Chemical properties

Sc-47 is a rare earth, usually in trivalent state. It can be radiolabelled with macrocyclic chelators, in particular DOTA, AAZTA and other chelators. The ionic radius is 74.5 pm.

Nuclear properties

Sc-47 decays by β^- emission with a half-life of 3.3492(6) days to stable Ti-47. It emits a low-energy β- spectrum with 162 keV average energy and 600 keV maximum energy. Emission of conversion and Auger electrons is negligible (<1%).

Moreover, Sc-47 emits γ rays at 159.4 keV (68.3%), suitable for SPECT imaging.

The mean electron energy emitted per decay is 162 keV, the mean photon energy per decay is 109 keV REF.

Production

Sc-47 is produced indirectly by thermal neutron irradiation of enriched Ca-46 oxide or carbonate targets in the research reactors of the PRISMAP+ network: RHF at ILL, BR2 at SCK CEN and MARIA at NCBJ. The Ca-47 (T_1/2=4.54 d) produced upon neutron capture decays to Sc-47 via β-minus decay and serves as a generator, allowing several subsequent elutions of Sc-47  REF,REF. With respect to other production pathways of Sc-47, this production scheme provides optimum radionuclidic purity and enables large-scale production  REF.

Alternatively, Sc-47 may be produced by high energy proton irradiation of titanium and vanadium targets with subsequent off-line mass separation at CERN-MEDICIS.

Distribution

The radiochemical separations of reactor-produced radionuclides are performed at POLATOM (NCBJ). Activity will be shipped from there to the users in the form of ScCl₃ solution, ready for labelling.

The mass-separated ions are implanted into a solid matrix, e.g. a NaCl layer on Al or Al layer on Au. The implanted layer can be dissolved and used directly, and an additional radiochemical separation can be used to obtain optimum radionuclidic and chemical purity. Radionuclides will be shipped from CERN-MEDICIS to the users in form of solution or in solid form, implanted into NaCl or Al metallic foil.

Examples of use

• See REF,REF for dosimetric calculations of Sc-47 in comparison to other β-minus emitters.
• Preclinicial bone scintigraphy with Sc-47 had been reported long ago REF.
• The preclinical SPECT imaging capabilities of Sc-47 have been demonstrated REF.
• The therapeutic efficacy of Sc-47-DOTA-folate has been compared preclinically with Lu-177-DOTA-folate and Y-90-DOTA-folate REF.
• Different Sc-47 labelled PSMA-ligands have been tested preclinically REF,REF.