47Sc and 46Sc cross-section measurement for an optimized 47Sc production with an 18 MeV medical PET cyclotron

Abstract

The availability of novel radionuclides plays a fundamental role in the development of personalized nuclear medicine. In particular, there is growing interest in pairs formed by two radioisotopes of the same element, the so-called true theranostic pairs, such as ^61,64Cu/⁶⁷Cu, ^43,44Sc/⁴⁷Sc and ¹⁵⁵Tb/^149,161Tb. In this case, the two radionuclides have identical kinetics and chemical reactivity, allowing to predict whether the patient will benefit from a therapeutic treatment on the basis of nuclear imaging data. ⁴⁷Sc [t_1/2 = 3.349 d, E [Formula: see text] = 440.9 keV (68.4%); 600.3 keV (31.6%), E_γ = 159.4 keV (68.3%)] is a promising radionuclide for theranostic applications in nuclear medicine. Its physical characteristics make it suitable for radionuclide therapy and allow SPECT imaging during treatment. Moreover, ⁴⁷Sc is foreseen as the therapeutic partner of the β⁺-emitters ⁴³Sc and ⁴⁴Sc, both under study for PET imaging, opening new avenues towards the true theranostics concept. ⁴⁷Sc can be produced by proton irradiation of an enriched ⁵⁰Ti oxide target with a medical cyclotron equipped with a solid target station. To optimize the production yield and the radionuclidic purity, an accurate knowledge of the production cross sections is necessary. In this paper, we report on measurements of the production cross section of ⁴⁷Sc and ⁴⁶Sc using enriched ⁵⁰Ti titanium oxide targets, performed at the Bern University Hospital cyclotron laboratory. On the basis of the obtained results, a study of the production yield and purity was performed to assess the optimal irradiation conditions. A production test was also carried out to confirm these findings.