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.

Automated summary

Dipole field navigation (DFN) is a method for navigating microcarriers towards tumor regions by distorting the magnetic field of an MRI scanner, with a piezoelectric system proposed for precise movement. In vitro experiments showed reliable targeting assessments with magnetic distortions for successful navigation of magnetic microparticles, albeit with some decrease in SNR and minor image distortion.