Radioimmunoassay was used extensively in clinical medicine but more recently has been largely replaced by non-radioactive methods.
Benedict Cassen's work with a directional probe lead to the development of the first imaging with a rectilinear scanner.
[9] In the same decade (1954) the Society of Nuclear Medicine (SNM) was organized in Spokane, Washington (US),[10] and (1958) Hal Anger developed the gamma scintillation camera,[11] which could image a whole region at the same time.
Initial introduction of radioisotopes into medicine required individuals to acquire of a considerable background information which was foreign to their medical training.
[13] At that time, the specialty include all of the uses of radioisotopes in medicine – radioimmunoassay, diagnostic imaging, and therapy.
Today, nuclear medicine is based on the use of the tracer principle applied to diagnostic imaging and therapy.
However, current U.S. regulations do not prohibit other physicians from interpreting nuclear medicine studies and perform radionuclide therapy.