1. A computer-implemented method of segmenting digitized images, the method performed by said computer comprising the steps of: providing a digitized image comprising a plurality of intensities corresponding to a domain of points on a 3-dimensional grid; defining a shape matrix for a selected point in said image from moments of the intensities in a window of points about said selected point; calculating eigenvalues of said shape matrix; determining an eccentricity of a structure underlying said point from said eigenvalues, and segmenting said image based on said eccentricity values, wherein the steps of defining a shape matrix, calculating eigenvalues of said shape matrix, and determining the eccentricity of the underlying structure are repeated for all points in said image.