A Canadian nuclear reactor is set to resume producing medical isotopes after being shut for 15 months of repairs.
The National Research Universal reactor in Chalk River, Ontario, was closed in May 2009 after a leak of heavy water within the reactor.
It had been producing about a third of the world supply of medical isotopes.
The disruption to supply caused delays and cancellations of diagnostic tests that use the isotopes, including scans for cardiovascular disease and cancer.
"The reactor is now operating at high power and can begin to create medical isotopes," operator Atomic Energy of Canada said in a statement.
Medical officials welcomed the 53-year-old reactor's return to service.
"It's terrific that we've gotten what is by all measures the most significant producer of medical isotopes in the world back functioning," Dr Robert Atcher of the US Society of Nuclear Medicine told the BBC.
The shortage caused by the Chalk River reactor's closure was exacerbated by the shut-down for maintenance of another major isotope-producing reactor in Petten, in the Netherlands.
The isotopes produced at the Chalk River plant are used for medical imaging and diagnostic scans for fractures, cancer and heart conditions.
When injected into the body they give off radiation that can be seen by a camera.