Chemical properties

Tb-152 is a radiolanthanide, most often in trivalent state and chemically very similar to lutetium. The ionic radius of Tb³⁺ is 92 pm, i.e. just 7% larger than Lu³⁺, which explains that macrocyclic chelators suitable for Lu-177 can be directly employed for Tb-152 too, in particular DOTA, but also others .

Nuclear properties

Tb-152 decays by β⁺ decay (20.3%) or electron capture (79.7%) with a half-life of 17.5(1) hours to Gd-152. The mean positron energy is 1140(130) keV.

Tb-152 emits γ- and X-rays, notably a strong line of 63.5 % at 344.3 keV and about 52% at 43 (+/-1) keV). This makes Tb-152 a suitable isotope for PET imaging and possibly useful for 3-photon imaging.

Tb-152 emits few conversion and Auger electrons.

Production

Tb-152 is produced by high energy proton induced spallation of tantalum targets at the production facility MEDICIS at CERN. An off-line mass separation is performed at MEDICIS at CERN. The mass-separated ions are implanted into a solid matrix, e.g. a Zn or NaCl layer on a noble metal backing. The implanted layer can be dissolved and used for an additional radiochemical separation to obtain optimum radionuclidic purity by removing the pseudo-isobar Ce-136 that is mass-separated as oxide ion on mass 152.

Tb-152 is produced by spallation reaction in thick tantalum targets with protons of high energy . The radionuclides are released from the target by distillation and separated as implanted ions into zinc-coated gold foils . The isotope implanted collections undergo then a dissolution and separation step.

Distribution

Tb-152 implanted into a solid matrix will be shipped from MEDICIS (CERN, Geneva, Switzerland).

Examples of use

• Tb-152 is part of the terbium radionuclide quadruplet , and can thus offer interesting imaging capacity, notably for PET and possibly also 3-photon imaging. Its extended half-life allows to perform dosimetric and imaging studies over several days. It was in particular used with antibody fragments .
• A first in human PET/CT imaging was performed with Tb-152-DOTATOC over 24 hours , as well as with Tb-152-PSMA617 .