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dig img quiz 1 set2
digital imaging quiz 1 set 2
Question | Answer |
---|---|
In the formula for brightness gain, brightness gain equals what? | minification gain X flux gain |
What is minification gain? | ratio of size of the input phosphor to the output phosphor |
In the minfication gain formula minification gain equals: | square of the diameter of the input phosphor / square of the diameter of the output phosphor |
In the conversion factor formula conversion factor equals: | output phosphor illumination (cd/m2) / input exposure rate ( mR/s) |
Magnification mode results in: | better spatial resolution, better contrast resolution, higher pt dose |
Explain the relationship between magnification and patient dose | increased magnification always increases pt dose |
ABC | automatic brightness control, automatic dose control or automatic brightness stabilization |
What is the purpose of the ABC? | to maintain image brightness by adjusting exposure factors for varying part thicknesses |
Explain the relationship between FOV and magnification | a smaller FOV produces greater magnification |
Explain the relationship between magnification and minification gain | increasing magnification decreases minification gain which decreases brightness gain |
What exposure factor is changed and how to maintain brightness when we change to a larger input phosphor? | mA is increased |
What is the mA range used in flouro? | .5-5mA (avg. 1-3 mA) |
What is vignetting | part of the image showing decreased brightness at the periphery |
What causes vignetting? | unfocused remnant radiation interacts with the periphery of the input phosphor |
What is the function of television monitoring? | to convert the light image into a video signal sent to the monitor |
What are the most popular types of television cameras? | vidicon and plumicon |
How is television monitoring set up? | the image intensifier is coupled directly to a television camera tube |
What is the difference between lens coupling and fiber optics? | fiber optics cannot accommodate aux devices, cannot take spots. |
How does lens coupling work? | with the use of a beam splitter light is divided between the TV camera and aux devices |
What is the function of the objective lens in the beam splitter? | accepts light from the output phosphor and converts it into 2 parallel beams |
Modulation | the size of the video signal is proportional to the light incident on the TV camera tube |
Raster pattern | movement of the e- beam |