Evaluacin dosimtrica de herramientas de ajuste fino del modelado de un haz de fotones de 6 MV para radioterapia / Dosimetric evaluation of fine tuning tools for the modelling of a 6 MV photon beam for radiotherapy

Cusis Castro, Tatiana C. (2023) Evaluacin dosimtrica de herramientas de ajuste fino del modelado de un haz de fotones de 6 MV para radioterapia / Dosimetric evaluation of fine tuning tools for the modelling of a 6 MV photon beam for radiotherapy. Master in Medical Physics, Universidad Nacional de Cuyo, Instituto Balseiro.

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Abstract in Spanish

El propsito de la planificacin de tratamientos en radioterapia es lograr la irradiacin del volumen blanco minimizando lo ms posible la dosis que reciben los rganos sanos. Por su parte, el control de calidad evala la correspondencia entre la dosis planificada y la que ser administrada al paciente. Para el diseo y clculo del plan de tratamiento se utilizan sistemas de planificacin conocidos como TPS, los cuales emplean un modelo de los haces de radiacin del equipo. Algunos TPS permiten la modificacin de parmetros especficos de dicho modelo para mejorar aun ms la correspondencia con el haz de radiacin. El objetivo de este trabajo es evaluar las herramientas de ajustes fino disponibles en el TPS Mnaco, denominadas Post modeling y su impacto dosimtrico sobre la planificacion de los tratamientos de radioterapia. En el desarrollo del presente trabajo se utilizan el acelerador lineal Elekta Synergy con colimador multilminas Agility, el TPS Mnaco, el detector planar MatriXX y el software de comparacin de dosis MyQA, disponibles en la Fundacin INTECNUS. Adems se utilizan los campos de irradiacin presentes en el paquete ExpressQA, proporcionados por el fabricante para el procedimiento de Post modeling. Se estudiaron cada uno de los parmetros modificables del MLC y su impacto en el clculo de los ocho campos del paquete ExpressQA. Se irradiaron dichos campos sobre el detector y se compar la medicin con el clculo utilizando la mtrica de ndice gamma 2 %2mm. Se disearon y analizaron ms de 200 modelos y se eligieron 2 de ellos como modelos ptimos. Adems, se estudi el comportamiento del detector y el impacto de su resolucin espacial en las mediciones, concluyendo que sera recomendable contar con un sistema de deteccin que presente mayor resolucin espacial. Finalmente, los modelos hallados fueron utilizados para recalcular planes de pacientes ya tratados en INTECNUS con diversas tcnicas. La variacin del porcentaje de pasaje del ndice gamma de los modelos ptimos respecto al original estuvo dentro del 2 %, cumpliendo en todos los casos la mtrica 3%3mm (criterio clnico). Se concluy que no es necesario modificar el modelado original utilizado en la institucin.

Abstract in English

The purpose of treatment planning in radiotherapy is to achieve irradiation of the target volume while minimizing the dose received by healthy organs as much as possible. Quality control, on the other hand, evaluates the correspondence between the planned dose and the dose that will be administered to the patient. Treatment planning systems, known as TPS, are used for the design and calculation of the treatment plan, which employ a model of the radiation beams from the equipment. Some TPS allow the modification of specific parameters of this model to further improve the correspondence with the radiation beam. The objective of this work is to evaluate the fine tuning tools available in TPS Monaco, called Post modeling, and their dosimetric impact on the planning of radiation therapy treatments. In the development of this work, the Elekta Synergy linear accelerator with Agility multileaf collimator, the TPS Monaco, the planar detector MatriXX, and the dose comparison software MyQA, available at the INTECNUS Foundation, are used. In addition, the irradiation fields present in the ExpressQA package provided by the manufacturer are used for the Post modeling procedure. Each of the modifiable parameters of the MLC and their impact on the calculation of the eight fields in the ExpressQA package were studied. These fields were irradiated onto the detector and the measurement was compared with the calculation using the gamma index metric 2%2mm. More than 200 models were designed and analyzed, and 2 of them were chosen as optimal models. Furthermore, the behavior of the detector and the impact of its spatial resolution on the measurements were studied, concluding that it would be advisable to have a detection system with higher spatial resolution. Finally, the found models were used to recalculate plans for patients who had already been treated at INTECNUS with different techniques. The variation in the percentage of gamma index passage for the optimal models in comparison to the original was within 2%, meeting the 3%3mm metric (clinical criteria) in all cases. It was concluded that it is not necessary to modify the original modeling used in the institution.

Item Type:Thesis (Master in Medical Physics)
Keywords:Radiotherapy; Radioterapia; Photon beams; Haces de fotones; [Modelling; Modelado; Post modelling; Synergy accelerator; Acelerador Synergy; Gamma index; Mtrica ndice gamma]
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Subjects:Medicine > Radiotherapy
Divisions:Centro Integral de Medicina Nuclear y Radioterapia. Fundacin INTECNUS
ID Code:1233
Deposited By:Marisa G. Velazco Aldao
Deposited On:15 Apr 2024 15:00
Last Modified:15 Apr 2024 15:00

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