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Principles of Doppler ultrasound

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Principles of Doppler ultrasound

  1. 1. Principles of Doppler ultrasoundSamir Haffar M.D.Department of Internal Medicine
  2. 2.  General principles Spectral-specific parameters Color-specific parameters Power Doppler imaging Normal flow in arteries Normal flow in veinsPrinciples of Doppler ultrasound
  3. 3.  General principles of Doppler ultrasound
  4. 4. Christian Doppler (1803 – 1853)Famous for what is called now the “Doppler effect”1841 Professor of mathematics & physicsPrague polytechnic1842 Published his famous book“On the colored light of the binary stars& some other stars of the heavens”1850 Head of institute of experimental physicsVienna UniversityAustrian physicist
  5. 5. 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
  6. 6. 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
  7. 7. What is the Doppler phenomenon?Doppler shift frequency (fd): ft – frThrush A, Hartshorne T. Peripheral vascular ultrasound: How, why and when.Elsevier Churchill Livingstone, London, 2nd edition, 2005.ftfr
  8. 8. Doppler equation∆ F Doppler shift frequency (kHz)F0 Ultrasound transmission frequency (MHz)V Blood cell velocity (cm/sec)Cos Ө Cos of angle between US & flow directionC Speed of sound in soft tissue (1 540 m/sec)∆ F = 2 F0 V Cos Ө / C
  9. 9. Goals of Doppler• Detection flow in a vessel• Detection direction of flow• Detection type of flow: Arterial or venousNormal or abnormal• Measurement the velocity of flow
  10. 10. Types of Doppler Continuous wave Doppler Spectral Doppler (duplex) Spectral & color Doppler (triplex) Power Doppler
  11. 11. 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
  12. 12.  Spectral-specific parameters
  13. 13. Spectral DopplerAngle correctioncursorBeam pathSample volumeBaselineEDVThrush A, Hartshorne T. Peripheral vascular ultrasound: How, why and when.Elsevier Churchill Livingstone, London, 2nd edition, 2005.PSV
  14. 14. Doppler shift frequency & angle of insonationThrush A, Hartshorne T. Peripheral vascular ultrasound: How, why and when.Elsevier Churchill Livingstone, London, 2nd edition, 2005.
  15. 15. Use of spectral baselineNormal baselineInverted baselineDropping baseline
  16. 16. Sample volume lengthLarge sample volume lengthSmall sample volume lengthThrush A, Hartshorne T. Peripheral vascular ultrasound: How, why and when.Elsevier Churchill Livingstone, London, 2nd edition, 2005.
  17. 17. Optimizing gate size & positionKruskal 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
  18. 18. Doppler equation∆ F Doppler shift frequency (kHz)F0 Ultrasound transmission frequency (MHz)V Blood cell velocity (cm/sec)Cos Ө Cos of angle between US & flow directionC Speed of sound in soft tissue (1 540 m/sec)∆ F = 2 F0 V Cos Ө / C
  19. 19. Percentage error in velocity measurements& angle of insonationIn order to minimize this error,angles of insonation > 60% should not be used
  20. 20. Optimizing Doppler angleLarger 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 resultsThrush A, Hartshorne T. Peripheral vascular ultrasound: How, why and when.Elsevier Churchill Livingstone, London, 2nd edition, 2005.
  21. 21. Doppler angle measurementAngle: 60PSV: 110 cm/secEDV: 41 cm/secAngle: 44PSV: 74 cm/secEDV: 27 cm/secThrush A et al. Peripheral vascular ultrasound. Elsevier Churchill Livingstone, London, 2005.
  22. 22. Changing position of the transducerIntercostalTransabdominal SubcostalKruskal JB et al.RadioGraphics 2004 ; 24 : 657 – 675.
  23. 23. Adjusting spectral velocity scaleSpectral scale: 200 cm/sec Spectral scale: 50 cm/secKruskal JB et al.RadioGraphics 2004 ; 24 : 657 – 675.Color Doppler image, color bar, & color scale unchangedSpectral component is active
  24. 24. Adjusting spectral Doppler gainGain setting 0% Gain setting 38%Gain setting 77% Gain setting 100%Kruskal JB et al.RadioGraphics 2004 ; 24 : 657 – 675.
  25. 25. Spectral wall filterWall filter 75 HzWall thump removedWall filter 550 HzFilter frequency too highAltered waveformWall filter 50 HzWall thumpThrush A, Hartshorne T. Peripheral vascular ultrasound: How, why and when.Elsevier Churchill Livingstone, London, 2nd edition, 2005.
  26. 26. Spectral aliasingCCADropping baseline Increasing scalePeaks cross baselineRubens DJ et al. Doppler artifacts & pitfalls.Ultrasound Clin 2006 ; 1 : 79 – 109.
  27. 27.  Color-specific parameters
  28. 28. Color mapBaselineWall filter
  29. 29. Changing color baselineKruskal JB et al.RadioGraphics 2004 ; 24 : 657 – 675.When color baseline changed → color velocity range changedRange of depicted velocities remains constant
  30. 30. Examples of different color mapsThrush A, Hartshorne T. Peripheral vascular ultrasound: How, why and when.Elsevier Churchill Livingstone, London, 2nd edition, 2005.Velocity range(cm/sec)Inversion ofcolor mapColor writepriorityBaselinewall filter
  31. 31. Inversion of color flowKruskal JB et al.RadioGraphics 2004 ; 24 : 657 – 675.Reversal of this inversionAppropriate directional flow notedPortal venous flow appears blueFalsely suggests flow reversal
  32. 32. Inversion of spectral flowKruskal JB et al.RadioGraphics 2004 ; 24 : 657 – 675.
  33. 33. Color box size / OverlayKruskal JB et al.RadioGraphics 2004 ; 24 : 657 – 675.Oversized color box↑ frame rate & ↓ resolutionReduced color box size↓ frame rate & ↑ resolutionColor box should be as small & superficial as possible
  34. 34. Doppler angle effectsThrush A, Hartshorne T. Peripheral vascular ultrasound: How, why and when.Elsevier Churchill Livingstone, London, 2nd edition, 2005.
  35. 35. Color box steeringChanging angle of insonationLarge angleUnusable imageSmall angleGood imageModerate angleFlow is not optimalSteered either left or right by a maximum of 20 – 25Sensitivity of transducer decreases as beam is steeredThrush A et al. Peripheral vascular ultrasound. Elsevier Churchill Livingstone, 2nd edition, 2005.
  36. 36. Color box steered in more than one direction todemonstrate flow in the whole vesselColor box steeringThrush A et al. Peripheral vascular ultrasound. Elsevier Churchill Livingstone, 2nd edition, 2005.
  37. 37. Adjusting color velocity scaleKruskal JB et al.RadioGraphics 2004 ; 24 : 657 – 675.Color velocity scale 2 cm/secColor aliasing in PV & its branchesHigh color velocity scale (69 cm/sec)Apparent absence of flow in PVColor velocity scale 30 cm/secNormal flow in a patent PV
  38. 38. Color Doppler aliasingVelocity scale range 12 cm/sec Velocity scale range 23 cm/secRubens DJ et al. Doppler artifacts & pitfalls.Ultrasound Clin 2006 ; 1 : 79 – 109.
  39. 39. Portal vein pseudo-clotVelocity scale: 20 cm/s Velocity scale: 7 cm/s
  40. 40. Adjusting color gainKruskal JB et al.RadioGraphics 2004 ; 24 : 657 – 675.Color gain should be set as high as possiblewithout displaying random color specklesColor gain 44% Color gain 65% Color gain 100%
  41. 41. Adjusting color gainFlow „bleeding out‟ of the vesselColor gain set too highThrush A, Hartshorne T. Peripheral vascular ultrasound: How, why and when.Elsevier Churchill Livingstone, London, 2nd edition, 2005.
  42. 42. Adjusting color wall filterFilter setting displayed on color scale (horizontal arrow)Filter too highRemoving low flowFilter setting reducedDisplay low flowThrush A, Hartshorne T. Peripheral vascular ultrasound: How, why and when.Elsevier Churchill Livingstone, London, 2nd edition, 2005.
  43. 43. Pseudo-thrombosis of main PVAdjusting velocity & angle of insonationVelocity: 24 cm/secWall filter: mediumAngle 90Velocity: 7 cm/secWall filter: mediumAngle < 90Radiol Clin N Am 2006 ; 44 : 805 – 835.
  44. 44. Doppler panel on console of manycontemporary US imagersEach parameter can be adjusted to optimize spectral orcolor Doppler components of the examinationKruskal JB et al.RadioGraphics 2004 ; 24 : 657 – 675.
  45. 45. 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 selectedpreset choices includes:
  46. 46. 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 motionRubens DJ et al. Doppler artifacts & pitfalls.Ultrasound Clin 2006 ; 1 : 79 – 109.
  47. 47.  Power Doppler imaging
  48. 48. Advantages of power mode Doppler• No aliasing• Angle independent• Increased sensitivity to detect low-velocity flowDistinguish pre-occlusive from occlusive lesionsSuperior depiction of plaque surface morphology• Useful in imaging tortuous vessels• Increases accuracy of grading stenosis
  49. 49. Power Doppler imagingLarge plaque ulcerICANarrow flow channel in ICA“string sign” or “trickle flow ”
  50. 50. 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
  51. 51.  Normal flow in arteries & veins
  52. 52. Flow at a curvature & bifurcationMyers KA & Clough A. Making sense of vascular ultrasound. Arnold, London, 2004.Apex of parabola moves awayfrom concave wall at a curveApex of parabola moves awayfrom outer wall at bifurcation
  53. 53. Flow around curves in a vesselTortuous ICAThrush A, Hartshorne T. Peripheral vascular ultrasound: How, why and when.Elsevier Churchill Livingstone, London, 2nd edition, 2005.A BAPSV outside the bend 70 cm/secBPSV inside the bend 55 cm/sec
  54. 54. Normal flow reversal zone in ICAOpposite to origin of the ECAHigh velocities near flow dividerReversal on opposite side to flow dividerThrush A et al. Peripheral vascular ultrasound. Elsevier Churchill Livingstone, London, 2005.
  55. 55. High & low resistance arterial flowHigh-resistance flowSFALow-resistance flowICAMyers KA & Clough A. Making sense of vascular ultrasound. Arnold, London, 2004.
  56. 56. Arterial high resistance flowTypical normal Doppler spectraNormal anterior tibial arteryTriphasic flow
  57. 57. Pulsatility indexMost commonly used of all indicesS SystolicD Minimum diastolicM MeanPI S – D / M
  58. 58. Effect of exercise on flowDorsalis Pedis Artery at restTriphasic flowThrush A, Hartshorne T. Peripheral vascular ultrasound: How, why and when.Elsevier Churchill Livingstone, London, 2nd edition, 2005.DPA following exerciseMonophasic hyperemic flow
  59. 59. Arterial monophasic flow• HyperemicExerciseInfectionTemporary arterial occlusion by blood pressure cuff• Distal to severe stenosis or occlusionLow velocityLonger rise time*Tardus-Parvus wave* Rise time: time between beginning of systole & peak systole
  60. 60. Tardus-Parvus waveDistal to severe stenosis or occlusionThrush A, Hartshorne T. Peripheral vascular ultrasound: How, why and when.Elsevier Churchill Livingstone, London, 2nd edition, 2005.Tardus: Longer rise timeParvus: Low PSV
  61. 61. Arterial low resistance flowTypical normal Doppler spectraNormal internal carotid artery
  62. 62. Pourcelot’s resistance indexRI S – ED / SNormal 50 – 70 %Abnormal > 80 %
  63. 63. Accleration Time (AT)or Rise Time (RT)• Length of time in seconds fromonset of systole to peak systole• Normal value: ≤ 0.07 second
  64. 64. Acceleration indexAI =X (KHz)Probe frequency (MHz)Normal value: > 3.8 cm/s2
  65. 65. Aacleration time & PSVEarly systolic pickAJR - Dec 1995Biphasic with late systolic pickMonophasic with late systolic pick
  66. 66. AT & AI according to degree of stenosisModerate stenosis50 – 85%Normal Severe stenosis> 85 %
  67. 67. Measurement of volume flowVolume = Cross-sectional area Mean velocity 60(ml/min) (cm2) (cm/sec)Cross-sectional area (cm2): π d2 / 4d: diameter
  68. 68. Doppler equationConverting Doppler shift frequency to velocity∆ F Doppler shift frequency (kHz)F0 Ultrasound transmission frequency (MHz)V Blood cell velocity (cm/sec)Cos Ө Cos of angle between US & flow directionC Speed of sound in soft tissue (1 540 m/sec)∆ F = 2 F0 V Cos Ө / C
  69. 69. ∆ FF0V ?Cos ӨC∆ F = 2 F0 V Cos Ө / C50 cm/s1.6 kHz5 MHz601 540 m/secThrush A, Hartshorne T. Peripheral vascular ultrasound: How, why and when.Elsevier Churchill Livingstone, London, 2nd edition, 2005.Doppler equationConverting Doppler shift frequency to velocity
  70. 70. Blood flow & PSV changes relatedto severity of arterial stenosisMyers KA & Clough A. Making sense of vascular ultrasound. Arnold, London, 2004.
  71. 71. Flow through a stenosisThrush A, Hartshorne T. Peripheral vascular ultrasound: How, why and when.Elsevier Churchill Livingstone, London, 2nd edition, 2005.Increased velocity through stenosisFlow reversal beyond stenosisCCAIJVICA Color from red to turquoise Posterior wall – deep blue
  72. 72. Pic Systolic Velocity ratioRobbin ML et al. Ultrasound Clin 2006 ; 1 : 111 – 131.Proximal: 2 cm proximal to stenosisSame Doppler angle if possible
  73. 73. 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 reductionHigh amplitude & low frequency signalLow amplitude & high frequency signalFlow reversal – Poor definition of spectral border• May be only sign of stenosis: calcified plaque
  74. 74. Spectral broadeningImmediate post-stenotic zone
  75. 75. 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, & FMD31AVF: Arterio-Venous Fistula2AVM: Arterio-Venous Malformation3FMD: Fibro-Muscular Dysplasia
  76. 76. Color Doppler bruitExtensive soft tisuue color Doppler bruit surroundsthe carotid bifurcation with 90% ICA stenosis
  77. 77. Venous valveTwo cups of a valve clearly seenIt is uncommon to see venous valves with this clarity
  78. 78. Normal venous flow Spontaneity Spontaneous flow without augmentation Phasicity Flow changes with respiration Compression Transverse plane Augmentation Compression distal to site of examinationPatency below site of examination Valsalva Deep breath, strain while holding breathPatency of abdominal & pelvic veins
  79. 79. Normal venous flow Spontaneity Spontaneous flow without augmentation Phasicity Flow changes with respiration Compression Transverse plane Augmentation Compression distal to site of examinationPatency below site of examination Valsalva Deep breath, strain while holding breathPatency of abdominal & pelvic veins
  80. 80. PhasicityFlow changes with respirationSlow ApneaRapid
  81. 81. Normal venous flow Spontaneity Spontaneous flow without augmentation Phasicity Flow changes with respiration Compression Transverse plane Augmentation Compression distal to site of examinationPatency below site of examination Valsalva Deep breath, strain while holding breathPatency of abdominal & pelvic veins
  82. 82. Compressibility of veinsDo not press too hard since the normal vein collapsesvery easily making it difficult to find11
  83. 83. Incompressibility = ThrombusDo not compress vein more than necessary in recent thrombusFear of detaching thrombus to cause PEMyers KA & Clough A. Making sense of vascular ultrasound. Arnold, London, 2004.
  84. 84. External compression of the veinRelaxation CompressionA
  85. 85. Normal venous flow Spontaneity Spontaneous flow without augmentation Phasicity Flow changes with respiration Compression Transverse plane Augmentation Compression distal to site of examinationPatency below site of examination Valsalva Deep breath, strain while holding breathPatency of abdominal & pelvic veins
  86. 86. Augmented flow in popliteal veinAug Competent vein
  87. 87. Normal venous flow Spontaneity Spontaneous flow without augmentation Phasicity Flow changes with respiration Compression Transverse plane Augmentation Compression distal to site of examinationPatency below site of examination Valsalva Deep breath, strain while holding breathPatency of abdominal & pelvic veins
  88. 88. Valsalva’s maneuverValsalva’s maneuverA VNormal respirationA V
  89. 89. Valsalva maneuverStartValsalvaEndValsalvaCompetent vein
  90. 90. Indicate on the report whetherthe examination was excellent, good or poorEmphasize if a scan is suboptimalMyers KA & Clough A. Making sense of vascular ultrasound. Arnold, London, 2004.
  91. 91. ReferencesArnold – 2004 Elsevier – 2005 Elsevier Mosby – 2005
  92. 92. Thank You

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