Doppler EchocardiographyDoppler Echocardiography

Alex Tan M.D.Alex Tan M.D.

7/15/20097/15/2009

Doppler vs. B-mode Echo- Doppler vs. B-mode Echo- complementary rolescomplementary roles

Primary target is the Primary target is the red blood cellred blood cell

Examine the Examine the direction, velocity, direction, velocity, and pattern of blood and pattern of blood flow through the heart flow through the heart and the great vessels.and the great vessels.

Primary target are the Primary target are the myocardium and the myocardium and the heart valvesheart valves

Provides information Provides information about the shape and about the shape and movement of cardiac movement of cardiac structures. structures.

OutlineOutline

Doppler EffectDoppler Effect

Continuous wave DopplerContinuous wave Doppler

Pulse wave DopplerPulse wave Doppler

Color DopplerColor Doppler

Tissue DopplerTissue Doppler

New research applying principles of New research applying principles of doppler echodoppler echo

Christian DopplerChristian Doppler

Austrian mathematician Austrian mathematician and physicistand physicist

Published his notable Published his notable work on the “Doppler work on the “Doppler Effect” at the age of 39Effect” at the age of 39

To explain the color of To explain the color of binary stars.binary stars.

Was Gregory Mendel’s Was Gregory Mendel’s physics professor in the physics professor in the University of Vienna.University of Vienna.

1803-1853

Doppler EffectDoppler Effect

““Observed frequency of a Observed frequency of a wave depends on the wave depends on the relative speed of the relative speed of the source and observer”source and observer”The pitch of sound was The pitch of sound was affected by motion toward affected by motion toward or away from the listeneror away from the listenerSound moves toward the Sound moves toward the listener, frequency listener, frequency increases, pitch rises.increases, pitch rises.Sound moves away from Sound moves away from the listener, frequency the listener, frequency decreases, pitch falls.decreases, pitch falls.

Doppler effect applied to Doppler effect applied to EchocardiographyEchocardiography

Transducer emits Transducer emits ultrasound reflected from ultrasound reflected from RBC.RBC.If RBC (flow of blood) If RBC (flow of blood) moves toward transducer, moves toward transducer, frequency of the reflected frequency of the reflected sound’s wavelength sound’s wavelength increasesincreasesIf RBC (flow of blood) If RBC (flow of blood) moves away from the moves away from the transducer, frequency of transducer, frequency of the reflected sound’s the reflected sound’s wavelength decreaseswavelength decreases

Doppler effect applied to Doppler effect applied to EchocardiographyEchocardiography

Transducer emits Transducer emits ultrasound reflected from ultrasound reflected from RBC.RBC.If RBC (flow of blood) If RBC (flow of blood) moves toward transducer, moves toward transducer, frequency of the reflected frequency of the reflected sound’s wavelength sound’s wavelength increasesincreasesIf RBC (flow of blood) If RBC (flow of blood) moves away from the moves away from the transducer, frequency of transducer, frequency of the reflected sound’s the reflected sound’s wavelength decreaseswavelength decreases

Doppler Shift and VelocityDoppler Shift and Velocity

FFdd: Doppler shift= Fr (received frequency)- F: Doppler shift= Fr (received frequency)- F00 (transmitted (transmitted frequency)frequency)FF00: Transmitted frequency of ultrasound: Transmitted frequency of ultrasoundV: velocity of blood.V: velocity of blood.: intercept angle between the interrogation beam and the target: intercept angle between the interrogation beam and the targetCan solve for V=FCan solve for V=Fdd(C)/2f(C)/2f00(cos (cos C= speed of sound in bloodC= speed of sound in blood

Importance of blood flow velocityImportance of blood flow velocity

Modified Bernoulli’s equation:Modified Bernoulli’s equation: P= 4vP= 4v22

Gives us the ability to estimate pressure Gives us the ability to estimate pressure differences between differences between – two chambers (i.e, TR)two chambers (i.e, TR)– Stenotic valves (i.e. AS)Stenotic valves (i.e. AS)

Angle of the Doppler beamAngle of the Doppler beamcos (0cos (0°°)= 1)= 1

cos (10cos (10°°)= 0.98)= 0.98

cos (20cos (20°°)= 0.94)= 0.94

cos (30cos (30°°)= 0.87)= 0.87

cos (60cos (60°°)= 0.5)= 0.5

cos (90cos (90°°)= 0)= 0

Fd= 2fFd= 2f00(V)(cos (V)(cos )/C)/C

Fd Fd V(cos V(cos ))Misalignment of the Misalignment of the interrogation beam interrogation beam will lead to will lead to underestimation of underestimation of the true velocitythe true velocityBecomes significant Becomes significant when when is >20 is >20°°

Carrier frequencyCarrier frequency

V=Fd(C)/2fV=Fd(C)/2f00(cos (cos ))If Fd stays the same, the lower the fIf Fd stays the same, the lower the f00 (carrier frequency), (carrier frequency), the higher the velocity of the jet that can be resolved.the higher the velocity of the jet that can be resolved.Unlike B-mode imaging where higher frequency Unlike B-mode imaging where higher frequency transducer gives better resolution, here lower frequency transducer gives better resolution, here lower frequency transducers gives better resolution.transducers gives better resolution.

Fd

Carrier frequencyCarrier frequency

V=Fd(C)/2fV=Fd(C)/2f00(cos (cos ))If Fd stays the same, the lower the fIf Fd stays the same, the lower the f00 (carrier frequency), (carrier frequency), the higher the velocity of the jet that can be resolved.the higher the velocity of the jet that can be resolved.Unlike B-mode imaging where higher frequency Unlike B-mode imaging where higher frequency transducer gives better resolution, here lower frequency transducer gives better resolution, here lower frequency transducers gives better resolution.transducers gives better resolution.

Fd

Spectral analysisSpectral analysis

The difference in waveform The difference in waveform between the transmitted and between the transmitted and backscattered signal is backscattered signal is compared.compared.Data processed by Fourier Data processed by Fourier transform (FFT) to display a transform (FFT) to display a spectral range of velocitiesspectral range of velocitiesTime- x axisTime- x axis

1.1. Velocity- y axisVelocity- y axis2.2. Direction - toward the Direction - toward the

transducer is positive, away transducer is positive, away from transducer negative.from transducer negative.

3.3. Amplitude - “brightness” of Amplitude - “brightness” of the signal.the signal.

Continuous wave dopplerContinuous wave doppler

Two dedicated crystals- one for transmitting and Two dedicated crystals- one for transmitting and one for receiving.one for receiving.Receives a continuous signal along the entire Receives a continuous signal along the entire length of the ultrasound beamlength of the ultrasound beamDisadvantage- don’t know where the signal Disadvantage- don’t know where the signal comes from.comes from.Advantage- can measure very high Doppler Advantage- can measure very high Doppler shift/velocities.shift/velocities.Most useful when trying to discern maximal Most useful when trying to discern maximal velocity along a certain path (AS, TR…etc).velocity along a certain path (AS, TR…etc).

Clinical example- ASClinical example- AS

The position of the The position of the doppler beam is 2-D doppler beam is 2-D guided.guided.

Profile is usually filled Profile is usually filled in- velocity along the in- velocity along the path that is below the path that is below the maximal velocity also maximal velocity also represented.represented.

Problematic casesProblematic cases

Don’t know where the maximal velocity comes Don’t know where the maximal velocity comes fromfrom

Serial stenosis- LVOT obstruction or AS?Serial stenosis- LVOT obstruction or AS?

Problematic casesProblematic cases

AS or MR?AS or MR?

Pulse wave dopplerPulse wave doppler

Short intermittent busts of ultrasound are transmitted.Short intermittent busts of ultrasound are transmitted.Only “listens” at a brief time intervalOnly “listens” at a brief time intervalPermits returning signal from one specific distance to be Permits returning signal from one specific distance to be selectively analyzed- “range resolution”selectively analyzed- “range resolution”Sample volumeSample volume

Clinical ExamplesClinical Examples

position of doppler beam position of doppler beam 2-D guided2-D guidedIn GE system, the sample In GE system, the sample volume is indicated by volume is indicated by double linesdouble linesSpectral envelope not Spectral envelope not filled infilled inCommon use- mitral Common use- mitral inflow velocity and LVOT inflow velocity and LVOT velocityvelocity

AliasingAliasing

Sampling rate is inadequate to resolve the Sampling rate is inadequate to resolve the direction of flowdirection of flowNyquist limit= PRF/2Nyquist limit= PRF/2PRF (pulse repetition frequency) - number of PRF (pulse repetition frequency) - number of pulse transmitted from the transducer/secondpulse transmitted from the transducer/second

AliasingAliasing

Tends to happen in at Tends to happen in at greater depthgreater depth

Sample volume at a Sample volume at a shallow site- can shallow site- can interrogate more interrogate more frequently (higher PRF)frequently (higher PRF)

Sample volume at deeper Sample volume at deeper site- cannot interrogate site- cannot interrogate as often (lower PRF)as often (lower PRF)

AliasingAliasing

Tends to happen at higher velocity jetsTends to happen at higher velocity jets

Methods to overcome aliasing include baseline Methods to overcome aliasing include baseline shift, continuous doppler, high PRF imaging. shift, continuous doppler, high PRF imaging.

High PRF imagingHigh PRF imagingShallower sample volume associated with a higher PRF- less likely Shallower sample volume associated with a higher PRF- less likely to have aliasingto have aliasingListening window will also sample returning signal from twice that Listening window will also sample returning signal from twice that depthdepthVelocity from both sites will be recordedVelocity from both sites will be recordedDisadvantage: range ambiguityDisadvantage: range ambiguityAdvantage: Higher velocities can be analyzed without aliasingAdvantage: Higher velocities can be analyzed without aliasing

ColorColor DopplerDoppler

pulse wave Doppler with multiple sample volume pulse wave Doppler with multiple sample volume along multiple scan linesalong multiple scan lines

direction, velocity and variance determined for direction, velocity and variance determined for each sample volumeeach sample volume

Color DopplerColor DopplerDisplayed as color information-Displayed as color information-– Amplitude - intensityAmplitude - intensity– Direction- red vs blue (toward or away from Direction- red vs blue (toward or away from

transducer)transducer)– Velocity- brightness (bright blue higher Velocity- brightness (bright blue higher

velocity)velocity)– Variance (turbulence)- coded green to give a Variance (turbulence)- coded green to give a

mosiac apperance.mosiac apperance.Overlays this information on 2D imagesOverlays this information on 2D imagesTime consuming (temporal resolution is Time consuming (temporal resolution is especially poor with a large sector window)especially poor with a large sector window)

Example of Color DopplerExample of Color Doppler

Color Gain

Semiquantitative methodSemiquantitative method

Color codes velocity and Color codes velocity and not actual volume!not actual volume!Angiography- contrast is Angiography- contrast is actual regurgitationactual regurgitationColor doppler encodes Color doppler encodes “billard ball effect”- color “billard ball effect”- color may encode non-may encode non-regurgitant blood that is regurgitant blood that is “pushed around” by the “pushed around” by the regurgitant jet.regurgitant jet.

Tissue Doppler ImagingTissue Doppler Imaging

Routine Doppler targets blood flowRoutine Doppler targets blood flow– High velocityHigh velocity– Low signal amplitudeLow signal amplitude

Tissue Doppler (assessing the movement of the Tissue Doppler (assessing the movement of the myocardium) targets tissuemyocardium) targets tissue– Low velocityLow velocity– High signal amplitudeHigh signal amplitude

Different FiltersDifferent Filters

Example of pulse TDIExample of pulse TDI

Velocity of tissue along a particular sample volume

Example of Color TDIExample of Color TDI

Velocity of tissue coded by color superimposed on 2-D image

Can derive information such as strain, strain rate, dyssynchrony…etc.

Applications of tissue dopplerApplications of tissue doppler

1036 patients from community based population study1036 patients from community based population study

Do patients with normal LV by conventional echo but Do patients with normal LV by conventional echo but abnormal systolic and diastolic function by TDI have abnormal systolic and diastolic function by TDI have increased mortality?increased mortality?

Background

TDI assessing LV systolic and diastolic function has been shown to have prognostic significance.

However, data conflicting.

Has not been applied to a large community population.

MethodsMethods

Conventional echo (2D, MM, PD mitral)Conventional echo (2D, MM, PD mitral)– To rule out patients with LVEF<50%, severe To rule out patients with LVEF<50%, severe

diastolic dysfunction, LVH, LV dilatationdiastolic dysfunction, LVH, LV dilatation

Color TDI: Color TDI: – 6 mitral annular positions6 mitral annular positions– Peak systolic (s’), early diastolic (d’), late Peak systolic (s’), early diastolic (d’), late

diastolic (a’)diastolic (a’)

Color TDI parameters

– E/e’E/e’– e’/a’e’/a’– e’/(a’x s’)e’/(a’x s’)

Patient characteristicsPatient characteristics1100 patients studied 1100 patients studied

19 excluded for AF or 19 excluded for AF or significant significant valvulopathyvalvulopathy

45 excluded for poor 45 excluded for poor quality images.quality images.

ResultsResults

Model 1: adjusted for age and sexModel 1: adjusted for age and sex

Model 2: adjusted for LVH, LV dilatation, LVEF<50%Model 2: adjusted for LVH, LV dilatation, LVEF<50%

Model 3: included only those with normal conventional echoModel 3: included only those with normal conventional echo

Prognostic significance of Prognostic significance of Eas indexEas index

Kaplan Meier Survival curves of age and sex adjusted tertiles of Eas [e’/(a’ x s’)]

Incremental value of TDI in Incremental value of TDI in predicting mortalitypredicting mortality