A Pneumatically Actuated Robotic Assistant for MRI-Guided Stereotactic Neurosurgery

This paper presents the development and cadaveric evaluation of a pneumatically actuated robotic assistant for MRI-guided stereotactic neurosurgery. The robot features two coaxial arcs that provide four degrees of freedom to position and orient a needle within an MRI scanner. It is driven by custom-designed MR-Safe pneumatic stepper motors and powered by in-room compressed medical air, enabling precise interventions under intraoperative MRI guidance. To improve anatomical visualization, two custom MR imaging coils were developed and integrated with the system. A dedicated clinical workflow was also proposed for robot-assisted stereotactic procedures under MRI-guidance. Targeting accuracy was first assessed in free space using an optical tracking system, yielding mean absolute errors of 0.97 ± 0.42 mm for tip position and 0.46 ± 0.23° for needle angle. System-level accuracy was then evaluated in MRI-guided phantom studies, showing errors of 1.38 ± 0.80 mm in tip position and 1.08 ± 0.67° in angle. Finally, a cadaver study validated the clinical workflow, with observed errors of 2.11 mm in position and 3.32° in angle. Quantitative imaging analysis confirmed minimal image degradation, with signal-to-noise ratio (SNR) variation below 12.26% and 2D geometric distortion under 0.20%.