超声彩色多普勒ColorDoppler__培训课件.ppt

Anatomy of a Color Flow Image The result is an image with colors representing the average velocities. General direction of ultrasound beam This area is red, so flow is away the beam, right to left This area is blue, so flow is generally towards from the beam, left to right RABT Dealing with the Doppler Problems What is going on here? Why is the blood flow multi-colored, rather than all red or all blue? Color Flow has Doppler’s Limitations Of the three pieces of information from a Doppler signal, CFM uses only the VELOCITY information. Velocity Intensity Turbulence And has the same limitations: Aliasing: Maximum velocity limited by PRF Dependent on angle of flow Frame Rates are a problem too! Since Color Flow requires lots of Doppler signals, the frame rates can be slow. Your only choices are: Do less color flow (make the color box smaller) Cheat L500: Parallel Processing L400: Automatic Control Technology Dealing with the Doppler Problems What is going on here? Where is the flow velocity the highest? A? B? C? A B C Dealing with the Doppler Problems The flow velocity is the same in the vessel, but the angle makes it look like the blood is accelerating from A to B to C. What is going on here? Where is the flow velocity the highest? A? B? C? A B C Dealing with the Doppler Problems What is going on here? Why is the blood flow multi-colored, rather than all red or all blue? Dealing with the Doppler Problems What is going on here? Why is the blood flow multi-colored, rather than all red or all blue? It’s a combination of changing angles and aliasing. Dealing with the Doppler Problems Remember this? What if we used Intensity instead of Velocity to map the flow information? Velocity Turbulence Intensity Dealing with the Doppler Problems Velocity asks “how fast is it going?” Velocity is subject to angle problems. Apparent velocity changes with angle. Velocity is subject to aliasing. Depends on PRF. Intensity asks “how many are going?”  Intensi