A Bellows-based Needle Insertion Robot with 2-DoF RCM Constraint

In recent years, magnetic resonance imaging (MRI) offers high-contrast images of soft tissue to monitor the ablation procedure,  an MRI-compatible robotic system aiming to target the lesions with high precision inside the MRI scanner for a better intraoperative procedure is necessary. 
To solve the leakage problem of conventional hydraulic drive robots, we presents an MR-safe needle insertion robot with 2 degrees of freedom (DOF) remote center of motion (RCM) mechanical constraint and based on a novel bellow actuator for in-bore MR image-guided minimally invasive biopsy. Further, to achieve real-time biopsy, an automatic needle insertion device was designed. To keep the Angle of the needle unchanged during force contact with the tissue, the whole system is designed to be stiff and a locking mechanism was added. Besides, a novel linked bellows hydraulic drive system and an MR-safe encoder comprising a grating scale and optical fibers were applied to drive the robot accurately. Finally, several experimental studies are done to evaluate the performance of this robotic system, whose mean motion error is 0.83mm, repeatable positioning accuracy is 0.56 and 0.39° of pitch and roll axis, and the holding torque of pitch and roll axis are 3.10 and 1.81 N·m, respectively.