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42 Cards in this Set
- Front
- Back
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What is the relationship between recorded detail and OID?
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Inverse. As OID increases, recorded detail decreases.
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What increase is needed in SID to remedy 1 in of OID?
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7 inches SID for every 1 inch OID
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What is the relationship between SID and recorded detail?
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Direct. As SID increases, so does recorded detail.
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What is the relationship between recorded detail and magnification?
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Inverse. As magnification increases, recorded detail decreases.
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How are SID and magnification related?
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Inverse. As SID increases, magnification decreases.
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What does Detective Quantum Efficiency (DQE) refer to?
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Phosphors with high atomic numbers react to x-ray photons more efficiently and possess greater speed.
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What does Conversion Efficiency (CE) refer to?
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A particular phosphor's ability to absorb x-ray energy and convert it to fluorescent light energy.
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What rare earth phosphors are used in radiography?
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Oxysulfides and oxybromides
lanthanum gadolinium yttrium |
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What rare earth phosphors are used in fluoroscopy?
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Cesium iodide
zinc cadmium sulfide |
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What three factors determine screen speed?
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Phosphor size
phosphor layer thickness degree of reflectivity backing |
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angulation against the grid lead strips, with resulting loss of density across the image
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angulation error
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Grid cut off from x-ray tube and grid surface planes not being parallel
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off-level errors
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If the SID is below the lower limits, or above the upper limits, grid cut off occurs. Loss of density at the periphery of the image
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Off focus grid
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X-ray beam is not centered to the grid, grid cut off occurs with a uniform density loss
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off-center errors
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What is the radiolucent interspace material in grids most often made of?
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plastic or fiber, sometimes aluminum
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How does scatter effect density and contrast?
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Increases density
lowers contrast |
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What is tube filtration's effect on density?
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It has no effect on image density
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True or False:
Correction for generator type is unnecessary in digital imaging |
True
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What is the function of contrast?
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To make details visible
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What does the D log E (sensitometric) curve illustrate?
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Film contrast characteristics
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SF radiographic contrast is the sum of what?
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subject contrast and film contrast
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What is exposure latitude?
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The leeway, or margin of error, one has with a given group of exposure factors.
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True or False:
There is a larger "margin of error" in kV selection at higher kV ranges. |
True
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A mathematical expression of spatial resolution is...
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modulation transfer function (MTF)
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Pixel depth is directly related to what?
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Shades of gray, or dynamic range
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How is pixel depth measured?
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In bits. The greater the number of bits, the more shades of gray
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distance between pixels (impacts spatial resolution)
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Pixel pitch
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How is pixel pitch determined?
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scanning/sampling frequency
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How is pixel density measured?
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Pixels/mm
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What does pixel density express?
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sampling frequency
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the ____ the SNR, the ____ the contrast resolution.
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higher, better
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What is Detective Quantum Efficiency?
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DQE - ability of the receptor material to perceive and interact with x-ray photons
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What do PSP receptors in CR/DR use?
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Cesium iodide, barium fluorohalide, and amorphous selenium
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True or False: The DQE of SF intensifying screens is higher than the PSP receptors used in CR/DR.
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False. CR/DR has higher DQE
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What are the layers of a PSP storage plate?
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Protective coat
Phosphors in binder material reflective backing polyester base support material antistatic layer lead foil backing |
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PSP storage plates should be erased at least how often?
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Every 48 hours
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the CR scanner should be evaluated for "laser jitter" at least how often?
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monthly
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CCDs or TFTs are used in what type of digital imaging?
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Indirect capture DR
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CCD and TFT are types of what?
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photodetectors - "read" the light emitted from scintillators change photons to electrical signal
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Which indirect capture step is eliminated in direct capture?
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The scintillator
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True or False:
The spatial resolution in direct capture systems is fixed. |
true
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Spatial resolution in direct capture systems is related to _____
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Detector element (DEL) size of the TFT
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