Bioeffects Flashcards
1
Q
When ultrasound propagates through human tissue, what can occur
A
Potential biological effects
2
Q
Very extensive research has been aimed at
A
The evaluation of potential for tissue injury
3
Q
Virtually all ultrasound-introduced adverse bio effects have occurred
A
At higher intensities than diagnostic medical ultrasound
4
Q
Propagation of sound is the effect that
A
Tissue has on sound
5
Q
Tissue propagation is the effect
A
Of sound on tissue
6
Q
Strength of the wave is described by which 3 things
A
Amplitude
Power
Intensity
7
Q
What is the equation for intensity
A
I= P/A
8
Q
Intensity is proportional to
A
Amplitude^2
9
Q
Amplitude, Power, Intensity can also express
A
The loudness or volume of sound
10
Q
What are the 5 acoustic variables
A
Pressure Density Particle motion Temperature Energy
11
Q
Amplitude is defined as
A
The particle displacement, particle velocity or acoustic pressure of a sound wave
12
Q
Amplitude indicates
A
The strength of the detected echo or the voltage induced in a crystal by a pressure wave
13
Q
What is another was to describe amplitude
A
The maximum displacement of an acoustic variable
14
Q
As the pulse travels through the medium, what is the reduction in amplitude called
A
Attenuation
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
16
Q
What is the formula for power
A
P= I x A
17
Q
What is the absolute unit of power
A
Watt
18
Q
What is a watt
A
Joules/ s
19
Q
What is the relative unit of power
A
Decibels (dB)
20
Q
Power is another expression of
A
Strength
21
Q
Power is determined by
A
The pulser
22
Q
Power defaults to
A
100% or zero dB
23
Q
Power is relative to the
A
Exam being preformed
24
Q
What is the SPTA of b scan
A
18.7 mW/cm^2
25
What is the SPPA of B scan
174 mW/cm^2
26
What is the power of B scan
18mW
27
What is the SPTA of M mode
73 mW/cm^2
28
What is the SPPA of M mode
174 mW/cm^2
29
What is the power of M mode
3.9 mW
30
What is the SPTA of pulse Doppler
1140 mW/cm^2
31
What is the SPPA of pulse Doppler
288 mW/cm^2
32
What is the power of pulse Doppler
30.7 mW
33
What is the SPTA of colour Doppler
234r mW/cm^2
34
What is the SPPA of colour Doppler
325 mW/cm^2
35
What is the power of colour Doppler
80.5 mW
36
Intensity is the measure of
The strength of sound wave
37
Intensity is equal to
The power per unit area
38
The absolute unit of intensity is
-mW/cm^2 or W/cm^2
39
What is the relative unit of intensity
Decibel (dB)
40
The relationship between intensity and power is
Proportional
41
If power increases, what happens to intensity
Increases
42
The relationship between area and intensity is
Inversely proportional
43
If area decreases, what happens to intensity
Increases
44
What is the relationship of intensity and the square of the pressure amplitude
Proportional
45
If 2 transducers have the same power but one has a larger beam area at the focal point; which transducer has the greatest intensity
The transducer with a smaller beam area at the focal point
46
A small change in the amplitude will result in what kind of change to intensity
Larger
47
By doubling amplitude what happens to intensity
It is quadrupled
48
Intensity is not a constant in
Time or space
49
What are the different expression of intensity
Spatial average
Spatial peak
Temporal average
Temporal peak
50
In space where is the spatial average found
At the transducer face
51
In space where is the spatial peak found
At the focal point where the beam area is the smallest
52
Spatial average and spatial peak are related by what
Beam uniformity ratio
53
BUR
Beam uniformity ratio
54
What is the equation for calculating BUR
BUR=SP/SA
55
What does the BUR give an idea about
How much focusing there is in a beam
56
Highly focused beams have what kind of BUR
High
57
Weakly focused beams will have what kind of BUR
Low
58
The BUR will always be greater than 1 because why
The peaks are always higher then the averages
59
What would the BUR of a perfectly uniform beam be
One
60
Wha the factors that effect the spatial peak in a US system
An increase in power and focusing will increase the spatial peak
61
What are the factors effecting the spatial average in an US system
Increasing the power will increase the spatial average
62
Over the time a peruse is generated what is there
A temporal average
63
What does the temporal average include
Both the ringing and listening phase of the pulse and the temporal peak
64
What is the temporal peak
The highest amplitude in the pulse at any given time
65
What relates the temporal peak and average
Duty Factor
66
DF
Duty factor
67
What is the equation for DF
DF=TA/TP
68
What replaces temporal peak in the DF equation
Pulse average
69
PA
Pulse average
70
Why is TP replaced by PA
Because the pulse is so short that TP almost equals PA
71
What is PA intensity
The average of all the intensities found within a single pulse
72
What are the factors that effect temporal intensities
Increase in power
| Increase in DF
73
What happens to DF when PRF or PD are increased
It increases
74
What is the DF for CW
100% because the crystal is always ringing
75
Because CW has a DF of 100% what does that mean for CW SPTA value when compared to pulsed wave applications
Typically higher
76
When the intensities are combined what do we need to have a better understanding of
The effects done to the patient
77
From highest to lowest what are the different types of intensities
```
SPTP
SPPA
SPTA
SATP
SAPA
SATA
```
78
What os the SPTP intensity also known as
The instantaneous peak (I.P)
Maximum intensity (I.M)
Time averaged half maximum
79
Where does the information for the effects of US come from
Epidemiology
In vitro cell studies
Animals studies
80
What is an epidemiological study conducted over
A long period of time
81
What is a epidemiologic study
People are monitored over the course of several years that were exposed to US in-utero
82
What is the purpose of a epidemiological study
Look for cause and effect
83
An in vitro study generally exposes what yo US
Macromolecules, membrane transport systems, cells or clumps of cells suspended in liquid
84
What can the results of in vitro studies give valuable information on
To set threshold for in vivo studies
85
What is another term for animal studies
In vivo
86
What do in vivo studies show
That the potential for bioeffects exist
87
What the adverse effects that in vivo studies have shown when the intensity of the machine exceed threshold
```
Fetal weight reductions
Postpartum mortality
Fetal abnormalities
Tissue lesions
Hind limb paralysis
Blood flow stasis
```
88
What are the good effects that in vivo studies have shown for US
Wound repair enhancement
| Tumor regression
89
If the intensities are kept below a certain threshold what has been observed
No adverse effects
90
For unfocused probes what must the intensities be below for it to be considered safe
100mW/cm^2
91
For focused probes what must intensities be under for them to be considered safe
1000mw/cm^2
92
what are the 2 main categories that bioeffects is divided into
Thermal
| Non-thermal (mechanical)
93
Thermal bioeffects are when
The tissues are heated and the effects that heat has on the tissue
94
Non-thermal (mechanical) bioeffects
Is the ability to cause a cell to implode
95
What is important to remember when dealing with thermal effects
That attenuation is primarily due to absorption
96
What is absorption in US
The conversion of sound to heat
97
What tissue handles temperature increases better when compared to what other tissues
Adult, compared to fetal or neonatal
98
There are no adverse effects when the temperature is less than what
2°c
99
Getting to what °c can kill a fetus
4
100
An increase in temperature between 2-6°c will have no adverse effects depending on what
Exposer time
101
When there is higher temperatures what will happen if there is a long exposer time
Higher chance of adverse effects
102
What doe mechanical effects include
Radiation force
| Cavitation
103
What is radiation force
The force exerted by sound on the medium which can deform and disrupt structures
104
What can radiation force cause
Flow in absorbing fluids to deform resulting in shear forces
105
What is cavitation
The production and behaviour of bubbles in a liquid medium
106
What can cavitation be divided into
Stable
| Transient
107
What is stable cavitation
Simple oscillation of the bubbles that can result in the streaming of liquid which results in shear stresses
108
What can shear stress do to tissues
Tear tissues apart
109
What is transient agitation
When the bubble actually collapses producing shock waves
110
What can the shock waves result in
Localized extremely high temperatures and has even emitted light in clear fluids
111
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
1992
112
What was the standard called for bioeffects
Output display standard
113
ODS
Output display standard
114
What are the qualities that are displayed on the ODS
Thermal index
| Mechanical index
115
TI
Thermal index
116
MI
Mechanical Index
117
What is the TI
The ratio of acoustical power produced by the transducer to the power required to raise the temperature in tissue 1°c
118
If the TI value is 1 and there is assumed tissue conditions what could it possible raise
The temperature of the tissue by 1°c
119
What 3 categories is TI furthered divided into
TIS
TIB
TIC
120
What do the 3 different categories for TI account for
The different tissues scanned and their respective absorption rates
121
what is TIS for
Soft tissue
122
What is TIB for
Bone near the focus
123
What is TIC for
Bone near the surface
124
What is the most common TI used
TIS
125
What is TIB used for
Obstetrical scanning
126
What is TIC used for
Transcranial study
127
What does MI represent
The likelihood that the energy used will lead to cavitation
128
What is MI proportional to
The peak rarefractional pressure
129
If peak rarefractional pressures double what happens to MI
It doubles as well
130
What is MI inversely proportional to
The square root of the frequency
131
If frequency quadruples what happens to MI
Halves
132
What is a possibility about TI and MI
Could be underestimated
133
As TI increases what is prudent to consider
Exposer time
134
What is the Max TI allowed
6
135
What is the Max MI allowed
1.9
136
The different applications of US can be divided into what 2 types
Non-scanned
| Scanned
137
What are the non-scanned applications
CW
Pulsed Doppler
M-mode
138
What type poses the highest risk for thermal effects
Non-scanned
139
What non-scanned application has the most potential for thermal effects and why
CW, because it repeatedly transmits in a straight line
140
When MI values are below 0.4 what is the apparent risk
Low
141
What are some adverse effects
Induction of premature ventricular contractions
Microvascular leakage with petechiae
Glomerular capillary hemorrhage
Local cell killing
142
When imaging with contrast agents practitioners should use the minimal what
Agent dose
MI
Examination time consistent with efficacious acquisition of diagnostic information
