Cyclotron Production and Separation of Scandium Radionuclides from Natural Titanium Metal and Titanium Dioxide Targets.

Theranostic strategies involve select radionuclides that allow diagnostic imaging and tailored radionuclide therapy in the same patient. An example of a Food and Drug Administration-approved theranostic pair is the ⁶⁸ Ga- and ¹⁷⁷ Lu-labeled DOTATATE peptides, which are used to image neuroendocrine tumors, predict treatment response, and treat disease. However, when using radionuclides of 2 different elements, differences in the pharmacokinetic and pharmacodynamic profile of the agent can occur. Theranostic agents that incorporate the matched-pair radionuclides of scandium- ⁴³ Sc/ ⁴⁷ Sc or ⁴⁴ Sc/ ⁴⁷ Sc-would guarantee identical chemistries and pharmacologic profiles. The aim of this study was to investigate production of ^43,44,47 Sc via proton-induced nuclear reactions on titanium nuclei using a 24-MeV cyclotron. Methods: Aluminum, niobium, and tantalum target holders were used with titanium foils and pressed TiO ₂ to produce scandium radionuclides with proton energies of up to 24 MeV. Irradiated targets were digested using NH ₄ HF ₂ and HCl in a closed perfluoroalkoxy alkane vessel in 90 min. Scandium radionuclides were purified via ion-exchange chromatography using branched N,N,N',N' -tetra-2-ethylhexyldiglycolamide. The titanium target material was recovered via alkali precipitation with ammonia solution. Results: Titanium foil and TiO ₂ were digested with an average efficiency of 98% ± 3% and 95% ± 1%, respectively. The typical digestion time was 45 min for titanium foil and 75 min for TiO ₂ The average scandium recovery was 94% ± 3%, and the average titanium recoveries from digested titanium foil and TiO ₂ after precipitation as TiO ₂ were 108% ± 8% and 104% ± 5% of initial mass, respectively. Conclusion: This work demonstrated a robust method for the cyclotron production of scandium radionuclides that could be used with natural or enriched TiO ₂ target material.
(© 2021 by the Society of Nuclear Medicine and Molecular Imaging.)