gms | German Medical Science

Objective: Diffusion Tensor Imaging (DTI) and fiber tractography became popular and widespreadly used methods to visualize major white matter tracts in the human brain in-vivo. In case of glioma surgery, precise and reliable information about spatial localization and course of fiber bundles is essential to minimize postoperative deficits while maximizing the extent of tumor resection. In case of these invasive tumors, displacing, infiltrating or destroying white matter tracts, the placement of adequate seed regions or seed volumes for routinely used fiber tractography methods is still challenging due to altered brain morphology. To optimize the seeding procedure within the tumor-affected hemisphere, a new approach using tractography within the healthy hemisphere is presented.

Method: Based on fiber tractography within the healthy hemisphere, new regions are defined along the tractography result describing the extended outlines of the fiber tract. These regions are then transformed, according to image registration of the pathological and healthy hemisphere onto the pathological side of the brain. Fiber tractography is then applied to the set of generated seed regions. Finally, the results are restricted to a subset of seed regions used as include regions along the estimated tract, distant to the tumor. The approach has been implemented in C++ within the MeVisLab platform on an Intel Core i7-2600K CPU, 3.4 GHz, 16 GB RAM. The approach has been applied to MR data sets of two patients, one patient with a right-hemispheric postcentral metastasis and one patient with a large left frontal glioma.

Results: In both cases, the corticospinal tract could be reconstructed via the presented semi-automated approach. In comparison to the reconstruction results via manually seeded fiber tractography within the tumor affected hemisphere, with seeds outlining the cerebral peduncle, and include regions outlining a strong extended proposed motor cortex area, the presented approach delivers more solid and larger fiber bundle reconstructions.

Conclusions: We presented a promising approach for fiber tractography in case of patients with tumors in close proximity to the motor cortex area, where the definition of regions of interest for fiber tractography is aggravated due to altered morphology.