Campus Research 2011

Medical isotopes a safer, cheaper way?

From Friday's Globe and Mail

Project leader Mark de Jong at the Canadian Light Source synchrotron at the University of Saskatchewan. (DAVID STOBBE/David Stobbe for The Globe and Mail)

It may sound like a real-life version of The Big Bang Theory meets Corner Gas, but a group of physicists and engineers at the University of Saskatchewan are dead serious about creating medical isotopes using high-speed electrons instead of nuclear fission.

"The real challenge," says physicist and project leader Mark de Jong, "is to make sure we have the isotopes for the people, for the health, of Canada."

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Dr. de Jong and his team at Canadian Light Source (CLS) on the Saskatoon campus are working to prove by March, 2012, that linear accelerators, known as linacs, can be a cost-effective way to produce technetium-99m — used as a radioactive tracer in the majority of medical scans — and provide enough for Canadian needs. That means enough for an estimated 5,500 scans a day for such things as heart, bone, lung and brain imaging.

The project is one of four funded by Natural Resources Canada's Non-reactor-based Isotope Supply Contribution Program to find ways to move technetium-99m production away from the nuclear industry by 2016 and avoid the costly — and dangerous — shortages of the past several years, sparked in large part by repeated problems at the Chalk River, Ont., reactor, one of the world's leading producers of medical isotopes and set to close in five years.

All four projects use particle acceleration systems — two with linacs; two with cyclotrons — with the advantages, they say, of much lower costs than building nuclear reactors, no need for weapons-grade uranium and no nuclear waste.

As Canada's national centre for synchrotron light research and home to the powerful football-field-sized accelerator, it's no surprise that CLS led a bid, partnered with the National Research Council, the University of Ottawa Heart Institute, the University of Toronto-affiliated University Health Network and Madison, Wisc.-based NorthStar Medical Radioisotopes.

The heart of the project will be a 40-kilowatt linac, ordered in early March from Ottawa-area-based Mevex Corp. and expected to be on site in October.

Here's how it will work, Dr. de Jong says: Electrons fired into a 3 1/2-metre-long copper tube "basically at the speed of light" will strike a target of tantalum, converting electron power into high-energy photons, which will irradiate 10 to 15 nickel-sized disks of molybdenum-100 (Mo-100). As the disks are irradiated, a percentage of the metal will be converted into molybdenum-99, which decays into technetium-99m. The disks will be dissolved and the isotope extracted from the solution in a separator "about the size of a microwave oven" being built by NorthStar. Any leftover Mo-100 would be recycled.

Mo-99 has a half-life (the time it takes to decay into Tc-99m) of 66 hours and the Tc-99m a half-life of six hours, Dr. de Jong says, so the molybdenum solution would be sent to the hospitals and separated on site.

Each step requires precise calculations. For example, how strong should the beam be? How long should the target be irradiated? What's the best form for the disks? How do you keep it all cool?

The plan is to have everything ready by the end of this year, with the first molybdenum-99 produced by February.

The "magic goal," Dr. de Jong says, is to be able to produce 100 to 200 curies (radiation units) of Mo-99 in a week — before the end of next March, when the government funding ends. "Then I think we've got a good case for starting to take a look at, 'Okay, how do we roll it out in terms of the further development?'"

The project is the next step in a process that began in 2009 at National Research Council Canada (NRC), which used a smaller accelerator to prove the principle and produce small quantities of medical grade Tc-99m. That expertise will be invaluable to the CLS team, Dr. de Jong says.

"My goal," Dr. de Jong says, "would be that, at a minimum, we basically demonstrate an alternate technique and show that it's a viable approach, that we can produce enough and that we can essentially have a method that everything can be done within Canada."

OTHER PROJECTS

Natural Resources Canada funded three other projects in January to develop alternative methods for producing technetium-99m, the world's most commonly used medical isotope.

Prairie Isotope Production Enterprise, a consortium including the University of Winnipeg, the city's Health Sciences Centre, the Winnipeg Regional Health Authority and Acsion Industries in Pinawa, Man., received $4-million. Like Canadian Light Source, PIPE is using a linear accelerator to produce molybdenum-99, which decays into Tc-99m. It will use a former Atomic Energy of Canada Limited facility near Pinawa for the project.

The other two projects are using cyclotrons, circular particle accelerators used in hospitals across Canada to create very short-lived isotopes for positron emission tomography (PET) scans:

•Advanced Cyclotron Systems Inc., partnered with the University of Alberta in Edmonton, the Centre Hospitalier Universitaire de Sherbrooke in Quebec and Thunder Bay Regional Research Institute in Ontario, received $11-million.

•The TRIUMF laboratory at the University of British Columbia in Vancouver, partnered with the BC Cancer Agency, the Centre for Probe Development and Commercialization at McMaster University in Hamilton, and the Lawson Health Research Institute in London, Ont., got $6-million.

Cyclotrons produce Tc-99m directly so, to deal with the substance's six-hour half life, or time it takes to decay, those proposals suggest tapping into a national cyclotron network.

Special to The Globe and Mail

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