Radiation Glossary

absorbed dose

The energy imparted by ionizing radiation per unit mass of irradiated material. The units of absorbed dose are the rad and the gray (Gy).

activity

Rate of disintegration, transformation, or decay of radioactive material. The units of activity are the curie (Ci) and the becquerel (Bq).

ALARA

Acronym for "as low as reasonably achievable." Make every reasonable effort to maintain exposures to radiation as far below the dose limits as is practical consistent with the purpose for which the activity is undertaken, taking into account the state of technology, the economics of improvements in relation to benefits to the public health and safety, and other societal and socioeconomic considerations, and in relation to utilization of ionizing radiation in the public interest.

Annual Limit on Intake
(ALI)

The amount of a radionuclide that would result in a committed effective dose equivalent of 5 rems, or a committed dose equivalent of 50 rems to an organ or tissue. See 10 CFR Part 20 Appendix B.

area of use

A room or suite in which radioactive materials is used. It may have one or more work areas.

background radiation

Radiation from cosmic sources; naturally occurring radioactive materials, including radon (except as a decay product of source or special nuclear material) and global fallout as it exists in the environment from the testing of nuclear explosive devices. "Background radiation" does not include radiation from source, byproduct, or special nuclear materials.

becquerel
(Bq)

1 nuclear transformation per second (s-1).

bioassay

The determination of kinds, quantities or concentrations, and, in some cases, the locations of radioactive material in the human body, whether by direct measurement, called in vivo counting, or by analysis and evaluation of materials excreted or removed from the human body.

CFR

Code of Federal Regulations.

controlled area

An area, outside of a restricted area but inside the site boundary, access to which can be limited by the licensee for any reason.

cpm

Counts per minute. Most radiation detectors display the number of events detected per unit of time. This can be converted to a measure of activity in dpm by dividing by the detection efficiency.

curie
(Ci)

A unit of activity. 3.7 x 1010 nuclear transformations per second, 3.7 x 1010becquerels, or 2.22x1012 nuclear transformations per minute. The term nuclear transformations is often replaced by the term disintegrations.

DAC

Derived Air Concentration. The concentration of a given radionuclide that, if inhaled continuously during the work year, would cause a dose of 5 rem.

deep dose

The dose from external whole body exposure at a tissue depth of 1 cm.

deterministic effect

Health effects, the severity of which varies with the dose and for which a threshold is believed to exist. Radiation-induced cataract formation is an example of a deterministic effect. Also called a nonstochastic effect.

DLAM

School of Medicine, Division of Laboratory Animal Medicine (obsolete). Now the Department of Comparative Medicine.

dose
or radiation dose

Generic term that means absorbed dose, dose equivalent, effective dose equivalent, committed dose equivalent, committed effective dose equivalent, or total effective dose equivalent, as defined elsewhere in this glossary.

dpm

Disintegrations per minute. A measure of activity. See curie.

effective dose equivalent
or effective dose

The sum of the products of the dose equivalent to each organ or tissue and multiplied by their respective tissue weighting factors, and then added to the external whole body dose.

EPA

US Environmental Protection Agency

exposure

Being exposed to ionizing radiation or to radioactive material.

external dose

That portion of the dose equivalent received from radiation sources outside the body.

extremity

Hand, elbow, arm below the elbow, foot, knee, or leg below the knee.

FDA

US Food and Drug Administration.

gray
(Gy)

SI unit of absorbed dose. One gray is equal to an absorbed dose of 1 joule/kilogram (100 rads).

high radiation area

An area, accessible to individuals, in which radiation levels could result in an individual receiving a dose equivalent in excess of 0.1 rem (1 mSv) in 1 hour at 30 centimeters from the radiation source or from any surface that the radiation penetrates.

ICRP

International Commission on Radiological Protection.

ionizing radiation

Alpha particles, beta particles, gamma rays, x-rays, neutrons, high-speed electrons, high-speed protons, and other particles capable of separating a target atom into an electron and a positive ion. As used in this manual, radiation does not include non-ionizing radiation, such as radio- or microwaves, or visible, infrared, or ultraviolet light.

IRB

Institutional Review Board (National Institutes of Health). A committee that reviews and approves research projects that involve human subjects.

monitoring

The measurement of radiation levels, concentrations, surface area concentrations or quantities of radioactive material and the use of the results of these measurements to evaluate potential exposures and doses.

NCDRP

North Carolina Division of Radiation Protection. www.drp.enr.state.nc.us

NCRP

National Council on Radiation Protection and Measurements. A non-profit corporation chartered by Congress to disseminate radiation protection guidance.

nonstochastic effect

Obsolete. See deterministic effect.

NRC

US Nuclear Regulatory Commission. The federal agency that regulates the use of radioactive byproduct materials. It does not have authority over accelerator-produced radioactive materials or x-rays.

occupational dose

The dose received by an individual in a restricted area or in the course of employment in which the individual’s assigned duties involve exposure to radiation and to radioactive material from licensed and unlicensed sources of radiation, whether in the possession of the licensee or other person. Occupational dose does not include dose received from background radiation, as a patient from medical practices, from voluntary participation in medical research programs, or as a member of the general public.

photon

A quantum of radiant energy. In this manual, the term usually means gamma rays or x-rays.

PO

Purchase Order

public dose

Dose received by a member of the public from exposure to radiation and to radioactive material released by a licensee, or to another source of radiation either within a licensee’s controlled area or in unrestricted areas. It does not include occupational dose or doses received from background radiation, as a patient from medical practices, or from voluntary participation in medical research programs.

quality factor

A modifying factor used to convert dose in rad to dose equivalent in rem. For x-, beta-, and gamma-radiation its value is 1.

rad

Special unit of absorbed dose. One rad is equal to an absorbed dose of 100 ergs/gram or 0.01 joule/kilogram. 100 rads equal 1 gray.

radiation area

An area, accessible to individuals, in which radiation levels could result in an individual receiving a dose equivalent in excess of 0.005 rem (0.05 mSv) in 1 hour at 30 centimeters from the radiation source or from any surface that the radiation penetrates.

RDRC

Radioactive Drug Research Committee (Food and Drug Administration). The RDRC is chartered by the Food and Drug Administration to review and approve basic research projects involving the administration of radioactive drugs to human subjects. CRSC provides this service.

rem

The special unit of any of the quantities expressed as dose equivalent. The dose equivalent in rems is equal to the absorbed dose in rads multiplied by the quality factor. For most forms of radiation, one rem is numerically equal to one roentgen or one rad. One sievert equals 100 rems.

restricted area

An area, access to which is limited by the licensee for purpose of protecting individuals against undue risk from exposure to radiation and radioactive material.

roentgen
(R)

The special unit of radiation exposure. The amount of exposure that liberates one esu of charge per cc of air. For most forms of radiation, one roentgen is numerically equal to one rem or one rad. Although considered obsolete, this term and its abbreviation are still commonly used.

RSC

Radiation General and Medical Safety Committees. This service is provided by the APRS and the LCCs.

RSO

Radiation Safety Officer. The individual responsible for managing the radiation safety or health physics program.

sievert
(Sv)

SI unit of any of the quantities expressed as dose equivalent. The dose equivalent in sieverts is equal to the absorbed dose in grays multiplied by the quality factor. 1 sievert equals 100 rems.

stochastic effects

Health effects that occur randomly and for which the probability of the effect occurring, rather than its severity, is assumed to be a linear function of dose without threshold. Hereditary effects and cancer incidence are examples of stochastic effects.

survey

An evaluation of the radiological conditions and potential hazards incident to the production, use, transfer, release, disposal or presence of radioactive material or other sources of radiation. When appropriate, such an evaluation includes a physical survey of the location of radioactive material and measurements or calculations of levels of radiation, or concentrations or quantities of radioactive material present.

tissue weighting factor

A weighting factor for an organ or tissue relating to the proportion of the risk of stochastic effects resulting from irradiation of that organ or tissue to the total risk of stochastic effects when the whole body is irradiated uniformly.

unrestricted area

An area, access to which is neither limited nor controlled by the licensee.

work area

A portion of a room or laboratory suite where radioactive materials are stored or handled. It is usually a single countertop.

worker

An individual engaged in activities that are licensed by a regulatory agency and controlled by a licensee. Classification as a worker does not require an employer/employee relationship. Volunteers, students on clinical rotation, residents, staff, faculty, and visiting scientists and physicians whose duties include work in radiation or radioactive materials areas are considered workers.

Last Updated: 10-29-2013
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