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Glossary of Radiographic exposure test 1

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Recorded detail
the sharpness of the structural lines as recorded in the radiographic image
Density
the degree of blackening or opacity of an area in a radiograph due to the accumulation of black metallic silver following exposure and processing of a film
Contrast
the visible differences between any two selected areas of density levels within the radiographic image
Scale of contrast
refers to the number of densities visible (or the number of shades of gray)
Short scale contrast
considerable or major differences between densities are present (high contrast) but the total number of densities is reduced
Long scale contrast
slight differences between densities are present (low contrast) but the total number of densities is increased
Film latitude
the inherent ability of the film to record a long range of density levels on the radiograph
Film contrast
the inherent ability of the film emulsion to react to radiation and record a range of densities
Exposure latitude
the range of exposure factors which will produce a diagnostic radiograph
What controls exposure latitude?
kVp
High kVp->______ exposure latitude
Wide
Low kVp->_____ exposure latitude
Narrow
Subject contrast
the difference in the quantity of radiation transmitted by a particular part as a result of the different absorption characteristics of the tissues and structures making up that part
2 parts of radiographic quality
Visibility of detail (photographic properties) and recognizability of detail (sharpness of detail; geometric properties)
3 parts of visibility of detail
Density, contrast, noise
3 parts of recognizability of detail
Recorded detail, shape distortion (true distortion), size distortion (magnification)
Scatter fog and artifacts are types of image _____
noise
2 types of motion
Voluntary and involuntary
How do you reduce visibility of involuntary motion on an image?
Using short exposure time (1/30th of a sec or less) and immobilization devices
How do you reduce visibility of voluntary motion on an image?
Good patient instructions mainly; also immobilization devices
Does motion affect magnification?
No
Does motion affect shape distortion?
No
Does motion affect recorded detail?
Yes; reduces recorded detail
Does motion affect contrast?
Yes; reduces contrast when it causes densities to overlap. Motion is the only variable that affects contrast without doing so through scatter. Involuntary motion is usually not enough to affect overall image contrast
Does motion affect density?
It is not a primary controller of density. At certain points in the image, motion can affect density; but overall the image density remains relatively unchanged
Does motion affect noise?
Yes; increases noise by creating false images
the quantity of electrical current flowing through a circuit; is a rate
mA
What controls intensity of e- flow rate through the filament circuit?
mA
mA is _______ proportional to beam intensity
directly
amount of time in which beam is activated and exposure occurs
Exposure time (s)
intensity of total exposure
mAs
What controls radiographic density?
mAs
mAs (total exposure) is _______ proportional to density
directly
As long as the final product (mAs) remains the same, you can change the mA and time
Law of reciprocity
If density changes, does it affect recorded detail or just visibility of recorded detail?
Visibility of recorded detail. There are only 2 causes of blur: motion and geometrical penumbra
Will an image recorded with well-defined, sharp details automatically ensure that you will produce a film that is of radiographic quality?
No. Both photographic and geometric properties must be adequate in order to have a quality image.
Can you alter visibility without changing recorded detail?
Yes
What can motion affect?
Density, contrast, noise, recorded detail
Will an image possessing a proper balance of the photographic properties of density and contrast automatically ensure that you will produce a film that is of radiographic quality?
No. For an image to be of high quality, density and contrast must be adequate and balanced. However, the image should also have minimal noise, blur, magnification, and shape distortion.
Can motion affect both geometric and photographic properties?
Yes
How would you describe the relationship between mA and time of exposure as it relates to mAs and radiographic density?
Law of reciprocity: It is possible to vary the values for mA and exposure time and still end up with the same mAs and a similar radiographic density
100 mA x ____ = 1.6 mAs
0.016 s
50 mA x ___ = 1.6 mAs
0.032 s
200 mA x ___ = 1.6 mAs
0.008 s
25 mA x ___ = 1.6 mAs
0.064 s
Why might density vary between images produced using the law of reciprocity?
The law of reciprocity is not completely valid when you use very short exposures with a high mA or very long exposures with a low mA in screen radiography (when intensifying screens are used). Also, the machine may not be properly calibrated.
When might the law of reciprocity be useful?
When a longer exposure time is required (ex. breathing technique to blur anatomy) or a short exposure time is desired (ex. reducing involuntary motion)
What are some negative effects that can occur when using the law of reciprocity?
High mA can cause anode pitting/cracking. High mA can also require a larger FS, which reduces recorded detail. Also, density may vary due to use of intensifying screens or uncalibrated machines.
Of what significance is the calibration of your x-ray generator output to the maintenance of radiographic density and to an overall program of quality assurance?
Generator output must be calibrated so it is consistent. If it is not consistent, density and quality of radiographs produced may vary. Linearity and reproducibility is desired.
the proportionate accuracy of the output of one mA station in relation to another mA station
Linearity
the consistency in which a given mA station emits the set output from one exposure to the next
Reproducibility
In overexposed images, ___ dense tissues are less visible
less
In underexposed images, ____ dense tissues are less visible
more
If radiographic density is insufficient or excessive, the visibility of the recorded image will be ________ and the radiographic quality will be ___________.
reduced; reduced
SID inc->Field size ____
inc
SID inc->Intensity ___
dec
Inverse square law formula
(Original density/New density) = (New SID squared/Old SID squared)
If the area of an image produced at 20" SID is 4 square inches, what is the area of an image produced at 40" SID?
16 square inches
When you double SID, intensity and field size changes by a factor of __
4
As SID increases, the beam diverges _____ and interacts with a ______ area of film
more; greater
Decreasing SID by 1/2 decreases field size to ____ its original size
1/4
Density of an 80" SID exposure would be ___ the density of a 20" SID exposure
1/16
Density of an 80" SID exposure would be __ the density of a 40" SID exposure
1/4
SID inc->Radiographic density ___
dec
SID dec->Radiographic density ___
inc
What principle is in effect in the following example: The density of a 20" SID image is 4x the density of a 40" SID image.
Inverse square law
Less than __% of the x-rays striking an x-ray film are absorbed by the emulsion to expose it.
1
Intensifying screens ______ the effect of x-radiation on the emulsion by means of __________, thereby reducing the exposure.
increase; fluorescence
the ability to absorb x-rays and instantaneously emit light
Fluorescence
Fluorescent materials absorb radiation of various wavelengths and then transform and emit it so a(n) _____ in wavelength and a(n) ______ in energy occurs
increase; decrease
______ image is contained in film emulsion and revealed by processing
Actual
invisible image after exposure and before processing
Latent image
image you can see after latent image is processed; radiograph you hang on viewbox
Manifest image
1st IR was a...
cardboard holder with a piece of film inside
Typical IR for film is a...
light-tight cassette
What is the front of a cassette made of?
A low-attenuating (radiolucent) material like carbon fiber
The back of the cassette is a...
lid that contains hinge(s) and latch to open cassette
What is on the inside back of the cassette (to prevent backscatter from fogging radiograph)?
Thin sheet of lead or copper foil
The lid inside the back of the cassette is _____ to apply pressure and act as a squeegee to ensure uniform film/screen contact.
curved
Where may intensifying screens be mounted in the cassette?
Inside front and back of cassette
If a cassette is fine-detail or slow-speed, where will the intensifying screen sometimes be mounted?
Only on 1 side, usually back/lid
Which screen gets more exposure, the front or back instensifying screen?
Back
To compensate for the reduced exposure received by the back intensifying screen, some manufacturers make the back screen ____ and thus ___ than the front. However, some just make the 2 screens ______.
thicker; faster; identical
What is used for film identification?
Blocker (flasher flashes info onto film)
What is a compression pad also called?
Pressure pad; supportive backing
Where is a compression pad located?
In the front an back of the cassette
2 purposes of a compression pad:
-Supplies surface to which you can attach an intensifying screen
-Compresses the intensifying screens to the film
Older compression pads were made of ____. New compression pads are ______.
felt; foam
What is an advantage of foam compression pads over felt compression pads?
Less debris
Which lasts longer generally, the cassette or the intensifying screen?
Cassette
Who invented intensifying screens?
Edison
Who was first to use intensifying screens?
Michael Pupin
4 layers of intensifying screens:
-Base
-Adhesive surface/reflective layer
-Phosphor layer
-Protective coat


What part of the intensifying screen interacts with the cassette?
Polyester base
What layer provides structural integrity and a foundation for all the other layers of the intensifying screen?
Polyester base
What layer binds the polyester base to the phosphor layer of the intensifying screen?
Adhesive surface/reflective layer
What can be found in the adhesive surface of the intensifying screen?
Reflective materials, which direct light back towards the film surface
Why do some brands of "fine" screens or "extremity cassettes" not have a reflective layer?
Light reflected from this layer has a longer distance to travel before reaching film, so it spreads and contributes to blur.
What is the most important part of the intensifying screen?
Phosphor layer
What is the active/functional layer of the intensifying screen?
Phosphor layer
Which layer of the intensifying screen is where x-rays are absorbed and converted to light?
Phosphor layer
Where does the majority of exposure to film come from?
Light from phosphor layer of intensifying screen
What % of exposure to film comes from light from phosphor layer of intensifying screen?
90-95
Intensifying screen is used->_____ technique is required
Less
What is the phosphor layer of the intensifying screen composed of?
Phosphor crystals suspended in a material (plastic binder solution)
What does the configuration of the phosphor crystals in the phosphor layer of the intensifying screen depend on?
Manufacturer
What is the outer layer of the intensifying screen?
Protective coat (T-coat; tough-coat) made of tough plastic
What does the protective coat of the intensifying screen do?
Seals phosphor layer and protects it from damage (from film sliding in and out of cassette; ex. static electricity artifacts) and moisture
The protective coat of the intensifying screen is ____ and ________ to light emitted by phosphor crystals.
clear; transparent
What determines how well the screen performs?
Phosphor layer efficiency
To be efficient, an intensifying screen must do these things in order:
-Absorb x-rays
-Convert energy from x-rays into visible light
-Emit the produced light out of the phosphor layer and toward the film

Screen ______ depends on screen efficiency.
speed
High speed screens can _____, ______, and _____ very well.
absorb; convert; emit
A higher speed screen requires ____ technique because it is ______ efficient.
less; more
Light output from a screen is affected by...
its thickness, phosphor density, average atomic number of the phosphor, inherent conversion efficiency of phosphor, addition of dyes, K-edge of phosphor, and kVp used
Intrinsic factors (inherent to a screen) include...
phosphor material, reflective layer, and dye
Phosphor layer is thicker->Absorption efficiency ___
inc
Phosphor layer is thicker->Emission efficiency ___
dec. However, thicker phosphor layers still emit much more light due to the great increase in absorption efficiency.
Size of crystal inc->Absorption efficiency ___
inc. However, this method is no longer used since large crystals increase mottle effects and decrease resolution of fine details.
Phosphor density inc (the phosphor crystals or the molecules in each phosphor crystal are more closely packed)->Absorption efficiency ___
inc
Clumping of phosphor crystals can cause...
structural mottle
Phosphors with high atomic number used->_____ e- density (increased concentration of e- within the space around the nucleus)->Absorption efficiency ___
Higher; inc
The type of chemical compound used for the phosphor affects _______ efficiency.
conversion
Edison determined ___________ was the most efficient chemical to use for intensifying screens.
calcium tungstate
Calcium tungstate was used for screens up to the 1970s. It had a __% conversion efficiency.
5
What chemical compounds are used for the phosphor today?
Rare earth elements
Which are more efficient, rare earth elements or calcium tungstate?
Rare earth elements
Rare earth elements have a __% conversion efficiency.
20
What are some of the rare earth elements used for the phosphor?
Yttrium, gadolinium, lanthanum, barium
Rare earth elements are ____x more efficient than calcium tungstate in converting x-ray energy into fluorescent light.
2-4
Rare earth elements can have atomic numbers lower than calcium tungstate, but they are faster/more efficient due to...
K-edge effect, higher phosphor density, and higher inherent conversion efficiency
The 2 most commonly used compounds for the phosphor today are...
lanthanum oxibromide or gadolinium oxisulfide
Configuration of rare earth molecules allows for phosphor molecules to be more tightly packed->Phosphor density ___->Absorption efficiency ___
inc; inc
If atomic number is too high, so K-edge binding energy is well above the average x-ray beam energies, then absorption due to the photoelectric effect may be ____
lost
Rare earth elements have _____ binding energies in K-shell compared to calcium tungstate
lower
Is the photoelectric effect more likely with calcium tungstate or rare earth elements?
Rare earth elements
Do calcium tungstate or rare earth elements have a higher conversion efficiency?
Rare earth elements
Color dyes are added to what layer of the intensifying screen?
Phosphor layer
Color dyes in the phosphor layer of the intensifying screen absorb light photons that are...
not directed straight toward the film
Color dyes in the phosphor layer let light rays that are __________ pass through and absorb light rays __________
coming straight to the film; going out to the side
Does dye in the intensifying screen increase or decrease recorded detail?
Dye increases recorded detail because it prevents excessively diverging rays from reaching the film
What is the benefit of adding dye to the phosphor layer of the intensifying screen?
Improved recorded detail
What is negative about adding dye to the phosphor layer of the intensifying screen?
Dye reduces the amount of light reaching the film, so you have to increase exposure to make up for the dye
Amount of dye inc->Screen speed ____
dec (slower speed screen)
If screens are slow speed, do you increase or decrease technical factors?
Increase
What type of cassettes had slow speed screens?
Detail or extremity cassettes
Dye in the intensifying screen affects only ______ efficiency.
emission
What layer of the intensifying screen directs light back toward the film?
Reflective layer
What are some extrinsic factors of the intensifying screen?
Temperature, kVp dependency, age
Temp inc->Volume of phosphor layer ___->Chance of x-ray beam interacting with a phosphor ____->Absorption efficiency ____->Screen speed ____
inc; dec; dec; dec
When a fluorescent screen emits light, the chemical (phosphor) itself emits a characteristic __________ of light.
wavelength
A specific chemical (phosphor) will always emit the same _____ light with the same wavelength and energy.
color
kVp inc->X-ray energy ___->Amount of light photons emitted by phosphor ____; energy of light photons emitted by phosphor ____
inc; inc; stays the same
A screen always emits the same ______ of light regardless of the energy of the incoming x-ray photon. So output of screen is ____-dependent
energy; kVp
kVp inc->Absorption efficiency ___ and conversion efficiency ___
dec; inc
As screen ____, it begins to deteriorate and discolor.
ages
What types of screen efficiency decrease as the screen ages?
Conversion and emission efficiency
Anything that increases exposure rate (mA and kVp) to a screen will increase the _______ emitted by that screen
light
Only characteristics that are ________ to a screen affect screen speed.
inherent
Higher screen speed->Light output ___
inc
200 speed screen will emit __x as much light as 100 speed screen
2
Do screens using calcium tungstate or rare earth elements have a higher screen speed?
Rare earth elements
Film is sensitive to react to a specific ______ emitted by the phosphor.
color light
Do low-speed screens or high-speed screens result in a lower patient dose?
High-speed screens
(Even though Allen said only characteristics that are inherent to a screen affect screen speed), later he said factors affecting screen speed include both ____ and _____ factors
intrinsic; extrinsic
Reflective layer efficiency inc->Screen speed ___
inc
Phosphor thickness inc->Screen speed ___
inc
Crystal size inc->Screen speed ___
inc
Dye added->Screen speed ___
dec
Absorption efficiency inc->Screen speed ___
inc
Conversion efficiency inc->Screen speed ___
inc
Temp inc->Screen speed ___
dec
kVp inc->Screen speed ___
inc
Age inc->Screen speed ___
dec
Higher screen speed->Density produced at a given exposure ___
inc
Higher screen speed->Patient dose ___
dec since lower exposure settings will produce adequate density
Speed of a screen is derived from the...
intensification factor
factor by which exposure can be reduced to obtain a similar density when using a screen
Intensification factor
Intensification factor formula
(Exposure without screen)/(Exposure with screen)
An exposure requiring 300 mAs was used to obtain a density of 2.0 without a screen. Using a screen, the exposure only required 10 mAs to obtain the same density. What is the intensification factor?
30. Screen is 30x faster than no screen
Slow/detail/extremity screens/cassettes have speeds of...
50-80
Medium/par-speed screens have a speed of...
100 (100 speed screen is the standard)
Fast/rare-earth speed screens have speeds of...
200, 400, 800, and maybe 1200
Very high speed screens are rarely used for 2 reasons:
-Thick phosphor layer results in loss of image sharpness
-Quantum mottle occurs due to grossly reduced mAs values used
Very high speed screens may lead to ____ mottle and _________/________ mottle in the image
quantum; material/receptor
Screen speed dec->Technique required ___
inc
You want to obtain the same density that you would obtain using 10 mAs with a 400 speed screen. What mAs would you use for a par speed screen?
40 mAs
Screen speed inc->Contrast ___
inc generally
Is the film emulsion more responsive to light or radiation?
Light
Screen acts as a _______ and absorbs some of the scatter from patient
filter
Screen used->Scatter reaching film ___->Contrast ___
dec; inc
Use of screens always results in _______ recorded detail
decreased
Why does the use of intensifying screens always result in decreased recorded detail?
Light has to travel farther to the film
Screen speed inc->Recorded detail ___
dec
If film/screen contact is not close, recorded detail will be ____
lost
Protective coat thickness inc->Recorded detail ___
dec
Phosphor layer thickness inc->Recorded detail ___
dec
Dye added->Recorded detail ___
inc
Dye added->More light is _______->Screen is ____ efficient (_____ speed)->_____ technique is required
absorbed; less; slower; greater
ability to emit radiation of one quality when stimulated by radiation of another quality
Fluorescence
When the light output from a screen exceeds 10^-8 sec, it is said to be...
phosphorescent
________ materials keep giving off light after exciting radiation is cut off.
Phosphorescent
Aged, poor-quality screens become ________ and develop _______.
phosphorescent; screen lag
When glow of light continues after x-rays are turned off, it is called...
screen lag/afterglow
Do intensifying screens have an effect on magnification?
No
Do intensifying screens have any effect on shape distortion?
No

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