Contrast Study Guide

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Author:
johndc3476
ID:
137579
Filename:
Contrast Study Guide
Updated:
2012-02-29 11:06:56
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johndan
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Kims Class RAD
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  1. How does KVP affect contrast and why?
    It decreases contrast because higher with higher KVP you have more scatter.

    The more scatter you have, the more you decrease contrast.

    Higher KVP = DECREASE contrast
  2. How does PT thickness/composition affect contrast?
    Having a thicker patient means you will need more kVp to get through the part. Hence you will have to increase kVp to get through it, and more kVp means more scatter.

    More scatter means you DECREASE contrast.

    Thicker patient/subject contrast = decreased contrast.

    Thicker patient = DECREASE contrast
  3. How does grids affect contrast?
    • Grids are used to prevent scatter from hitting the film.
    • More scatter results in a decrease in contrast so if grids are used then there will be less scatter and this results in an increase in contrast.

    Less scatter = INCREASED contrast

    Higher Grid Ratio = INCREASED contrast
  4. How does filtration affect contrast?
    Filtration in general works like kVp. They are used to increase OVERALL average energy of kVP. So if it's increasing kVp, it means you increase the amount of scatter happening, hence a decrease in contrast.

    More scatter = DECREASE in contrast.

    More filtration = DECREASE in contrast
  5. How does OID affect contrast?
    OID is similar to a grid where it angles scatter away from the IR resulting in less scatter.

    Less scatter means more contrast.

    Greater OID = INCREASE in contrast.
  6. How does collimation affect contrast?
    • When you collimate, you are exposing less body tissue.
    • If there is less body tissue, there will be less scatter.

    • Less scatter = Increase in contrast hence..
    • The more you collimate, the more you INCREASE contrast.
  7. How does film screen affect contrast?
    Faster film screen results in a steeper slope on the D log E curve.

    The steeper slope you have = increase in contrast

    Faster imaging systems in general result in increased contrast.
  8. How does processing affect contrast?
    An increase in temperature/time/concentration will result in a decrease in contrast.
  9. How does compression affect contrast?
    When you compress for example, in mammography, breast tissue, youre making it thinner hence you are going through less tissue.

    Less tissue = less scatter = increase in contrast

    More compresion = increased in contrast.
  10. How does masking affect contrast?
    Masking increases contrast.
  11. How does contrast media affect contrast?
    Contrats media increases contrast.
  12. What does neumonics stand for?
    S O F S F C M
    Stat Orders From Surgery Follow Cutting Mistakes
  13. What is STAT in the neumonics?
    SID
  14. What is ORDERS in the neumonics?
    Maginification OID
  15. What does FROM in the neumonics means?
    Film Speed
  16. What does SURGERY stand for in the neumonics?
    Screen Speed
  17. What does FOLLOW in the neumonics stand for?
    Focal Spot
  18. What does CUTTING stand for in the neumonics?
    Contact ( Filmscreen contact )
  19. What does mistakes stand for?
    Motion

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