Half-life (redirected from Half-life (1999))

half-life (haf´lif) the time required for the decay of half of a sample of particles of a radionuclide or elementary particles; symbol t 1/2 or T 1/2.

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antibody half-life  a measure of the mean survival time of antibody molecules following their formation, usually expressed as the time required to eliminate 50 per cent of a known quantity of immunoglobulin from the animal body. Half-life varies from one immunoglobulin class to another.

biological half-life  the time required for a living tissue, organ, or organism to eliminate one-half of a radioactive substance which has been introduced into it.

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half-life

n.

1. The time required for half the nuclei of a specific radionuclide or radioactive substance to undergo radioactive decay. Also called physical half-life.

2. The time required for half the quantity of a drug or other substance deposited in a living organism to be metabolized or eliminated by normal biological processes. Also called biological half-life.

3. The time required for the radioactivity of material taken in by or administered to an organism to be reduced to half its initial value by a combination of biological elimination processes and radioactive decay. Also called effective half-life.

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Half-life

The time required for half of the atoms in a radioactive substance to disintegrate.

Mentioned in: Positron Emission Tomography

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half-life,

n the time in which a radioactive substance will lose half of its activity through disintegration.

half-life, biologic,

n the time in which a living tissue, organ, or individual eliminates, through biologic processes, half of a given amount of a substance that has been introduced into it.

half-life, effective,

n the half-life of a radioactive isotope in a biologic organism, resulting from the combination of radioactive decay and biologic elimination.

half-life, physical,

n the average time required for the decay of half the atoms in a given amount of a radioactive substance.

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half-life

the time in which the radioactivity usually associated with a particular isotope is reduced by half through radioactive decay.