A Piezoelectric Robotic System for MRI Targeting Assessments of Therapeutics During Dipole Field Navigation

Dipole field navigation (DFN) is a method that has been developed to deliver therapeutics toward tumoral regions by navigating microcarriers in the vascular network. To do so, DFN distorts the high uniform magnetic field of a clinical magnetic resonance imaging (MRI) scanner using precisely located ferromagnetic balls to create magnetic gradients to implement the directional forces required to navigate magnetically saturated therapeutic microcarriers along a planned trajectory in the vasculature. Such local distortions of the magnetic field prevent MRI-based targeting assessments. As such, a system must be put in place to precisely move the ferromagnetic balls back-and-forth to alternate between MRI targeting assessment and DFN. Here, a piezoelectric actuation system is proposed. In vitro experiments conducted inside the bore of a 3T clinical MRI scanner show the feasibility for reliable targeting assessments with magnetic distortions sufficient to achieve a 100% success rate of magnetic microparticles being navigated through a predefined target branch at a bifurcation. Results show a 21.6% decrease in SNR with a maximum value of 2.2% MR-image distortion and a faintly visible image artifact after the piezoelectric system moved the soft ferromagnetic balls in the MRI targeting assessment position.