Image Analysis Radiographic Contrast 1.3 Flashcards
Visibility of detail factor that describes the difference between adjacent densities on an image
contrast
What must be present on an image for anatomic structures to be visualized?
entity it must exhibit contrasting shades of black, white, and gray compared to the structures that surround it
Define short scale contrast
images the display just a few gray shades and appear mostly black and white
define long scale contrast
images that display many shades of gray and few blacks and whites
Contrast caused by the anatomic density, atomic number, and thickness differences of the patients body parts, and how differently each tissue composition will absorb x-ray photons
subject contrast
what the kVp factor determines
the energy of x-ray photons produced and the differential absorption that occurs in the patinets tissues as the x-ray pass thru the patients body
what is the penetrating power of the beam?
kVp
What type of images does using high kVp produce?
low contrast images
Using high kVp causes more what?
scatter
How does an image appear when using high kVp?
long-scale contrast (few blacks and whites and many grays)
What type of image does low kVp produce?
high contrast images–produces low energy photons that are easily absorbed
What images will exhibit when using low kVp
short scale contrast (mostly black and white with few grays)
How images will appear when using low KVP?
appear mostly black and white
What must be evaluated to obtain desired level of contrast and gray scale
each patients body part being imaged and select the appropriate kVp for that specific patient
Define optimum kVp
the kVp that will provide adequate part penetration and sufficient image contrast
what to do to the technique when you need higher contrast and will have to alter the technical factors always from optimum kVp
decrease original kVp by 15%, and increase mAs by 100% alter factors away from optimum kVp