Implementation of a new separation method to produce qualitatively improved ⁶⁴ Cu

⁶⁴ Cu (T_1/2  = 12.7 h) is an important radionuclide for diagnostic purposes and used for positron emission tomography (PET). A previous method utilized at Paul Scherrer Institute (PSI) proved to be unreliable and, while a method using anion exchange chromatography is a popular choice worldwide, it was felt a different approach was required to obtain a robust chemical separation method.

Enriched ⁶⁴ Ni targets were created by electroplating on gold foil. The targets were irradiated with protons degraded to approximately 11 MeV at PSI's Injector 2 72 MeV research cyclotron and subsequently dissolved in HCl. The resultant solution was loaded onto AG MP-50 cation exchange resin and the ⁶⁴ Cu separated from its target material and radiocobalt impurities, produced as part of the irradiation process, using various specific mixtures of HCl/acetone solution. The eluted product was evaporated and picked up in dilute HCl (0.05 M). The chemical purity of ⁶⁴ Cu was determined by radiolabeling experiments at the highest possible molar activities.

Reproducible results were obtained, yielding 3.6 to 8.3 GBq ⁶⁴ Cu of high radionuclidic and radiochemical purity. The product was labeled to NODAGA-RGD, achieved at up to 500 MBq/nmol, indicating the high chemical purity. In a proof-of-concept in vivo study, ⁶⁴ Cu-NODAGA-RGD was used for PET imaging of a tumor-bearing mouse.

The chemical separation devised to produce high-quality ⁶⁴ Cu proved to be robust and reproducible. The concept can be used at medical cyclotrons utilizing a solid target station, such that ⁶⁴ Cu can be used at hospitals for PET imaging.