A computer-aided design system for revision of segmentation errors.

Automatic image segmentation methods often involve errors, requiring the assistance of the user to correct them. In this paper, a computer-aided design system is introduced for correcting such errors. The proposed system approximates each 3-D region by a parametric surface. Region voxels are first parametrized spherically using a coarse-to-fine subdivision method. By using the voxel positions and their parameter coordinates, control points of a rational Gaussian surface are determined through a least-squares method to approximate the region. Finally, this surface is overlaid with the volumetric image and by locally pulling or pushing it with the mouse while viewing image information, the surface is revised as needed. Typically, a few minutes are sufficient to correct errors in a region.