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.
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.
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.
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
|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|
|Purification||Off-line mass separation|
|Chemical Form||implanted in solid layer|
|Radiochemical Purity||Radiolabelling test required|
|Identification||Presence of 165.0 keV, 352.2 keV and 388.6 keV gamma lines|
|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|