Cyclotron production of 68Ga via the 68Zn(pn)68Ga reaction in aqueous solution

摘要

The objective of the present work is to extend the applicability of the solution target approach to the production of ⁶⁸Ga using a low energy cyclotron. Since the developed method does not require solid target infrastructure, it offers a convenient alternative to ⁶⁸Ge/⁶⁸Ga generators for the routine production of ⁶⁸Ga. A new solution target with enhanced heat exchange capacity was designed and utilized with dual foils of Al (0.20 mm) and Havar (0.038 mm) separated by helium cooling to degrade the proton energy to ~14 MeV. The water-cooled solution target insert was made of Ta and its solution holding capacity (1.6 mL) was reduced to enhance heat transfer. An isotopically enriched (99.23%) 1.7 M solution of ⁶⁸Zn nitrate in 0.2 N nitric acid was utilized in a closed target system. After a 30 min irradiation at 20 μA, the target solution was unloaded to a receiving vessel and the target was rinsed with 1.6 mL water, which was combined with the target solution. An automated module was used to pass the solution through a cation-exchange column (AG-50W-X8, 200-400 mesh, hydrogen form) which efficiently trapped zinc and gallium isotopes. ⁶⁸Zn was subsequently eluted with 30 mL of 0.5 N HBr formulated in 80% acetone without any measurable loss of ⁶⁸Ga. ⁶⁸Ga was eluted with 7 mL of 3 N HCl solution with 92-96% elution efficiency. The radionuclidic purity was determined using an HPGe detector. Additionally, ICP-MS was employed to analyze for non-radioactive metal contaminants. The product yield was 192.5 ± 11.0 MBq/μ·h decay-corrected to EOB with a total processing time of 60-80 min. The radionuclidic purity of ⁶⁸Ga was found to be >99.9%, with the predominant contaminant being 67Ga. The ICP-MS analysis showed small quantities of Ga, Fe, Cu, Ni and Zn in the final product, with ⁶⁸Ga specific activity of 5.20-6.27 GBq/μg. Depending upon the user requirements, ⁶⁸Ga production yield can be further enhanced by increasing the ⁶⁸Zn concentration in the target solution and extending the irradiation time. In summary, a simple and efficient method of ⁶⁸Ga production was developed using low energy cyclotron and a solution target. The developed methodology offers a cost-effective alternative to the ⁶⁸Ge/⁶⁸Ga generators for the production of ⁶⁸Ga.