Cyclotron production of ⁴³Sc and ⁴⁴gSc from enriched ⁴²CaO, ⁴³CaO, and ⁴⁴CaO targets

Introduction: Sc-43 and Sc-44g are both positron-emitting radioisotopes of scandium with suitable half-lives and favorable positron energies for clinical positron emission tomography (PET) imaging. Irradiation of isotopically enriched calcium targets has higher cross sections compared to titanium targets and higher radionuclidic purity and cross sections than natural calcium targets for reaction routes possible on small cyclotrons capable of accelerating protons and deuterons. Methods: In this work, we investigate the following production routes via proton and deuteron bombardment on CaCO3 and CaO target materials: Ca-42(d,n)Sc-43, Ca-43(p,n)Sc-43, Ca-43(d,n)Sc-44g, Ca-44(p,n)Sc-44g, and Ca-44(p,2n)Sc-43. Radiochemical isolation of the produced radioscandium was performed with extraction chromatography using branched DGA resin and apparent molar activity was measured with the chelator DOTA. The imaging performance of Sc-43 and Sc-44g was compared with F-18, Ga-68, and Cu-64 on two clinical PET/CT scanners. Discussion: The results of this work demonstrate that proton and deuteron bombardment of isotopically enriched CaO targets produce high yield and high radionuclidic purity Sc-43 and Sc-44g. Laboratory capabilities, circumstances, and budgets are likely to dictate which reaction route and radioisotope of scandium is chosen.