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Chapter 4 Flashcards

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1
Q

Can continuous wave ultrasound create anatomic images?

A

No

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2
Q

Short bursts of sound called _ are used in diagnostic ultrasound

A

Pulses

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3
Q

A pulse of ultrasound is a _

A

collection of cycles that travel together

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4
Q

Pulsed ultrasound is made up of _

A

individual cycles that travel together as a unit

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5
Q

Pulsed Ultrasound is made up of two components:

A

Transmit time (talking) Receive time (listening)

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6
Q

Five Parameters for Pulsed Ultrasound

A

Pulse duration
Pulse repetition period Pulse repetition frequency Duty factor
Spatial pulse length

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7
Q

The actual time from the start of a pulse to the end of that pulse

A

Pulse duration

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8
Q

Units for pulse duration

A

units of time, microsecond

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9
Q

Typical value for pulse duration

A

0.3 to 2.0 microseconds

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10
Q

In clinical imaging, a pulse is comprised of _ cycles

A

2-4

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11
Q

Pulse duration is determined by

A

sound source only

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12
Q

Is pulse duration adjustable by the sonographer

A

No

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13
Q

_ is a characteristic of each transducer. Does not change with imaging depth.

A

Pulse duration

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14
Q

Pulse duration (μs) =

A

of cycles x period

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15
Q

Relationship between pulse duration and the number of cycles in the pulse

A

Directly proportional

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16
Q

Relationship between pulse duration and period

A

Directly proportional

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17
Q

Relationship between pulse duration and frequency

A

Inverse

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18
Q

Pulse duration =

A

cycles/frequency

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19
Q

Pulses of long duration have _ cycles in the pulse or _

A

Many

individual cycles with long periods

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20
Q

Pulses of short duration have _ cycles in the pulse or _

A

Few

individual cycles with short periods

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21
Q

Pulses with _ duration are desirable for imaging because _

A

Shorter

they create images of greater quality and accuracy.

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22
Q

The distance that a pulse occupies in space from the start to the end of a pulse.

A

Spatial Pulse Length

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23
Q

Units for spatial pulse length

A

Distance such as mm

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24
Q

Typical values for spatial length

A

in clinical imaging, SPL in

soft tissue ranges from 0.1 to 1 mm

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25
Q

Spatial pulse length is determined by

A

both the sound source and the medium.

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26
Q

SPL =

A

of cycles in pulse x the wavelength of each cycle

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27
Q

Is spatial pulse length adjustable by the sonographer

A

No

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28
Q

Since _ is determined by both the source and the medium, so is SPL

A

Wavelength

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29
Q

Spatial pulse length (mm) =

A

cycles x wavelength (mm)

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30
Q

Relationship between spatial pulse length and the number of cycles in the pulse

A

Directly proportional

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31
Q

Relationship between spatial pulse length and wavelength

A

Directly proportional

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32
Q

Relationship between spatial pulse length and frequency

A

Inverse

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33
Q

Spatial Pulse Length is the _ of the pulse from _

A

distance

end to end
◆millimeters

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34
Q

Pulse duration is the _ that a pulse is “on”

A

Time

Microseconds

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35
Q

Two characteristics create long pulses:

A

Many cycles in the pulse

Cycles with longer wavelengths

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36
Q

Two characteristics create short pulses:

A

Fewer cycles in the pulse

Cycles with shorter wavelengths

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37
Q

Pulses of shorter length are desirable because they create

A

more accurate images and improve resolution

38
Q

The “on” or talking time of a single pulse

A

Pulse duration

39
Q

_ the time from the start of one pulse to the start of the next pulse. It includes one pulse duration plus one listening time.

A

Pulse repetition period

40
Q

Unit for pulse repetition period

A

Time such as milliseconds

41
Q

Typical values of PRP

A

In diagnostic ultrasound, 100

microseconds to 1 millisecond

42
Q

PRP is generally _ than pulse duration

A

100-1,000 times longer

43
Q

PRP is determined by

A

Sound source only

44
Q

Can PRP be adjusted by sonographer

A

Yes, by changing the image depth

45
Q

_ describes the maximum distance into the body that an ultrasound system is imaging

A

Depth of view

46
Q

The markers along the edge of an image indicate

A

Depth

47
Q

Relationship between PRP and depth

A

Directly related

48
Q

When the system is imaging more deeply, the time from one pulse to the next is _. Therefore PRP _

A

Longer

Increases

49
Q

When the system is imaging at shallow depths, the time from one pulse to the next is _. Therefore PRP _

A

Shorter

Decreases

50
Q

_ changes listening time

A

Depth

51
Q

The two components of PRP are

A

Transmit time or “on” time (Pulse duration) and

Receive time or “off” time

52
Q

the number of pulses that an ultrasound system transmits into the body each second.

A

Pulse repetition frequency

53
Q

Units for PRF

A

Hertz

54
Q

Typical values for PRF

A

1,000 to 10,000 Hz (pulses
per second)
We commonly use KHz

55
Q

PRF is determined by

A

Sound source only

56
Q

Can PRF be adjusted by sonographer

A

Yes, by adjusting image depth

57
Q

Is PRF related to frequency

A

No

58
Q

Relationship between PRF and depth

A

Inverse

59
Q

Shallow imaging= _ PRF

A

High

60
Q

Deeper imaging= _ PRF

A

Lower

61
Q

Relationship between PRP and PRF

A

Inverse and reciprocal

62
Q

A longer PRP results in a _ PRF

A

Lower

63
Q

A shorter PRP results in a _ PRF

A

Higher

64
Q

PRF=

A

1/PRP

65
Q

PRP=

A

1/PRF

66
Q

PRF X PRP=

A

1

67
Q

the percentage or fraction of time that the system transmits a pulse.

A

Duty factor

68
Q

Units for duty factor

A

None, it is a percentage

69
Q

Duty factor ranges in clinical imaging

A

from 0.2% to 0.5%

70
Q

Duty factor is determined by

A

Sound source only

71
Q

Is duty factor adjustable by sonographer

A

Yes, by changing depth

72
Q

Relationship between duty factor and depth

A

Inverse

73
Q

Duty factor=

A

(pulse duration/pulse rep period) x 100

74
Q

Longer pulses= _ duty factor

A

High

75
Q

The maximum value for duty factor is _ and is achieved with _

A

100%

Continuous wave sound

76
Q

The minimum value for duty factor is _ and exists when _

A

0%

The transducer is silent

77
Q

Typical value for duty factor

A

0.2%

78
Q

The system listens _ times longer than it transmits

A

500

79
Q

Shallow imaging: _ listening

A

Less

80
Q

Shallow imaging: _ PRP

A

Shorter

81
Q

Shallow imaging: _ PRF

A

Higher

82
Q

Shallow imaging: _ PRF

A

Higher

83
Q

Shallow imaging: _ duty factor

A

Higher

84
Q

Deep imaging: _ listening

A

More

85
Q

Deep imaging: _ PRP

A

Longer

86
Q

Deep imaging: _ PRF

A

Lower

87
Q

Deep imaging: _ duty factor

A

Lower

88
Q

Determined by source

A

Pulse duration
PRP
PRF
Duty factor

89
Q

Determined by source and medium

A

Spatial pulse length

90
Q

Does not change with imaging depth

A

Pulse duration

Spatial pulse length

91
Q

Changes with imaging depth

A

PRP
PRF
Duty factor

92
Q

The parameters that describe a single cycle can describe both continuous and pulsed wave sound

A

Period

Frequency Wavelength Propagation speed

Physics (25 decks)

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