A procedure to average 3D anatomical structures

Creating a feature-preserving average of three dimensional anatomical surfa ces extracted from volume image data is a complex task. Unlike individual i mages, averages present right-left symmetry and smooth surfaces which give insight into typical proportions. Averaging multiple biological surface ima ges requires careful superimposition and sampling of homologous regions. Ou r approach to biological surface image averaging grows out of a wireframe s urface tessellation approach by Cutting et al. (1993). The surface delineat ing wires represent high curvature crestlines. By adding tile boundaries in flatter areas the 3D image surface is parametrized into anatomically label ed (homology mapped) grids. We extend the Cutting et al. wireframe approach by encoding the entire surface as a series of B-spline space curves. The c restline averaging algorithm developed by Cutting et al. may then be used f or the entire surface. Shape preserving averaging of multiple surfaces requ ires careful positioning of homologous surface regions such as these B-spli ne space curves. We test the precision of this new procedure and its abilit y to appropriately position groups of surfaces in order to produce a shape- preserving average. Our result provides an average that well represents the source images and may be useful clinically as a deformable model or for an imation. (C) 2000 Elsevier Science BN. All rights reserved.