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 entire brain over the course of extended treatment periods. This approach differs markedly from most other methods, which typically target smaller areas of the brain with high-intensity ultrasound doses. As with most other potential breakthroughs, however, Perfusion's technique still needs to undergo some major testing. The company has already conducted several tests on animals, but the last time a similar method was tried on humans, many subjects ended up suffering from excessive bleeding. And that doesn't sound good at all.