Diffusion Tensor Imaging: A New Frontier

Alex Zurek:  Undergraduate Psychology Major at Marquette University

Diffusion Tensor
Diffusion tensor imaging (DTI) has risen to the forefront of neuropsychology in the past two decades. A modified type of magnetic resonance imaging, DTI produces images that depict the diffusion of water through white matter in the brain. White matter essentially consists of tracts that allow the brain to function as a coordinated unit. Efficient signaling is largely dependent on the unidirectional diffusion of water through white matter. DTI has been useful in examining such tracts, but there is still speculation as to what role those tracts play in the disease processes of disorders such as schizophrenia and Alzheimer’s disease. I spoke to Dr. Hoelzle, a Marquette Assistant Professor trained in clinical neuropsychology, to learn more about current issues regarding DTI.

What have we learned about white matter in the brain through the use of diffusion tensor imaging (DTI)?
I’ve heard some people explain [white matter] in really simple terms as roads, ways that the brain communicates, and we had a decent idea about that. DTI gives us an opportunity to…look at a diseased brain and say, “Yes, the connectivity is not what we thought it would be.” We knew about connectivity but DTI is really a sophisticated technology to take a snapshot of what is going on there. 

How has the use of DTI impacted physicians’ ability to identify neural and psychological disease?
It is exciting to think that DTI will maybe give us an earlier sign that something is going on. As a neuropsychologist we look at the behavioral outcome of something. We ask people to complete a task; it might be a memory task, it might be a problem-solving task, it might be a visuospatial task. The idea is that once the person is not successful at completing that task it is related to some damage; the brain is not working in the way we might anticipate. DTI might be more sensitive. It might pick up that something is not right well before it manifests itself in observable behavior. There is that unique opportunity to get in there early and maybe make a difference.

Have physicians been able to use what we have learned from DTI to devise treatments?
I do not know of any treatments. There is the opportunity that if we are able to identify things in a more efficient way, more accurate way, then that is obviously going to help us develop targeted treatments. 

Is there anything you find interesting about DTI that you would like to add?
A lot of my research is using neuropsychological measures and things you can administer to someone when they are in their hospital bed…; we don’t need the big technology. In situations where there was a motor vehicle accident and the person is complaining of cognitive complaints after the fact, people are finding the neuropsychological evidence more compelling. When there is imaging data and something does not look right, but it doesn’t seem like it is impacting the person behaviorally…it is hard to say “They deserve to be compensated.” When the behavioral measures do not match up with imaging then you have to struggle with what data is right. We see some convergent validity across methods, but the methodology develops quicker than our understanding of it. It might not be that one data is right and one data is wrong, we just do not understand how they go together.

The use of DTI to develop new treatments and earlier diagnoses of neurodegenerative and psychotic disorders may not be far off. Compelling research implicates loose diffusion in white matter as the frontal disconnection that has been proposed as the basis for schizophrenia. Additionally, DTI scans are alreadyproving useful to physicians at St. Jude Children’s Research Hospital who are now able to visualize the microstructure of tracts surrounding tumors, enabling physicians to individualize treatments more effectively. Dr. Hoelzle is right, “the methodology develops quicker than our understanding of it”, but as the understanding of DTI catches up to its methodology we are sure to continue seeing fascinating advancements in neuropsychology.

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