Patent ID: 7454043

Claim:
An image processing unit which comprises: an input for the signal of a current image of a body volume, the body volume being subject to a motion comprising several phases of motion; at least one input for a signal which represents the phase of motion of the body volume which belongs to the current image; a memory in which previous images of the body volume are stored together with the associated phases of motion; and a controller for: calculation of a similarity measure between the current image and a representative image, the similarity measure being associated with the phase of motion; calculation of the similarity measure between the representative image and the previous images or a sub-quantity thereof; and selection of those previous images whose similarity measure relative to the representative image lies in a predetermined range around the similarity measure of the current image relative to the representative image, the image processing unit being arranged to associate with the current image that previous image from among the previous images whose phase of motion is closest to the phase of motion of the current image.