New application of diffusion tensor imaging in neurosurgery.

Diffusion tensor imaging is a MRI technique that enables the measurement of the diffusion of water in tissue in order to produce neural tract images. Advanced methods such as color coding and tractography (fiber tracking) have been used to investigate the directionality. The localization of tumors in relation to the white matter tracts (infiltration, deflection), has been one the most important initial applications. A non invasive technique for assessing tumor tissue characteristics, like tumor cell density, is required to assist preoperative surgical planning for malignant brain tumors and help better define the target for tumor biopsy, resulting in more accurate diagnosis and grading of malignant brain tumors. One possible source of this information is diffusion tensor imaging. Date studies have focused on its ability to delineate white matter fiber tracks by fiber tracking and to detect tumor infiltration around the tumor and normal white matter interface. Relationships between cell density and the two key values that diffusion tensor imaging provides, fractional anisotropy and mean diffusivity, still need to be investigated. Mean diffusivity has a good negative correlation and fractional anisotropy has a good positive correlation with tumor cell density within the tumor core. Similar correlation was observed between the Ki-67, on the one hand and fractional anisotropy and mean diffusivity, on the other hand. Thus, measurement of both fractional anisotropy and mean diffusivity within the tumor core has a potential to provide detailed information on tumor cell density within the tumor.