Displays and Image Processing

Flashcards covering key concepts in displays and image processing in ultrasound.

Bistable Display

Displays an image composed of only 2 shades: black and white.

Gray Scale Display

Presents multiple levels of brightness, allowing differentiation of biologic tissues.

Contrast (Display)

Determines the range of brilliancies within the displayed image; bistable images are high contrast.

Brightness (Display)

Determines the brilliance of the displayed image.

Scan Converter

Device that stores information and then later displays it, translating data from spoke format into video format.

Writing (Scan Converter)

The storage of information in the scan converter.

Reading (Scan Converter)

Retrieving image data from the scan converter for display.

Analog Numbers

Real-world numbers with unlimited and continuous range of values.

Digital Numbers

Numbers associated with computer devices, having discrete values.

Analog Scan Converter

Uses a funnel-shaped vacuum tube to store electrons on a dielectric matrix; now obsolete due to limitations.

Digital Scan Converter

Uses computer technology to convert images into numbers for storage and processing; offers uniformity, stability, and accuracy.

Pixel

Picture Element - Smallest building block of a digital picture.

Pixel Density

Number of pixel elements per inch; higher density improves spatial resolution.

Bit

Binary Digit - Smallest amount of computer memory with a value of either 0 or 1.

Byte

Group of eight bits of computer memory.

Word

Consists of two bytes (16 bits).

A-to-D Converter

Converts electrical signals from the transducer from analog to digital form.

D-to-A Converter

Translates digital signals back into analog form for display on analog devices.

Preprocessing

Manipulation of image data before storage in the scan converter; cannot be reversed.

Postprocessing

Manipulation of image data after storage in the scan converter; changes can be reversed.

Read Magnification

Occurs after image data is stored; displays only original data pertaining to the ROI; spatial resolution does not change; postprocessing.

Write Magnification

Applied during data acquisition; rescans only the ROI and writes new data; improves spatial resolution; preprocessing.

Coded Excitation

Method of improving image quality using long sound pulses to improve penetration and resolution.

Spatial Compounding

Uses sonographic information from different imaging angles to produce a single image; reduces speckle and shadowing artifacts.

Frequency Compounding

Reduces speckle artifact by dividing the reflected signal into sub-bands and combining images from each.

Edge Enhancement

Image processing method that makes pictures look sharper by emphasizing edge boundaries.

Temporal Compounding

Persistence, temporal averaging - Displays information from older images superimposed on the current frame; creates a smoother image.

Fill-in Interpolation

Method of constructing new data points to fill gaps between scan lines in sector-shaped images; preprocessing.

Elastography

Dynamic technique that produces images based on tissue stiffness; potential for cancer diagnosis.

PACS

Picture Archiving and Communications System - Digital ultrasound lab for storing and transmitting medical images.

DICOM

Digital Imaging and Computers in Medicine - A set of rules that allows imaging systems to share information on a network.