IEEE Trans Med Imaging. 2014 Nov;33(11):2180-90. doi: 10.1109/TMI.2014.2332821. Epub 2014 Jun 26.
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.
使用运动补偿对清醒、不受约束的小动物进行无创功能成像，无需使用麻醉剂，并且可以同时进行动物对刺激或给予药物的行为反应的成像研究。虽然已经证明了使用基于标记的光学运动跟踪对清醒啮齿动物进行运动补偿示踪剂成像的可行性，但无标记运动跟踪将避免标记物脱落的风险，简化实验工作流程，并有可能在更大的运动范围内提供更准确的姿势估计。我们开发了一种立体跟踪系统，该系统依赖于头部的固有特征来估计运动。在多个摄像机视图中检测和匹配特征，以积累头部地标数据库，并根据地标到每个图像中特征的 3D-2D 配准来估计姿势。通过机器人控制对真实大鼠头部运动进行的标本大鼠头部幻影的姿势估计，使用无标记和基于标记的运动跟踪的均方根误差分别为 0.15 和 1.8 毫米。无标记运动跟踪还导致在对活体、未麻醉大鼠进行运动补偿正电子发射断层扫描成像时，运动伪影明显减少。如果能够稳健地区分非刚性特征并将其从姿势估计过程中排除，则在活体研究中可能会有进一步的改进。
