1. A method for segmenting a structure in an image, the method comprising: selecting one seed inside the structure, wherein the selecting is performed by a user; using a processor to derive a directionally dependent statistical model corresponding to the image to identify an area relative to the structure in the image, wherein the step of deriving comprises: resampling data corresponding to the structure in spherical coordinates; deriving a piece wise approximation using a mean shift algorithm of the image intensity along a radial direction extending from the seed; determining candidate voxels along a radial direction from a location of the seed, wherein the candidate voxels represent the structure; and segmenting the structure using the candidate voxels.