A leadless power transfer and wireless telemetry solutions for an endovascular electrocorticography

TL;DR

This work targets wireless data and power delivery for endovascular ECoG by combining optical data telemetry with FUS-powered piezoelectric energy harvesting embedded in a stent. The approach enables leadless communication and energy supply, demonstrated through an optical link using a single LED transmitter and an APD receiver, achieving up to 5 Mbit/s data transfer with sub-3 mW power consumption, and delivering about 10 mW total power with multiple piezoelectric harvesters under safe ultrasound conditions. Proof-of-concept tests using fresh bovine tissue and discrete components show the feasibility of integrating sensing, data communication, and power management within a compact stent cross-section, with BERs below 10^-8 to 10^-9 over extended testing. The results highlight potential benefits for pediatric and vasculature-fragile patients by removing long implanted cables and enabling scalable eBCIs, while underscoring the need for ASIC integration, biocompatibility validation, and in-vivo testing for clinical readiness.

Abstract

Endovascular brain-computer interfaces (eBCIs) offer a minimally invasive way to connect the brain to external devices, merging neuroscience, engineering, and medical technology. Achieving wireless data and power transmission is crucial for the clinical viability of these implantable devices. Typically, solutions for endovascular electrocorticography (ECoG) include a sensing stent with multiple electrodes (e.g. in the superior sagittal sinus) in the brain, a subcutaneous chest implant for wireless energy harvesting and data telemetry, and a long (tens of centimetres) cable with a set of wires in between. This long cable presents risks and limitations, especially for younger patients or those with fragile vasculature. This work introduces a wireless and leadless telemetry and power transfer solution for endovascular ECoG. The proposed solution includes an optical telemetry module and a focused ultrasound (FUS) power transfer system. The proposed system can be miniaturised to fit in an endovascular stent. Our solution uses optical telemetry for high-speed data transmission (over 2 Mbit/s, capable of transmitting 41 ECoG channels at a 2 kHz sampling rate and 24-bit resolution) and the proposed power transferring scheme provides up to 10mW power budget into the site of the endovascular implants under the safety limit. Tests on bovine tissues confirmed the system's effectiveness, suggesting that future custom circuit designs could further enhance eBCI applications by removing wires and auxiliary implants, minimising complications.

Figures (12)

• Figure 1: (a) Illustration of the system. In sub-figure a, the green arrow shows the tissues. (1) Skin tissue, (2) Bone tissue, (3) Dura mater, (4) Superior sagittal sinus. The system will have two parts. An implantable stent and an external device. All electrical components will sit in the stent in the superior sagittal sinus for the implantable part. The external device sits over the scalp and aligns with the implant. In the external device, an avalanche photodiode is used to collect optical signals from the implant, and an FPGA is used to decode the optical data. The ultrasound transducer array in the external device will generate focused ultrasound that delivers energy to the stent. Sub-figure b shows the stent with functional components. The sensing electrodes are on the stent for sensing electrical signals from the cortex. Three piezoelectrics sit in the stent to convert energy from focused ultrasound (FUS) to power the circuit. The optical transmitter, an 810 nm wavelength LED (shown in red), sits in a space within the stent. Two ASICs with control and sensing circuits, energy harvesting and power management circuit and LED driver sit in other spaces within the stents.
• Figure 2: (a) Skin, (b) Connective tissue, Galea aponeurotica, Loose areolar connective tissue, Periosteum, (c) Skull, (d) Dura Mater, (e) Superior sagittal sinus Wall. Dn is the diameter of the lens. Alpha is the emitting angle of the LED, which the emitting lens can control. The arrows represent the diffusion (blue), reflection (red), and absorption effect (purple).
• Figure 3: System block diagram. The top left corner shows the blocks in the external device. The data recovery will be implemented on FPGA and the wireless power delivery unit will be described in another work. The upper right part shows the blocks in the implant. The lower right part shows the potential components' size with an actual stent. The LED is a commercially available one and has a big substrate. We need a customized smaller substrate to meet our purpose.
• Figure 4: The structure of the piezoelectric harvester //Illustrating the process of electrical energy generation using Piezo-FUS: A focused ultrasound beam (blue ellipse) targets a stent embedded with a thin layer of piezoelectric material (highlighted in orange). Upon interaction with the ultrasound, the piezoelectric layer converts the acoustic energy into electrical energy, represented by the lightning bolt symbol.
• Figure 5: Modelled focused ultrasound/brain, (a) real CT (computed tomography) scan images, (b) modelled human head and a single spherical focused ultrasound transducer, (c) $P_0$ acoustic wave propagation through the head by the transient solution and the transient acoustic pressure at the scalp, and (d) the steady state solution of acoustic pressure and the acoustic pressure at the focal line.