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1. Doppler Instrumentation 2. Blood Flow Dynamics 3. Blood Vessel Diseases

Doppler Effect. Doppler Effect ? perceived change in frequency of emitted and received soundwave due to motion of the emitter, receiver or reflector. Doppler instruments. Doppler instruments send sample frequency into the tissue. Receiver later compares the reflected frequency with the sample

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1. Doppler Instrumentation 2. Blood Flow Dynamics 3. Blood Vessel Diseases

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    1. 1. Doppler Instrumentation 2. Blood Flow Dynamics 3. Blood Vessel Diseases Montgomery College DMS 2004

    2. Doppler Effect Doppler Effect – perceived change in frequency of emitted and received sound wave due to motion of the emitter, receiver or reflector

    3. Doppler instruments Doppler instruments send sample frequency into the tissue. Receiver later compares the reflected frequency with the sample frequency and calculates the difference – “Doppler Shift”

    4. Doppler Shift Fd = Freflected - Fsample = 2FVcosa / C Fd – Doppler Shifted Frequency F – Sample Frequency V – Velocity of moving reflector C – Propagation speed a - Doppler angle of insonation

    5. Doppler Angle Best: 0, 180, or 60 Good: 45 - 60 Acceptable: 30 – 60 Worst: 90

    6. Doppler Capabilities: Detects Flow (presence or absence) Direction Velocity Waveform characteristics: turbulent or laminar, steady or pulsatile, antegrade or retrograde, arterial or venous, etc.

    7. Some Doppler Instruments PD Pulsed Wave Doppler CF Color Flow Doppler PW Power Wave Doppler

    8. PD - Pulsed Wave Doppler Pulsed operated Capable of range resolution – allows to select exact sample position (depth) Superimposed on 2D image Waveform Spectral Analysis

    9. Pulsed Wave Doppler

    10. CF Color Flow Doppler Employs same principle as PD – pulsed waves Hundreds of sample gates positioned along many different scan lines Color – coded frequency information superimposed over a 2D image (different colors (hues) are assigned to different velocities) Color map appears as a vertical bar Gives information about presence of flow, its direction and velocity.

    11. Color Flow Doppler

    12. PD Power Doppler Energy mode Similarly to Color Flow Doppler, it detects Doppler Shifts and shows flow in color, but instead of assigning different color hues to different velocities, it assigns different color hues to different densities or volume (RBC amount). In that, Power Doppler similar to 2D imaging: the more RBC, the stronger the moving reflector – the brighter the color hue. PD does not show direction or velocity of flow, but presence of flow only. It considered to be more sensitive. Consequently, it used in occlusive or near occlusive cases when Color Doppler cannot detect any flow.

    13. Power Doppler

    14. Laminar flow Parabolic Fluid moves in concentric layers Mostly uniform direction and velocity (velocity increases as the distance from the wall increases) In straight and smooth vessels

    15. Laminar Flow

    16. Turbulent flow Widest range of velocities (even negative – in opposite direction) Eddy (circular) currents Produces spectral broadening and color variations Due to stenosis or extrinsic compression

    17. Turbulent Flow

    18. Low vs. High resistance waveform ICA, Vertebral, Renal, Celiac, Splenic, Hepatic arteries are characterized by low resistance flow ECA, Subclavian, Aorta, Iliac, Extremity arteries are characterized high resistance flow

    19. Low vs. High resistance waveform

    20. Physical course of the arterial disease

    21. VENOUS INSUFFICIENCY – INCOMPETENT VENOUS VALVES Bicuspid valves in veins keep the blood flowing in only one direction Incompetent venous valves allow blood to travel both directions creating venous hypertension, resulting in edema and varicosities. In addition, fluid, red cells, and fibrinogen may leak into the surrounding tissue. Breakdown of red blood cells and other substances can also prevent the tissue from getting proper oxygen and nutrients. (sometimes leading to ulceration)

    22. DVT (Deep Venous Thrombosis) Thrombi most frequently originate at the cusps of venous valves or in the soleal sinuses because of stagnation. Flow may become restricted leading to venous hypertension. The vein walls stretch, the venous valves are damaged, all of which may lead to venous insufficiency. The great clinical danger is that the entire thrombus or a part of it may break loose and travel into the pulmonary circulation and cause life-threatening pulmonary embolism

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