Developments toward the Implementation of Sc Production at a Medical Cyclotron.

Sc has favorable properties for cancer diagnosis using Positron Emission Tomography (PET) making it a promising candidate for application in nuclear medicine. The implementation of its production with existing compact medical cyclotrons would mean the next essential milestone in the development of this radionuclide. While the production and application of Sc has been comprehensively investigated, the development of specific targetry and irradiation methods is of paramount importance. As a result, the target was optimized for the Ca(p,n)Sc nuclear reaction using CaO instead of CaCO, ensuring decrease in target radioactive degassing during irradiation and increased radionuclidic yield. Irradiations were performed at the research cyclotron at the Paul Scherrer Institute (~11 MeV, 50 µA, 90 min) and the medical cyclotron at the University of Bern (~13 MeV, 10 µA, 240 min), with yields varying from 200 MBq to 16 GBq. The development of targetry, chemical separation as well as the practical issues and implications of irradiations, are analyzed and discussed. As a proof-of-concept study, the Sc produced at the medical cyclotron was used for a preclinical study using a previously developed albumin-binding prostate-specific membrane antigen (PSMA) ligand. This work demonstrates the feasibility to produce Sc with high yields and radionuclidic purity using a medical cyclotron, equipped with a commercial solid target station.