CHALK RIVER, Ont. - Patients in line for medical tests to diagnose cancer and heart ailments may have a longer wait as hospitals try to conserve a scarce supply of isotopes, doctors say.
  
The latest shutdown of an Atomic Energy of Canada Ltd. nuclear reactor at Chalk River, Ont. -- which provides about half the global supply of isotopes used in medical imaging -- is expected to last about a month.

Federally owned AECL says it has enough medical isotopes for the coming week, but will unable to meet demand by Saturday.

A lengthy shortage will force hospitals to delay non-urgent tests, said Dr. Karen Gulenchyn, a nuclear medicine expert who helped advise former health minister Tony Clement during the last isotope shortage in December 2007.

"It may mean that if you have an elective study booked ... that patient is going to be deferred and have to wait until the situation is resolved," she said.

"I'm reasonably confident that for most patients, if they're having an acute problem, that problem is going to be dealt with -- and the greater the acuity, the more likelihood it's going to be dealt with quickly and expeditiously."

Radioactive isotopes are injected into patients so radiologists can pinpoint areas of higher radiation and spot changes in the body so they can make more accurate diagnoses.

The president of the Ontario Association of Nuclear Medicine, Dr. Chris O'Brien, said the isotope shortage won't affect patients this week.

But starting next week, he said, hospitals may start using a different type of isotope that was used years ago. That type of isotope is more technologically challenging but still works.

O'Brien said hospitals may also inject fewer isotopes into patients -- meaning medical imaging will take longer -- or postpone nuclear medicine tests that aren't deemed urgent.

"It may come down to a day-to-day basis as of the middle of next week, and Weeks 3 and 4, determining how many doses we can get, how many patients we can do per day," he said.

"We'll be triaging on a day-to-day basis ... to try and get help to the people who need it urgently and less-urgents will have to wait."

Health Canada and the Ontario government warned Canada's medical community by email on Monday to expect a prolonged shortage of isotopes.

Clement, now industry minister, said the federal government will launch a contingency plan to deal with the isotope shortage.

"We have a plan in place to deal with these kinds of contingency situations where we work with our international partners and the producers of isotopes worldwide," he said in Atlanta, where he is attending an international biotechnology conference.

"That plan will be activated now."

The contingency plan is expected to recommend radioactive isotopes be saved for the most urgent cases, such as cancers, traumas, infections and blood clots in lungs.

Natural Resources Minister Lisa Raitt and Health Minister Leona Aglukkaq said in a statement Tuesday a secure supply of medical isotopes is a global issue.

"The government of Canada is engaging international isotope producers as well as companies such as MDS Nordion, Lantheus, and Covidien, who all play key roles in securing medical isotope supply for North America," they said.