Doppler Review

Question 1

What does Doppler tell the sonographer (6)

Answer 1

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

Question 2

what is doppler

Answer 2

change in frequency of a sound wave in a moving source

Question 3

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

Answer 3

higher
antegrade/positive shift

Question 4

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

Answer 4

less
retrograde/negative shift

Question 5

doppler shift basic calculation

Answer 5

Δf = f(received) - f(transmitted)

Question 6

doppler shift formula (not basic)

Answer 6

Δf = (2fo x v x cosO)/C

Question 7

doppler shift formula but for velocity

Answer 7

v= (Δf x C)/(2fo x cosO)

Question 8

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

Answer 8

increases

Question 9

if the angle of insonation increases = doppler shift _____

Answer 9

decreases

Question 10

doppler shift frequencies calculated by ______ (____)

Answer 10

fast Fourier transform (FFT)

Question 11

autocorrelation is the technique that analyzes _____ in a scan line

Answer 11

pulses

Question 12

autocorrelation determines the ___ and ____ of the blood flow

Answer 12

sign
mean velocity

Question 13

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

Answer 13

PRF
temporal

Question 14

Venous flow 4 characteristics

Answer 14

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

Question 15

what is the most under utilized control in Doppler

Answer 15

gain

Question 16

what does gain overcome

Answer 16

the attenuation of small RBCs and scatter

Question 17

if gain is too low =
too high=

Answer 17

poor visualization of spectral trace/colour fill
vs
creates artifacts

Question 18

scale (PRF) AKA

Answer 18

velocity range

Question 19

scale too low =
scale too high=

Answer 19

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

Question 20

how much space is above/below baseline for venous flow

arterial?

Answer 20

1/4 above
3/4 below

arterial = opposite

Question 21

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

Answer 21

echo

Question 22

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

Answer 22

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

Question 23

what do we do with the box angle in venous studies

Answer 23

woo hoo it

Question 24

gate size should be how big compared to vessel

Answer 24

1/3 size of the vessel

Question 25

gate size too big = too small =

Answer 25

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

Question 26

what does the wall filter do

Answer 26

eliminates low-frequency noise

Question 27

what does priority do

Answer 27

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

Question 28

priority high = low=

Answer 28

more colour vs grayscale shows instead of colour

Question 29

doppler noise/blooming

Answer 29

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

Question 30

doppler flash/clutter

Answer 30

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

Question 31

aliasing occurs when the _____ is exceeded

Answer 31

nyquist limit

Question 32

the Nyquist limit is what

Answer 32

1/2 PRF

Question 33

1/2 PRF usually falls between

Answer 33

5-30 kHz

Question 34

correcting for aliasing (5)

Answer 34

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

Question 35

what to corrections for aliasing can we actually do

Answer 35

move baseline increase PRF

Question 36

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

Answer 36

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

Question 37

power doppler is where what is measured

Answer 37

power or intensity of signal is measured rather than doppler shift

Question 38

power doppler is based on

Answer 38

density of RBCs not speed

Question 39

what is power doppler used for

Answer 39

assess small vessel, tissue perfusion, and slow flow

Question 40

does power doppler have aliasing

Answer 40

no

Question 41

what is less dependent on angle, doppler or power doppler

Answer 41

power