Abstracts

Rationale: Implementation of advanced far-field wireless technology in neurostimulators may help enhance and improve the treatment of epilepsy. Far-field wireless provides greater range of operation and data transfer speeds compared to the close-range inductive coupling used in current FDA approved epilepsy implants. Cyberonics, the creator of the VNS Therapy® System is developing a system utilizing far-field technology in an implantable neurostimulator. This technology enables greater wireless distances between the implant and programmer, making office visits less intrusive to the patient. The higher data-speeds may improve device interrogation and data-download times. This technology may also help facilitate the surgery, allowing for communication in parallel with other procedures and alleviating the need to bring an external programmer into the sterile field. Methods: Current FDA approved implants for epilepsy have a titanium-based housing and utilize inductive coupling via low-frequency waves (<100s kHz). Far-field wireless, which uses higher frequencies (>1 MHz), cannot penetrate through metal and thus, innovative configurations are required. Here, a unique planar antenna is designed and positioned behind a hermetically sealed ceramic window which allows wireless transmission outward. Antenna diversity is also implemented in the external programmer. A specific Federal Communications Commission allocated band for medical devices (402-405 MHz) is used along with wireless protocols and key-based authentication to minimize interference and prevent unintentional communications. Simulation modeling accounting for multiple tissues types and layers, use of phantom recipes, iterative design methods, and in vivo studies were performed during development. Multiple use-case studies were done to set specific design criteria such as distance, speed, and orientations; and testing to specification was done in anechoic chambers and representative operating rooms. Results: A consistent communication distance of greater than 1.5 meters was achieved, which is over 30 times further than the wireless range of current FDA approved implants for epilepsy. Also compared to these approved devices, this wireless technology achieves a data-rate of over 100 times greater. The antenna patterns were optimized per use-case studies and design specifications were achieved for typical clinician-patient orientations. Design, development, and testing show this communication technology has a minimal impact on battery life and is both robust and reliable. Conclusions: Far-field based wireless technology offers greater range and faster communication speeds than existing inductive-based wireless technique used in current neurostimulation devices targeting treatment of epilepsy. While still under development, these improvements may increase device programming efficiency during the implantation procedure and follow-up visits. High data-rate far-field wireless is also a prerequisite for implementation of future technologies and features as we aim towards achieving the best treatment for patients with epilepsy.