1. A method for identifying a region of interest (ROI) in an object from a set of similar images of different instances of said object, said method comprising: inputting the set of similar images into a computer suitably programmed with an algorithm for calculating optimised weights; calculating an initial weight map of a feature of said images, applying said algorithm to the initial weight map to calculate optimised weights of said feature at locations in said map to minimise the sample size needed to distinguish a first group of said instances from a second group of said instances, thereby producing a weighted map, and identifying said ROI as consisting of a set of locations in said weighted map at which said feature has the highest optimised weights.