method A first image of a moving object is acquired by of a first imaging method, e.g by PET or SPECT imaging. The first image contains artifacts caused by object motion. From two further images acquired by a second imaging method, e.g. C.T. or M.R., and representing the object in respective states of motion, a motion model is formed. The information contents of either the first image or a combination image, formed from the first image and the two further images, and the motion model is enhanced.