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Ultrasound Physics > Sound > Flashcards

Sound Flashcards

0
Q

What are the effects of the soundwave upon the biologic tissue called?

A

Biologic effects

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1
Q

What are the effects of the medium upon the soundwave called?

A

Acoustic propagation properties

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2
Q

What is the type of wave that carries energy, not matter, from place to place?

A

Sound

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3
Q

Areas of increased pressure and density

A

Compressions

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4
Q

Areas of decreased pressure and density

A

Rarefactions

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5
Q

What type of wave is a sound wave?

A

Mechanical, longitudinal

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6
Q

How does sound travel?

A

A soundwave is created by the vibration of a moving object. Sound must travel through a medium, it cannot travel through a vacuum. Sound travels in a straight line.

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7
Q

What identifies which waves are soundwaves?

A

Acoustic variables

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8
Q

What are three acoustic variables?

A

Pressure, density, distance

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9
Q

The concentration of force within an area, force/area.

A

Pressure

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10
Q

What is the unit of measurement for pressure?

A

Pascals (Pa)

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11
Q

What is the concentration of mass within a volume?

A

Density

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12
Q

What is the unit of measurement for density?

A

kg/cm^3

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13
Q

What is the measure of particle motion?

A

Distance

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14
Q

What type of wave’s particles move in a perpendicular direction to the direction of the wave?

A

transverse wave

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15
Q

What type of wave’s particles move in the same direction as the wave?

A

Longitudinal wave

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16
Q

What describes the features of a particular sound wave?

A

Acoustic parameters

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17
Q

What are the acoustic parameters?

A

Period, frequency, amplitude, power, intensity, wavelength, speed

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18
Q

What is the time required to complete a single cycle called?

A

Period

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19
Q

What is the unit of measurement for period?

A

Microseconds, or any unit of time

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20
Q

What is the range of typical values for an ultrasonic wave period?

A

.06 to .5 microsecond

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21
Q

Can the timespan of a period be changed by the sonographer?

A

No, it is determined by the sound source and cannot be changed by the sonographer.

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22
Q

The number of certain events that occur in a particular time duration

A

Frequency

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23
Q

What are the units for frequency in diagnostic ultrasound?

A

Hertz, meaning “per second”

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24
Q

Can the frequency be changed by the sonographer?

A

No, it is determined by the sound source, but cannot be changed by the sonographer.

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25
Q

What are the typical values of frequency in diagnostic ultrasound?

A

2 MHz to 15 MHz

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26
Q

Does frequency affect penetration and axial resolution?

A

Yes, therefore frequency affects image quality.

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27
Q

A wave with a frequency exceeding 20,000 Hz

A

Ultrasound

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28
Q

Wave that can be heard by man, frequencies between 20 Hz and 20,000 Hz

A

Audible sound

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29
Q

Sound wave with frequency less than 20 Hz

A

Infrasound

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30
Q

How frequency and period related to each other?

A

They are reciprocals, an inverse relationship. When frequency increases period decreases and when frequency decreases period increases. When period is unchanged, frequency is also unchanged.

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31
Q

What are the complementary units for frequency and period?

A

Seconds and Hertz

Microseconds and megahertz

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32
Q

What are the three “bigness” parameters; the three parameters which describe a sound beam’s strength?

A

Amplitude, power, and intensity

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33
Q

What is the difference between the average value and the maximum value of an acoustic variable?
(From the center of the wave to its peak)

A

Amplitude

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34
Q

What are the units of measure for amplitude?

A

Pressure – Pascals
Density – grams/cubic cm
Particle motion – centimetre, inches, units of distance
Amplitude may be expressed in decibels.

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35
Q

Can amplitude be changed by the sonographer?

A

Yes, it is determined by the sound source initially, and can be changed by the sonographer.

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36
Q

What happens to amplitude as a soundwave propagates through the body?

A

Amplitude decreases as sound propagates through the body.

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37
Q

What is the difference between maximum and minimum values of an acoustic variable?

A

The difference between maximum and minimum values of an acoustic variable is called the peak-to-peak amplitude.

38
Q

Another word for half of the peak-to-peak amplitude?

A

Amplitude is half of the peak-to-peak amplitude.

39
Q

What is the rate that work is performed, or the rate of energy transfer?

A

POWER is the rate that work is performed, or the rate of energy transfer.

40
Q

What are the units of measure for power?

A

The units for power are Watts.

41
Q

Can power be changed by the sonographer?

A

Yes, it is initially determined by the sound source and can be changed by the sonographer.

42
Q

What happens to power as sound propagates through the body?

A

Power decreases as sound propagates through the body.

43
Q

What is the relationship between power and amplitude?

A

Power is proportional to the wave’s amplitude squared.
Power is proportional to (amplitude)^2
If amplitude is tripled, then power is increased by a factor of 9.
3*3=9

44
Q

The length or distance of a single cycle within a wave is called its…

A

Wavelength

45
Q

What are the units of measure for wavelength?

A

Metres, millimetres, or any unit of length

46
Q

Can wavelength be changed by the sonographer?

A

No, wavelength cannot be changed by the sonographer.

47
Q

Is wavelength determined by the source or the medium?

A

Wavelength is determined by both the source and the medium.

48
Q

What type of resolution is influenced by wavelength?

A

Axial resolution is influenced by wavelength, therefore wavelength affects image quality.

49
Q

What are the typical values for wavelength in soft tissue?

A

.1–.8 mm is the range of typical values of wavelength in soft tissue.

50
Q

What is the equation for wavelength?

A

Wavelength (mm) = propagation speed(mm/microsec) / frequency(MHz)
Or
L=C/F

51
Q

What is the wavelength of sound with the frequency of 1 MHz in soft tissue?

A

In soft tissue, sound with the frequency of 1 MHz has a wavelength of 1.54 mm.

52
Q

How is wavelength determined in soft tissue?

A

In soft tissue, divide 1.54 mm by frequency in MHz to determine wavelength in millimetres.

53
Q

What is the propagation speed of sound in soft tissue?

A

The propagation speed of sound in soft tissue is 1.54 mm per microsecond.

54
Q

Do higher frequency waves have shorter or longer wavelengths?

A

Higher frequency waves have shorter wavelength and lower frequency waves have longer wavelength.

55
Q

What is propagation speed?

A

Propagation speed is the rate that sound travels through a medium. It is also called velocity or speed.

56
Q

What are the units of measure for propagation speed?

A

Propagation speed is measured in metres per second or millimetres per microsecond.

57
Q

What determines propagation speed?

A

Propagation speed is only determined by the medium, more precisely, by its density and stiffness.

58
Q

How much faster is a 5 MHz sound beam than a 3 MHz sound beam travelling through the same medium?

A

All sound travels at the same speed through any specific medium.

59
Q

Can the propagation speed be changed by the sonographer?

A

No, it cannot be changed by the sonographer since it is only determined by the medium through which it is travelling.

60
Q

What is the average speed of all sound (regardless of frequency) in biologic or soft tissue?

A

In soft tissue all sound travels at 1540 m/s = 1.54 km/s = 1.54 mm/microsecond

61
Q

Arrange from slowest to fastest the propagation speed of sound travelling through the following tissue types:
Soft tissue, lung, fat, bone, tendon, air

A

Air < lung < fat < soft tissue < tendon < bone

62
Q

What is the difference between stiffness and density?

A

Stiffness is related to change in shape, squishability.
Density is related to weight.
Stiffness is more important than density in determining speed.

63
Q

What is the relationship between stiffness and propagation speed?

A

As stiffness increases, propagation speed increases.

64
Q

What is the relationship between density and propagation speed?

A

As density increases, propagation speed decreases.

65
Q

What is the relationship between compressibility, elasticity, and stiffness?

A

Compressibility and elasticity are opposites of stiffness.

66
Q

How does bulk modulus relate to propagation speed?

A

Bulk modulus is the same as stiffness, so when bulk modulus increases, speed increases.

67
Q

What occurs when two waves overlap at the same location and at the same time and combine into a single new wave?

A

Interference

68
Q

What type of interference has occurred with the amplitude of the new combined wave is greater than the original two waves?

A

Constructive interference.

69
Q

What type of waves interfere constructively?

A

In-phase waves interfere constructively.

70
Q

What type of interference has occurred when the amplitude of the new wave is less than one of the original waves?

A

Destructive interference

71
Q

What type of waves interfere destructively?

A

Out-of-phase waves interfere destructively.

72
Q

Which parameter is inversely related to period?

A

Frequency

73
Q

Which parameter is inversely related to frequency?

A

Period

74
Q

Which parameters are determined by the sound source only?

A

Period, frequency, amplitude, power, and intensity are all determined by the sound source only.

75
Q

Which parameter is determined by both the source and the medium?

A

Wavelength is the only parameter determined by both the source and the medium.

76
Q

Which parameter is determined only by the medium?

A

Speed is the only parameter determined solely by the medium.

77
Q

True or false? Sound is a transverse, mechanical wave.

A

False. Sound is mechanical, but it is a longitudinal wave.

78
Q

Which of the following can be changed by the operator?Wavelength, amplitude, intensity, propagation speed, period, power

A

Amplitude, intensity, power

79
Q

The power in a beam is one watt and the area is 5 cm². What is the beam’s intensity?

A

0.2 watts/cm^2

80
Q

If intensity remains the same while the power is doubled, what happens to beam area?

A

The beam area must have doubled.

81
Q

A sound beam travels a total of 10 cm in two seconds. What is the speed of the sound in this medium?

A

5 cm/s

82
Q

True or false? Speed increases as frequency increases.

A

False

83
Q

What happens to the speed of sound in a medium when the bulk modulus increases?

A

It becomes faster because bulk modulus is just another term for stiffness and as stiffness increases, speed increases.

84
Q

The effects of ultrasound upon tissues are…

A

Bioeffects

85
Q

Which of the following waves will have the shortest wavelength?
A. Low frequency travelling in a fast medium
B. Low frequency travelling in a slow medium
C. High-frequency travelling in a fast medium
D. High-frequency travelling in a slow medium

A

D. High frequency travelling in a slow medium

86
Q 
Which of the following characteristics will create the fastest speed of sound?
A. High density, high stiffness
B. Low density, high stiffness
C. High-density, low stiffness
D. Low density, low stiffness
A

B. Low density, high stiffness

87
Q

Which of the following waves is ultrasonic and least useful in diagnostic imaging?
8 MHz, 2.5 MHz, 18,000 Hz, 24,000 Hz, 3,000,000 Hz

A

24,000 Hz

88
Q

Which of the following waves is ultrasonic and most useful in diagnostic imaging?
2,455,000 Hz, 2.4 kHz, 100 MHz, 14,000 Hz

A

2,455,000 Hz

89
Q 
Which of the following waves has the longest wavelength?
A. Low frequency
B. Low amplitude
C. High frequency 
D. High intensity
A

A. Low frequency

90
Q

How is intensity related to power?

A

Intensity is proportional, or directly related, to power. When one goes up, the other goes up.

91
Q

How is intensity related to amplitude?

A

Intensity is proportional to the amplitude of the wave squared.
If the amplitude is doubled, the intensity is increased by a factor of four: 2^2=4
Remember the term:
AMPLITUDE SQUARED

92
Q

True or false? If the amplitude of the wave is increased to 3 times its original value, the intensity is increased by six times.

A

False, intensity is proportional to amplitude squared.

3^2=9 so intensity would increase by nine times.

93
Q

True or false? If the power of a wave is halved, the intensity is reduced to 1/4 its original value.

A

False, power and intensity are proportional to each other, so when one goes up, the other goes up, and when one goes down, the other goes down.

Ultrasound Physics (17 decks)

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