Planning Nonlinear Access Paths for Temporal Bone Surgery.

Purpose: Interventions at the otobasis operate in the narrow region of thetemporal bone where several highly sensitive organs define obstacles withminimal clearance for surgical instruments. Nonlinear trajectories forpotential minimally-invasive interventions can provide larger distances to riskstructures and optimized orientations of surgical instruments, thus improvingclinical outcomes when compared to existing linear approaches. In this paper,we present fast and accurate planning methods for such nonlinear access paths.Methods: We define a specific motion planning problem in SE(3) = R3 x SO(3)with notable constraints in computation time and goal pose that reflect therequirements of temporal bone surgery.We then present k-RRT-Connect: twosuitable motion planners based on bidirectional Rapidly-exploring Random Trees(RRT) to solve this problem efficiently. Results: The benefits of k-RRT-Connectare demonstrated on real CT data of patients. Their general performance isshown on a large set of realistic synthetic anatomies. We also show that thesenew algorithms outperform state of the art methods based on circular arcs orBezier-Splines when applied to this specific problem. Conclusion: With thiswork we demonstrate that pre- and intra-operative planning of nonlinear accesspaths is possible for minimally-invasive surgeries at the otobasis.