Patient Care in Radiography Chapter 3 Key Terms

ALADA principle

as low as diagnostically achievable

ALARA principle

a principle that states that all radiation exposure to humans should be limited to levels that are as low as reasonable achievable.

centigray (cGy)

the most common unit for calculation of radiation doses in the United States; one one-hundredth of a gray, equal to 1 rad in the British system

coulombs per kilogram (C/kg)

the SI unit for measuring radiation intensity.

deterministic

describes biologic radiation effects that are predictable; their intensity is dose dependent. These effects occur only after a certain threshold amount of exposure has been received; formerly called nonstochastic effects.

dominant

with respect to genes, describes the gene of a gene pair that is expressed in the individual

equivalent dose (EqD)

a measurement of the effective dose of radiation as compared to that of 250 keV x-rays; obtained by multiplying the dose in rad or gray times the weighting factor of the specific type of radiation involved in the exposure and expressed in units of rem (British system) and sieverts (SI system); formerly dose equivalent.

dosimeter

an instrument to detect and measure radiation exposure; a badge worn to measure cumulative occupational exposure.

erythema

redness, or inflammation of the skin or mucous membranes caused by dilation and congestion of superficial capillaries, in radiography, "radiation burn" as a result of radiation treatment.

free radical

temporary molecule, portion of a molecule, or atom with unpaired electron(s) in its outer shell

genetic effects

damage to the reproductive cells of an irradiated person that may be observed as defects in the children or grandchildren of the irradiated individual.

gray (Gy)

the SI unit for radiation dose measurement.

hematologic

blood related

ionization

to separate or change into ions (charged particles).

long-term effects (latent effects)

stochastic radiation effects that usually occur between 10 to 15 years after exposure but may not be apparent for as many as 30 years.

mutation

an unusual change in genetic material occurring spontaneously or by induction.

optically stimulated luminescence (OSL)

type of personnel monitoring dosimeter using aluminum oxide as the radiation detector.

radiation absorbed dose (rad)

the basic unit of absorbed dose of ionizing radiation in the British system. One rad is equal to the absorption of 100 erg of radiation energy per gram of matter and to 1 cGy of dose in the SI system.

radiation equivalent in man (rem)

unit used to measure dose equivalents; determined by multiplying the dose in rad times the weighting factor

recessive

with respect to genes, describes the gene of the gene pair that is not expressed in the individual

roentgen (R, r)

the standard unit of radiation intensity in the British system of radiation measurement. It is a measurement of the intensity of radiation exposure in air. It is equal to the quantity of radiation that will produce 2.08 x 10 to the 8th ion pairs in a cubic centimeter of dry air.

short-term effects

radiation effects observed within 3 months of exposure; deterministic effects

sievert (sv)

the dose-equivalent unit in the SI system that results when the dose in Gy is multiplied by the W(to the power of R)

stochastic

describes biologic radiation effects that are random and unpredictable. Their likelihood is dose dependent but not their severity. There is no threshold amount of exposure necessary to produce these effects.

weighting factor (Wr)

an approximate measure of the relative biologic effectiveness of a particular radiation compared with 250-keV x-rays. It is multiplied by the dose to determine the equivalent dose.