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DMS 170 Physics > Test 2- Pulsed And Intensity > Flashcards

Test 2- Pulsed And Intensity Flashcards

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0
Q

Cycle is on….

A

Transmit

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1
Q

What is pulsed Ultrasound?

A

Collection of cycles that travel together.

Must have a beginning and an end.

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2
Q

Cycle is off…

A

Receive

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3
Q

What are Pulsed Wave Parameters?

A
  • pulse duration
  • spatial pulse length
  • pulse repetition period
  • pulse repetition frequency
  • duty factor
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4
Q

What is Pulse Duration?

A
  • on time - talking time - transmit time
  • actual time from the start to the end of a pulse
  • amount of time the pulse lasts
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5
Q

What are the units of pulse duration?

A

seconds, microseconds

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6
Q

Pulse Duration is the what?

A

Time it takes for one pulse to occur.

-determined by the number of cycles in each pulse and the period of the cycle

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7
Q

Can pulse duration be changed by the sonographer?

A

No.

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8
Q

Pulse duration is a characteristic of what?

A

the transducer/sound source

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9
Q

What is the pulse duration for clinical imaging?

A

0.5-2 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

What is the formula for pulse duration?

A 
PD = # of cycles in pulse x period
PD = # of cycles in pulse / frequency
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12
Q

Pulsed Duration - the transducer is made of _________ or _________ that stop the ringing and shorten the pulse for improved axial resolution.

A

backing layers, damping layers

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13
Q

short pulse = what?

A

better axial resolution

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14
Q

PD is directly related to ________ and number of _______ in the pulse.

A

Duty Factor, cycles

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15
Q

PD is inversely related to _______.

A

PRF

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16
Q

What is Spatial Pulse Length?

A

length or distance that a pulse occupies in space.

distance from the start of a pulse to the end of that pulse.

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17
Q

What are the units for Spatial Pulse Length?

A

mm

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18
Q

What is the spatial pulse length for clinical imaging?

A

0.1 to 1 mm

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19
Q

Spatial pulse length is determined by what?

A

the sound source and the medium

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20
Q

Can the Spatial Pulse Length be changed by the sonographer?

A

No.

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21
Q

What is the formula for Spatial Pulse Length?

A

SPL = # of cycles x wavelength

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22
Q

Why are shorter pulses desirable?

A

Better AXIAL RESOLUTION

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23
Q

SPL is directly related to _______ and ________.

A

wavelength, number of cycles

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24
Q

SPL is inversely related to ________.

A

frequency

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25
Q

What is Pulse Repetition Period?

A

Time from the start of one pulse to the start of the next pulse.
Includes talking and listening times.
Time when system has a pulse and when it has no pulse.

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26
Q

What are the units for PRP?

A

time

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27
Q

What is the PRP for clinical imaging?

A

100 microseconds to 1 msec

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28
Q

PRP is determined by what?

A

sound source

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29
Q

Can the PRP be changed by the sonographer?

A

Yes. PRP changes by the sonographer when depth of view is changed and then listening time increases.

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30
Q

PRP is directly related to what?

A

imaging depth

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31
Q

PRP is inversely related to what?

A

PRF

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32
Q

As imaging depth increases _________ increases.

A

PRP

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33
Q

As imaging depth decreases ________ decreases.

A

PRP

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34
Q

What is Pulse Repetition Frequency?

A

Number of pulses in one second.

Not related to the “frequency”

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35
Q

What is pulse repetition frequency determined by?

A

depth of view

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36
Q

What is the formula for PRF max?

A

PRF max = speed of sound in the medium / 2 x (max depth)

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37
Q

What are the units for PRF?

A

Hertz

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38
Q

What is the PRF in clinical imaging?

A

1,000-10,000 Hz (pulses per second)

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39
Q

What is PRF determined by?

A

sound source

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40
Q

PRF depends on what?

A

imaging depth

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41
Q

Can PRF be changed by the sonographer?

A

Yes. It changes by the sonographer when depth of view is changed

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42
Q

Shallow image = ______ PRF.

A

higher

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43
Q

Deeper image = ______ PRF.

A

lower

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44
Q

PRF is directly related to __________.

A

duty factor

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45
Q

PRF is inversely related to ________ and ________.

A

imaging depth and PRP

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46
Q

PRF determines what?

A

how fast images are generated

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47
Q

PRF of 5kHz means ________.

A

5000 pulses per second

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48
Q

What is Duty Factor?

A

Percentage of time that the system is “talking.”

Percentage of time that the system is ON

49
Q

Duty factor of 100% = ?

A

continuous wave

50
Q

DF of 1% or less = ?

A

pulsed wave

51
Q

DF of 0% = ?

A

equipment is OFF

52
Q

What is duty factor determined by?

A

sound source

53
Q

Can duty factor be changed by the sonographer?

A

Yes. It is changed by the sonographer when the depth of view is changed.

54
Q

The duty factor of clinical imaging is what?

A

0.1% to 1.0%

55
Q

Duty factor for Doppler is what?

A

0.5% to 5.0%

56
Q

What is the formula for duty factor?

A 
DF = Pulse Duration / Pulse repetition period x 100
DF = talking time / talking and listening time
57
Q

Duty factor increases when….

A
  • imaging depth decreases
  • shallower imaging
  • PRP decreases
  • PRF increases
58
Q

Duty factor is directly related to ______ and ______.

A

PRF and PD

59
Q

Duty factor is inversely related to ______.

A

PRP

60
Q

For shallow imaging in pulsed ultrasound there is……

A
  • less listening
  • shorter PRP
  • higher PRF
  • higher duty factor
61
Q

For deeper imaging in pulsed ultrasound there is…..

A
  • more listening
  • longer PRP
  • lower PRF
  • lower duty factor
62
Q

Duty Factor is important for determining _______. Why?

A

intensity, it relates to bioeffects

63
Q

What is bandwidth?

A

range of frequencies

64
Q

Shorter pulse has ________ bandwidth.

A

broad

65
Q

Longer pulse has _______ bandwidth.

A

narrow

66
Q

What parameters are changed by imaging depth?

A

PRP, PRF, Duty Factor

67
Q

What is intensity?

A

the amount or degree of strength of sound per unit area

68
Q

What is the unit of intensity?

A

W / cm^2

69
Q

Intensity relates to what?

A

the strength of the sound beam

70
Q

Intensity ~ ?

Intensity ~ ?

A

intensity ~ power

intensity ~ amplitude ^2

71
Q

What is intensity determined by?

A

determined by the system

72
Q

Why is intensity important?

A

related to bioeffects

73
Q

Can intensity be changed by the sonographer?

A

Yes.

74
Q

Intensity is the concentration of what?

A

the power in a beam

75
Q

What is the formula for intensity?

A

power (watts) / beam area (cm^2)

76
Q

Increasing _______, increasing intensity

A

power

77
Q

increasing _______, decreases intensity.

A

area

78
Q

decreasing _______, increases intensity.

A

area

79
Q

What is energy?

A

the ability to do work

80
Q

______ is energy transferred divided by time.

A

Power

81
Q

Intensity varies across what?

A

the sound beam

82
Q

Intensity is highest in the _______ and falls off at the ________.

A

center, periphery

83
Q

intensity is not uniform across the ______ and with ______ ______ not uniform in time.

A

beam, pulsed wave

84
Q

With pulsed wave, the intensity varies in _____.

A

time

85
Q

With pulsed wave, the intensity varies in _______…..

A

space

86
Q

Intensity
Peak-
Average-

A

Peak- the maximum value

Average - the middle value

87
Q

Intensity

Spatial (where) Peak -

A

maximum intensity along the beam

determined by focusing

88
Q

Intensity

Spatial (where) average-

A

Spatial (where) average- average over the beam

89
Q

Spatial (where) -

A

referring to space

90
Q

Which is higher SP or SA?

A

SP is always higher

91
Q

For ultrasound the ________ ________ is at the center of the beam and it _______ as the beam spreads…..

A

strongest intensity, reduces

92
Q

Temporal (when) -

A

referring to all time (transmit and receive)

93
Q

temporal (when) peak-

A

maximum intensity in the pulse

94
Q

temporal (when) average -

A

intensity over the time of the PRP

95
Q

Pulse average -

A

the intensity averaged over the time of the pulse

96
Q

For a given pulse, highest to lowest would be…..

A

TP, PA, TA

97
Q

Why are the TA and PA equal for continuous wave?

A

because there is no pulse

98
Q

Spatial peak, temporal peak SPTP

A

maximum value in space and time

99
Q

SATP

A

Spatial average, temporal peak

100
Q

SPPA

A

Spatial peak, pulse average

101
Q

SAPA

A

Spatial average, pulse average

102
Q

SPTA

A

Spatial peak, temporal average

103
Q

What is the most relevant intensity with respect to tissue heating?

A

SPTA

104
Q

SATA

A

Spatial average, temporal average

105
Q

the beam is only transmitting _______% in PW.

A

less than 1%

106
Q

99% of the time the intensity is _____.

A

0

107
Q

Spatial intensity -

A

ultrasound beam does not have the same intensity at different locations

108
Q

temporal intensity -

A

ultrasound beam does not have the same intensity at different times

109
Q

List the intensities from high to low.

A

SPTP > SATP > SPPA > SAPA > SPTA > SATA

110
Q

Beam uniformity factor or coefficient or ratio (BUR) SP/SA -

A

describes sound beam in space

111
Q

BUR

A

ratio of center intensity to average
unitless
always greater than 1

112
Q

For continuous wave - SPTA and SPPA and SPTP are _____.

A

the same

113
Q

For continuous wave SATA and SAPA and SATP are ______.

A

the same

114
Q

What is intensity determined by?

A

sound source

115
Q

Can intensity be changed by the sonographer?

A

Yes. Sonographer changes when changing power

116
Q

hydrophone or microprobe

A

device used to measure output intensity of the transducer

117
Q

below 100 mW/cm^2 -

A

unfocused sound

118
Q

below 1000 mW/cm^2 -

A

focused sound

119
Q

higher intensities are needed to produce bioeffects with a ________ transducer.

A

focused

DMS 170 Physics (1 decks)

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