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Bioeffects Flashcards

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1
Q

When ultrasound propagates through human tissue, what can occur

A

Potential biological effects

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2
Q

Very extensive research has been aimed at

A

The evaluation of potential for tissue injury

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3
Q

Virtually all ultrasound-introduced adverse bio effects have occurred

A

At higher intensities than diagnostic medical ultrasound

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4
Q

Propagation of sound is the effect that

A

Tissue has on sound

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5
Q

Tissue propagation is the effect

A

Of sound on tissue

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6
Q

Strength of the wave is described by which 3 things

A

Amplitude
Power
Intensity

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7
Q

What is the equation for intensity

A

I= P/A

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8
Q

Intensity is proportional to

A

Amplitude^2

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9
Q

Amplitude, Power, Intensity can also express

A

The loudness or volume of sound

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10
Q

What are the 5 acoustic variables

A 
Pressure
Density 
Particle motion
Temperature 
Energy
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11
Q

Amplitude is defined as

A

The particle displacement, particle velocity or acoustic pressure of a sound wave

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12
Q

Amplitude indicates

A

The strength of the detected echo or the voltage induced in a crystal by a pressure wave

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13
Q

What is another was to describe amplitude

A

The maximum displacement of an acoustic variable

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14
Q

As the pulse travels through the medium, what is the reduction in amplitude called

A

Attenuation

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15
Q

Power is the measure of what

A

The total energy transmitted, summed over the cross sectional area of the beam per unit time

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16
Q

What is the formula for power

A

P= I x A

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17
Q

What is the absolute unit of power

A

Watt

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18
Q

What is a watt

A

Joules/ s

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19
Q

What is the relative unit of power

A

Decibels (dB)

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20
Q

Power is another expression of

A

Strength

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21
Q

Power is determined by

A

The pulser

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22
Q

Power defaults to

A

100% or zero dB

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23
Q

Power is relative to the

A

Exam being preformed

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24
Q

What is the SPTA of b scan

A

18.7 mW/cm^2

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25
Q

What is the SPPA of B scan

A

174 mW/cm^2

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26
Q

What is the power of B scan

A

18mW

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27
Q

What is the SPTA of M mode

A

73 mW/cm^2

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28
Q

What is the SPPA of M mode

A

174 mW/cm^2

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29
Q

What is the power of M mode

A

3.9 mW

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30
Q

What is the SPTA of pulse Doppler

A

1140 mW/cm^2

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31
Q

What is the SPPA of pulse Doppler

A

288 mW/cm^2

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32
Q

What is the power of pulse Doppler

A

30.7 mW

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33
Q

What is the SPTA of colour Doppler

A

234r mW/cm^2

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34
Q

What is the SPPA of colour Doppler

A

325 mW/cm^2

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35
Q

What is the power of colour Doppler

A

80.5 mW

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36
Q

Intensity is the measure of

A

The strength of sound wave

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37
Q

Intensity is equal to

A

The power per unit area

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38
Q

The absolute unit of intensity is

A

-mW/cm^2 or W/cm^2

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39
Q

What is the relative unit of intensity

A

Decibel (dB)

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40
Q

The relationship between intensity and power is

A

Proportional

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41
Q

If power increases, what happens to intensity

A

Increases

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42
Q

The relationship between area and intensity is

A

Inversely proportional

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43
Q

If area decreases, what happens to intensity

A

Increases

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44
Q

What is the relationship of intensity and the square of the pressure amplitude

A

Proportional

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45
Q

If 2 transducers have the same power but one has a larger beam area at the focal point; which transducer has the greatest intensity

A

The transducer with a smaller beam area at the focal point

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46
Q

A small change in the amplitude will result in what kind of change to intensity

A

Larger

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47
Q

By doubling amplitude what happens to intensity

A

It is quadrupled

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48
Q

Intensity is not a constant in

A

Time or space

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49
Q

What are the different expression of intensity

A

Spatial average
Spatial peak
Temporal average
Temporal peak

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50
Q

In space where is the spatial average found

A

At the transducer face

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51
Q

In space where is the spatial peak found

A

At the focal point where the beam area is the smallest

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52
Q

Spatial average and spatial peak are related by what

A

Beam uniformity ratio

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53
Q

BUR

A

Beam uniformity ratio

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54
Q

What is the equation for calculating BUR

A

BUR=SP/SA

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55
Q

What does the BUR give an idea about

A

How much focusing there is in a beam

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56
Q

Highly focused beams have what kind of BUR

A

High

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57
Q

Weakly focused beams will have what kind of BUR

A

Low

58
Q

The BUR will always be greater than 1 because why

A

The peaks are always higher then the averages

59
Q

What would the BUR of a perfectly uniform beam be

A

One

60
Q

Wha the factors that effect the spatial peak in a US system

A

An increase in power and focusing will increase the spatial peak

61
Q

What are the factors effecting the spatial average in an US system

A

Increasing the power will increase the spatial average

62
Q

Over the time a peruse is generated what is there

A

A temporal average

63
Q

What does the temporal average include

A

Both the ringing and listening phase of the pulse and the temporal peak

64
Q

What is the temporal peak

A

The highest amplitude in the pulse at any given time

65
Q

What relates the temporal peak and average

A

Duty Factor

66
Q

DF

A

Duty factor

67
Q

What is the equation for DF

A

DF=TA/TP

68
Q

What replaces temporal peak in the DF equation

A

Pulse average

69
Q

PA

A

Pulse average

70
Q

Why is TP replaced by PA

A

Because the pulse is so short that TP almost equals PA

71
Q

What is PA intensity

A

The average of all the intensities found within a single pulse

72
Q

What are the factors that effect temporal intensities

A

Increase in power

Increase in DF

73
Q

What happens to DF when PRF or PD are increased

A

It increases

74
Q

What is the DF for CW

A

100% because the crystal is always ringing

75
Q

Because CW has a DF of 100% what does that mean for CW SPTA value when compared to pulsed wave applications

A

Typically higher

76
Q

When the intensities are combined what do we need to have a better understanding of

A

The effects done to the patient

77
Q

From highest to lowest what are the different types of intensities

A 
SPTP
SPPA
SPTA
SATP
SAPA
SATA
78
Q

What os the SPTP intensity also known as

A

The instantaneous peak (I.P)
Maximum intensity (I.M)
Time averaged half maximum

79
Q

Where does the information for the effects of US come from

A

Epidemiology
In vitro cell studies
Animals studies

80
Q

What is an epidemiological study conducted over

A

A long period of time

81
Q

What is a epidemiologic study

A

People are monitored over the course of several years that were exposed to US in-utero

82
Q

What is the purpose of a epidemiological study

A

Look for cause and effect

83
Q

An in vitro study generally exposes what yo US

A

Macromolecules, membrane transport systems, cells or clumps of cells suspended in liquid

84
Q

What can the results of in vitro studies give valuable information on

A

To set threshold for in vivo studies

85
Q

What is another term for animal studies

A

In vivo

86
Q

What do in vivo studies show

A

That the potential for bioeffects exist

87
Q

What the adverse effects that in vivo studies have shown when the intensity of the machine exceed threshold

A 
Fetal weight reductions
Postpartum mortality 
Fetal abnormalities 
Tissue lesions 
Hind limb paralysis 
Blood flow stasis
88
Q

What are the good effects that in vivo studies have shown for US

A

Wound repair enhancement

Tumor regression

89
Q

If the intensities are kept below a certain threshold what has been observed

A

No adverse effects

90
Q

For unfocused probes what must the intensities be below for it to be considered safe

A

100mW/cm^2

91
Q

For focused probes what must intensities be under for them to be considered safe

A

1000mw/cm^2

92
Q

what are the 2 main categories that bioeffects is divided into

A

Thermal

Non-thermal (mechanical)

93
Q

Thermal bioeffects are when

A

The tissues are heated and the effects that heat has on the tissue

94
Q

Non-thermal (mechanical) bioeffects

A

Is the ability to cause a cell to implode

95
Q

What is important to remember when dealing with thermal effects

A

That attenuation is primarily due to absorption

96
Q

What is absorption in US

A

The conversion of sound to heat

97
Q

What tissue handles temperature increases better when compared to what other tissues

A

Adult, compared to fetal or neonatal

98
Q

There are no adverse effects when the temperature is less than what

A

2°c

99
Q

Getting to what °c can kill a fetus

A

4

100
Q

An increase in temperature between 2-6°c will have no adverse effects depending on what

A

Exposer time

101
Q

When there is higher temperatures what will happen if there is a long exposer time

A

Higher chance of adverse effects

102
Q

What doe mechanical effects include

A

Radiation force

Cavitation

103
Q

What is radiation force

A

The force exerted by sound on the medium which can deform and disrupt structures

104
Q

What can radiation force cause

A

Flow in absorbing fluids to deform resulting in shear forces

105
Q

What is cavitation

A

The production and behaviour of bubbles in a liquid medium

106
Q

What can cavitation be divided into

A

Stable

Transient

107
Q

What is stable cavitation

A

Simple oscillation of the bubbles that can result in the streaming of liquid which results in shear stresses

108
Q

What can shear stress do to tissues

A

Tear tissues apart

109
Q

What is transient agitation

A

When the bubble actually collapses producing shock waves

110
Q

What can the shock waves result in

A

Localized extremely high temperatures and has even emitted light in clear fluids

111
Q

What year was a standard set so that real time information related to the potential for bioeffects be displayed on the monitor of US scanners

A

1992

112
Q

What was the standard called for bioeffects

A

Output display standard

113
Q

ODS

A

Output display standard

114
Q

What are the qualities that are displayed on the ODS

A

Thermal index

Mechanical index

115
Q

TI

A

Thermal index

116
Q

MI

A

Mechanical Index

117
Q

What is the TI

A

The ratio of acoustical power produced by the transducer to the power required to raise the temperature in tissue 1°c

118
Q

If the TI value is 1 and there is assumed tissue conditions what could it possible raise

A

The temperature of the tissue by 1°c

119
Q

What 3 categories is TI furthered divided into

A

TIS
TIB
TIC

120
Q

What do the 3 different categories for TI account for

A

The different tissues scanned and their respective absorption rates

121
Q

what is TIS for

A

Soft tissue

122
Q

What is TIB for

A

Bone near the focus

123
Q

What is TIC for

A

Bone near the surface

124
Q

What is the most common TI used

A

TIS

125
Q

What is TIB used for

A

Obstetrical scanning

126
Q

What is TIC used for

A

Transcranial study

127
Q

What does MI represent

A

The likelihood that the energy used will lead to cavitation

128
Q

What is MI proportional to

A

The peak rarefractional pressure

129
Q

If peak rarefractional pressures double what happens to MI

A

It doubles as well

130
Q

What is MI inversely proportional to

A

The square root of the frequency

131
Q

If frequency quadruples what happens to MI

A

Halves

132
Q

What is a possibility about TI and MI

A

Could be underestimated

133
Q

As TI increases what is prudent to consider

A

Exposer time

134
Q

What is the Max TI allowed

A

6

135
Q

What is the Max MI allowed

A

1.9

136
Q

The different applications of US can be divided into what 2 types

A

Non-scanned

Scanned

137
Q

What are the non-scanned applications

A

CW
Pulsed Doppler
M-mode

138
Q

What type poses the highest risk for thermal effects

A

Non-scanned

139
Q

What non-scanned application has the most potential for thermal effects and why

A

CW, because it repeatedly transmits in a straight line

140
Q

When MI values are below 0.4 what is the apparent risk

A

Low

141
Q

What are some adverse effects

A

Induction of premature ventricular contractions
Microvascular leakage with petechiae
Glomerular capillary hemorrhage
Local cell killing

142
Q

When imaging with contrast agents practitioners should use the minimal what

A

Agent dose
MI
Examination time consistent with efficacious acquisition of diagnostic information

Physics 3 (5 decks)

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