Glossary of Radiological Terminology (A)

GLOSSARY OF
RADIOLOGICAL TERMINOLOGY

ABSORBED DOSE The amount of energy imparted to matter by ionizing radiation per unit mass of irradiated material. The unit of absorbed dose is the rad and equal to 100 ergs/gram.
ABSORPTION The process by which radiation imparts some or all of its energy to any material through which it passes.
ACTIVATION The process of making a material radioactive by bombardment with neutrons, protons, or other nuclear radiation.
ACTIVITY The number of nuclear disintegrations occurring in a given quantity of material per unit time.
ACUTE EXPOSURE The absorption of a relatively large amount of radiation over a short period of time.
ACUTE HEALTH EFFECTS Prompt radiation effects for which the severity of the effect varies with the dose and for which a practical threshold exists.
ADULT An individual 18 or more years of age.
ALARA Acronym for As Low As Reasonably Achievable. Making every reasonable effort to maintain exposures to radiation as far below the dose limits as is practical.
ALPHA PARTICLE A positively charged particle emitted from the nucleus during radioactive decay and having a mass and charge equal in magnitude to a helium nucleus that has 2 protons and 2 neutrons.
ANION A negatively charged ion.
ANNUAL LIMIT OF INTAKE (ALI) The derived limit for the amount of radioactive material taken into the body of an adult worker by inhalation or ingestion in a year. ALI is the smaller value of intake of a given radionuclide in a year by the reference man that would result in a committed effective dose equivalent of 5 rems (0.05 Sv) or a committed dose equivalent of 50 rems (0.5 Sv) to any individual organ or tissue.
ATOM The smallest particle of an element which is capable of entering into a chemical reaction.
ATOMIC NUMBER (Z) The number of protons in the nucleus of an atom.
ATTENUATION The process by which a beam of radiation is reduced in intensity when passing through some material. It is the combination of absorption and scattering processes and leads to a decrease in flux density of the beam when projected through matter.

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ABSORBED DOSE	The amount of energy imparted to matter by ionizing radiation per unit mass of irradiated material. The unit of absorbed dose is the rad and equal to 100 ergs/gram.
ABSORPTION	The process by which radiation imparts some or all of its energy to any material through which it passes.
ACTIVATION	The process of making a material radioactive by bombardment with neutrons, protons, or other nuclear radiation.
ACTIVITY	The number of nuclear disintegrations occurring in a given quantity of material per unit time.
ACUTE EXPOSURE	The absorption of a relatively large amount of radiation over a short period of time.
ACUTE HEALTH EFFECTS	Prompt radiation effects for which the severity of the effect varies with the dose and for which a practical threshold exists.
ADULT	An individual 18 or more years of age.
ALARA	Acronym for As Low As Reasonably Achievable. Making every reasonable effort to maintain exposures to radiation as far below the dose limits as is practical.
ALPHA PARTICLE	A positively charged particle emitted from the nucleus during radioactive decay and having a mass and charge equal in magnitude to a helium nucleus that has 2 protons and 2 neutrons.
ANION	A negatively charged ion.
ANNUAL LIMIT OF INTAKE (ALI)	The derived limit for the amount of radioactive material taken into the body of an adult worker by inhalation or ingestion in a year. ALI is the smaller value of intake of a given radionuclide in a year by the reference man that would result in a committed effective dose equivalent of 5 rems (0.05 Sv) or a committed dose equivalent of 50 rems (0.5 Sv) to any individual organ or tissue.
ATOM	The smallest particle of an element which is capable of entering into a chemical reaction.
ATOMIC NUMBER (Z)	The number of protons in the nucleus of an atom.
ATTENUATION	The process by which a beam of radiation is reduced in intensity when passing through some material. It is the combination of absorption and scattering processes and leads to a decrease in flux density of the beam when projected through matter.