Ch 4 Radiation quantities And Units Flashcards
(35 cards)
From ____________ the unit for measuring radiation exposure was for the skin erythema dose
1900-1930
Defined as the received quantity of radiation that causes diffuse redness over an area of skin after irradiation?
Skin erythema dose
Why was skin erythema dose an often crude inaccurate way to quantify radiation exposure?
Because the amount of radiation required to produce an erythema reaction varies from one person to another.
The first international congress of radiology was held where and what year?
London, England in 1925
International commission of radiation units and measurements (ICRU) was formed in
1925
Is a dose to which occupationally exposed persons could be subjected without any apparent harmful acute effects, such as erythema of the skin?
Tolerance dose
Dose of radiation lower than which an individual has a negligible chance of sustaining specific biologic damage?
Threshold dose
Maximum permissible dose (MPD), was initially expressed in_______ and has since been replaced by the unit______
Rem
SI, sievert
Irradiation of _________ was found to be much more significant to the whole body health of an individual than irradiation of the _______.
Bone marrow
Skin
At ICRP adopted the term________, based on the energy deposited in biologic tissue by ionizing radiation and takes in account both of the following: ______________ and __________\
Effective dose (EfD)
The type of radiation
The variable sensitivity of the tissue exposed to the radiation
EfD is expressed in_____ and is the best measure of the overall risk arising from the simultaneous irradiation of various biologic tissue and organs within an individual.
SI unit, Sievert
____ is the the traditional unit for the radiation quantity equivalent dose (EqD)
Rem
Relates to the ionization produced in a small cavity within an irradiated medium or object to the energy absorbed in that medium as a result of its radiation exposure.
The Bragg-Gray theory
As the intensity of X-ray exposure of the air volume _________, the number of electron ion pairs produced________
Increases
Increases
Radiation ionization in air is termed?
Exposure
Amount of radiation responsible for the ionization of a well defined volume of air may be determined by measuring the number of electron-ion pairs or charged particles of either sign in that volume of air, this is termed found known as?
Exposure
Is defined as the total electrical charge of one sign, either plus or all minus, per unit mass that X-ray and gamma ray photons with energies up to 3 million electron volts generate in dry air at standard temperature and pressure
Exposure
Basic unit of electrical charge?
Coulomb (C)
Is another SI quantity that is used to express how energy is transferred from a beam of radiation to air
Air kerma
Is the total kinetic energy released in a unit mass of air and is expressed in metric units of joules per kilogram.
Air kerma
The sum total of air kerma over the exposed area of the patients surface or in other words a measure of the amount of radiant energy that has been thrust into a portion of the patients body surface
Dose area product
Amount of energy per unit mass absorbed by an irradiated object
Absorbed dose
Is the amount of energy transferred on average by incident radiation to an object per unit length of track, or passage, through the object and is expressed in units of kilo electron volts per micrometer.
Linear energy transfer (LET)
Radiation with ______ LET transfers a large amount of energy into a small area and can therefore potentially do much more biologic damage than radiation with a ____ LET.
High
Low
