1. A system ( 100 ) for analyzing a sequence of datasets representing sequential images of an object, a dataset associating data values with positions, the images having an image region having a first border ( 210 ) and a second border ( 220 ) associated with the object, the system comprising a ray establishing means ( 130 ) for establishing for individual images an analysis ray ( 232 ; 234 ; 236 ) connecting the first and second border of the image region, the analysis rays being in a respective position representing a substantially same position with respect to the object, a gradient establishing means ( 140 ) for establishing, for individual analysis rays, a gradient value which is representative of a rate of change in the data values along the analysis ray from the first border to the second border.