Doppler Principles

Question 1

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

Answer 1

doppler effect

Question 2

what is the Doppler effect

Answer 2

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

Question 3

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 ____

Answer 3

closer together
higher
further apart
lower

Question 4

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

Answer 4

blood flow
qualitatively
quantitatively

Question 5

doppler can give you the following info (3)

Answer 5

presence of flow
direction of flow
quality of flow

Question 6

doppler information is provided by (3)

Answer 6

spectral tracing
colour image
audible sound

Question 7

duplex scanning

Answer 7

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

Question 8

triplex scanning

Answer 8

scanning 2D image, doppler, and colour doppler

Question 9

RBC diameter and what it means

Answer 9

7 um
smaller than typical wavelength = Rayleigh scatter

Question 10

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

Answer 10

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

doppler shift = received f - transmitted f

Question 11

basic doppler formula

more detailed doppler formula

formula that means most to us as sonographers

Answer 11

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

3. v = (Δf x c) / (2fo x cos0)

Question 12

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

Answer 12

increases
linear

Question 13

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

Answer 13

lower

Question 14

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

Answer 14

increases
increasing
linear

Question 15

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

Answer 15

0
cant

Question 16

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

Answer 16

velocity
down (due to cosine of angle)

Question 17

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

Answer 17

increases

Question 18

Nyquist limit

Answer 18

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)

Question 19

the Nyquist limit is equal to ____ the PRF

Answer 19

1/2

Question 20

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

Answer 20

aliasing

Question 21

1/2 PRF usually falls between _____ kHz

Answer 21

5-30

Question 22

why does aliasing occur

Answer 22

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

Question 23

how can the Nyquist limit help with a diagnosis

Answer 23

plaque in lumen increasing velocity = exceeds Nyquist limit = aliasing

Question 24

how to know if it is aliasing rather than reversal

Answer 24

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

Question 25

correcting for aliasing can be accomplished by (5)

Answer 25

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

Question 26

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

Answer 26

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

Question 27

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

Answer 27

is

Question 28

the sample volume is created because of the ____

Answer 28

range equation

Question 29

sample volume determined by (3)

Answer 29

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

Question 30

the ____ the pulse duration the more accurate the beat frequency

Answer 30

longer

Question 31

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

Answer 31

4 opposite to 2D scanning where short PD is best

Question 32

range gating ____ possible with continuous wave doppler

Answer 32

not

Question 33

zone of sensitivity

Answer 33

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

Question 34

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

Answer 34

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

Question 35

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

Answer 35

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

Question 36

what is power in spectral tracing proportionate to

Answer 36

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

Question 37

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

Answer 37

peak systolic velocity envelope window dicrotic notch end diastolic velocity

Question 38

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

Answer 38

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

Question 39

Fast Fourier Transform (FFT)

Answer 39

the process in which the system creates a spectral trace

Question 40

y axis of spectral analysis represented by

Answer 40

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

Question 41

frequency on a spectral analysis is expressed in and velocity too

Answer 41

kHz or Hz cm/s or m/s

Question 42

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

Answer 42

towards to probe (pos number) away from the probe (neg number)

Question 43

blood can be categorized as ____, _____, or ____

Answer 43

high moderate low pulsatility

Question 44

how else can the pusitility of blood be referred as

Answer 44

resistance (high, mod, low)

Question 45

what is the determining factor to blood pulsitility

Answer 45

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

Question 46

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

Answer 46

tall, narrow systolic peaks reversed or absent diastolic flow common in extremities (CFA)

Question 47

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

Answer 47

broad systolic peaks (rapid upstroke, comes down slower) forward flow through diastole (doesn't reverse/cross baseline) feeding vital organs (ICA)

Question 48

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

Answer 48

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)

Question 49

4 qualitative assessments of a waveform

Answer 49

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

Question 50

5 quantitative assessments of a waveform

Answer 50

pulsatility index resistive index doppler shift peak velocity mean velocity

Question 51

pulsatility index is used to _______ and its formula

Answer 51

quantify the impedance to flow like in the presence of a stenosis PI = (A-B)/mean velocity A=PSV B= furthest away velocity

Question 52

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

Answer 52

change in pulsatility S/D ratio= A/B A= PSV B=EDV

Question 53

when S/D ratio increases, resistance ____

Answer 53

increases

Question 54

acceleration formula

Answer 54

Acceleration = Δv / ΔT V=PSV T= time from start to PSV

Question 55

spectral broadening

Answer 55

the vertical thickening of the spectral trace or envelope all v at same time=thin line greater range of v=spectral broadening

Question 56

false spectral broadening

Answer 56

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

Question 57

A mathematical technique that rapidly asses the Doppler shift signal to determine the mean, luminance and variance

Answer 57

AUTOCORRELATION

Question 58

A colour coding technique that employs the amplitude of the Doppler shifts thus being less angle dependant and more sensitive to low flow states

Answer 58

power doppler

Question 59

The area of interest for pulsed wave spectral Doppler comprised of the beam width, the receiver gate and the emitted pulse

Answer 59

sample volume

Question 60

This occurs when the second scan line is sent out before the first one has returned. It is a possibility when performing Doppler in a high PRF mode

Answer 60

range ambiguity

Question 61

The continuous wave region of interest for spectral Doppler where the transmitted and received beam intersect

Answer 61

zone of sensitivity