Cortical peeling: CSF/grey/white matter boundaries visualized by nesting isosurfaces

Abstract

One computational tool of particular interest in the analysis of MR images of the cerebral cortex has been the automatic extraction of surfaces. Recently, enhanced MR images have been produced whose quality presented the opportunity to extract several of these surfaces from the same volume. We present preliminary data using this approach to visualize the boundaries of the cortex from the dura to the white matter. A series of isosurfaces were extracted from a signal-enhanced T1 MRI. The lower MR-intensity isosurfaces featured cortical vessels and dura, in contrast to higher intensity isosurfaces, in which the deeper structure of the superficial gyri became apparent. Two surfaces were chosen, one representative of the outer cortical surface and the other of the inner grey/white boundary, and their separation was computed to construct a “cortical thickness map.” The use of nested isosurfaces with high quality MR images can differentially segment surface features and reveal the underlying structure of gyri and sulci, aiding anatomical delineation, and may ultimately result in the automatic extraction of cortical thickness maps.