LEWISTON – Maine hospitals have resumed cardiac exams, cancer scans and other tests that were postponed because of an international shortage of radioactive isotopes.

The problem started when a Canadian nuclear reactor that provides half the world’s supply of the isotopes was shut down for maintenance in mid-November. The National Research Reactor in Ontario was allowed to restart in mid-December.

The isotopes are used in at least 15 million medical scans a year in the United States, by one estimate. Some hospitals had to postpone, cancel or look for another test for 60 percent to 85 percent of patients who would have had tests involving the isotope.

Cindy Harradon from the Central Maine Medical Center in Lewiston says the Lewiston hospital is “back to smooth sailing.”