Detalhes bibliográficos
| Ano de defesa: |
2016 |
| Autor(a) principal: |
Cunha, Julyanne Silva
 |
| Orientador(a): |
Carvalho Júnior, Albérico Blohem de |
| Banca de defesa: |
Não Informado pela instituição |
| Tipo de documento: |
Dissertação
|
| Tipo de acesso: |
Acesso aberto |
| Idioma: |
por |
| Instituição de defesa: |
Universidade Federal de Sergipe
|
| Programa de Pós-Graduação: |
Pós-Graduação em Física
|
| Departamento: |
Não Informado pela instituição
|
| País: |
Brasil
|
| Palavras-chave em Português: |
|
| Área do conhecimento CNPq: |
|
| Link de acesso: |
https://ri.ufs.br/handle/riufs/5366
|
Resumo: |
Total Body Irradiation is a special technique of radiotherapy used for conditioning for bone marrow transplantation. Its function is to immunosuppression, bone marrow ablation and destruction of malignant cells. How it is the irradiation of a large and irregular field is necessary to seek ways to offset the tissues so that the absorbed dose to the patient's body has a uniformity of ± 10%. In addition, other factors intervene so that this condition is satisfied, such as the choice of radiation source, the posture of the patient, the incidence geometry, the distance of treatment, the combination of fields, among others. To analyze how these factors influence the dose distribution in the body, in this study we were simulated computationally scenarios of Total Body Irradiation, using telecobaltherapy units and linear accelerator of 6 MV, for an estimated equivalent and effective doses using the code MCNPX of radiation transport and hybrid anthropomorphic simulators UFHADF and UFHADM in sitting postures to RLAT and LLAT irradiation, and lying to the AP and PA projections. To validate the spectra used in the simulations was calculated PDP for comparison with experimental measurements. As for the validation of TBI scenarios were estimated entrance dose rates in skin also for comparison with experimental measurements. The PDP curves are shown according to the literature. The values of the estimated dose rates are less than 10% relative difference in relation to the experimental measurements, which allowed us to estimate the dose in the organs. The simulation results show that the lateral irradiations of UF simulators in the sitting posture offer a less uniform dose distribution compared to radiation AP / PA with the simulator in lying posture. For the PA irradiation geometry the absorbed dose in the red marrow is approximately 20% higher than in the AP projection, which suggests that the first case is most appropriate for the destruction of diseased marrow. Regarding the use of attenuators objects for radiation attenuation in the lung there was a reduction of 23% of the absorbed dose by this organ, which shows their effectiveness and importance to these procedures. It was also observed that the decrease in patient treatment away from the radiation source and the room walls leads to a near increase of 10% and 5%, respectively, the absorbed dose, which suggests that treatments be more suitable carried out great distances focus-surface and far from the room's walls. The energy beam used for Total Body Irradiation, the most significant differences between the Cobalt-60 and linear accelerator 6 MV spectra were up to 46.23%, which occurred for the AP irradiation geometry, where observed that the first deposits most of its energy near the surface, which shows that more energy beams for irradiation are more effective at greater depths. Another factor analyzed was the combination of adjacent and overlapping fields for the treatment, leading to overdoses in some organs and committed dose uniformity as observed by other authors. The calculation of the effective dose showed that there is a greater overall commitment of the body to radiation in LLAT incidence geometry. It was also found that the effective dose is higher in the AP projection than PA as found in the literature. The analyzes show the importance and suggest a more detailed study of the exposure conditions for planning treatments for TB |
