Los Alamos National Laboratory
Gary Kliewer, (505) 665-2085/[email protected]
LOS ALAMOS TAKES PART IN INTERNATIONAL RACE TO PROVIDE MEDICAL ISOTOPES
LOS ALAMOS, N.M., April 29, 1997 -- A novel collaboration between Los Alamos National Laboratory, U.S. industry and a Russian nuclear research institute has produced a rare radioisotope needed for certain medical diagnostics. The three-way deal keeps Russian nuclear materials experts employed on non-military projects, serves an important medical need, and paves the way for production of other radioisotopes with medical and commercial potential.
Earlier this month, the first shipment of irradiated metal used to produce a radioisotope now in short supply but needed for diagnosis of heart disease arrived at Los Alamos from Russia. Processed at Los Alamos' Radioisotopes and Analytical Resource laboratory within a week, the first two batches of the resulting isotope, strontium-82, then were shipped to Bristol-Myers Squibb in New Jersey where they will be prepared for certification by the Food and Drug Administration.
"The collaboration is making a significant contribution to our nuclear nonproliferation goals," said Los Alamos project leader Dennis Phillips. "And it also will benefit the medical field, which in turn has a commercial potential."
Strontium-82 decays to rubidium-82, used in positron emission tomography, or PET, a common medical imaging technology. Rubidium-82 emits radiation that can be "seen" by special cameras to produce internal pictures.
Los Alamos and Brookhaven national laboratories produce strontium-82, but cannot guarantee a year-round supply for medical applications. Some strontium-82 is supplied by Canada. But after these first samples from the Russian institute are certified by the FDA, hospitals may look forward to having their demands for the isotope met throughout the year.
Extraordinary teamwork is required to successfully run the gauntlet of import and shipping procedures, complete the chemical processing of the radioactive substance and get the material to hospitals in a form they can use. It is also a race around the world against the unrelenting decay-rate of the radioisotope itself: each passing day, another 3 percent of the valuable material is gone.
The race begins at the Institute of Nuclear Research in Troitsk, Russia, where a particle accelerator the Russians designed for medium energy physics experiments is used to irradiate a small block of rubidium metal called a "target." The Russian scientists received the official export license just a day before the first two targets had to be shipped.
Technology Commercialization International, a small company in Albuquerque, N.M., represents the Institute of Nuclear Research in the United States. TCI, which manages a number of joint ventures and partnerships with Russian institutes, assisted with importing the rubidium targets. TCI and Los Alamos received a grant for the program from the United States Industry Coalition, Inc. USIC's purpose is to support partnerships involving U.S. industry, universities, national laboratories and institutes in the former Soviet Union that prevent and reduce proliferation of weapons of mass destruction. USIC works to redirect the skills and activities of FSU scientists and engineers engaged in nuclear weapons work to peaceful pursuits.
Transporting the irradiated material requires extraordinary precautions. Custom shipping casks were built to safely transport the targets. Made of lead and stainless steel and nested inside a 30-gallon drum, each cask weighs 785 pounds. The target is a candybar-sized metal frame that holds the irradiated material inside. After the chemical procedures, the Los Alamos scientists end up with a precious 13 millionths of a gram of strontium-82.
The Los Alamos team adapted the chemical procedure developed by the Russian researchers, who have more experience working with this particular target material. The elaborate chemical extraction process must be done in a radiation-proof chamber. All manipulations are performed with remote mechanical arms behind 18-inch-thick leaded glass windows.
"The Russians weren't sure we could do it using our approach and processing facilities, which differed markedly from those in Russia," said Phillips. From Los Alamos, the strontium-82 was forwarded to Bristol-Myers Squibb. The pharmaceutical company mounts the isotope on another material to produce a "generator" that hospitals purchase and use for PET scans.
Bristol-Myers Squibb produces generators monthly for major cardiac care facilities around the country. Generators can be repeatedly "milked" for the imaging isotope, rubidium-82. The generator system allows for very quick tests, including studies in succession of a patient's heart at rest and under stress.
During the PET scan procedure, the rubidium-82 is removed from the generator through ion exchange by a normal saline solution and infused directly into a patient.
In the bloodstream, rubidium-82 mimics potassium. Because the heart uses a lot of potassium to do its job, it quickly extracts potassium -- and rubidium-82 -- from the blood. So the isotope collects in and around the heart. Then the PET scan reveals places where rubidium-82 piles up. The result is a three- dimensional image of the heart that shows places where circulation is abnormal or blocked. The rubidium-82 decays quickly, so in about 10 minutes the radioactivity in the patient is essentially gone.
Importing strontium-82 is in part a dress rehearsal for the joint manufacture of another radioisotope with broad medical and commercial potential, said Phillips. Selenium-72 is a short-lived isotope that may work well in a PET generator system. The Russian institute will be the primary source of selenium-72. Nonproliferation experts hope that isotope production will be a commercial success for Troitsk, thereby helping keep the Russian scientists employed in peaceful applications of nuclear chemistry.
Selenium-72 could make possible a broad new array of medical imaging applications. Selenium-72 decays to arsenic-72, an isotope that lasts just long enough to localize in diseased tissues to produce PET images, without lingering long enough to do significant radiological damage. It could be linked to an array of compounds that collect in specific parts of the body, including the brain or bones. TCI intends to develop the market for arsenic-72 as a new tool for cancer research and diagnostics.
The Department of Energy's Initiatives for Proliferation Prevention program considers this collaboration with the Institute of Nuclear Research, a member of the Russian Academy of Sciences, to be a big step towards incorporating the institute into the global isotope market and keeping its doors open.
Los Alamos National Laboratory is operated by the University of California for the U.S. Department of Energy.
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