Chapter 3 : Radiation Characteristics Flashcards
The term “quality” in dental imaging
the energy or penetrating ability of the xray beam
Voltage
measurement of force of the potential difference between two electrical charges
When voltage is increased the speed of the electrons is ______
increased
when the electrons strike the target with greater force and energy, what resutls?
penetrating xray beam with a short wavelength
Measurement of Voltage
Volts (v) or kilovolts (kV)
1 kV equals
1000 volts
Kilovoltage
Maximum voltage of an alternating current
the use of higher kV produces what?
more penetrating xrays
with greater energy
current intra oral settings in kV range
60-70kV
regulates the speed and energy of the electrons and determines penetrating ability of xray
quality
Density
overall darnkess or blackness of an image
if the kV is decreased the resultant image exhibits a _____ density and appears _____
decreased
lighter
increased kV = _____ density (darker)
increased
contrast
differences of dark and light areas in an image
an image with “high contrast” has many ____ areas _____ areas and few shades of ______
black
white
grey
an image with “low contrast” has many shades of ______ instead of areas that are predominently ______ and _____
grey
black
white
exposure time
interval of time during which xrays are produced
impulse
measurement that refers to the fact that xrays are created in a series of bursts or pulses rather than a continous stream
one impluse occurs every _/__ of a second
1/60
kilovoltage and _______ are inversely related
exposure time
Quantity of the xray beam
number of xrays produced in the dental xray unit
amperage
measurement of the amount of electrons passing through the cathode filament
ampere (A)
measures number of electrons, or current flowing in the cathode filament.
One milliamperage (mA)=
1/1000 of an ampere
What does the milliamperage regulate?
temperature of the cathode filament
an increase in the number of electrons that strike the anode ,_______ the number of xrays emitted from the tube
increases
how does milliamperage effect the density of an image
when mA is increased, the overall density also increases which results in a darker image.
increased mA = ____ density & ___ image
higher
darker
KLMN
Kv=quaLity
Ma=quaNtity
higher kV= ____ exposure time
decreased
lower kV = _____ exposure time
increased
increased mA=______ exposure time
decreased
decreased mA= ____ exposure time
increased
intensity
product of the quantity AND quality per unit of area
per unit of time exposure
regulates the penetrating power of the xray beam by controlling the speed of the electrons while travelling between the cathode and anode
kilovoltage
controls the penetrating power of the xray beam by controlling the number of electrons PRODUCED in the xray tube and the number of xrays produced.
milliamperage
as with mA this also affects the number of xrays produced
exposure time
target surface distance
distance from the source (tungsten target in anode) of radiation to the patients SKIN
target object distance
distance from the source (tungsten target in anode) of radiation to the tooth
target-receptor distance
distance from the source (tungsten target in anode) of radiation to the receptor
as x rays travel away from their source of origin, the intensity of the beam _____
lessens
The inverse square law
the intensity of radiation is proportional to the square of the distance from the source of radiation
according to the inverse square law, when the target receptor is doubled, the resultant beam is __/__ as intense
and when the target receptor distance is REDUCED by HALF, the resultant beam is ___ times as intense
1/4
four
The thickness of material (aluminum) that, when placed in the path of the x-ray beam, reduces the exposure rate by one-half.
half value layer (HVL)
If an xray beam as an HVL of 4 mm, a thickness of __ mm would be necessary to decrease its intensity by half
4
