Unit 2 (Recorded Detail & Distortion)

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nenyabrooke
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106546
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Unit 2 (Recorded Detail & Distortion)
Updated:
2011-12-03 20:29:45
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Imaging Principles
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Unit 2: Chapter 30 (Recorded Detail) and Chapter 31 (Distortion)
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  1. the shadow (blurriness) around the edges of the part being x-rayed
    penumbra
  2. what are the two geometric properties effecting the image?
    • distortion
    • recorded detail
  3. if you increase the SID will penumbra increase or decrease?
    decrease
  4. if you increase OID will the penumbra increase or decrease?
    increase
  5. if you increase the part thickness, will the penumbra increase or decrease?
    increase
  6. if the recorded detail is increase, has the penumbra increased or decreased?
    decreased
  7. misrepresentation of size and shape of the structures being examined
    distortion
  8. name three terms that are synonymous with recorded detail
    • sharpness
    • spatial resolution
    • detail
  9. do sharpness, spatial resolution, and detail have direct or indirect relationships with recorded detail?
    direct
  10. name three factors that determine spatial resolution
    • matrix size
    • pixel size
    • gray scale bit depth
  11. the number of the shades of gray offered
    gray scale bit depth
  12. what spatial resolution factor is on the Z axis?
    gray scale bit depth
  13. the whole field of view
    matrix
  14. what spatial resolution factor is on the Y axis?
    matrix
  15. what spatial resolution factor is on the X axis?
    pixel size
  16. if you decrease pixel size, will the resolution increase or decrease?
    increase
  17. if you increase the matrix, will the number of pixels increase or decrease?
    increase
  18. if you increase the matrix, will the pixels get smaller or larger?
    smaller
  19. if you decrease bit depth, do you increase or decrease resolution?
    decrease
  20. what unit is used to measure resolution?
    line pairs per millimeter (lp/mm)
  21. what instrument is used to measure resolution?
    • resolution test pattern tool
    • the more lines, the better the resolution
  22. name the six ways of accessing recorded detail
    • spatial resolution
    • spatial frequency
    • point spread function (PSF)
    • line spread function (LSF)
    • modulation transfer function (MTF)
    • noise
  23. the ability of an imaging system to accurately display objects in two dimensions
    spatial resolution
  24. if there is an increase in OID, you can compensate by:
    increasing SID (to reduce penumbra)
  25. name four ways to improve spatial resolution
    • increase matrix
    • decrease pixel size
    • increase number of pixels
    • increase bit depth
  26. how do you measure spatial frequency?
    by measuring distance between pairs of lines that are distinct from one another
  27. you have better resolution when you have a higher or lower frequency?
    higher
  28. PSF/LSF/ESF all have direct or indirect relationships with resolution?
    direct
  29. what is a digital term for penumbra?
    isotropic emission
  30. does MTF have a direct or indirect relationship to spatial frequency?
    indirect
  31. on the MTF scale, what represents the image close to perfect?
    1
  32. as you move closer to 0 and away from 1 on the MTF scale, do you gain or lose accuracy?
    lose
  33. if you have an increase in noise, has the resolution increased or decreased?
    decreased
  34. what is another name for noise?
    quantum mottle
  35. background information received by the image receptor
    noise
  36. what do you do to contrast and noise to get the best resolution?
    • increase contrast
    • decrease noise
  37. which offers the least amount of frequency?
    A. muscle
    B. bone
    C. adipose
    D. tendon
    B. bone
    (this multiple choice question has been scrambled)
  38. in digital sampling, what pattern is desirable?
    the nyquist pattern
  39. in digital sampling, which pattern is not desirable?
    the moire pattern
  40. if the nyquist pattern is met, will the resolution be higher or lower?
    higher
  41. if you eliminate motion, will the recorded detail increase or decrease?
    increase
  42. if you reduce OID, will the recorded detail increase or decrease?
    increase
  43. if you increase focal spot size, will recorded detail increase or decrease?
    decrease
  44. if you reduce intensifying screen phosphor size, will recorded detail increase or decrease?
    increase
  45. if you increase phosphor concentration, will you increase or decrease recorded detail?
    increase
  46. if you decrease SID, will you increase or decrease recorded detail?
    decrease
  47. what are the three types of motion?
    • involuntary
    • voluntary
    • equipment motion
  48. name two ways to minimize involuntary motion effects
    • reduce exposure time
    • immobilization
  49. if you reduce focal spot size, does the resolution increase or decrease?
    increase
  50. name two ways distance can affect resolution
    • OID
    • SID
  51. which of the following will cast the greatest amount of penumbra?
    A. sphere
    B. trapezoid
    C. cylinder
    C. cylinder
    (this multiple choice question has been scrambled)
  52. the true representation of the object
    umbra
  53. how do you calculate penumbra?
    • penumbra = (focal spot size X OID) divided by SOD
    • SOD=SID-OID
  54. if you increase phosphor layer thickness, will the resolution increase or decrease?
    decrease
  55. what controls quantum mottle?
    increasing mAs
  56. what is the major limitation of Indirect Digital System?
    • the size of the detector element
    • smaller size = better resolution
  57. what three factors affect the resolving power of intensifying screens?
    • phosphor size (decrease)
    • layer thickness (decrease)
    • concentration (increase)
  58. what are the two types of distortion?
    • size
    • shape
  59. size distortion is affected by:
    distance (OID and SID)
  60. shape distortion is affected by:
    • angulation
    • alignment
  61. if you decrease OID, will magnification distortion increase or decrease?
    decrease
  62. if you decrease SID, will magnification distortion increase or decrease?
    increase
  63. the size of a part at the image receptor will always be __________ than the actual size of the part.
    larger
  64. name two forms of alignment
    • tube perpendicular to the part
    • the part parallel to the receptor
  65. name two aspects of angulation
    • direction
    • degree
  66. if you increase SID, does size distortion increase or decrease?
    decrease
  67. if you increase OID, does size distortion increase or decrease?
    increase
  68. to calculate size distortion (magnification factor):
    M=SID/SOD
  69. to calculate object size:
    O=I/M
  70. always remember the object will always be ________ than the image
    smaller
  71. to calculate percentage of magnification:
    (Image minus Object) divided by Object, all multiplied by 100
  72. to minimize shape distortion, how should the central ray (CR) be aligned?
    perpendicular to the part and receptor
  73. to minimize shape distortion, how should the anatomical part be aligned?
    the part perpendicular to the CR, and parallel to the receptor
  74. to minimize shape distortion, how should the image receptor be aligned?
    parallel to the part, and perpendicular to the CR
  75. projects the object so it appears to be longer
    elongation
  76. projects the object so it appears to be shorter
    foreshortening
  77. how is elongation achieved?
    by angling the tube or the receptor
  78. how is foreshortening achieved?
    only achieved by angling of the part
  79. as the severity of the degree of angulation increases, does the shape distortion increase or decrease?
    increase
  80. as the severity of the direction of the angulation increases, does the shape distortion increase or decrease?
    increase
  81. name two examples of using misalignment to the radiographers advantage
    • positioning a patient prone to visualize intervertebral spaces
    • taking a left lateral chest to prevent heart magnification due to OID
  82. if patient thickness is increased, is size distortion increased or decreased?
    increased

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