A positron-emitting radionuclide is introduced, usually by injection, and accumulates in the target tissue.
As it decays it emits a positron, which promptly combines with a nearby electron resulting in the simultaneous emission of two identifiable gamma rays in opposite directions.
These tracers are generally short-lived isotopes linked to chemical compounds which permit specific physiological processes to be scrutinised.
They can be given by injection, inhalation, or orally.
Every organ in our bodies acts differently from a chemical point of view.
In most cases, the information is used by physicians to make a quick diagnosis of the patient's illness.
The thyroid, bones, heart, liver, and many other organs can be easily imaged, and disorders in their function revealed.
In developed countries (26% of world population) the frequency of diagnostic nuclear medicine is 1.9% per year, and the frequency of therapy with radioisotopes is about one-tenth of this.
In the USA there are over 20 million nuclear medicine procedures per year, and in Europe about 10 million.