Pose measurement and tracking system for motion-correction of unrestrained small animal PET/SPECT imaging

An optical landmark-based pose measurement and tracking system is under development to provide in-scan animal position data for a new SPECT imaging system for unrestrained laboratory animals. The animal position and orientation data provides motion correction during image reconstruction. This paper describes new developments and progress using landmark markers placed on the animal along with strobed infrared lighting with improvements in accuracy for the extraction of head feature positions during motion. A stereo infrared imaging approach acquires images of the markers through a transparent enclosure, segments the markers, corrects for distortion and rejects unwanted reflections. Software estimates intrinsic as well as extrinsic camera calibration parameters and provides a full six degree-of-freedom (DOF) camera-to-camera calibration. A robust stereo point correspondence and 3D measurement calculation based on the fundamental matrix provides the pose at camera frame rates. Experimental testing has been conducted on calibrated fixtures with six DOF measurement capabilities as well as on live laboratory mice. Results show significantly improved accuracy and repeatability of the measurements. The live mouse results have demonstrated that reliable, accurate tracking measurements can be consistently achieved for the full SPECT image acquisition.