Therapeutic principles
Alpha emitters are radioisotopes that emit an alpha particle during decay. By attaching the radioisotope to a molecule or monoclonal antibody that will “target” or seek out specific tumor cells in specific organs of the body, this alpha particle can be used to destroy tumor cells without harming normal cells in the body.
Alpha particles have a high linear energy transfer (LET) and short range in tissue: they release their high energy, and therefore create damage, over just a few cell diameters. They can therefore destroy tumor cells with minimal damage to surrounding healthy tissue.
As Bismuth-213 decays with a half-life of 46 minutes, no radioactivity remains in the patient a short time after the therapeutic dose is delivered. The Bi-213 decays to insignificant quantities of stable, non-toxic Bismuth-209. To permit the practical distribution of this product to health centers, a “generator” containing the parent radioisotope Ac-225, with a half-life of 10 days, is supplied every one or two weeks. From this generator, the Bismuth-213 final product is constantly replenished and can be extracted every few hours to produce the therapeutic dose.