Digital Image Characteristics, Receptors, and Image Acquisition

Practice flashcards covering essential concepts from the lecture on Digital Image Characteristics, Receptors, and Image Acquisition.

What is a digital image characterized by?

An electronic data set that must be processed by the computer for viewing on a display monitor.

What controls brightness in image pre-processing?

Histogram Analysis.

What controls contrast in image pre-processing?

Look-up Tables (LUTs).

What are the two methods for creating electronic data sets?

Computed Radiography (CR) and Digital Radiography (DR).

What does a pixel represent in a digital image?

A picture element or the smallest component of a matrix.

How does matrix size affect digital image quality?

A larger matrix size includes more smaller pixels, improving image quality.

What relationship exists between pixel size and field of view?

An increase in field of view leads to an increase in pixel size.

What is spatial frequency defined by?

The unit of line pairs per millimeter (lp/mm).

How does dynamic range affect digital imaging?

It determines the ability of the detector to accurately capture exposure intensities.

What is modulation transfer function (MTF)?

A measure of the imaging system's ability to display contrast and spatial resolution.

What is detective quantum efficiency (DQE)?

It measures the efficiency of an image receptor in converting x-ray exposure into a usable electronic signal.

How does signal-to-noise ratio (SNR) affect image quality?

Higher SNR indicates stronger signal to noise, improving digital image quality.

What does contrast-to-noise ratio (CNR) measure?

The contrast resolution compared with the amount of noise in a digital image.

What is pixel bit depth?

The numerical value assigned to a pixel determines the number of shades of gray displayed.

How many shades of gray can be represented with 14 bits?

16,384 shades of gray.

What is required for improved spatial resolution in a digital image?

Smaller pixel sizes and higher pixel densities.

What is the relationship between pixel size and spatial resolution?

Pixel size and spatial resolution have an inverse relationship.

How does increasing pixel density affect spatial resolution?

Increases spatial resolution.

What does the Nyquist Frequency refer to in data sampling?

The minimum sampling frequency required to accurately reproduce an analog signal.

What impacts the dynamic range of a digital image receptor?

The detector's ability to accurately capture a wide range of radiation intensities.

What is the purpose of quality control checks for digital equipment?

To evaluate the performance of digital equipment.

What are the two main types of digital image receptors?

Computed Radiography (CR) and Digital Radiography (DR).

What are photostimulable phosphors used for in CR?

They capture and store energy from x-ray exposure.

What distinguishes direct radiography (DR) from computed radiography (CR)?

DR combines image capture and image readout in one step.

What is the main function of an analog-to-digital converter (ADC)?

To convert analog signals into digital data.

What is a key feature of flat-panel detectors used in DR?

They integrate signal storage, readout, and digitization electronics.

What is the significance of pixel electrode size in DR?

Smaller pixel size yields better spatial resolution.

What process does an indirect conversion detector use?

It converts remnant radiation into visible light before creating electrical charges.

What are the two classes of flat-panel detectors?

Indirect and direct conversion detectors.

How does the direct conversion detector process differ from the indirect?

It converts remnant radiation directly into electrical charges.

What is a characteristic of a single stage in direct conversion detectors?

Amorphous selenium is used to convert remnant radiation into electrical signals.

What is necessary for effective communication between a DR panel and the generator?

A wireless communication pathway.

What factors need to be respected in DR panel care?

Proper cleaning and avoiding mishandling.

How does increased pixel bit depth enhance contrast resolution?

It allows for more shades of gray to be displayed.

What defines spatial resolution in digital imaging?

The smallest detail that can be detected in the image.

What happens to stored energy in a CR imaging plate after exposure?

It begins to fade and should be processed promptly.

What should be routinely inspected in digital imaging systems?

Image receptors for potential artifacts and damage.

What is the advantage of high DQE in a system?

Lower radiation exposure is needed to produce a quality image.

What type of errors can occur from improper data sampling?

Alias waveforms that distort the original signal.

What happens to the contrast of an image with low dynamic range?

The contrast will be limited, impacting image quality.

How does increasing the sampling frequency affect spatial resolution?

It improves spatial resolution by decreasing sampling pitch.

What effect does noise have on image quality?

Increased noise decreases visibility of anatomical details.

In CR, what is the function of the reader unit?

To read and process the energy stored in the imaging plate.

What does an increase in pixel pitch indicate?

Larger distance from the center of one pixel to the next.

What can routine cleaning and inspection of image receptors help identify?

Potential issues affecting radiographic quality.

What is the effect of proper handling and preparation of DR panels?

It maintains optimal performance and image quality.

What happens to pixels when the display field of view is fixed but matrix size is increased?

Pixel size decreases.

What does a higher spatial frequency in an imaging system require?

The ability to see smaller objects clearly.

Why is window leveling important in image post-processing?

It adjusts the brightness of the image for better visibility.

How is image quality affected by improper exposure techniques?

It can compromise the quality and diagnostic usefulness of the image.

What should DR panel inspection include?

Checking for scratches, dirt, and other damage.

What determines pixel spacing in digital imaging?

The distance between adjacent pixel centers.

How is exposure latitude defined?

The range of exposure intensities that produce a diagnostic image.

What is the importance of adjusting contrast in digital images?

To enhance the visibility of anatomical details.

What is the role of a photodetector in the CR imaging system?

To convert light energy released from the imaging plate into an electrical signal.

What is defined as the area where pixel data is obtained?

The volume of tissue imaged by the x-ray.

What is the maximum contrast resolution achievable with a 16-bit system?

65,536 shades of gray.

In terms of image quality, what does increased SNR indicate?

Higher quality image with less noise visible.

What criterion is used to evaluate the performance of digital imaging systems?

Routine quality control checks.

What is the purpose of dose monitoring in radiography?

To assess patient radiation risk based on exposure.

What is the relationship between the matrix size and computer processing time?

A larger matrix requires increased processing time.

What aspect of digital radiography significantly reduces patient exposure?

High DQE ratings of the imaging systems.

How are the functionalities of CR systems characterized?

By their two-step image acquisition process.

What is essential for digital image quality?

A balance between dynamic range, contrast resolution, and noise minimize.