Cyclotron production of ⁶⁷Ga using electroplated ⁶⁸Zn targets on gold and gold-coated aluminum backings.

Abstract

Gallium-67 remains a relevant radionuclide for single-photon emission computed tomography (SPECT) and radiopharmaceutical development as a longer-lived ⁶⁸Ga surrogate. In this work, the use of gold and gold-coated aluminum backings was evaluated for the cyclotron-based production of this radionuclide via the ⁶⁸Zn(p,2n)⁶⁷Ga nuclear reaction. Using such targets, activities of 2.1-2.6 GBq were achieved for irradiation times of 120-150 min at end of proton bombardment, corresponding to saturation yields of 2900-3800 MBq/μA. A radiochemical separation based on two chromatographic resins, combined with an anion-exchange step, was evaluated to recover over 70 % of the [⁶⁷Ga]GaCl₃ in 0.5 mL. Radionuclidic purity exceeded 98 % at end of purification and increased with time due to the decay of the shorter-lived ⁶⁶Ga. Trace metal analysis and test radiolabelling with NOTA confirmed apparent molar activities between 13 and 70 GBq/μmol, depending on the purification scheme. The suitability of the produced [⁶⁷Ga]GaCl₃ for radiopharmaceutical applications was further validated by the successful synthesis of six ⁶⁷Ga-labelled radioligands, namely [⁶⁷Ga]Ga-PSMA-11, [⁶⁷Ga]Ga-PSMA-I&T, [⁶⁷Ga]Ga-FAPI-46, [⁶⁷Ga]Ga-FAP-2286, [⁶⁷Ga]Ga-DOTA-TATE, and [⁶⁷Ga]Ga-DPI-4452. Gold-coated aluminum backings demonstrated good irradiation stability, although further optimization is required to improve reusability.