Physics Final Penny Vocabulary Flashcards
(304 cards)
1
Q
the rule that states that it takes 13 microseconds for sound to travel 1 cm in soft tissue
A
13 us rule
2
Q
the conversion of sound enery to heat
A
absorption
3
Q
the production of bubbles in a liquid medium
A
acoustic cavitations
4
Q
uses acoustic radiation force to compress the soft tissue and provides a qualitative measurement of stiffness without requiring pressure input from the sonographer
A
acoustic radiation force impulse imaging
5
Q
the interference pattern caused by scatterers that produces the granular appearance of tissue on a sonographic image
A
acoustic speckle
6
Q
changes that occur within a medium as a result of sound traveling through that medium
A
acoustic variables
7
Q
as low as reasonably achieveable; the principle that states one should always use the lowest power and shortest scanning time possible to reduce potential exposure to the patient
A
ALARA
8
Q
the wraparound of the spectral or Color Doppler display that occurs when the frequency shift exceeds the Nyquist limit; occurs only with pulsed-wave Doppler
A
aliasing
9
Q
amplitude mode; the height of the spike on the image is related to the strength (amplitude) of the echo generated by the reflector
A
A-mode
10
Q
the part of the receiver that increases or decreases the received echoes equally, regardless of depth
A
amplification
11
Q
the maximum or minimum deviation of an acoustic variable from the average value of that variable; the strength of the reflector
A
amplitude
12
Q
the part of the digital scan coverter that converts the analog signals from the receiver to binary for processing by the computer
A
analog-to-digital converter (A-to-D)
13
Q
without echoes, or black
A
anechoic
14
Q
the tool used to inform the machine what the flow angle is so that velocities can be accurately calculated
A
angle correction
15
Q
the diameter of the piezoelectric element(s) producing the beam
A
aperture
16
Q
the technique that varies the voltage to the individual elements to reduce grating lobes
A
apodization
17
Q
the transducer with multiple active elements
A
array
18
Q
echoes on the screen that are not representative of actual anatomy, or reflectors in the body that are displayed on the screen
A
artifacts
19
Q
the rate at which sound is attenuated per unit depth
A
attenuation coefficient
20
Q
a decrease in the amplitude and intensity of the sound beam as sound travels through tissue
A
attenation
21
Q
the color Doppler processing technique that assesses pixels as stationary or in motion
A
autocorrelation
22
Q
a portable device that is used to detect and treat abnormal heart rhytyms with electrical defibrillation
A
automatic external defribrillator
23
Q
same as real-time ultrasound
A
automatic scanning
24
Q
the ability to accurately identify reflectors that are arranged parellel to the ultrasound beam
A
axial resolution
25
the damping material of the transducer assembly, which reduces the number of cycles produced in a pulse
backing material
26
scattered sound waves that make their way back to the transducer and produce an image on the display
backscatter
27
the range of frequencies present within the beam
bandwidth
28
the acronym used to describe color Doppler scale: blue away, red towards
BART
29
the operator-adjustable dividing line between positive frequency shifts and negative frequency shifts on spectral and color Doppler
baseline
30
the part of the machine that shapes and steers the beam on the transmit end
beam former
31
the ratio of the center intensity to the average spatial intensity; also referred to as the SP/SA factor or beam uniformity coefficient
beam uniformity ratio
32
the principle that describes the inverse relationship between velocity and pressure
Bernoulli's priniciple
33
a non-Doppler technology that offers real-time imaging of blood flow while scanning in gray scale
B-flow imaging
34
the Doppler device that can detect positive and negative Doppler shifts
bidirectional Doppler
35
the digital language of zeroes and ones
binary system
36
black and white image
bistable
37
the smallest unit of memory in a digital device
bit
38
brightness mode; the brightness of the dots is proportional to the strength of the echo generated by the reflector
B-mode
39
the stationary layer of blood vells immediately adjacent to the vessel wall
boundary layer
40
the term describing the intensity or luminance of the color Doppler display
brightness
41
eight bits of memory
byte
42
the muscles in the calf that, upon contraction, propel venous blood toward the heart
calf muscle pump
43
the ability of veins to store blood
capacitance
44
technology used to create comparable transducer technology to piezoelectric materials
capacitative micromachined ultrasound transducers
45
display that uses an electron gun to produce a stream of electrons toward a phosphor-coated screen
cathode ray tube (CRT)
46
acoustic noise in the color and/or spectral Doppler signal
clutter
47
a way of processing the pulse to improve contrast resolution and reduce speckle
coded excitation
48
accessory vessels that connect portions of the same blood vessel together
collateral blood vessels
49
Doppler shift information presented as a color (hue) superimposed over the grayscale image
color Doppler imaging
50
the setting for color Doppler that allows the operator to select frequency shift threshold; it determines whether color pixels should be displayed preferentially over grayscale pixels
color priority
51
a type of reverberation artifact caused by small reflectors (i.e. surgical clips)
comet tail
52
the function of the receiver that changes the brightness of the echo amplitudes to compensate for attenuation with depth
compensation
53
an area in the sound wave of high pressure and density
compression
54
the function of the receiver that decreases the range of signal amplitudes present within the machine's receiver; opposite of dynamic range
compression (receiver function)
55
occurs when in-phase waves meet; the amplitudes of the two waves are added to form one large wave
constructive interference
56
the equation that describes the change in velocity as the area changes in order to maintain the volume of blood flow
continuity equation
57
sound that is continuously transmitted
continuous wave
58
Doppler device that uses continuous-wave ultrasound transmission; a device that consists of two elements, one element is used by the system to constantly transmit sound and the other is used to constantly receive sound
continuous wave Doppler
59
the ability to differentiate one shade of gray from another
contrast resolution
60
type of imaging in which an ultrasound contrast agent containing microscopic gas bubbles is used to improve visualization of structures or blood flow
contrast-enhanced ultrasound
61
the point at which a stenosis is hemodynamically significant with a pressure drop distal to the stenosis
critical stenosis
62
a synonym for the active element of the transducer, the piezoelectric part of the transducer assembly that produces sound
crystal
63
the temperature at which an ultrasound transducer will gain its piezoelectric properties, and also the temperature at which a transducer will lose the ability to produce sound if heated again above this temperature
Curie point
64
the transducer commonly referred to as a curvilinear or convex probe
curved sequenced arrayh
65
same as backing material; the part of the transducer assembly that reduces the number of cycles produced in a pulse
damping material
66
the process of reducing the number of cycles of each pulse in order to improve axial resolution
damping
67
a unit that establishes a relationship or comparison between two values of power, intensity, or amplitude
decibels
68
the function of the receiver that makes the signal easier to process by performing rectification and smoothing
demodulation
69
mass per unit volume
density
70
the inability to determine the depth of the reflector if the pulses are sent out too fast for them to be timed
depth ambiguity
71
occurs when out of phase waves meet; the amplitude of the resultant wave is smaller than either of the original waves
destructive interference
72
a group of metabolic diseases that result from a chronic disorder of carbohydrates metabolism
diabetes mellitus
73
a complication of diabetes that results from the severe lack of insulin
diabetic ketoacidosis
74
the relaxation of the heart following contraction
diastole
75
part of the digital scan converter that converts the binary signals from computer to memory to analog for display and storage
digital to analog converter (D-to-A)
76
relationship that implies that if one variable decreases, the other also decreases or if one variable increases, the other also increases;
directly related
77
how far apart objects are; may also be referred to as vibration or displacement
distance
78
spreading of the beam that occurs in the far zone
divergence
79
the change in the frequency of the received signal related to motion of reflector
Doppler effect
80
the equation that explains the relationship of the Doppler frequency shift and the propagation speed
Doppler equation
81
the test object used to evaluate the flow direction, the depth capability or penetration of the Doppler beam, and the accuracy of the sample volume location and measured velocity
Doppler phantom
82
real-time two-dimensional imaging combined with the spectral Doppler display
duplex
83
the percentage of time that sound is actually being produced
duty factor
84
the series of echo amplitudes present within the signal
dynamic range
85
refraction artifact caused by the curved surface of the reflector
edge shadowing
86
the sum of the individual resistances when multiple vessels are connected in series
effective resistance
87
a sonographic technique used to evaluate the stiffness of a mass or tissue
elastography
88
arc-like bands that occur when the machine is too close to an unshielded electrical device
electrical interference
89
the piezoelectric part of the transducer assembly that produces sound
element
90
the resoltion in the third dimension of the beam or the slick thickness plane
elevational plane
91
the resolution in the third dimension of the beam; the slice-thickness plane
elevational resolution
92
the difference in energy between two points
energy gradient
93
an artifact caused by sound passing through an area of lower attenuation
enhancement
94
the number of pulses per scan line in color Doppler; also referred to as packet size
ensemble length
95
the scientific study of creating tools and using equipment effectively in order to help the human body adjust to the work environment
ergonomics
96
pressure applied to the outside of an object
extrinsic pressure
97
the diverging part of the beam distal to the focal point
far zone
98
a mathematical process used for analyzing and processing the Doppler signal to produce the spectral waveform
fast Fourier transform
99
places grayscale pixels where there is no signal information based on adjacent scan lines; also referred to as pixel interpolation
fill-in interpolation
100
a motion artifact caused by the movement of tissue when using power Doppler
flash artifact
101
the volume of blood per unit time; typically measured in liter per minute or milliliter per second; represented by the symbol O
flow
102
the area of the beam with the smallest beam diameter
focal point
103
the portion of the transducer that is in contact with the patient's skin
footprint
104
three-dimensional ultrasound in real-time
four dimensional ultrasound
105
the number of frames per second
frame rate
106
one complete ultrasound image
frame
107
far zone
Fraunhofer zone
108
averages the frequencies across the image to improve contrast resolution and reduce speckle
frequency compounding
109
the difference between the transmitted and received frequencies
frequency shift
110
near zone
Fresnel zone
111
a form of resistance, caused by two materials rubbing against each other, thereby converting energy to heat
friction
112
the operating or resonating frequency emitted by the transducer
fundamental frequency
113
technology that provides the ability to view alternate imaging modality during real-time sonographpy; also referred to as hybrid imaging
fusion imaging
114
an artifact caused by extraneous sound that is not located along primary beam path; occurs with arrays; reduced or eliminated apodization, subdicing, and tissue harmonics
grating lobes
115
the depth at which sound has lost half its intensity
half-intensity depth
116
harmonic signal produced by the patient's tissue and that is a multiple of the fundamental frequency
harmonics
117
US law, which, among many goals, upholds patient confidentiality and requires the use of electronic medical records
Health insurance portability and accountability act
118
the study of blood flow through the vessels of the body
hemodynamics
119
inflammation of the liver
hepatitis
120
a unit of frequency
hertz
121
the ability to place echoes in the proper location horizontally and perpendicular to the sound beam
horizontal calibration
122
a term used to describe displayed colors
hue
123
states that waves are the result of interference of many wavelets produced at the face of the transducer
Huygen's principle
124
a device used to measure the output intensity of the transducer
hydrophone
125
describes the relationship between gravity, density of the blood, and distance between an arbitrary reference point
hydrostatic pressure
126
displayed echoes that are relatively brighter than the surrounding tissue
hyperechoic
127
a lower than normal blood surgar level
hypoglycemia
128
the resistance to the propagation of sound through a medium
impedance
129
Newton's principle that states that an object at rest stays at rest and an object in motion stays in motion, unless acted on by an outside forece
inertia
130
supplied with nerves
innervated
131
waves whose peaks and troughs overlap
in-phase
132
the percentage of sound reflected at an interface
intensity reflection coefficient
133
the percentage of sound transmitted at an interface
intensity transmission coefficient
134
the power of the wave divided by the area over which it is spread; the energy per unit area
intensity
135
the dividing line between two different media
interface
136
the technique that employs a miniature ultrasound transducer placed on a catheter and inserted into the circulatory system
intravascular ultrasound
137
relationship that implies that if one variable decreases, the other increases or if one variable increases, the other decreases
inversely related
138
the energy form of flowing blood
kinetic energy
139
a voluntary process that acknowledges an organization's competency and credibility according to standards and essentials set forth by a reliable source
lab accreditation
140
the flow profile represented by blood that travels in nonmixing layers of different velocities, with the fastest flow in the center and the slowest flow near the vessel walls
laminar flow
141
the ability to accurately identify reflectors that are arranged perpendicular to the ultrasound beam
lateral resolution
142
the total amount of energy in a system never changes, although it might be in a different form from which it started
law of conservation of energy
143
the man-made ceramic of which many transducer elements are made
lead zirconate titanate
144
the transducer commonly referred to as the linear probe or transducer
linear sequenced array
145
display that uses the twisting and untwisting of liquid crystals in front of a light source
liquid crystal display
146
waves in which the molecules of the medium vibrate back and forth in the same direction that the waves are traveling
longitudinal waves
147
the brightness of the color Doppler image
luminance
148
the timing component of the ultrasound machine that notes how long it takes for signals to return from reflectors
master synchronizer
149
the component of the transducer that is used to step down the impedance from that of the element to that of the patient's skin
matching layer
150
transducer that acquires real-time volumes using up to 10,000 elements, compared to the 128-512 elements used in standard 1D array transducers
matrix array transducer
151
the calculation used to identify the likelihood that cavitation could occur
mechanical index
152
transducers with a motor for steering the beam
mechanical scanheads
153
any form of matter: solid, liquid, or gas
medium
154
an artifact caused by sound bouncing off strong reflectors and causing a structure to appear on both sides of the reflector
mirror image artifact
155
millimeters of mercury
mmHg
156
motion mode; used to display motion of the relfectors
M-mode
157
an artifact caused by the beam bounching off several reflectors before returning to the transducer
multipath
158
the part of the beam between the element and the focal point
near zone
159
the length of the region from the transducer face to the focal point
near-zone length
160
low-level echoes on the display that do not contribute useful diagnostic information
noise
161
Doppler device that cannot differentiate between positive and negative frequency shifts
nondirectional Doppler
162
a stenosis that does not necessarily compromise blood flow to organs or structures
nonhemodynamically significant stenosis
163
reflectors that are smaller than the wavelength of the incident beam
nonspepcular reflectors
164
angle of incidence is 90 degrees to the interface
normal incidence
165
a hospital-acquired infection
nosocomial infectior
166
the maximum frequency shift sampled without aliasing; equal to one half the pulse repetition frequency
Nyquist limit
167
angle of incidence is less than or greater than 90 degrees to the interface
oblique incidence
168
a law used in electronics in which flow is equal to the pressure differential divided by resistance
Ohm's law
169
the component of a continuous-wave Doppler device that produces the voltage that drives the transducer
oscillator
170
waves that are 180 degrees opposite each other; the peak of one wave overlaps the trough of the other and vice versa
out of phase
171
output power; strength of sound entering the patient
output
172
receiver function that increases or decreases all of the echo amplitudes equally
overall gain
173
the number of pulses per scan line; also called the ensemble length
packet size
174
a measurable quantity
parameter
175
the movement of molecules due to propagating sound energy
particle motion
176
distance to the reflector
path length
177
the time it takes for one cycle to occur
period
178
the averaging of color frames in order to display blood flow with a low signal to noise ratio
persistence
179
the component of the Doppler device that determines positive opposed to negative frequency shifts and, therefore, direction of blood flow
phase quadrature
180
the transducer that uses phasing, or small time differences, to steer and focus the beam
phased array
181
the characteristic waveform of peripheral veins; flow is determined by respiratory variations as a result of intrathoracic pressure changes
phasic flow
182
in arteries, phasicity describes the shape of the waveform based on the resistiveness of the distal bed; in veins, phasicity describes the flow pattern that results from respiratory variation
phasicity
183
the method of focusing and/or steering the beam by applying electrical impulses to the piezoelectric elements with small time differences between shocks
phasing
184
a type of display and storage device commonly used in sonography and other imaging modalities
picture archiving and communications system
185
a material that generates electricity when pressure is applied to it, and one that changes shape when electricity is applied to it; also referred to as the element or crystal
piezoelectric materials
186
the ability to convert pressure into electricity and electricity into pressure
piezoelectric
187
the smallest component of a two dimensional digital image
pixel (picture element)
188
the flow profile represented by blood typically flowing at the same velocity
plug flow
189
the law that describes the relationship of resistance, pressure, and flow
Poiseuille's Law
190
occurs in the D-to-A converter; the image must be frozen
post processing
191
pressure energy created by the beating heart
potential energy
192
Doppler mode in which the signal is determined by the amplitude (strength) of the shift, not the shift itself; amplitude is directly proportional to the number of red blood cells
power Doppler
193
the rate at which work is performed or energy is transmitted
power
194
occurs at the receiver to the relatively weak signal coming from the transducer; ultimately, the signal has to be increased so the rest of the receiver can analyze it
preamplification
195
occurs in the A-to-D converter; the image must be live
preprocessing
196
the difference between pressures at two points of a blood vessel
pressure gradient
197
force per unit area or the concentration of force
pressure
198
a methodical way of evaluating equipment's performance on a routine basis to ensure proper and accurate equipment function
preventative maintenance
199
to transmit through a medium
propagate
200
artifact that occurs because the actual propagation speed of the tissue is greater than or less than 1540 meter per second, the machine places the reflector at the wrong location on the display
propagation speed errors
201
the speed at which a sound wave travels through a medium
propagation speed
202
Doppler measurement used to determine how pulsatile a vessel is over time
pulsatility index
203
blood that flows in a pattern representative of the beating heart, with increasesand decreases in pressure and blood flow velocity
pulsatility
204
the time during which the sound is actually being transmited
pulse duration
205
harmonic technology in which the fundamental frequency is flipped 180 degrees and transmitted, which cancels out the fundamental frequency via destructive interference, leaving only the harmonic signal
pulse inversion technology
206
the number of pulses of sound produced in 1 second
pulse repetition frequency
207
the time taken for a pulse to occur
pulse repetition period
208
sound that is sent out in pulses
pulsed wave
209
the Doppler technique that uses pulses of sound to obtain Doppler signals from a user-specified depth
pulsed-wave Doppler
210
part of the beam former that controls the amount of energy in the pulse
pulser
211
a planned program consisting of scheduled equipment-testing activities that confirm the correct performance of equipment
quality assurance programs
212
a measure of beam purity; the operating frequency of the transducer divided by the bandwidth
quality factor (Q-factor)
213
forces exerted by a sound beam on an absorber or reflector that can alter structures
radiation forces
214
equation used to calculate the distance to the reflector; in soft tissue, d = 0.77t where "d" is the depth of the reflector and "t" represents the round-trip time of the pulse
range equation
215
the gate placed by the operator in the region where Doppler sampling is desired; used with pulsed-wave Doppler
range gate
216
the ability to determine how far away a reflector is so it can be displayed on the screen; without range resolution there is depth ambiguity
range resolution
217
the ability to determine the depth of echoes by timing how long it takes for the echoes to go from the transducer to the reflector and back; ultilized by pulsed-wave devices
range resolution
218
an area in the sound wave of low pressure and density
rarefaction
219
the fixed quantity owed as the sound beam travels through tissue (related to attenuation)
rate
220
very small reflectors, like red blood cells
Rayleigh scatterers
221
the type of magnification performed in the D-to-A converter that magnifies the image by enlarging the pixels
read zoom
222
live ultrasound, also known as automatic scanning
real time
223
the component of the machine that processes the signals coming back from the patient
receiver
224
the part of the receiver that inverts the negative voltages to positives
rectification
225
the echo; the portion of sound that returns from an interface
reflection
226
the change in the direction of the transmitted sound beam that occurs with oblique incidence angles and dissimilar propagation speeds
refraction
227
the ability to place echoes in the correct location
registration
228
function of the receiver that is used to reduce image noise; sets a threshold below which the signal will not be displayed
rejection
229
the downstream impedance to flow; determined by vessel length, vessels radius, and viscosity of blood
resistance
230
Doppler measurement used to quantitate the resistiveness of the distal bed
resistive index
231
to alternatively expand and contract
resonate
232
an artifact caused by the beam bouncing between two strong reflectors
reverberation
233
the formula used to quantitate the presence of turbulence; Reynolds numbers greater than 2000 typically indicate turbulence
Reynolds number
234
an artifact caused by vibration of air bubbles
ring-down
235
the area within the range gate where the Doppler signals are obtained
sample volume
236
the amount of white added to a hue; the more white there is, te less saturated the color
saturation
237
the spectral Doppler and color Doppler tool that controls the number of pulses transmitted per second to obtain the Doppler information; also known as pulse repetition frequency in spectral Doppler and color Doppler
scale
238
the part of the ultrasound machine that processes the signals from the receiver; consists of the A-to-D converter, computer memory, and D-to-A converter
scan converter
239
created when one or more pulses of sound return from the tissue containing information related to the depth and amplitude of the reflectors
scan line
240
the phenomenon that occurs when sound waves are dispersed into different directions because of the small reflector size compared with the incident wavelength
scattering
241
the ability of a system to diplay low-level or weak echoes
sensitivity
242
an artifact caused by the failure of sound to pass through a strong attenuator
shadowing
243
elastography technique that uses shear wave information to analyze the stiffness of tissue
shear wave elastography
244
the body's pathologic response to illness, trauma, or severe physiologic or emotional stress
shock
245
an artifact caused by extraneous sound that is not found along the primary beam path; occurs with single element transducers
side lobes
246
another name for the receiver
signal processor
247
artifact that occurs as a result of the beam not being razor thin; thus unintended echoes may appear in the image as the beam slices through structures adjacent to intended reflectors
slice thickness artifact
248
the test object that evaluates the elevational resolution, or the thickness portion, of the sound beam perpendicular to the imaging plane
slick-thickness phantom
249
the third dimension of the beam
slice-thickness plane
250
part of the demodulation component of the receiver; an "envelope" is wrapped around the signal to eliminate the "humps"
smoothing
251
law used to describe the angle of transmission at an interface based on the angle of incidence and the propagation speeds of the two media
Snell's law
252
a traveling variation in pressure
sound
253
technique that eliminates edge shadowing because the object is imaged at different angles
spatial compounding
254
the length of a pulse
spatial pulse length
255
the ability of the system to distinguish between closely spaced objects; refers to axial, lateral, contrast, and elevational resolution
spatial resolution
256
algorithm used in signal processing to reduce the amount of acoustic speckl
speckle reduction
257
the method used to obtain the strain information
speckle tracking
258
the filling of the spectral window
spectral broadening
259
the area underneath the envelope on the spectral display
spectral window
260
reflections that occur when the sound impinges upon a large, smooth reflector at a 90 degree angle
specular reflectors
261
pathologic narrowing of a blood vessel
stenosis
262
the ablity of an object to resist compression and relateds to the hardness of a medium
stiffness
263
operator dependent type of elastography that measure the change in tissue as a result of compression
strain elastography
264
the changing of the shape of the muscle as it lengthens and contracts
strain
265
when acoustic fields cause motion of fluids
streaming
266
dividing the piezoelectric elements into very small pieces to reduce grating lobes
subdicing
267
the operator adjustable spectral Doppler control that increases or decreases the number or heartbeats visualized on the spectral display
sweep speed
268
the time period of the cardiac cycle when the heart is contracting
systole
269
rapid heart rate; a rate that exceeds the normal rate for the person's age
tachycardia
270
an arterial waveform shape with a delayed peak systolic upstroke that indicates proximal obstruction
tardus parvus
271
ability to display moving structures in real time; also known as frame rate
temporal resolution
272
the calculation used to pedict the maximum temperature elevation in tisisues as a result of the attenuation of sound
thermal index
273
allows the user to see width, height, and depth; may also be referred to as volume scanning
three-dimensional ultrasound
274
combination of platelets, red blood cells, and fibrin that make up a blood clot
thrombus
275
color Doppler imaging technique used to document wall mation
tissue Doppler imaging
276
the test object that mimics the acoustic properties of human tissue and is used to ensure proper equipment performanfce
tissue-equivalent phantom
277
the total amount of sound (in dB) that has been attenuated at a given depth
total attenuation
278
any device that converts one form of energy into antoher; may also refer to the part of the ultrasound machine that produces sound
transducer
279
ensures the electrical signals travel in the correct direction
transmit-receive switch
280
the difference in pressure inside a vessel compared to the pressure outside of the vessel
transmural pressure
281
type of wave in which the molecules in ia medium vibrate at 90 degrees to the direction of travel
transverse waves
282
the ability to visualize real-time grayscale, color Doppler, and spectral Doppler simultaneously
triplex
283
component of the backing material
tungsten
284
the outer layer of a blood vessel
tunica adventitia
285
the inner layer of a blood vessel which is closest to the flowing blood
tunica intima
286
the middle, muscular layer of a blood vessel
tunica media
287
chaotic, disorderly flow of blood
turbulent flow
288
sound waves of frequencies exceeding the range of human hearing
ultrasound
289
the color Doppler scale with mean velocities displayed vertically on the scale and turbulence displayed horizontally
variance mode
290
a network of small blood vessels that supply blood to the walls of arteries and veins
vasa vasorum
291
the narrowing of a blood vessel caused by the contraction of the vessel wall
vasoconstriction
292
the widening of a blood vessel caused by the relaxation of the vessel wall
vasodilatation
293
the color Doppler scale with mean velocities displayed vertically
velocity mode
294
the energy loss caused by friction
viscous energy
295
the distance from a transdcuer
vertical depth
296
the smallest component of a three-dimensional image
voxel (volume element)
297
the operator control that eliminates low-frequency, high-amplitude signals caused by wall or valve motion; also called a high-pass filter
wall filter
298
the leading edge of a wave which is perpendicular to the direction of the propagating wave; formed as a result of Huygen's principle
wavefront
299
the length of a single cycle of sound
wavelength
300
a small wave created as a result of Huygen's principle
wavelet
301
the type of magnification performed in the A-to-D converter that magnifies the image by redrawing it before it is stored in memory
write zoom
302
the plane that is perpendicular to the beam path
x-axis
303
the plane that is parallel to the beam path
y-axis
304
the brightness, or amplitude of the dots on the display
z-axis
