The invention provides a radioactivity local delivery system enabling the use of isotopes having a longer half life and having a lower energy. The invention also provides a radioactivity local delivery system enabling an easier and more efficient control of the dose/rate and total dose of local radiation delivery. The present invention utilizes a radioisotope coupled to a circulation time reducing agent such as a chelatin agent, the coupled radioisotope being in releasable association with the structure to be inserted in a vessel of a human patient. The coupled radioisotope can be part of the support itself or in releasable association therewith through the use of a biodegradable or non-biodegradable pharmaceutical carrier. Also provided is a method to decrease the growth of actively proliferating cells at a targeted site in a vessel of a human patient as well as compositions therefor.
