44Sc production from enriched 47TiO2 targets with a medical cyclotron

Sc-44 is a beta(+)-emitter which has been extensively studied for nuclear medicine applications. Its promising decay characteristics [t(1/2) = 3.97 h, E beta+ = 632 keV (94.3%), E-gamma = 1157 keV (99.9%); 1499 keV (0.91%)] make it highly attractive for clinical PET imaging, offering an alternative to the widely used Ga-68 [t(1/2) = 67.7 min, E beta+ = 836 keV (87.7%)]. Notably, its nearly fourfold longer half-life opens avenues for applications with biomolecules having extended biological half-lives and enables the centralized distribution of Sc-44 radiopharmaceuticals. An additional advantage of employing Sc-44 as a diagnostic radioisotope lies in its counterpart, the beta(-)-emitter Sc-47, which is currently under investigation for targeted radiotherapy. Together, they form an ideal theranostic pair, providing a comprehensive solution for both diagnostic imaging and therapeutic applications in nuclear medicine. At the Bern medical cyclotron, a study to optimize the production of scandium radioisotopes is currently ongoing. In this context, proton irradiation of titanium targets has been investigated, exploiting the reactions Ti-47(p,alpha)Sc-44 and Ti-50(p,alpha)Sc-47. This approach enables the production of Sc radioisotopes within a single PET medical cyclotron facility, employing identical chemical procedures for target preparation and post-irradiation processing. In this paper, we report on cross-section measurements of the Ti-47(p,alpha)Sc-44 nuclear reaction using 95.7% enriched (TiO2)-Ti-47 targets. On the basis of the obtained results, the production yield and purity were calculated to assess the optimal irradiation conditions. Production tests were performed to confirm these findings.