A single photon emission computed tomography system includes a base for supporting a patient and a detector assembly adjacent the field of view. The detector assembly detects photon strikes from the field of view. A photon-blocking member is disposed between the field of view and the detector assembly and has an aperture slot that allows passage of photons aligned with the slot. A collimating assembly includes a plurality of collimating vanes formed of photon-attenuating material and is disposed between the field of view and the detector assembly.