this invention involves radioactive medical devices for inhibiting an undesirable hyperplastic response in biological tissue , and a method for making the radioactive medical devices . in a first preferred embodiment , a medical device for inhibiting a hyperplastic response in biological tissue generally comprises polymeric hydrocarbon molecules forming the medical device and a salt or an acid of a radioactive isotope occluded within the polymeric hydrocarbon molecules . in a second preferred embodiment , the medical device comprises a thrombogenic sponge having a radioisotope trapped within the structure of the sponge . also in a preferred embodiment , a method of creating a medical device according to the present invention comprises : providing a first solvent in a container ; introducing a salt or an acid of a radioactive isotope into the first solvent ; introducing a second solvent into the first solution so as to form a second solution ; and introducing the medical device into the second solution , wherein the ionic components of the radioactive isotope migrate into the molecular structure of the medical device . in another aspect , a method of creating a medical device that inhibits a hyperplastic response in biological tissue comprises placing a salt or an acid of a radioactive isotope in a fluid and permitting the salt or acid to disassociate in solution , submersing the sponge in the solution and permitting the radioactive isotopes to become trapped in the structure of the sponge .