Enhanced sensitivity of flow detection in small vessels with slow flow by coherent-flow power Doppler

Abstract

Power Doppler imaging is a commonly used method for the detection of flow. However, the sensitivity of power Doppler in small vessel detection is limited in clinical ultraound scanners by a combination of factors, including the small-diameter of vessels, slow flow through the vessels, the size of the Doppler ensemble, the presence of motion, the presence of noise, and the type of filter used. We have developed an alternative power Doppler imaging technique that enhances flow detection of small vessels and slow flow. This technique utilizes the same principles as power Doppler, but uses the coherence of backscattered blood signal rather than the backscattered signal power. We show that this technique, called coherent flow power Doppler (CFPD), is less sensitive to clutter-based signals and thermal noise and improves signal-to-noise ratio of the flow signal. We show through simulations, phantoms, and in vivo experimentation in human liver that this additional signal-to-noise ratio (7.5-12.5 dB) can be utilized to detect slower flow, improved frame rate (smaller Doppler ensemble), or improve the Doppler image profile. In addition, the technique demonstrates better signal-to-noise ratio for small-sized vessels (less than 2 mm).