The availability of medical isotopes is in question as one of Canada's major supplies is scheduled to be shut down for repairs later this month.

Since the National Research Universal reactor in Chalk River, Ont., went down in the spring, Atomic Energy of Canada Ltd. said the repairs would take a month, then three.

It is not scheduled to be back up by the end of March, creating a supply crunch for medical isotopes that are used for diagnostic imaging in cancer and heart patients.

The void in isotope supply is set to worsen on Feb. 19 when the Dutch reactor in Petten is scheduled to shut down for maintenance, likely for about six months.

"This is the third time around," said Dr. Christopher O'Brien of the Ontario Nuclear Medicine Association in Brantford. "Our staff is much more comfortable with it, but it does create an extra burden on our technologists, on our nursing staff and on our clerical staff who are struggling in communicating with patients on how to move these patients around based on medical isotope supply."

Smaller reactors in France, South Africa and Belgium will pitch in, but there are questions about whether it will be enough.

The federal government says its imperative that NRU be brought back on line quickly and safely.

Doctors 'extraordinarily worried': Bennett

Doctors have been reluctant to refer patients because they are uncertain about the isotope supply. O'Brien urged doctors to let their nuclear medicine colleagues know about such patients so that their needs can be met.

"The doctors are extraordinarily worried," agreed Liberal critic Carolyn Bennett.

Nuclear medicine doctors have been coping, but are expecting to reach their capacity to do procedures on more weekdays, up from Thursdays and Fridays currently, O'Brien said.

On Tuesday, Liberals will hold a roundtable on the isotope shortage. The meeting has been planned for weeks, and includes invitations to domestic and international experts to propose solutions.