The medical isotope crisis: how we got here and where we are going.

(99m)Tc is the most widely used radionuclide in nuclear medicine. The reactor stoppages that occurred in recent years illustrated the vulnerability of the availability of radiotracers for imaging. With many of the reactors due for shutdown over the next 5-10 y, alternative routes to producing the (99)Mo/(99m)Tc pair are being explored. This brief review examines how we have reached this situation and what the near and distant future holds for securing the availability of these radioisotopes.