The aim of this study was to investigate whether diffusion tensor imaging (DTI) can be integrated into functional navigation for the intraoperative visualization of the pyramidal tract.

A single-shot spin-echo diffusion-weighted echo planar imaging sequence on a 1.5 T magnetic resonance (MR) scanner was used for DTI. One null image and six diffusion-weighted images (high B value 1 000 mm/s²) were obtained. Color-encoded fractional anisotropy maps of the principal eigenvector rendered as a boxoid within each voxel were used for segmentation of the pyramidal tract. The segmented images were rigidly registered with a T₁-weighted gradient echo 3D dataset for navigation in 16 patients with gliomas. In tumors adjacent to the motor cortex (n=6) data from functional MR imaging were co-registered.

The whole DTI processing lasted about 25-30 minutes in each case. In all cases DTI could be integrated into the navigational dataset resulting in an intraoperative visualization of the pyramidal tract by microscope-based navigation. Navigational accuracy measured as the target registration error was 1.2±0.46 mm. Registration of fractional anisotropy maps with the 3D navigational dataset was possible with an error of less than 2 mm. Co-registration with fMRI was consistent with DTI data. A neurological deterioration was observed only in one patient.

DTI can be reliably integrated into navigational datasets. Thus, microscope-based neuronavigation can be used for an intraoperative visualization of the course of the pyramidal tract. However, a possible shifting of the pyramidal tract has to be taken into account after major tumor parts are removed.