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Ultrasound Physics > Midterm Review > Flashcards

Midterm Review Flashcards

1
Q

Interfaces that scatter ultrasound energy are usually considered to be those that are equal to or smaller than ________.

A

Wavelength

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2
Q

Interfaces that scatter ultrasound energy are usually considered to be those that are _______ or _______wavelength.

A

Equal to

Smaller than

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3
Q

Regions of lower pressure and density are called ______.

A

Rarefactions

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4
Q

Define rarefactions

A

Regions of lower pressure and density

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5
Q

If you switch to a lower frequency for penetration, the wavelength of the transducer will ________.

A

Increase

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6
Q

Frequency and wavelength are _______ related.

A

Inversely

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7
Q

The attenuation of a 5.0 MHz transducer at a depth of 4 cm is _____.

A

10 dB

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8
Q

What is the formula for attenuation?

A

Total attenuation= attenuation coefficient X depth

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9
Q

What is the formula for attenuation coefficient?

A

Attenuation coefficient= Frequency/2

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10
Q

T or F. The higher the transducer frequency, the higher the Rayleigh scattering.

A

True

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11
Q

Transducer frequency and Rayleigh scattering are ________ related.

A

Directly

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12
Q

T or F. 15 kHz is not a ultrasound frequency.

A

True

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13
Q

The duty factor will increase with:

A

PRP
Pulse duration
Period

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14
Q

The attenuation of a 5 MHz transducer in soft tissue would be ____ dB at 2 cm of depth.

A

5

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15
Q

_____ microsec is the period of a 5.0 MHz transducer in soft tissue.

A

0.2

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16
Q

What is the formula for impedance?

A

Impedance= Density X propagation speed

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17
Q

Density X propagation speed=

A

Impedance

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18
Q

Continuous wave doppler has a duty factor of ______.

A

100%

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19
Q

What has a duty factor of 100% ?

A

Continuous wave doppler

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20
Q

For perpendicular incidence, the incidence angle is ______.

A

90 degrees

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21
Q

The incidence angle is 90 degrees for __________.

A

Perpendicular incidence

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22
Q

T or F. Attenuation decreases with an increase in wavelength.

A

True

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23
Q

Attenuation and wavelength are ________ related.

A

Inversely

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24
Q

The average propagation speed in human soft tissue is ________.

A

1.54 mm/microsec

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25
1.54 mm/microsec is the average propagation speed in ___________.
Human soft tissue
26
Frequency is _______ related to wavelength.
Inversely
27
The distance to a reflector in soft tissue is 15 cm. __________ is the round trip to this depth.
195 microseconds
28
The time it takes for one cycle to occur is _______.
Period
29
What is period?
The time it takes for one cycle to occur
30
In __________ the sound is refracted at a boundary between two media where propagation speeds are different.
Oblique incidence
31
In oblique incidence the sound is refracted at a boundary between two media where propagation speeds are ________.
different
32
_________ relates the transmitted beam direction to the incidence beam direction and the speeds of sound in the two materials forming the interface.
Snell's law
33
The number of pulses that occur in a second is called ______.
Pulse repetition frequency
34
When frequency increases, the period ________.
Decreases
35
The maximum variation that occurs in an acoustic variable is called ___________.
Amplitude
36
Amplitude is _________________________.
The maximum variation that occurs in an acoustic variable .
37
-3 dB of attenuation mean _________ the original intensity.
One-half | Choose best answer on test: Possibly 3dB
38
If beam power increases, intensity will __________.
Increase
39
Beam power and intensity are _______ related.
Directly
40
The speed at which a wave travels through a medium is called _________.
Propagation speed
41
Define propagation speed.
The speed at which a wave travels through a medium.
42
Sound is a _________ wave.
mechanical longitudinal
43
The wavelength of 3 MHz ultrasound in soft tissue is _____.
0.51 mm
44
________ sound is NOT described by pulse duration.
Continuous wave
45
T or F. Continuous wave (CW) is described by pulse duration.
False
46
The number of complete cycles per second is called ________.
Frequency
47
Define frequency.
The number of complete cycles per second
48
As sound travels, the reduction in amplitude and intensity of the wave is called ________.
Attenuation
49
Define attenuation.
The reduction in amplitude and intensity of the wave as sound travels.
50
T or F. The propagation speed is higher in bone than soft tissue.
True
51
Is propagation speed higher in soft tissue or bone?
Bone
52
Sound requires ___________.
a medium through which to travel.
53
Ultrasound pulses contain a range of frequencies called ___________.
Bandwidth
54
What is bandwidth?
Ultrasound pulses with a range of frequencies.
55
Does duty factor have a unit?
NO
56
T or F. Duty factor is unitless.
True
57
T or F. The spatial pulse length does not increase with frequency
True
58
Spatial pulse length and frequency are _________.
Unrelated
59
``` The propagation speed for a round trip time of 39 microseconds is _______ mm/microsecond. 1540.0 15.4 1.45 NONE OF THE ABOVE ```
NONE OF THE ABOVE
60
Examples of acoustic parameters:
Cycle Period Frequency
61
Cycle, period, and frequency are examples of ___________.
Acoustic parameters
62
The fraction of time that pulsed ultrasound is on is called _____________.
Duty factor
63
What is duty factor?
The fraction of time that pulsed ultrasound is on
64
Pulse repetition frequency is the number of pulses occurring in ___ second.
1
65
The number of pulses occurring in 1 second is _________
Pulse repetition frequency
66
What is pulse repetition frequency?
The number of pulses occurring in 1 second
67
T or F. Attenuation is higher in bone than in soft tissue.
True
68
Is attenuation higher is soft tissue or bone?
Bone
69
Is compression an acoustic variable?
NO
70
_________ is not an acoustic variable.
Compression
71
What are the acoustic vatiables?
Pressure Density Distance
72
The best way to describe the role of ultrasound scattering in diagnostic imaging is that ________________________.
It allows us to see the tissue interfaces
73
The distance to the reflector in soft tissue with a round-trip time of 39 microseconds is _______.
30 mm or 3 cm because 1 cm=10mm
74
If the beam area decreases, the intensity will _______.
Increase
75
Beam area and Intensity are ______ related.
Inversely
76
The four intensity values from the greatest to the least are:
SPTP SATP SPTA SATA
77
Heat production depends most directly on the ______________.
temporal average (TA) intensities.
78
__________ depends most directly on the temporal average (TA) intensities.
Heat production
79
Continuous wave ultrasound is described by:
Frequency Wavelength Propagation speed
80
The rate at which energy passes through a unit area is called _______.
Intensity
81
Define intensity.
The rate at which energy passes through a unit area
82
If the density of medium 2 is 10% greater than that of medium 1 and the propagation speeds are equal. The impedance of medium 2 is _____% higher for medium 1.
20%
83
Propagation speed is primarily determined by ___________.
The stiffness of the medium
84
________ is primarily determined by the stiffness of the medium.
Propagation speed
85
What is the units for impedance?
Rayls
86
Rayls is the unit for _______.
Impedance
87
In oblique incidence, the incidence and reflection angles are always ______.
Equal
88
In __________, the incidence and reflection angles are always equal.
Oblique incidence
89
If frequency increases, period will ________.
Decrease
90
Frequency and period is ________ related.
Inversely
91
Stiffer media have ______ sound speeds.
higher
92
T of F. Intensity is equal to the power of a wave divided by the area over which the power is spread.
True
93
Intensity is equal to the __________ divided by the ____________.
Power of a wave | Area over which the power is spread.
94
20kHz is equal to _________.
20,000 Hz
95
500 Hz is equal to
0.500 kHz
96
T of F. Stiffer media have higher sound speeds.
True
97
______ media have higher sound speeds.
Stiffer
98
The ____ of the media determine how much of the incident sound wave is reflected and transmitted into the ________.
Impedances | Second media
99
The impedances of the media determine how much of the ___________ is reflected and transmitted into the second media.
Incident sound wave
100
Attenuation encompasses:
Absorption Scattering Reflection
101
Is spatial pulse length determined by the length of the pulse and the propagation speed?
NO
102
Impedance increases when ______ and __________ increases.
Density | Propagation speed
103
Impedance, density, and propagation speed are ________ related.
Directly
104
Will pulse duration increase with frequency?
No
105
T or F. Pulse duration will increase with frequency.
False
106
Can sound travel through a vacuum?
No
107
Can sound travel through air, lung, and bone?
Yes
108
Spatial pulse length is determined by ________.
Wavelength

Ultrasound Physics (30 decks)

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