The director of nuclear medicine at the University of Iowa says a global shortage of medical isotopes used in the diagnosis and treatment of diseases in patients may get worse in the coming weeks.

Doctor Michael Graham says most of the reactors that produce the isotopes are shut down because of technical problems or maintenance. Graham says there are small number of nuclear reactors that are capable of making the isotope and all are in Canada, the Netherlands, Belgium, France and South Africa.

Graham says the U.S. didn’t produce the needed isotopes because Canada had planned to build two new reactors — but those were never brought up to speed because of technical problems. Graham says the federal government is looking into one option to produce the isotopes in the U.S.

Graham says a bill is being introduced into congress to convert a Missouri University research reactor to supply the isotopes, and that will costs about 150-million dollars to upgrade that facility. Graham says the isotopes are used in a number of diagnostic tests for things like heart disease, cancer and thyroid problems.