AvaliaÃÃes dosimÃtricas em pacientes submetidos à radioiodoterapia com base em fantomas de Voxels e em imagens de medicina nuclear

AUTOR(ES)

Ferdinand de Jesus Lopes Filho

DATA DE PUBLICAÇÃO

2007

RESUMO

In radioiodine therapy, the patients are submitted to the incorporation of a radioactive Sodium Iodide substance (NaI), which reacts physiologically with metastases, thyroid tissue remainders and other organs and tissues of the human body. There is a complex question, which is, the evaluation of the temporal and spatial distribution of the absorbed dose in radiosensitive organs and tissues of the patients submitted to this kind of treatment. As it is practically impossible to measure the absorbed dose in the internal regions of the patient in a direct form, numeric dosimetry is used in such estimates. Numeric dosimetry uses anthropomorphic models coupled to Monte Carlo codes for simulating the transport of radiation and its interaction with matter, as well as evaluating the deposited dose in radiosensitive organs and tissues. To carry out these dose evaluations, it is necessary to develop algorithms for simulating the radioactive sources involved in the problem. The group formed by the radioactive sources, the anthropomorphic models and the Monte Carlo code is, usually, denominated the exposure computational model, where the word exposure is in its more general sense. The objective of this work is to develop one of these models for estimating the absorbed dose fractions, the specific absorbed dose fractions and the ratios between absorbed dose and accumulated activity of the 131I, that are specific for patients submitted to the radioiodine therapy. The anthropomorphic model used is the FAX (Female Adult VoXel) voxel phantom. The algorithms for simulating the internal radioactive sources are based on scan images of patientâs whole body and the Monte Carlo code is the EGS4. The results obtained with the model developed were compared with the solfware MIRDOSE 3 and with similar published data. It is possible to esteem the equivalent doses in radiosensitive organs and tissues of the patients using the conversion coefficients here developed.

ASSUNTO(S)

engenharia nuclear radioiodine therapy medicina nuclear radioiodoterapia dosimetry monte carlo fantomas de voxels dosimetria voxel phantoms nuclear medicine

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