We worked on the development of implantable connectors, minimal invasive electrodes, impact resistant implant package, wireless link improvements and reduction of heat dissipated by the implant, data cloud and MRI compatibility.
A disconnection between electrodes and implant electronics using implantable connectors is desired, since it has several advantages related to implantation surgery. CorTec developed and built 8-way implantable connectors: The female connector part is attached to the implant electronics while the male part is located at the end of the electrode cable. After prototyping, CorTec has carried out extensive tests on long-term electrical performance, mechanical robustness and biocompatibility. The electrodes themselves were developed to be slightly stiffer, permitting burr-hole implantation, avoiding the need for a very invasive craniotomy.
The implant electronic itself uses wireless links for communication and power supply. The wireless communication link operates in the ISM band at 2.4 - 2.5GHz and is prone to interfere with other mobile devices. Therefore, a data collision minimization strategy was developed and implemented. The system selects one of 7 available channels inside the band for its communication and once this channel is disturbed by another wireless devices, the system switches to another channel. This method led to a dramatic improvement of wireless link stability. Further reliability of wireless communication was achieved by re-locating the antenna from the communication unit to the headpiece, effectively reducing the potential constellations of distance and angles between implanted and body-external communication antennas.
The implant consumes electric power, which is eventually dissipated as heat. Heat can lead to biological tissue damage, and therefore has to be minimized. Temperatures were found to be just below acceptable limits, but only with little safety margin. Modifying the electronic circuitry reduced power consumption by 30%, resulting in lower implant temperatures. Furthermore, the hermetic package that protects implanted electronics from body liquids was strengthened to meet latest normative requirements on mechanical impact robustness. We exchanged the Al2O3 packaging lid by a ZrO2 lid.
The compatibility of the system with a 3.0T MRI scanner was investigated with the result, that heating is most likeley not to reach critical levels of 2.0K neither do the magnetic forces, but the implanted system causes by it's permanent magnet a strong image shadowing of about 50mm radius, compromising the diagnostic purpose of MRI head scans.
The system streams the recorded brain data and also the protocol of system events to the newly developed and build cloud, where (still) simple visualisation tools permit the display of the data.
Cybersecurity plays an important role - perhaps not so much in the first clinical feasibility study - but in the later product. Therefore cybersecurity measures such as AES128 decryption of the wireless communication was implemented. A third party evaluated the effectiveness of our cycbersecurity measures with some recommendation for improvement for the final product.
