A Pneumatically Actuated Robotic Assistant for MRI-Guided Stereotactic Neurosurgery

Abstract

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 $0.97 \pm 0.42$ mm for tip position and $0.46 \pm 0.23^{\circ } $ for needle angle. System-level accuracy was then evaluated in MRI-guided phantom studies, showing errors of $1.38 \pm 0.80$ mm in tip position and $1.08 \pm 0.67^{\circ } $ 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%.