Needle Guiding Robot with Five-Bar Linkage for MR-Guided Thermotherapy of Liver Tumor

This paper reports the robot for horizontal gap open MRI which controls needle orientation effectively in the vertically limited gantry space. We locate the robot including actuators wholly in MR gantry and puncture needle from side of patient’s body. The robot has three Degree-of-Freedom (DOF) and can control needle orientation using five-bar linkage mechanism and gimbal mechanism. Two DOF is to actuate five-bar linkage and the other DOF to make five-bar linkage up and down. In experiments, the accuracy of five-bar linkage was 0.89±0.15 [mm] on a whole average and the accuracy of vertical placement of five-bar linkage was 0.13±0.02 [mm]. MR images had insignificant degradation of 19.4% in attrition rate of S/N ratio at the maximum. We conclude that the robot can control needle orientation with high repeatability and high MR compatibility in the limited gantry space.