What Exactly Is Diffusion Spectral Imaging?

Neuroscientist Van Wedeen talks about how in diffusion spectral imaging water is used as a tracer to figure out the directions and crossings that fibers in the brain take.

See more of Dr. Van Wedeen's videos here.

What is DSI? Yeah--this business of crossing fibers. And so we had no idea how many fibers might cross at a given location, whether there were 3, 5, 12. What numbers might be involved and what angles might be involved? The way diffusion imaging works is that it uses the motion of water in the tissue as a tracer. And the water is more rapid parallel to fibers than it is perpendicular. And so by measuring the differences, you can figure out the directions of the fibers. It's a strange business because it's reflecting a microscopic process, but it isn't honest microscopy. So you're seeing an average of phenomena that occur on a scale of 1 to 5 microns, 10 microns. But you're not actually taking a picture with a 10-micron resolution. And then, given the diffusion shapes, you draw the lines and connect the dots. This is probably my brain stem, and this is based on the idea of differential equations. You know, you just sort of--and what this leaves out is that secretly inside this matrix things are turning at 90-degree angles between these directions. And that's something that's just hit me in the last couple of months. That these turns are really there, and they're cellular in scale.
Posted on BrainLine March 12, 2013.

About the author: Van Wedeen. MD

Van Wedeen, MD is associate professor in Radiology at Harvard Medical School, assistant neuroscientist at Massachusetts General Hospital, and director of Connectomics at Martinos Center, Department of Radiology, Massachusetts General Hospital.

Van Wedeen

Produced by Brian King, Vicky Youcha, and Lara Collins, BrainLine.