Avaliação de dosímetro orgânico inteligente para aplicação em radioterapia.

Atualmente, o uso inapropriado e incorreto dos aceleradores lineares em radioterapia, ou seja, sem as condições necessárias para tratamentos oncológicos eficientes, tem sido alvo de crítica da impressa escrita e também da literatura médica. Nesse trabalho é apresentado o projeto, a fabricação e o desempenho de novos sensores à base do poli[2-metóxi-5-(2’-etilhexilóxi)-1,4-fenilenovinileno] e do Tris-(8-hidroxiquinolinolato) de alumínio (III) – Alq3 (MEH-PPV/Alq3) para detecção de doses de raios X (6 MeV) visando tanto o acompanhamento de tratamentos oncológicos, quanto a calibração da radiação fornecida por aceleradores lineares. Tal dispositivo de baixo custo (< R$1), denominado de “semároforo inteligente”, baseia-se no uso de uma única solução do material híbrido e apresenta variação irreversível de cor induzida pela radiação do vermelho ao amarelo, e depois a verde, para doses entre 0 a 40 Gy. Uma série de ensaios foi realizada para avaliar as curvas de resposta dose-cor, a sensibilidade, a reprodutibilidade e a estabilidade dos dispositivos fabricados a partir de diagramas de cromaticidade e de medidas de espectroscopia de absorção e de fluorescência do material híbrido exposto a diferentes doses e isodoses de radiação em phanton de água. Os resultados obtidos mostraram que o sensor apresenta curvas dose-cor dependentes da composição química do material híbrido, resposta em tempo real, linearidade e boa estabilidade. Finalmente, as resposta quantitativas e qualitativas do sensor foram investigadas com o auxílio de um dispositivo eletrônico, tipo colorímetro, que permitiu, dentre outras vantagens, correlacionar facilmente a cor emitida pela solução orgânica com a dose de radiação prescrita pelo acelerador.Nowadays, the inappropriate use of linear accelerators in radiotherapy, i.e. without the necessary conditions for effective cancer treatments, has been the target of criticism from press releases and also the medical literature. We report on design, fabrication and performance of a novel Alq3/MEH-PPV x-rays dose detector for radiation therapy in the management of cancer using linear accelerators (6 MeV). The detector consists of an irreversible color-changing from red to yellow, and then to green, low cost (< US$ 0.50 for each sensor unit) and accumulated organic device, denoted here as “traffic light device”, to measure the delivered dose from the radiation beams of linear accelerator in the range of 0 and 40 Gy by using a single sample solution and a colorimetric system. A series of test were conducted to evaluate the accuracy and precision of organic detector in measuring dose and depth-dose distribution of photon beans in a water phantom, and the ability to alter the dose-response curve of such device by manipulating the chemical composition of the hybrid material. The results showed that the device presents real time response, good stability and sensibility. We also discuss the sensibility of the optimized detector and the description of inexpensive handheld colorimeter that generates quantitative and qualitative data in point-of-care analytical system for linear accelerator equipments

Fabrication of organic and flexible sensor for aplication in blue-light therapy.

A fototerapia com luz azul (460 nm - 490 nm) é o procedimento mais utilizado para o tratamento da icterícia em recém-nascidos. Contudo, dois fatores alteraram drasticamente a eficiência desse tratamento: (1) o espectro da fonte luminosa e (2) a dose de radiação absorvida pelos neonatos. Este trabalho apresenta o desenvolvimento de detectores de radiação orgânicos e flexíveis, de baixo custo, de bom desempenho e de fácil operação para monitoramento da radiação incidente em neonatos ictéricos sob tratamento fototerápico. O princípio de funcionamento dos dispositivos baseia-se na resposta óptica de filmes finos à base de dois materiais orgânicos luminescentes: o tris (8-hidroxiquinolinato de alumínio) - Alq3 e o poli[2-metóxi-5-(2’-etilóxi)-p-fenilenovinileno] - MEH-PPV, dispersos em matriz de poliestireno – PS sob efeito de luz azul. Os resultados obtidos mostram que a radiação atua no sentido de alterar a intensidade de máxima emissão do vermelho ao verde, passando pelo amarelo, dos filmes de PS/MEH-PPV/Alq3. Esse resultado é atribuído à fotodegradação do MEH-PPV e, consequentemente, as mudanças na sobreposição entre os espectros de emissão do Alq3 e de absorção desse polímero. A resposta óptica dos filmes com a radiação foi usada para fabricar um sensor orgânico flexível, inédito e de custo inferior a R$0,50, para controle das condições de exposição de neonatos ictéricos à fototerapia com luz azul.Blue-light therapy (460 nm - 490 nm) is the most common treatment of jaundice in newborns. However, the efficiency of this treatment is dependent of two factors: (1) the spectrum of light source and (2) the delivered dose to the neonates. This work presents the development of a low-cost, flexible, good performance and an easy detector operation based on organic materials for evaluation of radiation dose delivered by the phototherapy units to jaundice newborns. The operation principles of the device is based on the optical response of poly [2-methoxy-5-(2’-ethylhexyloxy)-p-phenylene - MEH-PPV, tris (8-hydroxyquinolinato aluminum)-Alq3 and polystyrene-PS thin films under the effects of blue-light. It is observed that the optical response of the PS/MEH-PPV/Alq3 films changes from red to yellow, and then to green with the radiation exposure. It is attributed to the photodegradation process of MEH-PPV and also to the spectral overlap between the photoemission of Alq3 and the absorption of MEH-PPV. The optical response of PS/MEH-PPV/Alq3 films was used to develop a novel organic flexible and low cost (<US$ 0.25) smart sensor to ensure the effectiveness of phototherapy treatment

X-rays sensing properties of MEH-PPV, Alq3 and additive components : a new organic dosimeter as a candidate for minimizing the risk of accidents of patients undergoing radiation oncology.

In this paper, we report our experimental design in searching a smart and easy-to-read dosimeter used to detect 6 MV X-rays for improving patient safety in radiation oncology. The device was based on an organic emissive solutions of poly(2-methoxy-5(2 -ethylhexyloxy)-p-phenylenevinylene) (MEHPPV), aluminum-tris-(8-hydroxyquinoline) (Alq3) and additive components which were characterized by UV?Vis absorption, photoluminescence and CIE color coordinate diagram. The optical properties of MEH-PPV/Alq3 solutions have been examined as function of radiation dose over the range of 0?100 Gy. It has shown that MEH-PPV/Alq3 solutions are specifically sensitive toX-rays, since the effect of radiation on this organic system is strongly correlated with the efficient spectral overlap between Alq3 emission and the absorption of degraded MEH-PPV, which alters the color and photoemission of MEH-PPV/Alq3 mixtures from red to yellow, and then to green. The rate of this change is more sensitive when MEH-PPV/Alq3 is irradiated in the presence of benzoyl peroxide than when in the presence of hindered phenolic stabilizers, respectively, an accelerator and an inhibitor to activate or inhibit free radical formation. This gives rise to optimize the response curve of the dosimeter. It is clear from the experimental results that organic emissive semiconductors have potential to be used as dedicated and low-cost dosimeters to provide an independent check of beam output of a linear accelerator and therefore to give patients the opportunity to have information on the dose prescription or equipment-related problems a few minutes before being exposed to radiation

X-ray dose detector based on color changing of light-emitting polymer?metal complex hybrid material.

We report on the design, fabrication and performance of a poly (2-methoxy-5(2_-ethylhexyloxy)- p-phenylenevinylene)/tris-(8-hydroxyquinoline)aluminum (MEH-PPV/Alq3) X-ray dose detector for improving safety for cancer patients shortly before radiation therapy. The detector consists of an inexpen-sive (<US$ 1) organic device that is irreversibly color changing from red, to yellow, to green and measures the delivered dose from the radiation beams of a linear accelerator (6 MV) in the range of 0?40 Gy. The effect of radiation on the optical properties of MEH-PPV/Alq3 was described and we observed a strong correlation between the photoemission spectrum of Alq3 and the photoemission and absorption spectra of MEH-PPV degraded by radiation. A series of tests was conducted on the performance of the organic detector in measuring depth-dose distribution of photon beams in a water phantom and demonstrating linearity in the shift of PL and absorption as functions of the dose. These results have enabled the qual-itative and quantitative analysis of how the radiation instability of optical properties of MEH-PPV/Alq3 can be used to develop an innovative organic device for radiation therapy

A versatile radiochromic dosimeter for low-medium gamma radiation and its application to food irradiation.

This article presents a novel radiochromic film for selective detection of low-medium (0?10 kGy) gamma radiation (60Co) doses. This dosimeter is based on a printed fluorescent multilayer structure comprising a paper substrate having layers of copper phthalocyanine (DY220) (a green emitter material) on the bottom, and layers of poly[2-methoxy-5(20-ethylhexyloxy)-p-phenylenevinylene] (MEH-PPV) (a green-light absorber, red emitter, and radiation sensitive polymer) on the top. The effect of gamma radiation on the optical properties of DY220/MEH-PPV was described: it was observed as a strong correlation between radiation dose and fluorescent, color coordinates for CIE (1931) chromatic diagram, and Pantone color reference of the dosimeter. The rate of these changes can be altered by manipulation of top?bottom layers to represent easily the radiation dose to be determined in a wide range. This versatile dosimeter has many uses in the field of food radiation for monitoring, quality assurance, and control of the gamma radiation process

CdWO4-on-MEH-PPV:PS as a candidate for real-time dosimeters.

We report on the investigations about the modification of optical properties induced by X-rays onto film detectors of cadmium tungstate (CdWO4), poly[2-methoxy-5(20 -ethylhexyloxy)-p-phenylenevinylene] (MEH-PPV) and polystyrene (PS) This device takes advantage of reduction of spectral overlap between the radioluminescence (RL) of CdWO4 and the absorption of MEH-PPV as it is exposed to radiation, forming the basis of a new dosimeter that is capable of converting the orange-red radioluminescence of PS:MEH-PPV:CdWO4 into green. We propose an explanation of the optical processes occurring in MEHPPV:CdWO4 in terms of the radiation hardness of CdWO4 combined to the RL-induced degradation of MEH-PPV

Organic and smart radiation sensor for x-ray in clinical radiotherapy.

Neste trabalho são apresentadas a fabricação e a caracterização óptica de um novo detector de raios X para monitoramento da dose nos processos de radioterapia empregando fótons de alta energia (6,0 MV). O dispositivo foi fabricado a partir de materiais orgânicos luminescentes consolidados como elemento ativo de displays eletroluminescentes nanoestrurados, mas que, até esse momento, têm sido pouco investigados como detectores de radiação ionizante. Para tanto, foram preparadas soluções à base de tris(8-hidroxiquinolato) de alumínio - Alq3 e poli(2-metóxi-5-(2-etilhexiloxi)-pfenilenovinileno) – MEH-PPV, cujo espectro de emissão do primeiro material se sobrepõe ao de absorção do segundo. Os resultados obtidos mostram que os espectros de emissão do sistema MEH-PPV/Alq3 desloca-se do vermelho-laranja (λmax = 598 nm) para o verde (λmax = 545 nm) quando a dose de radiação vai de 0 a 100 Gy. Essa mudança, consequência da degradação induzida pela radiação do MEH-PPV, foi usada no desenvolvimento de dosímetros para possível futura aplicação no controle do tratamento de pacientes oncológicos.In this work it is presented the characterization and fabrication of a novel ionizing radiation detector for high energy photon beam (6.0 MV). It is used organic luminescent materials usually applied in light-emitting and nanostructure device, but still few explored in radiation dosimetry. Organic solutions of tris(8-hydroxyquinolinato) aluminum - Alq3 and poly[2-methoxy-5-(2’-ethylhexyloxy)-p-phenylene vinylene] - MEH-PPV were prepared to better study the impact of spectral overlap between the Alq3 emission and MEH-PPV absorption. It is observed a blue-shift on the photoluminescence of the MEH-PPV/Alq3 solution system from red-orange (λmax = 598 nm) to green (λmax = 545 nm) when the radiation dose changes from 0 to 100 Gy. This effect is attributed to the photoxidation process of MEH-PPV and was employed to design dose accumulation detector in order to represent easily the radiation dose for cancer treatment