Curvature Flow Based 3D Surface Evolution Model for Polyp Detection and Visualization in CT Colonography

Computerized Tomography (CT) colonography is an emerging noninvasive technique for screening and diagnosing colon cancers. Since colonic polyps grow outward from the colon wall, they are modeled as protrusion shapes. In this chapter, we propose a novel anisotropic 3D surface evolution model for detecting protrusion shape based colonic polyp on the curved surface. The important feature of the proposed model is that it can detect protrusions with both convex and concave shapes. Protrusion shapes are defined as the extension beyond the usual limits or above a plane surface. Based on Gaussian and mean curvature flows, the approach works by locally deforming the convex or concave surface until the second principal curvature goes to zero. The diffusion directions are changed to prevent convex surfaces from converting into concave shapes, and vice versa. The deformation field quantitatively measures the amount of protrudeness. We also designed a new color coding scheme for better visualization of the detected polyps. The proposed method has been evaluated by using synthetic phantoms and real colon datasets.