ARCHIVED - Solving Canada's medical isotope crisis
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January 24, 2011— Ottawa, Ontario
Canadian researchers are racing to perfect a safe, clean, inexpensive and reliable method for making isotopes used in medical imaging and diagnostic procedures. The new method does not require a nuclear reactor and could therefore eliminate future shortages of technetium-99m — the most widely used medical isotope today.
What are isotopes?
Isotopes are atoms of the same element with different numbers of neutrons in their nuclei. Stable isotopes do not change over time. However, atoms of unstable isotopes — called radioisotopes — change into other elements over time through radioactive decay.
Why is technetium-99m the radioisotope of choice for medical imaging?
Compared to other radioactive isotopes, Tc-99m is best suited for medical imaging as it emits a high energy gamma ray that can penetrate human tissue and be registered by detectors with high efficiency allowing for clear images. It also has a half-life of only 6 hours, which allows enough time for medical staff to collect the data but keep the patient's radiation exposure low. (A half life is the period of time it takes for a radioactive substance undergoing decay to decrease by half.)
Until recently, the National Research Universal (NRU) reactor at Chalk River produced almost 50 percent of the world's supply of medical isotopes. Then in May 2009, the NRU was shut down for repairs. This halt in operations, combined with several delays in its restart, contributed to a global isotopes shortage. While the NRU reactor has been back in operation since August 2010, it is expected to cease isotope production by 2016. This means it’s time to develop new methods that offer a more secure and sustainable supply of isotopes.
Last June, the Government of Canada announced a $35 million program to promote research into alternative methods for producing medical isotopes. Backed by NRC and other collaborators, the Canadian Light Source submitted one of four successful proposals under this research program to explore the technical and economic feasibility of using an electron linear accelerator to produce molybdenum-99 (Mo-99) — the “parent isotope” of technetium-99m (Tc-99m). Their proposal builds on research by the Idaho National Laboratory and a suggestion by Ottawa-based Mevex Corporation.
Scientists at the NRC Institute for National Measurement Standards (NRC-INMS) have already tested every step of the linear accelerator method. The research partners expect this method could ultimately make enough isotopes to supply all of Canada’s requirements.
According to Dr. Carl Ross, who leads the NRC-INMS team, the new method doesn’t pose any security or nuclear proliferation concerns because, unlike a nuclear reactor, it requires no weapons-grade uranium. What’s more, it generates virtually no radioactive waste materials that must be stored indefinitely. “Using a linear accelerator, you essentially produce only the isotope that you want, so there is negligible waste,”, he says.
“The linear accelerator method is virtually guaranteed to replace the nuclear reactor production method, ” adds Dr. Ross. “The physics is well established. The chemistry of separation is well known. So I don’t really see any impediment to it being successful.”
In the new method, a high energy linear accelerator bombards coin-sized discs of the stable isotope molybdenum-100 with X-rays, to produce radioactive molybdenum-99. Molybdenum-99, with a half-life of 66 hours, soon decays into the desired technetium-99m, which is used in some 5500 diagnostic procedures in Canada every day. Tc-99m can then be separated from Mo-99 using technology developed by U.S.-based NorthStar Medical Radioisotopes.
Over the next two years, NRC will work with its collaborators to develop a manufacturing process. A demonstration facility will be constructed at the Canadian Light Source in Saskatoon to prove that a high-power electron accelerator can produce a significant fraction of the medical isotopes required by nuclear pharmacies across the country.
“It is very fulfilling to work on a project that can have an immediate impact on our lives,” says Dr. Ross.
- Canadian Light Source
- TRIUMF team to play role in developing isotopes with accelerators
- Government of Canada Investing in Isotope Innovation
- Canadian-led team aims to produce medical isotopes without nuclear reactor
- Producing medical isotopes using X-rays
Enquiries: Media relations
National Research Council of Canada
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