Power Doppler imaging is a commonly used method for the detection of flow. The direction of flow is lost with power Doppler, but it has greater sensitivity to flow compared to velocity estimation techniques. Power Doppler imaging can be degraded if thermal noise is large or if slowly moving reverberation clutter passes through the wall filter. We have developed a power Doppler imaging technique, based on the same principles as power Doppler, but which uses the coherence of backscattered blood signal rather than the complex backscattered signal. This technique, called coherent flow power Doppler (CFPD), is less sensitive to clutter-based signals and thermal noise. We are developing enhanced flow detection methods based on CFPD through simulation, phantom, and in vivo experiments.