processing terms Flashcards
raw data
is the exposure information prior to any processing algorithms
-raw data is converted into digital data using the analog to digital converter 
quantization
assigns each pixel number
-each number has an assigned grayscale value.
- when does it happen: the same time as the analog to digital conversion. ( digital part is the number)
bit depth
is the number of shades of gray that can be used to define each pixel higher, the bit depth higher the amount of information 
grayscale 
Digital term for scale of contrast
what is a histogram
A graphical display of the pixel intensity distribution for a digital image. Frequency of recorded exposure values. 
what are VOI
values of interest
they are stored in histogram models
what to VOI determine
The range of the histogram data set that should be included in the displayed image 
look up table
it allows gray scale, values in the recorded image to be remapped to new values to improve the final image in someway, such as appropriate brightness and contrast.
LUT’s are specific to anatomic areas.
LUT is the controller for
digital contrast ***
rescaling
corrects the appearance of an image one small exposure Errors are present.
-compensates for minor over exposure. Errors made by the tech. 
what is a dead pixel? 
A pixel with a malfunction or sensor error. Able to be seen on technologist panel. 
dead pixel correction
using a software technique, dead pixels are identified in the matrix and then removed from all subsequent images. 
flat fielding
Dead pixels are removed from the matrix by making a mask of the dead pixels. 
edge ethancement
increases the contrast along the edges of the structures.
- It improves the visibility of details if excessive edge enhancement is used, it can cause a halo artifact around edges.
equalization 
process by which soft tissue and bone are enhanced so all the information within a region of interest can be seen
example: chest images anatomy above, and below the diaphragm can be seen
**It can’t correct for severe under or over exposure 
smoothing OR noise, suppression, low pass, filtering
is used to mask the quantum noise in an image remove random noise areas.
disadvantage : smoothing causes a loss of spatial resolution
Smoothing can’t correct for significant under exposure *
post processing
when the image appears on the screen