BackgroundRecently, significant interest in 44Sc as a tracer for positron emission tomography (PET) imaging has been observed. Unfortunately, the co-emission by 44Sc of high-energy γ rays (Eγ = 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—43Sc—having properties similar to 44Sc but is characterized by much lower energy of the concurrent gamma emissions. This work presents the production route of 43Sc by α irradiation of natural calcium, its separation and purification processes, and the labeling of [DOTA,Tyr3] octreotate (DOTATATE) bioconjugate.MethodsNatural CaCO3 and enriched [40Ca]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 μA. In order to find the optimum method for the separation of 43Sc from irradiated calcium targets, three processes previously developed for 44Sc were tested. Radiolabeling experiments were performed with DOTATATE radiobioconjugate, and the stability of the obtained 43Sc-DOTATATE was tested in human serum.ResultsStudies of natCaCO3 target irradiation by alpha particles show that the optimum alpha particle energies are in the range of 24–27 MeV, giving 102 MBq/μA/h of 43Sc radioactivity which creates the opportunity to produce several GBq of 43Sc. The separation experiments performed indicate that, as with 44Sc, due to the simplicity of the operations and because of the chemical purity of the 43Sc obtained, the best separation process is when UTEVA resin is used. The DOTATATE conjugate was labeled by the obtained 43Sc with a yield >98 % at elevated temperature.ConclusionsTens of GBq activities of 43Sc of high radionuclidic purity can be obtainable for clinical applications by irradiation of natural calcium with an alpha beam.

The internal α-particle beam of the Warsaw Heavy Ion Cyclotron was used to produce research quantities of the medically interesting Sc radioisotopes from natural Ca and K and isotopically enriched Ca targets. The targets were made of metallic calcium, calcium carbonate and potassium chloride. New data on the production yields and impurities generated during the target irradiations are presented for the positron emittersSc, Sc andSc. The different paths for the production of the long lived Sc/Sc in vivo generator, proposed by the ARRONAX team, using proton and deuteron beams as well as alpha-particle beams are discussed. Due to the larger angular momentum transfer in the formation of the compound nucleus in the case of the alpha particle induced reactions, the isomeric ratio of Sc/Sc at a bombarding energy of 29MeV is five times larger than previously determined for a deuteron beam and twenty times larger than for proton induced reactions on enriched CaCO targets. Therefore, formation of this generator via the alpha-particle route seems a very attractive way to form these isotopes. The experimental data presented here are compared with theoretical predictions made using the EMPIRE evaporation code. Reasonable agreement is generally observed.

The internal alpha particle beam of the heavy ion cyclotron operated by the Heavy Ion Laboratory (HIL) of the University of Warsaw has a maximum energy of 32 MeV and currently an intensity of up to 1 pµA. This beam is used by the HIL-University of Silesia collaboration for the production of research quantities of 211 At, 72 Se/ 72 As and 43,44 Sc radioisotopes. The produced activities are transported to the Institute of Nuclear Chemistry and Technology in Warsaw where research on therapeutic and imaging radiopharmaceuticals based on these radioisotopes is pursued.