Bi-213 vapor phase generator

Bi-213 is a radioactive isotope being evaluated for a variety of cancer therapies. Tissue-specific monoclonal antibodies are used to deliver the isotope to the cancer site, where alpha particles generated during the radioactive decay kill the cancerous cells. Bi-213 has many characteristics that are advantageous for alpha emitting isotopes, namely; a high ratio of alpha emissions relative to beta and gamma emissions, chemical characteristics suitable for attachment to monoclonal antibodies, and a relatively short half-life. What is currently lacking is a reliable, hospital-ready separations process for the preparation of Bi-213 from its parent isotope Ac-225. Current ion exchange processes are subject to radiolysis, which limits the capacity and shelf-life of the generator.

This study investigated the use of a high temperature vacuum process to produce Bi-213 from an Ac-225 generator. A prototype filament apparatus was tested using Ac-225 in the activity range of 10-20 μCi; yields up to 85% were achieved with a one-hour operation. A process window for both temperature and time was determined, such that contamination from the Ac-225 parent material was kept below 0.03%.