doppler echocardiography

1. Doppler echocardiography
Dr.S.R.SRUTHI MEENAXSHI MBBS,MD,PDF

2. BASICS
• A moving target will backscatter an ultrasound beam to the
transducer so that the frequency observed when the target is
moving toward the transducer is higher and the frequency
observed when the target is moving away from the transducer is
lower than the original transmitter frequency

3. Doppler effect
• Christian Andreas Doppler was
an
Austrian mathematician and phy
sicist.
• He is celebrated for his principle
– known as the Doppler effect –
that the observed frequency of a
wave depends on the relative
speed of the source and the
observe

4. Doppler effect

6. • V

7. DOPPLER SHIFT
• Doppler shift (F[d]) = F[r] - F[t]
• Blood flow velocity (V) is related to the Doppler shift by the
speed of sound in blood (C) and ø, the intercept angle between
the ultrasound beam and the direction of blood flow. A factor of
2 is used to correct for the "round-trip" transit time to and from
the transducer.
• F[d] = 2 x F[t] x [(V x cos ø)] ÷ C
• This equation can be solved for V, by substituting (F[r] - F[t])
for F[d]:
• V = [(F[r] -F[t]) x C] ÷ (2 x F[t] x cos ø)

8. • Note that the angle of the
ultrasound beam and the
direction of blood flow are
critically important in the
calculation
• ●For ø of 0º and 180º (parallel
with blood flow), cosine ø = 1
• ●For ø of 90º (perpendicular to
blood flow), cosine ø = 0 and
the Doppler shift is 0
• ●For ø up to 20º, cos ø results
in a minimal (less than 10
percent) change in the Doppler
shift
• ●For ø of 60º, cosine ø = 0.50

9. SPECTRAL ANALYSIS
• Spectral analysis — When the backscattered signal is
received by the transducer, the difference between the
transmitted and backscattered signal is determined by
comparing the two waveforms with the frequency content
analyzed by fast Fourier transform (FFT).
• The display generated by this frequency analysis is termed
spectral analysis. By convention, time is displayed on the x
(horizontal) axis and frequency shift on the y (vertical) axis.
• On spectral Doppler, shifts toward the transducer are
represented as "positive" deflections from the "zero" baseline,
and shifts away from the transducer are displayed as "negative"
deflections

11. DOPPLER MODALITIES
• Doppler methods used for cardiac evaluation:
• continuous wave
• pulsed wave
• color flow

12. CONTINUOUS WAVE DOPPLER (CW)
• Continuous wave Doppler employs two dedicated ultrasound
crystals: one for continuous transmission and a second for
continuous reception of ultrasound signals.
• This permits measurement of very high frequency Doppler shifts
or velocities.
• receives a continuous signal along the entire length of the
ultrasound beam.

13. CW DOPPLER PROFILE
• ideal Doppler profile is one with a smooth "outer" contour, well-
defined edge and maximum velocity, and abrupt onset and
termination
• The continuous wave Doppler profile is usually "filled in"
because lower-velocity signals proximal and distal to the point
of maximum velocity are also recorded.
• Continuous wave Doppler is typically used to measure higher
velocities as in pulmonary hypertension and aortic stenosis

14. CONTINUOUS WAVE DOPPLER

16. PULSE WAVE DOPPLER (PW)
• pulsed wave Doppler permits sampling of local blood flow
velocities at a specific region (or sample volume).
• This modality is particularly useful for assessing the relatively
low velocity flows associated with
• mitral or tricuspid inflow, pulmonary venous flow, left atrial
appendage flow, left ventricular outflow, or right ventricular
outflow blood flows

17. • To permit this, an ultrasound pulse is transmitted and then the
receiver "listens" during a subsequent interval defined by the
distance from the transmitter and the sample site.
• This transducer mode of transmit-wait-receive is repeated at an
interval termed the pulse-repetition frequency (PRF). The PRF
is therefore depth-dependent, being greater for near regions
and lower for distant or deeper regions.
• The width and length of the sample volume is varied by
adjusting the length of the transducer "receive" interval. Pulsed
Doppler is always performed with 2D guidance to determine the
optimal sample volume position.

18. • pulsed Doppler, the PRF is determined by the maximum depth
of the Doppler signals

20. NYQUIST LIMIT and ALIASING PHENOMENON
• The Nyquist limit defines the frequency at which aliasing and
range ambiguity will occur, and is equal to the PRF/2.
• The Nyquist limit defines when aliasing will occur using PW
Doppler. The Nyquist limit specifies that measurements of
frequency shifts (and, thus, velocity) will be appropriately
displayed only if the pulse repetition frequency (PRF) is at least
twice the maximum velocity (or Doppler shift frequency)
encountered in the sample volume.

21. COLOR FLOW DOPPLER
• Doppler color flow imaging is based upon the principles of
pulsed wave Doppler echocardiography.
• Along each scan line, a pulse of ultrasound is transmitted, and
the backscattered signals are then received from each "gate" or
sample volume along each line. In order to calculate accurate
velocity data, several bursts along each scan line are used,
known as the burst length.

22. • With color flow imaging, velocities are displayed using a color
scale,
• flow toward the transducer typically displayed in orange/red
• flow away from the transducer displayed as blue.
• Lighter shades are assigned higher velocities within the Nyquist
limit
• aliasing is depicted as color reversal.

23. • Turbulent flow is characterized by varied blood velocities and
directions.
• The variance of velocities within jets is usually color coded as a
multicolored mosaic display.

28. Tissue doppler imaging
• Tissue Doppler imaging is a form of pulsed wave Doppler that is
used for recording myocardial tissue velocity.
• Tissue Doppler early diastolic signal from the mitral annulus in
the apical view is used in evaluation of left heart diastolic
function, while tissue Doppler systolic recording from the
tricuspid annulus or basal right ventricular free wall in the apical
four chamber view may be used to aid in the assessment of
right ventricular systolic function,

30. Bernoulli equation
• he Bernoulli Equation can be considered to be a statement of
the conservation of energy principle appropriate for flowing fluids.
• The qualitative behavior that is usually labeled with the term "Bernoulli
effect" is the lowering of fluid pressure in regions where the flow velocity is
increased.
• In the high velocity flow through the constriction, kinetic energy must
increase at the expense of pressure energy.

31. Bernoulli principle
• This states that, in a steady flow, the sum of all forms of energy
in a fluid along a streamline is the same at all points on that
streamline. This requires that the sum of kinetic
energy, potential energy and internal energy remains
constant.[Thus an increase in the speed of the fluid – implying
an increase in its kinetic energy (dynamic pressure) – occurs
with a simultaneous decrease in (the sum of) its potential
energy (including the static pressure) and internal energy

33. RELATIONSHIP BETWEEN DOPPLER
VELOCITY AND PRESSURE
GRADIENT
• One of the most powerful attributes of Doppler
echocardiography is the ability to estimate the pressure
difference across a stenotic valve (eg, aortic stenosis) or
• between two chambers (eg, estimation of the pulmonary artery
systolic pressure from the tricuspid regurgitation velocity).

34. • This relationship is defined by the Bernoulli equation and is
dependent on the velocity proximal to a stenosis (V1), velocity
in the stenotic jet (V2), density of blood (p), acceleration of
blood through the orifice (dv/dt), and viscous losses (R[v]). The
pressure gradient (ΔP) can be calculated from:
• ΔP = [0.5 x p x (V2 x V2 - V1 x V1)] + [p x (dv/dt)] + R[v]
• If one assumes that the last two terms (acceleration and
viscous losses) are small and then enters the constants, the
formula is simplified to:
• ΔP (mmHg) = 4 x (V2 x V2 - V1 x V1)

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