Functional Ultrasound Imaging of Cerebral Capillaries in Rodents and Humans
Monitoring capillary blood flow is of great clinical value since microcirculation is crucial for proper delivery of oxygen and nutrients to the biological tissue, particularly in the brain. Functional ultrasound imaging is a novel method to measure hemodynamics in small vessels at a high resolution providing new insight into brain activity. Nevertheless, a drawback of this modality is the need for clutter filtering to suppress signals originating from slowly moving tissue that may hinder not only the detection of low blood flow velocity in micro vessels but also significantly underestimate the power spectrum of the Doppler signal. Here, we demonstrate how a spatiotemporal filtering approach based on the Singular Value Decomposition (SVD) can efficiently remove the clutter signal while preserving the blood flow signal even at low frequency. This strategy was applied to image brain capillaries in rodents and to visualize the cortical microvasculature in the human brain during neurosurgery.