Design of a Novel, Low-Cost System for Neural Electrical Impedance Tomography

New measurement techniques are needed to extract fascicle-level activity from nerves using minimally invasive electrode implants, such as cuff electrodes, in order to increase the recording sensitivity of chronically implanted arrays without jeopardising patient safety or electrode viability. This is key to closing the control loop for PNS-integrated prosthetic devices by enabling designers to selectively measure activity in specific motor fascicles, thus allowing for movement intention to be decoded from bulk activity. Electrical impedance tomography (EIT) is an established way to increase the spatial sensitivity of non-invasive recordings made using circumferential electrode arrays, but lacks experimental data proving its effectiveness in neural applications (N-EIT). This paper presents the design of a novel system for N-EIT that is meant to act as a lower cost option for exploratory work in this area when compared to solutions found in the existing literature. The measured characteristics of the system are shown to fit well into simulated parameters, and to be suitable for use ex vivo and in vivo NEIT experiments. Finally, the paper proposes a direction for future development in this field based on the refinement of N-EIT as a technology and the synergistic implementation of current steering capability to allow for selective stimulation and recording through a single electrode cuff array.