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Contrast is the second of the two major __________ properties.
photographic
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What is contrast?
differences in adjacent densities
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If you decrease the exposure range, does the contrast increase or decrease?
increase
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If you decrease dynamic range, does the contrast increase or decrease?
increase
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If you narrow the latitude, will the contrast increase or decrease?
increase
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Is there more or less contrast on a short scale when compared to a long scale?
more contrast
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Is contrast affected more by window level or window width?
window width
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What is the name of the device used to show "steps" of contrast?
a penetrometer
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If you increase the kVp, will the contrast increase or decrease?
decrease
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If you increase the kVp, will the dynamic range increase or decrease?
increase
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What is the analog equivalent for dynamic range?
exposure range
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If you increase the kVp, will the scale be longer or shorter?
long scale
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If you decrease the kVp, will there be more or less photoelectric absorption?
more
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If you increase the kVp, will there be more or less scatter?
more
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When does compression or expansion occur?
after the image is taken, on the computer/monitor
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Does compression increase or decrease the contrast?
increase
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Does expansion increase or decrease the contrast?
decrease
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What three ways can you utilize to achieve compression/expansion?
- change the D log E curve
- adjust the kVp
- adjust the window width
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If you decrease window width, does it result in compression or expansion?
compression
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What entity makes up the y-axis of the D log E curve?
density
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For the D log E curve, the steps in the contrast scale are measured in increments of _________.
.3 (log exposure)
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What is the purpose of the D log E curve?
It is used to plot the differences of contrast in each "step"
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if you decrease the window width, is the contrast higher or lower?
higher contrast
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On the D log E curve, does a curve that is more vertical signify high contrast or low contrast?
high contrast
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On the D log E curve, does a curve that is more horizontal signify high contrast or low contrast?
low contrast
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If there is too much density, will the log exposure fall on the shoulder or the toe of the D log E curve?
the shoulder
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Which film offers higher contrast?
Film A
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What are the two types of image contrast?
- Image receptor contrast
- Subject contrast
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Describe contrast's proportional relationship with density.
If density becomes too high OR too low, the contrast decreases.
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What is image receptor contrast?
the range of densities the film is able to record
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What are 4 factors that affect image receptor contrast?
- Intensifying Screens
- Film Density
- D log E Curve
- Film Processing
- Digital Image Receptors*** (digital, not analog)
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What are 3 factors that affect subject contrast?
- Kilovoltage
- Amount of Irradiated Material
- Type of Irradiated Material
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Which has lower contrast, directly exposed film or screen film?
directly exposed film
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Which film was exposed with a screen, and which film was exposed without a screen?
- A: with screen
- B: without screen (ex. exposed with just cardboard)
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Which of these films displays high contrast?
Film A
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Would a low contrast film present as a vertical curve or a horizontal curve on the D log E Curve?
Horizontal
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If there is not enough density on a film, would the curve it presents for the D log E curve fall on the shoulder or on the toe?
Toe
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What has happened to curve A in this D log E curve representation?
The A curve has an increase of "base density" most likely due to a processing error.
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What is subject contrast?
range of variations in intensity after attenuation of the beam
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Using _____________ means that you are using a wider range of photon energy.
higher kVp
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Using higher kVp offers greater ___________, ________, __________, and a _________ scale of contrast.
- penetrability
- range of exposures
- amounts of scatter
- longer
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What does the amount of Irradiated Material depend on?
- the thickness of the part
- field size
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If there is an increase in the thickness of the part being x-rayed, does the amount of scatter increase or decrease?
increase
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If there is a decrease in field size, does the scale of contrast get longer or shorter?
short scale
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If there is an increase in thickness of the part and in field size, will there be an increase or decrease in contrast?
decrease
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What influences the type of Irradiated Material?
- The atomic number
- Tissue Density
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If there is a high atomic number and tissue density, will there be greater or lesser attenuation?
greater
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What is attenuation?
absorption of the x-ray as it passes through matter
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If there is small difference in atomic number and tissue density as compared to adjacent tissues, will there be high contrast or low contrast?
low contrast
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What is a tool we use to improve visualization when evaluating an area of a film?
a contrast mask
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Is Kilovoltage inversely or directly related to contrast?
inversely (a.k.a. indirectly)
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Extreme overexposure, where you reach the top of the D log E Curve and beyond is called _________. What happens to the image on the film when this occurs?
Dmax This causes the areas of higher density to look lighter and the areas of lower density to look darker, the opposite of what they should (negative image)
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If the focal spot size gets smaller, does the contrast increase or decrease?
neither, it remains the same
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What controls the focal spot size?
mA
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What is the focal spot size
the area on the anode where the x-ray photons are produced
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How does the anode heel effect affect contrast?
It doesn't. (it affects density...it's "hotter" on the cathode side)
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Does the Air Gap technique increase or decrease scatter?
decrease
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Does the Air Gap technique increase or decrease contrast?
increase
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Does the Air Gap technique increase or decrease patient exposure?
increase
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Does increased filtration increase or decrease contrast?
decrease
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Does increased filtration increase or decrease the average beam energy?
Increase
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Does increased filtration increase or decrease intensity?
decrease
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Does beam restriction increase or scatter?
decrease
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Does beam restriction increase or decrease contrast?
increase
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Does the left film or the right film display more contrast?
the one on the right (it has too much contrast)
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There is a pathology present in one of these films. What is it, and which film shows it?
The film on the right is too dense, indicating that emphysema is likely.
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Which projection is showing more contrast? Which one has more scatter?
- The hand is higher contrast
- The abdomen has more scatter
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Does increasing the Grid Ratio increase or decrease contrast?
increase
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