Nuclear isomers in medicine

Only a small handful of nuclear isomers plays an important role in modern medicine. However, one single isomer (Tc-99m) is in terms of quantitative use almost the foundation of the medical application of radioactive compounds. This single isomer has driven the development of modern nuclear medicine over half a century. It is used for diagnostic imaging every day and all over the world. The nuclear and atomic physics basis for this is explained. The main areas of nuclear medicine (diagnostic single photon imaging, diagnostic positron emitter imaging and therapeutic use) are explained, and the few important isomers used in each category are exposed. Although nuclear medicine is evolving rapidly and making important gains in the management of oncological, cardiological and neurological diseases, new radionuclides and new isomers are rarely introduced. The medical use is confined to a narrow set of radionuclides close to the line of stability, and here, of course, the nuclear properties in general and the characteristics of the isomeric states are well known, and possible medical usage has been considered repeatedly. The nuclear isomers will probably keep their role, but from basic physics point of view, just as useful but trivial example of applied nuclear physics.