Canadian government orders reactor to produce medical isotopes

December 14, 2007

Physicians around the globe breathed a sigh of relief as the Canadian nuclear reactor responsible for producing a majority of the world’s medical radioisotopes was ordered to begin production again.

Physicians around the globe breathed a sigh of relief as the Canadian nuclear reactor responsible for producing a majority of the world's medical radioisotopes was ordered to begin production again.

The Chalk River Laboratories reactor in Ottawa, OT, had been shut down since Nov. 17 for routine maintenance, which unexpectedly stretched longer than anticipated. Before the ink could dry on press releases announcing that the closure would last into mid-January, the Canadian House of Commons and Senate, under considerable international pressure, passed emergency legislation on Dec. 12 ordering the reactor to come back online.

Atomic Energy of Canada Limited said in a press release on Dec. 14 that it had begun the process to restart the reactor and would produce medical isotopes within seven to eight days.

U.S. nuclear physicians had little option for backup suppliers during the shutdown, as the Canadian reactor is the sole producer of medical isotopes for North America.

"We've had to be very selective about the procedures we do, and we've had to be very inventive about what we do," said Dr. Chaitanya Divgi, chief of nuclear medicine and clinical molecular imaging at the Hospital of the University of Pennsylvania.

About 90% of all non-PET nuclear imaging procedures use technetium-99m, Divgi said. It is the workhorse of general nuclear medicine, and its uses include diagnostic applications in the brain, lungs, liver, kidneys, bones, and heart.

Tc-99m has a shelf-life of six hours, making it impractical to ship over long distances. U.S. hospitals receive containers known as generators that contain molybdenum-99, the isotope that breaks down into Tc-99m. Mo-99 has a half-life of 66 hours.

The generators are sold mainly by Bristol-Myers Squibb and Mallinckrodt, a unit of Covidien. Facilities use a chemical process to separate the Tc-99m just before it is needed for imaging.

"The reactor shutdown has been highly disruptive for us, particularly for Tc-99m," said Dr. Richard Wahl, director of nuclear medicine at Johns Hopkins University. "We've had to change things a bit, but we haven't had to cancel any procedures."

A decades-old debate about dependence on Canada for molybdenum came to the fore as hospital officials in the U.S. expressed concern about relying on one source - a foreign one, at that - for most of its medical isotope needs.

"We invented Tc-99m, and now we don't make it ourselves," Divgi said. "We need a national effort to ensure we have medical isotopes available."

The University of Missouri in Columbia is conducting a feasibility study to determine if it can ramp up its MU Research Reactor (MURR) to become a domestic source of Mo-99.

"The MURR Center has the potential to supply about 50%t of the U.S. nuclear medicine community's weekly Mo-99 demand using low-enriched uranium," said Ralph Butler, director of the MURR Center, in a press release.

Butler cited potential medical problems if the U.S. closed its borders to the shipment of radioactive materials due to a security event.