Transcript Ultrasonic Imaging - Echocardiography & Ultrasound Institute

DOPPLER ULTRASOUND
There are three major types of
Blood flow Doppler patterns:
1) Continuous Wave
2) Pulse Wave
3) Color Flow
What can We Measure with Doppler
Ultrasound?
• Velocities: Most calculations
start with this parameter
• Direction of Blood Flow
• Pressure Gradients
The Doppler Principle is the basis of many
applications
Beam alignment is crucial for
accurate velocity measurements
V = velocity of blood flow
C = speed of sound in blood
FT = transducer frequency
FS = backscatter frequency
Cos ϴ = cosine of angle
between US beam & blood flow
As the angle of the incident beam
and the direction of blood increases
the measured velocity decreases
and the error increases
DOPPLER BEAM
MEASURED BLOOD FLOW
VELOCITY VECTOR WHEN
BEAM IS NOT PARALELL
BLOOD FLOW
VELOCITY VECTOR
Effects of Intercept Angle in Velocity
Measurements can not be ignored beyond 20
degrees
Pulse Wave, Continuous Wave & Color Flow
Color Flow Principle is similar to
PW with multiple sector scans
SPECIFIC APPLICATION OF DOPPLER
MEASUREMENTS
• Pulsed Wave Doppler
– Stroke Volume Measurement
• Continuous Wave Doppler
– Peak velocity measurement
• Color Doppler
– Blood Volume flow & direction
Pulsed Wave Doppler
• Measures the blood velocity at a specific
location or sample volume
• Exact localization of moving objects
• Limited maximum velocity measurement
because of Nyquist Limit (more on this
later)
Pulsed Wave Doppler from transmittal
flow to evaluate diastolic function
Continuous Wave Doppler
• Measures the Maximum Velocity in a
specific direction ( vs location for PW)
• Essentially no limit in the maximum
velocity measurement (no Nyquist limit)
• The site of the maximum velocity cannot
be localized
Continuous Wave Doppler
MR JET VELOCITY PROFILE DURING
SYSTOLE, NOTE DIRECTION AND MAX
VELOCITY
Color Doppler
• Multiple sampling with pulsed wave
Doppler along the 2D scan lines.
• The quantity and direction of velocity are
measured in every point.
• The intensity of the signal represents
number of moving cells
• Movement away from the transducer is
blue and movement toward the transducer
is red.
Color Doppler Parasternal long axis
(LAX)
Blood Velocity Curves
• Can be measured any where there is
flow and an Acoustic Window
• Basic calculus is used to analyze the
velocity curves to obtain the Stroke
Volume (SV) and Cardiac Output
PW vs. CW thru the Mitral Valve
Pulse Wave Thru Pulmonary Veins:
Effects of Turbulence
CONTINUOUS DOPPLER WAVES
CAN BE USED TO MEASURE:
STROKE VOLUME
CARDIAC OUTPUT
STOKE VOLUME WITH
VELOCITY TIME INTERGRAL
STROKE VOLUME & CARDIAC OUTPUT
INTERGRAL
OF BLOOD
VELOCITY
DISTANCE
TRAVELED BY
BLOOD
DISTANCE TRAVELED BY
BLOOD
AREA OF FLOW
VOLUME OF
BLOOD
(STROKE VOLUME)
Stroke Volume Measurement
thru LV out flow tract (LVOT)
• SV = CSALVOT x VTILVOT
SV = Stroke Volume
CSA = Cross Sectional Area
VTI = Velocity Time Integral
LVOT = Left Ventricular Outflow Track
Measuring Pressure
Gradients
Measuring Pressure Gradients
Continuous Wave Doppler for
Pressure Gradient
• Pressure Gradient = 4 x V2
• Pressure Gradient = 4 x V21 – V22
– Measuring maximum gradient
through the narrowest area of the
flow
– Requires measuring the maximum
velocity thru the area of flow with
CW
SUMMARY
• Doppler measurements have
numerous applications in
echocardiography.
• We can also measure the velocity of
intra-cardiac structures (myocardium
or valves) and assess their function or
dysfunction.
SUMMARY
• Understanding Echocardiography
Physics will enhance our
understanding of:
• The physical principles that affect our
measurements and images
• Knowing when to believe or doubt our results
• The strengths and limitations of the technology