Restenosis, post-operative reclosure of the artery, affects approximately 30% of stent recipients subjected to dilatation of coronary blockages. Clinical exposure of the affected site to a very high dose from a radioactive source mounted at the tip of a catheter results in a significant reduction of restenosis rates. High energy gamma radiation from the current isotope of choice, Iridium-192, is, however, a safety concern for both the patient and personnel administering treatment. While substituting beta emitters for iridium reduces the risk of exposure to staff, energy deposited in tissue by beta rays diminishes rapidly with distance from the source, and is virtually extinguished in approximately 2 mm, making treatment of vascular walls difficult. Implant Sciences proposes to improve the safety of wire sources by pairing high-intensity, low-energy x- and gamma-ray emitting isotopes, specifically Iodine-125 and Ytterbium-169. Radiation from both penetrates tissue homogeneously and can be effectively used in treating cellular proliferation beginning in the media and extending to the adventitia. At the same time, unwanted exposure to nearby structures is greatly reduced, as is exposure to persons present in the operating room.
This effort is expected to show that iodine-125 and/or ytterbium-169 wire sources are, at the same time, both safe to use and effective restenosis inhibitors. Assuming this result, Implant Sciences Corporation will extend its iodine-125 brachytherapy seed production facilities to include the capacity for fabricating one or both of the proposed wire sources.
