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Contrast

Ch. 29

QuestionAnswer
______ is the difference between adjacent densities. contrast
The term ___________ describes the concept of contrast as it is displayed on a soft-copy monitor for digital images. dynamic range
The term __________ accurately describes the digital processing that produces changes in the range of density/brightness. window width
Any change in overall ____ will affect contrast. density
_____ contrast provides more diagnostic information, if it is still in visible range. Low
High contrast is also known as: Few shades of gray Increased contrast Low kVp Short scale contrast Short dynamic range/window width
Low contrast is also known as: Many shades of gray Decreased contrast High kVp Long scale contrast Large dynamic range/window width
___________ is the number of useful visible densities or shades of gray. Scale of contrast
_____ is the total range of density values recorded by the image receptor. Physical contrast
______ is the total range of density values that can be perceived by the human eye. Visible contrast
Compression or expansion of densities can be accomplished by the following: change in the film's Dlog E curve, adjustments in kVp or by the use of window width.
___________ is the range of densities that the film is capable of recording. Film contrast
Film contrast depends on four factors: intensifying screens film density D log E curve Processing
Intensifying screens create an inherently _________ image. higher contrast
Film contrast also changes with changes in ______. film density
Excessive or inadequate film density will _____ contrast. (especially true in the toe and shoulder regions of the D log E curve) decrease
Where on the D log E curve is contrast maximized? straight line portion
As the slope of the curve becomes steeper, contrast is _______. increased
Increased developer temperature, time, and replenishment cause increased fog and _________. decreased contrast
__________ is the range of differences in the intensity of the x-ray beam after it has been attenuated by the subject. subject contrast
______ is the primary controller of subject contrast. Kilovoltage (kVp)
An increase in kVp will lead to a wider range of exposures on the IR, which results in an overall _____ contrast. lower
As long as the kVp is adequate to penetrate the part being examined, low kVp will produce _____ subject contrast. high
High kVp produces a _______ range of relative exposures, while low kVp will produce an _______ range of relative exposures. compressed; expanded
As kVp increases, the percentage of _________ increases. Compton interactions
As a result of the increase in the amount of scatter reaching the IR, contrast is _________. decreased
Fog can be caused by subjecting film to: heat low level ionizing radiation chemical fumes
Any factor that results in an increase in fog will cause a _______ in contrast. decrease
When the difference between adjacent thicknesses is great, subject contrast is ______; when little difference exists in the thickness of adjacent body parts, subject contrast is _____. increased; decreased
When the amount of overall thickness of a body part increases = ____ scatter and ____ subject contrast. increased; decreased
A decrease in overall body part thickness/field size = _______ subject contrast increased
Materials with a higher Z# absorbs a _______% of the x-ray beam than low Z# materials. greater
The presence of more electrons will enable _____ interactions to occur. more
When the difference between the average Z# of adjacent tissues is great, subject contrast is ________. (and vice versa) increased
Contrast media _______ subject contrast by introducing greater differences in Z# variations than those that exist naturally. increase
When the difference between the densities of adjacent tissues is great, subject contrast is _______.(and vice versa) increased
The major consideration in evaluating visible contrast is verification that a proper range of ______ is visible in the area of interest. densities
A _______ is tool to help focus on the contrast in a certain area. contrast mask
A visible change in contrast will not be perceived until kVp is changed by _______ 4-12%.
There is no reason to repeat an exposure for contrast reasons unless a _______ change is made. 4-5%
The rule for contrast changes is to make adjustments of _________ percent. 15 or 8
Contrast evaluation can be made only when sufficient ______ exists to permit the range of contrast to be seen. density
Photoelectric effect interactions ______ as kVp decreases. increases
A given kVp for a 3 phase generator will produce a _____ contrast than a single pase unit. lower
kVp affects contrast and has the most _____ effect on the image. direct
Influencing factors has a ______ effect on the image. less direct
_____ is the controlling factor of contrast. kVp
As kVp increases, contrast _____. (and vice versa) decreases
kVp increases amount of radiation fog, which will in result _____ contrast. decrease
When a film is either over or underexposed, the contrast is _______. decreased
What effect do focal spot size and anode heel effect have on contrast? none
Removing scatter from the image will _____ contrast. increase
An increase in filtration will ______ contrast. decrease
Beam restriction will reduce the amount of scatter and therefore ______ contrast. increase
As the anatomical part size increases, the amount of scatter created by the part also increases, which will result in a _____ in contrast. decrease
High Z#'s will cause more photoelectric absorption, resulting in _______ contrast. increased
Grids improve _____ by removing scatter before it reaches the IR. contrast
Higher ratio grids remove more scatter - and will result in a ____ contrast image. higher
_____ is the amount of shades of gray a pixel can record. Bit depth
The larger the bit depth the ____ shades of gray the can be recorded. more
Decreasing film development time, temp, or replenishmen rate from the optimal range will ____ contrast. decrease