1. A system for registering an image sequence, comprising: an input for obtaining the image sequence, the image sequence comprising a plurality of images arranged sequentially within an image range; a transformation processor for establishing transformations between adjacent pairs of consecutive images in the image sequence to obtain a plurality of transformations as transformation matrices; an alignment processor for, based on the plurality of transformations, aligning the image sequence to a reference image to obtain a registered image sequence; wherein the alignment processor arranged for establishing the reference image from the plurality of images based on a transformation metric, the transformation metric quantifying a degree of transformation required for aligning the image sequence the reference image, wherein the alignment processor is arranged for quantifying the degree of transformation in accordance with the transformation metric based on multiplication of the transformation matrices of the adjacent pairs of consecutive images.