Markerless Motion Tracking of Awake Animals in Positron Emission Tomography

Abstract

Noninvasive functional imaging of awake, unrestrained small animals using motion-compensation removes the need for anesthetics and enables an animal's behavioral response to stimuli or administered drugs to be studied concurrently with imaging. While the feasibility of motion-compensated radiotracer imaging of awake rodents using marker-based optical motion tracking has been shown, markerless motion tracking would avoid the risk of marker detachment, streamline the experimental workflow, and potentially provide more accurate pose estimates over a greater range of motion. We have developed a stereoscopic tracking system which relies on native features on the head to estimate motion. Features are detected and matched across multiple camera views to accumulate a database of head landmarks and pose is estimated based on 3D-2D registration of the landmarks to features in each image. Pose estimates of a taxidermal rat head phantom undergoing realistic rat head motion via robot control had a root mean square error of 0.15 and 1.8 mm using markerless and marker-based motion tracking, respectively. Markerless motion tracking also led to an appreciable reduction in motion artifacts in motion-compensated positron emission tomography imaging of a live, unanesthetized rat. The results suggest that further improvements in live subjects are likely if nonrigid features are discriminated robustly and excluded from the pose estimation process.

Comparison of consumer purchase intention between interactive and augmented reality shopping platforms through statistical analyses

“…Markerless tracking has the potential to improve both the accuracy of motion measurements and the range of detectable motion compared to Marker-based systems [20]. Both forms of AR require at least a basic camera, however markerless AR may greatly benefit from using a motion sensor, such as Kinect.…”

The effect of isoflurane on 18F-FDG uptake in the rat brain: a fully conscious dynamic PET study using motion compensation

“…Such motion compensation (MC) approaches avoid the need for anaesthesia and minimise the stress of the animal since it is unrestrained (although the animal is often confined to a small space during the scan). Motion tracking can either be marker-based [10, 11], where a small marker is attached to the head of the animal and tracked by external cameras, or markerless, where the facial features of the animal are identified and tracked [12]. These approaches have been shown to produce reconstructions of comparable quality to those of standard (anaesthetised) scans and thus show the greatest promise for investigating the effect of anaesthetics.…”

PET motion correction in context of integrated PET/MR: Current techniques, limitations, and future projections

“…For example, by attaching fiducials to the patient's chest, one‐dimensional chest movement can be measured . More advanced methods may leverage stereoscopic or ToF cameras, or nonphysical fiducials such as lasers . The use of optical methods as tracking signals require additional hardware and processing, but are still relatively simple to implement.…”