At 211
7.2 h
ε
α 5,867...
γ (687)

Chemical properties

In the periodic table astatine is situated at the boundary of halogens and metalloids, i.e. partly behaves like a halogen and partly like a metal. This requires dedicated labelling strategies .

Nuclear properties

At-211 decays with 7.214(7) h half-life. It decays by 58.2% electron capture to short-lived Po-211 (T1/2 = 0.516(3) s) that decays in turn with 100% alpha emission to stable Pb-207. Moreover, At-211 decays by 41.8% alpha emission to quasi-stable Bi-207 (T1/2=31.6 years; only 26 Bq Bi-207 per 1 MBq of At-211 after decay of the latter) that decays in turn to stable Pb-207. Including its short-lived Po-211 daughter, the cumulative alpha emission is 100% per At-211 decay with an average alpha energy of 6.78 MeV.

At-211 emits X-rays, notably Kα at ≈78 keV (33.1(5)%) and Kβ at ≈90 keV (9.06(5)%). These energies enable SPECT-imaging, preferably with medium energy collimators .

Moreover, At-211 and its daughter Po-211 in equilibrium emit weak gamma-rays at 567.7 keV (0.31%), 687.0 keV (0.26%) and 897.8 keV (0.32%).

The mean alpha energy per decay is 6785 keV, the mean recoil energy (of Bi-207 or Pb-207 recoils respectively) is 131 keV, the mean electron energy per decay is 3 keV, and the mean photon energy per decay is 43 keV.

Production

At-211 is produced by alpha particle irradiation of metallic Bi-209 targets at the cyclotron ARRONAX.

Distribution

The radiochemical separation is performed at ARRONAX (ARRONAX, Nantes, France) and activity will be shipped from there to the users.

Examples of use

  • Clinical trials with At-211-radioimmunotherapy have been performed in the past and are ongoing.

Purity grades available

preclinical

No carrier added (n.c.a.)

Yes
ParameterSpecifications
Half-life7.214 h
DaughterPo-211 which decays immediately (T1/2=0.5 s) to stable Pb-207 (stable) and Bi-207 that is quasi-stable (T1/2=31.6 y).
Branching Ratio/Decay41.8 % α, then EC at 100%
58.2% EC, then α at 100%
ProductionBi-209(α,2n) At-211
PurificationDry extraction
Chemical FormChloroform
Specific Activityn.a.
Radionuclidic PurityAt-210/At-211 < 0.5%
Radiochemical Purityt.b.d.
Identification569.7 keV, 687.0 keV and 897.8 keV gamma lines present
AppearanceClear and colourless solution
pHn.a.
Activity availableTens of MBq
AvailabilityOn demand
GradePreclinical grade, n.c.a.
Other informationTransport to be discussed.

Applications

  • α-therapy

Point of supply

  • Nantes, France

Involved production facilities

ARRONAX, France