Visualization of human cerebral cortex by flattening algorithms

Visualization of human brain function based on cortical activity is an interesting research work. Since most of the cerebral cortical surface areas are buried inside folds, the complex topology of cortical surface makes the visualization extremely difficult. In this paper, we present a new visualization system involving reconstructing 3-D cortical surfaces, rendering and flattening the resulting surface. Besides developing the conventional polygon-based flattening algorithm, we also propose a new voxel-based flattening method that flattens the cortical surface directly from the 3-D voxel data. For a polygon-based method, the cerebral cortical surfaces have to be firstly transferred to 3-D polygons and then mapped onto a minimally distorted 2-D plane, which is achieved by an optimization procedure. However, the proposed new method converts the 3-D cortical voxel data directly to a 2-D map. The flattened map is then obtained from warping this 2-D map to the position of minimum distortions. We demonstrate the utility of two approaches by the entirely and partially flattened cerebral cortex map in MRI images. These approaches will facilitate more refined analysis in the function of cerebral cortex.