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Helpful Notes Flashcards

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1
Q

What does propagation speed depend on?

A

medium, not frequency

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2
Q

As stiffness increases, what happens to the propagation speed?

A

Propagation speed increases

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3
Q

As density increases, what happens to the propagation speed?

A

Propagation speed decreases

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4
Q

What is a typical wavelength in U/S?

A

0.1-0.8 mm

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5
Q

What is the typical intensity in U/S?

A

0.01-100 mW/cm2

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6
Q

What is the unit of impedence?

A

rayls

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7
Q

What occurs if impedence between 2 media are the same?

A

all transmission, no reflection

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8
Q

what happens to PRF if depth increases?

A

decrease PRF

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9
Q

What is DF in U/S typically?

A

1% or less

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10
Q

What are determined by the medium?

A
  • propagation speed

- impedence

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11
Q

What is determined by both propagation speed and the medium?

A
  • wavelength

- SPL

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12
Q

What does one need to know to determne attenutation?

A

rate (Ac) and path length (L)

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13
Q

what is the average rate of attenuation in U/S?

A

0.7 dB/cm

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14
Q

is specular or non specular angle dependant?

A

specular

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15
Q

In rayleigh scatter, what happens to intensity if frequency increases?

A

intensity increases 4x

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16
Q

How is temporal average determined?

A

pulse average x DF

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17
Q

What is the typical thermal bioeffects setting?

A

SPTA

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18
Q

What can a hydrophone measure?

A
  • PD
  • PRP
  • T
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19
Q

what are scan lines?

A

pulses that RETURN from tissues

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20
Q

What is sensitivity?

A

the ability of a system to display low level or weak echoes.

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21
Q

What does spatial resolution refer to?

A
  • Lateral res
  • Axial res
  • Elevational res
  • Contrast res
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22
Q

What material is used for backing material?

A

resin, Tungsten

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23
Q

What material is used for elements/crystals?

A

PZT

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24
Q

What does resonating frequency depend on?

A

thickness of the element and propagation speed of the element

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25
Q

How many volts does a ultrasound machine produce to drive piezoelectric elements?

A

10-500 V

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26
Q

How many individual elements do modern scanheads contain?

A

more than 100

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27
Q

Is a higher or lower Quality Factor better?

A

lower

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28
Q

Do CW have high or low Q Factors?

A

high becuase they do not have damping

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29
Q

What is quality factor?

A

How near to the actual operating frequency is the bandwidth

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30
Q

What is another name for lateral resolution?

A

Azimuthal resolution

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31
Q

Do most transducer have better axial or lateral resolution?

A

Axial

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32
Q

How is elevational resolution most commonly focused?

A

with a lens

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33
Q

What is the minimum FR that needs to be maintained or the image will flicker?

A

15 Hz

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34
Q

what are 3 adjustments that alter FR?

A
  • image depth (PRF)
  • number of focal zones
  • number of scan lines per frame (line density)
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35
Q

How is PRF related to FR?

A

directly

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36
Q

binary

A

0’s and 1’s

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37
Q

Bistable

A

black and white image

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38
Q

Bit

A

smallest unit of memory in a digital device

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39
Q

Byte

A

8 bits if memory

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40
Q

Pixel

A

smallest component of a 2D digital image

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41
Q

voxel

A

smallest component of a 3D image

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42
Q

what does the scan converter consisit of?

A
  • A-D converter
  • computer memory
  • D-A converter
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43
Q

what is subdicing?

A

dividing the peizoelectric elements into very small pieces to reduce grading lobes

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44
Q

Analog

A

dimmer switch, infinite

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45
Q

Digital

A

On/Off switch, finite

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46
Q

Is it better to have more pixels or more shades of gray?

A

more pixels=better spatial resolution

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47
Q

What transducers produce grating lobes?

A

linear transducers

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48
Q

Where is flash artifact seen?

A

movement of tissue in POWER doppler

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49
Q

What is inertia?

A

Newton’s principle that states an object in motion stays in motion unless acted on by an outside force.

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50
Q

What is Ohm’s law?

A

A law used in electronics in which flow is equal to the pressure divided by the resistance.

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51
Q

What is an oscillator?

A

the component of a CW doppler device that produces the voltage that drives the transducer

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52
Q

What is persistence?

A

the averaging of colour frames in order to display blood flow with a low signal-noise ratio.

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53
Q

What is poiseuilles law?

A

law that describes the relationship of resistance, pressure, and flow.

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54
Q

How is power doppler determined?

A

amplitude mode, brightness is determined by amount of RBC.

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55
Q

What cross sectional area percentage is considered to be hemodynamically significant?

A

75%

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56
Q

What diameter reduction percentage is considered to be hemodynamically significant?

A

50%

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57
Q

What are the advantages of PW over CW for spectral?

A
  • ability to select a specific depth to sample by utilizing range gate
  • ability to angle correct to calculate velocity
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58
Q

Are autocorrelation or FFT’s more accurate?

A

FFT

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59
Q

Does more white make a color more or less saturated?

A

less saturated.

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60
Q

What type of signal does flowing blood typically produce?

A

low amplitude, high velocity signal.

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61
Q

what is mechanical index?

A

the calculation used to identifty the liklihood that caviation will occur.
MI<0.4

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62
Q

What is thermal index?

A

the calculation used to predict the maximum temperature elevation in tissues as a result of attenuation of sound
TI<2

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63
Q

What documentation of U/S images should it include?

A
  • pt’s name
  • facilty info
  • date of exam
  • image orientation
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64
Q

What should the post examination worksheet include?

A
  • pt’s name
  • date of exam
  • type of exam
  • relevant clinical info
  • ICS 9 code (ACC)
  • name of patients healthcare provider and contact info.
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65
Q

What is the definition of communication?

A

transfer of information from one person to another.

66
Q

What is anaphylactic shock?

A

allergic reaction leading to vasodilation and pooling in peripheral blood vessels.

67
Q

What is cardiogenic shock?

A

failure of the heart to pump the proper amount of blood to vital organs.

68
Q

What is distributive shock?

A

When blood vessels lack the ability to constrict and assist in the return of blood to the heart, leading to pooling in the periphery.

69
Q

What is hypovolemic shock?

A

when the amount of intravascular fluid decreases by 15-25%

70
Q

What is neurogenic shock?

A

loss of the sympathetic pathologic conditions that interfere with the normal pumping action of the heart.

71
Q

What is obstructive shock?

A

results from pathologic conditions that interfere with the normal pumping of the heart.

72
Q

What is septic shock?

A

There is an immune responce of thre body that leads to capillary permeability and vasodilation.

73
Q

What are the 3 categories of distributive shock?

A
  • anaphalytic
  • septic
  • neurogenic
74
Q

Are frequencies higher in Doppler or B-mode imaging?

A

frequency for doppler is lower than for B-mode imaging.

This is because sound attenuates when looking at color compared to just tissue.

75
Q

What receiver function is responsible for decreasing the difference between the smallest and largest received signal amplitudes?

A

Compression

76
Q

Is gray scale map assessment pre or postprocessing?

A

postprocessing

77
Q

The technique of frame averaging (persistence) during real-time acquisition is designed to:

A

Reduce random noise

Persistence reduces speckle

78
Q

What is one of the main advantages of harmonics?

A

improves contrast resolution

79
Q

How is contrast resolution always improved?

A

increasing frequency

80
Q

Interpolation is used to fill in the missing data between scan lines in what?

A

both grayscale and color doppler

81
Q

To generate a sonographic image, what is the order in which the following system components are activated?

A
  • Pulser
  • Beam Former
  • Reciever
  • Memory
  • Display
82
Q

What is a typical frame rate for B-mode real-time imaging?

A

10-50 Hz

83
Q

What control could you adjust to improve the signal-to-noise ratio on the image?

A

Frame averaging (persistence)

84
Q

Define Duty Factor

A

the fraction of time that the transducer is activly transmitting sound

85
Q

If you increase the pulse repetition frequency and leave all other controls unchanged, what will happen to frame rate?

A

frame rate will increase

86
Q

What does increasing dynamic range do to contrast resolution?

A

decreases contrast resolution

87
Q

Does increasing PRF decrease frame rate?

A

no

88
Q

What is compression opposite of?

A

dynamic range

89
Q

What is the difference between compression and dynamic range?

A

compression-decreases the range of signal amplitudes present

Dynamic range-the series of echo amplitudes present within the signal

90
Q

Increasing the number of acoustic scan lines in one frame improves what?

A

lateral resolution

91
Q

What component is necessary for a real-time B-mode scanner but is not present in an A-mode scanner?

A

scan converter

92
Q

A digital scan converter is another name for what system component?

A

Image memory

93
Q

Where are images stored in the ultrasound system?

A

scan converter

94
Q

What three colors are used on a color monitor to produce the range of available colors?

A

red
green
blue

95
Q

When you “freeze” the ultrasound image, where is the echo information stored?

A

scan converter

96
Q

What type of resolution is determined by the number of pixels in the scan converter?

A

spatial resolution

97
Q

What is the order in which the signal travels in the ultrasound system?

A

Transducer
Reciever
Scan converter
Display

98
Q

You are imaging a 3D data set that has anisotropic resolution. What does this mean?

A

Unequal resolution is present between imaging planes.

99
Q

What is another name for spatial compounding?

A

compound imaging

100
Q

While scanning a curved structure, you notice shadowing at the lateral edges of the structure. What is required for this artifact to occur?

A

Different media propagation speeds

101
Q

What are the artifacts of reverberation?

A
  • comet tail
  • ring down
  • ?
102
Q

When you select spatial compound imaging which artifacts will it eliminate?

A
  • refraction
  • shadowing
  • enhancement
  • acoustic speckle
103
Q

What results in banding?

A

incorrect TGC

when there are areas of brightness and darkness in different depths of the image

104
Q

Which artifact is associated with resonance of a gas bubble?

A

ring down

105
Q

Which of the following helps to improve the lateral resolution in a B-mode image?

A

increase aperature

106
Q

What technique reduces grating lobes?

A

tissue harmonic imaging

107
Q

What technique would be most likely to produce grating lobes in your image?

A

Beam steering

108
Q

A standard for handling and transferring images and medical information between computers is:

A

DICOM

109
Q

Which artifact is related to the sound beam traveling through a structure with low attenuation?

A

Enhancement

110
Q

What type of focusing is performed by delay circuitry upon reception?

A

dynamic recieve focusing

111
Q

When you select one focal zone, how many pulse/listen cycles are required for each acoustic scan line in one image frame?

A

one

112
Q

define esemble length/packet size?

A

For color doppler, each line of sight must be pulsed multiple times. The number of pulses per line is termed esemble length or packet size.

113
Q

What is velocity estimation in doppler based on?

A

measurement of doppler angle of incidence.

114
Q

What are varience color maps?

A

green color shows turbulence

115
Q

Flash artifact is typically what type of signal?

A

high amplitude, low frequency

116
Q

What does interial losses of fluid energy depend on?

A

changes in flow direction and and changes in blood velocity.

117
Q

When does reynolds number increase?

A

Reynolds number increases with increasing flow speed and enlarging tube diameter.

118
Q

how may a bruit appear on spectral doppler?

A

Seen in an area of post stenotic turbulence. It appears as bright echoes near the baseline located undernath the systolic peak.

119
Q

What two controls affect the spatial resolution of the color image?

A

Frequency and line density

120
Q

What are another names for lateral resolution?

A
  • Angular
  • Transverse
  • Azimuthal
121
Q

What are another names for axial resoltuion?

A
  • longitudinal
  • axial
  • Radial
  • Range
  • Depth
122
Q

What is doppler shift frequency proportional to?

A

velocity of the reflector

123
Q

What is doppler shift frequency dependant on?

A

doppler angle and transducer frequency

124
Q

Transmission of the sound wave from one medium to the next is determined by the media’s _________

A

impedance

125
Q

what is the thickness of the matching layer equal to according to the wavelength?

A

1/4 of the wavelength

126
Q

What pulse wave transducer displays a trapezoidal image?

A

Vector

127
Q

The greater the impedance difference between two structures, the greater the:

A

reflection

128
Q

The speed at which a wave travels through a medium is determined by
what?

A

stiffness and density of the medium

129
Q

What will happen to pressure at a stenosis?

A

preasure will decrease

130
Q

Where is uniform intensity of the sound beam located?

A

In the far field

131
Q

The amplitude of the transmitted and recieved signals is the the responsibility of what?

A

system output

132
Q

The mechanical index is inversely proportional to the:

A

operating frequency

133
Q

How do you fix range ambuigity?

A

PRF should be reduced

134
Q

What is apodization only good for?

A

grade lobes

135
Q

What are doppler shift frequencies in the range of? (infra, audible, ultra)?

A

audible

136
Q

What are the frequency ranges for ultrasound?

A

20 KHz

2-20 MHz

137
Q

The display will generally have a DR smaller or larger than other portions of the ultrasound instrument?

A

smaller

138
Q

Analog voltages occur at the output of the:

A

beam former

transducer

139
Q

Digital signals occur at the output of the:

A

beam former

signal processor

140
Q

Another name for analog

A

proportional

141
Q

Another name for digital

A

discrete

142
Q

What is a tuned amplifier?

A

is simply an amplifier with an electronic filter called the bandpass filter.

143
Q

What is another name for detection?

A

demodulation

144
Q

What is the typical DR of an amplifier?

A

100-120 dB

145
Q

What is the typical DR of a display?

A

30 dB

146
Q

List the lowest to highest intensity values:

A
  • SPTA gray scale
  • M-mode
  • pulsed wave
  • color doppler
147
Q

What is mechanical index inversely related to?

A

operating frequency

148
Q

What is the thickness of the element equal to according to wavelength?

A

1/2 wavelength

149
Q

What are types of transducer construction?

A
  • linear
  • convex
  • annular
150
Q

What are types of transducer operations?

A
  • sequenced
  • phased
  • vector
151
Q

What does focal length also mean?

A

near zone length

152
Q

To improve contrast resoltion what would we do to dynamic range?

A

increase DR (compression)

153
Q

When we decrease DR what happens?

A

more contrast, granier

154
Q

When we increase DR, what happens?

A

less contrast, smoother

155
Q

The impedance of the matching layer is

A

less than that of the crystal and greater than the impedance of the skin

156
Q

What is section thickness related to?

A

beam width

157
Q

What is frame rate determined by?

A

penetration depth and propagation speed of the medium

158
Q

What constitutes a transmission

channel?

A

an independant pulse delay and an element

159
Q

Is contrast resolution or spatial resolution most likely related to pixel density?

A

spatial resolution

160
Q

What is the size of the sample volume determined by?

A
  • beam diamter
  • length of US pulse
  • reciever gate length
161
Q

According to pressure, which direction does blood flow?

A

from higher pressure to lower pressure

162
Q

What does the vertical axis of spectral analysis represent?

A

frequency

Physics Registry (1 decks)

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