Fabrication and Biocompatibility Testing of Thin-Film Metamaterial Neurostimulation Leads for Magnetic Resonance Imaging.

OBJECTIVE

Chronically implantable neurostimulation leads, such as those used for deep brain stimulation, remain only partially MRI-compatible due to the presence of wire conductors that can induce hazardous radiofrequency (RF) heating. As a result, current systems are limited to MRI-conditional use, restricting patients' access to routine clinical imaging. Here, we propose a novel metamaterial based Resistive Tapered Stripline (RTS) architecture as a candidate solution for next-generation DBS leads.

METHODS

The RTS design incorporates impedance transitions along the lead, producing metamaterial-like behavior that increases inductance and promotes RF current reflection and dissipation while preserving low-frequency electrical conduction required for the therapeutic stimulation. Ultrathin titanium-gold microstrip segments with sharp impedance transitions were fabricated via physical vapor deposition on a non-conductive, non-magnetic substrate wire, with electrical properties guided by electromagnetic simulations. Material biocompatibility was evaluated in a rodent model following ISO 10993-6 guidelines.

RESULTS

Scattering-parameter measurements demonstrated high RF reflection (>64% of incident power), low transmission, and symmetric electrical behavior, confirming effective suppression of RF coupling. Histological analyses of microgliosis, astrocytosis, neurodegeneration, demyelination, and cellular composition showed no significant differences between RTS wires and commercially available DBS leads, confirming material biocompatibility.

CONCLUSION

We developed and tested a novel technology specifically designed as a candidate for future MRI compatible implantable DBS leads.

SIGNIFICANCE: This technology could represent a promising advancement toward MRI safer implantable neurostimulation systems, enabling broader access to high-quality MRI while maintaining device performance and long-term biocompatibility. Its versatile materials and manufacturing approach could be potentially extended to other chronically active implantable leads.