Design and Modeling of a 7-DOF MR-Conditional Robot for MRI-Guided Brain Stereotactic Surgery

In brain stereotactic surgery, the operation precision can be significantly improved if real-time magnetic resonance image (MRI) guidance is achieved. However, the limited space inside the MRI bore and the strong magnetic field pose challenges to performing robot-assisted brain stereotactic surgery in the MR environment. In this paper, a 7-degree-of-freedom (DOF) MRconditional robot with ultrasonic actuation is developed to operate inside the MRI bore. The robot consists of a 3-DOF translational positioning module and a 2-DOF remote center of motion (RCM) module for the adjustment of the puncture needle, and a 2-DOF feeding module for needle insertion. A workflow for robot-assisted brain stereotactic surgery is proposed. The performances of the robot are systematically tested. The signal-to-noise ratio (SNR) reduction to the MR images is measured to be below 6%, showing good MR compatibility. The RCM point shift is measured to be 1.01 mm, and the positioning accuracy and repeatability of the robot are measured to be 2.3610.14 mm and 0.3110.21 mm, respectively. Phantom experiments are performed in the MR environment, and the maximum positioning and orientation errors in the phantom are found to be 1.77 mm and 4.330, respectively. The experimental results demonstrate the feasibility of the developed robot in MRI-guided neurosurgery.