  Combining the unmatched soft-tissue imaging capabilities of magnetic
resonance imaging (MRI) with high precision robotics has the potential to
improve the accuracy, precision, and safety of a wide range of image-guided
medical procedures. However, the goal of highly functional MRI-compatible
robotic systems has not yet been realized because conventional electromagnetic
servomotors used by medical robots can become dangerous projectiles near the
strong magnetic field of an MRI scanner. Here we report a novel electromagnetic
servomotor design that is constructed from non-magnetic components and can
operate within the patient area of clinical scanners. We show that this design
enables high-torque and precisely controlled rotary actuation during imaging.
Using this servomotor design, an MRI-compatible robot was constructed and
tested. The robot demonstrated that the linear forces required to manipulate
large diameter surgical instruments in tissues could be achieved during
simultaneous imaging with MRI. This work presents the first fully functional
electromagnetic servomotor that can be safely operated (while imaging) in the
patient area of a 3 Tesla clinical MRI scanner.
