213Bi

Bismuth-213 (213Bi) is a radioactive isotope of bismuth with atomic number 83 and mass number 213. It decays predominantly by alpha emission to thallium-209, with a half-life of about 46 minutes. The emitted alpha particles have high linear energy transfer, delivering potent cytotoxicity over a short range in tissue. Because of these properties, 213Bi is studied for targeted alpha therapy.

Production and availability: 213Bi is typically obtained from a generator based on its parent nuclide actinium-225 (225Ac). 225Ac decays with a half-life of about 10 days through a chain that ultimately yields 213Bi, which can be eluted from the generator as needed. The short half-life of 213Bi requires rapid radiopharmaceutical preparation and administration.

Medical use: In radiopharmacy, 213Bi is attached to monoclonal antibodies or peptides that target cancer cells, creating a targeted alpha therapy (TAT). Applications have been explored in hematologic malignancies and solid tumors in clinical trials. The combination of a short half-life and high-LET alpha radiation enables strong tumor cell killing with potentially reduced dose to surrounding healthy tissue, but poses dosimetric and supply challenges.

Safety and regulatory status: Handling of 213Bi requires specialized radiopharmacy facilities and trained personnel due to alpha radiation, with internalization being the primary radiotoxicity risk. Production is limited by dependence on 225Ac availability, pharmaceutical development, and regulatory approvals, with ongoing research into dosimetry, pharmacokinetics, and clinical efficacy.