Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Echo > Physics > Flashcards

Physics Flashcards

1
Q

Specular reflection

A

Mirror-like
Structures >1 wavelength in diameter
Angle of incidence = angle of reflection

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Specular reflection and frequency

A

Independent of frequency

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Diffuse reflection

A

Omnidirectional
Structures <1 wavelength in diameter
Frequency dependent, more scattering with higher frequency

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Interference

A

Algebraic sum of wave amplitude

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Speckle

A

Noise in US images produced by interference pattern from multiple small reflectors (scatterers)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Refraction

A

Bending of wavefront as sound passes between media with different propagation velocities
Snell’s law

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Snell’s law

A

Sin Angle I / Sin angle T = V I / V T

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Diffraction

A

Spreading or divergence of sound beam

Greater with smaller source

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Absorption

A

Sound energy converted to other forms of energy like heat

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Attenuation

A

Loss of intensity as sound wave passes through medium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Soft tissue attenuation

A

0.5-1.0 dB/cm/MHz

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Resonance

A

Air bubbles resonate within ultrasound field, ring like a bell
Persistent oscillation produces continued ultrasound signal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Nonlinear behavior

A

Distortion of sound wave by interaction with media

Can be described as sum of sine waves at frequencies that are multiples of principle frequency (harmonics)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Harmonics generated strongly by

A

Microbubbles

Compression and expansion not equal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Harmonic generated weakly by

A

Tissue

Velocity of sound higher during compression than rarefaction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Transducer components

A

Piezoelectric crystal
Backing block
Quarter-wavelength matching layer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Piezoelectric crystal

A

Vibrates with applied current, most efficient at resonant frequency
Transmitter and receiver

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Backing block

A

Limits ringing of crystal to create discrete US pulses

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Quarter-wavelength matching layer

A

Provides better acoustic impedance matching between crystal and skin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Mechanical transducer

A

Controlled movement of single element to produce 2D image

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Phase array transducer

A

Multiple crystal elements to produce 2D or 3D image

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Narrow bandwidth transducer

A

High Q factor
Crystals allowed to ring freely
More efficient / sensitive

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Wide bandwith transducer

A 
Low Q factor
Wide range of frequencies sent and received 
Backing block, crystal impurities
Short pulses
Facilitates harmonic imaging
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Continues imaging

A

Continuous
Separate send and receive transducers
CW doppler

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Pulsed imaging

A

Single transducer alternately sends and receives
PW doppler
Grayscale imaging
Colorflow imaging

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Colorflow pulsed imaging methods

A

Autocorrelation method

Time domain method

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Colorflow autocorrelation method

A

Compares frequency differences from sequential pulses

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Colorflow time domain method

A

Measures distance objects move between pulses separated in time by PRP
Velocity = change in distance./ PRP

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

Pulse repetition period

A

Time between pulses

Directly related to imaging depth

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

PRP Equation

A

PRP = depth * speed of sound

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Pulse repetition frequency

A

Inversely related to PRP and imaging depth

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

PRF Equation

A

PRF = 1 / PRP

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

Duty factor

A

Fraction of PRP that transducer is emitting sound

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

CW doppler duty factor

A

1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

Pulsed techniques duty factor

A

<1 (usually 0.001 to 0.01)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

Duty factor equation

A

Pulse duration(s) / PRP (s)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

Pulse duration

A

Time from start of a pulses to end of a pulse

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

Second harmonic imaging

A

Single sent out at nominal frequency, filter processes signals returned at 2f which are displayed as image

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

Types of resolution

A

Temporal
Contrast
Spatial

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

Temporal resolution

A

Ability to see object as it moves over time

How often you can see something

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

Temporal resolution determined by

A

Fram rate (frames / sec)
Depth
Line density
Use of multiple beam formers increase frame rate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

Improving temporal resolution

A

Decrease image depth
Decrease image display width
Decrease # of focal points
Decrease line density

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

Contrast resolution

A

Ability to see differences in gray scale

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

Contrast resolution dependent on

A 
Intrinsic properties
Frequency
Gain
Compression
Color
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

Types of spatial resolution

A

Axial

Lateral

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

Axial resolution

A

Discern two objects in line of US beam

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

Axial resolution determined by

A

Spatial pulse length (set by manufacturer)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

Axial resolution improved by

A

Higher frequencies

Fewer cycles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

Axial resolution equation

A

(Cycles x wavelength) / 2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
50
Q

Lateral resolution

A

Discern two objects across image

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
51
Q

Lateral resolution better with

A

Narrower beam

Use of focal point, near field

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
52
Q

Ultrasound beam focusing

A

Mechanical beam focusing
Electronic beam focusing
Multiple focal zones

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
53
Q

Mechanical beam focusing

A

Fixed, acoustic lenses, shaped crystals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
54
Q

Electronic beam focusing

A

Dynamic, delay in firing central elements

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
55
Q

Multiple focal zones

A

Separate scan lines for each zone, images electronically spliced
Poor frame rate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
56
Q

Side lobes

A

Single element adjacent to main beam

57
Q

Grating lobes

A

Phased array lobes adjacent to main beam

58
Q

Echo ranging

A

Distance of object from transducer determined by time of flight and velocity (assumed 1540 m/s)

59
Q

Echo ranging equation

A

d = 1/2t * v

60
Q

Echo ranging 1 cm

A

13 usec

61
Q

Transducer Output Power

A

Energy put out by machine (MI or dB)

62
Q

Higher transducer output power =

A

better signal to noise ratio

destroy contrast bubbles

63
Q

Amplification

A

Received signals made larger or smaller to optimize appearance
Noise and signal amplified
No effect on signal to noise ratio or bubbles

64
Q

Gain compensation

A

Corrects amplification for signal loss due to depth related attenuation (time-gain compensation)
or unequal signal strength across image (lateral-gain compensation)

65
Q

Compression

A

First information into display’s capacity

66
Q

Reject

A

Filters low or high intensity signal to improve image quality

67
Q

Wavelength

A

Distance between wave peaks

68
Q

Frequency (f) =

A

Number of waves / s (Hz)

69
Q

Ultrasound frequency

A

Above audible range (>20,000 Hz)

70
Q

Diagnostic US frequency range

A

1-20 MHz

71
Q

Velocity of sound

A

Varies with density and compressibility of medium

72
Q

Average soft tissue velocity of sound

A

1540 m/s

73
Q

Wave equation

A

Velocity = frequency x wavelength

74
Q

Wavelength of 3 MHz sound

A

0.5. mm in soft tissue

75
Q

Frequency and wavelength

A

Higher f = shorter wavelength

76
Q

Ultrasound signal strength

A

Ampltiude
Power
Intensity

77
Q

Amplitude

A

Difference between max and min value of wave

78
Q

Power

A

Total energy produced each second (watts)

79
Q

Intensity

A

Power / cross-sectional beam area (W / cm2)

80
Q

Decibel (dB)

A

Units for describing difference between US intensities

81
Q

dB equation

A 
dB = 10 log (I / I0)
I = measured intensity
I0 = defined reference intensity
82
Q

3 dB change

A

Doubling in intensity

83
Q

30 dB change

A

1000 fold change in intensity

84
Q

100 d change

A

10^10 times more intense

85
Q

Mechanical index

A

Measure of potential to produce cavitation (formation f bubbles)

86
Q

MI equation

A

MI = peak negative pressure / sqrt(f)

87
Q

Bubbles destroyed when MI

A

> 1

88
Q

Harmonic signals weak when MI

A

<0.1

89
Q

Acoustic impedance

A

Product of density (p) and velocity of sound (v) in medium
Differences between acoustic impedances directly related to % reflection
Z = p v

90
Q

Nyquist Limits (DF)

A

Highest doppler shift (velocity) that can be measured with pulsed doppler

91
Q

Nyquist Limit equation

A

DF = PRF / 2

92
Q

Higher Nyquist limit

A

Shallower depth

Lower frequency

93
Q

Velocities above Nyquist limit

A

Alias or wrap around, displayed as opposite direction

94
Q

Doppler effect

A

Frequency shift caused by relative motion between source and target

95
Q

Doppler shift increased by

A

Velocity of sample relative to source
Interrogation angle
Frequency of source

96
Q

Doppler shift decreased by

A

Velocity of sound in the medium

97
Q

How to raise nyquist limit

A

Decrease depth

No effect of sector width or range gate size

98
Q

How to decrease doppler frequency shift

A

Reduce transducer frequency (f0)

99
Q

Frequency means

A

Number of time particle in conducting medium vibrates per unit time

100
Q

Frequency vs period

A

Frequency = 1 / period

101
Q

Tissue with fastest loss of strength

A

Lung

102
Q

Materials that respond to acoustic waves and generate electrical signals

A

Piezoelectric crystals

103
Q

Doppler angle

A

Angle between the direction of flow and the ultrasound beam

104
Q

Doppler effect, higher frequency / pitch

A

Object moving towards you

105
Q

Positive doppler shift

A

Reflector moving so that angle between transmitted beam and direction of flow > 90 degrees

106
Q

Doppler shift of 0

A

Reflector is stationary or moving in direction perpendicular to the beam

107
Q

Time gain compensation corrects for different media…

A

Attenuation

108
Q

Attenuation is sum of

A

Scattering
Absorption
Reflection

109
Q

Strength of transmitted sound wave controlled by

A

Power control

110
Q

Control for what extent received signal is amplified

A

Gain control

111
Q

Compression

A

determines dynamic range of received signals used to create image

112
Q

Spatial resolution means

A

Smallest distance between two objects that allows distinction between them

113
Q

Spatial resolution =

A

Size of a pixel in the relevant direction

114
Q

Temporal resolution definition

A

Shortest time between two events that allows distinction between them
Shortest duration of event that can be detected

115
Q

Temporal resolution =

A

inverse of frame rate

116
Q

Dynamic range adjusted by

A

Compression control

117
Q

Frequency and depth

A

Higher frequency = smaller depth

118
Q

Increase to compensate for attenuation

A

Gain

119
Q

Decreasing what = better contrast

A

Dynamic range / compression

120
Q

Ghosting artifact

A

When imaging higher velocity regions, movement of cardiac structures produces low velocity signals which appear as color

121
Q

Removes ghosting artifact

A

Filtering

122
Q

Time gain compensation and depth

A

Decreases signal in near field, increases in far field

123
Q

Better assess rapid structures

A

Higher frame rate
Narrowing sector
Decreasing depth

124
Q

Decreasing aliasing

A

Baseline shift away from direction of flow

125
Q

Persistence

A

Images averaged together to create smoothing effect

Lower = better temporal resolution

126
Q

Image resolution improved by

A

Increase the write zoom
Reducing sector width
Changing focal point

127
Q

Increasing line density effect

A

Improves spatial resolution

Decreases frame rate and temporal resolution

128
Q

Higher frequency and spatial resolution

A

Better spatial resolution

129
Q

Increase frame rate by

A

Decreasing depth

Reducing sector angle

130
Q

Reducing sector angle

A

Reduces scan lines -> higher frame rate

131
Q

M mode features

A

US reflections along single line over time
Higher temporal resolution
Simultaneous visualization of structures

132
Q

Spectral doppler features

A

Displays power spectrum of velocities along single line over time

133
Q

Rationale for echo contrast

A

Increased reflection by added gas-liquid interface

134
Q

Acoustic shadowing with contrast

A

Increased attenuation by contrast filled cavity

135
Q

Higher sweep speed

A

Detailed time estimates

136
Q

Lower sweep speed

A

Multicycle events like respiratory variation

137
Q

Higher harmonics ->

A

Reduces near field, enhances far field

138
Q

Smoothing

A

Averaging adjacent pixels to create a smoother image

Echo (30 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions