Small cyclotron production of non-carrier-added ¹⁰³Pd from electroplated Rh targets

With the emission of both Auger and conversion electrons (AE and CE) together with some x-rays and a few low intensity gamma-rays, palladium-103 (¹⁰³Pd, T_1/2 17 d) and its daughter rhodium-103m (^103mRh, T_1/2 56 min) are interesting radionuclides for applications in targeted radionuclide therapy. ¹⁰³Pd's x-ray emissions have been applied in brachytherapy implants, but the unavailability of non-carrier-added (n.c.a.) ¹⁰³Pd has limited the development of ¹⁰³Pd-radiolabeled compounds that exploit its AE and CE emissions. Through a collaboration between UWM and DTU, we have developed a procedure to produce n.c.a. ¹⁰³Pd from Rh foils and electroplated Rh targets on graphite backings. The targets were irradiated on 16 MeV cyclotrons at 20-40 μA with a production yield of 1.6-2.2 MBq/μAh. Rh dissolution was performed in HCl by applying alternating current. The commercially available AG-1X8, TK200, normal DGA, and branched DGA resins were tested for ¹⁰³Pd purification from the Rh bulk target material. The DGA resins were found to be the most convenient with high separation factors and quantitative ¹⁰³Pd elution in HCl solutions. The Rh could be recycled and used for electroplating new targets. Recycled Rh targets improved the molar activity of the ¹⁰³Pd produced. After two branched DGA columns, 87.2 ± 6.3 % of ¹⁰³Pd activity was recovered. ICP-OES analysis of the purified batches showed the presence of only few remaining impurities: 1.2 ± 0.3 nmol Pd, 0.4 ± 0.3 nmol Rh and traces of Al, Fe, and Zn. Finally, n.c.a. ¹⁰³Pd radiolabeling was demonstrated with the TETA chelator in acetate buffered solutions.