14. B (RADIATION MEASUREMENTS) Flashcards
T or f
Radiation can be measured in the same manner as other physical concepts, such as time (minutes), distance (miles/kilometers), and weight (pounds or kilograms).
T
The International Commission on Radiation Units and Measurement (ICRU) has established special units for the measurement of radiation. Such units are used to define three quantities of radiation:
(1) exposure, (2) dose, (3) dose equivalent.
At present, two systems are used to define radiation measurement:
→ the older system, Traditional System or Standard System
→ the newer system which is the _____, SI System or
Système International de’Unités (International System of Units)
metric equivalent
records the dose received by person wearing it
DOSIMETER BADGE
worn on the surface of the body
DOSIMETER BADGE
determining the quantity of radiation exposure or dose, specifically ionizing radiation
DOSIMETRY
refers to the measurement of ionization in air produced by x-rays
EXPOSURE
measures the intensity of the radiation field as opposed to the amount of radiation absorbed
EXPOSURE
The conversion of roentgen and coulombs per kilogram can be expressed as follows:
1 R = 2.58 x 10^-4 C/kg
1 C/kg = 3.88 x 10^3 R
Definition
1 R = 87 erg/g
Traditional System: Roentgen (R)
Conversion
1 R = 2.58 x 10^-4 C/kg
Traditional System: Roentgen (R)
Conversion
1 C/kg = 3880 R
SI System: Coulombs per kg
the amount of energy absorbed by a tissue
DOSE
measures the total energy absorbed by any type of ionizing radiation per unit of mass of any type of matter
DOSE
varies with the type and energy of radiation and type of matter absorbing the energy
DOSE
Definition
1 rad = 100 erg/g
Traditional System: Radiation absorbed dose (rad)
Conversion
1 rad = 0.01 Gy
Traditional System: Radiation absorbed dose (rad)
Definition
1 Gy = 0.01 J/kg
SI System: Gray (Gy)
Conversion
1 Gy = 100 rads
SI System: Gray (Gy)
The conversions of rad and gray (Gy) can be expressed as follows:
1 rad = 0.01 Gy
1 Gy = 100 rads
measurement used to compare the biologic effects of different types of radiation
DOSE EQUIVALENT
ex.:
o alpha particles penetrate only a few mm of tissue, loses all
their energy and are totally absorbed; whereas x-rays penetrate much farther, lose some of their energy, and are only partially absorbed
DOSE EQUIVALENT
the biological effect of a particular absorbed dose of alpha particles would therefore considered as more severe than similar radiation absorbed dose of-xrays
DOSE EQUIVALENT
Definition
1 rem = rads x QF
Traditional System: Roentgen equivalent (in) man (rem)
Conversion
1 rem = 0.01 Sv
Traditional System: Roentgen equivalent (in) man (rem)
Conversion
1 Sv = 100 rems
Sievert (Sv)
Definition
1 Sv = Gy x QF
Sievert (Sv)
The conversions of rem and Sievert can be expressed as follows:
1 rem = 0.01 Sv 1 Sv = 100 rems
unit of electrical charge; the quantity of electrical charge transferred by 1 ampere in 1 second
Coulombs
unit of electrical current strength; current yielded by 1 volt against 1 ohm of resistance
Ampere
unit of energy equivalent to 1.0 x 10^-7 joules or to 2.4 x 10^-8 calories
Erg
SI unit of energy equivalent to the work done by the force of 1 newton acting over the distance of 1 meter
Joule
SI unit of force; the force that, when acting continuously on a mass of 1 kg, will impart to it an acceleration
Newton
unit of mass equivalent to 1000 grams or 2.205 pounds
Kilogram
in dental radiography, the gray and sievert are equal and the roentgen, rad, and rem are considered approximately equal
MEASUREMENTS USED IN DENTAL RADIOGRAPHY
smaller multiples of these radiation units are typically used in dentistry because of the small quantities of radiation use during radiographic procedures
MEASUREMENTS USED IN DENTAL RADIOGRAPHY
