Browsing by Author "Sousa, Patrick Emmanuel"
Now showing 1 - 3 of 3
Results Per Page
Sort Options
- Development of a high resolution detector for medical imaging with ionizing radiation: = desenvolvimento de um detector de alta resolução para imagem médica com radiações ionizantesPublication . Sousa, Patrick Emmanuel; Silva, Maria da Conceição Abreu e; Mendes, Pedro Fernando Paulo RatoEste trabalho apresenta o desenvolvimento de um protótipo de uma câmara gama projectado de forma a demonstrar as suas capacidades em imagem bidimensional de alta resolução. Em particular, a imagiologia molecular e a visualização de órgãos internos de pequenos animais são considerados. O sistema proposto é um dispositivo compacto que oferece o potencial para uma resolução inferior ao milímetro. O sistema consiste numa câmara optoelectrónica híbrida – o tubo ISPA (Imaging Silicon Pixel Array) acoplado a uma electrónica específica. O tubo, originalmente desenvolvido para propósitos de física de altas energias no CERN, foi testado com sucesso no campo da imagiologia com radiação gama de baixa energia utilizando fontes radioactivas, demonstrando capacidades reais quer em resolução espacial quer em energia. O primeiro sistema electrónico de leitura desenvolvido foi implementado para validar o conceito de imagem bidimensional. Uma das principais desvantagens deste sistema era seu tamanho e devido às restritas exigências necessárias de modo a empregar este tipo de detector em aplicações biomédicas por não físicos, um novo sistema de leitura compacto e apropriado foi projectado e construído. Neste trabalho é apresentado uma nova geração em electrónica de leitura para o controlo e o processamento em tempo real de imagens com o tubo ISPA, que conduziu ao desenvolvimento de uma ferramenta importante em imagiologia digital.
- Study of scattered radiation during fluoroscopy in hip surgeryPublication . Lesyuk, Oksana; Sousa, Patrick Emmanuel; Rodrigues, Sónia; Abrantes, António; Almeida, Rui; Pinheiro, João; Azevedo, Kevin; Ribeiro, Luís PedroObjective: To measure the scattered radiation dose at different positions simulating hip surgery. Materials and Methods: We simulated fluoroscopy-assisted hip surgery in order to study the distribution of scattered radiation in the operating room. To simulate the patient, we used a anthropomorphic whole-body phantom, and we used an X-ray-specific detector to quantify the radiation. Radiographs were obtained with a mobile C-arm X-ray system in continuous scan mode, with the tube at 0° (configuration 1) or 90° (configuration 2). The operating parameters employed (voltage, current, and exposure time) were determined by a statistical analysis based on the observation of orthopedic surgical procedures involving the hip. Results: For all measurements, higher exposures were observed in configuration 2. In the measurements obtained as a function of height, the maximum dose rates observed were 1.167 (± 0.023) µSv/s and 2.278 (± 0.023) µSv/s in configurations 1 and 2, respectively, corresponding to the chest level of health care professionals within the operating room. Proximal to the patient, the maximum values were recorded in the position occupied by the surgeon. Conclusion: We can conclude that, in the scenario under study, health care professionals workers are exposed to low levels of radiation, and that those levels can be reduced through the use of personal protective equipment.
- Study of the scattered x-ray distributions around a mammography unitPublication . Lima, Patricia; Sousa, Patrick Emmanuel; Rodrigues, Sónia Isabel do Espírito Santo; Abrantes, António; Silva, Carlos; Ribeiro, Luís; De almeida, Rui; Azevedo, KevinPurpose: To measure the distribution of scattered radiation in a mammography unit for shielding design purposes. Methods and Materials: Measurements were carried out with an anthropomorphic phantom used to simulate a body from one adult patient. The dose rate for scattered radiation was recorded by placing a solid state sensor (Unfors Xi Survey Detector) every 10 degrees at 1 m distance from the FOV centre, in the axial and coronal planes of the breast. The scattered radiation distribution was treated as isodose curves, specifying the amount of radiation that will be delivered to a specific point in the room around the equipment (GE Senographe DMR). More than 50 exposures were made with a tube voltage of 30 kVp, anode-filter combination Mo/Mo and large focus. Results: In the axial plane, results show that the scattered radiation is absorbed up to 73% on the back of the anthropomorphic phantom, at the potter bucky plane height. In the coronal plane, the scattered radiation significantly increases with the angle due to backscattering effect. Assuming the direction of the incidence beam is 0 degree, results show that the scattered radiation is 86% higher at 160 degrees than at 90 degrees. Conclusion: The type of mammographic view and the patient´s body strongly influence the distribution of scattered x-ray radiation. These results can be used to improve the shielding design of a mammographic unit with less resources and less spending on shielding barriers.