Magnetic Fringe Field Navigation of a guidewire based on Thin Plate Spline modeling

Abstract

Fringe Field Navigation (FFN), a method first introduced by our group, aims at providing a high directional pulling force on a magnetic object such as a magnetic tip of a guidewire or other instruments. In a clinical setting, the pulling force is typically produced by the strong fringe field generated by the superconducting magnet of a clinical Magnetic Resonance Imaging (MRI) scanner. Because it is impossible or practical to move such a bulky magnet, directional changes are performed by robotically moving the patient in the magnetic fringe field outside the scanner. To do so, a homogenous transformation for each point in a set of discrete points in the magnetic field space must first be done and used to determine the position of the robotic manipulator to enable the steering of a guidewire equipped with a magnetic tip towards the desired direction. We used the Thin Plate Spline (TPS) method to model the magnetic field and to estimate the direction of the magnetic field required to navigate the guidewire along a predetermined path. We also propose guidelines for the sampling of the magnetic field to produce a more accurate TPS function. To prove the concept, we applied FFN on a small experimental prototype using a small permanent magnet and a robotic manipulator to steer a guidewire inside a phantom. The preliminary results suggest that the same approach could be scaled up for clinical applications taking advantage of the much stronger magnetic field generated by the superconducting magnet of already available MRI scanners.