Nuclear Medicine is an important branch of diagnostic radiology that provides unique physiologic information about disease processes. There are numerous established applications for nuclear medicine in human patients and a smaller number of established applications for nuclear medicine in animal patients. Nuclear medicine involves the use of radioactive materials in either a diagnostic or therapeutic manner.

Scintigraphy involves the production of images demonstrating the distribution of radioactive materials within a patient following the internal administration of a radioactive pharmaceutical. Scintigraphy is a diagnostic branch of nuclear medicine. Radioactivity is the spontaneous disintegration of the nucleus of a radioactive atom. This phenomenon was discovered initially in 1896 by Becquerel using uranium. Pierre and Marie Curie discovered two other naturally occurring radioactive materials, polonium and radium in the final years of the 19th century. These discoveries combined with Roentgen's discovery of x-rays in 1895, set the stage for the medical fields of radiology and nuclear medicine.

Elements are made up of atoms. The atomic number (Z), or the number of protons in an atom's nucleus defines its identity, while the number of neutrons in the nucleus determines the isotope of the element. The ratio of neutrons:protons in the nucleus defines its stability. Too many neutrons or protons will make the nucleus unstable, causing it to undergo radioactive decay.

		Standard notation used to summarize atomic and nuclear compostition. Position your mouse over the individual letters to show descriptions

Radioactive decay is a process in which an unstable nucleus transforms into a more stable one by emitting particles and/or photons and releasing nuclear energy. Radioactive decay is a process that involves primarily the nucleus, whereas chemical reactions involve primarily the outermost orbital electrons of the atom. Thus the fact that an atom has a radioactive nucleus does not effect its chemical behavior. Similarly, the chemical state of an atom does not affect its radioactive behavior. For example, an atom of the radionuclide ¹³¹I exhibits the same chemical behavior as an atom of ¹²⁷I, a naturally occurring stable nuclide. Furthermore, ¹³¹I has the same radioactive characteristics whether it exists as iodide ion (I^-) or incorporated into a large protein molecule as a radioactive label.