[Diffusion-weighted imaging and diffusion tensor imaging in preoperative diagnostics].

The extent of anisotropy and the direction of diffusion of H protons characterize the tissue structure and qualitative and quantitative evaluation of the appropriate parameters provide inferences for the membrane permeability, axon thickness, integrity and connectivity. The technique of fiber tracking is implemented in the presurgical diagnostics for lesions in the brain to show the relationship of the lesion to the fiber system. The benefit of this technique for preoperative and intraoperative localization of the pyramidal tracts, the primary motor areas, the optic radiation and the speech regions could be confirmed. In focal gliomas the fibers are often displaced to the edge of the tumor; however, in diffusely growing tumors the fiber system is infiltrated by tumor cells. In high-grade gliomas destruction of the fibers often occurs. Limitations are always present in brain regions where several fiber systems cross in different directions, such as the centrum semiovale. Appropriate neuroanatomical knowledge must be present in order to be able to immediately recognize such possible deviant pathways of the fiber tracking.