Tb 155
5.3 d
γ 87, 105, 180...

Chemical properties

Tb-155 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-155 too, in particular DOTA, but also others. Also radiolabelling of heat-sensitive molecules with Tb radionuclides has been reported .

Nuclear properties

Tb-155 decays by electron-capture with a half-life of 5.32(6) days to stable Gd-155. Its half-life of several days is close to the physical half-life of the therapeutic Tb-161 radiolanthanide and of Lu-177, therefore allowing for extended imaging studies.

Tb-155 emits low energy conversion and Auger electrons with an average of 2.0 electrons (with energies above 4 keV) per decay.

Tb-155 emits γ- and X-rays, notably 107(1) % around 45(+/-11%) keV, and 32.0(18) % at 86.6 keV and 25.1% at 105.3 keV . These make Tb-155  suitable for SPECT-imaging.

The mean electron energy emitted per decay is 38 keV, the mean photon energy per decay is 175 keV.


Tb-155 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. an Al, Zn or NaCl layer on a noble metal backing. The implanted layer is then dissolved and used for an additional radiochemical separation to obtain optimum radionuclidic purity by removing the pseudo-isobar Ce-139 that is mass-separated as oxide ions on mass 155.


Radiochemical separations are performed at the PRISMAP production facilities PSI SINQ and Injector 2 (PSI, Villigen, Switzerland), BR2 (SCK CEN, Mol, Belgium) or MARIA (NCBJ, Otwock-Swierk, Poland). Activity will be shipped from one of these locations to the users in form of TbCl3 solution, ready for labelling of e.g. DOTA-compounds.

Radiochemical separations is performed directly at MEDICIS at CERN, Switzerland. Activity will be shipped from there in form of TbCl3 solution, ready for labelling of e.g. DOTA-compounds.

Examples of use

  • Tb-155 is part of the terbium radionuclide quadruplet , and can offer SPECT imaging capacity over extended periods, notably for peptides and antibodies .

Purity grades available


No carrier added (n.c.a.)

Production routeTa(p,spallation) or Gd(p,X)
DaughterDecays to stable Gd-155: 100% EC
Half-life5.3 d
ProcessingOff-line mass separation + 2-step column separation
Primary Container
Product Graden.c.a.
Physical FormSolid
Chemical FormImplanted in solid layer
Radioactive Concentration (gamma spectrometry)n.a.
Radionuclide identification (gamma spectrometry)87 keV, 105 keV and 180 keV gamma lines present
Radionuclidic Purity (gamma spectrometry)t.b.d.
Chemical purity (ICP-OES)n.a.
Molar activity (ICP-OES)n.a.
Apparent Molar Activityn.a.
Microbiological qualityn.a.
Bacterial endotoxinn.a.
pH (pH strips)n.a.
Additional information
Activity availablet.b.d. (under commissioning) few times per year
Activity limit for UN2910 (excepted package) shipment20 MBq in dry state or 2 MBq in liquid form
Other informationResearch grade implanted (with >10% Ce-139) in Al, Zn or NaCl layer on Au foil also possible



Point of supply

  • Geneva, Switzerland

Involved production facilities

CERN, International