2. Doppler History
First use of Doppler
ultrasonography to study
flow velocity in the fetal
umbilical artery
was reported in 1977
3. Doppler History
Fitzgerald & Drumm. Umbilical artery studies 1977BMJ
Eik-Nes et al. Fetal aortic velocimetry : Dupplexscanner
1980 Lancet
Campbell et al. Utero-placental circulation: Dupplex
scanner 1983 Lancet
Wladimiroff et al. MCA / UA PI ratio 1987 OG
Kiserud et al. Ductus venosus velocimetry 1991Lancet
4. Basic principals
Echoes from stationary tissues are the same from
pulse to pulse.
Echoes from moving objects exhibit slight
differences in the time for the signal to be
returned to the receiver.
These differences can measured as phase shift
from which the Doppler frequency is obtained.
5. T1 : time of omitted signal .
T2 : time of returned signal .
T2 – T1 = time difference or phase
shift .
from phase shift the Doppler
frequency is obtained.
AS TIME DIFFERENCE DECREASE THE
DOPPLER FREQUENCY INCREASE.
6. T2
pulse repetition frequency
T1
(T2 –T1) phase shift with known beam / flow angle can
calculate flow velocity .
7. Basic Principals
The time difference or phase shift
are then proceeded to produce
either colorflow display or a
Doppler sonogram
8. Basic Principals
‘Doppler frequency’ is obtained by measuring
the time difference for the signal to be returned
when reflected from moving scatterers .
Doppler frequency increase if:
1. flow velocity increased .
2. beam is more aligned to the direction of
flow.
3. higher transducer frequency is used.
9. Factors affecting doppler frequency
q
3
2
The angle of insonation
Flow velocity
1
(the angle q between the beam and the direction of
flow becomes smaller). This is of the utmost
importance in the use of Doppler ultrasound.
10. (the angle q between the beam and the direction of flow
becomes smaller). This is of the utmost importance in the
use of Doppler ultrasound.
beam (A) is more aligned than (B)
The beam/flow angle at (C) is almost 90° and there is a very poor Doppler signal
The flow at (D) is away from the beam and there is a negative signal.
11. Aliasing
If a second pulse is sent before the first is received, the receiver cannot
discriminate between the reflected signal from both pulses and aliasing
occur.
12. Aliasing
So to eliminate aliasing The
pulse repetition frequency or
scale is set appropriately for
the flow velocities
13. Basic Principals
The volume flow in the UAs
increases with advancing
gestation. The high vascular
impedance detected in the first
trimester gradually decreases. It is
attributed to growth of placental
unit and increase in the number of
the functioning vascular channels.
14. Uses
plays a vital role in the diagnosis of
fetal cardiac defects .
assessment of the hemodynamic
responses to fetal hypoxia and
anemia.
diagnosis of other non-cardiac
malformations.
15. Anatomy
Blood supply provided by
the ovarian and uterine
arteries
Uterine Arteries: main
branches of the internal
iliac arteries
Uterine Arteries: Ascend
through the lateral wall and
anastomose with the
ovarian arteries
16. Anatomy
Arcuate Arteries: Run Circumferentially around the uterus
Uterus: Blood supply to anterior and posterior walls
provided by the Arcuate arteries
Radial Arteries: Extend from the arcuate arteries and
enter the endometrium
Spiral Arteries: connect the maternal circulation to the
endometrium
Responsible for a 10 fold increase in blood flow
17. Anatomy
Conversion of small muscular spiral arteries into large
vascular channels transforms the uteroplacental
circulation into a low-resistance-to-flow system. These
have a dilated and tortuous lumen, a complete absence
of muscular and elastic tissue, no continuous
endothelial lining.
20. Umbilical artery
UMBILICAL ARTERY FLOW
characteristic saw-tooth appearance of arterial
flow in one direction and continuous umbilical
venous blood flow in the other.
22. Umbilical artery
Benefit of Umbilical Artery Evaluation
Less experienced operators can achieve
highly reproducible results with simple,
inexpensive continuous-wave
equipment .
23. Umbilical artery
The 40% of the combined fetal ventricular output is
directed to the placenta by two umbilical arteries.
The assessment of umbilical blood flow provides
information on blood perfusion of the fetoplacental
unit .
24. Umbilical artery
With advancing gestation,
umbilical arterial Doppler
waveforms demonstrate a
progressive rise in the
end-diastolic velocity and
a decrease in the
pulsatility index.
26. The possible Doppler velocimetry sites
Middle cerebral artery
Using color flow imaging, the middle cerebral artery can be
seen as a major lateral branch of the circle of Willis, running
anterolaterally at the borderline between the anterior and the
middle cerebral fossae
27. Middle cerebral artery
The blood velocity increases with advancing gestation,
and this increase is significantly associated with the
decrease in PI
28. Middle cerebral artery
An early stage in fetal adaptation to hypoxemia -
central redistribution of blood flow
( brain-sparing reflex)
increased blood flow to protect the brain, heart,
and adrenals
reduced flow to the peripheral and placental
circulations
29. Doppler wave form of early stage of
fetal hypoxemia
increased end-diastolic flow in the middle
cerebral artery (lower MCA pulsatility
index or resistance index)
Average of both MCAs must be calculated
for more precise result
30. Middle Cerebral Artery
Flow velocity waveform in the fetal middle cerebral artery
in a severely anemic fetus at 22 weeks (left) and in a
normal fetus (right). In fetal anemia, blood velocity is
increased
31. Middle Cerebral Artery
When the fetus is hypoxic, the cerebra arteries
tend to become dilated in order to preserve
the blood flow to the brain and The systolic to
diastolic (A/B) ratio will decrease (due to an
increase in diastolic flow)
32. Doppler ultrasound for the fetal assessment in
high-risk pregnancies
(Cochrane Review). In: The Cochrane Library,
1999. Neilson JP and Alfirevic Z
11 Studies Included In Analysis
Trudinger et al 1987
McParland et al 1988
Tyrrell et al 1990
Hofmeyr et al 1991
Newham et al 1991
Burke et al 1992
Almstrom et al 1992
Biljan et al 1992
Johnstone et al 1993
Pattison et al 1994
Nienhuis et al 1997
33. Doppler ultrasound for the fetal assessment
in high-risk pregnancies
Meta analysis
Nearly 7000 patients were included
The trials compared no Doppler ultrasound to
Doppler ultrasound in high-risk pregnancy
(hypertension or presumed impaired fetal
growth)
34. Doppler ultrasound for the fetal assessment
in high-risk pregnancies
Main results
A reduction in perinatal deaths.
Fewer inductions of labour .
Fewer admissions to hospital .
no report of adverse effects .
No difference was found for fetal distress
in labour .
No difference in caesarean delivery .
35. Biophysical profile for fetal assessment in
high risk pregnancies
• When compared with conventional fetal monitoring
(usually cardiotocography) biophysical profile
testing showed no obvious effect (either beneficial
or deleterious) on pregnancy outcome. There was
an increase in the number of inductions of labour
following biophysical profile in the trial.
Alfirevic Z, Neilson JP. Biophysical profile for fetal assessment in high risk
pregnancies (CochraneReview). In: The Cochrane Library, 1995.
