Distortion

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Author:
johndc3476
ID:
144863
Filename:
Distortion
Updated:
2012-03-31 10:54:13
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johndc3476
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  1. What are some factors of distortion?
    • Tube angle
    • Bone fractures
    • Position of Patient.
    • Position of the casette
  2. How do you
    assess distortion?
    Distortion is a geometric property that affects quality of the radiographic image.
  3. What are the two types
    of distortion?
    • Elongation
    • Foreshortening
  4. When density or
    contrast is poor, can you see distortion?
    No. But it still it exists nonetheless.
  5. How can you minimize
    distortion? ( 5 factors )
    The distance, direction and angulation of tube, anatomical part, central ray and image receptor.
  6. What is size distortion?
    It is and can ONLY be maginification
  7. Why is minimification impossible?
    Because of the divergent property of x-ray .
  8. When size distortion(magnification) is reduced, what happens to detail?
    Detail is increased.
  9. Does OFD have a direct or indirect relationship with magnification?
    OFD has a direct relationship with magnification.
  10. When OFD increases, what happens to magnification?
    Whne OFD increases, magnification increases
  11. OFD is a critical distance in what 2 factors?
    Magnification and resolution
  12. How does SID affect magnification?
    Greater SID = smaller magnification.
  13. Does SID have a direct, indirect or inverse relationship with magnification?
    SID has an inverse relatinship wtih magnfication
  14. Why does SID cause less magnification?
    When SID is increased, you get straighter photons for the body part.
  15. What is the equation to calculate magnification?
    Magnification = SID / (SID - OFD)
  16. What is the ideal thing to do to get the best image?
    Object being x-rayred is parallel to the film and central ray is perpendicular to the object and film
  17. What is foreshortening?
    Foreshortening occours when the object is at an angle and the CR is perpendicualr to the film ( it will appear shorter/squashed together)
  18. What is elongation?
    Type ofdistortion that occurs whne object is parallel to the film and central ray is angled.
  19. How do you avoid shape distortion?
    Alignment of the central ray with anatomical part as well as proper positioning
  20. Any structure not positioned at the CR will be distorted because....
    of the divergence of the beam, the farther from the CR the greater the distortion.
  21. What is spatial distortion?
    When CR is at an angle but the object and filmare parallel to each other.
  22. In spatial distortion, 3d relationship between several body parts are...
    Distorted on the image by different elognations of each body aprt.
  23. What causes elongation?
    Angle of the tube.

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