Duality-Based Optimization of Occlusion Avoidance for Active Optical Navigation System in Robotic Orthopedic Surgeries

In robotic orthopedic surgery, the optical tracking system (OTS) is typically placed in a fixed location. In surgery, the OTS’s line of sight is likely to be blocked. This will interrupt the navigation and affect surgical safety. To solve this occlusion problem, an RGB-D camera is used to detect possible occluders and a navigation robot is utilized to actively adjust the OTS viewpoint before occlusion occurs. To guarantee the applicability, the occluder is enveloped using a convex polytope, and a two-phase optimization method is proposed based on duality of convex optimization. The effectiveness of the proposed method is verified via simulations and experiments. Experimental results show thattheproposed method can avoid occlusion between the OTS and the occluder, and the targets are located near the center of the measurement volume. This active navigation guarantees the continuity of intraoperative navigation, and thus helps to improve the safety in robotic orthopedic surgery. Note to Practitioners—OTS is recognized as the gold standard for intraoperative navigation in orthopedic surgery. Fixed navigation is typically adopted in the operating room, where the surgeon manually adjusts the viewpoint of the OTS when necessary. However, fixed navigation has some limitations, i.e., measurement volume is limited, and the line of sight is easily blocked. To address this occlusion problem, the OTS and RGB-D camera are mounted on a 7-DOF navigation robot, and the OTS viewpoint can be actively adjusted before occlusion occurs. In this paper, complex occluders in the operating room are enveloped using convex polytopes. Occlusion avoidance is formulated as two-phase optimization based on duality. Simulations and experiments validate the effectiveness of the proposed method with Control Lyapunov Function constraints. The proposed method can maintain occlusion avoidance between the OTS and occluder. In future work, efforts will be directed towards the occlusion-free strategies of multiple occluders.