A Gamma Counter is a machine to measure gamma radiation emitted by a radionuclide

Radionuclide

A radionuclide is an atom with an unstable nucleus, which is a nucleus characterized by excess energy available to be imparted either to a newly created radiation particle within the nucleus or to an atomic electron. The radionuclide, in this process, undergoes radioactive decay, and emits gamma...

. Up to 300 samples are placed in sealed vials or test tubes, and move along a serpentine track on a horizontal plane. One at a time, they move down inside a shielded detector, set to measure specific energy windows characteristic of the particular isotope. Depending on the half-life and concentration of the sample, measurement times vary from 0.02 minute to one minute. Gamma counters are standard tools used in the research and development of new radioactive compounds used for diagnosing and treating disease, (as in PET

Positron emission tomography

Positron emission tomography is nuclear medicine imaging technique that produces a three-dimensional image or picture of functional processes in the body. The system detects pairs of gamma rays emitted indirectly by a positron-emitting radionuclide , which is introduced into the body on a...

 scanning). Gamma counters are used in radiobinding assay

Radiobinding assay

A radiobinding assay is a method of detecting and quantifying antibodies targeted towards a specific antigen. As such, it can be seen as the inverse of radioimmunoassay, which quantifies an antigen by use of corresponding antibodies.-Technique:...

s and in radioimmunoassay

Radioimmunoassay

Radioimmunoassay is a very sensitive in vitro assay technique used to measure concentrations of antigens by use of antibodies...

s (RIA).

Units can be programmed to measure many different isotopes and perform over 30 different assay tests.