Radiation Protection Glossary

A radiation protection glossary for Radiation Protection Supervisors (RPS) and anyone interesting in radiation safety terminology. The glossary is a mixture of health physics terms, and phrases related to radiation legislation, transport, practical safety and similar.

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Annihilation (Positron - Electron)

Annihilation (Positron - Electron) radiation occurs when an electron (negatively charged) collides with a Positron (positively changed & the electron 'anti-particle'). The usual result is the emission of two gamma ray photons , each of 511 KeV and travelling away from each other. The example in this glossary shows the decay of F-18 by positron emission followed by the resulting annihilation radiation. This process has application in Positron Emission Tomography (PET imaging).

Reality is merely an illusion, albeit a very persistent one

– Albert Einstein