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Physics > Module 3 : Particle Motion and Wave Propagation > Flashcards

Module 3 : Particle Motion and Wave Propagation Flashcards

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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
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2
Q

what is operator control

A
  • you decide what preset and transducer to use based on the requisition and patient history
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3
Q

what is transducer activation (sending)

A
  • electrical current sent to transducer and is converted into sound
  • reverse piezoelectric effect
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4
Q

what is sound interaction

A
  • sound waves travel through the tissue and produce echoes that will return to the transducer
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5
Q

what is transducer activation (receiving)

A
  • returning sound waves are converted back into electrical current
  • piezoelectric effect
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6
Q

what is image display

A
  • electrical current processed through the machine and converted into an image on a monitor
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7
Q

what is the piezoelectric effect

A
  • when pressure waves are applied to a certain crystal they produce electric pulses or a voltage
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8
Q

what is the reverse piezoelectric effect

A
  • when electric pulses or voltage are applied to certain crystals that will produce sound waves
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9
Q

what does acoustic mean

A
  • sound
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10
Q

what does propagation mean

A
  • travel
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11
Q

what does acoustic propagation mean

A
  • effects tissue cause on sound
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12
Q

what does bio effects mean

A
  • effects of ultrasound on tissue
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13
Q

what is sound

A
  • propagating variation
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14
Q

doe waves carry matter

A
  • no only energy
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15
Q

does sound waves require a medium to travel

A
  • yes
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16
Q

what type of wave is a sound wave

A
  • longitudinal mechanical wave
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17
Q

what are the 4 acoustic variables

A
  • pressure
  • density
    + rarefactions and compressions
  • partical motion
  • temperature
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18
Q

characteristics of pressure as an acoustic variable

A
  • pressure can be expressed a a sine wave
  • crests = high pressure
  • troughs = low pressure
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19
Q

what is density

A
  • concentration of particles or mass per unit volume
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20
Q

what are regions of low density called

A
  • rarefactions
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21
Q

what are regions of high density called

A
  • compressions
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22
Q

what is the particle motion in a transverse wave

A
  • perpendicular to travel
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23
Q

what is the particle motion in a longitudinal wave

A
  • parallel to travel
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24
Q

characteristics of temperature as an acoustic variable

A
  • energy creates heat

- important for attenuation and bio effects which we will discuss later

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25
Q

what is mode conversion

A
  • occurs when one type of wave is converted to another form

- occurs at a tissue bone interface

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26
Q

what are 6 wave terms

A
  • frequency
  • period
  • wavelength
  • propagation speed
  • amplitude
  • intensity
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27
Q

what is frequency a measurement of

A
  • cycles per second

- complete variations an acoustic variable goes through in one second

28
Q

what is the unit of frequency

A
  • hertz Hz

- ultrasound uses mega hertz

29
Q

what is period

A
  • time it takes for one cycle to occur

- reciprocal of frequency

30
Q

what is the unit of period

A
  • seconds or micro seconds
31
Q

what is wavelength

A
  • length of space one cycle takes up
32
Q

what is the unit of wavelength

A
  • millimeters
33
Q

what is the relationship between frequency and period

A
  • they are inverse to each other
34
Q

what is the relationship between wavelength and frequency

A
  • inverse to each other
35
Q

what is the formula for determining wavelength

A
  • wavelength = C / F
36
Q

what is propagation speed (c)

A
  • speed with which a wave moves through a medium
37
Q

what is the speed of sound in soft tissue

A

1540 m/s

38
Q

what determines the speed of sound

A
  • the medium
39
Q

what three terms are used to describe wave intensity

A
  • amplitude
  • intensity
  • power
40
Q

what is amplitude

A
  • maximum variation of an acoustic variable
41
Q

what is intensity

A
  • power of wave divided by the area
42
Q

what is power

A
  • total energy over the entire cross sectional area
43
Q

what is another way to describe intensity

A
  • concentration of energy in a sound beam
44
Q

how are amplitude and intensity related

A
  • intensity is directly related to amplitude squared
45
Q

how is intensity related to power and area

A
  • directly related to power

- inversely related to area

46
Q

what is the intensity equation

A

I = P / a

47
Q

is the ultrasound beam intensity uniform in time and space

A
  • no
48
Q

where is the beam most intense in space

A
  • greatest at eh centre and falls off near periphery
49
Q

how does time change the intensity in the beam

A
  • 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
Q

where is the greatest intensity found across the beam

A
  • SP at the centre
51
Q

what is the average intensity

A
  • measured over the entire beam is called the spatial average
52
Q

how is the SP and SA related

A
  • Beam Uniformity Ratio BUR

- BUR = SP/SA

53
Q

what is the temporal peak found

A
  • greatest intensity found in the pulse

- equal to the Pulse average

54
Q

what is the pulse average

A
  • average of all values found in a pulse
55
Q

what is the temporal average

A
  • includes the dead time between pulses where there is no intensity
56
Q

how are the TP and TA related

A
  • duty factor DF

- DF = TA/ TP or DF = TA/PA

57
Q

what is the highest intensity

A
  • SPTP = instantaneous peak
58
Q

what is the lowest intensity

A

SATA

59
Q

what is the intensity we use for bioconsiderations

A

SPTA

60
Q

from lowest to highest intensity where do the ultrasound modes rank

A
  • M Mode
  • real time B mode
  • doppler
  • CW
61
Q

what is the range equation

A
  • used to calculate the distance to a reflector from the probe
62
Q

formula for range equation

A

D = C x t

63
Q

what does D mean in range equation

A

distance to REFLECTOR AND BACK

64
Q

what does C represent in range equation

A

average speed of sound in soft tissue

65
Q

what does t represent in range equation

A

time for round trip

- go return time

Physics (8 decks)

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