Indirect Production of No Carrier Added (NCA) <sup>177</sup>Lu from Irradiation of Enriched <sup>176</sup>Yb: Options for Ytterbium/Lutetium Separation

This article presents a concise review of the production of no-carrier-added (NCA) 177Lu by the 'indirect' route by irradiating ytterbium-176 (176Yb)-enriched targets. The success of this production method depends on the ability to separate the microscopic amounts of NCA 177Lu from bulk irradiated ytterbium targets. The presence of Yb+3 from the target in the final processed 177Lu will adversely affect the quality of 177Lu by decreasing the specific activity and competing with Lu+3 complexation since ytterbium will follow the same coordination chemistry. Ytterbium and lutetium are adjacent members of the lanthanide family with very similar chemical properties which makes the separation of one from the other a challenging task. This review provides a summary of the methods developed for the separation and purification of NCA 177Lu from neutron irradiated 176Yb-enriched targets, a critical assessment of recent developments and a discussion of the current status of this 177Lu production method. Keywords: Electro-amalgamation, Extraction chromatography (EXC), Neutron irradiation, No carrier added (NCA) 177Lu, Peptide receptor radionuclide therapy (PRRT), Separation.