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Sono 2343 > Chapter 5 > Flashcards

Chapter 5 Flashcards

1
Q

average attenuation in soft tissue is?

A

0.5 dB every centimeter

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2
Q

if the question is with units of V, which ratio are we talking about?

A

amplitude/voltage

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3
Q

if the question is with W, which ratio are we talking about?

A

power

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4
Q

power ratio?

A

output power/input power

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5
Q

sample volume

A

the anatomic region from which pulsed Doppler echoes are accepted

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6
Q

saturation

A

the amount of hue present in a mix with white

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7
Q

spectral analysis

A

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.

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8
Q

spectral broadening

A

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 of flow velocities encountered by the sound beam. This occurs for disturbed and turbulent flow.

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9
Q

spectral-doppler display

A

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

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10
Q

spectrum analyzer

A

a device that derives a frequency spectrum from a complex signal

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11
Q

stenosis

A

narrowing of a vessel lumen.

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12
Q

streamlines

A

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

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13
Q

turbulence

A

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

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14
Q

variance

A

square of standard deviation; one of the outputs of the autocorrelation process; a measure of spectral broadening (i.e. spread around the mean).

helps highlight turbulent flow states.

usually appears green on display.

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15
Q

viscosity

A

resistance of a fluid to flow

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16
Q

volumetric flow rate

A

volume of fluid passing a point per unit of time (ie per second or minute).

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17
Q

wall filter

A

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.

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18
Q

window

A

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

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19
Q

inertia

A

resistance to acceleration

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20
Q

laminar flow

A

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

streamlines are straight and parallel

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21
Q

luminance

A

brightness of a presented hue and saturation.

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22
Q

parabolic flow

A

laminar flow with a profile in the shape of a parabola

while fluid flows down a tube

form of laminar flow

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23
Q

phase quadrature

A

two signals differing by one-fourth of a cycle

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24
Q

plug flow

A

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

at entrance of tube

speed of fluid is constant

form of laminar flow

moves as a unit

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25
Q

poise

A

unit of viscosity

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26
Q

poiseuille equation

A

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

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27
Q

priority

A

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

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28
Q

pulsatile flow

A

flow that accelerates and decelerates with each cardiac cycle.

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29
Q

pulsed Doppler

A

a Doppler device or procedure that uses pulsed-wave ultrasound

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30
Q

range gating

A

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

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31
Q

resistance

A

pressure difference divided by volume flow rate for steady flow

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32
Q

Doppler-power display

A

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

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33
Q

Doppler shift

A

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

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34
Q

Doppler spectrum

A

the range of frequencies present in Doppler-shifted echoes.

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35
Q

Duplex instrument

A

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

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36
Q

eddies

A

regions of circular flow patterns present in turbulence

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37
Q

ensemble length

A

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

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38
Q

fast fourier transform

A

digital computer implementation of the Fourier transform.

a math technique for separating a spectrum into its individual frequency components.

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39
Q

filter

A

an electric circuit that passes frequencies within a define range.

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40
Q

flow

A

to move in a stream; volume flow rate.

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41
Q

fluid

A

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

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42
Q

frequency spectrum

A

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

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43
Q

gate

A

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

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44
Q

hue

A

the color perceived based on the frequency of light.

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45
Q

autocorrelation

A

a rapid technique, used in most color-Doppler instruments, to obtain mean Doppler-shift frequency.

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46
Q

baseline shift

A

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

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47
Q

bernoulli effect

A

pressure reduction in a region of high-flow speed.

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48
Q

bidirectional

A

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

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49
Q

clutter

A

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

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50
Q

Color-Doppler display

A

the presentation of 2D, real-time Doppler-shift information in color superimposed on a real-time, grayscale, anatomic, cross-sectional image. Flow directions toward and away from the transducer (ie positive and negative Doppler shifts) are presented as different colors on the display.

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51
Q

compliance

A

distensibility; nonrigid stretch-ability of vessels

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52
Q

continuous-wave Doppler

A

a Doppler device or procedure that uses continuous-wave ultrasound

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53
Q

disturbed flow

A

flow that cannot be described by straight, parallel streamlines.

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54
Q

Doppler angle

A

the angle between the sound beam and the flow direction

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55
Q

Doppler effect

A

a change in frequency caused by reflector motion

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56
Q

Doppler equation

A

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

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57
Q

ultrasound can detect and present?

A

motion information

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58
Q

motion is detected by using

A

the Doppler effect

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59
Q

insufficiency/regurgitation

A

valves allowing reverse flow by not closing completely

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60
Q

units for viscosity

A

poise

kg/ms

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61
Q

pressure

A

force/are

distributed equally throughout static fluids and exerts its force in all directions

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62
Q

what’s the normal viscosity for blood?

A

0.035 poise at 37 degrees Celsius

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63
Q

hydrostatic pressure

A

describes the force of gravity on static fluid

pressure difference required for flow to occur

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64
Q

pressure gradient

A

aka pressure difference

the greater the pressure difference, the greater the flow rate

pressure diff/distance between the 2 pressure points

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65
Q

volumetric flow rate

A

is the volume of blood passing a point per unit of time

adult blood flow rate is 5,000 mc/min

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66
Q

types of flow

A

plug flow

laminar flow

parabolic flow

non-parabolic flow

disturbed flow

turbulent flow

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67
Q

pulsatile flow

A

nonsteady flow with acceleration and deceleration due to the cardiac cycle (beating heart)

happens in the heart and the arterial side

relationship between pressure and flow rate depends on impedance (resistance), inertia, and compliance (expansion and contraction) of the vessel walls

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68
Q

windkessel effect

A

expansion and contraction of vessels that keeps blood flowing forward

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69
Q

flow reversal

A

when no valves are present to prevent it

it’s normal in distal veins during diastole

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70
Q

continuity rule

A

volumetric flow rate is constant at every unit

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71
Q

flow speed ____ at a stenosis and ____ can occur distal to it.

A

increases, turbulence

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72
Q

occlusion

A

vessel is blocked and there’s no flow

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73
Q

bernoulli effect

A

decreased pressure in regions of higher flow speed

necessary o allow fluid to accelerate into the stenosis and decelerate out of if

if flow speed increases, the magnitude of the pressure drop increases

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74
Q

Doppler effect

A

is a change in frequency (and wavelength) caused by motion of a reflector, receiver, or a sound source

amount of change in frequency depends on reflector motion speed, angle between the wave propagation direction and motion, and the frequency of the wave emitted by the source

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75
Q

if a reflector is moving towards the receiver, the echo has a ___ frequency

A

higher

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76
Q

if a reflector is moving away from the receiver, the echo has a ___ frequency

A

lower

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77
Q

doppler shift

A

the change in frequency caused by motion is called Doppler-shift frequency

is equal to the received frequency - the source frequency

difference between the emitted frequency and the echo frequency from moving scatterers

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78
Q

positive doppler shift

A

received frequency is greater than the emitted frequency

approaching reflector

higher frequency

moves against propagation speed

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79
Q

negative doppler shift

A

received frequency is smaller than emitted frequency

receding reflector

lower frequency

moves along the propagation speed

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80
Q

a higher operating frequency will have a ___ doppler shift

A

larger

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81
Q

the doppler shift depends on the ____ of the doppler angle.

A

cosine

82
Q

only the portion of motion direction that is ____ to the beam contributes to the doppler effect

A

parallel

83
Q

the ___ the doppler angle, the ____ the doppler shift

A

larger, less

84
Q

angle 90 degrees means

A

0.0 cosine aka 0 doppler shift

85
Q

angle 0 degrees means

A

1 cosine

86
Q

60 degrees means

A

0.5 cosine

87
Q

error in calculated flow speed increases with what?

A

with angle

the higher the angle, the higher the error

88
Q

doppler shift measurements aren’t reliable at angles greater than

A

60 degrees

89
Q

color doppler displays present information on?

A

the presence, direction, speed, and character of blood flow and on the presence, direction, and speed of tissue motion

presents 2d, cross-sectional, real-time blood flow or tissue motion

presents anatomic information in gray-scale form and detects doppler-shift frequencies at several locations along each scan line

is an extension of gray-scale sonography

90
Q

presentations of doppler info

A

audible
color-Doppler
spectral Doppler
strip chart recording

91
Q

color doppler principle

A

if an echo has a different frequency from that emitted, a doppler shift has occured

a 90 degree doppler angle yields no doppler-shift on vessels

phasing is used to steer the pulse

all pulses are steered at the same angle, resulting in a a parallelogram presentation

92
Q

autocorrelation

A

math technique used in signal processor to detect doppler-shift echoes

determines the mean and variance of the doppler shift signal at each location along the scan line

typically 100-400 doppler samples per scan line are shown

a 3-pulse minimum is required for one speed estimate

more pulses improve the accuracy of estimates or to improve detection of slower flow

93
Q

color controls

A

gain

color window location

width and depth

steering angle: permits avoidance of 90 degree angle

color-map inversion: alternates the color assignments on either side of the doppler shift baseline on color map

wall filter: eliminates clutter caused by tissue and wall motion

priority: selects gray-scale echo strength below which color will be shown at pixel location

baseline shift: allows shifting the baseline up or down to correct aliasing

velocity range (PRF): controlled by operator, sets the PRF and the limit at color bar extremes, low value permits slower flows to be viewed but high probability of aliasing for faster flows

color map selection

variance

smoothing: aka persistence, provides frame to frame averaging to reduce noise

ensemble length: is the number of pulses used for each color scan line, min is 3, 10-20 are the most common, higher lengths give better estimates of mean doppler shifts but lowers FR

94
Q

average attenuation for each centimeter in soft tissue is?

A

0.5 dB

95
Q

color-doppler limitations

A

it’s angle dependent

lower FR bc several pulses per scan line are required

lack of detailed spectral info

max permissible FR is:
max FR = 77,000 cm-s / pen x LPF x ensemble length

96
Q

max permissible FR for color-doppler?

A

max FR = 77,000 cm-s / pen x LPF x ensemble length

97
Q

doppler shift displays

A

hue represents the sing of the doppler shift

changes in hue, saturation, or luminance up or down represents high doppler shift magnitude

change in the hue from left to right on map represents variance

98
Q

the doppler detector in color-doppler yields what?

A

the sign mean, variance, amplitude, and power of the doppler spectrum

99
Q

need help with angle

A

help

100
Q

other names for doppler power

A

power doppler, color power doppler, color-doppler energy, ultrasound angio, power angio

101
Q

doppler power displays

A

present 2D doppler info by color-encoding the strength of the doppler shifts

assigns color values to doppler shift power values

the power of doppler shifts is determined by the concentration of moving scatterers producing doppler shifts

102
Q

pros and cons of doppler power

A

pros:
free of aliasing
not angle dependent
more sensitive to slow flow and small/deep vessels bc lower PRF can be used

con:
shows only the presence of flow

103
Q

spectral doppler displays

A

two types: CW and PW

used to image the heart and vessels

CW and PW present information in an audible and visual form corresponding to scatterer motion

104
Q

PW spectral doppler

A

can use range gating

usually combined with gray-scale (called duplex scanning)

105
Q

range gate definition

A

PW doppler has the ability to select information from a particular depth along the beam

106
Q

bidirectionality

A

if the instrument can distinguish between positive and negative doppler shifts

107
Q

CW spectral doppler

A

has 2 crystals or groups of crystals (one transmits constantly and the other listens constantly)

has CW oscillator and a doppler detector that detects doppler shifts

108
Q

components of CW doppler system

A

oscillator

receiving crystal that produces voltages with frequencies equal to the returning echoes’ frequencies

the RF amplifier that increases the echo voltage amplitude

doppler detector

audio frequency amplifier that strengthen this different frequency

the phase quadrature detector

109
Q

oscillator

A

part of the beam former for CW that produces a continuously alternating voltage that drives the source crystal

2-10 MHz

110
Q

doppler detector

A

part of the signal processor

in the mixer, the sum and difference between the two frequencies is calculated

the filter removes the sum and leaves the difference which is the doppler shift frequency
echo frequency-oscillator frequency

111
Q

phase quadrature detector

A

determines the direction and separates doppler shift voltages into separate reverse and forward channels

positive and negative doppler shifts are heard separately

voltages are sent to display

112
Q

positive shifts=

A

toward the probe beam

113
Q

negative shifts=

A

away from the probe beam

114
Q

when angled 90 degrees, the doppler shifts are

A

equally positive and negative so they cancel each other out

115
Q

angle incorporation or correction

A

must be accurate to correctly display the doppler shift speed vs time

angles at 30-60 degrees are best

most common is 60

116
Q

wall filter

A

aka thump filter

rejects frequencies below a value

is used to remove clutter

adjustable over ranges of 25-32,000 Hz

117
Q

what’s high intensity and has low frequency doppler shifts?

A

vessel wall or cardiac valve motion

118
Q

pulsed-wave operation

A

pulser generates pulses 5-30 cycles long

echoes are processed in detector in which they’re amplified and doppler shifts determined

119
Q

range gating

A

based on the echoes arrival time, echoes at a certain depth can be selected by the amplifier gate

enables depth selectivity and a smaller Doppler sample

operator controls gate length and location

120
Q

longer gate lengths are used for what?

A

for searching for desired vessel and flow location

121
Q

what determines the Doppler sample volume?

A

beam width at the sample volume depth,
gate length,
emitted pulse length

1/2 of a pulse length is added to gate length

122
Q

spectral analysis

A

visual picture of what listeners hear from the loudspeaker

provides a more useful way to present doppler information visually

is in the form of a Doppler frequency spectrum

123
Q

shorter wavelengths are used for what?

A

for spectral analysis and evaluation

improves spectral display quality

124
Q

frequency spectrum

A

the breaking up of the frequency components of a wave/signal and putting them in order of increasing frequencies

125
Q

define spectrum

A

an array of components of a wave, separated and arranged in order of increasing frequency

126
Q

fast fourier transform

A

is the math technique the system uses to derive the Doppler spectrum from the echoes

can show spectral broadening

127
Q

spectral displays

A

the amplitude/power of each doppler shift is presented as brightness

displays presentation of doppler spectra vs time aka doppler shifts vs time

doppler signal power is proportional to blood cell concentration

128
Q

doppler spectra

A

doppler shift on horizontal axis

Power or Amplitude of each frequency on the vertical axis

in venous flow, the display is constant

129
Q

spectral broadening

A

indicative of disturbed or turbulent flow (bc of their high variation of velocities) and can be related to a stenosis

can also be made by excessive doppler gain or excessive sample volume length or beam spreading (with wide aperture arrays)

130
Q

downstream

A

distal

131
Q

upstream

A

proximal

132
Q

tardus-parvus waveform

A

is typical of flow with proximal stenosis

133
Q

typical ranges for vascular?

flow speed, angles, operating f, doppler shift

A

flow speed: 10-100 cm/s

doppler angles: 30-60 degrees

operating frequency: 2-10 MHz

doppler shift: 100 Hz-11 kHz

134
Q

flow is a ___ term

A

volumetric term

volume/time

135
Q

another word for ensemble

A

packet

136
Q

smaller angle means

A

better angle

137
Q

the nyquist criterion is

A

1/2 the PRF

138
Q

pros and cons of CW

A

pro: peak velocity obtainable bc CW has no nyquist limit
cons: no ability to do range gate

139
Q

pros and cons of PW

A

pro: range discrimination (we can determine the depth)

nyquist limit and aliasing are cons

140
Q

in spectral displays, the thickness of the mountains are called what

A

envelope

the thickness means the range of velocities

which is why spectral broadening means it’s detecting tons of different velocites/frequencies

141
Q

when pressure decreases, velocity ____.

A

increases

142
Q

the highest velocity occurs when?

A

during peak systole

143
Q

_____ is represented on the horizontal or “x” axis on a spectral Doppler trace.

A

time

144
Q

Peak systole corresponds to the:

A

highest velocity in the waveform

145
Q

ΔF = +/- [(2 * v * fo) / c] * Cos θ

The symbol “delta F” in the Doppler equation represents which of the following?

A

Doppler shift

146
Q

The Nyquist limit is equal to ____ the PRF.

A

One half

147
Q

True or false? The Doppler effect is the change in the frequency of sound reflected off a moving target.

A

True

148
Q

ΔF = +/- [(2 * v * fo) / c] * Cos θ

The symbol “fo” in the Doppler equation represents which of the following?

A

Transmitted frequency

149
Q

True or false? Color Doppler provides accurate quantitative information regarding blood-flow velocities.

A

False

150
Q

True or false? There is no spectral window on a continuous wave spectral Doppler graph.

A

True

151
Q

Aliasing is a Doppler artifact that is characteristic of ____ systems.

A

Pulse wave

152
Q

An advantage of continuous wave Doppler would be:

A

No Nyquist limit to the maximum velocity the system can record

153
Q

True or false? Spectral Doppler provides accurate quantitative information regarding blood flow velocities.

A

True

154
Q

The brightness of the spectral trace at any point on a spectral histogram represents:

A

The number of red blood cells traveling at that particular velocity at that point in time

155
Q

Techniques to minimize/eliminate aliasing include all of the following except:

A

Reduce the overall gain

156
Q

In the BART system of display, red signifies flow in which direction?

A

Flow detected moving towards the probe

157
Q

A stenosis is defined as a/an:

A

Abnormal luminal narrowing

158
Q

True or false? The sample volume is used to provide the Doppler angle information the system uses to calculate velocities.

A

False

159
Q

True or false? A stenotic region in a vessel or across a valve causes blood flow acceleration.

A

True

160
Q

The volumetric flow rate equation (Q = ?/?) relates which two of the following parameters?

A

A and B

pressure difference and resistance

161
Q

What flow is associated with severe stenosis?

A

Turbulent

162
Q

The standard for display on a spectral Doppler trace is _____.

A

Velocity

163
Q

True or false? Aliasing on a spectral Doppler trace does not interfere with accurate velocity measurements.

A

False

164
Q

True or false? It is always necessary to make the color box as wide as possible in order to optimize color Doppler sensitivity.

A

False

165
Q

True or false? The range gate of the pulsed Doppler system is usually placed close to the vessel wall and away from the center stream, in order to obtain the fastest flow profile.

A

False

166
Q

In the BART system of display, blue signifies flow in which direction?

A

Flow detected moving away from the probe

167
Q

The wall filter control for spectral Doppler is used to:

A

Eliminate low velocity echoes from the spectral trace

168
Q

ΔF = +/- [(2 * v * fo) / c] * Cos θ

The symbol “v” in the Doppler equation represents which of the following?

A

Velocity of the red blood cells

169
Q

The cosine of 90° is ____.

A

0

170
Q

True or false? Normal flow in a blood vessel is usually described as laminar flow.

A

True

171
Q

True or false? The technique for color flow display known as power angio, is more sensitive to low flow states than Doppler.

A

True

172
Q

True or false? The term antegrade refers to the normal direction of flow for a particular blood vessel.

A

True

173
Q

True or false? The Doppler shifted frequency is directly proportional to blood flow velocity.

A

True

174
Q

True or false? Spectral broadening occurs when there is a widening of the spectral envelope and filling in of the spectral window.

A

True

175
Q

True or false? Flash artifact is a spectral Doppler phenomenon.

A

False

176
Q

ΔF = +/- [(2 * v * fo) / c] * Cos θ

The symbol “c” in the Doppler equation represents which of the following?

A

Speed of sound in soft tissue

177
Q

ΔF = +/- [(2 * v * fo) / c] * Cos θ

The “Cos theta” in the Doppler equation represents which of the following?

A

Doppler angle

178
Q

True or false? For cardiac applications an angle of 20 degrees or less is acceptable for spectral Doppler studies.

A

True

179
Q

True or false? The term retrograde refers to reverse flow detected in a particular vessel.

A

True

180
Q

True or false? A spectral analysis graph is a histogram that relates velocity or frequency shift with time and allows accurate measurement of peak velocities.

A

True

181
Q

True or false? The ultrasound PRF is determined by the voltage PRF applied to the transducer element.

A

True

The ultrasound pulse repetition frequency is equal to the voltage pulse repetition frequency of the pulser.

182
Q

Causes of disturbed flow include which of the following?

A

Tortuous vessel
Vessel widening
Vessel branching

183
Q

What flow is associated with severe stenosis?

A

Turbulent

184
Q

The color Doppler display pattern that would accurately depict a normal physiologic flow in a normal vessel would be:

A

Brighter colors toward the center of the vessel with darker colors seen peripherally

185
Q

what does the black band above and below the baseline represent in spectral display?

A

the signals attenuated by the wall filters

186
Q

what’s the assumed Doppler angle in cardiac?

A

0 degrees

187
Q

what does insonification angle mean?

A

doppler angle

188
Q

color doppler yields what?

A

velocity information

189
Q

work

A

total energy expended

power x time

190
Q

poiseuille’s law deals with what kinds of tubes?

A

with long straight nonstenosis vessels

diameter of the entire vessel

191
Q

continuity rule deals with what kinds of tubes?

A

with the diameter of a short section of the vessel

192
Q

recommended angles for color doppler?

A

30-60 degrees

193
Q

color flow

A

color doppler

194
Q

where are the sing, mean, and variance of the Doppler signals stored?

A

addresses that correspond to anatomic locations.

195
Q

BART

A

blue away, red towards

196
Q

RABT

A

red away, blue towards

197
Q

make the color box only as ___ as necessary

A

only as big as necessary

bc the larger it is, the lower the FR will be

198
Q

velocity range

A

aka scale

adjust color PRF for Doppler signal

199
Q

sector arrays are sent out in different directions so color has _____.

A

different Doppler angles

200
Q

what is the best angle for gray-scale imaging?

A

90 degrees

201
Q

what is the best angle for Doppler?

A

0 degrees

Sono 2343 (8 decks)

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