Institute Physics for Medicine Paris, INSERM, ESPCI PSL Paris, CNRS, France
In the last twenty years, our team broke three fundamental barriers of ultrasound imaging - temporal resolution, sensitivity to motion and spatial resolution - with several orders of magnitude. These conceptual changes led to the advent of Ultrasound as a full-fledged neuroimaging modality for fundamental research in neuroscience and for clinical applications.
First, building on the concept of acoustic holography, ultrafast ultrasound imaging at thousands of frames per second made it possible to detect very subtle blood flow changes in small cerebral vessels during neuronal activity and introduced functional ultrasound imaging (fUSi) as a full-fledged neuroimaging modality. Its portability, cost and sensitivity make it particularly suited for neuroimaging during behavior, learning or cognitive studies in awake and freely moving animals, for functional brain connectomics in small animal models, for systems neuroscience. Clinical applications are already under investigation for clinical functional neuroimaging in human neonates, for per-operative functional imaging and future non-contact Brain Machine Interfaces.
Second, when combined with intravenously injected contrast agents, ultrafast imaging provides in vivo non-invasive imaging of whole brain hemodynamics up to microscopic scales. This Ultrasound Localization Microscopy (ULM) of the cerebrovascular system is achieved by localizing and tracking the exact position of millions of 1-3 µm diameter microbubbles deep into the brain.
Finally, by tracking the dynamics of these microbubbles during neuronal activity, it is possible for the first time to perform whole brain functional neuroimaging in rodents at the microscopic scale. With the growing evidence of early vascular or neurovascular dysfunction in neurodevelopmental and neurodegenerative diseases, such functional Ultrasound Localization Microscopy could improve the fundamental understanding, early screening and monitoring of the alterations in the developing and aging brain.