The invention relates to the processing of a series of images. A multi-dimensional data set is formed from the series of images, for example, by stacking the images in order of succession. A cut plane is taken through the stack, that is, in the direction of succession and a slice through the stack is taken along the cut plane. A region of interest is derived from the slice. The invention is particularly useful for cardiology where a stack of successive MR images of a moving heart is formed. The ventricles of the heart are accurately segmented while using the slice in the direction of the time axis.