Carbon nano-structured neural probes show promise for magnetic resonance imaging applications

Objective. Previous animal studies have demonstrated that carbon nanotube (CNT) electrodes provide several advantages of preferential cell growth and better signal-to-noise ratio (SNR) when interfacing with brain neural tissue. This work explores another advantage of CNT electrodes, namely their MRI compatibility. MRI-compatible neural electrodes that do not produce image artifacts will allow simultaneous co-located functional MRI and neural signal recordings, which will help improve our understanding of the brain. Approach. Prototype CNT electrodes on polyimide substrates are fabricated and tested in vitro and in vivo in rat brain at 9.4 T. To understand the results of the in vitro and in vivo studies, a simulation model based on numerical computation of the magnetic field around a two-dimensional object in a tissue substrate is developed. Main Results. The prototype electrodes are found to introduce negligible image artifacts in structural and functional imaging sequences in vitro and in vivo. Simulation results confirm that CNT prototype electrodes produce less magnetic field distortion than traditional metallic electrodes due to a combination of both superior material properties and geometry. By using CNT films, image artifacts can be nearly eliminated at magnetic fields of strength up to 9.4 T. At the same time, the high surface area of a CNT film provides high charge transfer and enables neural local field potential recordings with an equal or better SNR than traditional electrodes. Significance. CNT film electrodes can be used for simultaneous MRI and electrophysiology in animal models to investigate fundamental neuroscience questions and clinically relevant topics such as epilepsy.