Some synthetic radioisotopes are extracted from spent nuclear reactor fuel rods, which contain various fission products. For example, it is estimated that up to 1994, about 49,000 terabecquerels (78 metric tons) of technetium were produced in nuclear reactors; as such, anthropogenic technetium is far more abundant than technetium from natural radioactivity.
Some synthetic isotopes are produced in significant quantities by fission but are not yet being reclaimed.  Other isotopes are manufactured by neutron irradiation of parent isotopes in a nuclear reactor (for example, technetium-97 can be made by neutron irradiation of ruthenium-96) or by bombarding parent isotopes with high energy particles from a particle accelerator.
Many isotopes, including radiopharmaceuticals, are produced in cyclotrons. For example, the synthetic fluorine-18 and oxygen-15 are widely used in positron emission tomography.