PowerPoint's presentation about Doppler in obstetrics

2. Christian Andreas Doppler
An Austrian mathematician
and physicist.
He formulated the principle
now known as the Doppler
effect.
The observed frequency of a
wave depends on the relative
speed of the source and the
observer.

3. Doppler is the mainstay of the
diagnosis and management of high-risk
pregnancies.
Fetal arterial and venous Doppler
parameters indicate the likelihood of
the fetus being healthy, hypoxic, or
acidaemic.

4. Doppler modalities are based on
three fundamental principles.
(1) Moving structures change the
frequency and amplitude of reflected
ultrasound signals.
Moving structures include not only blood,
but also fetal vessels or tissues. This can
generate a shift in the backscattered signals.

5. (2) Analysis of the components of the
reflected signals are utilized for different
Doppler modalities: the shift in frequency
for directional color and spectral Doppler,
and the shift in amplitude for power
Doppler ultrasound (PDU).

6. (3) All color and power Doppler
modalities are pulsed techniques, while
spectral Doppler can be pulsed or
continuous.

7. PRF( pulse repetition frequency)
or scale, is the number of times a pulsed
activity occurs every second, frequency of
signals (pulses).
A low PRF allows signals from slow
moving targets to reach the transducer
before the next pulse is emitted.
A high PRF will allow only high velocities
to reach the ultrasound transducer before
the next pulse.

8.  The wall filter
Is a barrier defined by a specific threshold
frequency below which signals are not
displayed in the Doppler image.
Gain
Is the amplification of signals. The
quality and reproducibility of the
recordings can be improved by knowledge
of these Doppler settings and how to adjust
them

9. Doppler assessment of the placental circulation
plays an important role in:
 Screening for impaired placentation and its
complications as preeclampsia, intrauterine
growth restriction and perinatal death.
 Assessment of the fetal circulation is
essential in the better understanding of the
pathophysiology of a wide range of
pathological pregnancies and their clinical
management

10. Three key components for Competent use of
Doppler U/S:
(1) The capabilities and limitations of Doppler
ultrasound.
(2) The different parameters which contribute to
the flow display.
(3) Blood flow in arteries and veins.

11. Doppler flow velocity waveform and
gestational age:
The amount of perfusion in trophoblastic tissue
is related to gestational age.
For this reason, in interpreting the Doppler
findings, gestational age must be taken into
account.
Nomograms for Doppler measurements should
be standardized according to gestational age.

12. In the routine use of ultrasound in practice, the
accepted time for starting Doppler sonographic
examinations is the beginning of the second
trimester.
This is the right time that allows modifications
in antenatal care in a high-risk pregnancy.
For specific conditions, earlier timing of
measurements may be considered.

14. Flow imaging modes
Spectral Doppler
• Examines flow at one site.
• Detailed analysis of distribution of flow.
• Good temporal resolution – can examine flow waveform.
• Allows calculations of velocity and indices.
Color flow
• Overall view of flow in a region
• Limited flow information
• Poor temporal resolution/flow dynamics (frame rate can be
low when scanning deep)
• Color flow map (different color maps)
• Direction information
• velocity information (high velocity & low velocity)
• Turbulent flows

15. Indications:
Fetal indications
• Fetal growth restriction.
• Poor perinatal outcome.
• Twin-twin transfusion.
Maternal conditions
Diabetes mellitus Chronic kidney disease
Hypertension Pro-thrombotic states
Pregnancy-related conditions
Suspected IUGR
Previous pregnancy with IUGR or fetal death in utero
Decreased fetal movement Oligohydramnios
Polyhydramnios Multifetal pregnancy

16. Vessels needed to be examined
• Umbilical artery
• Middle cerebral artery
• Uterine artery
• Umbilical vain
• IVC
• Ductus venosus

19. The umbilical artery was the first fetal vessel
to be evaluated by Doppler velocimetry.
Placental blood is assessed by studying the
umbilical artery.
Flow velocity waveforms from the umbilical
cord have a characteristic saw-tooth appearance
of arterial flow in one direction and continuous
umbilical venous blood flow in the other.

21. UA waveforms are slightly different at the fetal
abdominal wall and at the placental insertion,
with indices higher at the wall than the insertion.
However, the difference is minimal, so it is not
important to obtain the waveforms always at the
same level.
In practice, the UA is best examined in a
segment of free floating umbilical cord.

24.  Normal impedance to flow
in the umbilical arteries and
normal pattern of pulsatility
at the umbilical vein in 1st
trimester
 Normal impedance to flow
in the umbilical arteries and
umbilical vein in early 2nd
trimester
 Normal impedance to flow
in the umbilical arteries and
umbilical vein in late 2nd
and 3rd trimester.

29. The middle cerebral artery is the vessel of
choice to assess the fetal cerebral circulation
why?
 Easy to identify
 Highly reproducible
 Provides information on the brain-sparing
effect.
MCA should be sampled soon after its origin
from the ICA.

30. Normal middle cerebral artery waveform

31. BRAIN SPARING EFFECT
IUGR is associated with increased blood flow
to the fetal brain.
This increase in blood flow during diastole can
be demonstrated by Doppler ultrasound of the
MCA.
This effect is termed the brain-sparing effect
and is demonstrated by a low value of the MCA
PI.

33. Doppler recordings from umbilical artery (UA), middle cerebral artery (MCA)(middle)
for the control and the three intrauterine growth restricted (IUGR) fetuses with
present (PEDF), absent(AEDF) or reverse (REDF) umbilical artery end-diastolic flow.

34. Indications of MCA Doppler:
Preterm SGA:
Limited accuracy, should not be used.
Term SGA:
If normal UAD and abnormal MCA-D (PI<5th
percentile) moderate predictive value for
acidosis at birth, used to time the delivery.
Fetal anemia:
Pronounced MCA PI due to increased fetal
heart rate and decreased blood viscosity.

36. Advantages of MCD:
I. Middle cerebral artery Doppler is more
sensitive in predicting fetal anemia
II. Better than UAD
III. Non invasive technique better than
amniocentesis

38. A computational model of the fetal circulation
was developed, including the key elements
related to fetal blood redistribution and using
measured cardiac outflow profiles to allow
personalization.
The model was first calibrated using patient-
specific Doppler data from a healthy fetus.

39. Next, aortic isthmus(AoI) and middle cerebral
artery(MCA) flow changes were studied by
variation of cerebral and peripheral-placental
resistances.
Finally, to study how this affects an individual
fetus, the model was fitted to three IUGR cases
with different degrees of severity.

42. In conclusion, the proposed computational
model provides a good approximation to assess
blood flow changes in the fetal circulation.
The results support that while MCA flow is
mainly determined by a fall in brain resistance,
the AoI is influenced by a balance between
increased peripheral-placental and decreased
cerebral resistances.
Personalizing the model allows for quantifying
the balance between cerebral and peripheral-
placental remodeling, thus providing potentially
novel information to aid clinical follow up.

43. NORMAL MIDDLE CEREBRAL ARTERY
WAVEFORM
IUGR

47. The Ductus venosus originates from
the umbilical vein, its diameter
measure one- third of that of the
umbilical vein.

48. It is a shunt between the intra-
abdominal umbilical vein and
inferior vena cava (IVC)that directs
well-oxygenated blood through the
foramen ovale into the left heart,
thus feeding the coronary and
cerebral circulation.

49. The Ductus venosus characterized by
high blood velocity which ensures high
kinetic energy needed for streaming,
also reflects the pressure gradient
that drives venous liver perfusion.

50. The blood flow velocity waveform,
particularly the deflection during atrial
contraction, is commonly used in
hemodynamic evaluation of the fetus,
for example in fetal growth restriction.

51. Moderate predictive value, mainly
used for preterm small for gestational
age with abnormal umbilical artery
Doppler and to recognize time of
delivery.

59. The uterine artery waveform by the mid-
second trimester is characterized by high end
diastolic velocities (EDVS) with continuous
forward blood flow throughout diastole.
The diastolic component of uterine artery
Doppler waveform is transformed during
normal pregnancy from low peak flow velocity
with early diastolic notch, to high flow velocity
with early diastolic notch.

60. Ifthe end diastolic flow does not increase
throughout pregnancy, or if a small notch is
detected at the beginning of diastole, the fetus
is at high risk for developing IUGR.
Diastolic blood flow may be absent or even
reversed with extreme degrees of placental
dysfunction.

63. Abnormal Uterine Artery [18-24 Weeks]
 Bilateral notch with mean RI >0.55
 Unilateral notch with mean RI >0.65
 R.I.: >0.58>26 WKS :
 Difference between right & left uterine artery
S/D ratio > 1.0
 Important is normograph of PI of uterine
artery. PI should go down as the pregnancy
advances.

64. Doppler spectra of Ut.A flow

67. The IVC, before its entrance into
the right atrium, has a triphasic
pulsatile pattern. The first forward
wave begins to increase with atrial
relaxation, reaches a peak during
ventricular systole, and then falls at
the end of ventricular systole.

68. The second forward wave occurs
during early diastole, and the third
wave, characterized by reversed
flow, is present in late diastole with
atrial contraction.

69. In healthy fetuses, a significant
decrease of the reversed flow during
atrial contraction is present with
advancing gestation.
In IUGR fetuses the IVC is
characterized by an increase in
reversed flow during atrial
contraction.