1. A method for segmenting a target structure of an image comprising: receiving, at a computer, input to denote a region of interest of said image; setting a first seed representing at least one pixel outside of a target structure within said region of interest and a second seed representing at least one pixel inside said target structure; solving a first partial differential equation associated with said first seed and a second partial differential equation associated with said second seed to determine whether an exterior distance function has a minimum distance from said first seed and to determine whether an interior distance function has a minimum distance from the second seed, said exterior distance function and said interior distance function each representative of a distance to a set of points with a local travel cost; and segmenting said target structure from said image using a competition criterion between said interior distance function and said exterior distance function to determine said target structure.