Ch. 3 test aug 31st Digital Radiographic image processing and manipulation


takes place in the computer where the algorithms determine the image histogram

post processing

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

Nyquist Theorem

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?

sampling theorem

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 ______ _____

signal loss

what are the extra steps during image acquisition?

- indirect capture- direct capture

indirect capture

x-rays to light to electrical signal

direct capture

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