The effective half-life for a radionuclide within the body is the period of time needed for the compound to be decreased by 50%. This occurs due to the combined effect of the biological half-life and the physical half-life for the compound.
Definitions:
(1) The biological half-life is the time required for half of the material to be eliminated from body through excretion in urine, stool, sweat or other routes.
(2) The physical half-life is the time required for the compound to loss half of its activity through radioactive decay.
