Are neurons dying? What is the brain tissue doing? How is the blood flow in the brain? Learn what specialized imaging techniques can tell us.
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Magnetic resonance spectroscopy is a very old technique.It's actually the first
type of technique that was used in MR imaging. It's not in itself an imaging technique,
so you don't get a picture. You're not seeing an image of the brain.
Instead what you get is a measure of biochemistry of the tissue that's
in the brain. So we can look at whether neurons are dying or
whether axons have been damaged, whether there is inflammation.
It's not reimbursable, so it's rarely used in clinical practice. It's virtually all
being used in research, but it's still one of these techniques that really gets at
what's happening to the tissue without us having to do a biopsy.
Now biopsies are necessary in most points of time, and MR spectroscopy
is only useful in certain areas of the brain, but it's one of the more exciting.
But beyond magnetic resonance imaging, there are new techniques in
what we consider the imaging world including optical coherence tomography.
So this is a relatively new technique that allows us to look at blood flow both--
you know--relatively close to the edge of the brain and looks at both blood that's
been oxygenated and also deoxygenated blood. So, as neurons fire, they take up blood,
they use the oxygen, and so you get this rush of both oxygenated and deoxygenated
blood. The advantage of this is we get a really fast time course of looking at
how the brain functions. The downside is it only goes about 2 inches into the cortex.
So it limits what we can do.
Functional magnetic resonance imaging is another technique that's being
widely used in research, especially in--well, in brain injury among pretty much every other
disease you can think of. Functional imaging uses the same MRI systems that our
standard structural clinical imaging is using--or are using--and looks at the time course
of blood flow to certain areas of the brain. So for example, if you open and close
your right hand, within about 5 seconds you see an increase in blood flow
to areas in the left motor cortex. We can measure this because it actually changes
the amount of iron saturation in the brain, so we can localize this. Right now, for
clinical purposes it's being used predominantly for presurgical planning, but there
have been widespread differences shown between TBI and controls. At this point,
it's really used to differentiate between groups of patients, so it's not as useful
on the single patient level, but it's one of the applications that's really being pushed
forward to look at function.
Produced by Victoria Tilney McDonough and Brian King, BrainLine.
Deborah Little, PhD is an associate professor of Neurology & Rehabilitation, Anatomy & Cell Biology, Ophthalmology & Visual Sciences, and Psychology at the University of Illinois. The focus of the work in her laboratory is to identify clinically-relevant MRI markers of injury in persons with a history of traumatic brain injury with a focus on the use of diffusion tensor imaging.
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