Physics and instrumentation

2. Course Name: Basics of Doppler
Course Code: MIDDU
Aqsa Hafeez
Lecturer
URISMIT- UOL

3. Doppler Waveform &
Indices

4. Learning objectives
By the end of this section, you will be able to
learn about:
Spectrograms
Phases of Spectrogram
Doppler Indices

5. Doppler waveform (Spectrograms)
• Doppler waveforms refer to the
morphology of pulsatile blood flow
velocity tracings on spectral Doppler
ultrasound. Waveforms differ by the
vascular bed (peripheral, cerebrovascular,
and visceral circulations) and the presence
of disease

6. There are three types of waveform that
describe the number of phases of flow in
each cardiac cycle.
•Triphasic
•Biphasic
•Monophasic
Doppler waveform (Spectrograms)

7. 1. Triphasic Waveform
Triphasic waveform having three
phases, due to crossing the zero flow
baseline twice in each cardiac cycle
• systolic forward flow
• early diastolic flow reversal (below
zero velocity baseline)
• late diastolic forward flow (slower than
in systole)

9. External Carotid Artery; Normal Waveform

10. 2. Biphasic Waveform
• Biphasic waveform having two phases or
variations having forward and reverse flow.
• systolic forward flow
• either of the following (controversial):
1. Diastolic flow reversal without late
diastolic forward flow (more common)
2. Zero diastolic flow reversal and
pandiastolic forward flow (slower than
in systole)

14. 3. Monophasic waveform
• Monophasic waveform having one phase
• systolic forward flow continuing into
diastole, lacking reverse diastolic flow,
which can be divided by
acceleration/deceleration time.
• sharp: fast systolic rise and fast
diastolic fall
• blunted: slow systolic rise and slow
diastolic fall

15. 1. Triphasic arterial flow is considered
normal in peripheral arteries and
monophasic flow is considered
abnormal .
2. Pulsatile venous flow is considered
abnormal and is suggestive of elevated
pressures in the right atrium.
Doppler waveform (Spectrograms)

16. 3. Diastolic flow reversal is generally
considered normal but pandiastolic
forward flow is abnormal in the peripheral
arteries . These categorizations differ for
the cerebrovascular and visceral
circulations, which normally have lower
resistance.

21. Waveform Indices
• Indices are defined as “ ratios of
velocities”. In ratio the angle factors
appear on both the top & bottom and
hence cancel each other out, so that the
index is independent of beam angle.

22. Waveform Indices
A number of most commonly encountered
indices are
• A/B Ratio
• Resistance Index
• Pulsatility Index
• Damping Factor
• Spectral Broadening

23. A/B Ratio
• The A/B ratio is the ratio of two specific
velocities at two points of cardiac cycle.
e.g Maximum velocities
• It is ususally employed where there is no
reverse flow in the waveform.

24. Resistance Index
• The resistive index is a calculated flow
parameter in Doppler Ultrasound, derived
from the maximum, minimum, and mean
Doppler frequency shifts during a defined
cardiac cycle.
• RI= PSV-EDV
PSV

25. Resistance Index
• It is also known as Pourcelot Index
• High resistance in the distal vessels
produces low diastolic flow in the
supplying artery and results in high value
for Resistive index
• A resistance results in a low value as there
is high diastolic flow.

26. Resistance Index
• As a vessel narrows and resistance to flow
increases, the RI will increase. The RI is
proportional to not only vascular
resistance but also vascular compliance.
• Different vessels and vascular beds have
different flow requirements, so there are
different normal RI values depending on
the target organ.

28. Pulsatility Index
• The pulsatility index (PI) (also known as
the Gosling index) is a calculated flow
parameter in Doppler ultrasound, derived
from the maximum, minimum, and
mean Doppler frequency shifts during a
defined cardiac cycle.

29. Pulsatility Index
• Pulsatility is an intrinsic property of the
cardiovascular system, governed by the
resistance differential across the arteriolar
bed.
• It allows the potential energy stored in the
elastic, proximal arteries to propagate
throughout the microcirculation at a mean
pressure consistent with adequate
perfusion.

30. PI = (peak systolic velocity - minimal diastolic velocity)
(mean velocity)
This ratio is used in vessels where reverse flow
may occur
e.g in lower limbs

32. Damping Factor
• The damping factor is defined as
“The ratio of pulsatility Indices at two sites
along an artery”
Damping factor = PI (proximal site)
PI ( Distal site)

33. Damping Factor
• The numerical value for this index
increases as the disease becomes more
severe
• Value of 2 being typical of high degree of
damping

34. References:
• Scissons R, Comerota A. Confusion of peripheral
arterial Doppler waveform terminology. Journal
of Diagnostic Medical Sonography. 2009;24 (4):
185-194
• W. Norman McDicken and Peter R. Hoskins.
Physics: Principles Practice and artefacts, 3rd
Edition.

35. Thanks!!