chapter 15 fluoro
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each of the black spaces below before clicking
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| mA for fluoroscopy | 0.5-5 mA
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| length and diameter of image intensifier tube | 50cm long, 15-58cm diameter
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| 5 parts of image intensifier | 1. input phosphor
2. photocathode
3. focusing lenses
4. accelerating anode
5. output phosphor
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| material of input phosphor | cesium iodide
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| material of output phosphor | silver-activated zinc cadmium sulfide
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| brightness gain | expression of ability of image intensifier tube to increase image brightness
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| flux gain | ratio of number of light photons at output phosphor to number of light photons emitted in input phosphor + represents tube's conversion efficiency
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| conversion factor | expression of luminance at output phosphor divided by input exposure rate
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| Automatic Brightness Control (ABC) | function of fluoro unit adjusting kVp, mA, or both
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| magnification mode | increases voltage to electrostatic focusing lenses
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| in magnification mode, the focal point is shifted _______ from output phosphor | farther
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| trifocus image intensifier ________________ can be operated in any of these 3 modes | 30/23/15
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| distortion: | misrepresentation of true size or shape of object
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| 2 types of distortion from fluoro: | unequal magnification (pincushion) and loss of brightness around periphery (vignetting)
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| image noise: | results when insufficient info is present to create image (not enough xrays expose input phosphor)
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| image noise is fixed by ______ __ | increasing mA
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| 2 tv cameras: | camera tube and Charge-Coupled Device (CCD)
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| image intensifier can resolve ______lp/mm | 5
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| monitor can resolve ___to___lp/mm | 1 to 2
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| cassette spot filming | static imaging process using radiographic cassette to obtain an image
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| Flat-Panel Detectors are used in ________ fluoroscopy | digital
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| Flat-panel detectors: | cesium iodide amorphous silicon indirect capture detector
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| Application-Specific Integrated Circuits (ASIC): | minimize noise, maximize readout speed, allow switching from low to high dose
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| Backlighting: | erase detector between frames, preventing ghosting
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| advantages of flat panel detectors in place of image intensifiers: | reduce bulk+weight
don't degrade w/age
more durable
less artifacts
reduce dose 50%
better contrast resolution
postprocessing options
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| fluoro features: | Last Image Hold (LIH) for virtual collimation
frame averaging, reducing pt dose
option to include grid
selection of added filtration
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| frame averaging __________spatial resolution | decreases
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Created by:
JuliaW2003