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Vascular 1 > Doppler Review > Flashcards

Doppler Review Flashcards

1
Q

What does Doppler tell the sonographer (6)

A

presence of flow
direction of flow
quality of flow
velocity of RBCs
resistance/pulsatility
timing

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2
Q

what is doppler

A

change in frequency of a sound wave in a moving source

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3
Q

when RBCs are moving toward the transducer the received frequency will be _____ than the transmitted frequency (______/_____ shift)

A

higher
antegrade/positive shift

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4
Q

when RBCs are moving away from the transducer the received frequency will be _____ than the transmitted frequency (______/_____ shift)

A

less
retrograde/negative shift

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5
Q

doppler shift basic calculation

A

Δf = f(received) - f(transmitted)

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6
Q

doppler shift formula (not basic)

A

Δf = (2fo x v x cosO)/C

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7
Q

doppler shift formula but for velocity

A

v= (Δf x C)/(2fo x cosO)

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8
Q

if the operating f or RBC velocity increases = doppler shift ____

A

increases

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9
Q

if the angle of insonation increases = doppler shift _____

A

decreases

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10
Q

doppler shift frequencies calculated by ______ (____)

A

fast Fourier transform (FFT)

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11
Q

autocorrelation is the technique that analyzes _____ in a scan line

A

pulses

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12
Q

autocorrelation determines the ___ and ____ of the blood flow

A

sign
mean velocity

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13
Q

colour doppler uses many pulses to obtain the mean velocity = reduction in ___ = effects the ____ resolution

A

PRF
temporal

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14
Q

Venous flow 4 characteristics

A

spontaneous (sometimes further from the heart isn’t ex. distal fem/pop)
unidirectional (for the most part)
respirophasic
augmentable (not every vein)

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15
Q

what is the most under utilized control in Doppler

A

gain

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16
Q

what does gain overcome

A

the attenuation of small RBCs and scatter

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17
Q

if gain is too low =
too high=

A

poor visualization of spectral trace/colour fill
vs
creates artifacts

18
Q

scale (PRF) AKA

A

velocity range

19
Q

scale too low =
scale too high=

A

aliasing
vs
spectral trace too small, difficult to see low velocity shifts in colour

20
Q

how much space is above/below baseline for venous flow

arterial?

A

1/4 above
3/4 below

arterial = opposite

21
Q

for most studies, the colour baseline will not be adjusted. what is the exception

A

echo

22
Q

do we angle correct for venous flow? why/why not

A

no as velocities are not important (they range so much)

23
Q

what do we do with the box angle in venous studies

A

woo hoo it

24
Q

gate size should be how big compared to vessel

A

1/3 size of the vessel

25
Q

gate size too big =
too small =

A

spectral broadening
vs
difficult to interrogate the true middle of the vessel

26
Q

what does the wall filter do

A

eliminates low-frequency noise

27
Q

what does priority do

A

it can give more emphasis to the colour when overwriting the grayscale

28
Q

priority high =
low=

A

more colour
vs
grayscale shows instead of colour

29
Q

doppler noise/blooming

A

doppler gains too high
colour: blossoms out of the vessel or appears in an anechoic structure that has no flow
spectral: artificially increase PSV

30
Q

doppler flash/clutter

A

appears as low level echoes in the colour flow seen in the tissue as a result of movement like the heart wall, valve, or vessel wall motion

31
Q

aliasing occurs when the _____ is exceeded

A

nyquist limit

32
Q

the Nyquist limit is what

A

1/2 PRF

33
Q

1/2 PRF usually falls between

A

5-30 kHz

34
Q

correcting for aliasing (5)

A

move baseline
increase PRF
increase doppler angle
lower operating frequency
change to continuous wave

35
Q

what to corrections for aliasing can we actually do

A

move baseline
increase PRF

36
Q

doppler mirror image (spectral and colour: caused by and looks like)

A

spectral: flow on both sides of baseline caused by over gain or angle too close to 90
colour: false vessel appears deep to real one due to a deeper strong specular reflector

37
Q

power doppler is where what is measured

A

power or intensity of signal is measured rather than doppler shift

38
Q

power doppler is based on

A

density of RBCs not speed

39
Q

what is power doppler used for

A

assess small vessel, tissue perfusion, and slow flow

40
Q

does power doppler have aliasing

A

no

41
Q

what is less dependent on angle, doppler or power doppler

A

power

Vascular 1 (4 decks)

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