Canadian team develops method to make medical isotope sans reactor
Cyclotron process could alleviate hospitals’ dependence on shaky supply from Chalk River and other such reactors.
Vancouver – A team of scientists led by Canada’s national laboratory for particle and nuclear physics, TRIUMF, have announced that they successfully produced a key medical isotope, technetium-99m (Tc-99m), using cyclotrons already available in Ontario and British Columbia hospitals.
“Making medical isotopes in hospitals instead of nuclear reactors is a major milestone for diagnostic imaging for patients in Canada and around the world,” says Paul Schaffer, head of TRIUMF’s Nuclear Medicine Division and one of the team leaders. “We took the principles of physics, chemistry and engineering that people have known for years, and used them to write a recipe for upgrading a cyclotron so it could be used to make technetium-99m. We’ve just completed using that recipe on machines in both Ontario and BC.”
According to the nuclear lab, Technetium-99m (Tc-99m) is the world’s most highly used medical isotope and is the critical component in more than 76,000 imaging procedures per day. The problem is that two ageing nuclear reactors produce about three quarters of the global supply, particularly the NRU reactor in Chalk River.
In the past few years, both reactors have suffered maintenance and repair outages, threatening the global supply of medical isotopes. In 2007, a shutdown of the Chalk River reactor caused a world-wide shortage of the most commonly used isotopes. Most recently, a 15-month shut down of the 55-year-old Chalk River reactor in 2009/10 prompted the Canadian government to dedicated $35 million toward finding alternate sources for medical isotopes.
One of the results is TRIUMF’s modified cyclotron process. Commonly used for producing other medical isotopes like Fluorine-18 or Carbon-11, these modified particle accelerators produce Tc-99m by accelerating hydrogen ions to a prerequisite energy and then directing them onto targets of enriched molybdenum-100 (Mo-100).
As the hydrogen ions are extracted from the cyclotron, the electrons are stripped off, creating a stream of protons. The protons collide with the molybdenum causing a portion of the Mo-100 to transmute into Tc-99m. The target material is then dissolved in a liquid solution and passed through an ion-exchange column to separate the Tc-99m from the bulk target material. According to TRIUMF, the chemical form of Tc-99m isolated using this method is identical to that obtained from the reactor-based process.
“One of these cyclotrons can supply a metro area such as Vancouver and there are more than a dozen of these cyclotrons in hospitals across Canada,” says Tom Ruth, senior scientist at TRIUMF and the BC Cancer Agency and principal investigator for the team. “What we’ve shown is that a decentralized model for producing technetium is now possible. We are in discussions with several industrial partners and regional health authorities about how to start implementing this vision.”