Chemical properties

Scandium is a rare earth element, normally present in solution in oxidation state III with ionic radius of 74.5 pm. Sc-43 can be radiolabelled with macrocyclic chelators, e.g., DOTA, or with other chelators such as NODAGA, AAZTA, H4pypa or H3mpatcn REF,REF,REF,REF,REF.

Nuclear properties

Sc-44 decays by β⁺ decay (94.27(5)%) and electron capture (5.73%) with a half-life of 4.042(25) hours REF to stable Ca-44. It emits a medium-energy positron spectrum with 632 keV average energy and 1474 keV maximum energy.

Moreover, Sc-44 emits a hard γ-ray at 1157.0 keV (99.9%) in prompt coincidence (T_1/2=2.7 ps) with every emitted positron.

The mean electron energy emitted per decay is 596 keV, the mean photon energy per decay is 2136 keV REF.

Production

Sc-44 is produced by proton irradiation of enriched Ca-44 oxide (or carbonate) targets at CRR at IFIN-HH (TR19) or at the C30 cyclotron at NCBJ.

Distribution

The radiochemical separations are performed at CRR (IFIN-HH, Magurele, Romania) or POLATOM (NCBJ, Otwock, Poland). Activity will be shipped from these facilities to the users in the form of ScCl₃ (or acetate) solution, ready for radiolabelling.

Examples of use

• Sc-44 has been evaluated preclinically with peptides, PSMA ligands, affibodies and monoclonal antibodies REF,REF,REF,REF.
• Settings of commercial activity meters have been evaluated with Sc-44 REF.
• The preclinical PET imaging performance of Sc-44 has been compared to other positron emitters REF,REF.
• The impact of the prompt γ-ray emission on quantification with preclinical and clinical scanners has been evaluated REF.