Recovery of zinc-68 from gallium-68 cyclotron target effluent: A method to establish wet chemistry capabilities for metal precursor recovery in PET radiometals.

[BACKGROUND] Gallium-68 (68Ga) is a PET isotope that is finding more use in the clinical setting as a PET diagnostic tool, e.g. 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 germanium-68/gallium-68 (68Ge/68Ga) generators or liquid targets containing zinc-68 (68Zn) and irradiated with protons in an accelerator. Recently, GE Healthcare published an article describing the production and purification of 68Ga using solid 68Zn target irradiation. The method described in this study to recover 68Zn from liquid target effluent may also be used to re-purify 68Zn from effluents from 68Ga production using solid targets. Preliminary studies, to be published in a follow-up paper, that result in electroplated solid 68Zn targets are briefly mentioned to demonstrate that such targets can be made from the 68Zn purified using this recovery method.

[METHOD] An ion-exchange based method was used for purifying (or 'recovering') target material-containing effluent for future reuse in target preparation. This was accomplished using a column with Bio-Rad AG1-X8 resin bed of approximately 20-25 g of resin in a glass ion-exchange column. Eluted fractions from the ion-exchange column were tested using a NexION 350D ICP-MS to detect the presence of total zinc and trace contaminants Cu, Fe, Pb, Cr, Al, Mn, Ti, Ni, and Ag. The isotopic purity of the 68Zn in the effluent was also measured to confirm the original isotopic ratio.

[RESULTS] The results presented indicate that any contaminants in the effluent samples were reduced to levels below the limits of detection of analytical techniques commonly used in PET manufacturing laboratories (including ICP-OES).

[CONCLUSION] This article provides a simple method for recovering 68Zn from liquid target effluent to be used in the plating of 68Zn targets for 68Ga solid target production. This method will allow academic/PET facilities to establish a wet chemistry process for recovering 68Zn and, using separation schemes published or developed elsewhere, and other precursors used for making solid cyclotron targets for isotope production.