Production of the positron-emitting radionuclide 68Ga: the radiochemical scheme of radionuclide generator 68Ge → 68Ga

Abstract

⁶⁸Ga (T_1/2 = 68 min) in complexes with peptides is used in positron emission tomography  for diagnostics of neuroendocrine tumors. The most promising strategy for ⁶⁸Ga production is usage of the radionuclide generator ⁶⁸Ge → ⁶⁸Ga. In this research, the sorption behavior of Ge(IV) and Ga (III) has been studied. The distribution coefficients (K_d) of Ge(IV) on the anion exchange (Dowex 1×8) and cation exchange (Dowex 50×8) resins in various ethanedioic and hydrochloric acid solutions were determined. For each ion exchange resin, four series of measurements were carried out, in which the concentration of oxalic acid was fixed (0.001 M, 0.003 M, 0.005 M, 0.01 M), and the concentrations of hydrochloric acid ranged from 0 to 3 M. Based on the distribution coefficients, the chemical scheme of the radionuclide generator ⁶⁸Ge → ⁶⁸Ga has been developed. The chemical system is based on the anion exchange resin Dowex 1×8 and mixture of 0.005 M C₂H₂O₄ / 0.33 M HCl. Several types of the generators with direct and reverse mode of elution were tested and the optimal scheme was determined. Elution of the generators was performed once a day with 8 ml of 0.005 M C₂H₂O₄ / 0.33 M HCl solution. The 68Ga yield and the ⁶⁸Ge breakthrough are comparable for all the systems.