[en] Commercially the generators of ^99mTc use a chromatographic column loaded with alumina where the ⁹⁹ Mo, product of fission of the ²³⁵ U, it is retained and eluted the ^99m TcO₄ - by means of a saline solution. Among the limitations of this system, they are: the limited capacity of adsorption of the alumina (2 mg ⁹⁹ Mo/g alumina) and the production of significant quantities of radioactive waste of medium activity, product of the separation of the ⁹⁹ Mo and the rest of the products of fission of the ²³⁵ U that impose, on the other hand, elaborated radiochemical manipulations. Given these limitations, new procedures of preparation of generators ⁹⁹ Mo/^99m Tc, of low or medium activity specify that keep the same characteristics of quality and purity that those obtained by the traditional generator, via the nuclear reaction ⁹⁸ Mo(n,r)⁹⁹ Mo, they have been and they continue being study object. A viable option for the production of generators of ^99m Tc consists on using gels of titanium molybdates like matrixes of this generators. The gels are synthesized starting from solutions of TiCI₄ and (NH₄)₂ MoO₄ and irradiated later on. These gels allow to incorporate until 40% of Mo, with what is possible to obtain activities of up to 7.5 GBq/g ⁹⁹ Mo (200 mCi), avoiding the complex separation processes for their obtaining. Of capital importance they are the conditions of synthesis of the gels, which are presently study object work. Among the evaluated parameters they are: order of addition of the titanium solutions and molybdenum, molar ratio Ti:Mo, concentration of the solution of Ti, p H of the molybdates solution and laundry of those obtained gels, as well as the preparation of the columns. Trying to elucidate those structures of the synthesized materials, which are responsible for the properties of the corresponding generators, some techniques of such analysis were applied as: thermogravimetry, infrared microscopy, scanning electron microscopy of high vacuum and X ray diffraction. Gels of molar ratio Ti:Mo 1:1, 1.5:1, 2:1 and 1:2, were synthesized of which washed samples were irradiated and without washing. Encouraging results were obtained with the gel synthesized with a relationship equimolar Ti:Mo, TiCI₄ 0.828 M, adding Mo to Ti, and irradiated after washing. All the gels are amorphous and thermally stable up to the 780 C, showing the presence of a pure compound. (Author)

[en] The ^99m Tc, continues being the radionuclide more used in nuclear medicine to world scale. The production of this radioisotope, is carried out by means of generators ⁹⁹ Mo/^99m Tc that get ready commercially with ⁹⁹ Mo of high specific activity, adsorbed in alumina (2 mg ⁹⁹ Mo/g alumina) and that they are elutriated every 23 hours. In an alternative way, it is intended to use gels of titanium molybdates, as matrices of this generators. The gels are synthesized starting from solutions of ammonium molybdates and of titanium tetrachloride in aqueous media. These gels allow to incorporate until 25% of molybdenum in their structure, being been able to use ⁹⁹ Mo of low specific activity that can be obtained starting from the reaction ⁹⁸ Mo (n, γ) ⁹⁹ Mo. With the object of producing generators of medium activity, with the base of gels of titanium molybdates, intends in this work, to study the influence of two synthesis parameters of these gels: the concentration of the titanium solutions and the molar ratio Ti: Mo. The decrease of the concentration of the titanium solution, used during the synthesis of the gels, is converted in an efficiency decrease and radionuclide purity of the generators, as well as an increment so much of the volume of elutriation, as of the pH of the elutriates. The gels that contain an major number of titanium moles, regarding the molybdenum moles, present a greater radionuclide purity, but they diminish their efficiency. The best characteristics for the gels synthesis of titanium molybdates are: a molar ratio 1:1 for Ti and Mo, and to use solutions of titanium whose concentration is near at 1 M. (Author)