Image Characteristics Flashcards
X-Ray Quality
average energy and penetrating power of the beam; controlled by kV (dental = 65-100kV)
Exposure time
measured in impulses, 1 impulse = 1/60 second
kV Peak Rule
increase kVp by 15, decrease exposure time by 1/2.
decrease kVp by 15, increase exposure time by 2x.
3 Exposure Factors
time, mA, kVp
Density
overall darkness of film; controlled by mA; mA + exposure time have inverse relationship
Constrast
how sharply dark/light areas are separated; high = few shades of gray (low kVp) / low = many shades of gray (high kVp)
Short-Scale Contrast
black/white densities visible; high contrast
Long-Scale Contrast
many shades of gray; low contrast
Radiolucent
dark/black; pulp. low atomic #
Radiopaque
light/white; enamel, bone. high atomic #
mAs
mA x s = mAs
Inverse Square Law
distance and intensity have inverse relationship; exposure time follows distance change
Geometric Characteristics
sharpness, magnification, distortion - must be minimized for an accurate image
Penumbra
zone of unsharpness along edges of images
Sharpness influences
[detail/resolution] affected by motion