The scientific community has spent a decade exploring ultrasound as a means of breaking through the blood-brain barrier -- a layer of tightly-packed cells that surround the brain's blood vessels, making it difficult for doctors to deliver chemotherapy and other treatments to cancer patients. Thus far, though, most ultrasound-based techniques have relied upon complex and often costly equipment, including MRI machines and infusion pumps. But researchers at a startup called Perfusion Technology think they may have come up with a less invasive, more cost-effective alternative -- a new headset designed to deliver low-intensity ultrasound therapy to the