1. An imaging system comprising: at least one radiation detector disposed adjacent a subject to detect and measure at least one of emission and transmission radiation from a subject, the detector being movable around the subject to receive the radiation and generate measured projection data at a plurality of projection angles; a FOV means for determining a plurality of pixels which belongs to a field of view of the radiation detector at each projection angle; an image processor which iteratively reconstructs the radiation detected only in the field of view into image representations; and an image memory in which the image representations are iteratively reconstructed.