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Medical Term:

annihilation radiation


the radiation resulting when a positron from beta-positive decay comes to rest. It encounters an electron, and the two particles annihilate each other and convert their rest mass into two 0.51-MeV gamma rays emitted in exactly opposite directions.

See: pair production

© Copyright 2017 Wolters Kluwer. All Rights Reserved. Review Date: Sep 19, 2016.