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Magnetic Control of a Flexible Needle in Neurosurgery

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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 and enhance the current neurosurgical technique. The principal mechanism is to create asymmetric stress surrounding the needle tip enabling the soft tissue to be traversed in an optimal direction.

We have developed a magnetically guided flexible needle specially designed for neurosurgical use. 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.

In this paper, we addressed the feasibility of navigating a flexible needle with fluoroscopic imaging and magnetic steering in soft tissue environments. We employed an electromagnetic navigation system designed for animal trials and a projective X-ray fluoroscope as visual feedback, which improve the clinical relevance. A closed-loop control strategy was implemented to perform automatic navigation of a flexible needle along the targeted trajectory. The experimental work was performed using an in vitro brain phantom and ex vivo pig brain. In the agarose brain phantom, the magnetic needle could follow the predefined straight and curved paths along the trajectories with the RMS errors below one millimeter. In the dissected pig brain, we demonstrated the feasibility of using the proposed magnetically guided flexible needle in a heterogeneous environment.

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