Multi-Angle Emission and Cross-Correlation Based Ultrafast Doppler and Functional Ultrasound Imaging

Detecting small blood flow signals presents a significant challenge in ultrasound Doppler imaging, emphasizing the necessity for improved imaging sensitivity and effective noise reduction strategies. Recent developments in ultrafast ultrasound Doppler flow imaging, based on multi-angle planewave coherent compounding, have overcome the framerate limitations of traditional focused ultrasound imaging, enabling high-sensitivity imaging of small blood flows. The evolution of planewave imaging modalities also demands new approaches for ultrasound noise reduction. Utilizing the strong coherence of blood flow signals from different tilted planewave emissions, we perform a noise suppression method that divides the planewave signals into two subgroups based on the sign of their tilting angles, and performs a cross-correlation operation after clutter filtering to produce noise-reduced power Doppler images of blood flow. Experimental evaluations involving rat cerebral blood flow and functional imaging reveal that the method can enhance the signal-to-noise ratio of blood flow images by approximately 15 dB. Furthermore, it significantly enhances the sensitivity of ultrafast ultrasound functional brain imaging.