Development of a Compact Optical Tracking System with Motorized Variable Zoom and Rotation for Tracking Range Adjustment in Image-Guided Surgery

Interest in remote robot-assisted image-guided surgery is increasing to improve medical accessibility in areas where physical visits by medical staff are challenging. However, existing optical tracking systems (OTS) cannot accommodate intraoperative changes in tracking range because they use fixed magnification lenses and mounts. We develop a new OTS that includes a motorized variable zoom lens system and a two-degree of freedom (DOF) rotation module, along with control algorithms to adjust the tracking range for targets in remote image-guided surgery. The variable zoom lens system automatically switches among three preoperatively calibrated zoom lenses using a lead-screw-based linear guide and a photo interrupter sensor. Based on a remote center of motion (RCM) mechanism, a rotation module can adjust the OTS’s orientation while keeping its position fixed. In addition, we implemented a reinforcement learning-based control algorithm to ensure that the target always remains within the OTS's tracking range. The variable zoom lens system showed high iterative precision at the micrometer level, and the positional tracking error of target was less than 0.1 mm. The rotation module achieved a resolution of 0.1° in the yaw and pitch axes. We trained the control algorithm in a virtual simulator environment and deployed it in the actual system to keep the rigid body within the tracking range. The proposed system can adapt to intraoperative changes in tracking range. This will contribute to increased utilization of OTS in various surgical fields and enhance the safety of surgeries.