chapter 6 radio
radiolucent refers to
the portion of an image that is dark or black
radiolucent lacks density
radiopaque refers to
that portion of an image that appears light or white
density
the overall blackness or darkness of a dental image
if the density of an image appears too light or too dark the image considered
nondiagnostic
correct density allow the radiographer to view
black areas (such as air spaces
white areas ( including enamel,dentin, and bone)
gray areas ( ex soft tissue)
density increases
image appears darker
kilovoltage decreases
density decrease and image appear lighter
mA increased
the density inceases and the image appear darker
mA decreases
density decreases and image appear lighter
the longer the the exposure time
the more x-ray photons reach the receptor and continue to darken the image
contrast
the difference in the degree of blackness ( densities) adjacent areas on the dental image
high contrast
when viewed on a light source a dental image that has very dark areas and very light areas
low contrast
an image that does not have very dark and and very light areas but instead has many shades of gray
film contrast
refers to the chracteristics of the film that influence radiographic contrast
inherent qualities of the film
deremined and controlled by the film manufacturer and cannot be changed
film processing
is under the control of the dental radiographers
an increase in development time or developer temp result in
high contrast
subject contrast is determined by
size and thickness of patient tissue
high voltage
low subject contast----> and many shades of gray are seen on the dental radiographs
low kilovoltage
high subject contast-------> areas of black and white are seen on the image
only kilovoltage has a direct infuance on
contrast
x-ray with higher energy
are better able to penetrate tissue
high kilovoltage
low or decreases contrast -----> radiograph exhibits many shades of gray
low kilovoltage
high or increased contrast ------> radiograph has many black and white areas
scale contrast
the range of useful densities seen on a dental image
short scale contrast
an image show only 2 densities
black and white areas
lowe kilovoltage --> high contrast
long scale contrast
many densities or many shades of gray
high kilovoltage
low contrast
for finding dental caries
short scale contrast is beneficial
a short scale contrast may help allow the radiocent carries stand out because it demostrated more of the black and white areas
operator treating a patient with periodontal issues
increase kilovoltage --> produce long scale contrast : beneficial to see subtle in bone loss associated with periodontal disease
a premolar bite-wing reveals carious in both
maxilary and mandibular allowing the caries to be better viewed
stepwedge is made of
uniform-layered thicknesses
Geometric characteristics are 3
sharpness
magnification
distortion
sharpness
the sharpness of an image influanced by
focal spot size
movement
Focal spot size
ranges from 0.6 to 1,0 mm2 and determined by the manufacturer
the smaller the focal spot size the sharper the image
film composition
fast films -->contain larger crystals that produce less image sharpness
lower fims contain smaller crystals that produce more image sharpness
movment
more movement less sharp is the image
magnification refers to
appears larger than the acual size
to limit image magniication
use the langest targest receptor distance and shortest object receptor distance
to limit image distortion
portion the receptor and the tooth parallel to each other and direct the x-ray beam prependical to the receptor and the tooth