Contrast Flashcards

1
Q
  • makes details visible
  • a psychovisual perception
  • the variation in density levels that makes detail visible
A

contrast

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2
Q
  • caused by attenuation and differential absorption
  • variation, changes or differentiation of adjacent densities on the radiograph
  • produced by photoelectric effect
A

contrast

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3
Q

its primary function is to make detail visible

A

contrast

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4
Q

differentiations between densities or details be readily made

A

satisfactory contrast

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5
Q

___ controls differential absorption of the x-ray beam by the body because of its control of x-ray beam energy

A

kVp controls differential absorption of the x-ray beam by the body because of its control of x-ray beam energy

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6
Q
  • inherent in the screen-film combination
  • influenced somewhat by processing of the film
A

image receptor contrast

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7
Q
  • affected by film (IR), film type & direct/IS exposure
  • affected by range of ODs and film processing technique
A

image receptor contrast

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8
Q

film-screen images have _______ contrasts than direct film exposure images

A

film-screen images have HIGHER contrasts than direct film exposure images

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9
Q

controlled by anatomy and pathology; affects contrast through variations of Z, tissue thickness, and tissue density

A

subject contrast

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10
Q

most important factor in controlling subject contrast

A

kVp

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11
Q

subject contrast
↓ kVp = _ contrast

A

subject contrast
↓ kVp = ↑ contrast

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12
Q

photoelectric effect varies in proportion to the cube of Z

A

effective atomic number

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13
Q

enhances contrast by enhancing photoelectric absorption

A

contrast media

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14
Q

objects that coincide with the x-ray beam have high subject contrast

A

object shape

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15
Q

caused by the shape of the structure

A

absorption blur

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16
Q
  • The difference in density/brightness between adjacent values are great.
  • The transition from white to black areas are fast and abrupt.
  • Can be achieve with the use of low kVp.
  • Is usually pleasing to the eye, but does not give better diagnostic value.
A

high contrast

17
Q

high contrast

↑ contrast = _ gray tones / short-scale contrast

A

high contrast
↑ contrast = ↓ gray tones / short-scale contrast

18
Q

low contrast

↓ contrast = _ gray tones / long-scale contrast

A

low contrast
↓ contrast = ↑ gray tones / long-scale contrast

19
Q
  • The differences in density/brightness between adjacent values are small
  • Transition from black to white areas are slow and there are many shades of gray that represent varying tissues in the body
  • Can be achieve with the use of high kVp.
A

low contrast

20
Q

means the range of optical densities from the lightest to the blackest part of the radiograph

A

scale of contrast

21
Q

there is great differences between available densities
high contrast
low kVp

A

short scale contrast

22
Q

there is little differences between available densities
many shades of gray
low contrast
high kVp

A

long scale contrast

23
Q

____ is the only factor that can control contrast of the radiograph

A

kVp is the only factor that can control contrast of the radiograph

24
Q

controls the differential absorption of the x-ray beam in the body

25
OID ↑ OID (15 to 25 cm) = air gap technique = _ scatter cleanup (equivalent to 8:1 grid ratio) = _ contrast
↑ OID (15 to 25 cm) = air gap technique = ↑ scatter cleanup (equivalent to 8:1 grid ratio) = ↑ contrast
26
air gap technique disadvantage _ magnification, _ SID, _ mAs to maintain density
air gap technique disadvantage ↑ magnification, ↑ SID,↑ mAs to maintain density
27
Grid ↓ scatter reaching the image receptor = _ scatter fog = _ gray tones = _ contrast
↓ scatter reaching the image receptor = ↓ scatter fog = ↓ gray tones = ↑ contrast
28
limits are being irradiated
beam restriction
29
beam restriction ↓ field size = _ number of Compton interactions = _ scatter = _ patent dose = _ gray tones = ↑ contrast
↓ field size = ↓ number of Compton interactions = ↓ scatter = ↓ patent dose = ↓ gray tones = ↑ contrast
30
as filtration is ↑, beam becomes ______ (average photon striking the patient has shorter wavelength)
as filtration is ↑, beam becomes HARDER (average photon striking the patient has shorter wavelength)
31
↑ filtration = harder photons = _ Compton scatter = _ contrast
↑ filtration = harder photons = ↑ Compton scatter = ↓ contrast
32
air-gap technique = _ contrast (owing to air filtration)
air-gap technique = ↓ contrast (owing to air filtration)
33
aka subject contrast
anatomy and pathology
34
cause differential absorption of x-ray photons, which results in contrast
anatomy and pathology
35
anatomy and pathology ↑ atomic number = _ contrast (owing to photoelectric effect) ↑ tissue density = _ contrast (owing to Compton scattering) ↑ tissue thickness = _ contrast (owing to Compton scattering) use of a contrast agent = _ contrast (owing to photoelectric effect)
↑ atomic number = ↑ contrast (owing to photoelectric effect) ↑ tissue density = ↓ contrast (owing to Compton scattering) ↑ tissue thickness = ↓ contrast (owing to Compton scattering) use of a contrast agent = ↑ contrast (owing to photoelectric effect)
36
↑ processing time = ↑ chemical fog = _ contrast
↑ processing time = ↑ chemical fog = ↓ contrast
37
↑ chemical temperature = ↑ chemical fog = _ contrast
↑ chemical temperature = ↑ chemical fog = ↓ contrast
38
In digital images, _______ can be enhanced through post-processing and is mostly affected by the pixel bit depth available in the system.
In digital images, CONTRAST can be enhanced through post-processing and is mostly affected by the pixel bit depth available in the system.
39
number of bits available for each pixel
pixel bit depth