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18 Cards in this Set
- Front
- Back
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lattitude
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range of exposures that an image can present with adequate quality
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wide lattitude
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can discriminate btwn wide range of exposures
can provide dx over wide range of exposures |
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what affects resolution
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size of focal spot
magnification detector resolution motion processing |
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what does MTF stand for
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modulation transfer fxn
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do you want a high or low signal to noise ratio
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high signal, low noise
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what does beam energy refer to
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the spread of mangitude of XR beam energy spectrum
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what does a high beam energy result in
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increased variation in absoprtion, decreased scatter
increased contrast |
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what does mAs refer tp
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tube current exposure time
reflects total photons forming an image |
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how does maS affect image
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increases dose to pt, decreases noise
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which has higher radiation to pt: PA or AP CXR
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AP, b/c the photons have to penetrate more soft tissue (ex breasts)
and breasts have a higher tissue weighting factor |
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does a bigger or small focal spot size improve resolution
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smaller
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drawback to small focal spot size
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decreased maximal tube output b/c of inability to handle heat
--> increased exposure time --> blur |
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how does collimation affect scatter
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decresaes scatter --> improved contrsat, less noise, lower dose
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does an anti scatter grid cause more or less attenuation of xr beam
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more
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how to get a high energy beam
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high kvp and high filtration
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how to get a low energy beam
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low kvp, low filtration
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effects of a low energy beam
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high variation in absorption
decreased scatter high contrast requires more photons to penetrate body part; photons are also more highly absorbed |
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high kvp -->
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lower dose
lower contrast |
