Posted on behalf of Hannah Hoag
The Canadian government is making a move to stop using nuclear reactors to produce medical isotopes. Natural Resources Canada announced yesterday that it would distribute CAN$31 million (US$31.1 million) to four teams that will use existing cyclotrons and linear accelerators to develop Technetium-99m (Tc-99m) by April 2012. An extra CAN$4 million will go on costs the government incurs in setting up and administering the overall programme.
The federal government gave up on the National Research Universal reactor at Chalk River, Ontario, and its planned successor, two Multipurpose Applied Physics Lattice Experiment (MAPLE) reactors, after it decided safety issues were too pricey to fix. The NRU produced about half the world’s supply of medical isotopes before it suffered several prolonged shutdowns beginning in 2007 (see Nature stories here and here). Problems at the site squelched the global isotope supply in 2009 (see Nature stories here and here). It is now back online, but will stop producing medical isotopes in 2016.
The isotopes produced by the NRU are the by-products of highly enriched uranium. They include molybdenum-99 (Mo-99), an unstable isotope (half-life, 66 hours) that decays into Tc-99m (half-life, 6 hours). Because of its short half-life, Tc-99m cannot be stockpiled.
All four of the funded teams will avoid using uranium and focus on scale-up issues, including the safety and commercial viability of producing Tc-99m without nuclear reactors.
“These investments will help us move towards a more diversified supply chain – one that is robust and less vulnerable to disruption,” Christian Paradis, Minister of Natural Resources, said in a statement.
The two teams using cyclotrons aim to generate Tc-99m by bombarding molybdenum-100 with a beam of protons. The project, led by TRIUMF, the national physics laboratory based in Vancouver, received CAN$6 million. The other, spearheaded by Advanced Cyclotron Systems Inc. (ASCI), received CAN$11 million. The ASCI project will rely on cyclotrons in Quebec and Alberta; preliminary experiments have already produced small amounts of Tc-99m. ASCI estimates the two sites could supply up to 15% of Canadian requirements (see press release).
The other two teams, Canadian Light Source Inc. in Saskatoon, Saskatchewan, and the Manitoba-based Prairie Isotope Production Enterprise (PIPE) project, will see whether they can generate the medical isotope by firing X-rays at coin-sized discs of Mo-100 to produce radioactive Mo-99, which then decays into Tc-99m. The federal government allotted CAN$10 million to the CLS-led group and CAN$4 million to PIPE. The CLS says it could meet 20-30% of Canada’s needs.
Each team is confident it can produce the medical isotope by next April. If all goes as planned, Timothy Meyer, head of strategic planning and communications at TRIUMF, there will be an “an embarassment of riches” to choose from (see Postmedia News).
Despite this, some are left wondering whether the government has failed to diversify sufficiently. In December 2009, an expert panel advised a mix of reactor- and non-reactor-based technologies to produce medical isotopes, and recommended the government move quickly to build a new nuclear research reactor (see report). The cyclotron is the “timeliest option”, but “it is not a complete solution”, the authors warned. The short half-life of Tc-99m prevents it from being shipped to hospitals and radiopharmacies that are much more than 4 hours from a cyclotron.
Image courtesy of Sherbrooke University Hospital Étienne-Le Bel Clinical Research Center, Quebec, Canada.