A radiation detector includes slit collimator. A radiation detector receives radiation which has been received in each of the slits. The aspect ratio of the detector is approximately three, and each semiconductor radiation detector (106) has a transverse dimension (C y ) which is less than that of its respective slit (W y ). A reconstruction processor generates an image indicative of the radiation received by the detectors. The detector may be rotated about a fixed axis (109). Alternately, the detector may be translated in coordination with its rotation to provide a substantially square field of view.