basics of ultrasound doppler

1. Doppler principles [1]
Dr. Kamal Sayed MBBS MSc US UAA

2. •
General principles
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Spectral specicific parameters
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Color specific parameters
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Power doppler imaging
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Normal flow in arteries
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Normal flow in veins

3. •
Doppler Effect & frequency shift
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1- The apparent change in frequency due to the relative
motion b/w the source & observer is known as the doppler
effect.
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2- doppler effect is the phenomenon that the wave
frequency changes when the distance b/w a source of sound
& a receiver of sound is changing :
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@ if objects are coming closer to each other [moving towards
each other], frequency increases [wave compressed &
shortened].
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4. •
@ if objects are moving farther away from each other,
frequency decreases [wave rarefied & lengthened].
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3- doppler effect refers to change in pitch of a sound due to
the motion either of the source or the listener.
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4- if 2 objects are approching each other, OR if an initial
object is approaching a 2ND standing object, the pitch is
higher.
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5- if 2 objects are moving apart, OR if an initial object is
moving apart from a 2ND standing object, the pitch is lower.
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•
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5. •
# IF source & observer are moving towards each other, the
pereceived [received] frequency [fr] is higher than the actual
[transmitted] frequency [ft].
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# IF source & observer are moving away from each other, the
pereceived [received] frequency [fr] is lower than the actual
[transmitted] frequency [ft].
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6- the change in loudness is the doppler frequency shift.
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7- doppler phenomenon is the difference b/w transmitted &
received frequencies.
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Slide [6]
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6. Doppler phenomenon

7. 1- US wave transmitted by a certain fequency from probe, US
waves will return from blood vessel by a different frequency.
2- the difference b/w both frequencies, is called frequency shift,
& represented as color OR spetrum.
3- doppler effect occur ONLY in moving objects; SO in occlusion
NO duplex color or spectrum is seen.

8. Df = 2 F0 V COS @ / C
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The perceived frequency [fr], is RELATED to the actual
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transmitted frequency [ft], AND the relative speeds of :
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@ source & @ waves in the medium, BY the
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doppler equation : slide [23]
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V = blood cells velocity [cm/s] /
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Df = doppler frequency shift [KHz]/
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C = speed of sound in soft tissue [1540 m/s] /
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F0 = original US transmitted fequency [MHz]/
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@ = cosine of angle b/w US TXR & blood flow direction/
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Df = 2 F0 V COS @ / C
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9. https://pt.slideshare.net/ahmedesawy543/duplex-ultrasound-doppler-waveform-changes-
242945335?qid=007f77a4-8223-4f08-a870-a44517ab2264&v=&b=&from_search=12
dr. ahmed elsawi

10. •
Positive OR negative frequency shifts
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A) SPECTRAL DOPPLER :
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1- flow towards probe, is above the baseline; a positive
frequency shift.
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2- flow away from probe, is below the base line; a negative
frequency shift.
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B) COLOR FLOW DOPPLER :
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1- towards probe is red color ; is a positive doppler shift.
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2- away from probe, is blue color; a negative frequency shift.
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Slide [25]
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11. Df = 2 F0 V COS @ / C

12. •
Positive OR negative frequency shifts
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A) SPECTRAL DOPPLER :
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1- flow towards probe, is above the baseline; a positive
frequency shift.
•
2- flow away from probe, is below the base line; a negative
frequency shift.
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B) COLOR FLOW DOPPLER :
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1- towards probe is red color ; is a positive doppler shift.
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2- away from probe, is blue color; a negative frequency shift.
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Slide [13]
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14. The received frequency is :
@ higher during approach.
@ identical at instant of passing by.
@ lower during receding [recession].
Doppler phenomenon
Df [doppler freq shift] = Ft [transmitted freq] – Fr [received freq]

15. •
Goals of doppler US
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1- detection flow in a vessel.
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2- detection direction of flow.
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3- detection type of flow : @ arterial or venous.
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@ normal or abnormal.
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4- measurement of flow velocity.

16. •
Types of doppler modalities :
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1- continuous wave doppler [CWD] (other types are all pulsed
wave doppler [PWD]).
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2- spectral [duplex] doppler.
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3- spectral & color [triplex] doppler.
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4- power doppler [PD].
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ALL doppler US examinations should be performed with :
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Grey-scale US, color doppler, spectral doppler, power doppler.

17. PULSED WAVE DOPPLER [PWD]
1- PWD employs elements of the transducer that send as well
as receive signals.
2- US is emitted as “pulses” between these pulses.
3- in PWD, the same TXR element receives the reflected signal
[one crystal] but in CWD 2 crystals are employed.
4- every emitted pulse is paired with a corresponding return
signal.

18. •
5- (PWD) uses the Doppler principle that moving objects
change the characteristic of sound waves.
@ By sending short and quick pulses of sound, it becomes
possible to accurately measure the velocity of blood in a
precise location and in real time.
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6 - PW allows us to measure blood velocities at a single point,
or within a small window of space.

19. 7- US waves are produced in pulses.
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@ Each pulse is 2-3 cycles of the same frequency.
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@ The pulse length [SPL] is the distance each pulse travels.
@The [PRF] is the rate at which the transducer emits
the pulses [the number of cycles emitted per seconds in Hz].
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In US imaging the significance of wavelength is
that short wavelengths are required to produce short pulses
for good anatomical detail (in the depth direction) and this
requires higher frequencies.

20. •
Factors affect PW reflected, on evaluation
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1- cardiac pump function : cardiac insufficiency.
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2- Aortic valve function : Aortic stenosis/insufficincy.
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3- course of vessel : tortuosity.
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4- peripheral vascular : @ periferal inflammation.
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@ polyneuropathy. @ warm or cold extremity. @ vasospastic
disorders.

21. •
spectral specific parametres [Slide [22]]
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1- base line . .
2- angle. / 3- angle correction cursor.
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4- doppler spectral gain.
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5- gate site. / 6- gate size [between bars].
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7- beam path.
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8- sample volume.
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Slide [22]
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22. Some spectral parameters

23. •
1] Base line
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1- the base line is depicted on both spectral waveform
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& the color bar.
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2- the base line divides the color bar into positive & negative
doppler shifts.
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3- adjusment of the base line alters the velocity range that is
displayed, & therefor used to prevent aliasis.
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4- color base line : the position of the base line on the color
bar is indicated by a horizontal black line [yellow circles]
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slide [25/26]
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24. @ Duplex US image in slide [25] LT image, demonstrates
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aliasing of the spectral waveform which produced inaccurate
waveform & quantitative flow data.
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@ same slide [25], RT image, spectral base line is lowered,
which resulted in a spectral waveform falling within the range
of velocities being evaluated, thus obtaining accurate
quantitative flow data.
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@ changing the base line will not change the velocity scale
[same PRF 1515 Hz], making base line adjustment a logical
initial change when solving aliasing.

26. Spectral base line different cases

27. Angle of insonation is b/w the TXR & vessel being studied.
Doppler angle is b/w US beam & blood flow being measured.
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2] doppler angle
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1- doppler Angle is the angle b/w the US beam & blood flow
being measured .
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2- The angle of insonation [b/w TXR & vessel being studied]
should be b/w 45° & 60° .
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3- the doppler angle corrects for the usual clinical situation
when an ultrasound beam is not parallel to the Doppler
signal
Slide [30/31]

28. 4- the Doppler angle of insonation has a significant effect on
spectral Doppler velocity measurements.
It is crucial that duplex criteria are standardised with a
fixed angle of insonation and that this angle is consistently
used during velocity estimations.
5- The strongest signal and best waveforms would be at zero
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degrees. Zero degrees is not usually clinically feasible,
however, so instead the probe is at some angle between
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0 (parallel) and 90 degrees (perpendicular), when evaluating
the vessel (usually between 30 and 60 degrees).
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Slide [34/35]

29. •
6- a higher-frequency doppler signal is obtained if the beam is
alligned more to the direction of flow.
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7- if the beam flow angle is almost 90^ there is a very poor
doppler signal.
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8- if the flow is away from the beam, there is a negative
signal
9- the larger the angle, the greater the
error.
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10- donot use angle > 60^, great error in velocity.
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11- angle 90^ [perpedicular], complete loss of flow.
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Slide [35/36]

30. [A] is more alligned than [B] & produces higher-frquency doppler signals.
[C] is almost 90^ with very poor doppler signal.
[D] is away from the beam & there is a negative shift.

32. •
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12- The US machine can correct a Doppler signal appropriately
if the TXR is angled less than 60 degrees from a vessel.
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It does not, however, know what angle you are using, so you
have to provide this information to the machine, usually via a
knob on the control panel.
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13- Cosine angle 90^ is zero [0], Cosine angle 0^ is one [1].
Slide [33]

33. Cosine angle 90^ is zero [0].
Cosine angle 0^ is one [1].

34. •
Angle correction
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[slides 36/38/40/41/42]
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1- angle correction is that the doppler angle b/w the US beam
& the blood flow is being measured, & is used to calibrate the
velocity scale.
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2- angle correction specifies the true doppler angle by placing
the cursor parallel to the direction of the blood flow.
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3- the angle of insonation is the angle b/w the TXR & vessel
being studied.
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4- angle < 60^, difference in speed is 10 – 15%, but
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angle > 60^, the difference in PSV is 30 – 35%.
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35. •
5- in slide [36] LT duplex image : @ obtained with NO angle
correction, shows how NO meaningfull velocity data from
the portal venous waveform, because the computer
automatically assigns an angle of 0^ [cosine 0 = 1].
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@ without angle corection, the measured flow velocity is
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18 cm/s.
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@ same slide [36] duplex RT image obtained with correct
definition of the angle b/w the TXR & direction of portal
venous flow, demonstrates a flow velocity of 29,3 cm/s.
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Slide [36]
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37. •
6- in slide [38]: @ LT duplex image obtained with a 30^
corrected angle, which is too low, demonstrates a flow
velocity of 21.3 cm/s in the portal vein.
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@ same slide [39] RT image duplex obtained with a 70^
corrected angle, which is too high, demonstrates a flow
velocity of 52.8 m/s in the portal vein, which represents an
overestimation of flow velocity.
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@ NOTE that, the measured flow velocity increases as the
corrected angle increases.
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Slide [39]

39. •
7- in slide [40] LT & middle duplex images of the anterior
branch of the RT portal vein : @ obtained with TXR positioned
in an intercostal location [LT image], & subcostaln [middle
image].
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@ LT & middle images, depict flow as moving toward & away
from the TXR respectively.
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@ RT duplex image same slide [41], TXR positioned
perpendicular to flow [arrow], NO color is assigned, yielding
a false finding of absent flow. The angle of insonation of the
vein depends entirely on the position of the TXR.
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Slide [41]
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43. •
3] velocity scale [PRF]
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1- velocity scale is the range of flow velocities that are
depicted with either the color or spectral component.
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2- if the measured flow velocity falls outside the selected
scale, aliasing of the currently active scanning mode will
occur.
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3- Spectral Doppler echocardiography uses US to record
the velocity, direction, and type of blood flow in the
cardiovascular system.
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44. •
4- in a color duplex US image, setting the spectral scale
[sampling rate] too high : e.g PRF 14,286 Hz, flow is more
difficult to appreciate & characterize on the scale.
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5- in the same duplex image, when the scale [PRF] is reduced
to 3,731 Hz, the appearance of the spectral wave is
improved, providing more visible quantitative & qualititative
data.
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6- NOTE that the CFD US image, color bar, & color scale, all
remain unchanged because the spectral component is active.
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Slide [45]

46. •
7- the spectral waveform typically makes use of 265 pulse
cycles per scan line, & contains qualitative & quantitative
diagnostic information for interpretation.
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8- on the other hand, the color map contains only 8 pulse
cycles per scan line, thereby providing considerably less
information.
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slide [47]