Aplicabilidade de transistor bipolar de junção em dosimetria de feixes elétrons de megavoltagem

• Autor(a) principal: Passos, Renan Garcia de
• Data de Publicação: 2015
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da UFS
• Texto Completo: https://ri.ufs.br/handle/riufs/5333
• topic: Dosimetria; Dispositivos eletrônicos; Radioterapia; Elétrons; Físico-química; Radiação; Transistores; Dosimetry; Electronic devices; Radiotherapy; Electrons; CNPQ::CIENCIAS EXATAS E DA TERRA::QUIMICA

With the evolution in the radiation studies was noticed the precautions needed in the ionizing radiation applications due to the effects caused by this particles or waves interacting with the atoms as it pass through, the radiation energy deposited at certain point is known as absorbed dose. The dosimetry is a study that quantifies the dose values deposited by the radiations, this quantification is really necessary in medical applications as radiotherapy. In this work was studied the possibility to use the BC856 bipolar junction transistor in electron beam dosimetry, a radiation very common in superficial tumors treatment. The bipolar junction transistor is an electronic device that amplifies current in electric circuits; this characteristic is known as current gain. Some researches already indicated that this amplifier capacity is reduced when devices exposed to radiations, due to damage caused in the structures. The transistors studied presented slightly different current gain, even those from the same package, therefore was selected just the devices with similar gain. The transistors was irradiated by electron beans generated from a Varian linear accelerator Clinac iX, 6, 9 and 12 MeV beans was used in the tests. The collector current was measured before the irradiations and immediately after using an electrometer, to determinate the current gain reduction. It was possible to observe a linear relation between dose and damage caused in transistors. Even through the devices do not completely recover from the damages caused by radiation the devices apparent to be reusable. In the percentage dose deposited in different acrylic depth was possible no notice results from the transistors resembling the linear accelerator calibration data. It´s possible to conclude that the transistors studied may be used in megavoltage electron beam dosimetry due to the possibility to relate the damage caused in the devices and the dose absorbed by then.