Module 3 : Particle Motion and Wave Propagation Flashcards
1
Q
what are the 5 steps to create an image
A
- step 1 = operator control
- step 2 = transducer activation (sending)
- step 3 = sound interaction
- step 4 = transducer activation (recieving)
- step 5 = image display
2
Q
what is operator control
A
- you decide what preset and transducer to use based on the requisition and patient history
3
Q
what is transducer activation (sending)
A
- electrical current sent to transducer and is converted into sound
- reverse piezoelectric effect
4
Q
what is sound interaction
A
- sound waves travel through the tissue and produce echoes that will return to the transducer
5
Q
what is transducer activation (receiving)
A
- returning sound waves are converted back into electrical current
- piezoelectric effect
6
Q
what is image display
A
- electrical current processed through the machine and converted into an image on a monitor
7
Q
what is the piezoelectric effect
A
- when pressure waves are applied to a certain crystal they produce electric pulses or a voltage
8
Q
what is the reverse piezoelectric effect
A
- when electric pulses or voltage are applied to certain crystals that will produce sound waves
9
Q
what does acoustic mean
A
- sound
10
Q
what does propagation mean
A
- travel
11
Q
what does acoustic propagation mean
A
- effects tissue cause on sound
12
Q
what does bio effects mean
A
- effects of ultrasound on tissue
13
Q
what is sound
A
- propagating variation
14
Q
doe waves carry matter
A
- no only energy
15
Q
does sound waves require a medium to travel
A
- yes
16
Q
what type of wave is a sound wave
A
- longitudinal mechanical wave
17
Q
what are the 4 acoustic variables
A
- pressure
- density
+ rarefactions and compressions - partical motion
- temperature
18
Q
characteristics of pressure as an acoustic variable
A
- pressure can be expressed a a sine wave
- crests = high pressure
- troughs = low pressure
19
Q
what is density
A
- concentration of particles or mass per unit volume
20
Q
what are regions of low density called
A
- rarefactions
21
Q
what are regions of high density called
A
- compressions
22
Q
what is the particle motion in a transverse wave
A
- perpendicular to travel
23
Q
what is the particle motion in a longitudinal wave
A
- parallel to travel
24
Q
characteristics of temperature as an acoustic variable
A
- energy creates heat
- important for attenuation and bio effects which we will discuss later
25
what is mode conversion
- occurs when one type of wave is converted to another form
| - occurs at a tissue bone interface
26
what are 6 wave terms
- frequency
- period
- wavelength
- propagation speed
- amplitude
- intensity
27
what is frequency a measurement of
- cycles per second
| - complete variations an acoustic variable goes through in one second
28
what is the unit of frequency
- hertz Hz
| - ultrasound uses mega hertz
29
what is period
- time it takes for one cycle to occur
| - reciprocal of frequency
30
what is the unit of period
- seconds or micro seconds
31
what is wavelength
- length of space one cycle takes up
32
what is the unit of wavelength
- millimeters
33
what is the relationship between frequency and period
- they are inverse to each other
34
what is the relationship between wavelength and frequency
- inverse to each other
35
what is the formula for determining wavelength
- wavelength = C / F
36
what is propagation speed (c)
- speed with which a wave moves through a medium
37
what is the speed of sound in soft tissue
1540 m/s
38
what determines the speed of sound
- the medium
39
what three terms are used to describe wave intensity
- amplitude
- intensity
- power
40
what is amplitude
- maximum variation of an acoustic variable
41
what is intensity
- power of wave divided by the area
42
what is power
- total energy over the entire cross sectional area
43
what is another way to describe intensity
- concentration of energy in a sound beam
44
how are amplitude and intensity related
- intensity is directly related to amplitude squared
45
how is intensity related to power and area
- directly related to power
| - inversely related to area
46
what is the intensity equation
I = P / a
47
is the ultrasound beam intensity uniform in time and space
- no
48
where is the beam most intense in space
- greatest at eh centre and falls off near periphery
49
how does time change the intensity in the beam
- sound is sent in pulses which means there is no intensity during listening
- within a pulse intensity starts off high at beginning then falls off
50
where is the greatest intensity found across the beam
- SP at the centre
51
what is the average intensity
- measured over the entire beam is called the spatial average
52
how is the SP and SA related
- Beam Uniformity Ratio BUR
| - BUR = SP/SA
53
what is the temporal peak found
- greatest intensity found in the pulse
| - equal to the Pulse average
54
what is the pulse average
- average of all values found in a pulse
55
what is the temporal average
- includes the dead time between pulses where there is no intensity
56
how are the TP and TA related
- duty factor DF
| - DF = TA/ TP or DF = TA/PA
57
what is the highest intensity
- SPTP = instantaneous peak
58
what is the lowest intensity
SATA
59
what is the intensity we use for bioconsiderations
SPTA
60
from lowest to highest intensity where do the ultrasound modes rank
- M Mode
- real time B mode
- doppler
- CW
61
what is the range equation
- used to calculate the distance to a reflector from the probe
62
formula for range equation
D = C x t
63
what does D mean in range equation
distance to REFLECTOR AND BACK
64
what does C represent in range equation
average speed of sound in soft tissue
65
what does t represent in range equation
time for round trip
| - go return time
