Desenvolvimento e análises de sementes sintetizadas atravésda rota sol-gel para implantes em tumores de próstata

• Ano de defesa: 2005
• Autor(a) principal: Wanderley dos Santos Roberto
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Minas Gerais; UFMG
• Palavras-chave em Português: Engenharia Metalúrgica e de Minas; Engenharia metalúrgica; Prostata Tumores; Ciência dos materiais; Bioengenharia; Câncer Tratamento
• Link de acesso: http://hdl.handle.net/1843/BUOS-8DUK5Z

In the present work it was proposed the production of seeds synthesized by the sol-gel process, incorporating natural samarium, and containing the isotope 152Sm to be activated in 153Sm, as an alternative for the treatment of prostate cancer. The first stage of this work involved a study of the viability of the incorporation of the element Sm in the bioglass, in which it was also performed a theoretical study of neutronic activation, which is able to estimate the amount of Sm, that will induce a radioactive activity similar to the activity in which conventional seeds are used. In this same stage, a dosimetric study was done, using the Monte Carlo MCNP-4B method, to estimate the radial distribution of the absorbed dose due to implants of seeds containing samarium atoms. In the second stage, a study of the dissolution in vitro was performed, and also a study of the biodegradability in vivo through a pilot study. These two stages were followed by studies of the composition and structure of the samples. In the third stage, a dosimetric study of the radial distribution ofabsorbed dose was accomplished, through the MCNP-4B, PENELOPE and EGSnrc codes, based on the Monte Carlo method. In this study, the absorbed doses were estimated with macroaggregated seeds placed at 6.0x103m far from each other. In addition, in this stage a radiopacity analysis of the seeds containing Sm, geometrically elaborated for theuse in brachytherapy on the prostatic gland, was performed. The composition analysis demonstrated that it was possible to incorporate the element Sm in the samples synthesized by the sol-gel process. The results indicated that the samples are amorphous, presenting great surface area, that varied from 77 to 353m2.g1, increasing with the concentration of SiO2, whereas the variables as pore volume and pore size decrease with the concentration of CaO. The in vitro dissolution studies, presented an apparent increase on the concentration of Si,Ca and Sm in the first hours, maintaining a relatively constant level after 24 hours in solution. In this study, it was possible to verify that the kinetics of dissolution of Si and Ca was greater than the kinetics of dissolution ofSm.The concentrations of Si and Ca were respectively 436 and 4660 times larger than the Sm concentration in SBF. These data allow us to say that, when radioactive seeds prepared with the compositions here studied, are implanted in vivo, little amount of radioactive Sm will be liberated in the body in short-term, avoiding that radioactive material migrate for unwanted areas. The in vivo study, realized through the animal pilot model, was capable of demonstrating that, as described in the literature, the glasses produced here through sol-gel method do not present toxic level.i With the dosimetric studies it was possible to estimate that the absorbed dose in the prostate will be of 276Gy, 126Gy above the value of absorbed dose using conventional seeds,according to recently published studies. The dosimetric results revealed that the absorbed dose due to the interactions originated from synthesized seeds with 153Sm, will be 100 times higher than the 125I, up to 2.75mm, demonstrating that this possibly happens due to the beta dose contribution of the 153Sm. The theoretical and instrumental analysis of neutronic activation showed that the seeds synthesized via sol-gel process, can obtain activity levels of 407MBq within 75 minutes of activation with thermal and epithermal neutron flux of 6.6x1011 n.cm2.s1 and 2.5x1010 n.cm2.s1, respectively. From the theoretical and experimental data it could be estimated that, with the seeds synthesizedwith the isotope 153Sm, substituting for the natural samarium, only 20 minutes of activation with the neutronic flux previously mentioned will be necessary. The geometrically elaborated seeds presented good radiopacity in X-ray diagnostic, in comparison with the 125I seeds. The obtaining of the seeds geometrically elaborated is possible due to the easiness of the synthesis, manipulation and molding of glasses via sol-gel process reported extensively in the literature.