ELIMINATION HALF-LIFE of radioactive materials from an organism — a time term during which activity (quantity) of the radioactive material which is in an organism or body decreases twice.
Reduction of content of radioactive material in an organism is caused by radioactive decay and exchange fiziol, processes. Distinguish biological and effective Items. Biological Items — a time term during which a half of the radioactive material which is contained in an organism or body is removed for the account fiziol, exchange processes. Effective Pct. (Teff) differs in the fact that for its calculation consider also physical disintegration of radioactive material (Tf). In radio isotope diagnosis use generally radioactive materials with short Pct that allows not to subject body tissues to essential radiation.
U. Ya. Margulies.