Unit 1 (Contrast)

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nenyabrooke
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99397
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Unit 1 (Contrast)
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2011-12-03 20:23:18
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Imaging Principles
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Chapter 29: Contrast for Unit 1 in Imaging Principles
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  1. Contrast is the second of the two major __________ properties.
    photographic
  2. What is contrast?
    differences in adjacent densities
  3. If you decrease the exposure range, does the contrast increase or decrease?
    increase
  4. If you decrease dynamic range, does the contrast increase or decrease?
    increase
  5. If you narrow the latitude, will the contrast increase or decrease?
    increase
  6. Is there more or less contrast on a short scale when compared to a long scale?
    more contrast
  7. Is contrast affected more by window level or window width?
    window width
  8. What is the name of the device used to show "steps" of contrast?
    a penetrometer
  9. If you increase the kVp, will the contrast increase or decrease?
    decrease
  10. If you increase the kVp, will the dynamic range increase or decrease?
    increase
  11. What is the analog equivalent for dynamic range?
    exposure range
  12. If you increase the kVp, will the scale be longer or shorter?
    long scale
  13. If you decrease the kVp, will there be more or less photoelectric absorption?
    more
  14. If you increase the kVp, will there be more or less scatter?
    more
  15. When does compression or expansion occur?
    after the image is taken, on the computer/monitor
  16. Does compression increase or decrease the contrast?
    increase
  17. Does expansion increase or decrease the contrast?
    decrease
  18. What three ways can you utilize to achieve compression/expansion?
    • change the D log E curve
    • adjust the kVp
    • adjust the window width
  19. If you decrease window width, does it result in compression or expansion?
    compression
  20. What entity makes up the y-axis of the D log E curve?
    density
  21. For the D log E curve, the steps in the contrast scale are measured in increments of _________.
    .3 (log exposure)
  22. What is the purpose of the D log E curve?
    It is used to plot the differences of contrast in each "step"
  23. if you decrease the window width, is the contrast higher or lower?
    higher contrast
  24. On the D log E curve, does a curve that is more vertical signify high contrast or low contrast?
    high contrast
  25. On the D log E curve, does a curve that is more horizontal signify high contrast or low contrast?
    low contrast
  26. 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

  27. Which film offers higher contrast?
    Film A
  28. What are the two types of image contrast?
    • Image receptor contrast
    • Subject contrast
  29. Describe contrast's proportional relationship with density.
    If density becomes too high OR too low, the contrast decreases.
  30. What is image receptor contrast?
    the range of densities the film is able to record
  31. 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)
  32. What are 3 factors that affect subject contrast?
    • Kilovoltage
    • Amount of Irradiated Material
    • Type of Irradiated Material
  33. Which has lower contrast, directly exposed film or screen film?
    directly exposed film
  34. 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)
  35. Which of these films displays high contrast?
    Film A
  36. Would a low contrast film present as a vertical curve or a horizontal curve on the D log E Curve?
    Horizontal
  37. 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
  38. 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.
  39. What is subject contrast?
    range of variations in intensity after attenuation of the beam
  40. Using _____________ means that you are using a wider range of photon energy.
    higher kVp
  41. Using higher kVp offers greater ___________, ________, __________, and a _________ scale of contrast.
    • penetrability
    • range of exposures
    • amounts of scatter
    • longer
  42. What does the amount of Irradiated Material depend on?
    • the thickness of the part
    • field size
  43. If there is an increase in the thickness of the part being x-rayed, does the amount of scatter increase or decrease?
    increase
  44. If there is a decrease in field size, does the scale of contrast get longer or shorter?
    short scale
  45. If there is an increase in thickness of the part and in field size, will there be an increase or decrease in contrast?
    decrease
  46. What influences the type of Irradiated Material?
    • The atomic number
    • Tissue Density
  47. If there is a high atomic number and tissue density, will there be greater or lesser attenuation?
    greater
  48. What is attenuation?
    absorption of the x-ray as it passes through matter
  49. 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
  50. What is a tool we use to improve visualization when evaluating an area of a film?
    a contrast mask
  51. Is Kilovoltage inversely or directly related to contrast?
    inversely (a.k.a. indirectly)
  52. 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)
  53. If the focal spot size gets smaller, does the contrast increase or decrease?
    neither, it remains the same
  54. What controls the focal spot size?
    mA
  55. What is the focal spot size
    the area on the anode where the x-ray photons are produced
  56. How does the anode heel effect affect contrast?
    It doesn't. (it affects density...it's "hotter" on the cathode side)
  57. Does the Air Gap technique increase or decrease scatter?
    decrease
  58. Does the Air Gap technique increase or decrease contrast?
    increase
  59. Does the Air Gap technique increase or decrease patient exposure?
    increase
  60. Does increased filtration increase or decrease contrast?
    decrease
  61. Does increased filtration increase or decrease the average beam energy?
    Increase
  62. Does increased filtration increase or decrease intensity?
    decrease
  63. Does beam restriction increase or scatter?
    decrease
  64. Does beam restriction increase or decrease contrast?
    increase
  65. Does the left film or the right film display more contrast?
    the one on the right (it has too much contrast)
  66. 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.

  67. Which projection is showing more contrast? Which one has more scatter?
    • The hand is higher contrast
    • The abdomen has more scatter
  68. Does increasing the Grid Ratio increase or decrease contrast?
    increase

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