Ultrasound Physics: Instrumentation, Displays, Dynamic Range, Harmonics, and Artifacts

Comprehensive vocabulary flashcards covering ultrasound pulsed echo instrumentation, displays and image processing, dynamic range, harmonics and contrast agents, and artifacts.

Master Synchronizer

maintains and organizes The proper timing and interaction of the systems components

Pulser

Create electrical signals that excite the transducer PZT crystals and create sound beams

Output Power

Effects images, brightness by altering the strength of the sound of the train user sent to the body

Thermal Index

Calculate a number related to the potential for tissue heating resulting from the sound beam

Mechanical Index (Instrumentation)

Calculate number related to the potential for cavitation produced by the ultrasound be

Noise

Random and persistent disturbance, the curse or reduces a signal clarity

Signal to Noise Ratio

Is a comparison of the meaningful information in an image compared to the amount of contamination

Beam Former

receives the pulser signal electrical spike and distributes it to numerous active elements of a array transducer

Digital Beam Former

Modern transformers use advanced micro processes, certain technology, and producing signals in digital format

Switch

Protect the delicate receiver components from the powerful signals that created for pulse transmission

Receiver

Transforms the electrical signals from the transducer in to a form Suitable for Display

Amplification

Each electronic signal returning from the transducer is made larger

Receiver gain

Increases amplitude of all returning signals equally making the entire image brighter

Preamplification

Is the process of improving the quality of a signal before it is amplified

Compensation

The receiver correct for attenuation

TGCs

X Axis indicates the amount of compensation Y axis indicates reflector depth

Near gain

Superficial depths reflections undergo a constant amount of compensation

Delay

Steps at which variable compensation begins

Slope

Compensation, correct for the effects of increasing attenuation that result from increasing path length

Knee

Reflections are maximally compensated by the ultrasound system

Far gain

Indicates the maximum amount of compensation that the receiver can provide

Compression (Instrumentation)

Is performed without altering the ranking between the signals

Dynamic Range (Instrumentation)

Is also known as compression

Demondulation

Changes the electrical signals within the receiver into a form, more suitable for display on a monitor

Rectification

Convert all negative voltage is into positive voltage

Smoothing

Places to smooth line around the bumps and evens them out

Rejection

Allows sonographer to control low level gray scale information within the data will appear on the display image

Threshold

Also known as rejection

Dynamic Frequency Tuning

Use only the high frequency part of the reflected pulse band which to create the superficial portion of the image

ALARA

When an entire image is too bright or too dark

Display

Device that represents the process data

Bistable

Only black and white appear

Grayscale display

Presents multiple levels of brightness allows many shades of gray

Contrast

Determines the range of brilliance is within the displayed image

Brightness

Determines the brilliance of the display image

Scan converters

Translate the information from the book format into the video format

Analog number

Real world numbers that are found in our everyday lives

Digital number

Associated with computer devices

Analog scan converter

Is a funnel shaped vacuum tube with an electron gun located within its smaller end

Digital scan converter

Use computer technology to convert images into numbers

Pixel

Smallest building block of a digital picture

Pixel density

Number of picture elements per inch

Bit

Smallest amount of computer memory

Binary number

Group of bits and is simply a series of zeros and ones

Byte

Group of eight bits of computer memory

Word

Computer memory consists of two bytes or 16 bites

Contrast resolution

Ability to distinguish between subtle differences in grayscale

Analog to Digital Converter

To move information from real world to the computer world

Digital to Analog Converter

To move information from the computer world back to the real world

Video Display

The signal now in analog is presented on

Preprocessing

Any process of the reflected signals before storage

Postprocessing

Any process after storage and the digital scan converter

Read magnification

Occurs active image data is stored in the scan converter

Write magnification

Is applied during data acquisition before storage and the scan converter

Region of Interest

Specific area of portion of an image chosen by the sonographer undergo write magnification

Coded Excitation

Improving image quality

Spatial Compounding

Using sonographic information from several different imaging angles to produce a single image

Frequency Compounding

Reduces speckle artifact, and noise and ultrasound images

Edge Enhancement

Image processing method that makes pictures look sharper

Temporal Compounding

Image processing technique that continues to display information from older images

Persistence

Also known as temporal compounding

Fill-in Interpolation

Constructing new simulated data points to fill in the gaps

Elastography

Produces images from sound reflections in an entirely new way

PACS

Describes the digital ultrasound laboratory in which images and additional medical information or digitized and sort on a large computer

DICOM

Set a rules or protocols that allows imaging systems to share information on a network

Dynamic Range (Signal)

Supporting extent to which a signal can vary and still be accurately measured

Compression (Dynamic Range)

Reduce the dynamic range of a signal without introducing errors

Number of choices

An alternate description of dynamic range

High contrast

Images that display few shades of gray

Low contrast

Images that displayed many shades of grey

Harmonic Imaging

Creation of an image from sand reflections at twice the frequency of the transmitting sound

Fundamental frequency

Transmitted frequency

Harmonic Frequency

Twice the fundamental frequency

Fundamental Image

Image created by processing reflections that have the same frequency as a transmitted sound

Harmonic Image

Image created by processing reflections that are twice the fundamental frequency

Linear Behavior

Proportional or symmetrical

Nonlinear Behavior

Irregular or disproportionate

Tissue Harmonics

Created by non–linear behavior during transmission in tissue

Pulse Inversion Harmonics

Designed the utilize harmonic reflections, which are distortion free while eliminating distorted fundamental reflections

Power Modulation Harmonics

Designed to augment harmonic reflections, which contain less distortion while eliminating distorted fundamental reflections

Microbubbles

Injected in the circulation or ingested

Resonance

Non–linear behavior where microbes expand more during rare faction then they shrink during compression

Mechanical Index (Contrast)

Amount of contrast, harmonics produce may be estimated by a number

Peak Rarefaction Pressure

Maximum negative pressure in a sound wave

Artifact

Error in an image

Hyperechoic

Portion of an image that are brighter than surrounding tissue

Hypoechoic

Portions of an image that are not as bright as surrounding tissue or appear less bright

Anechoic

Extreme form of hypoechoic, meaning entirely without echoes

Isoechoic

Describe structures with equal echo brightness

Homogeneous

Portion of tissue or an image that has similar echo characteristics throughout

Heterogeneous

Portion of tissues or an image that has different echo characteristics throughout

Comet Tail

Created one closely space reverberations merge

Ring Down

Also known as comet tail

Shadow

Appears as a hypoechoic or anechoic region, extending downward from a highly attenuating structure

High attenuation

Deep reflecting surfaces do not appear on the image

Edge Shadow

Hypoechoic region, extending down from the edge of a curved reflector

Curved reflector

Diverse or bends the same beam away from the edge, creating an edge shadow artifact

Refraction (Edge Shadow)

Also known as edge shadow

Enhancement

Hyperechoic region beneath tissue with abnormally low attenuation

Low attenuation

Less weakening of the sound beam Diane surrounding tissues, resulting in an area of enhancement beneath the structure