Digital Radiography and Image Processing Review

Flashcards created from the lecture notes covering Digital Radiography (DR), Computed Radiography (CR), image processing, histograms, detectors, and DICOM standards.

What does the deviation index compare?

Acquired exposure to target exposure

What did the creation of electronic data sets allow in medical imaging?

Computer manipulation of imaging data

Digital radiography receptors are commonly referred to as:

Flat-panel detectors

The primary function of a look-up table (LUT) is to adjust:

Image contrast

High-pass filtering is most closely associated with:

Edge enhancement

Pixel pitch is dependent on which two factors?

Matrix size and image receptor size

Early digital computerization was first applied to which imaging modalities?

CT and ultrasound

Higher DQE is associated with:

Lower patient dose for the same image quality

Which process begins grayscale point processing?

Creation of a histogram

Histogram rescaling involves comparing the acquired histogram to a:

Reference histogram

Histogram equalization is recognized as a standard procedure by which organization?

American College of Radiology (ACR)

One responsibility of the technologist when using EI is to:

Ensure ALARA compliance

Major developments in digital image processing occurred primarily during which decades?

1970s through 1990s

A histogram is best described as:

A graphical representation of signal values

Standardized EI and DI values are especially important because:

New and upgraded digital equipment continues to be introduced

The field of view (FOV) determines the:

Area of anatomy included in the image

Gray scale bit depth in digital imaging typically ranges between:

$8$ and $32$ bits

How many bits are required to form one byte?

Eight

Which exposure condition cannot be corrected by histogram rescaling?

Excessive overexposure

Point processing operations primarily involve:

Adjusting pixel values one at a time

Why should overexposure be avoided in CR imaging despite wide exposure latitude?

To reduce unnecessary patient dose

Typical CR plate throughput ranges between:

$30$ and $200$ plates per hour

What allows liberated electrons in the imaging plate to move within the crystal structure?

Laser stimulation

Which step in CR imaging involves formation of a latent image?

Image acquisition

CR image acquisition can be performed using which setup?

Tabletop or with a grid

Which two methods are used to read CR imaging plates?

Point-by-point and line-by-line readout

Computed radiography systems use which type of image receptor?

Photostimulable imaging plates

Low band-pass filtering is primarily used to:

Suppress visible image noise

Computed radiography was first developed during which decade?

Early 1980s

In computed radiography, data manipulation is also known as:

Post-processing

Which factor can falsely trigger collimator edge identification algorithms?

Prosthetic devices or implants

Proper positioning in CR imaging is important because it helps prevent:

Histogram analysis errors

Which method may be used to collect the electrical signal produced in an indirect DR detector?

Thin-film transistor or charge-coupled device

In a TFT array, pixel size is directly related to the size of the:

Detector element (DEL)

Which action helps prevent fluid-related damage to DR panels during portable exams?

Enclosing the panel in a protective bag

Direct conversion detectors use which material as a photoconductor?

Amorphous selenium

Exceeding weight load limits on a DR panel may result in:

Permanent mechanical damage

A limitation of traditional generator-dependent DR panels is that they:

Use vendor-specific interfaces

Which scintillation materials are commonly used in indirect flat-panel detectors?

Cesium iodide and gadolinium oxysulfide

Flat-panel detectors were first introduced into clinical radiography in approximately:

$$1995$$

In digital radiography, the latent image is best described as:

Electrical signal values stored in detector elements

A characteristic limitation associated with indirect conversion detectors is:

Light spread that may reduce spatial resolution

Thin-film transistors are used in which detector types?

Both indirect and direct detectors

Which component is common to both direct and indirect flat-panel detector systems for signal readout?

Thin-film transistor (TFT) array

Panels that detect x-radiation without a direct generator interface are commonly called:

Trigger panels

In auto-detection technology, the TFT array begins collecting signal when:

X-radiation is detected by the panel

Which configuration describes a DR panel that is permanently mounted within the imaging system?

Integral to equipment design

The primary distinction between direct and indirect DR panels is based on:

The method of x-ray energy conversion

TFT fill factor is defined as the percentage of a detector element that consists of:

Active sensing material

Responsibility for understanding manufacturer-specific DR panel restrictions belongs to the:

Medical physicist

What does DICOM stand for?

Digital Imaging and Communications in Medicine

Analog-to-digital conversion consists of which two steps?

Sampling and quantification

LUT adjustments are most similar to changing which film characteristic?

D-log-E curve

What is the purpose of applying a look-up table (LUT)?

To map pixel values to display brightness

What process converts analog signals into digital data?

Analog-to-digital conversion

The volume of interest (VOI) is identified during which step?

Histogram analysis

Point processing in digital imaging affects:

Individual pixels

What is a key advantage of having a quantifiable exposure index?

It allows objective assessment of image quality and ALARA compliance

Why were healthcare reimbursement structures modified in favor of DR systems?

To encourage migration from CR to DR

A DQE value of $1$ represents:

$100$ percent efficiency with no information loss

The primary purpose of the DICOM standard is to:

Ensure consistent storage, display, and sharing of images

Why is there no universal exposure index system in digital radiography?

Different manufacturers use different exposure indicator systems

Density resolution increases when:

Gray scale bit depth increases

LUT values are assigned to which data points?

Pixel values in the histogram

Sampling frequency is commonly expressed as:

Pixels per millimeter

Where are electrons trapped during latent image formation?

Europium sites

The CR readout process occurs in which manner?

Line by line only

Photostimulable imaging plates are best described as:

Reusable, multilayer rigid sheets

Which post-processing technique enhances cortical margins and trabecular detail?

High band-pass filtering

Which interaction is primarily responsible for energy absorption in CR phosphors?

Photoelectric interaction

Suboptimum mAs exposures in CR imaging are most likely to result in:

Increased quantum noise

Pixel pitch refers to the:

Distance between adjacent pixels

What type of laser is used to scan CR imaging plates?

Neon–helium laser

During digitization, the analog signal is converted into:

A limited set of discrete values

Spatial resolution in a TFT-based detector is indirectly related to:

DEL dimensions

Why does amorphous silicon require the use of a scintillator in indirect detectors?

Its atomic number is too low to efficiently absorb x-ray energy

Flat-panel detectors are most accurately described as part of which imaging modality?

Digital radiography (DR)

Which feature distinguishes direct detectors from indirect detectors?

Absence of a scintillation layer

A detector with a $95$ percent fill factor contains approximately what percentage of non-sensing electronics?

$5$ percent

In digital radiography, how can the latent image also be described?

A stored phosphor image

Which detector class converts x-ray energy directly into an electrical signal without producing light?

Direct conversion

Which image processing step identifies relevant anatomy and excludes non-image areas?

Exposure field recognition

Which term is most commonly used in clinical practice to refer to a flat-panel detector?

Panel