Error propagation of the robotic system for liver cancer coagulation therapy

The goal of this paper is to establish the error propagation model of the ultrasound-guided robot for liver cancer coagulation therapy, which consists of ultrasound machine, image-guided software subsystem, position tracking unit and needle-driven robot. The target of tumor is transformed to robot coordinate frame to let the robot move to the target. The transformation includes three dimension ultrasound construction, registration between pre-operative model and intra-operative physical body, coordinate transformation from position tracking unit to robot. The factors affecting the system accuracy can be expressed by the sum of target mapping error and robot positioning error. Then, the propagation model of target mapping error on the Euclidean motion group is established. At last, the simulations of the propagation model of target mapping error and the experiment of the system accuracy are carried out and the results show our proposed error propagation model is efficient and the system accuracy can satisfy the need of coagulation therapy for liver cancer.