Principles of Doppler ultrasound
Samir Haffar M.D.Department of Internal Medicine
General principles
Spectral-specific parameters
Color-specific parameters
Power Doppler imaging
Normal flow in arteries
Normal flow in veins
Principles of Doppler ultrasound
General principles of Doppler ultrasound
Christian Doppler (1803 – 1853) Famous for what is called now the “Doppler effect”
1841 Professor of mathematics & physics Prague polytechnic
1842 Published his famous book “On the colored light of the binary stars & some other stars of the heavens”
1850 Head of institute of experimental physics Vienna University
Austrian physicist
The Doppler effectProposed by Christian Doppler in 1842
• Change in frequency of a wave for an observer movingrelative to the source of the wave
• Commonly heard when a vehicle sounding a sirenapproaches, passes, & recedes from an observer
• Received frequency Higher during approachIdentical at instant of passing byLower during recession
What is the Doppler phenomenon?
Thrush A, Hartshorne T. Peripheral vascular ultrasound: how, why and when.Elsevier Churchill Livingstone, London, 2nd edition, 2005.
= ft
> ft
= ft
< ft
What is the Doppler phenomenon?
Doppler shift frequency (fd): ft – fr
Thrush A, Hartshorne T. Peripheral vascular ultrasound: How, why and when.Elsevier Churchill Livingstone, London, 2nd edition, 2005.
ft
fr
Doppler equation
∆ F Doppler shift frequency (kHz)
F0 Ultrasound transmission frequency (MHz)
V Blood cell velocity (cm/sec)
Cos ӨCos of angle between US & flow direction
C Speed of sound in soft tissue (1 540 m/sec)
∆ F = 2 F0 V Cos Ө / C
Goals of Doppler
• Detection flow in a vessel
• Detection direction of flow
• Detection type of flow: Arterial or venous Normal or
abnormal
• Measurement the velocity of flow
Types of Doppler
Continuous wave Doppler
Spectral Doppler (duplex)
Spectral & color Doppler (triplex)
Power Doppler
All Doppler ultrasound examinations shouldbe performed with:
Tahmasebpour HR et al. RadioGraphics 2005 ; 25 : 1561 – 1575.
• Gray-scale US
• Color Doppler
• Spectral Doppler
• Power Doppler
Spectral-specific parameters
Spectral Doppler
Angle correctioncursor
Beam path
Sample volume
Baseline
EDV
Thrush A, Hartshorne T. Peripheral vascular ultrasound: How, why and when.Elsevier Churchill Livingstone, London, 2nd edition, 2005.
PSV
Doppler shift frequency & angle of insonation
Thrush A, Hartshorne T. Peripheral vascular ultrasound: How, why and when.Elsevier Churchill Livingstone, London, 2nd edition, 2005.
Use of spectral baseline
Normal baseline
Inverted baseline
Dropping baseline
Sample volume length
Large sample volume lengthSmall sample volume length
Thrush A, Hartshorne T. Peripheral vascular ultrasound: How, why and when.Elsevier Churchill Livingstone, London, 2nd edition, 2005.
Optimizing gate size & position
Kruskal JB et al.RadioGraphics 2004 ; 24 : 657 – 675.
Wide gate including PV (above baseline) & HV (below baseline)
Gate should be positioned over central part of the studied vessel
Doppler equation
∆ F Doppler shift frequency (kHz)
F0 Ultrasound transmission frequency (MHz)
V Blood cell velocity (cm/sec)
Cos ӨCos of angle between US & flow direction
C Speed of sound in soft tissue (1 540 m/sec)
∆ F = 2 F0 V Cos Ө / C
Percentage error in velocity measurements & angle of insonation
In order to minimize this error,angles of insonation > 60% should not be used
Optimizing Doppler angle Larger the angle, greater the error
• Ideally should be zero Usually not possible • Smallest angle possible Not under our control• Do not use angle > 60° Great error in velocity• Angle 90° Complete loss of flow
• Transducer position Obtain smaller angle
• Different US systems May be different results
Thrush A, Hartshorne T. Peripheral vascular ultrasound: How, why and when.Elsevier Churchill Livingstone, London, 2nd edition, 2005.
Doppler angle measurement
Angle: 60°PSV: 110 cm/secEDV: 41 cm/sec
Angle: 44°PSV: 74 cm/secEDV: 27 cm/sec
Thrush A et al. Peripheral vascular ultrasound. Elsevier Churchill Livingstone, London, 2005.
Changing position of the transducer
IntercostalTransabdominal Subcostal
Kruskal JB et al.RadioGraphics 2004 ; 24 : 657 – 675.
Adjusting spectral velocity scale
Spectral scale: 200 cm/sec Spectral scale: 50 cm/sec
Kruskal JB et al.RadioGraphics 2004 ; 24 : 657 – 675.
Color Doppler image, color bar, & color scale unchanged Spectral component is active
Adjusting spectral Doppler gain Gain setting 0% Gain setting 38%
Gain setting 77% Gain setting 100%
Kruskal JB et al.RadioGraphics 2004 ; 24 : 657 – 675.
Spectral wall filter
Wall filter 75 Hz
Wall thump removed
Wall filter 550 Hz
Filter frequency too high
Altered waveform
Wall filter 50 Hz
Wall thump
Thrush A, Hartshorne T. Peripheral vascular ultrasound: How, why and when.Elsevier Churchill Livingstone, London, 2nd edition, 2005.
Spectral aliasing CCA
Dropping baseline Increasing scalePeaks cross baseline
Rubens DJ et al. Doppler artifacts & pitfalls. Ultrasound Clin 2006 ; 1 : 79 – 109.
Color-specific parameters
Color map
BaselineWall filter
Changing color baseline
Kruskal JB et al.RadioGraphics 2004 ; 24 : 657 – 675.
When color baseline changed → color velocity range changed
Range of depicted velocities remains constant
Examples of different color maps
Thrush A, Hartshorne T. Peripheral vascular ultrasound: How, why and when.Elsevier Churchill Livingstone, London, 2nd edition, 2005.
Velocity range(cm/sec)
Inversion ofcolor map
Color writepriority
Baselinewall filter
Inversion of color flow
Kruskal JB et al.RadioGraphics 2004 ; 24 : 657 – 675.
Reversal of this inversionAppropriate directional flow noted
Portal venous flow appears blueFalsely suggests flow reversal
Inversion of spectral flow
Kruskal JB et al.RadioGraphics 2004 ; 24 : 657 – 675.
Color box size / Overlay
Kruskal JB et al.RadioGraphics 2004 ; 24 : 657 – 675.
Oversized color box↑ frame rate & ↓ resolution
Reduced color box size↓ frame rate & ↑ resolution
Color box should be as small & superficial as possible
Doppler angle effects
Thrush A, Hartshorne T. Peripheral vascular ultrasound: How, why and when.Elsevier Churchill Livingstone, London, 2nd edition, 2005.
Color box steeringChanging angle of insonation
Large angleUnusable image
Small angleGood image
Moderate angleFlow is not optimal
Steered either left or right by a maximum of 20 – 25° Sensitivity of transducer decreases as beam is steered
Thrush A et al. Peripheral vascular ultrasound. Elsevier Churchill Livingstone, 2nd edition, 2005.
Color box steered in more than one direction to demonstrate flow in the whole vessel
Color box steering
Thrush A et al. Peripheral vascular ultrasound. Elsevier Churchill Livingstone, 2nd edition, 2005.
Adjusting color velocity scale
Kruskal JB et al.RadioGraphics 2004 ; 24 : 657 – 675.
Color velocity scale 2 cm/secColor aliasing in PV & its branches
High color velocity scale (69 cm/sec)Apparent absence of flow in PV
Color velocity scale 30 cm/sec Normal flow in a patent PV
Color Doppler aliasing
Velocity scale range 12 cm/sec Velocity scale range 23 cm/sec
Rubens DJ et al. Doppler artifacts & pitfalls. Ultrasound Clin 2006 ; 1 : 79 – 109.
Portal vein pseudo-clot
Velocity scale: 20 cm/s Velocity scale: 7 cm/s
Adjusting color gain
Kruskal JB et al.RadioGraphics 2004 ; 24 : 657 – 675.
Color gain should be set as high as possible without displaying random color speckles
Color gain 44% Color gain 65% Color gain 100%
Adjusting color gain
Flow ‘bleeding out’ of the vesselColor gain set too high
Thrush A, Hartshorne T. Peripheral vascular ultrasound: How, why and when.Elsevier Churchill Livingstone, London, 2nd edition, 2005.
Adjusting color wall filter
Filter setting displayed on color scale (horizontal arrow)
Filter too high Removing low flow
Filter setting reduced Display low flow
Thrush A, Hartshorne T. Peripheral vascular ultrasound: How, why and when.Elsevier Churchill Livingstone, London, 2nd edition, 2005.
Pseudo-thrombosis of main PV Adjusting velocity & angle of insonation
Velocity: 24 cm/secWall filter: medium
Angle 90°
Velocity: 7 cm/secWall filter: medium
Angle < 90°
Radiol Clin N Am 2006 ; 44 : 805 – 835.
Doppler panel on console of many contemporary US imagers
Each parameter can be adjusted to optimize spectral or
color Doppler components of the examination
Kruskal JB et al.RadioGraphics 2004 ; 24 : 657 – 675.
Clinical & tissue-specific presets
• Clinical option GeneralAdultObstetric (etc…)
• Tissue-specific preset AbdomenRenalTransplant (etc...)
Kruskal JB et al.RadioGraphics 2004 ; 24 : 657 – 675.
Once a transducer selected
preset choices includes:
Guidelines for optimal Doppler examination
Adjust gain & filter
Adjust velocity scale & baseline
Doppler angle < 60° by steering & probe position
Color box as small & superficial as possible
Sample volume size: 2/3 of vessel width in the center
Avoid transducer motion
Rubens DJ et al. Doppler artifacts & pitfalls. Ultrasound Clin 2006 ; 1 : 79 – 109.
Power Doppler imaging
Advantages of power mode Doppler
• No aliasing
• Angle independent
• Increased sensitivity to detect low-velocity flow Distinguish pre-occlusive from occlusive lesionsSuperior depiction of plaque surface morphology
• Useful in imaging tortuous vessels
• Increases accuracy of grading stenosis
Power Doppler imaging
Large plaque ulcerICA
Narrow flow channel in ICA“string sign” or “trickle flow ”
Disadvantages of power Doppler imaging
• Do not provide velocity of flow
• Do not provide direction of flowNew machines provide direction of flow in power mode
• Very motion sensitive (poor temporal resolution)Less suitable for rapid scan along vessels
Normal flow in arteries & veins
Flow at a curvature & bifurcation
Myers KA & Clough A. Making sense of vascular ultrasound. Arnold, London, 2004.
Apex of parabola moves away from concave wall at a curve
Apex of parabola moves away from outer wall at bifurcation
Flow around curves in a vessel
Tortuous ICA
Thrush A, Hartshorne T. Peripheral vascular ultrasound: How, why and when.Elsevier Churchill Livingstone, London, 2nd edition, 2005.
A B
A
PSV outside the bend 70 cm/sec
B
PSV inside the bend 55 cm/sec
Normal flow reversal zone in ICA
Opposite to origin of the ECAHigh velocities near flow divider
Reversal on opposite side to flow divider
Thrush A et al. Peripheral vascular ultrasound. Elsevier Churchill Livingstone, London, 2005.
High & low resistance arterial flow
High-resistance flowSFA
Low-resistance flowICA
Myers KA & Clough A. Making sense of vascular ultrasound. Arnold, London, 2004.
Arterial high resistance flow
Typical normal Doppler spectra
Normal anterior tibial arteryTriphasic flow
Pulsatility index
Most commonly used of all indices
S Systolic
D Minimum diastolic
M Mean
PI S – D / M
Effect of exercise on flow
Dorsalis Pedis Artery at restTriphasic flow
Thrush A, Hartshorne T. Peripheral vascular ultrasound: How, why and when.Elsevier Churchill Livingstone, London, 2nd edition, 2005.
DPA following exerciseMonophasic hyperemic flow
Arterial monophasic flow
• HyperemicExercise Infection Temporary arterial occlusion by blood pressure cuff
• Distal to severe stenosis or occlusion Low velocity Longer rise time* Tardus-Parvus wave
* Rise time: time between beginning of systole & peak systole
Tardus-Parvus waveDistal to severe stenosis or occlusion
Thrush A, Hartshorne T. Peripheral vascular ultrasound: How, why and when.Elsevier Churchill Livingstone, London, 2nd edition, 2005.
Tardus: Longer rise time
Parvus: Low PSV
Arterial low resistance flowTypical normal Doppler spectra
Normal internal carotid artery
Pourcelot’s resistance index
RI S – ED / S
Normal 50 – 70 %
Abnormal > 80 %
Accleration Time (AT) or Rise Time (RT)
• Length of time in seconds from
onset of systole to peak systole
• Normal value: ≤ 0.07 second
Acceleration index
AI = X (KHz)
Probe frequency (MHz)
Normal value: > 3.8 cm/s2
Aacleration time & PSV
Early systolic pick
AJR - Dec 1995
Biphasic with late systolic pick
Monophasic with late systolic pick
AT & AI according to degree of stenosis
Moderate stenosis 50 – 85%
Normal Severe stenosis> 85 %
Measurement of volume flow
Volume = Cross-sectional area × Mean velocity × 60 (ml/min) (cm2) (cm/sec)
Cross-sectional area (cm2): π d2 / 4d: diameter
Doppler equationConverting Doppler shift frequency to velocity
∆ F Doppler shift frequency (kHz)
F0 Ultrasound transmission frequency (MHz)
V Blood cell velocity (cm/sec)
Cos ӨCos of angle between US & flow direction
C Speed of sound in soft tissue (1 540 m/sec)
∆ F = 2 F0 V Cos Ө / C
∆ F
F0
V ?
Cos Ө
C
∆ F = 2 F0 V Cos Ө / C
50 cm/s
1.6 kHz
5 MHz
60°
1 540 m/sec
Thrush A, Hartshorne T. Peripheral vascular ultrasound: How, why and when.Elsevier Churchill Livingstone, London, 2nd edition, 2005.
Doppler equationConverting Doppler shift frequency to velocity
Blood flow & PSV changes relatedto severity of arterial stenosis
Myers KA & Clough A. Making sense of vascular ultrasound. Arnold, London, 2004.
Flow through a stenosis
Thrush A, Hartshorne T. Peripheral vascular ultrasound: How, why and when.Elsevier Churchill Livingstone, London, 2nd edition, 2005.
Increased velocity through stenosis Flow reversal beyond stenosis
CCA
IJV
ICA
Color from red to turquoise Posterior wall – deep blue
Pic Systolic Velocity ratio
Robbin ML et al. Ultrasound Clin 2006 ; 1 : 111 – 131.
Proximal: 2 cm proximal to stenosis
Same Doppler angle if possible
Post-stenotic zone/Spectral broadeningProportional to severity of stenosis
• Cannot be precisely quantified (evaluated visually)Fill-in of spectral window > 50% diameter reductionSeverely disturbed flow > 70% diameter reduction
High amplitude & low frequency signalLow amplitude & high frequency signalFlow reversal – Poor definition of spectral
border
• May be only sign of stenosis: calcified plaque
Spectral broadeningImmediate post-stenotic zone
Pseudospectral broadening
• High gain setting
• Vessel wall motion
• Site of branching
• Abrupt change in vessel diameter
• ↑ velocity: athlete, high cardiac output, AVF1, & AVM2
• Tortuous vessels
• Aneurysm, dissection, & FMD3
1AVF: Arterio-Venous Fistula2AVM: Arterio-Venous Malformation3FMD: Fibro-Muscular Dysplasia
Color Doppler bruit
Extensive soft tisuue color Doppler bruit surrounds
the carotid bifurcation with 90% ICA stenosis
Venous valve
Two cups of a valve clearly seenIt is uncommon to see venous valves with this clarity
Normal venous flow
Spontaneity Spontaneous flow without augmentation
Phasicity Flow changes with respiration
Compression Transverse plane
Augmentation Compression distal to site of examination Patency below site of examination
Valsalva Deep breath, strain while holding breath Patency of abdominal & pelvic veins
Normal venous flow
Spontaneity Spontaneous flow without augmentation
Phasicity Flow changes with respiration
Compression Transverse plane
Augmentation Compression distal to site of examination Patency below site of examination
Valsalva Deep breath, strain while holding breath Patency of abdominal & pelvic veins
Phasicity
Flow changes with respiration
Slow ApneaRapid
Normal venous flow
Spontaneity Spontaneous flow without augmentation
Phasicity Flow changes with respiration
Compression Transverse plane
Augmentation Compression distal to site of examination Patency below site of examination
Valsalva Deep breath, strain while holding breath Patency of abdominal & pelvic veins
Compressibility of veins
Do not press too hard since the normal vein collapsesvery easily making it difficult to find
11
Incompressibility = Thrombus
Do not compress vein more than necessary in recent thrombusFear of detaching thrombus to cause PE
Myers KA & Clough A. Making sense of vascular ultrasound. Arnold, London, 2004.
External compression of the vein
Relaxation Compression
A
Normal venous flow
Spontaneity Spontaneous flow without augmentation
Phasicity Flow changes with respiration
Compression Transverse plane
Augmentation Compression distal to site of examination Patency below site of examination
Valsalva Deep breath, strain while holding breath Patency of abdominal & pelvic veins
Augmented flow in popliteal vein
Aug Competent vein
Normal venous flow
Spontaneity Spontaneous flow without augmentation
Phasicity Flow changes with respiration
Compression Transverse plane
Augmentation Compression distal to site of examination Patency below site of examination
Valsalva Deep breath, strain while holding breath Patency of abdominal & pelvic veins
Valsalva’s maneuver
Valsalva’s maneuver
A V
Normal respiration
A V
Valsalva maneuver
Start Valsalva
End Valsalva
Competent vein
Indicate on the report whether
the examination was excellent, good or poor
Emphasize if a scan is suboptimal
Myers KA & Clough A. Making sense of vascular ultrasound. Arnold, London, 2004.
References
Arnold – 2004 Elsevier – 2005 Elsevier Mosby – 2005
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