DOPPLER ULTRASOUND in Pregnancy

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DOPPLER ULTRASOUND in Pregnancy

• Dr. Mohammed AbdallaEgypt, Domiat Hospital

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Doppler History

• First use of Doppler ultrasonography to study
• flow velocity in the fetal umbilical artery
• was reported in 1977

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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

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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.
• .

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• 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.

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T2
T1
pulse repetition frequency
(T2 T1) phase shift with known beam / flow
angle can calculate flow velocity .
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Basic Principals

• The time difference or phase shift are then
  proceeded to produce either colorflow display or
  a
• Doppler sonogram

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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
• flow velocity increased .
• beam is more aligned to the direction of
  
• flow.
• higher transducer frequency is used.

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Factors affecting doppler frequency
Freq.
3
2
The angle of insonation
q
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.

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(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.
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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.
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Aliasing

• So to eliminate aliasing The pulse repetition
  frequency or scale is set appropriately for the
  flow velocities

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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.

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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.

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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

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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

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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.

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Umbilical artery doppler
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Doppler indices
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Umbilical artery
UMBILICAL ARTERY FLOW characteristic saw-tooth
appearance of arterial flow in one direction and
continuous umbilical venous blood flow in the
other.
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FACTORS AFFECTING UMBILICAL ARTERY DOPPLER FLOW
VELOCITY WAVEFORMS
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Umbilical artery

• Benefit of Umbilical Artery Evaluation
• Less experienced operators can achieve highly
  reproducible results with simple, inexpensive
  continuous-wave equipment .

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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 .
• .

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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.

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• Middle cerebral artery doppler

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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
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Middle cerebral artery
The blood velocity increases with advancing
gestation, and this increase is significantly
associated with the decrease in PI
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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
•      
•  
•  

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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

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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

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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)

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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
Almstrom et al 1992 Biljan et al 1992 Johnstone
et al 1993 Pattison et al 1994 Nienhuis et al
1997

• Trudinger et al 1987
• McParland et al 1988
• Tyrrell et al 1990
• Hofmeyr et al 1991
• Newham et al 1991
• Burke et al 1992

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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)

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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 .

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Biophysical profile for fetal assessment inhigh
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.
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Thank you