Brain Atlas Deformation in the Presence of Large Space-occupying Tumors

Brain atlases contain a wealth of information that could be used for radiation therapy or neurosurgical planning. So far, however, when large space occupying tumors and lesions drastically alter the shape of brain structures and substructures, atlas-based methods have been of limited use. In this work we present a new technique that permits warping a brain atlas onto image volumes in which large lesions are present. This technique involves several steps: a global registration to bring the two volumes into approximate correspondence, a local registration to warp the atlas onto the patient volume, the seeding of the warped atlas with a synthetic tumor, and the deformation of the seeded atlas. Global registration is performed using a mutual information criterion. The method we have used for atlas warping is derived from optical flow principles. Preliminary results obtained on real patient images are being presented. These results indicate that the method we propose can be used to automatically segment structures of interest in brains with gross deformation. Potential areas of application for this method include automatic labeling of critical structures for radiation therapy and presurgical planning.