This paper introduces the design and kinematic analysis of a 5-DOF (multiple degree of freedom) hybrid-driven MR (Magnetic Resonance) compatible robot for prostate brachytherapy. It can slip the leash of template and rely on the high precise of MR imaging. After a brief introduction on design requirements of MR compatible robot, a description of our robot structure, material selection, hybrid-driven, and control architecture are presented. Secondly, the forward kinematics equations are obtained according to the equivalent diagram of this robot, and the actual workspace can be outlined. This will help the designer to determine whether this robot can be operated in the MR core without intervention with patient. And then, the inverse kinematics equations combined with trajectory planning are used to calculate the actuators movement. This will help the control system to manipulate the robotic accurately. Finally, vision based experiments on phantoms are used to verify the mechanism precision. As the results shown, the needle tip precision of mechanism is 0.9 mm in the general lab environment.

Hepatocellular carcinoma (HCC), which leads to more than one million deaths every year in the world, is the second most common malignancy in China. As microwave ablation (MWA) is an effective method for the treatment of liver cancer, an ultrasound-directed (US-directed) robotic system was designed to assist surgeons on positioning the needle. This interventional robotic system includes a 5-DOF needle-guiding robot, a conventional 2D ultrasound device, a workstation for path planning and image processing and an electromagnetic tracking device. In clinical environments, we first use real-time freehand 3D ultrasound reconstruction and image analysis methods to attain tumour position, and then manipulate the guiding hole of the robot to position the needle affirmed by the surgeon. Finally, the feasibility of the interventional robotic system are validated by experimental results.