Technetium-99m is the most widely used isotope for diagnostic imaging. (CBC)

A move by the U.S. to produce a domestic supply of medical isotopes brings Canadian isotope suppliers a step closer to losing their largest customer, a nuclear medicine specialist says.

The U.S. House of Representatives voted 400-17 last week in favour of a bill that would give $163 million US over five years to subsidize domestic production of a key medical isotope, technetium-99m, or Tc-99m, for use in diagnostic medicine.

"The worldwide isotope shortage has long been adversely affecting patients in the U.S.," Dr. Michael Graham, president of the Society of Nuclear Medicine, said in a news release. "This important legislation will bring us one step closer to solving this chronic problem."

The latest ongoing shutdown of the 52-year-old National Research Universal reactor in Chalk River, Ont., is the third time Canada has "dropped the ball" on producing medical isotopes, said Dr. Christopher O'Brien, head of the Ontario Association of Nuclear Medicine.

"This is not unexpected; it's very sad," O'Brien said in an interview on Monday. "It's an example of Canada dropping the ball and not having a broad enough perspective on the ramifications of a political decision.

"As Prime Minister [Stephen] Harper stated, Canada is 'getting out of the business,' against the recommendation of the medical community."

Chalk River's reactor licence expires in 2016, and the federal government has not committed to renewing it.

Canada is getting about half of its normal supply of medical isotopes from Europe and South Africa and is currently stretching its supply for cancer diagnosis and treatment by using a different type of isotope for heart tests, O'Brien said.

But doctors and patients are always "teetering on the brink of disaster" if hiccups in delivery from overseas occur, he added.

Technologists are constantly negotiating with pharmaceutical companies to ensure the limited supplies of medical isotopes are distributed fairly, he said.

"Going from a position of leadership to a position of dependency has its challenges," O'Brien said.

The U.S. bill is now headed to the U.S. Senate for approval.

O'Brien and his group would like to see Canada send two "calming" messages to the world:

• Canada will continue to be a leader in supplying medical isotopes using tried and true reactor-based technology.
• Canada is looking at innovative research into alternative approaches of producing Tc-99m without using nuclear reactors.

On Monday, the BC Cancer Agency announced it has a $1.3-million grant from the Canadian Institutes of Health Research and the Natural Sciences and Engineering Research Council of Canada to develop an alternative source of medical isotopes using cyclotrons instead of nuclear reactors.

Health Canada announced the grant as part of a $5.4-million research program called Alternative Radiopharmaceuticals for Medical Imaging.

The announcement also included two-year grants worth a total of $2.17 million for two research teams at the University of Ottawa Heart Institute. The teams will develop two new alternatives to medical isotopes, test new applications for their use in diagnosing heart disease and fast track production and distribution across Canada.

France and the Netherlands have said they will replace aging reactors with modern reactors to supply medical isotopes to their populations, similar to what the U.S. bill proposes, O'Brien said.