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47 Cards in this Set
- Front
- Back
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What is the difference between adjacent densities called |
Contrast |
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Along with density this allows us to see subject detail |
Contrast |
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Once exposure is done contrast is finite film or digital |
Film |
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Many shades of gray available, applies to soft copy (monitor display), great range of density/brightness, windowing ( manipulation of brightness/density and therefore contrast), LUTs and there effect on contrast Film or digital |
Digital |
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The difference between adjacent densities |
Contrast |
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Any change in density (mAs, brightness) will have some effect on |
Contrast |
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Low contrast, many shades of gray, long scale, large window or dynamic range, seen more with ___ kVp |
High |
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High contrast, black to white, short scale, narrow window, seen more with __ kVp |
Low |
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Subtle shades of gray reveal |
More |
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Contrast within a department will be determined by |
Radiologist, equipment calibration |
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Digital response to exposure is __ and highly sensitive to exposure |
Linear |
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Processor fog __ contrast |
Decreases |
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Overdevelopment __ contrast |
Decreases |
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Developer contamination by fixer will __ fog |
Increase |
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Compton scatter __ with higher kVp |
Increases |
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Fog goes up, contrast goes |
Down |
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As kVp goes __, wider range of photon energies, more photons will penetrate, greater range of exposure, more uniform penetration, reduced contrast |
Up |
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As kVp goes __, less range of exposure, greater attenuation with thicker parts and higher atomic numbers, |
Down |
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Subject contrast is dependent on kVp selected and type/amount of irradiated tissue this is called |
Differential absorption |
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Uniform thickness, subject contrast goes __ |
Down |
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Variety of thickness subject contrast goes |
Up |
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Uniform tissue density subject contrast goes |
Down |
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Variety of tissue density subject contrast goes |
Up |
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Need a variety of __ __ in adjacent tissue to see contrast |
Atomic numbers |
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What must you have to see optimal contrast in an image |
Proper range of densities for that part |
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How do you enhance visibility when trying to read film |
Environment, turn off lights, turn off unused view boxes, focus on ROI, use contrast mask |
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What technique controls contrast |
kVp |
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KVp up contrast goes |
Down |
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When choosing kVp you need to look at |
Anatomy, pathology, contrast scale desired by rads |
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Optimal kV for each part will also be affected by |
Subject an imaging parameters |
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What affects both quantity and quality |
kV |
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Increasing this means more Compton and less photoelectric |
kV |
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mAs on film visibly affects |
Density |
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mAs on digital affects |
IR exposure and exposure number |
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Focal spot size does not affect |
Contrast |
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Anode heel effect means radiation intensity is more intense at the |
Cathode end |
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Air gap reduces __ so contrast __ |
Scatter, increases |
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An increase in filtration will increase average beam energy so contrast |
Decreases |
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Increase beam restriction (collimating) will decrease # of photons, so scatter __ and contrast __ |
Decreases, increases |
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As field size goes __, contrast goes __ and scatter __ |
Up, down, up |
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As tissue density goes __, contrast goes __, scatter goes __ |
Up, down, up |
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As atomic # goes __, contrast goes ___ |
Up, up because of photoelectric effect |
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Cleans up and absorbs scatter, contrast increases, higher ratio, greater contrast |
Grids |
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Increases contrast over direct exposure film radiography, don't know why |
Intensifying screens |
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Histograms alter |
Density |
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LUTs alter |
Contrast |
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Windowing alters |
Both |
