[Role of tractography in stereotactic radiosurgery and brain stereotactic radiotherapy]

Hypofractionated stereotactic radiotherapy and stereotactic radiosurgery are major therapeutic weapons in the brain, whether for tumor, vascular or functional treatments. They tend increasingly to democratize and to become standard treatments. However, human brain anatomy is very complex and not limited to the currently described organs at risk. Diffusion tensor imaging (DTI) tractography is a simple tool that enables to identify reproducibly big white matter fiber tracts. Not only does tractography allow a redefinition of organs at risk in the brain, but it would also allow the identification of new targets, such as the ventral intermediate nucleus (Vim) within the thalamus for treatment of movement disorders. We present here a review of the role of tractography and the anatomy, function and currently described dose-effect relationships of white matter fiber tracts with a major functional impact: the pyramidal tract for motor ability, the optic radiation for vision and the arcuate fasciculus for language.