Putting a New Spin on some Old Physics
When Pierre Trudeau visited the UBC campus in February 1976, he candidly acknowledged that he knew nothing about cyclotrons but was excited about the research potential they offered for Canada. The then prime minister was in Vancouver to speak at the official dedication ceremony for TRIUMF, a facility on the university’s south campus that still houses the world’s largest example of a cyclotron, AKA a high energy particle accelerator.
What a difference a few decades can make. TRIUMF has since gained an international reputation for expertise in areas related to physics, chemistry, and nuclear medicine. And although most Canadians may still be hard‑pressed to explain what a cyclotron is, it’s probably fair to that say many have at least heard of a high energy particle accelerator – think Higgs boson. But the enhanced public profile of these once‑obscure pieces of scientific equipment is also due to a series of events that have brought cyclotrons into the fold of modern medicine.
At the end of 2007, a research nuclear reactor in the small town of Chalk River, Ontario, broke down unexpectedly. It was the sole North American source of radioactive materials key to producing technetium‑99m, an isotope required for the sophisticated medical imaging that doctors now routinely use to diagnose and treat conditions such as cancer or heart disease.
When the reactor broke down, thousands of patients found themselves waiting for imaging procedures, and although the mechanical problem was resolved after a few hectic months, the “isotope crisis” had revealed that the reactor might well be on its last legs.
Dr. Francois Benard holds the BC Leadership Chair in Functional Cancer Imaging at UBC. As the medical community struggled with the problem, he was among the first to identify cyclotrons as a potential solution. They are already found in dozens of hospitals across the country – devices typically as big as a single car garage containing powerful magnets that spin electrically charged particles around at high speeds then direct them at small, coin‑sized targets. Depending on a target’s makeup, the impact yields all sorts of isotopes. More specifically, if the target is made of the metal molybdenum, one of those isotopes is technetium‑99m.
Technetium‑99m is a short‑lived, radioactive version of a fairly unremarkable silvery gray metal. Small quantities of it can be attached to biological agents with an affinity for particular organs or cancerous tumours. Once injected directly into the human body, the localized radiation can be turned into images that go well beyond the established success of X‑ray imagery. Not only do they reveal the physical structure of what is happening beneath the skin, but also the otherwise invisible biochemical interactions that are occurring at the same time.
As exotic as this procedure might sound, it has become a routine undertaking in the last 20 years, one that is now carried out on millions of patients every year. Benard has been interested in this powerful technology for even longer, since his student days at the Université de Sherbrooke, where his father had been among the researchers who helped establish the medical school.
The cyclotron’s ability to produce technetium has been known since 1971, but the finding held little medical interest while the Chalk River reactor was doing its job. Thomas Ruth, senior research scientist at TRIUMF, credits Benard with reminding a community in crisis of this valuable piece of old news.
“Francois was the one locally that really pushed the envelope to make us look at something that was staring us in the face,” he says.
By 2010 a team led by principle investigator Dr. Paul Schaffer, as well as members of Richmond‑based Advanced Cyclotron Systems, Inc., one of the world’s leading manufacturers of these devices, were actively exploring the prospect of cyclotron‑based isotope production. More than $30 million in federal funding went to research groups across the country for this purpose. The culmination of these efforts came this June with an announcement that the BC Cancer Centre’s cyclotron could generate technetium‑99m in quantities sufficient to meet the needs of Vancouver and likely well beyond. Although the downtown Vancouver‑based cyclotron will be turning out the isotopes on a workaday basis, it was the hard science carried out at TRIUMF by Schaffer’s team that made it viable.
“What we’ve achieved is showing that we could scale things up substantially, by an amount of 10 times,” said Benard. “Essentially the milestone is moving away from pilot scale to real‑life quantities that make it useful for urban areas.”
Researchers at cyclotron facilities in Edmonton, Alberta and Sherbrooke, Quebec, are also close to demonstrating their own ability to meet regional imaging needs. If similar achievements can be made in other parts of the country, Canada will become the first place in the world to free itself from the constraints of nuclear reactors as the sole source of technetium‑99m.
For Professor Anna Celler of the university’s Department of Radiology, this milestone seemed more like a trip down memory lane. As part of the project team, she took part in calculations of a cyclotron’s isotope output, just as she had done for her PhD research decades earlier.
“It was very natural and I enjoyed it,” she said, recalling a peak period in cyclotron research. “Investigations of different radioisotopes using cyclotrons is something that was done more in the 70s and 80s than it is being done now.”
Even so, Celler added that this accomplishment may well be a sign that cyclotrons are hitting their scientific stride once again. Besides solving the immediate problem of technetium‑99m, the same approach can turn out a wide range of different isotopes, each suited for a specific type of medical imaging.
Pierre Trudeau might not have fully understood what a cyclotron is, but he was right to be excited. “We are involved in other projects, creating medically important radioisotopes,” says Celler. “People realize that the cyclotron can be used, and the expertise is here.”