Physics Final Kremkau Vocabulary

Question 1

Mode of operation in which the display presents echo amplitude versus depth (used in opthamology)

Answer 1

A mode

Question 2

conversion of sound to heat

Answer 2

absorption

Question 3

having to do with sound

Answer 3

acoustic

Question 4

pressure, density, and particle vibration; sound wave quantities that vary in space and time

Answer 4

acoustic variables

Question 5

as low as reasonably achievable. The principle that is prudent to obtain diagnostic information with the least amount possible of energy exposure to the patient

Answer 5

ALARA

Question 6

Improper doppler-shift information from a pulsed spectral-Doppler or color-Doppler instrument when the true Doppler shift exceeds one-half the pulse repetition frequency

Answer 6

aliasing

Question 7

the process by which small voltages are increased to larger ones

Answer 7

amplification

Question 8

a device that accomplishes amplification

Answer 8

amplifier

Question 9

maximum variation of an acoustic variable or voltage

Answer 9

amplitude

Question 10

related to a procedure or system in which data are represented by proportional, continuously variable, physical quantities

Answer 10

analog

Question 11

a device that converts voltage amplitude to a number. Abbreviated ADC

Answer 11

analog to digital converter

Question 12

echo free

Answer 12

anechoic

Question 13

size of a transducer element (for a single element transducer) or group of elements (for an array)

Answer 13

aperture

Question 14

nonuniform driving of elements in an array to reduce grating lobes

Answer 14

apodization

Question 15

a transducer assembly containing several piezoelectric elements

Answer 15

array

Question 16

decrease in amplitude and intensity with distance as a wave travels through a medium

Answer 16

attenuation

Question 17

attenuation per centimeter of wave travel

Answer 17

attenuation coefficient

Question 18

A rapid technique, used in most Color-Doppler instruments, to obtain mean Doppler-shift frequency

Answer 18

autocorrelation

Question 19

in the direction of the transducer axis (sound travel direction)

Answer 19

axial

Question 20

the minimum reflector separation along the sound path that is required to produce separate echoes

Answer 20

axial resolution

Question 21

Mode of operation in which the display presents a spot of appropriate brightness for each echo received by the transducer

Answer 21

B mode

Question 22

a B-mode image that represents an anatomic cross section through the scanning plane

Answer 22

B scan

Question 23

sound scattered back in the direction from which it originally came

Answer 23

backscatter

Question 24

range of frequencies contained in an ultrasound pulse; range of frequencies within which a material, device, or system can operate

Answer 24

bandwidth

Question 25

movement of the zero Doppler-shift frequency or zero flow speed line up or down on a spectral display

Answer 25

baseline shift

Question 26

region containing continuous wave sound; region through which a sound pulse propagates

Answer 26

beam

Question 27

the part of an instrument that accomplishes electronic beam scanning, apodization, steering, focusing, and aperture with arrays

Answer 27

beam former

Question 28

pressure reduction in a region of high-flow speed

Answer 28

Bernoulli effect

Question 29

indicating Doppler instruments capable of distinguishing between positive and negative Doppler shifts (approaching and receding flow)

Answer 29

bidirectional

Question 30

having two possible states

Answer 30

bistable

Question 31

binary digit; one or zero

Answer 31

bit

Question 32

production and dynamics of bubbles in sound

Answer 32

cavitation

Question 33

a single one- or two-way path for transmitting electric signals, in distinction from other parellel paths; an independent transmission delay line and transducer element path; an independent reception transducer element, amplifier, analong-to-digital converter, and delay line path

Answer 33

channel

Question 34

sequential display of all the frames stored in memory at a controllable frame rate

Answer 34

cine loop

Question 35

noise in the Doppler signal that generally is caused by high-amplitude, Doppler-shifted echoes from the heart or vessel walls

Answer 35

clutter

Question 36

capacative micromachined ultrasonic transducer that contains miniature elements that are comprised of two electrically conducting layers facing each other; one of which is fixed and the other of which is a flexible membrane

Answer 36

CMUT

Question 37

a sophisticated form of transmission in which the driving voltage pulses have intrapulse variations in amplitude, frequency, and/or phase.

Answer 37

coded excitation

Question 38

the presentation of two-dimensional, real-time Doppler-shift information in color superimposed on a real-time, gray-scale, anatomic, cross-sectional image. Flow directions toward and away from the transducer are presented as different colors on the display

Answer 38

color-Doppler display

Question 39

a series of closely spaced reverberation echoes

Answer 39

comet tail

Question 40

equalization of received echo amplitude differences caused by different attenuations for different reflector depths; also called depth gain compensation or time gain compensation

Answer 40

compensation

Question 41

distensibility; nonrigid stretchability of vessels

Answer 41

compliance

Question 42

combination of a piezoelectric ceramic and a nonpiezoelectric polymer

Answer 42

composite

Question 43

reduction in differences between small and large amplitudes. Region of high density and pressure in a compressional wave

Answer 43

compression

Question 44

combination of positive or negative pressures

Answer 44

constructive interference

Question 45

a wave in which cycles repeat indefinitely; not pulsed. Abbreviated CW

Answer 45

continuous wave

Question 46

A Doppler device or procedure that uses continuous wave ultrasound

Answer 46

continuous wave doppler

Question 47

a suspension of bubbles or particles introduced into circulation to enhance the contrast between anatomic structures, thereby improving their imaging

Answer 47

contrast agen

Question 48

ability of a gray-scale display to distinguish between echoes of slightly different intensities

Answer 48

contrast resolution

Question 49

curved linear array

Answer 49

convex array

Question 50

the cosine of angle A is the length of side b divided by the length of side c. abbreviated cos

Answer 50

cosine

Question 51

a gel used to provide a good sound path between a transducer and the skin by eliminating the air between the two

Answer 51

coupling medium

Question 52

the Reynolds number above which turbulence occurs

Answer 52

critical Reynolds number

Question 53

leakage of strong signals in one direction channel of a Doppler receiver into the other channel; can produce the spectral-Doppler mirror-image artifact

Answer 53

cross-talk

Question 54

element

Answer 54

crystal

Question 55

temperature at which an element material loses its piezoelectric properties

Answer 55

curie point

Question 56

one complete variation of an acoustic variable

Answer 56

cycle

Question 57

material attached to the rear face of a transducer element to reduce pulse duration; the process of pulse duration reduction

Answer 57

damping

Question 58

unit of power or intensity ratio; the number of decibels is 10 times the logarithm (to the base of 10) of the power or intensity ratio. Abbreviated dB.

Answer 58

decibel

Question 59

detection

Answer 59

demodulation

Question 60

mass divided by volume

Answer 60

density

Question 61

combination of positiver and negative pressures

Answer 61

destructive interference

Question 62

the ability to image fine detail and to distinguish closely spaced reflectors

Answer 62

detail resolution

Question 63

conversion of voltage pulses from radio frequency to video form

Answer 63

detection

Question 64

related to a procedure or system in which data are represented by numeric digits

Answer 64

digital

Question 65

a device that converts a number to a proportional voltage amplitude. Abbreviated DAC.

Answer 65

digital-to-analog converter

Question 66

a thin, flat, circular object

Answer 66

disk

Question 67

a device that presents a visual image derived from voltages received from an image processor

Answer 67

display

Question 68

flow that cannot be described by straight, parallel streamlines

Answer 68

disturbed flow

Question 69

the angle between the sound beam and the flow direction

Answer 69

Doppler angle

Question 70

a change in frequency caused by reflector motion

Answer 70

Doppler effect

Question 71

the mathematical description of the relationship between the Doppler shift, frequency, Doppler angle, propagation speed, and reflector speed

Answer 71

Doppler equation

Question 72

color-doppler display in which colors are assigned according to the strength (amplitude, power, intensity, energy) of the Doppler-shifted echoes

Answer 72

Doppler-power display

Question 73

reflected frequency minus incident frequency; the change in frequency caused by motion

Answer 73

Doppler shift

Question 74

the range of frequencies present in Doppler-shifted echoes

Answer 74

Doppler spectrum

Question 75

an ultrasound instrument that combines gray-scale sonography with pulsed Doppler and, possibly, continuous wave Doppler

Answer 75

duplex instrument

Question 76

fraction of time that pulsed ultrasound is on

Answer 76

duty factor

Question 77

aperture that increases with increasing focal length (to maintain constant focal width)

Answer 77

dynamic aperture

Question 78

continuously variable reception focusing that follows the increasing depth of the transmitted pulse as it travels

Answer 78

dynamic focusing

Question 79

ratio (in decibels) of largest to smallest power that a system can handle; ratio of the largest to smallest intensity of echoes encountered

Answer 79

dynamic range

Question 80

reflection

Answer 80

echo

Question 81

regions of circular flow patterns present in turbulence

Answer 81

eddies

Question 82

imaging tissue stiffness by tracking movement under mechanical stress

Answer 82

elastography

Question 83

the piezoelectric component of a transducer assembly

Answer 83

element

Question 84

the detail resolution in the direction perpendicular to the scan plane. It is equal to the section thickness and is the source of section thickness artifact

Answer 84

elevational resolution

Question 85

capability of doing work

Answer 85

energy

Question 86

increase in echo amplitude from reflectors that lie behind a weakly attenuating structure

Answer 86

enhancement

Question 87

number of pulses used to generate one color-Doppler image scan line

Answer 87

ensemble length

Question 88

the region of a sound beam in which the beam diameter increases as the distance from the transducer increases

Answer 88

far zone

Question 89

digital computer implementation of the Fourier transform

Answer 89

fast Fourier transform

Question 90

an electric circuit that passes frequencies within a defined range

Answer 90

filter

Question 91

a backlighted rectangular matrix of thousands of liquid-crystal display elements

Answer 91

flat-panel display

Question 92

to move in a stream; volume flow rate

Answer 92

flow

Question 93

a material that flows and conforms to the shape of its container;a gas or liquid

Answer 93

fluid

Question 94

distance from a focused transducer to the center of a focal region or to the location of the spatial peak intensity

Answer 94

focal length

Question 95

region of minimum beam diameter and area

Answer 95

focal region

Question 96

length of the focal region

Answer 96

focal zone

Question 97

the concentration of the sound beam into a smaller beam area than would exist otherwise

Answer 97

focus

Question 98

a mathematical technique for obtaining a Doppler frequency spectrum

Answer 98

Fourier transform

Question 99

bandwidth divided by operating frequency

Answer 99

fractional bandwidth

Question 100

a single image produced by one complete scan of the sound bream

Answer 100

frame

Question 101

number of frames of echo information stored each second

Answer 101

frame rate

Question 102

far zone

Answer 102

Fraunhofer zone

Question 103

constant display of one of the frames in memory

Answer 103

freeze

Question 104

number of cycles per second

Answer 104

frequency

Question 105

the range of Doppler-shift frequencies present in the returning echoes

Answer 105

frequency spectrum

Question 106

near zone

Answer 106

fresnel zone

Question 107

the primary frequency in a collection of frequencies that can include odd and even harmonics and subharmonics

Answer 107

fundamental frequency

Question 108

ratio (in decibels) of amplifier output to input electric power

Answer 108

gain

Question 109

a device that allows only echoes from a selected depth (arrival time) to pass

Answer 109

gate

Question 110

an electronic device that rapidly performs calculations to accelerate the creation of images

Answer 110

graphics processing unit (GPU)

Question 111

additional weaker beams of sound traveling out in directions different from the primary beam as a result of the multielement structure of transducer arrays

Answer 111

grating lobes

Question 112

range of brightness (gray levels) between white and black

Answer 112

gray scale

Question 113

frequencies that are even and odd multiples of another, commonly called fundamental or operating frequency

Answer 113

harmonics

Question 114

unit of frequency, one cycle per second; unit of pulse repetition frequency, one pulse per second

Answer 114

hertz

Question 115

the color perceived based on the frequency of light

Answer 115

hue

Question 116

a small transducer element mounted on the end of a narrow tube; a piezoelectric membrane with small metallic electrodes

Answer 116

hydrophone

Question 117

having relatively weak echoes. Opposite of hyperechoic (having relatively strong echoes)

Answer 117

hypoechoic

Question 118

a reproduction, representation, or imitation of the physical form of a person or a thing

Answer 118

image

Question 119

the portion of a system operating on Principle 2 that acquires the echo information from the signal processor, performs the retrospective, virtual-beam computations and sends the results to the display.

Answer 119

image former

Question 120

the part of the image processor where echo information is stored in image format

Answer 120

image memory

Question 121

an electronic device that manipulates and prepares images for visual presentation

Answer 121

image processor

Question 122

density multiplied by the sound propagation speed

Answer 122

impedance

Question 123

angle between incident sound direction and a line perpendicular to the boundary of a medium

Answer 123

incidence angle

Question 124

resistance to acceleration

Answer 124

inertia

Question 125

an electronic system that electrically drives a transducer, receives returning echoes, and presents them on a visual display as an anatomic image, Doppler spectrum, or color-Doppler presentation

Answer 125

instrument

Question 126

power divided by area

Answer 126

intensity

Question 127

reflected intensity divided by incident intensity; the fraction of incident intensity transmitted into the second medium

Answer 127

intensity reflection coefficient

Question 128

transmitted intensity divided by incident intensity; the fraction of incident intensity transmitted into the second medium

Answer 128

intensity transmission coefficient

Question 129

combinations of positive and/or negative pressures

Answer 129

interference

Question 130

one thousand hertz

Answer 130

kilohertz

Question 131

flow in which fluid layers slide over each other in a smooth, orderly manner, with no mixing between layers

Answer 131

laminar flow

Question 132

perpendicular to the direction of sound travel

Answer 132

lateral

Question 133

gain controls that enable different gain values to be applied laterally across an image to compensate for differing attenuation values in different anatomic regions

Answer 133

lateral gain control

Question 134

minimum reflector separation perpendicular to the sound path that is required to produce separate echoes

Answer 134

lateral resolution

Question 135

a ceramic piezoelectric material

Answer 135

lead zirconate titanate

Question 136

a curved material that focuses a sound or light beam

Answer 136

lens

Question 137

adjectival form of line

Answer 137

linear

Question 138

array made of rectangular elements arranged in a straight line

Answer 138

linear array

Question 139

an anatomic image presented in a rectangular format

Answer 139

linear image

Question 140

linear array operated by applying voltage pulses to all elements, but with small time differences (phasing) to direct ultrasound pulses out in various directions

Answer 140

linear phased array

Question 141

linear array operated by applying voltage pulses to groups of elements sequentially

Answer 141

linear sequenced array

Question 142

wave in which the particle motion is parellel tot he direction of wave travel (compressional wave)

Answer 142

longitudinal wave

Question 143

brightness of a presented hue and saturation

Answer 143

luminance

Question 144

A B-mode presentation of changing reflector position (motion) versus time (used in echocardiography)

Answer 144

M mode

Question 145

measure of the resistance of an object to acceleration

Answer 145

mass

Question 146

material attached to the front face of a transducer element to reduce the reflections at the transducer surface

Answer 146

matching layer

Question 147

an indicator of nonthermal mechanism activity; equal to the peak rarefactional pressure divided by the square root of the center frequency of the pulse bandwidth

Answer 147

mechanical index

Question 148

material through which a wave travels

Answer 148

medium

Question 149

one million hertz

Answer 149

megahertz

Question 150

an artifactual gray-scale, color flow, or Doppler signal appearing on the opposite side of a strong reflector

Answer 150

mirror image

Question 151

several reflections produced by a pulse encountering a pair of reflectors; reverberation

Answer 151

multiple reflection

Question 152

the narrowing of a sound beam that occurs with an unfocused flat transducer element

Answer 152

natural focus

Question 153

the region of a sound beam in which the beam diameter decreases as the distance from the transducer increases

Answer 153

near zone

Question 154

sound propagation in which the propagation speed depends on pressure causing the wave shape to change and harmonics to be generated

Answer 154

nonlinear propagation

Question 155

the Doppler-shift frequency above which aliasing occurs; one-half of the pulse repetition frequency

Answer 155

Nyquist limit

Question 156

sound direction that is not perpendicular to media boundaries

Answer 156

oblique incidence

Question 157

preferred frequency of operation of a transducer

Answer 157

operating frequency

Question 158

in operating principle 1, positional information is determined by knowledge of the direction of the pulse when it enters the patient and by measurment of the time it takes for each echo to return to the transducer. The proper location to present the echo can then be determined from a starting point on the display (usually at the top). With knowledge of the sound speed, the instrument uses the echo arrival time to determine the depth of the structure that produced that echo

Answer 158

Operating Principle 1

Question 159

Operating principle 2 sends several pulses of ultrasound through the cross section of anatomy to be imaged but does not produce a one-for-one correspondence of pulse and displayed scan line. Instead, all the echo information from throughout the anatomic cross section is collected, and then massive computational processes determine the location and strength of each echo produced at each location in the anatomy. This approach is used in recent, sophisticated instruments and produces improved quality compared with Principle 1.

Answer 159

Operating Principle 2

Question 160

the extension of the field of view beyond the normal limits of a transducer scan plane

Answer 160

panoramic imaging

Question 161

laminar flow with a profile in the shape of a parabola

Answer 161

parabolic flow

Question 162

imaging depth

Answer 162

penetration

Question 163

time per cycle

Answer 163

period

Question 164

geometrically related by 90 degrees

Answer 164

perpendicular

Question 165

sound direction that is perpendicular to the boundary between media

Answer 165

perpendicular incidence

Question 166

averaging sequential frames together

Answer 166

persistence

Question 167

tissue-equivalent device that has characteristics that are representative of tissues

Answer 167

phantom

Question 168

a description of progress through a cycle; one full cycle is divided into 360 degrees of phase

Answer 168

phase

Question 169

two signals differing by one-fourth of a cycle

Answer 169

phase quadrature

Question 170

an array that steers and focuses the beam electronically (with short time delays)

Answer 170

phased array

Question 171

linear sequenced array with phased focusing added; linear sequenced array with phased steering of pulses to produce a parallelogram-shaped display

Answer 171

phased linear array

Question 172

the system provides means for electronically communicating images and associated information to workstations and devices external to the sonographic instrument, the examining room, and even the building in whcih the scanning in done

Answer 172

picture archiving and communications system

Question 173

conversion of pressure to electric voltage

Answer 173

piezoelectricity

Question 174

picture element; the unit into which imaging information is divided for storage and display in a digital instrument

Answer 174

pixel

Question 175

flow with all fluid portions traveling with the same flow speed and direction

Answer 175

plug flow

Question 176

unit of viscosity

Answer 176

poise

Question 177

the mathematical description of the dependence of volume flow rate on pressure, vessel length and radius, and fluid viscosity

Answer 177

Poiseuille equation

Question 178

imaging processing done after storage in the memory

Answer 178

postprocessing

Question 179

rate at which work is done; rate at which energy is transferred

Answer 179

power

Question 180

signal and image processing accomplished before storage in the memory

Answer 180

preprocessing

Question 181

force divided by the area in a fluid

Answer 181

pressure

Question 182

the gray-scale echo strength below which color-Doppler information is shown preferentially on a display

Answer 182

priority

Question 183

transducer assembly

Answer 183

probe

Question 184

progession or travel

Answer 184

propagation

Question 185

speed at which a wave moves through a medium

Answer 185

propagation speed

Question 186

flow that accelerates and decelerates with each cardiac cycle

Answer 186

pulsatile flow

Question 187

a description of the relationship between peak systolic and end diastolic flow speeds of Doppler shifts

Answer 187

pulsatility index

Question 188

a brief excursion of a quantity from its normal value; a few cycles

Answer 188

pulse

Question 189

interval of time from beginning to the end of a pulse

Answer 189

pulse duration

Question 190

number of pulses per second

Answer 190

pulse-repetition frequency

Question 191

interval of time from the beginning of one pulse to the beginning of the next

Answer 191

pulse repetition period

Question 192

a Doppler device or procedure that uses pulsed-wave ultrasound

Answer 192

pulsed Doppler

Question 193

ultrasound produced in pulsed form by applying electric pulses or voltages of one or a few cycles to the transducer

Answer 193

pulsed ultrasound

Question 194

ultrasound imaging in which pulses are reflected and used to produce a display

Answer 194

pulse-echo technique

Question 195

the force exerted by a sound beam on an absorber or a reflector

Answer 195

radiation force

Question 196

voltages representing echoes in cyclic form

Answer 196

radio frequency

Question 197

an artifact produced when echoes are placed too close to the transducer because a second pulse was emitted before they were received from the first pulse

Answer 197

range ambiguity

Question 198

relationship between round-trip pulse travel time, propagation speed, and distance to a reflector

Answer 198

range equation

Question 199

selection of the depth from which echoes are accepted based on echo arrival time

Answer 199

range gating

Question 200

region of low density and pressure in a compressional wave

Answer 200

rarefaction

Question 201

unit of impedance

Answer 201

rayl

Question 202

imaging with a rapid frame sequence display

Answer 202

real time

Question 203

a display that, with a sufficient frame rate, appears to image moving structures or a changing scan plane continuously

Answer 203

real-time display

Question 204

portion of sound returned from a media boundary; echo

Answer 204

reflection

Question 205

angle between the reflected sound direction and a line perpendicular to the media boundary

Answer 205

reflection angle

Question 206

media boundary that produced a reflection; reflecting surface

Answer 206

reflector

Question 207

change of sound direction on passing from one medium to another

Answer 207

refraction

Question 208

the number of times each second that information is sent from the image memory to the display. The number of times per second that a computer monitor redraws the information found in the memory

Answer 208

refresh rate

Question 209

pressure difference divided by volume flow rate for steady flow

Answer 209

resistance

Question 210

the ability to distinguish echoes in terms of space, time, or strength

Answer 210

resolution

Question 211

the condition in which a driven mechanical vibration is of a frequency similar to a natural vibration frequency of the structure, yielding maximum response

Answer 211

resonance

Question 212

operating frequency

Answer 212

resonance frequency

Question 213

multiple reflection

Answer 213

reverberation

Question 214

a number that depends on flow speed and viscosity to predict the onset of turbulence

Answer 214

Reynolds number

Question 215

the anatomic region from which pulsed Doppler echoes are accepted

Answer 215

sample volume

Question 216

the amount of hue present in a mix with white

Answer 216

saturation

Question 217

a line produced on a display that represents ultrasonic echoes returning from the body. A sonographic image is composed of many such lines

Answer 217

scan line

Question 218

transducer assembly

Answer 218

scanhead

Question 219

the sweeping of a sound beam through the anatomy to produce an image

Answer 219

scanning

Question 220

an object that scatters sound in many directions because of its small size or fits surface roughness

Answer 220

scatterer

Question 221

diffusion or redirection of sound in several directions upon encountering a particle suspension or a rough surface

Answer 221

scattering

Question 222

a geometric figure bounded by two radii and the arc of the circle included between them

Answer 222

sector

Question 223

an anatomic image presented in a pie slice- shaped format

Answer 223

sector image

Question 224

ability of an imaging system to detect weak echoes

Answer 224

sensitivity

Question 225

reduction in echo amplitude from reflectors that lie behind a strongly reflecting or attenuating structure

Answer 225

shadowing

Question 226

weaker beams of sound traveling out from a single element in directions different from those of the primary beam

Answer 226

side lobes

Question 227

information-bearing voltages in an electric circuit; an acoustic, visual, electric, or other conveyance of information. The physical representation of a message or information

Answer 227

signal

Question 228

an electronic device that manipulates electric signals in preparation for appropriate presentation of information contained in them

Answer 228

signal processor

Question 229

thickness of the scanned tissue volume perpendicular to the scan plane

Answer 229

slice thickness

Question 230

medical two-dimensional, cross-sectional, and three-dimensional anatomic and flow imaging using ultrasound

Answer 230

sonography

Question 231

traveling wave of acoustic variables

Answer 231

sound

Question 232

the region of a medium that contains virtually all of the sound produced by a transducer

Answer 232

sound beam

Question 233

an emitter of ultrasound; transdcuer

Answer 233

source

Question 234

averaging of frames that view the anatomy from different angles

Answer 234

spatial compounding

Question 235

length of space over which a pulse occurs

Answer 235

spatial pulse length

Question 236

the granular appearance of images and spectral displays that is caused by the interference of echoes from the distribution of scatterers in tissue

Answer 236

speckle

Question 237

separation of frequencies in a Doppler signal for display as a Doppler spectrum; the application of the Fourier transform to determine the frequency components present in a Doppler signal

Answer 237

spectral analysis

Question 238

the widening of the Doppler-shift spectrum; that is, the increase in the range of Doppler-shift frequencies present that occurs because of a broadened range flow velocities encountered by the sound beam. This occurs for disturbed and turbulent flow

Answer 238

spectral broadening

Question 239

the presentation of Doppler-information in a quantitative form of Doppler shift versus time. Visual display of a Doppler spectrum

Answer 239

spectral-Doppler display

Question 240

a device that derives a frequency spectrum from a complex signal

Answer 240

spectrum analyzer

Question 241

reflection from a large, flat, smooth boundary

Answer 241

specular reflection

Question 242

propagation speed that is different from the assumed value

Answer 242

speed error

Question 243

narrowing of a vessel lumen

Answer 243

stenosis

Question 244

property of a medium; applied pressure divided by the fractional volume change produced by the pressure

Answer 244

stiffness

Question 245

the increase or decreaseof the length of a segment of a material, subjected to a stress, divided by its original length

Answer 245

strain

Question 246

a line representing the path of a motion of a particle of fluid

Answer 246

streamline

Question 247

nonspecific term referring hear to amplitude or intensity

Answer 247

strength

Question 248

a force per unit area applied to a material that compresses or stretches it

Answer 248

stress

Question 249

ability to distinguish closely spaced events in time; improves with increased frame rate

Answer 249

temporal resolution

Question 250

a device without tissue-like properties that is designed to measure some characteristic of an imaging system

Answer 250

test object

Question 251

an indicator of thermal mechanism activity (estimated temperature rise); a value equal to transducer acoustic output power divided by the estimated power required to raise tissue temperature by 1 degree celcius

Answer 251

thermal index

Question 252

equalization of echo amplitude differences caused by different attenuations for different reflector depths

Answer 252

time gain compensation

Question 253

a device that converts energy from one form to antoher

Answer 253

transducer

Question 254

transducer element(s) with damping and matching materials assembled in a case

Answer 254

transducer assembly

Question 255

angle between the transmitted sound direction and a line perpendicular to the media boundary

Answer 255

transmission angle

Question 256

a sound wave in which the particle motion is perpedicular to the direction of wave travel, also called a shear wave

Answer 256

transverse wave

Question 257

random, chaotic, multidirectional flow of a fluid with mixing between layers; flow that is not laminar

Answer 257

turbulence

Question 258

sound having a frequency greater than what humans can hear, that is, greater than 20 kHz

Answer 258

ultrasound

Question 259

a device that converts electric energy to ultrasound energy, and vice versa

Answer 259

ultrasound transducer

Question 260

square of standard deviation; one of the outputs of the autocorrelation process; a measure of spectral broadening

Answer 260

variance

Question 261

linear sequenced array that emits pulses from different starting points and (by phasing) in different directions

Answer 261

vector array

Question 262

an imaginary beam that describes the result of retrospective, computed beam forming. The virtual beam can be imagined in transmission or reception form

Answer 262

virtual beam

Question 263

an imaginary reception beam that can be thought of as determine the echo produced at each pixel location in the image

Answer 263

virtual reception beam

Question 264

an imaginary laser-thin transmitted ultrasound beam that can be thought of as producing the excellent detail resolution throughout the image that is accomplished with retrospective, computed beam forming

Answer 264

virtual transmission beam

Question 265

resistance of a fluid to flow

Answer 265

viscosity

Question 266

three-dimensional imaging

Answer 266

volume imaging

Question 267

volume of fluid passing a point per unit of time

Answer 267

volumetric flow rate

Question 268

an electric filter that passes frequencies above a set level and eliminates strong, low-frequency Doppler shifts from pulsating heart or vessel walls or tissue motion

Answer 268

wall filter

Question 269

traveling variation of one or more quantities

Answer 269

wave

Question 270

length of space over which a cycle occurs

Answer 270

wavelength

Question 271

an anechoic region appearing beneath echo frequencies presented on a Doppler spectral display

Answer 271

window

Question 272

a measure of the hardness (stiffness) of a material. It is the ratio of the applied stress to the resulting strain in a material subjected to the stress

Answer 272

Young’s modulus

Question 273

an analog detector that yields mean Doppler shift as a function of time

Answer 273

zero-crossing detector