Multi-Imager Compatible, MR Safe, Remote Center of Motion Needle-Guide Robot.

We report the development of a new robotic system for direct image-guided interventions (DIGI; images acquired at the time of the intervention). The manipulator uses our previously reported pneumatic step motors and is entirely made of electrically nonconductive, nonmetallic, and nonmagnetic materials. It orients a needle-guide with two degrees of freedom (DoF) about a fulcrum point located below the guide using an innovative remote center of motion parallelogram type mechanism. The depth of manual needle insertion is preset with a third DoF, located remotely of the manipulator. Special consideration was given to the kinematic accuracy and the structural stiffness. The manipulator includes registration markers for image-to-robot registration. Based on the images, it may guide needles, drills, or other slender instruments to a target (OD < 10 mm). Comprehensive preclinical tests were performed. The manipulator is MR safe (ASTM F2503-13). Electromagnetic compatibility (EMC) testing (IEC 60601-1-2) of the system shows that it does not conduct or radiate EM emissions. The change in the signal to noise ratio of the MRI due to the presence and motion of the robot in the scanner is below 1%. The structural stiffness at the needle-guide is 33 N/mm. The angular accuracy and precision of the manipulator itself are 0.177° and 0.077°. MRI-guided targeting accuracy and precision in vitro were 1.71 mm and 0.51 mm, at an average target depth of ∼38 mm, with no adjustments. The system may be suitable for DIGI where [mm] accuracy lateral to the needle (2D) or [mm] in 3D is acceptable. The system is also multi-imager compatible and could be used with other imaging modalities.