Enhanced torque-based impedance control to assist brain targeting during open-skull neurosurgery : a feasibility study

Background: Cooperatively-controlled robotic assistance could provide increased positional accuracy and stable and safe tissue targeting tasks during open-skull neurosurgical procedures, which are currently performed free-hand. Methods: Two enhanced torque-based impedance control approaches, i.e. a variable damping criterion and a force-feedback enhancement control, were proposed in combination with an image-based navigation system. Control systems were evaluated on brain-mimicking phantoms by 13 naive users and 8 neurosurgeons (4 novices and 4 experts). Results: In addition to a 60% reduction of user effort, the combination of the proposed strategies showed comparable performances with respect to state-of-the-art admittance controller, thus satisfying the clinical accuracy requirements (below 1mm), reducing the hand tremor (by a factor of 10) and the tissue's indentation overshooting (by 80%). Conclusion: Although the perceived reliability of the system should be improved, the proposed control was suitable to assist targeting procedures, such as brain cortex stimulation, allowing for accurate, stable and safe contact with soft tissues.