Magnetic Control of a Flexible Needle in Neurosurgery.

Minimally invasive neurosurgery does not require large incisions and openings in the skull to access the desired brain region, which often results in a faster recovery with fewer complications than traditional open neurosurgery. For disorders treated by the implantation of neurostimulators and thermocoagulation probes, current procedures incorporate a straight rigid needle, which restricts surgical trajectories and limits the number of possible targets and degrees of freedom at the respective target. A steerable needle with a flexible body could overcome these limitations. In this paper, we present a flexible needle steering system with magnetic and fluoroscopic guidance for neurosurgical procedures. A permanent magnet at the proximal end of a flexible needle is steered by an external magnetic field, and the resultant tip-deflection angle bends the flexible body like a bevel-tip needle. We implemented a kinematic model for the magnetic needle derived from a nonholonomic bicycle model and a closed-loop control strategy with feed-forward and feed-back components using a chained-form transformation. The proposed needle steering method was investigated through in vitro and ex vivo experiments.