Rule 1 shadow casting
xrays should be emitted from the smallest source of radiation as possible
Rule 2 shadow casting
the xray source (focal spot or target) to the object (oral structure) distance should be as long as possible
Rule 3 shadow casting
The object (tooth) to film distance should be as short as possible
Rule 4 for shadow casting
The film andlong axis of the object (oral structure) should be parallel.
Rule 5 for shadow casting
the xray beam should be placed perpendicular to film
geometric characteristics (factors) is also called?
shadow casting
which of the following factors effect contrast?
development time
development tempature
KVP
Decrease mA causes
increase exposure time
decrease intensity
decrease density (lighter)
decrease quantity
Increase mA causes
decrease exposure time
increase intensity
increase density (darker)
increase quantity (amount, #)
increase temp. of cathode
Increase KVP causes
#NAME?
Decrease KVP causes
decrease density
decrease intensity
less energy
long wavelength
high contrast
short scale
In dental radiography, the term ___ is used to describe the energy, power, or penetrating ability of the xray beam
quality
Xrays with longer wavelengths have ___ penetrating power.
less
Xrays with longer wavelengths are _____ likely to be absorbed by matter.
more
When the voltage is increased:
electrons move from the cathode to the anode with more speed.
dental xray equipment requires the use of less than __ kilovolts.
95
Density
the overall drakness or blackness of a film
When the kilovolt peak is increased hile other exposure factors remin constant, the resultant film exhibits a decreased density and appears?
darker
Quantity of the xrays produced is controlled by:
milliamperage
Amperage regulates the ____ of electrons produced at the cathode filament.
quantity, number
20 mA with an exposure time of 2 seconds would result in 40 mAs. If the milliamperage is decreased to 10, th time must be increased to ___ seconds to maintain the same density of tge exposed radiograph.
4
If a dental hygienist makes a radiograph with an 8 inch PID at 5 for the exposure time, but she moves to another room and uses the 16 inch PID, what would her new exposures times need to be?
20
If the exposure was 20 impulses at 8 inches and we use a 16 inch BID. what will the new impulses be?
80
10 mA for .6 = 15 mA for ___s?
0.4
one impulse occurs every 1/60th of a second. 60 impulses equal one second
1/10 second = ___ impulses
1/20 second = ___ impulses
1/30 second = ___ impulses
6
3
2
If you used an exposure of 20 impulses with the 16in, what is the new exposure time with 8in PID?
5
A dentist is using the exposure at 15mA and 2 seconds, then decides to change to 10mA, the new time required is?
3
Decrease focal spot size = _____ sharpness
increase
Increase crystal size = _____ sharpness
decrease
Decrease crystal size = ____ sharpness
increase
Decrease movement = ____ sharpness
increase
Increase movement = _____ sharpness
decrease
Increase target-receptor distance = _____magnifcation
decrease
Increase object-receptor distance = ____magnifcation
increase
Decrease object-receptor distance = ____magnifcation
decrease
Object and receptor are parallel = ___ distortion
decrease
Beam perpendicular to object and receptor = ___ distortion
decrease
Beam not perpendicular to object and receptor = ___ distortion
increase
The capability of the receptor to reproduce distinct outlines of an object is called?
sharpness
The unsharpness or blurred edges seen on a radiographic image is
penumbra
The geometric characteristic that refers to a radiographic image that appears larger than its acual size is called?
magnification
A variation in the true size and shape of the object being radiographed is called?
distortion
To minimize dimensional distortion, the xray beam must be directed ____ to the tooth and the receptor.
perpendicular
To create a sharp image the dental radiographer uses?
- smallest focal spot
- film smallest crystal emulison
- limits movement of patient, tubehead,& receptors
To limit image magnification the ___ and ____ are used.
longest target-receptor distance
shortest object-receptor distance
To limit image distortion the receptors and tooth are positioned _____ to each other, and xray beam is directed ____ to the tooth and receptor.
parallel
perpendicular
A decrease in object-receptor distance results in a _____ in magnification.
decrease
A increase in object-receptor distance results in an ___ in image magnification.
increase
A longer PID and target receptor distance results in ____ image magnification.
less
The target receptor distance is determined by the?
the length of the PID
Magnification or enlargement of a xray results from ____?
divergent paths of xray beam
xrays travel in diverging straight lines as they radiate from?
focal spot
target-receptor distance is also known as?
source to receptor distance
The sharpness of an image is influenced by the following 3 factors?
focal spot size
film composition
movement
focal spot is?
small area converts bombarding electrons into xray photons
The size of the focal spot is determined by the ______?
manufacturer of the xray equipment.
The smaller the focal spot area the ____ image appears.
sharper
The larger the focal spot the ____ is the loss of image sharpness.
greater
The half-value layer is the amount of?
aluminum needed to reduce xray beam intensity by half
The length of the PID is changed from 16 to 8in. The resultant intensity of the beam will be?
four times as intense
When you increase the intensity of the xray beam you increase what 3 items?
kilovoltage
milliamperage
exposure time
To increase the penetrabililly of xrays, thier wavelengths should be?
shortened by increasing the KVP
When you increase film density you what?
increase the mA
increase the KVP
increase the time
decrease the distance
Contrast is primarily a funcion of ?
KVP
The "mean" penetrablility of xray beam is not related to ____?
mA
Exposure factors are:
whatever you can adjust when you are taking a xray
Examples of exposure factors are?
KVP
Filtration
mA
Exposure time
target to film distance
Kilovoltage is
a measurement of force and energy
Milliamperage
a measurement of the number of electrons flowing through the cathode filament
The total energy contained in xray beam in a specific area at a given time is?
intensity
Increasing miliiamperage alone results in an image with _____?
increased density
A radiograph with high contrast was produced with ___?
low milliamperage
A radiograph that has many light and dark areas with few shades of gray is said to have?
high contrast
Identify the term that describes how dark and light areas are differentiated on an image:
contrast
If kilovoltage is decrease with no other variations in exposure factors, the resultant image will:
appear lighter
The overall blackness or darkness of an image
density
Identify the milliamerage range for dental radiography?
7 to 15 mA
Increasing milliamperage results in an increase in 2 things:
temp of filament
number of xrays produced
In dental radiography, the quantity of radiation produced is controlled by 2 things?
millliamperage and exposure time
Radiaion produced with high KVP results in?
short wavelengths
Identify the unit of measurement used to describe the AMOUNT of electric current flowing through the xray tube?
ampere
A higher KVP produces xrays with?
greater energy levels
shorter wavelengths
more penetrating ability
Identify the KVP range for the most dental xray machines?
65 to 100
In dental radiography, the quality of the xray beam is controlled by?
KVP
Source to receptor distance means
if you go from 8in to 16in PID
Wavelengths determines what?
energy and penetrating power of radiation
Shorter wavelengths have ___ power.
more
Longer wavelengths have ___ power.
less
Quality
describes the mean energy or penetrating ability of xray beam
Voltage is
measurement of force that refers to the potential difference b/w 2 electrical charges
Voltage determines the ____ of electrons that travel from cathode to anode
speed
Volt is
unit of measurement used to describe the potential that drives an electrical current through a circuit
A ___ KVP should be used when the area to be examined is dense or thick.
higher
The use of 85 to 100 KvP produces ___ penetrating dental xrays with ___ energy and ____ wavelengths
more
greater
shorter
The use of 65 to 75 Kvp produces ___ penetrating dental xrays with ___ energy and ____ wavelengths.
less
less
longer
KVP
the maximum or peak voltage that is used during an xray exposure
polychromatic xray beam
many different wavelengts of varying intensities is produced.
high contrast is
has many black areas and many white areas
low contrast is
has many shades of gray instead of black and white
An image of high contrast is useful for the detection and progession of ____?
dental carries
An image with low contrast is useful for the detection of ____ or ____?
periodontal and periapical diease
Exposure time refers to?
the interval time during which xrays are produced
Exposure time is measured in _____?
impulses
Amperage
increase in the number of electrons available to travel from the cathode to the anode
quantity is
to the number of xrays produced in dental xray unit
ampere (A)
unit of measure used to describe the number of electrons current flowing through the cathode filament
The number of amperes needed to operate a dental xray unit is _____.
small
one milliampere is equal to ____ of an ampere.
1/1000
Quality and quantity are both described together as _____?
intensity
target-surface distance
the distance from the source of radiation to the patients skin
target- object distance
the distance from the source of radiation of the tooth
target receptor distance
the distance from the source of radiation to the receptor
receptor is
film or digital sensor
The xray beam from an 8in PID is ____ intense than a 16in PID
more
inverse square law
intensity of radiation is inversley proportional to the square of the distance from the source of radiation.
Inversely proportional means
one variable increases while the other decreases
If the source to receptor distance is doubed. According to the inverse square law, the result beam is ____ intense.
04-Jan
If the source to receptor distance is reduced by half. According to result beam is ____ as intense.
4 times
Aluminum filters are used to remove the ___ , _____ and ____ of xrays.
low energy
less penetrating
long wavelengths
Aluminum filters are placed in the path of the beam to ______.
reduce intensity
Mesuring the half-valaue lyer determines the ________ of the beam,
penetrating quality
The portion of processed radiograph that appears dark or black is?
Radiolucent
THe portion of a processed radiograpgh that appears light or white is?
Radiopaque
What appears most radiolucent on denta radiograph?
air space
Examples of radiopaque stuctures seen on dentak xrays are?
bone, enamel,dentin
Increasing the milliamperage will cause?
increase in density & image appears darker
Increasing the KVP will cause?
increase in density & image appears darker
Increasing the exposure time will cause _____?
increase in density & image darker
A dental patient has thick soft tissues and dense bones. To compensate for this increase in subject thickness and provide image of good density. What way is the LEAST harmful?
increase KVP
When viewed on a light source, a dental radiograph that demonstrates many shades of gray is said to have?
low contrast
When viewed on a light source, a dental radiograph that demonstrates very dark areass and very light areas is?
high contrast
The type of contrast preferred on a dental radiograpgh is?
a compromise b/w short-scale and long-scale contrast
Contrast is
difference in the degrees of blackness b/w adjacent areas on dental xray
Is film processing under control of the dental radiographer?
yes
Development time of the temperature of the developer solution affects the contrast of a denal xray known as?
generic factor of film
Subject contrast determined by
the thickness, density and composition of the subject
Scale of contrast is?
the range of useful densities seen on a dental radiograph
Short-scale contrast
only shows 2 densities = black & white
have lower kvp, high contrast
long-scale contrast has
many densities, many shades of gray
have higher kvp, low contrast
Stepwedge
device to demostrate short and long scale
monitor quality control of film
demonstrates densities
uniformed layered thickness