1. A method for classifying pulmonary structures in digitized images, comprising the steps of: providing approximate target structure locations of one or more target structures in a digitized 3-dimensional (3D) image; fitting an anisotropic Gaussian model about said approximate target locations to generate more precise 3D target models and center locations of said one or more target structures; warping each said 3D target models into a 3D sphere; constructing a bounding manifold about each said warped 3D sphere; and identifying clusters on said bounding manifolds wherein said one or more target structures are classified.