1. An image registration system comprising: a memory storing digital data representing a first image and a second image; an image processing unit configured to register the second image onto a coordinate system of the first image to obtain a registered second image; and a user interface device adapted to display one of the first image or the registered second image, and a movable region having a periphery, the user interface being adapted to display the first image or the registered second image within the periphery and the other image outside the periphery; wherein, the image processing unit is adapted to determine a similarity in alignment of a feature of the registered second image with a corresponding feature of the first image only at the periphery of the movable region, and the user interface device is adapted to provide a visual indication to indicate the similarity of the alignment.