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33 Cards in this Set
- Front
- Back
Radiographic density |
The degree of blackness on a radiograph.
Dark areas made p of black metallic silver on finished radiograph Can be increased by raising mA or exposure time or even kVp by increasing the penetrating power of the x-ray beam |
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Radiographic Contrast - What is it? Long scale vs short scale?
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Differences in radiographic density between adjacent areas on radiograph. |
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Subject density
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The ability of the different tissue densities to absorb x-rays. Penetrate depending on the differences in atomic number and thickness |
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Radiographic detail
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Sharp tissue and organ inteerfaces. Most common factors affecting detail are patient motion or penumbra effect |
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Penumbra Effect (Penumbra)
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Excessive penumbra causing blurring around edges or shadows cast by x-ray exposure. GREATEST ON CATHODE SIDE OF IMAGE BECAUSE THE EFFECTIVE FOCAL SPOT IS NOT CONSTANT ACROSS THE RADIORAPH (Larger at the cathode) |
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Quantum mottle
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Density variation caused by incomplete exposure of film. |
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x-ray production process
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-Thermionic emission (Boiling off of electrons from the filament on cathode side. As filament current increases the filament becomes hotter and more electrons are relased) |
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Milliamperage
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AKA Tube current - Measurement of the number of electrons traveling from cathode to anode during the exposure
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Time
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measurement of how long the x-rays are produced - the length of exposure |
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mAs calculations
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-mA x seconds = mAs |
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Factors affecting Radiographic/Optical Density (OD)
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-mAs |
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Kilovoltage
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AKA Object Density
Measure of the maximum electrical potential across an x-ray tube Controls penetrability (The thicker the part, the higher the kVp) |
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How does kVp affect the tube current?
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increase causes an acceleratin of electrons:
-Increases electron kinetic energgy -Increases photon energy -Increase acceleration (more peneratrability) -Increase in scatter radiation Higher kVp allows you to use less mAs, decreasing tube load and tube heat |
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How does kVp affect CONTRAST
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Contrast decreases with increased kVp because it increases x-ray energy,increases penetration, and increases scatter radiatin. |
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How does kVp affect density?
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Increases with increased kVp due to x-ray energy |
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How does kVp affect exposure latitude?
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High contrast (Black and white) - is narrow latitude, at lower kVp, an error of a few kVp can make a very noticeable diffference |
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Scatter radiation
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Produced when x-ray photons from the primary beam redirected after interaction in/on the patient or table. |
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The grid
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Device used to improve the contrast of the radiographic image by cleaning up scatter radiation before it reaches the image. |
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Air gap
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Has same effect as grid by controlling scatter because the scatter photon diverges beyond the borders of the film. Equivalent to a 5:1 grid |
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Completely clear image vs black image
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Completely clear = Wasn't exposed |
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Distortion
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Incorrect positioning; |
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Intensiffying screen construction
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Base - Plastic cardboard backingg and flexible |
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Screen speeds
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Slow (detail or fine) - high defenition, better detail |
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Large and small crystals
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Larger crystals - Faster but decrease detail
Smaller crystals = Slower but better detail |
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What is Film made up of?
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Made up of a polyester base, ligght sensitive emulsion (gelatin) on both sides, AND Silver Halide microcrystals imbedded in the gel (Silver bromide and silver iodine crystals) |
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Latent image
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The image of film before developing
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Screen types
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Blue senstive (ultraviolet) - Blue light emitting phosphors from the screen (Calcium tungstate and some rare-earth phosphors) |
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System speed
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Screen speed combined with film speed |
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Film speed
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higher the number the faster the film. |
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Developer solution
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Convert silver halide crystals into black metalic silver. Contains a solvent, reducing agent, restrainer an activator and a preservative
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Fixer solution
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Removes unchanged halide crystals leaving black metalic silver on the film along with hardeningg it to reduce scrates. Contains a fixer agent, solvent, hardener, acidifier, and preservative
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FFD
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Focal film distance = Increase of this increases detail, penumbra decreases, and an increase of it causes less distortion
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OFD
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Object film distance = Increase of this , detail is decreased, and penumbra is increased. If it's decreased, there is less distortion
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