Chemical properties

Sm-153 is a radiolanthanide, usually in trivalent state. It can be radiolabelled with macrocyclic chelators, in particular DOTA. The ionic radius is 95.8 pm.

Nuclear properties

Sm-153 decays by beta-minus emission with a half-life of 1.9285(2) days to stable Eu-153. It emits a low to medium energy beta spectrum with 225 keV average energy and 808 keV maximum energy. In addition to beta-minus emission it shows ample emission of low energy conversion and Auger electrons , thus emitting in total about 2.34 electrons (with energies above 4 keV) per decay.

Moreover, Sm-153 emits gamma-rays at 103.2 keV (29.14%) suitable for SPECT imaging.

The mean electron energy emitted per decay is 265 keV, the mean photon energy per decay is 62 keV .

Production

Sm-153 is produced by thermal neutron irradiation of enriched Sm-152 oxide targets in the BR2 reactor at SCK CEN. The produced carrier-added Sm-153 is then mass separated at the MEDICIS facility at CERN. Thus, Sm-153 with high specific activity is obtained .

Distribution

A final radiochemical separation is performed at SCK CEN (Mol, Belgium). Activity will be shipped from there to the users in form of SmCl₃ solution, ready for labelling of e.g. DOTA-compounds.

Examples of use

• c.a. Sm-153 with limited specific activity is mainly used for bone pain palliation, commercially available under the brand name Quadramet^®.
• The high-specific activity variant described here enables applications for receptor-targeted radionuclide therapy.
• Sm-153 is also suited as source for Mößbauer spectroscopy , a highly sensitive technique to characterize the chemical state and chemical environment of samarium bound in solids or frozen ex vivo samples.