Localization of Language Areas in Brain Tumor Patients by Functional Geometry Alignment

The substantial reorganization of functional systems and hemodynamic changes caused by brain tumors make fMRI detection and characterization of functional brain regions in tumor patients a particularly difficult task. Our goal is to identify functional areas among different individuals and to localize potentially displaced active regions in patients. Localizing corresponding functional regions in patients with brain lesions is necessary for the pre-surgical localization of functional regions critical for language and other functions. In addition such findings may help to elucidate the mechanisms that control reorganization processes secondary to mass lesions in the brain. Anatomical data is only of limited value for this purpose. Rather than rely on spatial geometry, we propose to perform registration of functional regions between individuals in an alternative space whose geometry is governed by the functional interaction patterns in the brain. We first embed the brain into a functional map that reflects connectivity patterns during a task sequence. The resulting functional maps are then registered, and the obtained correspondences are propagated to the two brains. Initial experiments with the language system indicate that the proposed method yields improved correspondences across subjects. Our algorithm localizes language areas in tumor patients, even if the areas are not detected by standard approaches such as univariate regression.