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img crit contrast 2

image critique - contrast 2

QuestionAnswer
Contrast the difference between adjacent densities
Dynamic range contrast as displayed on the monitor, the number of shades of gray which a pixel can display.
Window width digital processing that controls changes in contrast
A high contrast x-ray exhibits ____ shades of gray? few shades of gray
A high contrast x-ray exhibits ____ scale? short scale
A high contrast x-ray exhibits ____ dynamic range? short dynamic range
A high contrast x-ray exhibits ____ window width? narrow window width
A low contrast x-ray exhibits ____ shades of gray? many shades of gray
A low contrast x-ray exhibits ____ scale? long scale
A low contrast x-ray exhibits ____ dynamic range? large dynamic range
A low contrast x-ray exhibits ____ window width? wide window width
Low contrast is associated with what kind of kVp? high kVp
Low kVp yields what kind of contrast? high
Alternate names for the D log E curve H and D curve, Characteristic curve.
On the H and D curve, a more vertical slope demonstrates what? short scale or high contrast
What minimum kVp change is needed for a noticeable change in contrast? 4kVp
How do IS affect contrast? they increase contrast or shorten the scale.
How does screen speed affect contrast? it has a negligible effect
What is the range for desired density? .25 – 2.5
The shoulder of the H and D curve demonstrates what? overexposure
The toe of the H and D curve demonstrates what? underexposure
what does fog do to the toe of the H and D curve? it raises it, decreases contrast
What does fog do to contrast? it decreases it
What is created when a higher kVp is used? longer scale of contrast, greater amount of scatter, greater range of exposures, greater penetrability.
When an image is repeated to improve contrast, how should the kVp be changed? 8-15% increments or by 5-10 kVp
How are kVp and contrast related? inversely
How does FSS affect contrast? it doesn’t
When taking advantage of the anode heel effect, how should the patient be positioned? with the thicker anatomy under the cathode.
Air gap technique: an increase in OID increases contrast
An increase in the average energy of the beam affects contrast how? it decreases it
An increase in beam restriction affects contrast how? it increases contrast due to decreased scatter
An increase in grid ratio affects contrast how? it increases contrast because it absorbs more scatter
What is the contrast improvement factor? (K) it measures contrast with and without a grid
Created by: annaluz87