A positron emission tomography (PET) scanner, including a first detector portion arranged circumferentially around a patient pallet, the first detector portion having a predetermined axial extent and transaxially subtending more than 180 degrees, but less than 360 degrees with respect to a central axis of the scanner defined by the first detector portion and a second detector portion arranged separately from and opposing the first detector section, the second detector portion having a radius of curvature smaller than a radius of curvature of the first detector portion, wherein the second detector portion transaxially subtends less than 180 degrees with respect to the central axis of the scanner.
