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Radiology Finals

Terms in this set (186)

x-rays are generated when a stream of electrons traveling from one side of a x-ray tube head is suddenly stopped by the impact with the:
tungsten target of the anode
the mA setting controls:
the heat of the tube head filament; the number of free electrons in the tube; number of protons ultimately produced; the density of the film -- NOT the speed of electrons moving from the cathode to the anode
the mean penetrability of an x-ray beam is NOT related to:
mA
Increasing the kVp results in
a long scale of contrast
He is the father of radiation protection:
Rollins
The electron that has the greatest binding power to the nucleus is:
K - closest to the nucleus
When an electron is removed from an atom:
an ion is produced
The density of an x-ray film can be influenced by:
kVp, and mA
The x-ray was discovered by:
Roetgen
A radiograph is defined as
A picture on film produced by passage of x-rays through a object or body
Which of the following statements is true regarding the importance of dental radiographs
Many dental disease are discovered through radiographs alone
The density of the radiograph is decreased when the ___________ is increased
subject thickness
the total transfer of energy from the x-ray photon to the atoms of matter which the x-ray beam passes
...
as x-ray wavelengths is increased, the frequency of the individual x-rays will
decrease
physical distance between two successive crest peaks
wavelength
something has caused a hole in an inner shell of an atom. What type of radiation will this be
gamma radiation
in addition to x-rays, what is produced in the x-ray tube during normal tube operation
heat
the quality or penetration power, of secondary radiation is:
less that than of primary radiation
the unit of electrical potential difference or force is called
volt
the unit of electrical quantity is called:
ampere
as x-ray energy is decreased, penetrating power will
decrease
this x-ray control determines the beam energy and penetrating power
kVp
when the operator changes impulses what is being changed
exposure time
the lead diaphragm in the tube head is referred to as the
collimator
Identify the substance found in the x-ray tube head that functions to help dissipate the heat
oil
which of these terms describes an electromagnetic device within the x-ray tube head for changing voltage of aternating current
...
transformer
A device that increases or decreases the voltage of alternating current
x ray beam absorption depends on
the energy of the x-ray beam, the composition of the absorbing matter
which prime factor is manipulated when using the 15% rule
kVP
exposure time and mA are directly proportional to each other
false
which is the controlling factor or factors for image contrast? Mark all correct answers
(only) kVp
radiopaque refers to that portion of processed radiograph that is
white
the intensity of x-ray beam is inversely proportional to the square of the exposure distance -
inverse square law
potential voltage
What is the kVP
focal trough
The area of sharp focus in panoramic radiography is known as the
The vertical angulation in the tubehead of the panoramic unit
is fixed in position so the x-ray is described slightly upward
thermionic emission occurs at the
the negative cathode
step-down transformer
Used to decrease voltage from the incoming 110- or 220-line voltage to the 3 to 5 volts used by the filament circuit.
Density is the overall darkness or brightness of a film
first statement is true second statement is false
a film with low contrast
is useful for the detection of periodontal or periapical disease. n has many shades of gray.
the half-value layer is
the amount of aluminum need to reduce the intensity by one-half
the best x-ray to penetrate body tissue is:
hard waves, short wavelenghts
which best describes a film with many shades of gray from completely black to white
long scale contrast
if the operator wants to change from short-scale contrast to long scale contrast technique and maintain the density
increase kVp and decrease mA
Radiation
emission of energy through space or substance in the form of waves or particels
Radioactivity
Process by which certain unstable atoms or elements undergo spontaneous disintergration, or decay, in an effort to attain a more balanced nuclear state
in panoramic radiography, which of the following exposure factors cannot be changed
exposure time
A lead apron _____ a thyroid collar should be used when exposing a panoramic film, and the patient should be told to raise the tongue up to the_________
without, palate
A reverse smile line is seen on the radiograph if the patient's
chin is tipped up
The anterior teeth will appear skinny if the
teeth are positioned too far foward on the bite-block
A disadvantage of panoramic dental radiography when contrasted with intraoral dental radiograph
the images seen on a panoramic radiograph are not as sharp as those on intraoral because of intensifying screens
Which of the following is NOT an accurate description of an intensifying scree
reflecting layer directs the light produced toward the screen
What specific mechanisms of radiation injury may result in the formaiton of hydrogen peroxide when energy is absorbed by patient tissues
free radical formaiton created by the ionization of water
which of the following mechanisms of radiation injury may occur when x-ray energy is absorbed by patient tissues
ionization, free radical formation
the indirect theory proposes that
free radicals combine to form toxins - both a and b
stochastic biologic effects from radiation
occur as a direct function of dose
Examples of nonstochastic effects include
erythema, loss of hair - both a and c
which of the following types of cells are radiosensitive
blood
which of the following are considered radioresistant (?)
salivary glands
Critical organs exposed in dental radiography
skin, thyroid glands, lens of eye and bone marrow
The traditional unit of dose
RAD
the si equivalent of rem
sievert
F speed instead of d-spped reduces the absorbed dose by
60
which modifications in technique reduce patient exposure
a longer source-to-film distance
somatic effects
effect of radiation exposure that are expressed in exposed person rather than offspring
total dose
Quantity of radiation received or total amount absorbed (more damage with tissue absorbing large quantities of radiation)
The collimator
controls the size and shape of the x ray field coming out of the x ray tube; controls secondary radiation
Circular collimator
produces a cone-shaped beam that is 2.75 inches in diameter
16-inch rectangular PID
most effective in reducing patient exposure
thyroid collar
May exists as a separate shield or as part of a lead apron; used in intraoral films not extraoral films
to avoid radiation during processing the radiographer must be positioned
90-135 degree angle
current MPD to occupationally exposed
5.0 rem
ALARA
As Low As Reasonably Achievable
Vertical bite wings can often be used for:
bone loss
On bite wing the indicator dot
has no significance
Vertical bite wing
size 2: with vertical position
Vertical angulation
downward, and is termed positive
premolar bite-wing position
midline of the mandibular canine
molar bite wing
mandibular first molar
which of the following is FALSE regarding dental x-ray film regarding formation of latent image
all crystals must be exposed and energized in order for there to be a latent image
Which component of film provides stable support
film base
The emulsion is softened and the exposed silver halide crystals precipitate in the
developing cycle
the film emulsion is composed of a homogenous mixture of
gelatin and silver halide crystals
the latent image on a radiograph
An unseen image produced by silver halide crystlas that have been exsposed to radiation and thus levels of stored energy, making a pattern
the areas of film that are_____energized will be ______ when film is processed
more; darker
latent image centers are aggregates of
Neutral silver atoms
during formation of the latent image, irregularities in the lattice structure of the exposed are a result of ________ attract silver atoms
the emulsion
a two film packet requires
the same amount of exposure time
the two film packet may be used
when a duplicate is needed
the identification dot is used to
determine film orientation
what is the purpose of the lead foil sheet found within the film packet
to sheild the film from necessary background radiation
the thin lead foil sheet is positioned
behind the film
the embossed pattern placed on the lead foil sheet by the manufacturer will reveal
If the film packet is inadvertently positioned in the mouth backward and then exposed.
the tube side of the dental film
solid white
during the chemical processing the, the fixer
removes the unexposed silver halide crystals leaving light or clear spots where those crystals used to be
which type of intraoral film is best for visualizing interproximal surfaces
bitewing
A fast film responds more quickly than a slow film because
the silver halide crystals in the emulsion are larger
screen film
is sensitive to fluorescent light
the fixing agent that clears the unexposed crystals is
amonium thysulfite
an intensifying screen is a device that transfers x-ray energy into visible light. The visible light in turn, exposes the screen film
TRUE
lack of contact between screen and film result in
a loss of image sharpness
duplicating film
not exposed to x-rays and has emulsion on one side only - both a and c
which of the following areas would appear the most radiolucent on a dental radiograph
airspace
radiopaque refers to the portion of processed radiograph that is
white
if the mA is increased the film density is
increases and appears darker
which of the following changes will result in a radiograph with a reduced density
increasing the subject thickness
a radiograph that has _____ is said to have a low contrast
many shades of gray
an increase ________ temperature will result in film with an increase contrast
development
the range of useful densities seen on a radiograph is termed the
scale of contrast
a step wedge will reveal that radiographs taken at higher kVp will have ________ vs. radiographs taken at a lower kVp
long scale contrast
The geometric characteristics of _______ refers to the capability of the x-ray film to reproduce distinct outlines of an object
sharpness
which of these films is best suited when the dentist requests a radiograph that examines of the structures of large area of the maxilla
occlusal
the floating thermometer for manual processing should placed in
the developing solution
which of the following influencing factors would degrade film sharpness
larger silver halide crystal size, lager focal spot - d
which of the following factors would improve image sharpness
smaller crystal size,
which of the following choices would result in an increased magnification
increase object-film distance
a longer PID results in
an increase target-film distance
to minimized dimensional distortion the object and film should be
parallel to one another
the latent image is
the image on the radiograph film before processing but after expoure
during processing a chemical reaction occurs and the halide portion of the ________ silver halide crystal is removed
exposed, energized
The developer initiates a chemical reaction that reduces the exposed silver halide crystals into metallic silver, but it leaves the unexposed silver halide crystals uneffected
TRUE
Which of the following possibilities is the correct processing order for manual tanks
development, rinsing, and fixation
the film emulsion is hardened during which of the following stages of development process
fixation
______ generates the black tones and the sharp contrast of the radiographic image
hydroquinone
optimal temperature for the manual developer is
68
the primary reason that automatic processors are faster
higher developing temperatures
elon generates the _______ seen on dental radiographs
many shades of gray
if film if processed below 60 F
hydroquinone would be inactive, but elon would be active
which of the following chemicals is the accelerator in the developer solution
sodium carbonate
developer agents are only active in a ______ enviroment
a and b - alkaline/basic or high pH
the restrainer stops the development of
unexposed crystals more than exposed crystals
Which of component of fixer solution is commonly known as hypo:
sodium thyosulfite
the purpose of the fixing agent is to remove all_______ from the film emulsion
unexposed silver halide crytals
the hardening agent used in the fixer solution is
potassium alum
the acidifier used in fixer solution
acetic acid
any leaks of white light in the dark room cause film:
fog
safelighting is a _______ intensity light composed of _______ wavelengths of the visible light spectrum
low; long
the optimal temperature for film storage ranges from
50-70
which of the following statements is true of automatic film processors
only - automatic film with daylight loaders may used in a room with white light
an overall graying of the film decreasing diagnostic visibility could result from which of the following
all of the above
an exhausted developer produces a radiograph with
reduced density and reduced contrast
an exhausted fixer produces a radiograph
yellow-brown color because exhausted fixer does not stop chemical reaction
a major advantage of automatic film processing vs. manual
less processing time is required
reticulation means the film appears
cracked
insufficient fixation time or insufficient rinsing would lead to
yellow brown film
developer cut-off appears as
straight white border on film
a calibration test for accurate kilovoltage and mA readings would most likely would ensure the _______ is functioning properly
dental x-ray
according to the test for dental x-ray film if the process film appears clear with a slight blue tint
the film is fresh and properly stored and protected
to conduct a film screen contact test, the wire mesh test object is placed
on top of loaded cassette
the viewbox should emit a uniformed and subdued light when it is functioning properly. Permanent discolored plexiglass surfaces and blackened fluorescent light bulbs must be placed
TRUE
During the light leak test for the dark room
all the lights within the dark room should be off
safelighting can be tested with the
coin test
the image of the coin appears on the processed radiograph after the coin test
safelighting is not safe with that film
Two tests the automatic film processor_________ in the automatic film processor
unwrap to unexposed films, expose one to light, and then process both films
If the processor is functioning properly the results of automatic processor test films will be
an unexposed film appears clear and dry, and the exposed film appears dark and dry
If the density seen on a daily radiograph appear darker on those seen on the reference radiographs the developer solution
too concentrated, and too warm - d
the clearing test is used to monitor
fixer strenght
radiographs are a _______ comprehensive patient care
necessary component of
the electric current in the x-ray tube flow in only one direction
from cathode to anode
the higher the _______ the greater the speed of electrons as they strike the target
potential voltage
panoramic films used over intraoral periapical films include visualization of
impacted third molar teeth, jaw fractures, and large lesions in the posterior mandible - 1,2,3
in the panoramic radiography the pivotal point or access in which the cassette carrier or the tubehead is
rotation center
the rotational change in a panoramic machine allows the image layer to conform to the ______ shape of the dental arches
elliptical
the collimator used on panoramic radiography has a opening in the shape of a ________ slit
narrow, vertical
which selection below correctly describes the image destortion produces when the patient's midsagittal plane is not centered
structures on one side of the image are narrowed and the other side is widened
when the patient's head is positioned too far backward the clinician will NOT observe
the structures on one side will be narrower than the other
which of the following phases is NOT consistent with panoramic ghost images
appear on same side as original side of same object
what error will cause the production of a radiopaque wedge-shaped artifact near the midline
the lead apron was place to high on the back of the patient's back
the ______ radiation received and the _______ dose rate, the shorter the latent period
more; faster
which type of cells are more sensitve to radiation
rapidly dividing; young
_______ is an example of a patient protection technique used before radiation exposure
proper prescribing of radiographers
inherent filtration in the dental x-ray tubehead
includes filtration that takes place when the primary beam passes through the glass window of the x-ray tube, the insulating oil, and tubehead seal
Added filtration in the dental x-ray tubehead refers to
results in more penetrating useful beam.
The state and federal require that dental x-ray machines operating above 70 kVp have a minimum total of aluminum filtration
2.5
the receptor is placed in the mouth parallel to the long axis of the tooth being radiographed
in parallel technique
the central ray of the x-ray beam is directed perpendicular at a right angle to the receptor and the long axis of the tooth
the paralleling techniqe
the object-receptor distance
must increased to keep the receptor parallel with the long axis of the tooth
to compensate for image magnification, the target receptor distance must also be increased
in paralleling technique
if the lack of parallelism between the receptor and the long axis of the tooth does not exceed 20 degrees, the resultant image is generally acceptable
...
rule of isometry
two triangles are equal if they have two equal angles and share a common side
vertical angulation -
the central ray of the x-ray beam must be directed perpendicualr to the imaginary bisector that divides the angle formed by the receptor and the long axis of the tooth
mandibular cross-sectional occlusal projection
used to examine the buccal and lingual aspects of the mandible
extraoral projection is typically used
to evaluate the tempromanibular joint, oral surgery
Lateral jaw projection of the ramus of mandible
to evaluate impacted third molars
the x-ray unit time must be adapted to allow exposures in a time frame of 1/100 of a second
in digital imaging
Storage phosphor imaging
the images are cleared from the plates by exposure to viewbox light for several minutes, or the images may be erased from the plates immediately after the scanning process
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