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Radiation Protection Glossary

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Annihilation (Positron - Electron)
Electron - Positron Annihilation
Annihilation (Positron - Electron) of F-18
Annihilation (Positron - Electron) radiation occurs when an electron (negatively charged) collides with a Positron (positively changed & the electron’s anti-particle). The usual result is the emission of two gamma ray photons – each of 511 KeV 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).