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 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. A support assembly supports the collimating assembly and includes a first support member and a second support member with the collimating assembly being disposed therebetween. An adjustment assembly includes a first adjuster operable to adjust a first distance between the collimating assembly and the first support member and a second adjuster operable to adjust a second distance between the collimating assembly and the second support member.