Chapter 8: Digital imaging

Means that images are produced with uniform density and contrast, regardless of the amount of exposure:

Automatic rescaling

Is a measure of the amount of radiation that was absorbed by the IR, not the patient:

Exposure Indicator/Index

One of the two types of digital imaging systems, this one was introduced in the United States in 1983 by Fuji Medical Systems of Japan

Computed radiography (CR)

Stores the latent image of the body part until it is processed:

Photostimulable phosphor (PSP)

The process of acquiring images of the body using x-rays, displaying them digitally, and viewing and storing them on a computer and in computer files:

Digital imaging

Is used to measure the capacity or accuracy of the digital detector to pass its spatial resolution characteristics to the final image:

Modulation Transfer Function (MTF)

When anatomy or the area of interest is too large to fit on one IR, multiple images can be joined together using a special computer program called:

Image stitching

Is a graph of the minimum and maximum signals in the image:

Histogram

Individual matrix squares are known as:

Pixels

Device that takes the stored charge and converts it into digital values:

Analog-to-digital converter

The digital image as seen on the monitor is described as having a:

Matrix

Describes the ability of a digital system to convert the x-ray input electric signal into a useful radiographic image:

Signal-to-noise ratio (SNR)

Is a processing technique in which each pixels frequency is averaged with the surrounding tissue’s pixel values:

Smoothing

Allows the limited operator to add text that is useful to have on an image

Image annotation

Controls the brightness on the image:

Window level

This detector converts light into electrons and stores them in capacitors

Complementary Metal Oxide Semiconductor (CMOS)

Can include cropping, sharpening, and other techniques to enhance the image:

Post processing

Occurs when the grid lines are not aligned with the laser scanning frequency of the CR reader:

Moire pattern

Is a processing technique in which images can be made sharper and have greatly increased contrast

Edge enhancement

The ability to distinguish anatomical structures of similar subject contrast:

Contrast resolution

Also known as masking, or shuttering, is used to blacken out the white collimation borders:

Electronic cropping

Controls the contrast in the image:

Window width

Is a one step process. Detectors convert the x-ray energy directly to an electric signal:

Direct conversion

The response of the detector to different levels of radiation exposure:

Dynamic range

Is used along with a histogram. It is a file of stored images for each projection.

Look-up table (LUT)

The amount of detail or sharpness of an image as seen on the monitor:

Spatial resolution

Is a two step process in which the x-ray energy is first converted into light and then converted into an electric signal:

Indirect conversion

Occurs when there are not enough photons in the detectors to provide a high-quality image:

Quantum mottle

One of the two types of digital imaging systems, this one is often referred to as cassetteless because they do not use a cassette with an IP

Digital radiography (DR)

Defective pixels that may cause a loss of patient information are called:

Dead pixels

Is a type of indirect conversion detector in which there is no photodiode and instead it converts the light from the scintillator to the electric signal:

Charge-coupled device (CCD)

Consist of either a scintillation screen or a photoconductor, which converts the x-ray photons directly into electrical signals:

Flat panel detectors (FPD)

Means that it does not absorb primary x-rays:

Radiolucent

A “cassette-based” digital imaging system is termed

Computed Radiography (CR)

When using DR systems, indirect conversion of x-ray energy requires how many steps?

Two

The system used to view and store digital x-ray images is called a __________.

PACS

When a CR plate is inserted into the reader for processing, the phosphor is scanned with a:

Laser beam

How many times can the phosphor in the CR plate be used?

10,000 times

When using indirect conversion DR systems, the light in the flat-panel detector is converted to an electric signal by the:

Photodiode

When splitting a CR cassette in half for two exposures, the half not being exposed should be covered with:

Lead

A minimum of how many sides of the collimated x-ray beam should be shown on the IR and image?

Two

After the imaging plate is scanned in the CR reader and the image sent to storage, the phosphor is exposed to a ___________________ to erase the anatomical image

White light

What is the size of the flat-panel detector inside the table of a DR system?

43 x 43 cm

A charge-coupled device (CCD) is used in an indirect conversion DR system to:

Convert light into electrical signals

Direct conversion DR processing requires how many steps to process the x-ray image?

One

The viewing monitor’s active viewing area is called a:

Matrix

Each square picture element in a digital viewing monitor is called a:

Pixel

The amount of detail or sharpness in the digital image is termed:

Spatial resolution

The greatest spatial resolution will be produced when the matrix is _________ and the pixels are _________.

Large; small

The ability to distinguish anatomical structures of similar subject contrast is termed:

Contrast resolution

The ability of the digital system to convert the x-ray input electric signal into a useful radiographic image is termed the

Signal-to-noise ratio (SNR)

“Noise” refers to the amount of information that is not useful in the radiographic image. This noise is referred to as:

Quantum mottle

The best quality radiographic image will be produced on the viewing monitor when there is ________ SNR, ______ noise.

high, low

Which control on the viewing station controls the density, or brightness, in the radiographic image?

Window level

“Window width” controls which aspect of the radiographic image?

Contrast

Which control on the viewing station can blacken the clear or white areas around the collimation edges of a radiograph?

Cropping

What is the name of the computer software function that allows separate radiographic images to be tied into one image for viewing?

Image stitching

The computer software function that allows any type of “text” to be written on a radiographic image is:

Image annotation

What is the name of the processing technique that can be used to increase contrast and sharpen the image?

Edge enhancement

What is the name of the computer software function that allows adjustment of the radiographic image after it has been processed?

Postprocessing

What is the term for the calibration of an image display system that ensures that all radiographic images’ gray scales are presented consistently?

DICOM gray-scale function

What artifact will be shown in the radiographic image if there is inadequate exposure technique?

Quantum mottle

The artifact that will occur when the grid lines are not aligned with the CR reader’s laser light is:

Moiré pattern

When there is foreign matter inside the CR imaging plate, an artifact may be shown called:

Light spots

The artifact that is caused by noise in the digital system’s electronics that creates lengthwise or crosswise lines is called a(n):

Extraneous line pattern

Digital radiographic images are stored, retrieved, sent, and viewed using an extensive image management system called the:

PACS

A CR plate inside the cassette can be exposed to light for how long before it will start to erase?

15 seconds

What is the weakest link in the digital imaging chain?

Viewing monitor

Which of the following should be checked regularly on the viewing monitor?

1. Viewing surface and air flow

2. Image quality using a test pattern

3. Resolution

All 3

What is the name of the technique in which each pixel’s frequency is averaged with the surrounding tissues’ pixel values in an effort to reduce noise in the image?

Smoothing

What is the name of the processing technique that allows the x-ray images to be produced with uniform density and contrast, regardless of the amount of exposure?

Automatic rescaling

If the CR reader does not erase the image plate completely, which artifact will appear?

Ghost or phantom

Sampling frequency is important in CR processing. The more signal that is sampled will have an image that has greater:

Spatial resolution

The capacity or accuracy of the digital detector to pass its spatial resolution characteristics to the final image is termed the:

Modulation transfer function (MTF)

The number of gray shades that a digital system can reproduce is termed:

Dynamic range

Blackening out of the white borders on an image so that no white light shows is termed?

Electronic cropping

The artifact that will occur when the grid lines are not aligned with the CR reader’s laser light is:

Moiré pattern

This occurs when there may be a defect in a component of the computer screen matrix that may cause a loss of patient information:

Dead pixels

A graph of the minimum and maximum signals in the digital image is called the:

Histogram