Researchers from the USC Neurorestoration Center and the California Institute of Technology (Caltech) have built a simple, noninvasive device for measuring blood flow in the brain, by adapting a technique currently used in animal studies known as speckle contrast optical spectroscopy (SCOS). It works by capturing images of scattered laser light with an affordable, high-resolution camera— tiny blood cells pass through a laser beam, and the way the light scatters allows researchers to measure blood flow and volume. The device has already been tested with humans in small proof of concept studies demonstrating the tool’s utility for assessing stroke risk and detecting brain injury. In the current study, Liu and his team sought to confirm that SCOS is truly measuring blood flow in the brain, rather than in the scalp, which also contains many blood vessels. Liu’s team took an innovative approach: By temporarily blocking blood flow to the scalp, they confirmed that SCOS readings were indeed measuring signals from blood vessels in the brain. Readings from 20 participants showed that positioning the detector at least 2.3 centimeters away from the laser source provided the clearest measurement of brain blood flow. Beyond advancing research, the study helps confirm the clinical potential of SCOS for detecting and responding to stroke, brain injury and dementia.