ch8 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 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 or picture elements

Takes the stored charge and converts it into digital values

Analog-to-digital-converter (ADC)

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

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 density in 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 the 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 into 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

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

Charged 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 (FPDs)

Means that it does not absorb primary x-rays

Radiolucent

A “cassette-based” digital imaging system is termed

Computed radiography (CR)

The purpose of the photostimulable phosphor plate is to

Store the image of the body part until processed

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 _____ system.

PACS

The front of the imaging plate is made of

A radiolucent material that does not absorb x-rays

Barium fluorohalide with europium is used

As the phosphor that absorbs the x-ray energy in the imaging plate (IP)

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

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

Photodiode

One of the main advantages of using CR and DR digital systems is

Ability to process images very fast

Which of the following must be used with digital-based x-ray processors to ensure that the ALARA concept is practiced?

An exposure technique chart

Quantum mottle occurs in digital images if

There is not enough photons reaching the IR

Which of the following should be used when imaging body parts that have extreme differences in tissue thickness?

Compensating filter

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

Lead

Which of the following is a true statement regarding the centering of the body part when using digital systems?

The part must be placed in the center of the plate or detector

The storage phosphors in the CR plate are hypersensitive to

Small levels of scatter radiation exposure

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

Two

Which of the following is important to use when using digital systems for mobile radiography?

kVp less than 90

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 × 43 cm

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

Convert light into an electrical signal

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

One

Which of the following artifacts appear along the length of travel on the image due to dust on the light guide?

White line

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

Which of the following matrix sizes will produce the best spatial resolution?

The biggest one 3000 × 3000 matrix

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

Large; small

The matrix of 1200 × 1800 will show how many pixels on the viewing monitor?

2,160,000

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

Contrast resolution

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

Dynamic range

The ability of the digital system to convert the x-ray input electrical signal into a useful radiographic images 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

Which of the following should never be placed on the radiographic image using electronic means (computer software)?

R and L markers

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

One of the most important aspects of setting the exposure factors when using digital systems is to ensure that the

kVp is set correctly

Which of the following tells the operator that the correct exposure has been received by the phosphors in the imaging plate?

Exposure indicator number

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

Postprocessing

The universally accepted standard for exchanging radiographic images inside and outside the institution, and among all manufacturers, is which of the following?

DICOM

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

DICOM grayscale function

Which radiographic examination would require image stitching of several separate images?

Full spine for scoliosis

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

Electronic cropping

What artifacts 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 readers laser light is

Moire pattern

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

Light spots

Which of the following artifacts can appear in the radiographic image if the CR imaging plate is not erased properly?

Phantom or ghost images

The artifact that is caused by noise in the digital systems, electronics that creates lengthwise or crosswise lines is called a(n)

Extraneous line pattern

Which of the following artifacts can occur if the CR imaging plate receives too much background or scatter radiation?

Fogging

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 race?

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 airflow

2. Image quality using a test pattern

3. Resolution

2 and 3

Which of the following takes the storage charge in the flat panel detector and converts it into a digital value?

Analog to digital converter (ADC)

Which of the following will be seen in the x-ray image of either the kVp or the mA is that too low for the projection?

Quantum mottle

What is the name of the technique in which each pixels frequency is averaged with the surrounding tissue pixel value 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?

Rescaling

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

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

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 characterizes to the final image is termed the

Modulation transfer function (MTF)

Which of the following contains a file of stored images for each projection, which are then referenced during processing of the digital image?

Look up table (LUT)