P.A. Roche

Passing data and supplying power to neural implants

This work investigates two important components in neural implants, the information link and the energy source. In this paper, a new concept in which neural implants operate on the biological resources readily available to them is adopted. The volume conduction property of human tissue is employed to pass information, and the electrons released during cellular metabolic process are collected to supply power. The x-antenna has been developed for data communication wherein the volume conduction mechanism has been used. The paper has shown that the bodys own energy stores can be converted to electrical current using a biofuel cell. The biofuel cell approach would provide not only uninterrupted power but also an opportunity to explore new methods fostering improved biocompatibility for implantable devices

Application of the reciprocity theorem to volume conduction based data communication systems between implantable devices and computers

There have been increasing needs for a wireless two-way information channel between computers and microdevices implanted within the human body. It has been demonstrated that this channel can be established based on the volume conduction property of the biological tissue. This paper presents a fundamental property of the volume conduction channel. By applying the reciprocity theorem to this channel, we show that it is a symmetric channel, i.e., the sensitivity of signal transmission is independent of the direction of information flow. We discuss several important factors in actual data communication systems that produce discrepancies from the assumptions of the reciprocity theorem. We also present experimental results based on a physically constructed volume conduction model. The reciprocity property demonstrated in this paper provides theoretical guidelines for the design of volume conduction based, energy-efficient data communication modules for various implantable devices.

A volume conduction antenna for implantable devices

We have developed a new volume conduction based antenna, called the x-antenna, that can be embedded in, or connected to, various implantable medical devices. This miniature antenna and an associated transceiver establish a wireless two-way data communication link between a wearable computer and implanted sensors/actuators to perform a variety of therapeutic and diagnostic functions within the human body. Our experiments have shown that the x-antenna requires less than one microwatt of energy to perform data communication tasks, more energy-efficient than any other known data communication modality.

Optimization of an implantable volume conduction antenna

As implantable devices become increasingly sophisticated, there is a strong need for developing a wireless data communication channel between these devices and external computers. This important problem has been studied and an antenna is being designed based on the volume conduction of biological tissues. Closed-form equation and finite element analyses were performed for the case of brain implantation using a spherical volume conduction model of the head. Finite element proofs of concept in 2D and 3D demonstrated the influence of epoxy and a volume conductor reflector on volume currents, exhibiting changes in the far field as controlled by the near field. A 3D finite element analysis showed an increased signal transduction of 35% as compared to the 3D analytical analysis, which was not able to simulate the epoxy. The optimum angle of inclination is shallower than what was intuitively thought, indicating that the antenna elements destructively interfere with the generated surface voltages, requiring the antenna elements to be rotated away from each other.

Using a cell phone for biotelemetry

A cell phone can be used to transmit data for biological monitoring and diagnosis, in addition to its usual functions, without requiring modification. This paper discusses the benefits, obstacles, and methods of using cell phones to transmit biological waveforms to increase the mobility of patient monitoring and facilitate critical care before the patient even boards the ambulance.

Signal multiplexing and modulation for volume conduction communication

Volume conduction communication is an efficient means of transmitting signals within the human body. The paper introduces a multiplexing and modulation method which minimizes circuit complexity, space, and power consumption.

Analytical and numerical optimization of an implantable volume conduction antenna

As implantable devices become increasingly sophisticated, there is a strong need for developing a wireless data communication channel between these devices and external computers. This important problem has been studied and an antenna is being designed based on the volume conduction of biological tissues. Closed-form equation and finite element analyses were performed for the case of brain implantation using a spherical volume conduction model of the head. A 2D proof of concept was done showing the influence of a volume conductor reflector on volume currents, exhibiting changes in the far field as controlled by the near field. A 3D finite element analysis showed an increased signal transduction of 35% as compared to the 3D analytical analysis, which was not able to simulate the epoxy.

Computer Simulation of Volume Conduction Based Data Communication Channel for Neuroprosthetic Devices

Neuroprosthetic devices often require an information channel to communicate with external computers through biological tissue. Traditionally, this channel is provided either by a bundle of wires penetrating the skin or by a radio-frequency coupler. In a different approach, the ionic fluid within the human body is utilized to establish a data communication channel. We investigate a number of important issues related to the antenna of this channel, including the surface shape, curvature, and orientation. The finite element method is utilized to optimally select system parameters according to the dimensions of the neuroprosthetic device and the site of implantation

Designing a cell phone adaptor for biological waveform transmission

The cell phone is a powerful and plentiful tool which can be wielded to transmit data for biological monitoring and diagnosis, in addition to its usual functions, without requiring modification. This paper discusses the benefits, obstacles, and methods of using cell phones to transmit biological waveforms.

Biological resources within the human body can be used to operate neural implants

Implantable neural devices have many therapeutic, diagnostic, and prosthetic applications. Although there have been exciting developments in constructing these devices, two critical problems, data communication between the implanted device and external computers as well as electrical power to the device, have not yet been solved. We investigate these problems using the volume conduction properties of the human body. A prototype implantable device is constructed equipped with a volume conduction data communication channel. A new power delivery antenna is conceptualized, inspired by a study of the power delivery mechanisms of electric fish. Our investigation indicates that the volume conduction resources within the human body may provide a powerful solution to both problems.