Chapter 3: Digital Radiographic Image Processing and Manipulation

Involves converting the digital input data to an image with appropriate brightness and contrast using contrast enhancement parameters

Contrast manipulation

This controls the ratio of black and white, or contrast

Window width

The post processing technique in which frequencies of areas of interest are known, those frequencies can be amplified and other frequencies suppressed

High-pass filtering

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

Nyquist theorem

This is a histogram of the luminance values derived during image acquisition. It is used as a reference to evaluate raw information and correct luminance values

Look-up table (LUT)

What is it called when excess light enters the eye, causing over sensitization of a chemical within the eye called rhodopsin and results in temporary white light blindness?

Veil glare

The detail or sharpness of an image is called:

Spatial resolution

Also known as foldover or biasing and causes mirroring of the signal at ¼ the frequency

Aliasing

Refers to the way anatomy is oriented on the imaging plate

Image orientation

This occurs when fewer pixels in the neighborhood or included in the signal average

Edge enhancement

When a sampled frequency is exactly at the Nyquist theorem, often a zero-amplitude signal will result called:

Critical frequency

This means that images are produced with uniform brightness and contrast, regardless of the amount of exposure used to acquire the image

Automatic rescaling

A function that allows retrieval of images from the PACS based on date of examination, patient name or number, examination number, pathologic condition, or anatomic area

Archive query

Occurs by averaging each pixel’s frequency with surrounding pixel values to remove high-frequency noise

Low-pass filtering

The data within the collimated area produce a graphic representation of the densities called a_____.

histogram

What is used to blacken out the white collimation borders, effectively eliminating veil glare?

Shuttering

Include things such as patient name, healthcare facility, patient identification number, date of birth, and examination date:

Patient demographics

The process of putting together multiple images that are too large to fit on one cassette using specialized software programs

Image stitching

Controls how bright or dark the screen image is:

Window level

The function that allows selection of preset terms and/or manual text input that can be particularly useful when such additional information is necessary:

Image annotation

Also known as low-pass filtering

Smoothing

The function that allows the QC technologist to select one or more local computers to receive images

Manual send

If the entire range of exposure were digitized, pixel values representing ______ would be digitized

all values

Data collected within the collimated border of the image are represented by a:

Histogram

The higher the kilovoltage peak, the _______ the histogram

narrower

If too few pixels are sampled, the result will be:

Low resolution

In an effort to display the pixels for the area of interest, when exposure is greater or less than what is needed to produce an image, ______ occurs.

automatic rescaling

Automatic rescaling means that images are produced, regardless of the amount of exposure, with:

Uniform brightness and contrast

Changing the slope of the look-up table graph will increase or decrease:

Contrast

If all of the shades were left in an image after processing, the contrast would be:

Too low

Changing the steepness of the exposure gradient:

Controls image contrast

The improper algorithm application may result in:

degradation of the image

The more manipulation of the image, the greater the:

Loss of information

Amplification of the frequencies of the areas of interest is known as:

Edge enhancement

Suppressing frequencies in the areas of interest is known as:

Masking

Low-pass filtering is also known as:

Smoothing

High-pass filtering is useful for enhancing:

Organs and soft tissue

Averaging the frequency of each pixel with surrounding pixel values to remove high-frequency noise is called:

Low-pass filtering

Image level parameters control image:

Brightness

Window width controls the ratio of black and white, also known as:

Contrast

Excessive light entering the eye when viewing an image is known as ______ glare

veil

An image manipulation process that fills in the background so that it is darkened is known as:

Shuttering

The process of joining two or more images into one continuous image is known as image:

Stitching

The workstation function that allows selection of preset terms or manual text input is termed image:

Annotation

Magnification of the entire image at the workstation is termed:

Zoom

The ability to send images to local network stations can be accomplished using the:

Manual send function

Proper patient demographic input is the responsibility of the:

Technologist

The data within the collimated area produce a _________ representation of the densities called a _________.

graphic; histogram

In 1928 ______ who was a researcher for AT&T, published a paper “certain topics in telegraph transmission theory”.

Harry Nyquist

The term _______ is used widely to explain this phenomenon. It refers to the use of automatic rescaling without regard to the appropriate exposure amount

dose creep

Low energy (low kVp) creates a _______ histogram; high energy (high kVp) creates a ______ histogram.

wider; narrower

The _______ or ______ of an image is referred to as spatial frequency resolution

detail; sharpness

The digital _______ are processed to mimic the appearance of screen-film images

images

Spatial frequency is measured in _____ per millimeter

line pairs

Preprocessing occurs _______ displaying the image

prior to

Once the image is stored in the ______, all postprocessing activities result in a loss of _______ from the original image

PACS; information

______ is useful for enhancing large structures such as organs and soft tissues, but it can be noisy

Low-pass filtering

Once _______ photons have been converted into electrical signals, these signals are available for processing and ______

X-ray; manipulation

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

Low-pass filtering

After the signal is obtained for each ______, the signal is averaged to shorten processing time and storage. The more pixels involved in the averaging, the smoother the image appears

pixel

The digital imaging _______ records a wide range of x-ray exposures. If the entire exposure were digitized, values at the extremely high and low ends of the exposure range would also be digitized, resulting in _____ tissue-density resolution.

receptor; low

Suppressing frequencies, also known as _______, can result in the loss of small detail

masking

In cassette-based PSP systems, although the imaging plate is able to store ______ for an extended period, the longer they are stored, the more energy they lose

electrons

Changing the _______ of the image may also change the location of the region of interest that was used during the preprocessing phase

orientation

The _______ function allows the QC technologist to select one or more local computers to receive images

manual send