Visualising neuronal tracts

Nuada Medical Specialist Imaging

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Diffusion tensor tractography image showing the neuronal tracts in the brain of an adult male, viewed from above. These tracts correspond to bundles of axons, which are elongated projections that extend from neurons. They form the critical connective 'wiring' that transmits chemical and electrical signals between other neurons for sensory and motor functions.

What does this technique show?

This image has been created using a magnetic resonance imaging (MRI) scanner and an advanced method of data collection called diffusion tensor imaging, which is sensitive to the movement (diffusion) of water molecules in the tissue. The structure of the axon bundles that make up the tracts restricts this movement, so water is able to diffuse more freely along the length of the tract than across it.

By measuring the main direction of this water movement, this technique can provide directional information on the tracts. A colour palette is applied to represent this information and is superimposed onto the 3D structural brain image to create the image shown here. Thus the neuronal tracts can be mapped and examined in a living human brain.

Why was this image created?

MRI is a powerful diagnostic tool in medicine used routinely to provide anatomical information about the brain. However, MRI doesn't provide any functional information.

In cases when an MRI scan highlights a brain tumour or unidentified mass, the consultant requests a tractography. Combining structural MRI data with tractography data from diffusion tensor imaging is valuable in assisting diagnostics and neurosurgical planning. In the case of a brain tumour, the radiologist can use tractography to identify nearby neuronal tracts and assess whether they have been displaced or disrupted by the tumour.

This information is crucial when neurosurgeons need to remove as much of the tumour as possible with as little damage as possible to the function of the normal structures of the surrounding brain. It is also valuable academically, helping scientists to understand development and connectivity in the brain.