A method and system for generating synthetic images for use in a database is described. The database is used for delineation of features in real images, the method comprising the steps of: providing a delineated image acquired using a first scanner, defining a model related to the generation of synthetic images using a second scanner, processing the delineated image using the model to generate a synthetic image, mapping contours to the synthetic image to form a synthetic image-contour pair; repeating providing, defining and processing steps to generate a plurality of synthetic images and contour pairs for the database; using said database of synthetic images and contour pairs to optimise a contouring algorithm, where the optimised algorithm generates contours for the real images of the same type as the synthetic images; processing one or more further real images to contour and delineate features on the further real image using the algorithm.