text: Production of a radiopharmaceutical involves two processes:
  * The production of the radionuclide on which the pharmaceutical is based.
  * The preparation and packaging of the complete radiopharmaceutical.
  Radionuclides used in radiopharmaceuticals are mostly radioactive isotopes of elements with atomic numbers less than that of bismuth, that is, they are radioactive isotopes of elements that also have one or more stable isotopes. These may be roughly divided into two classes:
  * Those with more neutrons in the nucleus than those required for stability are known as proton-deficient, and tend to be most easily produced in a nuclear reactor. The majority of radiopharmaceuticals are based on proton deficient isotopes, with technetium-99m being the most commonly used medical isotope, and therefore nuclear reactors are the prime source of medical radioisotopes.
  * Those with fewer neutrons in the nucleus than those required for stability are known as neutron-deficient, and tend to be most easily produced using a proton accelerator such as a medical cyclotron.