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Medical Term:

radioactive isotope


an isotope with an unstable nuclear composition; such nuclei decompose spontaneously by emission of a nuclear electron (ß particle) or helium nucleus (a particle) and radiation (? rays), thus achieving a stable nuclear composition; used as tracers and as radiation and energy sources.

See: half-life

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