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Nuclear medicine

Alberta researchers get go-ahead for new cyclotron

EDMONTON – A team of researchers is moving ahead with a plan to build a particle accelerator, also known as a cyclotron, that’s capable of producing medical isotopes. If successful, the Edmonton facility would provide materials needed to alleviate the shortage of medical isotopes that occurred when the nuclear reactor in Chalk River, Ont., went offline for repairs.

In March, the federal government approved an initial $3-million grant for the project. Dr. Sandy McEwan, chair of oncology at the University of Alberta, and his team are now searching for a space large enough to hold the giant machine and its two-metre-thick walls of protective concrete.

They hope to have the particle accelerator, a miniature version of the Franco-Swiss Hadron Collider, ready to start spinning and colliding protons by early 2011.

Radioactive isotopes are essential for many of the tests doctors use to diagnose heart problems, cancer, sports injuries and bone lesions. But the global supply has been short ever since Ontario’s Chalk River reactor was shut down for repairs last year. Reactors in The Netherlands and South Africa have also gone down recently, and last week the head of the Canadian Association of Nuclear Medicine warned of cancelled tests.

Dr. McEwan’s new cyclotron should produce the necessary isotope, technetium-99, he said. “We’ve got a lot of research to do before we get to that stage, but that’s the vision we have going forward,” he told the Edmonton Journal

The cyclotron works by accelerating protons through a loop until they travel at about 90 per cent of the speed of light. Then a technician deflects the high-energy proton into a target site filled with the element molybdenum-100.

The force of the collision changes some of the element to technetium-99, one step down the periodic table, and once the remaining molybdenum and technetium are separated, the latter can be shipped to hospitals.

An added challenge is technetium’s radioactivity. It has a half-life of only six hours, which means it degrades quickly. “You’ve got to work very fast and you’ve got to make a lot of it,” said Dr. McEwan. “But it is possible to make it and ship it.”

Researchers in Edmonton know the idea works, because they already have a cyclotron working in the basement of the Cross Cancer Institute producing F sodium florid, which can be used for some of the diagnostic tests in which doctors normally use technetium. That cyclotron has been key to preventing a long wait-list in Alberta.

The F sodium florid has a half-life of only two hours, but still gets shipped to Calgary and Winnipeg every day for tests there. The team hopes to build on that success to prove this cyclotron can work reliably, too. If they succeed, there might be no need for Canada to build a new multi-use nuclear reactor to replace the aging Chalk River facility. Such a project has been estimated to cost between $500 million and $1.2 billion to build.

In a diagnostic test, the radioactive material works as tiny tracer molecules in the patient’s body. Doctors mix the technetium with another molecule, like sugar, that will be absorbed at a different rate by diseased tissue than healthy cells.

Cancerous cells, which multiply more quickly than normal cells, will absorb more of the sugar cells. With the technetium attached, a nuclear medicine scan will show a brighter spot, indicating cancer.

Posted April 8, 2010

 

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