1. A method for segmenting intravascular images comprising the steps of: acquiring a series of digitized images acquired from inside a vessel, each said image comprising a plurality of intensities corresponding to a 2-dimensional grid of pixels; providing a precomputed set of shapes for modeling contours of vessel wall boundaries, wherein a contour can be expressed as a sum of a mean shape and a inner product of shape modes and shape weights; initializing a boundary contour for one of said set of images; initializing said shape weights by projecting a contour into said shape modes; updating said shape weights from differential equations of said shape weights; and computing a contour by summing said mean shape and said inner product of shape modes and updated shape weights.