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Physics 1 > Particle Motion and Wave Propagation > Flashcards

Particle Motion and Wave Propagation Flashcards

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1
Q

5 steps of getting an image

A
  1. operator control: decide preset/transdcer
  2. transducer activation (sending): electrical current to sound; reverse piezoelectric effect
  3. sound interaction: sound waves travel through tissue and produce echoes
  4. transducer activation (receiving): sound waves converted to electrical current; piezoelectric effect
  5. image display: electrical current processed through machine and converted to image on monitor
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2
Q

3 reason why preset is important

A
  1. get you in the neighborhood
  2. gives you labels/calculations
  3. safety
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3
Q

acoustic

A

refers to sound

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4
Q

propagation

A

refers to travel

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5
Q

acoustic propagation

A

refers to the effects tissue cause on sound

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6
Q

bioeffects

A

refers to the effects of ultrasound on tissue (can be good or bad)

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7
Q

acoustic variables

A

pressure
density (rarefactions/compressions)
particle motion
temperature

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8
Q

pressure represented by

A

sine wave where crests=increased pressure and troughs=decreased pressure

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9
Q

density

A

concentration of particles or mass per unit volume
low=rarefaction
high=compressions

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10
Q

what kind of wave is a sound wave

A

mechanical wave (needs a medium to travel through)

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11
Q

what kind of wave is an ultrasound machine using

A

longitudinal mechanical wave

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12
Q

longitudinal vs transverse sound waves

A

L: back and forth particle motion parallel to wave travel direction
T: perpendicular to wave travel (swinging rope up and down but waves travel sideways)

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13
Q

mode conversion

A

when one type of wave is converted to another form (ex. long waves until hit bone then trans waves)

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14
Q

wave terms (6)

A

frequency
period
wavelength
propagation speed
amplitude
intensity

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15
Q

frequency (what/equation)

A

number of complete variations an acoustic variable goes through in one second (how many cycles per second)

f=1/T

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16
Q

period (what/equation)

A

time it takes for once cycle to occur

T=1/f

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17
Q

wavelength

A

length of space one cycle takes up

λ=C/f

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18
Q

speed of sound in tissue

A

1540 m/s
1.54 mm/microsecond

19
Q

an increase in frequency affects the period and wavelength how

A

it will result in a decrease in period and wavelength

20
Q

what determines the propagation speed

A

the medium

21
Q

amplitude

A

max variation of an acoustic variable

strength of wave determined by the source of sound

22
Q

intensity (what/equation)

A

power of wave divided by the area

I= P/a

23
Q

power

A

total energy over the entire cross-sectional area

24
Q

how are intensity and amplitude related

A

I = Amp^2

this means a small change in amplitude results in a large change in intensity

25
Q

spatial peak (what/where)

A

greatest intensity found across beam

where focus is

26
Q

spatial average (what/where)

A

average intensity over entire beam

right where probe first makes contact

27
Q

SP and SA related by what and what does the equation look like

A

related by beam uniformity ratio

BUR= SP/SA

28
Q

Temporal peak

A

greatest intensity found in the pulse

29
Q

pulse average

A

average for all values found in a pulse (average of peak on 3 cycles if pulse has 3 cycles)

30
Q

TP and PA relation

A

TP always higher than PA but in ultrasound its so close they are used interchangeably

31
Q

temporal average

A

includes the dead time between pulses where there is no intensity

32
Q

TP and TA related by (equation)

A

related by duty factor

DF=TA/TP

33
Q

highest intensity

A

SPTP

34
Q

biological considerations intensity

A

SPTA

35
Q

lowest intesnity

A

SATA

36
Q

modes of ultrasound from lowest to highest intensity

A

M mode
real time b mode
doppler
continuous wave (no dead time=SPTP)

37
Q

SPTA values are dependent on

A

the depth (changes shape of beam=changes SP)

38
Q

propagation speed in air, fat, bone, soft tissue

A

330m/s
1460m/s
4080m/s
1540m/s

39
Q

range equation

A

D=Cxt

40
Q

what do we do differently in an equation of we want distance to a reflector (interface) vs G-R

A

for reflector we divide by 2
for G-R we dont

41
Q

1cm rule

A

it takes 13 microseconds to travel 1cm to reflector and back to probe (2cm total)

42
Q

If the intensity of the emitted sound is doubled what will happen to the power?

A

it will also double

43
Q

If you scanned with frequencies of 3 MHz, 5 MHZ, and 7.5 MHZ to scan through the same section of liver tissue, which one would reflect back to the surface first?

A

all at the same time as speed of sound is constant

44
Q
A

Physics 1 (8 decks)

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