Called functional ultrasound imaging (fUSi), this new type of scan is unprecedented in precision and depth. In it, researchers used functional ultrasound imaging (fUSi) to monitor brain activity in a study subject as the individual moved about an open space. For brain imaging, fUSi measures changes in blood flow as a proxy for brain activity, Soloukey explains. For instance, EEGs provide a “superficial measure” of brain activity, Soloukey says. That’s where functional ultrasound imaging came in.