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203 Cards in this Set
- Front
- Back
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A diplay presentation of echo amplitude versus depth
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A-mode
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Conversion of sound to heat
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Absorption
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Having to do with sound
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Acoustic
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Pressure,density and particle vibration; sound wave quantities that vary in space and time
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Acoustic Variables
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As low as reasonably achievable
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ALARA
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improper doppler shift info from a pulsed wave doppler or color doppler when the true doppler shift exceeds one half the PRF
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Aliasing
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Process by which small voltages are increased to larger ones
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Amplification
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Device that accomplishes amplification
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Amplifier
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Maxium variation of an acoustic variable or voltage
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Amplitude
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Related to a procedure or system in which data are represented by proportional,continuously variable, physical quantities
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Analog
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device that converts voltage amplitude to a number.ADC
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Analog to Digital converter
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echo-free
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Anechoic
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Size of a transducer element or group of elements
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Aperature
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Nonuniform driving of elements in an array to reduce grating lobes
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Adopization
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A transducer assembly containing several PZT elements
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Array
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Decrease in amplitude and intensity with distance as a wave travels through a medium
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Attenuation
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Attenuation per cm of wave travel
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Attenuation Coefficient
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A rapid technique, used in most color doppler-shift frequency
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Autocorrelation
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In the direction of the transducer axis
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Axial
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The minimum reflector seperation along the path that is required to produce seperate echos
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Axial resolution
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Mode of operation in which the display presents a spot approriate brightness for each echo recieved by the transducer
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B-mode
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A b-mode image that represents an anatomic cross section through the scanning plan
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B scan
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Sound scattered back in the direction from which it origanally came
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Backscatter
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Range of frequencies contained in an ultrasound pulse;range of frequencies within which a material,device,or system can operate
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Bandwidth
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Movement of the zero doppler-shift frequency or zero flow speed line up or down on a spectral display
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Baseline shift
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Region containing continuous wave sound;region through which a sound pulse prpagates
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Beam
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Cross-sectional area of a sound beam
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Beam area
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Part of an instrument that accompishes electronic beam scanning, apodization,steering,focusing,and aperture with arrays
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Beam former
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Pressure reduction in a region of high flow speed
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Bernoulli effect
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Indication doppler instruments capable of distinguishing bewteen positive and negative doppler shifts
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Bidirectional
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Having 2 possible states
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Bistable
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Binary digit
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Bit
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A diplay device that produced an image by scanning an electron beam over a phosphorcoated screen CRT
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Cathode ray tube
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Production and dynamics of bubbles in sound
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Cavitation
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Single one or two way path for tranmitting electric signals, in distinction from other parrallel paths
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Channel
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Sequentail display of all framed stored in memory at a controlled frame rate
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Cine loop
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Noise in the doppler signal that generally is caused by high-amplitude,doppler-shifted echos from the heart or vessel wall
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Clutter
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Sophisticated form of transmission in which the driving voltage pulses have intrapulse variation in amplitude, frequency,and/or pulse
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Coded excitation
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Presentation of 2 dimensional, realtime doppler shift info superimposed on a real-time,gray-scale, anatomic cross sectional image. Flow toward and away from transducer are presented as different colors on a display
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Color Doppler display
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Series of closely spaced reverberation echos
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Comet tail
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Equalization of recieved echo amplitude differences caused by differnet attenuation for different reflector depths;also called depth gain compensation or TGC
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Compensation
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Distensibility; nonrigid strechability of vessels
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Compliance
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Combination of a PZT ceramic and a nonPZT polmer
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Composite
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Reduction in differences between small and large amplitudes. Region of high density and pressure in a compressional wave
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Compression
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Combination of positive or negative pressure
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Constructive interference
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A wave in which cycles repeat indefinitely;not pulsed
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Continuous Wave
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A doppler device or procedure that uses continuous wave ultrasound
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Continuous Wave Doppler
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A suspension of bubbles or particles introduced into circulation to enhance the contrast between anatomic structures,thereby improving their imaging
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Contrast agent
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Ability of a gray-scale display to distinguish bewteen echos of slightly different intensities
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Contrast resolution
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Curved linear array
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Convex array
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Gel used to provide a good sound path bewteen a transducer and the skinby elininating the air between the 2
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Coupling medium
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Reynolds number above which trubulence occurs
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Critical reynolds number
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element
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Crystal
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Temperature at which an element material loses its piezoelectric properties
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Curie point
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One complete variation of an acoutic variable
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Cycle
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Material attached to the rear face of the transducer element to reduce pulse duration; the process of pulse duration reduction
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Damping
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Detection
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Demodulation
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Unit of power or intensity ratio; the number of decibels is 10 times the logarithm of the power or intensity ratio
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Decibal-dB
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Mass divided by Volume
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Density
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Combination of positive and negative pressures
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Destructive interference
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Ability to image fine detail and to distinguish closely spaced reflectors
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Detail resolution
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Conversion of voltage pulses from radio frequency to video form
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Demodulation
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Related to a procedure or system in which data are represented by numeric digits
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Digital
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Device that converts a number to a proportional voltage amplitude
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Digital to Analog converter
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Device that presents a visual image derived from voltages recieved from an image processor
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Display
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Flow that cannot be described by straight, parrallel stremlines
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Disturbed flow
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The angle bewteen the sound beam and the flow direction
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Doppler angle
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Change in frequency caused by motion of reflectors
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Doppler effect
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Mathematical description of the relationship bewteen doppler shift,frequency,doppler angle prop. speed, and reflector speed
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Doppler equation
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Color doppler display in which colors are assigned according to the strength of doppler shift echos
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Doppler-power display
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Reflected frequency minus incident frequency; a change in frequency that occurs as a result of motion
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Doppler shift
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Range of frequencies present in doppler-shifted echos
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Doppler specturm
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Ultrasound instrument that combines gray-scale sonography with pulsed doppler and possibly, continuous wave doppler
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Duplex instrument
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Fraction of time that pulsed ultrasound is on
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Duty factor
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Aperature that increases with increasing focal length
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Dynamic aperature
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continuously variable reception focusing that follows the increasing depth of the transmitted pulse as it travels
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Dynamic focusing
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Ratio of largest to smallest power that a system can handle; ratio of the largest to smallest intensity of echoes
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Dynamic range
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Regions of circular flow patterns present in turbulence
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Eddies
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The piesoelectric component of a transducer assembly
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Element
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Detail resolution in the direction perpindicular to the scan plane. It is equal to the section thickness and the source section thickness artifact
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Elevational resolution
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Capability of doing work
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Energy
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Increase in echo amplitude from reflectors that lie behind a weakly attenuating structure
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Enhancement
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Region of a sound beam in which the beam diameter increases as the distance from the transducer increases
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Far zone/Far field
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Digital computer implementaion of the fourier transform
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Fast Fourier Transform
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An electric circuit that passes frequencies within a certain range
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Filter
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A back-lighted rectangle matrix of thousands of liquid crystal display elements
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Flat-panal diaplay
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Distance from a focused transducer to the center of a focal region or to the location fo the spatial peak intensity
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Focal Length
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Region of minium beam diameter and area
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Focal region
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Length of the focal region
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Focal Zone
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The concentration of the sound beam into a smaller beam area than would exist otherwise
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Focus
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Bandwidth divided by operating frequency
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Fractional Bandwidth
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Single image produced by one complete scan of the sound beam
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Frame
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Number of frames of echo information stored each second
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Frame rate
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Far zone
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Fraunhofer Zone
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COnstant display of one of the frames in memory
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Freeze-frame
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Number of cycles per second
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Frequency
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Range of doppler-dhift frequencies present in the returning echos
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Frequency spectrum
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Near zone
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Fresnel zone
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Primary frequency in a collection of frequencies that can include odd and even harmonics and subharmonics
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Fundamental frequency
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Ratio of amplifier output to input electric power
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Gain
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Device that allows only echos from a selected depth to pass
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Gate
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Additional weaker beams of sound traveling out in directions different from the primary beam as a result of the multielement structure of transducer arrays
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Grating Lobes
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Range of brightness between white and black
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Gray scale
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Frequencies that are even and odd multiples of another, commonly called the fundamental or operating frequency
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Harmonics
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Unit of frequency, one cycle per second; unit of pulse repition frequency, one pulse per second
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Hertz
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Small transducer element mounted on the end of a narrow tube; a piesoelectric membrane with small metallic electrode
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Hydrophone
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Having revatively weak echos.
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Hypoechoic
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Part of the image processor where echo information is stored in image format
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Image memory
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Electronic device that manipulated and prepares images for visual presentation
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Image processor
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Density multiplied by the sound propagation speed
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Impedance
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Angle between incident sound direction and a line perpindicular to the boundry of a medium
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Incidence angle
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Resistance to acceleration
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Inertia
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Power divided by area
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Intensity
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Reflected intensity divided by incident intensity; the fraction of incident intensity reflected
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Intensity reflection coefficient
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Transmitted intensity divided by incident intensity; the fraction of incident intensity transmitted into the second medium
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Intensity tranmitted coeffcient
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Combinations of positive and or negative pressures
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Interference
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One thousand hertz
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Kilohertz
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Flow in which fluid layers slide over each other in a smooth, orderly manner, with no mixing between layers
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Laminar flow
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Minimum reflector seperation perpindicular to the sound path that is required ti produce seperate echos
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Lateral resolution
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Curved material that focuses a sound or light beam
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Lens
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Array made of rectangular elements arranged in a line
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Linear Array
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Linear array operated by applying voltage pulses to all elements, but with small time differences to direct ultrasound pulses out in various directions
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Linear phased array
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Linear array operated by applying voltage pulses to groups of elements sequentially
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Lenear sequenced array
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Wave in which the particle motion is parrallel to the direction of the wave travel
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Longitudinal wave
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B mode presentation of changing reflector position versus time
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M-mode
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Material attached to the front face of a transducer element to reduce the reflection at the transducer surface
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Matching layer
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Indicator of nonthermal mechanism activity; equal to the peak rarefactional pressure divided by the aqual root of the center frequency of the pulse bandwidth
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Mechanical index
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Artifactual gray-scale,color flow, or doppler signal appearing on the oppisite side of a strong reflector
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Mirror image
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Several reflections produced by a pulse encountering a pair of reflectors;reverberation
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Multiple reflection
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Narrowing of a sound beam that occurs with an unfocused flat transducer element
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Natural focus
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Region of a sound beam in which the beam diameter decreased as the distance from the transducer increases
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Near zone
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Sound propagation in which the propagation speed depends on pressure causing the wave shape to change and harmonics to be generated
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Nonlinear propagation
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Doppler-shift frequency above which alsising occurs; one half the PRF
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Nyquist limit
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Sound direction that is not perpindicular to media boundries
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Oblique incidence
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Laminar flow with a profile in the shape of a parabola
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Parabolic flow
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Imaging depth
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Penetration
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Time per cycle
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Period
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Sound direction that is perpindicular to the boundry between media
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Perpindicular incidence
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Averaging sequential frames together
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Persistance
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Array that steers and focuses the beam electronically
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Phased array
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Linear sequeced array with phased focusing added; linear sequenced array with phased steering of pulses to produce a parallelogram-shaped display
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Phased leanear array
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The system tht provides means for electronically communicating images to workstations
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PACS
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Conversion of pressure to electric voltage
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Piezoelectricity
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Picture element; unit which imaging information is divided for storage and display in a digital instrument
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Pixel
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Flow with all fluid portions traveling with the same flow speed and direction
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Plug flow
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Mathematical description of dependence of volume flow rate on pressure, vessel length and radius, and fluid viscosity
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Poiseuille's Equation
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Image processing done after memory
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Postprocessing
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Force divided by the area in a fluid
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Pressure
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Gray-scale echo strength below which color doppler information is shown preferentailly on a display
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Priority
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Speed with which a wave moves through a medium
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Propagation speed
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Flow that accelerated and decelerates with each cardiac cycle
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Pulsatile flow
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Interval of time from beginning to end of a pulse
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Pulse duration
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Number of pulses per second;
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Pulse repetition frequency
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Interval of time from the beginning of one pulse to the beginning of the next
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Pulse repetition Period
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Doppler device or procedure that uses pulsed wave ultrasound
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Pulsed doppler
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Ultrasound produced in pulsed form by applying electric pulses or voltages of one or a few cycles to the transducer
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Pulsed Ultrasound
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Ultrasound imaging in which pulses are reflected and used to produce a display
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pulse-echo technique
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Force exerted by a sound beam on an absorber or a reflector
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Radiation force
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Artifact produced when echoes are placed too close to the transducer because a second pulse was emitted before they were recieved
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Range ambiguity
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Relationship between round-trip pulse time,propagation speed, and distance to a reflector
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Range equation
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Region of low density and pressure in a compressional wave
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Rarefaction
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Display that, with a sufficient frame rate, appears to image moving structures or a changing scan plane continuously
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Real-time display
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Portion of sound returned from a media boundry;echo
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Reflection
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Angle between the reflected sound direction and line perpindicular to the media boundry
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Reflection angle
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Media boundry that produces a reflection;reflecting surface
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Reflector
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Change of sound direction on passing from one medium to another
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Refraction
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Pressure difference divided by volume flow rate for steady flow
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Resistance flow
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Ability to distinghish echoes in terms of space,time or strength
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Resolution
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Multiple reflection
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Reverberation
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Number that depends on flow speed and viscosity to perdict the onset of turbulence
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Reynolds number
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Artifact resulting from a continuous stream of sound emanating from an anatomic site
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Ring-down artifact
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Anatomic region from which pulsed doppler echoes are accepted
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Sample volume
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Electric device that reformats echo data into an image for aimage processing, storage and display
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Scan converter
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A line produced on a display that represents ultrasonic echoes returning from the body
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Scan lines
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An object that scatters sound because of its small size or its surface roughness
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Scatterer
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Diffusion or redirection of sound in several directions upon encountering a particle suspension or a rough surface
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Scattering
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Thickness of the scanned tissue volume perpindicular to the scan plane
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SLice thickness
Section thickness |
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Ability of an imaging system to detect weak echoes
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Sensitivity
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Reduction in echo amplitudefrom reflectors that lie behind a strongly reflecting or attenuating structure
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Shadowing
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Weaker beams of sound traveling out from a single element in direction from that of theprimary beam
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Side lobes
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Electronic device that manipulates electric signals in preparation for appropiate presentation of information contained in them
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Signal processor
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Traveling wave of acoustic variables
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Sound
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Region of a medium that contains virtually all of the sound produced by a transducer
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Sound beam
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Averaging if frames that view anatomy from different angles
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Spatial compounding
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Length of space over which a pulse occurs
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Spatial pulse length
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Granular appearance of images and spectral displays that is caused by the interference of echoes from the distribution of scatterers in tissue
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Speckle
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Seperation of frequencies in a doppler signal for display as a doppler spectrum; the application of the fourier transform to determine the frequency compomnents present in a doppler signal
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Spectral analysis
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Wideing of the doppler-shift spectrum; that is, the increase in the range of doppler shift frequencies present that occurs because of a broadened range of flow velocities encountered by the sound beam
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Spectral broadening
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Reflection from a large,flat smooth boundry
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Specular reflection
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Propagation speed that is different from the assumed value
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Speed error
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Narrowing of vessel
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Stenosis
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Property of a medium; applied pressure divided by the practional volume change produced by the pressure
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Stiffness
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Amplitude or intensity
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Strength
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Ability to distinguish closely spaced events in time
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Temporal resolution
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Indicator of thermal mechanism activity; a value equal to transducer acoustic output power divided by the estimated power required to raise tissue temperature
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Thermal index
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Equalization of echo amplitude differences caused by different reflector depths
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Time gain compensation
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Device that converts energy from one form to another
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Transducer
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Angle between the transmittted sound direction and a line perpendicular to the media boundry
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Transmission angle
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Sound having a frequency greater than 20kHz
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Ultrasound
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Linear sequenced array that emits pulses from different starting points and different directions
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vector array
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Resistance of a fluid to flow
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Viscosity
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Electric filter that passes frequencies above a set level and elininates strong, low-frequency doppler shifts from pulsing heart or vessel walls
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Wall filter
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Length of space over which a cycle occurs
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Wavelength
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