Flow detection based on the spatial coherence of backscattered echoes

Power Doppler imaging is widely used in clinics for flow detection. However, its ability and sensitivity in slow flow detection is limited by thermal noise and clutter. In addition, its frame rate is limited due to the need for a large number of ensembles to obtain sufficient sensitivity in flow detection. Such a need may also result in flash artifacts during moderate tissue motion. We propose an alternative method of flow detection using the spatial coherence of backscatterred ultrasound echoes. The method produces similar or better signal quality of conventional power Doppler techniques, but enhances slow flow detection and frame rate. We demonstrate the feasibility of this method with both simulations and an in-vivo human thyroid study. The results are compared with conventional power Doppler slow-flow detection. It is shown that this method can detect approximately 30% slower flow than conventional power Doppler, or improves the frame rate by a factor of 3 without loss of image quality.