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Physics > Chapter 3 > Flashcards

Chapter 3 Flashcards

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1
Q

7 parameters that describe the features of a sound wave

A 
Period
Frequency
Amplitude
Power
Intensity 
Wavelength 
Propagation speed
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2
Q

The source of the sound wave is the

A

Ultrasound system and the transducer

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3
Q

_ is the tissue through which the sound is traveling

A

Medium

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4
Q

the time it takes a wave to vibrate a single cycle

A

Period

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5
Q

Typical values: (period) in diagnostic ultrasound

A

Typically 0.06-0.5 microseconds

May be written as 6x10^-8 to 5x10^-7 or .000000006-.00000005

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6
Q

Is period adjustable by the sonographer

A

No

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7
Q

_ frequency goes deeper

A

Low

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8
Q

_ frequency is used for superficial structures

A

High

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9
Q

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

A

Frequency

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10
Q

• In ultrasound, frequency of a wave =

A

Number of cycles per second

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11
Q

Units for frequency

A

Hertz (Hz)

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12
Q

1,000,000 cycles/second = 1_

A

MHz

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13
Q

Typical values of frequency in ultrasound

A

2-15MHz

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14
Q

Frequency affects _ & _

A

Penetration and image quality’s

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15
Q

Frequency is determined by

A

Sound source only

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16
Q

Is frequency adjustable by sonographer

A

No

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17
Q

Infrasound

A

<20 Hz

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18
Q

Audible sound

A

20-20,000Hz

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19
Q

Ultrasound

A

> 20,000Hz (20MHz)

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20
Q

Frequency and period have _ relationship

A

An inverse

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21
Q

Frequency and period: if one remains constant what happens to the other

A

It remains unchanged

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22
Q

Period and frequency are _

A

Reciprocals

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23
Q

If a wave has a frequency of 4Hz, the period would be

A

1/4 second

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24
Q

Seconds & Hz

Microseconds & megahertz are examples of

A

Complimentary units

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25
Q

1Hz=

A

1 event per second

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26
Q

Event can mean

A

Cycle, frames, beat, etc

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27
Q

3 bigness parameters

A

Amplitude
Power
Intensity

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28
Q

Bigness parameters describe

A

Size, magnitude, or strength of a wave

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29
Q

Bigness parameters (amplitude, power, intensity) are determined by what

A

Sound source

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30
Q

The difference between the maximum value and the average or undisturbed/ baseline value of an acoustic variable. The difference between the minimum value and the average value

A

Amplitude

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31
Q

Bigness may be described in

A

Decibels

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32
Q

Units for amplitude

A

Can have units of any of the acoustic variables

Decibels, pascals, g/cm^3, cm, inches, etc

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33
Q

Amplitude: typical values

A 
range from 1 million pascals (1 MPa) to 3
million pascals (3 MPa)
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34
Q

Amplitude is determined by

A

initially by sound source only. As the wave travels through the body, the amplitude decreases. The rate of which depends on the characteristics of the sound wave and the medium

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35
Q

Can amplitude be changed by the sonographer

A

Yes

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36
Q

The difference between the maximum and minimum values of an acoustic variable

A

Peak to peak amplitude

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37
Q

_ is twice the value of amplitude

A

Peak to peak amplitude

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38
Q

The rate at which work is performed; the rate of energy transfer

A

Power

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39
Q

Units for power

A

Watss

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40
Q

Power: typical values

A

.004-.090 watts (4-90 milliwatts)

41
Q

Power is determined by

A

initially by the sound source. Power decreases as sound propagates through the body (rate of decrease is dependent upon the medium)

42
Q

Can power be changed by the sonographer

A

Yes

43
Q

_ & _ describe the magnitude of a wave

A

Amplitude and power

44
Q

When power increases what happens to amplitude

A

It increases too

45
Q

Power is proportional to the waves

A

Amplitude squared

46
Q

If amplitude is tripled, the power is

A

increased by a factor of nine

47
Q

If the amplitude is halved, the power is

A

decreased by a factor of four

48
Q

The concentration of energy in a sound beam • Intensity = power/area

A

Intensity

49
Q

Intensity describes

A

The bigness of a wave

50
Q

Units for intensity

A

W/cm^2

51
Q

Intensity: typical values

A

.01-300 W/cm^2

52
Q

Intensity is determined by

A

Initially by the sound source.

Changes as it propagates through the body

53
Q

Can intensity be changed by the sonographer

A

Yes

54
Q

Relationship between intensity & power

A

Proportional

55
Q

If a wave’s power is doubled, the intensity is

A

Doubled

56
Q

Relationship between intensity & amplitude

A

Proportional to amplitude squared

57
Q

If a wave’s amplitude is doubled, the intensity

A

increases four times its original value

58
Q

The distance or length of one complete cycle

A

Wavelength

59
Q

Units for wavelength

A

mm, m, units of length

60
Q

Typical values of wavelength in soft tissue

A

0.1-0.8mm

61
Q

Can wave length be changed by the sonographer

A

No

62
Q

Equation for wavelength

A

L=c/f (L=1.54/f)
L (wavelength:mm)
c (propagation speed:mm/microseconds)
f (frequency: MHz)

63
Q

Relationship between wavelength and frequency

A

Inverse

64
Q

As frequency increases, wavelength _

A

decreases

65
Q

Lower frequency= _ wavelength

A

longer

66
Q

Wavelength of 1 MHz sound in soft tissue=

A

1.54mm

67
Q

The rate at which a sound wave travels through a medium

A

Propagation speed

68
Q

Units of speed

A

m/s, mm/microseconds

69
Q

Typical value of speed

A

500 m/s-4,000 m/s depending in the tissue through which it is traveling

70
Q

Speed is determined by

A

Medium

71
Q

Can speed be changed by the sonographer

A

Not

72
Q

TThe average biologic medium is called

A

Soft tissue

73
Q

The speed of sound in soft tissue is

A

1,540 m/s or 1.54 mm/microseconds

74
Q

Speed in tissue types from lowest to highest

A 
Lung
Fat
Soft tissue
Liver
Blood
Muscle
Tendon
Bone
75
Q

Sound travels slowest in what tissue

A

Lung

76
Q

Sounds travels fastest in what tissue

A

Bone

77
Q

Prop speed in air

A

330 m/s

78
Q

Prop speed in water

A

1,480 m/s

79
Q

Prop speed in metals

A

2,000-7,000 m/s

80
Q

Sounds travels fastest in

A

solids

81
Q

Sound travels slowest in

A

gases

82
Q

Equation for speed

A

c=fXL
c: speed
f: frequency
L: wavelength

83
Q

Two characteristics of a medium that affect the speed of sound

A

Stiffness

Density

84
Q

The ability of an object to resist compression, opposite of compressibility and elasticity

A

Stiffness

85
Q

Stiffness is AKA

A

Bulk modulus

86
Q

The relative weight of a material

A

Density

87
Q

Stiffness and speed are _ related

A

Directly

88
Q

The stiffer the medium, the _ the sound

A

Faster

89
Q

Density and speed are _ related

A

Inversely

90
Q

The denser the material, the _ the sound

A

Slower

91
Q

Rule of thumbs

A

Stiffness & Speed= Same direction

Density & Speed= Different direction

92
Q

Stiffness has _ influence on speed than density

A

greater

93
Q

Fastest media are

A

Stiff and not dense

94
Q

Determined by source

A 
Amplitude
Power
Period
Frequency
Intensity
95
Q

Determined by medium

A

Speed

96
Q

Determined by source and medium

A

Wavelength

97
Q

Can be changed by sonographer

A

Amplitude
Power
Intensity

98
Q

Can’t be changed by sonographer

A

Wavelength
Period
Speed
Frequency

99
Q

Reciprocals

A

Period

Frequency

Physics (25 decks)

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