Chemical properties
Tb-149 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-149 too, in particular DOTA.
Nuclear properties
Tb-149 decays with a half-life of 4.118(25) hours by 16.7% alpha emission (3967 keV alphas) to Eu-145 (T1/2=5.9 d). Moreover, Tb-149 decays by beta-plus emission (7.1(3)%) and electron capture (76.2%) to Gd-149 (T1/2=5.9 d). It emits a medium energy positron spectrum with 730 keV average energy and 2450 keV maximum energy.
Moreover, Tb-149 emits gamma-rays at 165.0 keV (26.4%), 352.2 keV (29.4%), 388.6 keV (18.4%), 652.1 keV (16.2%), 853.4 keV (15.5%), etc.
The mean alpha energy emitted per decay is 662 keV, the mean alpha recoil energy 18 keV, the mean electron energy emitted per decay is 84 keV and the mean photon energy per decay is 1286 keV .
Production
Tb-149 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 can be dissolved and used for an additional radiochemical separation to obtain optimum radionuclidic purity by removing the pseudo-isobars Ce-133, Ce-133m, La-133 that are mass-separated as oxide ions on mass 149.
Distribution
Tb-149 implanted into a solid matrix will be shipped from MEDICIS (CERN, Geneva, Switzerland). To minimize decay losses during shipping, experiments with Tb-149 are best performed at the medical facility AGORA (CHUV, Lausanne, Switzerland).
Examples of use
| Parameter | Specifications |
|---|---|
| Half-life | 4.12 h |
| Daughter | Gd-149 (T1/2=9.3 d): 15 mBq per 1 Bq Tb-149 Eu-145 (T1/2=5.9 d): 4.8 mBq per 1 Bq Tb-149 |
| Branching Ratio/Decay | 16.7% α, 7.1% β+, 76.2% EC |
| Production | Ta(p,spallation) |
| Purification | Off-line mass separation |
| Chemical Form | implanted in solid layer |
| Specific Activity | n.a. |
| Radionuclidic Purity | n.a. |
| Radiochemical Purity | Radiolabelling test required |
| Chemical Purity | n.a. |
| Identification | Presence of 165.0 keV, 352.2 keV and 388.6 keV gamma lines |
| Appearance | n.a. |
| pH | n.a. |
| Activity available | t.b.d., under commissioning |
| Availability | Few times per year (planning in advance) |
| Grade | research grade, n.c.a. |
| Other information | Implanted in Al, Zn or NaCl layer on Au foil |