso de portal de imagem, por exemplo. Todas essas intervenções possibilitam a precisão na identificação das margens de CTV-PTV para o maximização de entrega de dose prescrita. Neste ínterim, os métodos para o cálculo de margens desenvolvidas pelo BIR e van Herk são abordados, além da discussão acerca de um estudo onde aqueles métodos foram empregados e aplicados clinicamente. Os resultados indicam uma exatidão na entrega de dose que está abaixo de 2%, valor menor que o limite de ±5% sugerido pelos relatórios das agências internacionais.
ABSTRACT - The procedures in radiotherapy aim to achieve high accuracy on dose delivery. This work covers some considerations about systematic and random errors besides the related uncertainties in prostate cancer treatments performed in conformal radiotherapy treatment which can compromise the dose delivery in the planning. Suggestions about minimizing the uncertainties are presented in reports and guidelines of the International Atomic Energy Agency (IAEA), International Commission on Radiation Units and Measurements (ICRU), and The British Institute of Radiology (BIR), they are widely discussed and confronted to clinical observations inside the radiotherapy treatment. Those geometric errors and uncertainties are closely related to the dose delivered to the patient. The find of the optimal CTV-PTV margins allows a better accuracy of dose delivery on the tumor and spare the surrounding high radio-sensitive organs. For the understanding of roots related to over and under-dosing in the prostate cancer radiotherapy treatment, the change of the geometrical shape due to the anatomical variations of the treated volume (TV) and the organ at risk (OAR) must be taken into account. As well as the precise CTV-PTV delineation techniques like the use of the portal of the image, for instance. All those interventions possibilities the accuracy of identifying the CTV-PTV margins for the maximum delivery of the prescribed dose. In the meantime, both BIR and van Herk margins recipes are covered, therefore a study where those methods were applied clinically and analyzed were discussed. The results indicate the dose delivery of less than 2% that is inside the limit of ±5%, which is in compliance with international reports.
ABSTRACT - The procedures in radiotherapy aim to achieve high accuracy on dose delivery. This work covers some considerations about systematic and random errors besides the related uncertainties in prostate cancer treatments performed in conformal radiotherapy treatment which can compromise the dose delivery in the planning. Suggestions about minimizing the uncertainties are presented in reports and guidelines of the International Atomic Energy Agency (IAEA), International Commission on Radiation Units and Measurements (ICRU), and The British Institute of Radiology (BIR), they are widely discussed and confronted to clinical observations inside the radiotherapy treatment. Those geometric errors and uncertainties are closely related to the dose delivered to the patient. The find of the optimal CTV-PTV margins allows a better accuracy of dose delivery on the tumor and spare the surrounding high radio-sensitive organs. For the understanding of roots related to over and under-dosing in the prostate cancer radiotherapy treatment, the change of the geometrical shape due to the anatomical variations of the treated volume (TV) and the organ at risk (OAR) must be taken into account. As well as the precise CTV-PTV delineation techniques like the use of the portal of the image, for instance. All those interventions possibilities the accuracy of identifying the CTV-PTV margins for the maximum delivery of the prescribed dose. In the meantime, both BIR and van Herk margins recipes are covered, therefore a study where those methods were applied clinically and analyzed were discussed. The results indicate the dose delivery of less than 2% that is inside the limit of ±5%, which is in compliance with international reports.
Description
Master in Radiation Applied to Health Technologies. - Specialization area: Digital Imaging Technologies.
Keywords
Radioterapia Dosimetria Cancro da próstata Segurança do doente Radiotherapy Dosimetry Prostate cancer Patient safety
Citation
Assis MJ. Geometric uncertainties in prostate cancer radiotherapy treatments [dissertation]. Lisboa: Escola Superior de Tecnologia da Saúde de Lisboa/Instituto Politécnico de Lisboa; 2019.
Publisher
Instituto Politécnico de Lisboa, Escola Superior de Tecnologia da Saúde de Lisboa