A Canadian nuclear has been shut down, throwing awry scanning schedules for cancer patients across the world.
The Chalk River reactor in Ontario is the main supplier of isotopes that are injected as a radioactive dye into patients with cancer or other diseases for scanning purposes. The reactor supplies two-thirds of the world's medical isotopes to hospitals.
It was closed two weeks ago for scheduled maintenance which has now been prolonged until early or mid-January.
Doctors have described the shortage of medical nuclear material as ''potentially catastrophic''.
Thousands of patients in Canada, the United States and other countries have had vital tests postponed because of the shortage.
''Last week, I guess you could describe it as struggling,'' said Dr Chris O'Brien, president of the Ontario Association of Nuclear Medicine.
''This week it's devastating, and next week potentially catastrophic.''
The head of the Canadian Nuclear Safety Commission said the government-run reactor was violating safety standards.
The sudden shutdown has created problems for MDS Nordion, the medical supply company which sells much of Chalk River's output.
The company said it anticipates a return to full production in early to mid-January.
In the meantime, company officials said it was looking for other sources of supply for the radioisotopes.
The isotopes cannot be stockpiled because they have a short shelf life.