OBJETIVO: Avaliar o desempenho de um equipamento de raios X utilizado em radiologia intervencionista e a qualidade de imagem produzida, aplicando alguns testes de controle de qualidade. MATERIAIS E MÉTODOS: O equipamento de raios X testado foi da marca Philips (Integris H3000), do serviço de hemodinâmica de um hospital do Rio de Janeiro. Foram utilizados objetos de teste de Leeds para avaliar a qualidade da imagem, e um sistema Radcal 9015 para medições dosimétricas. RESULTADOS: Nos modos high e normal, os valores medidos das taxas de kerma no ar foram diferentes dos esperados. Em alguns casos, os valores das taxas medidas não foram afetados pelo uso de diferentes modos de magnificação. A avaliação da qualidade da imagem apresentou resultados diferentes dos valores recomendados pelas normas. Isto pode levar à obtenção de imagens de menor qualidade e ao aumento da exposição à radiação de pacientes e profissionais. CONCLUSÃO: Os resultados mostraram a importância da aplicação periódica de testes de controle de qualidade, que permitem monitorar o desempenho do equipamento e estimar a exposição dos pacientes e trabalhadores. Os resultados obtidos sugerem a necessidade de uma revisão no sistema de aquisição de imagens do equipamento.
OBJECTIVE: The PENELOPE code was utilized to simulate irradiation geometries where heterogeneities are present and to simulate a photon beam behavior under these conditions. MATERIALS AND METHODS: For the homogeneous case, the ionizing radiation behavior was simulated only with water, and different materials were introduced to simulate heterogeneous conditions. Cubic geometries were utilized for the homogeneous phantoms, and parallelepiped-shaped geometries for the heterogeneities with the following composition: bone and lung tissue simulators, as recommended by the International Commission on Radiological Protection, and titanium, aluminum and silver. Input parameters were defined as follows: energy and type of source, 6 MV photons; source-surface distance=100 cm; and radiation field of 10×10 cm 2. RESULTS: Percentage depth-dose curves were obtained for all the cases. As result, it was observed that for high electronic density materials, such as silver, the absorbed dose is higher than the absorbed dose in the homogeneous phantom, and for the lung tissue simulator, it is lower. CONCLUSION: Results clearly demonstrate the relevant role of heterogeneities in the treatment planning system algorithms utilized in the calculation of dose distribution in patients, increasing the accuracy of the dose delivered to the tumor and avoiding unnecessary irradiation of healthy tissues. Keywords: Radiotherapy; Monte Carlo; PENELOPE; Heterogeneities; Depth-dose distribution.OBJETIVO: Utilizar o código PENELOPE e desenvolver geometrias onde estão presentes heterogeneidades para simular o comportamento do feixe de fótons nessas condições. MATERIAIS E MÉTODOS: Foram feitas simulações do comportamento da radiação ionizante para o caso homogêneo, apenas água, e para os casos heterogêneos, com diferentes materiais. Consideraram-se geometrias cúbicas para os fantomas e geometrias em forma de paralelepípedos para as heterogeneidades com a seguinte composição: tecido simulador de osso e pulmão, seguindo recomendações da International Commission on Radiological Protection, e titânio, alumínio e prata. Definiram-se, como parâmetros de entrada: a energia e o tipo de partícula da fonte, 6 MV de fótons; a distância fonte-superfície de 100 cm; e o campo de radiação de 10×10 cm 2 . RESULTADOS: Obtiveram-se curvas de percentual de dose em profundidade para todos os casos. Observou-se que em materiais com densidade eletrônica alta, como a prata, a dose absorvida é maior em relação à dose absorvida no fantoma homogêneo, enquanto no tecido simulador de pulmão a dose é menor. CONCLUSÃO: Os resultados obtidos demonstram a importância de se considerar heterogeneidades nos algoritmos dos sistemas de planejamento usados no cálculo da distribuição de dose nos pacientes, evitando-se sub ou superdosagem dos tecidos próximos às heterogeneidades. Unitermos: Radioterapia; Monte Carlo; PENELOPE; Heterogeneidades; Dosimetria. AbstractResumo
Purpose: Characterize the value of dose rate received by the nuclear medicine professionals during the examination procedure and handling of radiopharmaceuticals, permiting the realization of more specific pratices of radioprotection in nuclear medicine. Method and Materials: For this work was monitoring two professional in two separate nuclear medicine services, totaling four profissionals monitoring during two moths. Their routine was not modified. The measuring of the rate dose was made with an ionization chamber model Babyline 81 at a distance of 1.0 m from the source. The measurements were made during the eluation of radioisotope, preparation the radiopharmaceuticals, in the administration and during the exam realization. The value of the rate dose was associated the procedure realized, for this way to caracterize the level of exposure that the professional it was sudmitted during your daily work. Results: It was observed for the test of renal scintigraphy with DTPA an average of 2.55 μGy/h and an average value of 1.20 μGy/h to DMSA. For examinations of bone scintigraphy with MDP was observed an average of 2.63 μGy/h for the protocol of time and 3.09 μGy/h for the protocol of counting, the difference in protocol is due to different interpretation medical. The bone flow scintigraphy the average rate dose was 5.17 μGy/h. The values of the background radiation measured over the handling of radiopharmaceuticals shows a maximum increase of up to six times the background radiation before manipulation and this value influence the measurements performed by measuring activity. Conclusion: The evaluation of the values of dose rate may help in taking action directed to optimizing the radioprotection and minimize the sum of errors during a correct administered radiopharmaceutical to the patient, minimizing the dose in the pacient and in the professional.
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