Radiographic density and contrast Flashcards
how do we see each other?
reflected light
how do we read?
reflected light
how do we interpret radiographs?
transmitted light
incident light
total light from source like a view box or illuminator that is partly
Absorbed
Reflected
Transmitted
radiographic density
blackness/darkness of an area of film
what is the usable range of radiographic density?
0.25-2.5
what is the most active component of radiographic film?
AgBr crystals
when exposed to xrays or visible light, AgBr is ionized and is converted to
metallic silver
the greater the radiation to reach the film, the ______ the amount of metallic silver formation
greater
what is the color of metallic silver?
black
parts of the film receiving more radiation appear _______
darker
what does an unexposed film look like
clear
concentration of electrons is _________ related to density
directly
radiolucency
an area of a radiograph representing a radiolucent object (dark area)
characteristics of radiolucency (6)
- more x-radiation is transmitted
- the more trapped electrons, the more and image appears
- less effective in absorbing
- dark
- more x-rays reach receptor
- more metallic silver
radiopacity
area of radiograph representing a radiopaque object (Light area)
radiopaque characteristics (6)
- less transmitted
- less electrons
- MORE absorbed
- lighter
- less xrays reach receptor
- less metallic silver
radiographic contrast
observed differences in adjoining radiographic densities
differentiate structures based on 3 things:
density
thickness
chemical composition
density of dentin is similar to the density of what?
cementum
if the differences between radiographic densities are GREAT - it is ____ contrast
if the differences are SMALL - it is ______ contrast
HIGH
LOW
high contrast characteristics (5)
SHORT scale contrast LOWER kVp LESS shades of grey identifies caries intraoral kVp: 70
low contrast characteristics (5)
LONG scale contrast HIGHER kVp MORE shades of grey identifies less dense objects extraoral kVp: 90
