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Physics 1 > Doppler Principles > Flashcards

Doppler Principles Flashcards

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1
Q

a change in pitch results from the relative motion of the source of the sound or the receiver

A

doppler effect

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2
Q

what is the Doppler effect

A

a change in pitch results from the relative motion of the source of the sound or the receiver

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3
Q

when the sound source is moving towards the wave, crest are ______ and the pitch is _____, or if moving away from you, the crests are _____ and the pitch sounds ____

A

closer together
higher
further apart
lower

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4
Q

doppler information is orimarily used to assess ____ both _____ and _______

A

blood flow
qualitatively
quantitatively

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5
Q

doppler can give you the following info (3)

A

presence of flow
direction of flow
quality of flow

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6
Q

doppler information is provided by (3)

A

spectral tracing
colour image
audible sound

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7
Q

duplex scanning

A

when scanning both the 2D image and doppler simultaneously (shows image and spectral tracing at same time)

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8
Q

triplex scanning

A

scanning 2D image, doppler, and colour doppler

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9
Q

RBC diameter and what it means

A

7 um
smaller than typical wavelength = Rayleigh scatter

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10
Q

doppler shift is based on the principle of ____ and doppler shift formula

A

wave interference (reflected wave varies slightly in f from transmitted wave = beat frequency)

doppler shift = received f - transmitted f

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11
Q

basic doppler formula

more detailed doppler formula

formula that means most to us as sonographers

A
  1. doppler shift = received f - transmitted f
  2. Δf= (2fo x v x cos0) /c

2fo = operating f
v = velocity of RBC
cos0 = angle to vessel

  1. v = (Δf x c) / (2fo x cos0)
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12
Q

as the operating f increases, the doppler shift ____ (_____ relationship)

A

increases
linear

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13
Q

since RBCs return very little intensity, a ____ f probe is needed for doppler

A

lower

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14
Q

as RBCs move faster, the difference in the returned f _____, therefore _____ the doppler shift (_____ relationship)

A

increases
increasing
linear

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15
Q

cosine 90 = ____ so if the beam is perpendicular to vessels, doppler shift ____ be calculated

A

0
cant

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16
Q

the angle of insonation impacts the ___ calculated (angle up = doppler ____)

A

velocity
down (due to cosine of angle)

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17
Q

as the angle of insonation increases, the percent error for velocity ____

A

increases

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18
Q

Nyquist limit

A

the limit is reached when the RBC velocities are faster than the machine’s ability to sample
(pulses can only be sent out as fast as they can be returned and are limited by the speed of sound in soft tissue)

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19
Q

the Nyquist limit is equal to ____ the PRF

A

1/2

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20
Q

if the PRF is greater than 1/2 (Nyquist limit exceeded) , ____ occurs

A

aliasing

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21
Q

1/2 PRF usually falls between _____ kHz

A

5-30

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22
Q

why does aliasing occur

A

the RBC are not being sampled fast enough so a false reading occurs and parts of the signal are wrapped around the baseline

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23
Q

how can the Nyquist limit help with a diagnosis

A

plaque in lumen increasing velocity = exceeds Nyquist limit = aliasing

24
Q

how to know if it is aliasing rather than reversal

A

if showing both extreme colours and no zero velocities (black) = aliasing, not reversal

25
Q

correcting for aliasing can be accomplished by (5)

A

increase the PRF
move the baseline
increase the Doppler angle (heel or toe of the probe)
lower the operating frequency
change to continuous wave

26
Q

what two ways to correct aliasing are used most often and which one first

A

increase PRF (1st) (AKA scale/ velocity range)
move the baseline (decrease to add room on top)

27
Q

since pulsed sound is used to doppler it ___ possible to define a sample volume or gate

A

is

28
Q

the sample volume is created because of the ____

A

range equation

29
Q

sample volume determined by (3)

A

the beam width (depends on depth/focus)
the receiver gate length
the length of the emitted pulse (short=less data)

30
Q

the ____ the pulse duration the more accurate the beat frequency

A

longer

31
Q

a minimum of __ cycles/pulse is required for doppler (opposite to what)

A

4
opposite to 2D scanning where short PD is best

32
Q

range gating ____ possible with continuous wave doppler

A

not

33
Q

zone of sensitivity

A

area of intersection between the received beam and transmitted beam where CW Doppler sample volume is found

34
Q

how big is the zone of sensitivity and what does this mean

A

5-6cm
large sample volume= chance for picking up more than one vessel = very complex spectral tracing

35
Q

the spectral tracing of doppler frequencies generated by moving blood that we see is plotted along the following axes (3)

A

time (x)
frequency or velocity (y)
power (z) (brightness of the pixels)

36
Q

what is power in spectral tracing proportionate to

A

the number of blood cells moving at one velocity at given time (brighter=more RBCs in a sample)

37
Q

five parts of a spectral analysis (and be able to draw/label it)

A

peak systolic velocity
envelope
window
dicrotic notch
end diastolic velocity

38
Q

the way in which the system creates a spectral trace is through a process called

A

Fast Fourier Transform (FFT)
mathematical technique seperating individual Doppler shifts from the complex beat frequency

39
Q

Fast Fourier Transform (FFT)

A

the process in which the system creates a spectral trace

40
Q

y axis of spectral analysis represented by

A

either the frequency of the Doppler shift or the velocity of the RBCs

41
Q

frequency on a spectral analysis is expressed in and velocity too

A

kHz or Hz

cm/s or m/s

42
Q

antegrade vs retrograde (and what it is expressed by on y-axis)

A

towards to probe (pos number)

away from the probe (neg number)

43
Q

blood can be categorized as ____, _____, or ____

A

high
moderate
low pulsatility

44
Q

how else can the pusitility of blood be referred as

A

resistance (high, mod, low)

45
Q

what is the determining factor to blood pulsitility

A

what it is supplying (brain=low pulsitility/resistance, limbs=high)

46
Q

high pulsatile/resistance blood on spectral analysis has (2) (where its common)

A

tall, narrow systolic peaks
reversed or absent diastolic flow

common in extremities (CFA)

47
Q

low pulsatile/resistance blood on spectral analysis has (2) (where its common)

A

broad systolic peaks (rapid upstroke, comes down slower)
forward flow through diastole (doesn’t reverse/cross baseline)

feeding vital organs (ICA)

48
Q

moderate pulsatile/resistance blood on spectral analysis has (2) (where its common)

A

tall, narrow, sharp systolic peaks (high)
forward through through diastole (low) (sometimes little reversal in late systole)

feed both high/low resistance vascular beds depending on the physiological state (CCA)

49
Q

4 qualitative assessments of a waveform

A

presence of flow
direction of flow
laminar or turbulent
spectral broadening (thick envelope)

50
Q

5 quantitative assessments of a waveform

A

pulsatility index
resistive index
doppler shift
peak velocity
mean velocity

51
Q

pulsatility index is used to _______ and its formula

A

quantify the impedance to flow like in the presence of a stenosis

PI = (A-B)/mean velocity

A=PSV
B= furthest away velocity

52
Q

the systolic/diastolic ratio is another means of quantifying a ____ and its formula

A

change in pulsatility

S/D ratio= A/B

A= PSV
B=EDV

53
Q

when S/D ratio increases, resistance ____

A

increases

54
Q

acceleration formula

A

Acceleration = Δv / ΔT

V=PSV
T= time from start to PSV

55
Q

spectral broadening

A

the vertical thickening of the spectral trace or envelope

all v at same time=thin line
greater range of v=spectral broadening

56
Q

false spectral broadening

A

artifact that occurs when Doppler gain is set too high or sample volume gate is large relative to the vessel

Physics 1 (7 decks)

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