Patent ID: 7530941

Claim:
A 169 Ytterbium radioactive source to be used for temporary brachytherapy which is encapsulated prior to activation in a material that does not contain unacceptable amounts of isotopes that, when irradiated by neutron flux, would be transmuted to radioactive isotopes that emit undesirable radiations for the treatment of tumors, or if transmuted into radioactive isotopes that emit undesirable radiations, have such short half-lives that they will have inconsequential activities shortly after irradiation, wherein the 169 Ytterbium radioactive source has an activity greater than 10 curies, has an activity concentration of at least 10 curies/mm 3 , has a density of at least 5 g/cm 3 , has a composition that is at least 50% by weight of ytterbium, and does not exhibit a significant amount of radioactive emission having an energy greater than 310 keV.