An imaging system, including (1) a CT scanner configured to scan an object arranged on a patient pallet (2) a PET scanner, including a first detector portion, including first detector elements, arranged circumferentially around the patient pallet, the first detector portion having a predetermined axial extent and transaxially subtending less than 360 degrees with respect to a central axis of the scanner and a second detector portion, including second detector elements, arranged separately from and opposing the first detector portion, wherein the second detector elements are of a different type than the first detector elements, and the second detector portion is configured to be movable radially and circumferentially around the object and (3) an acquisition subsystem configured to acquire first event data from the first detector portion and to acquire second event data from the second detector portion.
