Development of a computacional model for calculations of absorved dose to organs and tissues of the human body in situations of accidental exposures / Desenvolvimento de um modelo computacional para cÃlculos de dose absorvida em ÃrgÃos e tecidos do corpo humano nas situaÃÃes de exposiÃÃes acidentais

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

Exposure to a radiation field may be of medical, environmental, occupational or accidental nature, but in all cases the main objective is the determination of the whole body absorbed dose or the distribution of absorbed dose to specific organs and tissues. In recent years, estimates of the radiation absorbed dose in the human body have become more accurate due to the advances of modern technology in the areas of instrumentation and computer development. Apart from dosimeters and biodosimetrical methods, there exist computational exposure models based on Monte Carlo (MC) methods for the calculation of absorbed doses to organs and tissues. To properly simulate the radiation transport processes in the human body, the computational MC code should be coupled to an anthropomorphic voxel phantom, which currently can be considered as the best true to nature representation of the human body for the purpose of absorbed dose determination. In this work, a computational exposure model was developed by coupling the Monte Carlo EGS4 code to the MAX voxel phantom, which was adequately modified to allow especially for the evaluation of absorbed dose to humans exposed to external radiation sources in accidental situations. In order to easily adapt the MAX/EGS4 exposure model to accidental situations, a generalized point source was developed which can be positioned at arbitrary locations with respect to the human body. Proper functioning of this generalized point source was verified with an Alderson-Rando (AR) phantom. The physical AR phantom was scanned by a computer tomograph and the segmented images of the virtual AR phantom were subsequently connected to the EGS4 MC code. Data from experimental exposures of the physical AR phantom were then compared to the results obtained from corresponding exposures simulations of the virtual AR phantom with the EGS4 MC. Application of the MAX/EGS4 accidental exposure model will be demonstarted in this study for two selected radiation accidents which happened in Yanango (Peru) and Nesvizh (Belarus). According to information given in corresponding reports of the International Atomic Energy Agency (IAEA) exposure conditions of the two accidents have been simulated with the MAX/EGS4 exposure model, which in case of the accident in Nesvizh (Belarus) included a modification of the posture of the MAX phantom. The results show that the MAX/EGS4 exposure model can properly be adjusted to specific irradiation conditions, and absorbed doses to radiosensitive tissues and organs resulting from accidental exposures can be determined with sufficient accuracy which is crucial for the medical treatment of the exposed individuals

ASSUNTO(S)

egs4 acidentes radiolÃgicos alderson-rando voxel phantoms fantomas de voxels engenharia nuclear radiological accidents egs4 alderson-rando

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