gms | German Medical Science

Objective: Major white matter tracts can be visualized by diffusion tensor imaging (DTI). Especially in brain stem lesions the selected approach is crucial to minimize postoperative deficits. The aim of this study was to investigate how DTI data can be visualized adequately to help surgical planning in brain stem lesions.

Methods: A group of 11 patients with brain stem lesions (6 cavernomas, 2 lymphomas, 2 gliomas, 1 metastasis) was investigated. MR-imaging was performed with a 1.5T MR scanner; for DTI a single-shot, spin-echo diffusion weighted echo planar imaging sequence was measured. Diffusion tensors were calculated by using the DTI task card software (MGH Boston, USA) under syngo VA25. Several visualization tools were compared: color-encoded fractional anisotropy maps, glyph representations of the diffusion tensors, fiber tracking of major white matter tracts, and reconstruction of hulls wrapping fiber bundles.

Results: Glyph representation was superior to FA map visualization, however only fiber tract representation allowed to get an impression about the organisation of the major white matter tracts in the brain stem. A widening and displacement of the fiber tracts due to the different brain stem lesions was easily detectable in a simultaneous 3-D display of reconstructed fiber tracts and high resolution anatomy. This display allowed planning the approach into the brain stem prior to surgery.

Conclusions: 3-D visualization of major white matter tracts by fiber tracking with co-registered display of standard high-resolution MR image data was most suitable to plan an approach into the brain stem. Intraoperative mapping however will still be necessary since the resolution of the reconstructed fiber bundles is still too low.