FINAL TQ PART VI Flashcards
name this definition?
used to measure film blackening
optical density
equation for optical density?
OD=log(Isubo/Isubt)
Isubo=light intensity on film
Isubt=light transmitted through film
for every 0.3 change in optical density, the %T inversely changes by?
a factor of 2.0
as optical density increases, what is the affect on transmittance?
- 3 equals?
- 0 equals?
decreases (dark film)
50% transmittance
1% transmittance (too dark)
increased slope equals increased?
film contrast
name this definition?
range of exposures over which the image receptor responds with ODs in the diagnostically useful range
latitude
with latitude, the wider, what is the affect on mAs and error?
*how is this related to film contrast?
mAs vary more result in diagnostic image
greater margin for error
*inversely related
film latitude is equal to what and related to contrast how?
range of grey tones
inversely related
computed radiography allows for what digital concept? this equals?
*digital image detectors are sensitive to how many differences in gray tones
windowing, gray scale expansion
*1000 differences in gray tone
what is an important feature of digital imaging?
the computers ability to mathematically bring density differences into the visual range
in terms of windowing, you increase the window level you increase?
in terms of windowing, you increase the window width you decrease?
image density
image contrast (gray scale expansion)
in terms of windowing, what is said to control visibility of detail?
window width
image quality is image clarity based on what 2 principles?
contrast and detail
radiographic contrast is based on what three principles?
film contrast
subject contrast
fog and scatter
image contrast resulting from patient interactions equals? and based on what?
subject contrast
thickness differences
density differences
atomic no differences
quality of radiation (kVp)
