Ch.33 Flashcards
On a DR system, off centering of the anatomy especially while using AEC, can result in unacceptable what?
Image Mottle
Exposure o the “raw” x-ray beam to the AEC detector cells results in what?
Early shut off causing underexposure
It takes ____ increases in kVp to show visible increase in for densities.
Large
Scatter radiation is primarily produced by what?
Large body parts and Large Field Sizes (poor collimation)
Why do large body parts and large field sizes cause scatter radiation?
Because both of these increase the volume of exposed tissue
This is defined as the range of exposure that can produce a diagnostically acceptable image for a particular imaging system.
Exposure Latitude
What is the exposure latitude for film based systems? Digital systems?
Film- -30% to +50%
Digital- =50% to +400%
For digital systems a much wider exposure latitude is allowed especially in the direction of what?
Over exposure
This is extreme overexposure causing a loss of data that results in a flat black appearance of the overexposed portion of the image. It is not a “fog” but a loss of data.
Saturation
It takes how much more than the normal exposure to reach saturation?
8-10 times
Some systems begin to show mottle at only what percent in mAs reduction?
30%
The frequent appearance of image mottle reported by many radiographers while using AEC is most likely due to the persistent use of what rather than the AEC itself?
Low kVp levels
If image mottle is a problem during AEC procedures, the kVp should be what until sufficient signal is reaching the detector cells.
Increased
For both CR and DR,no amount of mAs will ever compensate for inadequate what?
kVp
A CR and DR system can compensate image brightness and contrast for over penetration but it cannot what?
Replace or adjust information that is absent from the latent image due to under penetration.
