Elena Renken in Nautilus:
The brain’s lifeline, its network of blood vessels, is like a tree, says Mathieu Pernot, deputy director of the Physics for Medicine Paris Lab. The trunk begins in the neck with the carotid arteries, a pair of broad channels that then split into branches that climb into the various lobes of the brain. These channels fork endlessly into a web of tiny vessels that form a kind of canopy. The narrowest of these vessels are only wide enough for a single red blood cell to pass through, and in one important sense these vessels are akin to the tree’s leaves.
“When you want to look at pathology, usually you don’t see the sickness in the tree, but in the leaves,” Pernot says. (You can identify Dutch Elm Disease when the tree’s leaves yellow and wilt.) Just like leaves, the tiniest blood vessels in the brain often register changes in neuron and synapse activity first, including illness, such as new growth in a cancerous brain tumor.1, 2 But only in the past decade or so have we developed the technology to detect these microscopic changes in blood flow: It’s called ultrafast ultrasound.