Spretz, Tomás Emanuel (2016) Dosimetría de campos pequeños de fotones en radioterapia. Intercomparación entre distintos detectores. / Small fields dosimetry of radiotherapy photon beams. Maestría en Física Médica, Universidad Nacional de Cuyo, Instituto Balseiro.
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Resumen en español
Se entiende que un haz de fotones conforma un Campo Pequeño cuando no se logra el equilibrio lateral de partículas cargadas. Esto implica que no se satisfacen las condiciones exigidas por la teoría de dosimetría para establecer una relación entre ionización y dosis. El presente trabajo tiene como objetivos comprender los conceptos básicos ligados a los campos pequeños, conocer tecnologías empleadas para su dosimetría, realizar mediciones en haces de fotones con distintos detectores, y analizar los resultados obtenidos. Para ello, se emplearon dos detectores tipo diodo, un detector de diamante sintético, una micro-cámara de ionización y una cámara de ionización de propósito general. Se midieron factores de campo, perfiles de dosis y curvas de dosis en profundidad. En el primer caso, los cocientes de lecturas debieron ser afectados por factores de corrección, de acuerdo a lo especificado en el formalismo presentado por Alfonso et al. Se verificó que a los detectores de estado sólido deben aplicarse las menores correcciones. En el caso de perfiles de dosis, se observaron los efectos de volumen parcial y de oclusión de la fuente de fotones. Las curvas de dosis en profundidad también son afectadas por el volumen del detector. Los mejores resultados fueron obtenidos con el diodo de encapsulado más pequeño.
Resumen en inglés
A photon beam establishes a Small Field when lateral charged particle equilibrium is not reached. Under such situation, the conditions required by the dosimetry theory to relate ionization to dose, are not satisfied. The goal of the present work is to understand the basic concepts linked to small fields, to know technologies used for its dosimetry, to make beam measurements with different detectors and to analyze the results. Two different diodes, a diamond detector, a micro-ionization chamber and a conventional ionization chamber were used. Measurements of output factors, dose profiles, and percent-depth dose curves were performed. In the case of the output factors, the ratios of detector readings were multiplied by correction factors, as specified by Alfonso et al. It was verified that solid-state detectors need the smallest corrections. In the case of dose profiles, both volume-averaging and photon source occlusion effects were observed. Percent depth dose curves are affected by detector volume averaging too. The best results were obtained with the diode which has the smallest housing.
| Tipo de objeto: | Tesis (Maestría en Física Médica) |
|---|---|
| Palabras Clave: | Dosimetry; Dosimetría; Diamonds; Diamantes; Radiation detectors; Detectores de radiaciones; Photons; Fotones [Small field; Campo pequeño] |
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| Materias: | Medicina > Dosimetría |
| Divisiones: | Fundación Centro de Medicina Nuclear y Molecular de Entre Ríos |
| Código ID: | 578 |
| Depositado Por: | Tamara Cárcamo |
| Depositado En: | 19 Abr 2017 17:40 |
| Última Modificación: | 24 Abr 2017 17:08 |
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