Chemical properties

Ra-223 is usually in divalent state.

Nuclear properties

Ra-223 decays with by ɑ decay with a half-life of 11.43(5) days. Its decay chain involving Rn-219 (T_1/2 = 4 s), Po-215 (T_1/2 = 1.8 ms), Pb-211 (T_1/2 = 36 min), Bi-211 (T_1/2 = 2.2 min) and Tl-207 (T_1/2 = 4.8 min) leads to stable Pb-207. Including its short-lived decay chain, the cumulative ɑ emission is 400% per Ra-223 decay.

Ra-223 emits X rays from 81 to 98 keV (49.6%) and γ rays, notably 269 keV (13.3%), its daughter Rn-219 emits γ rays at 271 keV (10.8%) and Bi-211 emits γ rays at 351 keV (13%). These are the principal photon emissions of the decay chain that enable SPECT-imaging REF,REF.

Production

Ra-223 is produced by high energy proton induced spallation of thorium targets with subsequent off-line mass separation at CERN MEDICIS facility. The mass-separated ions are implanted into a solid matrix, e.g., a NaCl layer on Al or Al layer on Au metal backing.
The implanted layer can be dissolved and used directly, but an additional radiochemical separation can be used to obtain optimum radionuclidic and chemical purity.

Distribution

Ra-223 in solid form, implanted in foil form can be shipped from CERN.

Examples of use

• The main application of Ra-223 is as free Ra²⁺ ions, that act, analogously to Ca²⁺, as bone seekers. Administered as Ra-223 chloride under the product name Xofigo®, it is used for targeted therapy of bone metastases of metastatic prostate cancer REF.
• Stable chelation of Ra²⁺ with the chelator macropa has been reported REF.
• Encapsulation of Ra-223 in liposomes REF or radiolabeled nanoparticles REF,REF is being investigated.