Real-time positioning and tracking technique for endovascular untethered microrobots propelled by MRI gradients

A real-time positioning and tracking technique for untethered devices or robots magnetically propelled by a clinical magnetic resonance imaging (MRI) system is described. The local magnetic field induced by the device, composed of a ferromagnetic material, is used as a signature to localize the device on three one-dimensional projections. A high-precision 3D circular-motion system was used to assess the precision and accuracy of this method. The integration of this technique inside propulsion and imaging MRI sequences was also achieved to demonstrate the feasibility of this tracking scheme in a closed-loop control scheme. Finally, in vivo tracking during automatic navigation of an untethered device in the carotid artery of a living animal is demonstrated.