Diffusion Tensor Imaging (DTI) Explained! | Neuroscience Methods 101

Diffusion Tensor Imaging, or DTI, is a brain scan that shows the connections within the brain. Here is how it works.

The white matter of the brain shows the axonal bundles, i.e. the connections between neurons. Making an image of these white matter bundles, tractrography, gives us an idea of which areas are interconnected.

For this we use diffusion weighted imaging, or diffusion weighted MRI. Abbreviated as DWI or DW-MRI, it looks at the diffusion of hydrogen protons. Since hydrogen protons do not stand still but more aroud, making smart use of different magnetic gradients in the MRI can help to see in which areas hydrogen is diffusion or not. A DWI can reveal where diffusion is restricted, which can give an indication of neurological problems, such as stroke.

After we have a diffusion weighted image, we can go further by calculating the fraction anisotropy. This value shows if diffusion is stronger in one direction than in the other directions. In the brain this is mainly the case in white matter axons. By calculating these tensors we get an image the represents where white matter bundles are going.

References/resources:
Soares, J. M., Marques, P., Alves, V. & Sousa, N. A hitchhiker’s guide to diffusion tensor imaging. Front. Neurosci. 7, (2013). https://doi.org/10.3389/fnins.2013.00031

Tsolaki, E., Downes, A., Speier, W., Elias, W. J. & Pouratian, N. The potential value of probabilistic tractography-based for MR-guided focused ultrasound thalamotomy for essential tremor. NeuroImage Clin. 17, 1019–1027 (2018). https://doi.org/10.1016/j.nicl.2017.1...

Caiazzo, G., Trojsi, F., Cirillo, M., Tedeschi, G. & Esposito, F. Q-ball imaging models: comparison between high and low angular resolution diffusion-weighted MRI protocols for investigation of brain white matter integrity. Neuroradiology 58, 209–215 (2016). https://doi.org/10.1007/s00234-015-16...

Tian, Q. et al. Diffusion MRI tractography for improved transcranial MRI-guided focused ultrasound thalamotomy targeting for essential tremor. NeuroImage Clin. 19, 572–580 (2018). https://doi.org/10.1016/j.nicl.2018.0...

Kamada, K. et al. Functional Monitoring for Visual Pathway Using Real-time Visual Evoked Potentials and Optic-radiation Tractography: Oper. Neurosurg. 57, 121–127 (2005). https://doi.org/10.1227/01.neu.000016...

Kamada, K. et al. Visualization of the frontotemporal language fibers by tractography combined with functional magnetic resonance imaging and magnetoencephalography. J. Neurosurg. 106, 90–98 (2007). https://doi.org/10.3171/jns.2007.106....

Martin, A. R. et al. Translating state-of-the-art spinal cord MRI techniques to clinical use: A systematic review of clinical studies utilizing DTI, MT, MWF, MRS, and fMRI. NeuroImage Clin. 10, 192–238 (2016). https://doi.org/10.1016/j.nicl.2015.1...

Narrated by: Miles Wischnewski

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