Preoperative surgical planning for robot-assisted liver tumour ablation therapy based on collision-free reachableworkspaces

To destroy an entire tumour with the minimum damage to healthy tissue using robotic-assisted liver tumour coagulation therapy, the surgeon should manually determine the needle-insertion path and the entry point based on a reconstructed three-dimensional (3D) model of the liver and the operating environment. However, existing preoperative planning methods depend on the skill of the surgeon, which has implications for the surgeon's workload. Because of a lack of tactile feedback and limited 3D visualization space, this preoperative planning must be iterated many times until an optimal needle-insertion path can be obtained. Here we propose a preoperative planning method that determines the collision-free reachable workspace (CFRW) of the needle, from which the surgeon can select a feasible needle-insertion path, or the optimal needleinsertion path can be automatically chosen with some optimization criteria. Based on a mathematical description of the critical structures, an analytical expression of the CFRW of the needle is obtained, whereby the needle-insertion path can avoid interference with blood vessels, ribs and other obstacles. This work provides an effective and accurate method to aid the surgeon in selecting a needle-insertion path, which can improve the efficiency and safety of the operation, as well as significantly reduce the surgeon's workload.