Each year, nearly 800,000 people in the U.S. experience a stroke, and almost 90 percent of those are ischemic strokes in which a clot cuts off blood flow to part of the brain. To prevent further injury, blood flow to the brain must be restored as quickly as possible. In a new study, researchers show that non-invasive optical sensors can provide clinicians with real-time feedback on whether clot busting treatments are restoring blood flow. The technique, which monitors blood flow and oxygen levels in the brain, could also reveal early warnings signs of neurological complications after a stroke.