ORNL, a Department of Energy (DOE) multiprogram facility, has developed the production, processing and delivery system to provide a radioisotope researchers believe will make coronary angioplasty more effective at unclogging coronary arteries. Columbia University offers the clinical expertise and is performing studies that could clear the way for an improvement of a procedure performed annually on 400,000 people in the United States.
Of those patients, about 30 percent need additional angioplasty or heart bypass surgery because the arteries become reclogged, often within six months. Nationally, this adds $1 billion to the $4 billion cost of the initial angioplasty procedures.
Cardiology researchers at Columbia have demonstrated that they can use low doses of radiation to inhibit restenosis - the reclogging of coronary arteries. Low doses of radiation inhibit the rapid proliferation of smooth muscle cells that can form inside the newly unclogged arteries.
The challenge in using radiation is identifying the best radioisotope that has the desired radioactive decay properties, is routinely available and cost effective, said Russ Knapp, group leader of Nuclear Medicine at ORNL.
"The method being studied for delivering the radiation dose uses a tiny filament attached to the end of a flexible wire that a doctor threads through the coronary artery that has been unblocked by previous inflation of a tiny balloon," Knapp said. "With this technique, radiation dosages can vary according to where the wire is as it's guided through the artery." Another major drawback is that the manufacturing process is time-consuming and very expensive.
Columbia University's Judah Weinberger, an interventional cardiologist and associate professor of clinical medicine, came up with the idea of using a solution of a radioisotope to inflate the balloon. The balloon, inflated with a saline solution, enlarges the artery and allows blood to flow more freely. Weinberger suggested the balloon could do both - unclog the artery and deliver a low dose of radiation to prevent restenosis. All the cardiologist needed was the perfect radioisotope, so Weinberger called Knapp, who has done extensive research on medical uses of radioisotopes.
"I suggested that they consider rhenium-188," Knapp said, "because it is readily available from a generator system that we have developed for hospital use and has excellent radiation properties for this application."
Weinberger suggested a chemical for inflation of the isotope that would deal with a worst-case scenario.
"If the balloon containing the saline and rhenium-188 were to break, the radioisotope is simply expelled in the urine, causing no harm to the patient," Weinberger said.
In addition to identifying the ideal radioisotope, ORNL is providing to Columbia University the radioisotope generator and concentration methods for delivering the proper dose of rhenium-188.
After testing with animals at Columbia University, the next step is obtaining Food and Drug Administration approval to test the technique on patients. If all goes well, the radiation angioplasty technique could be in use within a few years.
"This is a perfect example of how basic research at a national laboratory, combined with clinical studies available at a school of medicine, can lead to something that can benefit thousands of people and improve their quality of life," Knapp said.
ORNL, one of DOE's multiprogram research facilities, is managed by Lockheed Martin Energy Research Corp.