takes place in the computer where the algorithms determine the image histogram
done by the technologist through various user functions
what does data recognition program search for in the image histogram?
anatomy recorded on the imaging plate by finding collimation edges, and eliminating scatter outside the collimation
what results in failure to find the collimation edges in the image histogram?
incorrect data collection
what do images look like if there is incorrect data collection?
images may be too bright or too dark
what does centering anatomy to the imaging plate ensure?
appropriate recorded intensities are located
what happens when you fail to center anatomy to the center of the imaging plate?
result in an image that is too bright or dark
failure to find collimated images equals what kind of image
too light or too dark
failure to center part to IR equals
too light or too dark image
a graphical representation of exposure values collected from the imaging plate
horizontal axis of histogram shows
tone values (gray value) x-axis
vertical axis of histogram
number of pixels in each tone (y-axis)
what do values on one end of histogram represent?
the black areas (greater acquired signals)
what vary towards the opposite end in a histogram?
tones vary toward the opposite end and get brighter and the middle area is the medium tones
what does the extreme opposite end of the histogram represent?
white tones ( no acquired signals)
what is the process of histogram formation?
- IR is scanned- image location and orientation are determined- size of the signal is determined- value is placed on each pixel- generated from the image data
what is allows a histogram to generated to find?
useful signal by locating the minimum (S1) and maximum (S2) signals within the anatomic regions of interest in the image
what is the x-axis related to in a histogram?
amount of exposure signal
what is the y-axis in a histogram?
displays the number of pixels for each exposure
what does graphic representation appear as?
series of peaks and valleys and has a pattern that varies for each body part
what does a low energy kVp give a lower/wider histogram?
what does a high energy kVp wider/narrow histogram?
what shows the distribution of pixel values for any given exposure?
what is essential when choosing histogram analysis?
choosing the correct anatomic region on the menu before exposing
when does image correction take place?
during histogram analysis
Describes the method of converting analog audio signals into digital format by sampling at twice the highest frequency of the audio.
what is the nyquist therem often referred to as?
At least ______ the number of pixels needed to form the image must be sampled
if too few/many are sampled, the result is a lack of resolution
oversampling does not result in
additional useful information
during image acquisition, extra steps result in ______ _____
what are the extra steps during image acquisition?
- indirect capture- direct capture
x-rays to light to electrical signal
x-rays to electrical signal
the indirect method of image acquisition has the highest/lowest potential for loss of signal
In PSP plates, the longer the electrons are stored, the __
more energy they lose
When laser stimulates electrons, some lower energy electrons _____ _____ _____ ____
escape the active layer
if enough energy was lost, some lower energy electrons are ___________________
not stimulated enough to escape, and information is lost