8/20/18. The Doppler Effect. Objectives. What is the Doppler Effect. Doppler principles. Spectral Waveform. Image recognition. Vascular Ultrasound

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1 Vascular Ultrasound: Physics and Haemodynamics Objectives Doppler principles Spectral Waveform Key factors Haemodynamics: Stenosis Waveforms Image recognition Vascular Ultrasound: A flawed paradigm What is the Doppler Effect Vascular Ultrasound Ultrasound of blood vessels ) Arteries / Venous Don t exist in isolation Attached to systems Own pathology Change with pathology The Doppler Effect Advanced Ultrasound Should be learned early Carotid What is the Doppler Effect?: More Familiar The Stationary Ambulance 1

2 The Moving Ambulance Christian Doppler ( ) Ultrasound: Components B-mode Colour Spectral The Doppler Effect The Doppler Effect B-mode: The Basics Movement Change in sound wavelength/ frequency Relationship to Ultrasound? observed frequency of a wave depends on the relative speed of the source and the observer Back to the basics Radar/Sonar Ultrasound B-mode: The Basics Ultrasound B-mode: The Basics 2

3 Ultrasound B-mode: The Basics B-mode: The Basics Variation in Anatomical Reflectors Ultrasound (MHz) Frequency Time Image Doppler: Ultrasound Doppler: Ultrasound B-mode Same Frequency Doppler Change in frequency Visualise movement Represent the change in frequency Spectral Fast Fourier Analysis Colour Autocorrelation Sound Doppler: Ultrasound hat determines the change in frequency? Colour Duplex Ultrasound Change in frequency What determines the change in frequency? 3

4 What determines the change in frequency? Doppler: The Equation Change in frequency = 2 X Freq X Reflector Speed X Angle (Cos 0) Speed of Sound Using the Doppler equation: Explain Doppler: Terminology B-mode Doppler Colour Colour flow imaging Colour Doppler Amplitude Doppler Spectral Doppler Duplex Ultrasound Colour duplex ultrasound Doppler: Let s look at Colour Color Flow Imaging: Optimisation Autocorrelation Qualitative Directional Directs interrogation Optimize B-Mode image first Keep box small Width Optimise Spatial resolution Temporal resolution Contrast resolution Own range of settings- Name them Create a good Doppler angle Heel / toe probe or steer PRF / Scale Set color gain appropriately 4

5 Spectral Doppler Spectral Doppler Fast Fourier Trans. Own settings- Name them Mathematical tool Frequency information Æ Spectral waveform Spectral: The Waveform Spectral: Information Moment in time Range of V s Intensity PSV EDV Ratios Resistance Mono, Bi, Triphasic Calculation (S/D, RI, PI) Blood Flow Profile Where are these useful? Spectral: Information Spectral: PSV PSV EDV Ratios Resistance Mono, Bi, Triphasic Calculation (S/D, RI, PI) Blood Flow Profile Basic Haemodynamics Stenosis Increase in velocity How to understand Pipes, hoses, basic plumbing 5

6 Spectral: Stenosis: Mr Benoulli What is a critical stenosis? How is PSV explained Preservation of Energy x x (Fluid Energy)x = Pressure & Kinetic E. What is a critical stenosis? Critical Stenosis Loss of Pressure/ Energy Carotid (55-65% diameter) Iliac A (97% area) x x - y Reduction in volume/pressure Renal Artery: 82% area RA Diameter: 60-70% Excretion of renin? Spectral: EDV/ Ratios Spectral: EDV/ Ratios Severe stenosis Increase in EDV Why? Severe stenosis Increase in EDV Loss volume Less resistance Distal vasodilation take us to 6

7 s 7% Ar ter ioles 5% Main Branches 10% Terminal Branches 6% Spectral: Resistance Spectral: Resistance: Mr Poiseuille Cardiac Output Artery tortuosity compliance no. of branches size Distal Vascular Bed Pressure Difference Q= Flow/Volume n = Viscosity r = Radius of the Vessel Spectral: Resistance: Mr Poiseuille Spectral: Resistance contributions Pressure Difference Q= Flow/Volume n = Viscosity r = Radius of the Vessel If r =.0001m r4 = Aorta Large Arteries Main Branches Terminal Branches Arterioles Capillaries Venous Spectral: Resistance Waveforms Spectral: Resistance Waveforms Draw waveforms Monophasic Biphasic Triphasic Draw waveforms Monophasic Biphasic Triphasic Label high/ low resistance Label high/ low resistance 7

8 Spectral: The Carotid Spectral: The Carotid ICA CCA ECA Vertebral Subclavian ICA CCA ECA Vertebral Subclavian? Hepatic A Spectral: Normal Physiology Cavernosal A: Pre Post Injection Leg Arterial Mesenteric Uterine Penile Spectral: Pathology Blood Flow Profile Leg Arterial Umbilical A. Third trimester Laminar Flow 8

9 Blood Flow Profile Haemodynamic: Normal flow Plug Flow Laminar Helical Essential concept: Explains Inaccuracies Presume direction of flow Recommend deg The Literature: Carotid Stenosis Blood Flow Profile The Importance of Doppler Angle of Insonation on Differentiation between 50 69% and 70 99% Carotid Artery Stenosis Logason etal Eur J of Endo Surg stenoses (51 patients) re-evaluated >50% stenosis Angle: Initial scan Mean 46 - PSV I81cm/s Spectral Broadening Mild Moderate Severe (Flow reversal) Audible Angle: Re-scanned 60 - PSV 261cm/s Some Examples CCA PSV EDV Resistance Mono, Bi, Triphasic Blood Flow Profile Plug, Laminer, Spectral Broadening Signature Waveform Conclusion 9

10 Superficial Femoral A Some Examples... Ulnar Artery SFA Aorta-Which is which? How can we tell which direction? 10

11 SMA 36yo male, cadaver, day 1 Poor urine output Mild acute antibody rejection DTPA Mag 3, Day 5 Bx CCA (see next page as well) CCA (more info) CCA CCA No CTA Large infacrt No CTA Large infacrt 11

12 ICA Vertebral Carotid Bulb ICA Hepatic A Appendix 12

13 EIA Groin Anything else? Draw Pre- stenosis Stenosis Immediately post severe stenosis Very distal post severe stenosis 13