1. A method of modeling a three dimensional target object represented by a plurality of cross-sectional images to provide a representative corresponding three dimensional model, comprising the steps of: selecting an initial model from a plurality of available initial models by identifying an initial model based on physical similarity to said target object; superimposing an initial model upon said target object; for each of said plurality of cross-sectional images, determining an intersection contour of said initial model and a cross-sectional image of said target object; refining said determined intersection contour to more closely delineate said target object; sub-sampling points representing said refined determined intersection contour to provide a sub-sampled contour dataset; and adjusting said initial model towards said sub-sampled contour to provide a representative three dimensional model of said target object.