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7 Cards in this Set
- Front
- Back
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What is noise? |
Background data that does not contribute to the image |
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What is quantum mottle? |
nonuniformity in the x-ray beam. Rain on a sidewalk. |
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How does field size relate to noise? |
Increased collimation -> decreased field size -> increased noise (decreased number of photons hitting the detector). Compensate by increasing mAs. Decreased collimation > increased field size > decreased noise but increased scatter and dose.
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What dose a grid do to dose? |
Increases it. Higher grid ratio > higher mAs |
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To decrease noise, is it better to increase mAs or kVp? |
Increase mAs. An increase in kVp will decrease quantum mottle but increase compton scatter and therefore, increase noise. |
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What is "grid cut off"? What causes it? |
Grid cut off means you block too many photons and cause quantum mottle or a noisy image. Usually caused by improper grid positioning. If question stem alludes to grid cut off, choose repositioning before increasing mAs |
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How are noise and source-to-detector distance related? |
Inverse square law. |
