Ch3 Digital Radiographic Image Process and Manipulation. PACS

preprocessing

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

postprocessing

done by the technologist through various user functions

psp

plate that records a wide range of x-ray exposures

finding collimation and eliminating scatter

data recognition programs search for anatomy recorded on the imaging plate by what?

signal

information within the collimated area is the __________ used for image data.

incorrect

failure of the system to find the collimation edges can results in ________ data collection

too bright or too dark

how may the image look if the system cannot find the collimated edges?

centering the anatomy

what is just as important as the system finding the collimation edges?

centering the anatomy

what ensures that appropriate recorded densities are located

the part

histograms are dependent on what?

histogram

a graphical representation of exposure values collected from the imaging plate

horizontal axis

where is the value of each tone represented on a histogram?

vertical axis

where is the number of pixels in each tone represented on a histogram?

darker

values to the left of a histogram are?

brighter

values to the right of a histogram are?

image sampling

plate is scanned.

image location and orientation are determined.

size of the signal is determined.

value is placed on each pixel.

a histogram is generated from the image data.

histogram

what compares raw data of the current exposure and a "normal one"?

wider

a low energy (kVp) histogram is?

narrow

a high energy (kVp) histogram is?

1928

when was the nyquist theorm introduced?

claude shannon

who presented a mathematical proof of the nyquist theory?

1928

when did claude shannon present a mathematical proof of the nyquist theory?

sampling theorm

what is another name for the nyquist theorm

nyquist theorm

when sampling a signal, the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be as close to the original as possible

lack of resolution

the nyquist theorm states that if too few pixels are sampled this will happen

yes

is there some light that is lost during the light to digital conversion using psp?

light spread

what happens because the small distance between the phosphor plate surface and the photosensitive diode of the photomultiplier

loss of information

what happens when there is light spread?

fpd

what loses fewer signals to light spread?

aliasing

what occurs when the spatial frequency is greater than the nyquist frequency

aliasing

what occurs when sampling occurs less than twice per cycle

automatic rescaling

when a exposure is greater than or less than what is needed to produce an image

automatic rescaling

problems with ________ include:

too little exposure results in quantum mottle

too much exposure results in a loss of contrast and loss of distinct edges because of detector saturation

dose creep

unnecessary high doses over time

look up table

a histogram of the luminance values derived during image acquisition

contrast

what can be increased or decreased by changing the slope of the graph in a look up table?

brightness

what can be increased or decreased by moving the line up or down the y-axis in a look up table

quality control workstation

functions of a __________ include:

image processing parameters

contrast manipulation

spatial frequency resolution

spatial frequency filtering

digital

out of digital imaging and film/screen imaging which has a greater dynamic range?

digitization

what gives the image a wide latitude?

spatial frequency resolution

referred to as the detail or sharpness of the image

edge enhancement

the averaging of the signal that occurs to shorten processing time and storage, after the signal is obtained for each pixel

high pass filtering

what results in an increase of contrast and edge enhancement

small details

masking can result in a loss of what?

smoothing

what results from averaging the frequency of each pixel with surrounding pixel values to remove high frequency noise

noise and contrast

smoothing results in a reduction of what?

smoothing

what is useful for viewing small structures such as fine bone tissues

image manipulation

a branch of basic functions of the processing system that includes:

window level and window width

background removal or shutter

image orientation

image stitching

image annotation

magnification

image management

a branch of basic functions of the processing system that includes:

patient demographics input

manual send

archive query

window level

what controls how light or dark the image is?

window width

what controls the ratio of black to white, or contrast

shutter

when unexposed borders around the collimation edges allow excess light to enter the eye

veil glare

what causes over sensitization of a chemical withing the eye called rhodopsin?

orientation

the way the anatomy is oriented on the imaging plate

stitching

used for anatomy or areas of interest too large to fit on one cassette

annotation

information other than standard identification must be added to the image

identification

proper ________ of the patient is even more critical with digital imaging, because retrieval cab be nearly impossible

archive query

used for historical images, this function allows retrieval of images from the PACS based on:

date of exam

patient name or number

exam number

pathologic condition

anatomic area

aliasing

a loss of digital information because of a fluctuating signal; also known as fold over, biasing, or wraparound

archive query

a software function that allows historical information to be gathered from digital storage, such as multiple examinations, a range of dates, or by pathology

automatic rescaling

occurs when exposure is greater or less than the optimal amount to produce a diagnostic image; it is the effort of the computer to "fix" exposure errors

contrast manipulation

conversion of the digital image using contrast enhancement parameters

critical frequency

the frequency of a signal that exactly matches the nyquist frequency, resulting in a zer amplitude signal caused by phase shifts

edge enhancement

occurs when fewer pixels in the neighborhood are included in the signal average; the smaller the neighborhood, the greater the enhancement

high pass filtering

technique for the enhancement of contrast and edge that amplifies the frequencies of areas of interest that are known and suppresses frequencies outside the area of interest

histogram

a graphic representation of all the digitally recorded signals of a digital x-ray exposure

image annotation

software function that allows text or markers to be digitally added to an image

image orientation

identification of the top or side of an image

image sampling

the amount of information gathered from pixel storage

image stitching

process of "sewing" together multiple image to form one continuous image

look up table

a reference histogram of the luminance values derived during image acquisition

low pass filtering

a result of average each pixel's frequency with surrounding pixel values to remove high frequency noise; the result is a reduction of noise and contrast; useful for viewing small structures such as fine bone

manual send

a computer function that allows image to be sent to specified reading stations

nyquist theorm

when sampling a signal such as the conversion from an analog to a digital image, the sampling frequency must be greater than twice the bandwidth of the input signal so that the reconstruction of the original image will be nearly perfect

patient demographics

input information regarding patient age, identifying number, ordering physician, and so on

shuttering

used to blacken out the white collimation borders in a digital image, effectively eliminating veil glare

smoothing

also known as low pass filtering, the result of averaging each pixel's frequency with surrounding pixel values to remove high frequency noise

spatial frequency resolution

the amount of detail or sharpness in a digital image

window level

the image manipulation parameter that changes screen image brightness

window width

the image manipulation parameter that changes screen image contrast

image sampling

the useful signal is determined during which part of image processing?