In therapeutic nuclear medicine (radionuclide therapy), unique characteristics of radioactive materials (radioisotopes) are used for therapeutic irradiation of cells and/or organs.
Typically, a small amount of a radiopharmaceutical* is introduced into the body by injection or ingestion. The radiopharmaceutical is attracted to particular organs or tissues. From their locations within the body, the radioisotope releases small amounts of energy (radiation) which will act on cells (target cells) and/or organs (target organs). This irradiation can be for the purpose of a curative treatment (for instance thyroid cancer), palliative treatment (for instance for bone pain) or to reduce an organ's function (for instance an over-active thyroid).
Radiopharmaceuticals are molecules or chemicals that are attached to a small amount of radioactive isotope that once administered to the patient are able to specifically localize within organs and/or organ systems in health and disease.