Electrokinetic removal of radionuclides contained in scintillation liquids absorbed in soil type Phaeozem.

Control samples of scintillation liquids - Phaeozem soil mixtures were prepared with different scintillation liquids as the support electrolyte, Install Gel® XF, (Ultima Gold AB™ and Ultima Gold XR™), to construct the polarization curves, and to select the cell potential with the highest mass transfer to remove 24Na (15 h) and 99mTc (6 h) as radiotracers from polluted Phaeozem soil. During the electrokinetic treatment (EKT), the removal of radionuclides contained in scintillation liquids absorbed in Phaeozem soil, liquid phase was characterized by Gas Chromatography coupled with a Flame Ionization Detector (GC-FID) and Fourier Transform Infrared Spectrometry (FTIR), solids by FTIR, before and after the application of cell potential. In this sense, the support electrolyte was selected based on the highest current generated (1 mA), as in the case of scintillation liquid 50% Ultima Gold XR™ + 50% Water (1:1), which was used for 6 h in the presence of a mesh and a titanium rod, as anode and cathode, respectively. Finally, the removal percentage accumulated in the liquid phase after the EKT of Phaeozem soil polluted by 99mTc was 61% close to the anode after 4 h. It was also 61% for 24Na close to cathode after 2 h, and after 4 h it was 71.8%.

Production optimization of 99Mo/99mTc zirconium molybate gel generators at semi-automatic device: DISIGEG.

DISIGEG is a synthesis installation of zirconium (99)Mo-molybdate gels for (99)Mo/(99m)Tc generator production, which has been designed, built and installed at the ININ. The device consists of a synthesis reactor and five systems controlled via keyboard: (1) raw material access, (2) chemical air stirring, (3) gel dried by air and infrared heating, (4) moisture removal and (5) gel extraction. DISIGEG operation is described and dried condition effects of zirconium (99)Mo- molybdate gels on (99)Mo/(99m)Tc generator performance were evaluated as well as some physical-chemical properties of these gels. The results reveal that temperature, time and air flow applied during the drying process directly affects zirconium (99)Mo-molybdate gel generator performance. All gels prepared have a similar chemical structure probably constituted by three-dimensional network, based on zirconium pentagonal bipyramids and molybdenum octahedral. Basic structural variations cause a change in gel porosity and permeability, favouring or inhibiting (99m)TcO(4)(-) diffusion into the matrix. The (99m)TcO(4)(-) eluates produced by (99)Mo/(99m)Tc zirconium (99)Mo-molybdate gel generators prepared in DISIGEG, air dried at 80°C for 5h and using an air flow of 90mm, satisfied all the Pharmacopoeias regulations: (99m)Tc yield between 70-75%, (99)Mo breakthrough less than 3×10(-3)%, radiochemical purities about 97% sterile and pyrogen-free eluates with a pH of 6.

[166Dy]Dy/166Ho hydroxide macroaggregates: an in vivo generator system for radiation synovectomy.

Radiation synovectomy is an effective treatment in patients suffering from inflammatory-rheumatoid and degenerative joint diseases. The aim of this work was to examine the feasibility of preparing dysprosium-166 (166Dy)/holmium-166(166Ho) hydroxide macroaggregates ([166Dy]Dy/166Ho-HM) as an in vivo generator for radiation synovectomy evaluating whether the stability of 166Dy-HM and 166Ho-HM complexes is maintained when the daughter 166Ho is formed. The Monte Carlo (MCNP4B) theoretical depth dose profile for the in vivo [166Dy]Dy/166Ho generator system in a joint model was calculated and compared with that produced by 90Y, 153Sm and 166Ho. 166Dy was obtained by neutron irradiation of enriched 164Dy2O3 in a Triga Mark III reactor. Macroaggregates were prepared by reaction of [166Dy]DyCl3 with 0.5 M NaOH in an ultrasonic bath. [166Dy]Dy/166Ho-HM was obtained with radiochemical purity >99.5% and with the majority of particles in the 2-5 microm range. In vitro studies demonstrated that the radio-macroaggregates are stable in saline solution and human serum without a significant change in the particle size over 14 d, suggesting that no translocation of the daughter nucleus occurs subsequent to beta- decay of 166Dy. Biological studies in normal rats demonstrated high retention in the knee joint even 7 d after [166Dy]Dy/166Ho-HM administration. The Monte Carlo (MCNP4B) theoretical depth dose profiles in a joint model, showed that the in vivo [166Dy]Dy/166Ho generator system would produce 25% and 50% less radiation dose to the articular cartilage and bone surface, respectively, than that produced by 90Y or pure 166Ho in a treatment with the same therapeutic dose to the synovium surface. Despite that 153Sm showed the best depth dose profile sparing doses to healthy tissues, the use of 166Dy could provide the advantage of being applied in patients that cannot be reached within a few hours from a nuclear reactor and to produce less radiation exposure to the medical personnel during the radiopharmaceutical administration.

Effect of Zr:Mo ratio on 99mTc generator performance based on zirconium molybdate gels.

Zirconium molybdate gels have shown to be viable alternatives for preparation of 99mTc generators using 99Mo produced by neutron activation. The aim of this work was to investigate the effect of the Zr:Mo molar ratio on the gel chemical structure and correlate it with the elution efficiency. A series of gels were prepared at Zr:Mo molar ratios from 0.5:1 to 2.3:1 and characterized by TGA, IR, XRD and UV. It was found that the variation of Zr:Mo ratio produces different polymolybdate arrangements on the octahedral units around to the zirconia which is mainly influenced by the water content. When the matrix molybdenum concentration was increased a lesser amount of water was found and the elution efficiencies were increased. However high elution efficiencies produce higher 99Mo breakthrough values. The gel formulation appears thus to be a compromise between the elution efficiency and the molybdenum breakthrough. The chemical-physical properties of these gels are presented and discussed.

Labeling of biotin with [166Dy]Dy/166Ho as a stable in vivo generator system.

The aim of this work was to synthesize [166Dy]Dy/166Ho-DTPA-Biotin to evaluate its potential as a new radiopharmaceutical for targeted radiotherapy. Dysprosium-166 (166Dy) was obtained by neutron irradiation of enriched 164Dy(2)O(3) in a Triga Mark III reactor. The labeling was carried out in aqueous media at pH 8.0 by addition of [166Dy]DyCl(3) to diethylenetriaminepentaacetic-alpha,omega-bis(biocytinamide) (DTPA-Biotin). Radiochemical purity was determined by high-performance liquid chromatography (HPLC) and TLC. The biological integrity of labeled biotin was studied evaluating its avidity for avidin in an agarose column and by size-exclusion HPLC analysis of the radiolabeled DTPA-Biotin with and without the addition of avidin. Stability studies against dilution were carried out by diluting the radiocomplex solution with saline solution and with human serum at 37 degrees C for 24 h. The [166Dy]Dy/166Ho-labeled biotin was obtained with a 99.1+/-0.6% radiochemical purity. In vitro studies demonstrated that [166Dy]Dy/166Ho-DTPA-Biotin is stable after dilution in saline and in human serum and no translocation of the daughter nucleus occurs subsequent to beta(-) decay of 166Dy that could produce release of 166Ho(3+). Avidity of labeled biotin for avidin was not affected by the labeling procedure. Biodistribution studies in normal mice showed that the [166Dy]Dy/166Ho-DTPA-Biotin has a high renal clearance. In conclusion, the radiolabeled biotin prepared in this investigation has adequate properties to work as a stable in vivo generator system for targeted radiotherapy.