Diffusion tensor imaging

Image:Illus dti.gif Diffusion tensor imaging (DTI) is a new magnetic resonance imaging(MRI)-based technique that allows us to visualize the location, the orientation, and the anisotropyof the brain's white mattertracts. The architecture of the axonsin parallel bundles and their myelinshield facilitate the diffusionof the water molecules along their main direction. This diffusion which is preferentially oriented in one direction is called "anisotropic diffusion". The imaging of this white matter property is an extension of diffusion MRI. If we apply diffusion gradients (i.e. magnetic fieldvariations in the MRI magnet) in at least 6 directions, it is possible to calculate, for each pixel, a tensor(i.e. a 3*3 matrix) that describes this diffusion anisotropy. The fiber direction is indicated by the tensor?s main eigenvector. This vector can be color-coded, yielding a cartography of the tracts? position and direction (red for left-right, blue for superior-inferior, and green for anterior-posterior). The brightness is weighted by the tracts? anisotropy.

Fiber tracking algorithms can be used to track a fiber along its whole lenght (e.g. the corticospinal tract, through which the motor information transit from the motor cortexto the spinal cordand the peripheral nerves).

The clinical applications of DTI are the tract-specific localization of white matter lesions, the localization of tumorsin relation to the white matter tracts (infiltration, deflection), the localization of the main white matter tracts for neurosurgical planning, and the assessment of the white matter maturation in children.

External links

• White Matter Atlas
• Pediatric DTI database
• Thesis on DTI
• Information, with image galleryfr:Imagerie du tenseur de diffusion

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It uses material from the http://en.wikipedia.org/wiki/Diffusion+tensor+imaging Wikipedia article Diffusion tensor imaging.