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30 Cards in this Set
- Front
- Back
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The extreme differences between blacks and whites of an image, appearing as a series of shadows of different densities (variations of grays)
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Contrast
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Shows very vew shades of grays
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Short scale contrast
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Shows many shades of grays
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Long scale contrast
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Low Contrast
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Long scale contrast
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many subtle shades of gray and occurs with higher kVp ranges
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Low Contrast
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High Contrast
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Short Scale Contrast
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Black and white and occurs with lower kVp ranges
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High Contrast
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Controls the primary differences in radiographic densities known as ....
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Contrast
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Effect of increase in kVp
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Increased penetrability, decreased contrast
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40 - 150 kVp in one or two increments.
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kVp diagnostic Range
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As the kVp increases, the xray wavelength becomes ..... Because kVp is the penetrating power, there must be enough penetration to move the xray beam through the object to carry the information across to the film.
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kVp Shorter, and more penetrating
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Whenever kVp is increased, more remnant radiation, as well as ......reaches the film.
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scattered radiation,
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.... contrast is recommended because it provides better visualization and the patient receives less radiation because of the use of ....
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Longer Scale (low) contrast, Lower mAs at higher kVp
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Factors that DO NOT affect Contrast
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mA
Time mAs SID Focal Spot |
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Factors that AFFECT Contrast
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kVp controls contrast (inversely proportional)
OID and contrast directly proportional (air gap) A grid with a high ratio reduces scatter A larger collimation field produces more scatter Increased filtration produces a beam with more energy, more scatter, less contrast |
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Formula to lengthen scale of contrast
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15% Rule
Increase kVp by 15% decrease mAs by 50 % |
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Formula to shorten scale of contrast
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15% Rule
Decrease kVp by 15% Increase mAs by 2X |
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Effect of scatter radiation on contrast
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scatter radiation places added density on the film causing lower contrast. (not good contrast) FOG
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The smaller the beam size the .... the contrast
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Higher the Contrast (Short Scale)
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Lowest kVp = .... contrast
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Greatest contrast (Short Scale)
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Highest Grid ratio = ... Contrast
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Greatest Contrast (Short Scale)
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Smallest area of collimation = .... contrast
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Greatest Contrast (Short Scale)
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The fastest film/screen speed combination = ... contrast
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Greatest Contrast (Short Scale)
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Film processing , the greater the total filtration ..
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the lower the contrast (Long Scale)
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SID
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NO EFFECT ON Contrast
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OID, The greater the object distance, the ..
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Higher the contrast (Short Scale) because of the "Air Gap" Technique
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The greater the tissue density and thickness, the more scatter radiation, therefore ..
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reduced contrast (Long Scale)
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The lower the atomic number of tissue irradiated the greater the scatter due to Compton effect
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reduced contrast (Long Scale)
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A compression device can be used to reduce tissue thickness, thereby
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increasing contrast (Short scale)
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Destructive Pathology tends to ..while additive pathology tends to ....
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destructive pathology increases contrast (short scale) /// additive pathology tends to decrease contrast (long scale)
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