Preparation of electroplated zinc-68 targets for gallium-68 cyclotron production using recovered zinc-68

Gallium-68 (68Ga) is a PET isotope that is finding more use in the clinical setting as a PET diagnostic tool, for example 68Ga PSMA is widely used in the diagnosis of prostate cancer, and 68Ga dotatate for the diagnosis of neuroendocrine tumors. Current production is mostly performed using either 68Ge/68Ga generators or liquid targets containing 68Zn and irradiated with protons in an accelerator. Recently, GE Healthcare published an article describing the irradiation and purification of 68Ga using a solid 68Zn target. This article describes an electroplating process used to produce 68Zn targets.

The method to produce 68Zn cyclotron targets for 68Ga production by electroplating zinc-68 onto a 1" diameter 99.99% natural silver planchette is described. Each target had differing plated masses, ranging from 40 to 170 mg using an electroplating solution produced from purified zinc-68 effluent from prior, non-solid target based 68Ga production processes. The targets were irradiated using a GE PET cyclotron proton beam with an energy of 16.5 MeV and beam current approximately 80 mA. Radiochemical yields of purified gallium-68 resulting from the dissolution of each target were measured using preliminary HPGe results to determine gallium-68 yield. The gallium-68-specific gamma emission at 1077.3 keV, as opposed to the indirect emission at 511 keV, was used to determine the amount of 68Ga present in the sample. In addition, the amount of stable metal contaminants (Zn, Fe, Ag and Al) were measured using qualitative ICP-OES.

The targets produced using this technique were stable to both mild-mechanical abrasion (wipe with non-metallic material and washing with water) and irradiation by a 16.5 MeV cyclotron proton beam. Based on initial data, the optimum plating mass for 68Zn targets is between 60 mg and 160 mg. This applies to targets produced by this method and subsequently irradiated, digested, and purified using GE Healthcare equipment and protocols.

This article provides methodology to produce 68Zn solid targets for cyclotron production of 68Ga. The initial results from 68Ga specific quality control analytical techniques demonstrate the potential for establishing a GMP-compliant production process within an academic or hospital setting.