Towards an MRI-Driven Robotic Cold-Snare System for Gastrointestinal Polyp Resection

Robotic manipulation can be applied in endoluminal interventions to enhance dexterity, ergonomics and precision. The strong background field generated by a Magnetic Resonance Imaging (MRI) scanner can be exploited to magnetise ferromagnetic objects within the scanner’s workspace. Magnetic imaging gradients can then be utilised to robotically manipulate such objects. Here, we propose an MRI-actuated cold-snare mechanism for gastro-intestinal polyp removal. The mechanism features a stationary 2 mm diameter ferromagnetic sphere fixed at the base of the instrument as well as a second 2 mm diameter sphere, tethered to the instrument tip. Magnetic gradients are used to manoeuvre the tethered sphere around a polyp, at which point magnetic attraction, induced by the MRI’s background field, is used to couple the two spheres. The tether is then pulled tight, resulting in a cut of the ensnared tissue. The dipole-dipole attractive force in the MRI scanner is characterised and validated indirectly utilising a linear stage and load-cell setup. The proposed device is tested in a pre-clinical MRI scanner by severing gelatine phantoms, where an average task completion time of 7 minutes and 36 seconds  ± 42.78 seconds.