3D thread tracking for robotic assistance in tele-surgery

Remote tele-manipulation tasks can be both long and exhausting. The operative workload can however be reduced through contextual systems, in which routine or dexterous actions are performed automatically. In this paper, we investigate this idea in tele-surgery by proposing automatic scissors, namely the possibility for a surgeon to invoke a third robotic arm to come and automatically cut the thread that he/she is holding. In particular, we address the problem of tracking deformable 3-dimensional (3D) curvilinear objects from stereo images. We propose an approach based on discrete Markov random field (MRF) optimization to track, in 3D, a thread modeled by a non-uniform rational B-spline (NURBS). We evaluate its accuracy off-line on synthetic and real data and illustrate its use for an automatic scissors command within an assistance system based on the da Vinci tele-surgical robot.