1. A method for presenting images of a region of a subject obtained in a chronological sequence, each image being composed of a plurality of picture elements and each picture element having a value allocated thereto representing an appearance of that picture element in the image, comprising the steps of: comparing respective values allocated to respective picture elements at identical locations in two of said images to identify a change of said value between said two of said images; entering said change in a change log for said picture element; allocating a marking to said picture element dependent on the entry in said change log; and superimposing said marking at the location of said picture element in a selected image of said region.