principles of doppler ultrasound

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  • Principles of Doppler ultrasoundSamir 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 veinsPrinciples of Doppler ultrasound
  • General principles of Doppler ultrasound
  • Christian Doppler (1803 1853)Famous for what is called now the Doppler effect1841 Professor of mathematics & physicsPrague polytechnic1842 Published his famous bookOn the colored light of the binary stars& some other stars of the heavens1850 Head of institute of experimental physicsVienna UniversityAustrian 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 frThrush A, Hartshorne T. Peripheral vascular ultrasound: How, why and when.Elsevier Churchill Livingstone, London, 2nd edition, 2005.ftfr
  • Doppler equation F Doppler shift frequency (kHz)F0 Ultrasound transmission frequency (MHz)V Blood cell velocity (cm/sec)Cos Cos of angle between US & flow directionC Speed of sound in soft tissue (1 540 m/sec) F = 2 F0 V Cos / C
  • 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
  • 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 DopplerAngle correctioncursorBeam pathSample volumeBaselineEDVThrush A, Hartshorne T. Peripheral vascular ultrasound: How, why and when.Elsevier Churchill Livingstone, London, 2nd edition, 2005.PSV
  • Doppler shift frequency & angle of insonationThrush A, Hartshorne T. Peripheral vascular ultrasound: How, why and when.Elsevier Churchill Livingstone, London, 2nd edition, 2005.
  • Use of spectral baselineNormal baselineInverted baselineDropping baseline
  • 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.
  • 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
  • Doppler equation F Doppler shift frequency (kHz)F0 Ultrasound transmission frequency (MHz)V Blood cell velocity (cm/sec)Cos Cos of angle between US & flow directionC Speed of sound in soft tissue (1 540 m/sec) F = 2 F0 V Cos / C
  • Percentage error in velocity measurements& angle of insonationIn order to minimize this error,angles of insonation > 60% should not be used
  • 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.
  • 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.
  • Changing position of the transducerIntercostalTransabdominal SubcostalKruskal JB et al.RadioGraphics 2004 ; 24 : 657 675.
  • 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
  • Adjusting spectral Doppler gainGain setting 0% Gain setting 38%Gain setting 77% Gain setting 100%Kruskal JB et al.RadioGraphics 2004 ; 24 : 657 675.
  • 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.
  • Spectral aliasingCCADropping baseline Increasing scalePeaks cross baselineRubens DJ et al. Doppler artifacts & pitfalls.Ultrasound Clin 2006 ; 1 : 79 109.
  • Color-specific parameters
  • Color mapBaselineWall filter
  • Changing color baselineKruskal JB et al.RadioGraphics 2004 ; 24 : 657 675.When color baseline changed color velocity range changedRange of depicted velocities remains constant
  • 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
  • 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
  • Inversion of spectral flowKruskal JB et al.RadioGraphics 2004 ; 24 : 657 675.
  • 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
  • Doppler angle effectsThrush A, Hartshorne T. Peripheral vascular ultrasound: How, why and when.Elsevier Churchill Livingstone, London, 2nd edition, 2005.
  • 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.
  • 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.
  • 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
  • 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.
  • Portal vein pseudo-clotVelocity scale: 20 cm/s Velocity scale: 7 cm/s
  • 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%

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