film screen radiography Flashcards
The ____ beam refers to the x-rays that remain as the useful beam exits the pt. It consists of x-rays scattered away from the IR and image-forming x-rays.
exit
The medium that converts the x-ray beam into a visible image is called the _____ ________.
image receptor
The two basic components of radiographic film are the ________ and the __________.
base and emulsion
Modern radiographic film base is made of __________.
polyester
How thick is radiographic film base?
150-300 um
The important characteristics of radiographic film base are lucency and
dimensional stability
The main purpose of the gelatin emulsion in radiographic film is to
hold the silver halide crystals
Crystals in film emulsion consist of __________ and ___________.
Silver bromide and silver iodide
The overcoat on radiographic film is a protective covering of ____________.
Gelatin
Latent image formation occurs during film _________.
exposure
A contaminant in the silver halide crystal creates the
Sensitivity speck
Direct exposure film has a _______ emulsion and _______ silver halide crystals than screen-film.
Thicker ,more
The latent image can be seen
only after development
Photon interactions free the electrons from __________ atoms in the silver halide crystal.
Both A and B . Bromide and iodide
The latent image is made up of _________ atoms.
Silver
Photon interactions in the emulsion occur with exposure to ________.
Both A and B. X-rays and light?
The most commonly used radiographic film is __________.
Screen film
The size, shape, and distribution of silver halide crystals determine _________ of screen-film.
Speed, contrast , and sensitivity
The contrast of film is inversely proportional to its ______.
Latitude
High contrast film contains _______ silver halide crystals of ______ size.
Smaller and uniform
Film is made with double emulsion to enhance film __________.
Speed
Spectral matching is not a consideration when using
Direct exposure film
Orthochromatic film is used with rare earth screens because of its sensitivity to ________ light.
Green
What is a reasonable maximum storage time for radiographic film?
45 days
Film fog on unprocessed film will occur with radiation exposure as low as _______.
0.2 mr
Storing film in very low humidity conditions can cause
Static artifacts
Film should be stored at a temperature of _____ or below and with humidity no higher than
68 F , 40%
The layer of screen that lies closest to the film is the _______________.
Protective coating
The light-emitting efficiency of the intensifying screen is improved by the
Reflective layer
Screen characteristics are determined by
All of the above. Size of phosphor crystals, thickness of phosphor layer, & phosphor composition
A phosphorescent material emits light
For a period of time after stimulation
An intensifying screen is an example of _______________.
Luminescence and fluorescence
Luminescent material emits light after its outer shell electrons are
Excited
A screen that emits light after an exposure terminates is exhibiting
screen lag
The intensification factor is a measurement of screen _________.
Speed
The intensification factor is the exposure required ___________ divided by the exposure required ___________.
Without screens , with screens
The intensification factor increases with increased ____________.
Kvp???
The ability of an intensifying screen to absorb x-rays is called
Detective quantum efficiency
Image noise is increased with increased
Conversion efficiency
What is the formula for conversion efficiency?
CE= (emitted light/ # of X-rays absorbed) x 100
Both the isotropic emission of light from screen phosphor crystals and the added reflective layer contribute to
Image blur
Spatial resolution is improved when a screen has
Added absorbing dye
Image blur is generally increased by any factor that increases the
Intensification factor
A fine detail screen can resolve ___ lp/mm.
15
About ___% of the latent image on the film is created by light from the screens.
99%
The use of screens greatly increases
Tube life
The back cover of the cassette is usually made of ______ material to reduce backscatter.
High z
A disadvantage of the speed of rare earth screens is the increase in
Quantum mottle
Intensifying screens wear out because of
Improper handling
If a film is used without spectral matching, the result would be a reduction in
Optical density
In a busy department, screens should be cleaned ______.
Monthly
An annual wire mesh test is needed to check for
Worn felt contacts
Film that has emulsion coated on both sides is called what?
double-emulsion film
Between the emulsion and the base is a thin coating of material called the ________ _____, which ensures uniform adhesion of the emulsion to the base.
adhesive layer
The ________ layer allows the emulsion and the base to maintain proper contact and integrity during use and processing.
adhesive
The emulsion is enclosed by a protective covering of gelatin called the ________.
overcoat
What is the most commonly used radiographic film type?
screen-film
After an interaction of the x-ray is either totally absorbed or partially absorbed. If it is totally absorbed it is called?
photoelctron
After an interaction of the x-ray is either totally absorbed or partially absorbed. If it is partially absorbed it is called?
compton
The phosphor converts the xray beam into…?
Light
During WWI when glass became largely unavailable, what became its substitute as film base? What is this substitute’s deficiency?
Cellulose nitrate ; it’s flammable
By the mid-1920s, a new “safety base” for film was introduced. What material was it made of?
cellulose triacetate
The emulsion consists of a homogeneous mixture of _______ and ______ ______ ________.
Gelatin and silver halide crystals
The emulsion layer of film is _ to _ µm thick.
3 to 5
_______ grains are used in most radiographic films.
Tabular
High ratio grid has higher/lower contrast improvement factor ?
Higher
The higher the grid ratio the higher/lower is the Bucky factor
Higher
Bucky factor increases with increasing/decreasing Kvp
Increasing
What is the purpose of a moving grid
To remove grid lines
What are the different types of grid motions used ?
Reciprocating and oscillating grid
How will the image appear if the grid is off level?
Grid cutoff across image, underexposed, light image (loss of density ). Same as of center
How will the image appear if the grid is off center ?
Grid cutoff across image, underexposed, light image (loss of density ) same as off level
How will the image appear if the grid is of focus?
Grid cutoff on one side of the image
How will the image appear if the grid is placed upside down?
Grid cutoff toward the edge of the image
You can improve the image contrast on a heavy patient without increasing the patient dose by
Tight collimation
Beam restriction with an ……. Is only accurate at a fixed SID.
Aperture diaphragm
Higher kvp …….patient dose…..and image contrast.
decreases, decreases
The most commonly used beam restricting device is the…..?
variable collimator
The use of a compression device will increase …….on the image.
Contrast
Photoelectric interactions increase when ……is decreased.
kvp
What are the three best ways to improve contrast resolution?
?
The three primary factors influencing the intensity of the scatter in the image forming bean are :
Kvp,field size, and patient thickness
Quantum mottle is controlled by
mAs
In long scale contrast density is
Increased
In short scale contrast density is
Decreased
Voltage ripple:
High frequency < 1 %
Half wave 100%
Full wave 100%
3 phase 6 pulse 13% 12 pulse 4%
Name the 4 types of body habitus
Hypersthenic (5%)
Sthenic(50%)
Hyposthenic (35%)
Asthenic(10%)
The main disdvantage of parallel crossed _________
Grid cutoff
Focal spot blur can be reduced by using a ______ focal spot, large SID, small OID.
Small
The 3 prime geometric factors affecting image quality ________
magnification,distortion, forcal spot blur
In general radiography, the useful optical densities lie between _____and ______
0.25-2.25
An IR with ______ can be used over greater image range of exposure
Wide latitude
Spatial resolution improves with decreased ___________________________
screen, motion, geometric blur
WIth automatic exposure control (AEC) the exposure is terminated when the optimum _____is reached.
OD
Sharpness of detail can be improved by increasing ______
SID
At least a ______ change in mAs is necessary to produce a visible change in OD.
30%
Using high frequency and or high ratio grid results in ____________patient radiation dose.
increase
The use of ________ imprves contrast and reduces patient does.
collimation
The main diadvantage of parallel crossed _________
Grid cutoff
Define contrast resolution
The ability to distinguish anatomic structures of similar subject contrast such as liver and spleen
The main components of film are:
base, adhesive, emulsion, supercoat
This is applied on the base layer before emulsion.
adhesive
Diagnostic radiographic film with emulsion on both sides is termed:
Duplitized,Double Emulsion, or Double Coated. Answer is all of the above
What is the correct order of the processing process:
Developer, Fixer, Washer, Dryer
High ratio grid improves
radiographic contrast
The higher the grid ratio
The higher the contrast improvement factor
Bucky factor increases with …… kvp
Increasing
The use of a compression device will increase
Contrast
Purpose of grid
To improve image contrast
Optical density is directly controled by the changing
mAs
The use of …….improves contrast and reduces patient dose
Collimation
Purpose of moving grid
to remove grid lines
High grid ratio increases……. and…………, and decreases………….
patient dose,grid cutoff, and positioning latitude
Destructive
radiolucent
Constructive
Radiopaque
Intensifying screen increases…………, decreases……….and………..
density, patient dose, and detail
How can you reduce motion blur?
short exposure time
The image after processing is known as
manifest image
What does grid cutoff mean?
The primary x rays are absorbed
Radiograpgic grid with ines running in two directions
Crossed
Whwn mA is increased what must be done to exposure time in order to maintain the same exposure?
decrease time
What is the purpose of the fixer in an automatic processor?
remove the unexposed silver halide crystals
When is xray film most sensitive to safelight illumination?
after exposure
Poor film-screen contact will cause which of the following effects?
Unsharpness
Which of the following could be the cause of poor film-screen contact?
warped cassette, worn backing in the cassette, and damaged latch on the cassette
Which grid removes more scatter radiation?
Crossed
Which of the following influences geometric unsharpness?
OID
Focal-Object Distance
SID
Distortion can be caused by
Tubes Angle
The Position of The organ or Structure Within The Body.
The Radio graphic Positioning of The Part.
The major function of filtration is to reduce
patient dose
Which of the following will influence recorded detail?
1) Screen Speed
2) Screen/Film Contract
3) Focal Spot
What will result from using single-emulsion film in an image receptor having a two intensifying screens?
Decreased Density
Boxes of film stored in too warm an area may be subject to
film fog
X-ray film emulsion is most sensitive to safelight fog
.
After Exposure.
The absorption of useful radiation by a grid is called
grid cutoff
The unwanted exposure of film by environment is called:
chemical fog
Primary cause for contamination is:
Other chemicals have mixed with the developer
The part of processing that is most affected by contamination is:
developer
This artifact is caused by static electricity and happens in low humidity:
trees
This occurs when screen phosphors continue to emit light after the x-ray exposure has stopped:
phosphorescence
………..% change in mAs is required for a perceptible change in OD.
30%
…………% change in kVp is required for a perceptible change in OD.
4%
…………..% increase in kVp will double the OD (15% rule)
15%
What is the formula for OD?
OD=log 10 Io/It
The base + fog of a film is shown below the _______ of characteristic curve
toe portion
