1. A computer implemented method for three-dimensional contour tracking comprising the steps of: providing a database of a plurality of shape models and a plurality of appearance models, wherein shape models are curves and surfaces, appearance models are voxel intensity patterns, wherein said models include 2-dimensional shape models, 3-dimensional shape models and dynamical models that describe how a contour changes as it is propagated along on object in an image; providing a learning and classification algorithm trained using said shape models and appearance models; providing a digitized volumetric image comprising a plurality of intensities corresponding to an N×N×N domain of points in a 3-dimensional space; extracting one or more candidate data patches of an object from one of said images; calculating features from said data patches and applying said learning and classification algorithm to said features wherein said object is localized; searching for a shape and appearance counterpart of said candidate object among said stored shape models and appearance models that most closely matches said object to initialize a contour; and tracking said contour along said object in 3D incorporating said learning and classification algorithm, initializing said contour about an object in a low-resolution version of said image; tracking said contour along said object in said reduced resolution image to obtain a contour surface about said object; and re-tracking said contour surface along said object in said N×N×N image to correct errors in said contour surface in said reduced resolution image; wherein said steps of providing a database, providing a learning and classification algorithm, extracting data patches, calculating features, and tracking said contour are performed by a computer processor.