Cyclotron production of ^sup 43^Sc for PET imaging

Background Recently, significant interest in ^sup 44^Sc as a tracer for positron emission tomography (PET) imaging has been observed. Unfortunately, the co-emission by ^sup 44^Sc of high-energy γ rays (E ^sub γ^=1157, 1499 keV) causes a dangerous increase of the radiation dose to the patients and clinical staff. However, it is possible to produce another radionuclide of scandium--^sup 43^Sc--having properties similar to ^sup 44^Sc but is characterized by much lower energy of the concurrent gamma emissions. This work presents the production route of ^sup 43^Sc by [alpha] irradiation of natural calcium, its separation and purification processes, and the labeling of [DOTA,Tyr3] octreotate (DOTATATE) bioconjugate. Methods Natural CaCO3 and enriched [^sup 40^Ca]CaCO3 were irradiated with alpha particles for 1 h in an energy range of 14.8-30 MeV at a beam current of 0.5 or 0.25 [mu]A. In order to find the optimum method for the separation of ^sup 43^Sc from irradiated calcium targets, three processes previously developed for ^sup 44^Sc were tested. Radiolabeling experiments were performed with DOTATATE radiobioconjugate, and the stability of the obtained ^sup 43^Sc-DOTATATE was tested in human serum. Results Studies of ^sup nat^CaCO3 target irradiation by alpha particles show that the optimum alpha particle energies are in the range of 24-27 MeV, giving 102 MBq/[mu]A/h of ^sup 43^Sc radioactivity which creates the opportunity to produce several GBq of ^sup 43^Sc. The separation experiments performed indicate that, as with ^sup 44^Sc, due to the simplicity of the operations and because of the chemical purity of the ^sup 43^Sc obtained, the best separation process is when UTEVA resin is used. The DOTATATE conjugate was labeled by the obtained ^sup 43^Sc with a yield >98 % at elevated temperature. Conclusions Tens of GBq activities of ^sup 43^Sc of high radionuclidic purity can be obtainable for clinical applications by irradiation of natural calcium with an alpha beam.