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Ultrasound Physics > Exam 3 Flashcards > Flashcards

Exam 3 Flashcards

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1
Q

What is the relationship of the diameter of the transducer and the divergence angle

A

Inversely related
Large Dia, small angle
Small dia, large angle

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2
Q

High frequency will create a beam with

A

Deep foci

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3
Q

T or F:
High frequency causes beam to attenuate more

A

True

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4
Q

Large diameter crystals create beam with ____ (Deep or Shallow) foci

A

Deeper foci

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5
Q

Pulse waves have _____ pulses and have ____ crystals

A

Short pulses, 1 crystal

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6
Q

CW waves have _____ waves, and have _____ crystals

A

Continuous wave, 2 crystals

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7
Q

What are the pros of CW Doppler

A

Aliasing never happens

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8
Q

What are the cons of CW Doppler

A

Velocity on entire region overlap between receive and transmit beams (Range ambiguity)

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9
Q

What are the instrument controls for CW

A

Transmit power control
Receiver sensitivity or gain control
Wall filter control

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10
Q

Equation for PRP

A

1/PRF

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11
Q

Equation for PRF

A

1/PRP

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12
Q

What is the equation for PD

A

1/frequency

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13
Q

How do we steer a beam

A

Adjust firing times of signal

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14
Q

What is apodization

A

Strength of side and grating lobes are reduced

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15
Q

What is the main purpose of apodization

A

To get rid of side and grating lobes

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16
Q

How can apodization be reduced

A

Sending different electrical spikes to each element

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17
Q

Stronger electrical signals are sent to

A

Center elements instead of sides

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18
Q

What are side lobes

A

Additional areas of sound energy equal to and greater than focal zone exist outside of the main beam

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19
Q

Side lobes are known to reduce

A

Lateral resolution

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20
Q

Side lobes are only located in the

A

Far field

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21
Q

Side lobes are ___% of the main beam

A

14%

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22
Q

Side lobes pulse the beam which will

A

Reduce effects

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23
Q

Side lobes have a single element that produce

A

Sound continuously

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24
Q

What are grating lobes

A

Lobes resulting of array transducer scanning

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25
Q

Grating lobes are located only in

A

Both near and far field

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26
Q

Grating lobes can be reduced by

A

Making tightly packed array elements

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27
Q

What are the pros of a linear switched array

A

Wide linear image

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28
Q

What are the cons of linear switched array

A

Fixed focus
Not able to steer
$$$

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29
Q

Where is linear switched array going to be used

A

Vascular imaging, Doppler, color Doppler

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30
Q

What is mechanical steering

A

Motorized dome over top

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31
Q

What are the pros of mechanical steering

A

Cheap

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32
Q

What are the cons of mechanical steering

A

Fixed focus
Mechanical wear
Motion
Limited temporal range

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33
Q

Annular array is used in

A

2-D, M Mode Doppler, and color Doppler

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34
Q

What are the pros of annular array

A

Variable focus in lateral and elevational resolution
Depth of field

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35
Q

What are the cons of annular array

A

Mechanical wear
Motion
Temporal resolution
Grating lobes
$$$

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36
Q

When are 1-D phased array sectors used

A

Used in cardiac imaging

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37
Q

What are the main frequency ranges in 1-D phased array sectors

A

2-4MHz

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38
Q

What is the peds frequency range in 1-D phased array sectors

A

5-8MHz

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39
Q

What is the frequency range in small adults and children in 1-D phased array sectors

A

3.5-5MHz

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40
Q

What are the pros of 1-D phased array sector

A

Varable focus
Motion artifacts eliminated
Parallel processing is option

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41
Q

What are the cons of 1-D phased array sectors
Relative to mechanical:
Relative to 2-D:

A

M - $$$, electronics are complicated
2-D - Fixed elevational focus, no elevational dimension

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42
Q

When are 1-D Curved linear arrays

A

2-D, color Doppler, and Doppler

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43
Q

What are the pros of 1-D Curved linear array

A

Variable focus in lateral
Wide linear image in near field
Can do parallel processing

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44
Q

What are the cons for 1-D curved linear arrays
Relative to mechanical:
Relative to 2-D:

A

M - $$$
2-D - Fixed elevation focus, no steering in elevation

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45
Q

2-D arrays can image well in

A

Both lateral and elevational planes

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46
Q

What are the 3 types of transducer

A

Linear
Annular
Convex

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47
Q

Active elements in a straight line

A

Linear

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48
Q

Circle rings

A

Annular

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49
Q

Elements in arched line

A

Convex

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50
Q

What is the shape of linear transducer
What will happen when there’s a dropout

A

Rectangular
1 vertical black line will drop

51
Q

Annular rings acquire date from

A

Shallower depths and the outer from deeper depths

52
Q

What is the shape of annular transducer
What will happen if there’s a dropout

A

Pie
Dropout makes a ring

53
Q

In convex array pulses are sent out

A

Simultaneously but are radial in nature

54
Q

What is the shape of convex array
What will happen if there’s a dropout

A

Windshield shape
Dropout will cause 1 black vertical line

55
Q

What are the 3 methods of focusing

A

External focusing
Internal focusing
Phased array focusing

56
Q

External focusing is the use of

A

Lens

57
Q

Internal focusing is the use of

A

Curved active element

58
Q

Phased array focusing is the use of

A

Onboard electronics to achieve focus

59
Q

What is the relationship of PZT thickness and frequency

A

Inversely related

60
Q

What is the equation for PZT thickness

A

Frequency (MHz) = (Speed of sound in PZT (mm/us) / 2 x Thickness (mm)

61
Q

T or F:
Thickness determines pulse wave and continuous wave

A

False
Pulse wave only

62
Q

Thin crystals produce sound pulses with ____ (High or low) frequencies

A

Higher frequencies

63
Q

What are the 2 factors that affect NZL

A

Diameter/apeture of transducer
Frequency of sound produced by transducer

64
Q

A large diameter and high frequency will give you a ____ foci (Shallow or Deep)

A

Deep

65
Q

Small diameter and low frequency will give you a _____ foci (Shallow or deep)

A

Shallow

66
Q

What is the matching layer

A

1/4 of the thickness of matching layer of sound

67
Q

What is LATA

A

Lateral, Angular, Transverse, Azimuthal

68
Q

What is LARRD

A

Long, Range, Radial, Depth

69
Q

What are types of flow

A

Pulsatile
Phasic
Steady
Laminar
Turbulent
Continuity

70
Q

What is pulsatile flow
What is an example

A

Variable velocity flow due to cardiac contraction
Ex. Arterial circulation

71
Q

What is phasic flow
What is an example

A

Variable velocity due to respiration
Ex. Venous circulation

72
Q

What is steady flow
What is an example

A

Constant velocity flow
Ex. When holding one’s breathe

73
Q

What are the 2 types of laminar flow
Define them

A

Parabolic - Average flow is 1/2 of the max,
Plug flow - All layers have same speed

74
Q

What is laminar flow

A

Layered flow, liquid is at different speeds as youn move from vessel wall

75
Q

What is turbulent flow

A

Random/chaotic circles or eddies

76
Q

What is continuity flow

A

Volume flow rate must be constant in the before, at, and after

77
Q

What does continuity flow mean

A

Blood cannot be created or destroyed as it moves through the vessel

78
Q

What is the boundary condition

A

Flow must = 0 at vessel wall

79
Q

What does FFT cause in laminar flow

A

Shoots all ticks to final box

80
Q

What does FFT cause in turbulent flow

A

Shoots ticks all over in different boxes

81
Q

FFT results in more

A

Velocity bins being filled in spectral window (Spectral broadening)

82
Q

What is PI
What is the equation
What are the units

A

Pulsatality index
PI = (Max - Min) / Ave
No units

83
Q

What is the relationship of the sine of an angle and wavelength
Now with frequency and sine of the angle

A

Inversely related
Inversely related

84
Q

What is RI
What is the equation
What are the units

A

Resistivity index
RI = (Max - Min) / Max
No units

85
Q

Technique that is used to quantify and to image the blood flow, in turn would mean we are checking the hearts motion

A

Doppler

86
Q

What is the basic premise of Doppler

A

Relative motion of sound source and observer

87
Q

What are the 3 ways to produce Doppler

A

Sound source moves, listener stays
Sound source stays, listener moves
Sound source and listener move

88
Q

CW Doppler transmits waves used and receive waves that produce

A

Product of 2 signals

89
Q

If you have a large diameter how will that affect your NZL

A

NZL will increase by same amount

90
Q

PW Doppler look at

A

Specific depths (Volume)

91
Q

In PW Doppler there are more:
Results in:

A

More cycles in each pulse
Results in improved sensitivity

92
Q

What is the purpose of the wall filter

A

Remove low frequency signals

93
Q

In color Doppler you are no longer looking at the peak amplitude you are looking at

A

Reflector velocities average

94
Q

What is used to acquire color Doppler

A

Multiple pulse echo sequence

95
Q

In color Doppler if there is a bulid up the signal is going to take____ (More or less) time to be displayed

A

More

96
Q

Power Doppler indicates the presence of

A

Doppler shift

97
Q

Power Doppler does not look at ____ or ____

A

Speed or direction

98
Q

Power Doppler is also known as ____ Mode or color ____

A

Energy mode or color angio

99
Q

What are the pros of Power Doppler

A

Increased sensitivity to low
velocity flow
No aliasing (Velocity is not considered)
Unaffected by Doppler angles but for 90 degrees

100
Q

What are the cons for Power Doppler

A

Can’t know direction
Lower frame rates
Susceptible to motion of patient

101
Q

Aliasing is directly related to
Cuts off

A

PW Doppler
Peak velocity

102
Q

Aliasing causes a cut off in ___
Aliasing causes no cut off in ___

A

PW Doppler
CW Doppler

103
Q

Color percevied by the viewer

A

Hue

104
Q

Hue that is mixed with white

A

Saturation

105
Q

Brightness of saturation

A

Luminance

106
Q

The less white present the greater the

A

Saturation

107
Q

Luminance represents

A

Echogenicity

108
Q

Measuring Doppler with frequency within each pixel associated with a pulse pocket

A

Variance

109
Q

Variance is used as an effective measure to indicate

A

Turbulence

110
Q

Velocity mode for color cannot determine

A

Laminar or turbulent flow

111
Q

What does color red mean

A

Flow toward the transducer

112
Q

What does color blue mean

A

Flow away from the transducer

113
Q

How do you indicate turbulence and laminar flow in color on the screen

A

Laminar is on left side
Turbulent is on right side

114
Q

Describe the relationship between period and frequency

A

Inversely related

115
Q

What is th equation for period

A

1/f

116
Q

What is the equation for frequency

A

1/P

117
Q

Name the powers of 10
1,000,000,000
1,000,000
1,000
0.01
0.001
0.000001
0.000000001

A

10^9 - Giga
10^6 - Mega
10^3 - Kilo
10^-2 - Centi
10^-3 - Milli
10^-6 - Micro
10^-9 - Nano

118
Q

What is the equation for Nyquist Limit

A

PRF/2

119
Q

Name the equations for far field divergence angle

A

Sin0 = 1.2 x wavelength / Diameter
Sin0 = 1.2 x prop speed / Diameter x Frequency

120
Q

Name the equations for NZL

A

Diameter x frequency / 6.16
Diameter^2 x frequency / 6
r^2 / Wavelength

121
Q

What is the equation for RI and PI

A

RI = (Max - Min) / Max
PI = (Max - Min) / Ave

122
Q

What are the equations for Doppler Shift

A

Doppler shift = Reflected Frequency - Transmitted Frequency
Fd = 2fovcos0 / c

123
Q

What is Bernoulli’s Equation

A

Constant = P + 1/2pv^2 + pgh

Ultrasound Physics (6 decks)

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