The role of probabilistic tractocraphy in the surgical treatment of deep seated brain tumors

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Abstract in foreign language

Surgery provides the best survival rate for brain tumor patients but the risk of severe permanent neurological deficit is high in case of deep-seated tumors involving eloquent regions. Advanced MRI-based brain mapping techniques, such as probabilistic tractography are capable to identify important white matter pathways and subcortical nuclei that are not visible on conventional MRI sequences. In this Ph.D thesis we examined if probabilistic tractography is suitable to identify important brain structures in tumor patients and healthy subjects in two distinct subcortical eloquent regions: 1, the thalamus and 2, the brainstem. As far as we know, no previous study has examined this question before. In thalamic tumor patients we used connectivity-based thalamic segmentation by probabilistic tractography to identify the border of the normal thalamus and the tumor and differentiate the thalamic nuclei. The same technique was applied to the brainstem in healthy subjects to segment the four main ascending-descending pathways, namely the corticospinal/corticobulbar, the frontopontine and the sensory pathways and the reticular formation. The method was applied in two representative brainstem tumor patients to demonstrate the clinical applicability of the technique. Our results showed that connectivity-based segmentation by probabilistic tractography of the thalamus and the brainstem is suitable for clinical use and can potentially lower the surgical risk of tumor resection in these delicate eloquent subcortical brain regions.

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