Wedged beam are often used in clinical radiotherapy to compensate missing tissues and dose gradients. In this work, the Fricke Xylenol Gel (FXG) dosimeter was used for 6 MV photons radiation wedge field profiles measurements, allowing to infer the wedge filter physical attenuation coefficient. This dosimeter is a chemical system of a Fe3+-Xylenol complex concentration, that when measured spectrophotometrically, the absorbance is directly proportional to the absorbed dose. From theses results one can infer that the FXG can be used also as an alternative dosimetric system for measurements of wedge filters.

The Fricke dosimeter is a ferrous sulfate aqueous solution that, when irradiated, oxidizes the Fe2 + ions to Fe3 + . This new concentration, generally determined through spectrophotometry, is directly proportional to the ionizing radiation absorbed energy. The Fricke Xylenol Gel dosimeter (FXG) was developed through the incorporation of swine skin gelatin and xylenol orange. These modifications provided better signal stability and sensitivity for lower absorbed dose measurements, such as those used in radiotherapy. In this work FXG samples were irradiated with absorbed doses of 2 Gy, from 6 MV and 10 MV photons, using small field sizes geometry for dosimetric parameters determination. All the FXG dosimeter readings were accomplished with our specially developed spectrophotometer, using a narrow light beam at the wavelength of 585 nm, where the highest absorbance sensitivity occurs. From our results, we can confirm not only that the FXG dosimetric system (FXG plus a high lateral spatial resolution spectrophotometer) can be used for general dosimetry, but as well for small field size dosimetry of interest in radiosurgery.

The polymers Tetrafluoroethylene- hexa- fluoropropylene (FEP) and Tetrafluoroethylene- per- fluoromethoxyethelene (PFA) are normally used as anti-adherent coatings and can also be applied for several applications in research. For example, they can be used as radiation dosimeters for X-ray and gamma photons, electrons, protons and other ionazing particles. In order to determine radiation induced damage, that can compromise applications in dosimetry, FEP and PFA films were bombarded with protons of 1 MeV at fluences from 1 × 10(11) protons/cm² to 1 × 10(16) protons/cm². During the bombardment, the chemical species emission was monitored with a Residual Gas Analyzer (RGA), and results show that the CF3 radical is the specie preferentially emitted. The bombarded films were also analyzed with Optical Absorption Photospectrometry (OAP) which shows quantitative chemically specific evidence of the damage caused by the proton bombardment. Our results show that damage to polymers is detectable for all fluences used in this work, but damage that can compromise applications in dosimetry occurs only for fluences greater than 1 × 10(14) protons/cm².

Considerando a importância da garantia da qualidade nos serviços de radioterapia, este trabalho tem como primeiro objetivo fazer uma avaliação dos testes propostos pelos protocolos oficiais internacionais TG40 e ARCAL XXX para os equipamentos de cobalto, acelerador linear e simulador. O segundo objetivo consistiu em se fazer uma avaliação dos testes que atualmente são realizados por alguns serviços de radioterapia nacionais e da América Latina, comparando-os com os apresentados nos protocolos citados. Dos resultados obtidos, observou-se que embora o TG40 apresente os testes básicos necessários para um controle de qualidade adequado, o ARCAL ainda sugere testes complementares. Dos resultados e discussões, concluiu-se que é necessário que os serviços de radioterapia implementem os testes de controle de qualidade básicos e indispensáveis aos seus equipamentos, e que os demais testes sejam implementados de acordo com as suas necessidades e disponibilidades. Como produto deste estudo, sugestões de protocolos são apresentadas para o trabalho de rotina, provenientes da fusão dos protocolos analisados.

In view of the great importance of quality control in radiotherapy services, this paper aimed primarily to evaluate the tests recommended by international protocols TG40 and ARCAL XXX for teletherapic equipments (cobalt, linear accelerator and simulator). A second objective was to evaluate the tests currently used in some radiotherapy services in Brazil and Latin America and to compare these tests with the ones recommended by the international protocols. Our results suggest that ARCAL is more complete than TG40, although the latter includes all the essential basic tests. We concluded that radiotherapy services should implement all basic quality control tests and that all other complementary tests should be implemented according to the need of each service. Finally, suggestions of protocols are presented, elaborated from the official and routine protocols used.

A braquiterapia por alta taxa de dose está recebendo atenção considerável na maioria dos países. Por isso, nos serviços que utilizam este equipamento exige-se que o desenvolvimento de um programa de controle de qualidade seja cada vez mais rigoroso, para garantir não apenas a segurança aos pacientes, mas também aos operadores e demais envolvidos. Este trabalho tem por objetivos fazer um levantamento dos tipos de testes para um equipamento de braquiterapia por alta taxa de dose, propostos pelos protocolos oficiais publicados (TG40, TG56 e ARCAL XXX) e avaliar os tipos de testes que atualmente são realizados por alguns serviços de radioterapia, comparando-os com aqueles apresentados nos protocolos citados. Das análises feitas, observou-se que: a) quanto aos protocolos oficiais, o TG56 é mais completo que o TG40 e o ARCAL XXX; b) quanto às instituições analisadas, estas em geral se basearam no TG56 para elaborar seus próprios protocolos, os quais demonstraram ter também concordância com os outros já citados. Nestes protocolos, a inexistência dos testes anuais foi notada, o que pode ser explicado por sua aparição nas freqüências trimestral e semestral. Do produto deste estudo são apresentadas tabelas dos tipos de testes com suas respectivas freqüências de utilização, das quais um protocolo pode ser inferido para auxiliar na implementação, pelo menos, dos tipos de testes de controle de qualidade básicos e indispensáveis para o equipamento, garantindo, assim, um tratamento adequado aos pacientes e uma melhor segurança ao pessoal envolvido e, conseqüentemente, assegurando a garantia de qualidade na braquiterapia por alta taxa de dose.

High dose rate brachytherapy has been increasingly recognized in most countries, and radiotherapy services using this equipment are encouraged to have a very efficient quality assurance program to ensure protection for patients, workers and other personnel involved. The objective of this paper was to determine the types of tests for high dose rate equipment required by official protocols (TG40, TG56 and ARCAL XXX) and to compare them with the types of tests utilized by some radiotherapy services. We concluded that: a) the protocol TG56 is more extensive and complete than the other official protocols (TG40 and ARCAL XXX); b) the protocols used by the services evaluated on this study were based on the protocol TG56, and were concordant with the other official protocols. In these protocols annual tests were frequently replaced by tests performed quarterly or twice a year. This study established the types of test used and their frequency of utilization, and permitted the design of an optimized protocol that may help in the implementation of basic and indispensable tests in order to ensure patient adequate treatment and safety to personnel involved, and consequently improve high dose rate brachytherapy quality assurance.