Monitoring blood flow in the brain is crucial for diagnosing and treating neurological conditions such as stroke, traumatic brain injury (TBI), and vascular dementia. However, current imaging methods like MRI and CT scans are costly and not easily accessible. Now, scientists have developed a new, noninvasive device that uses laser light to measure cerebral blood flow quickly and affordably, paving the way for broader clinical use.

To develop the device, researchers from the USC Neurorestoration Center (Los Angeles, CA, USA) and the California Institute of Technology (Caltech, Pasadena, CA, USA) adapted a research technique known as speckle contrast optical spectroscopy (SCOS)—traditionally used in animal studies—for potential use in humans. The device captures laser light scattered by moving blood cells with a high-resolution camera, providing real-time insight into blood flow and volume within the brain.

In their latest research, the scientists aimed to confirm that SCOS truly measures blood flow within the brain rather than the scalp, a question that has long challenged light-based neuroimaging. To test this, the team temporarily blocked scalp blood flow while maintaining normal brain circulation. The resulting data from 20 participants demonstrated that when the detector was positioned at least 2.3 centimeters from the laser source, the readings accurately reflected cerebral rather than scalp blood flow.

The results, published in APL Bioengineering, mark the first experimental evidence in humans showing that laser speckle optical devices can penetrate scalp layers to capture brain-specific blood signals. The findings not only validate SCOS’s accuracy but also provide a technical framework for researchers developing other light-based brain monitoring tools.

Because the SCOS system is compact, low-cost, and noninvasive, it holds immense promise for clinical applications. It could eventually be used to assess stroke risk, detect traumatic brain injury, and monitor brain health in dementia patients. The technique is already being used by collaborating teams to aid in stroke and TBI diagnosis, and further refinements are underway to enhance image resolution and data precision.

“We look directly at humans in essentially the same way the tool will be applied, so there’s nothing lost in translation,” said Charles Liu, MD, PhD, professor of clinical neurological surgery at the Keck School of Medicine of USC and director of the USC Neurorestoration Center. “With the knowledge that we’re now measuring exactly what we intend to measure, we’re going to expand our testing of this technique with patients in clinical settings.”

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