Bozhi Ma

The Transcutaneous Charger for Implanted Nerve Stimulation Device

Implanted nerve stimulation offers many advantages to improve the QOL (quality of life) of the patients suffering from nervous system diseases such as Parkinsons disease and epilepsy. Secondary battery begins to be used instead of primary secondary, service life of the implanted device is extended and the device becomes smaller and lighter. For charging the secondary battery fit in the body, a transcutaneous charger is designed. Two coupling coils designed specially are used to transmit and receive energy. With the mentioned coupling coils, the charger attains 15 mA charge current and the charge requirement is satisfied

In vivo experimental study of thermal problems for rechargeable neurostimulators.

Eddy currents in the metal shell and copper losses in the coils generate heat in rechargeable neurostimulators, which increases the temperature of the adjacent tissue, potentially causing thermal damage of implant patients. Hence, there is an urgent need for a simple self‐help method to measure the temperature of such subcutaneous devices.

A Method for Removal of Deep Brain Stimulation Artifact From Local Field Potentials

This paper presents a signal processing method for the electrophysiology simultaneously recorded during deep brain stimulation (DBS) as a research tool. Regarding the local field potential (LFP) signals recorded during stimulation, a novel method was proposed for removal of stimulation artifacts caused by the much stronger stimulating pulse compared to typical LFP. This artifact suppression method was tested and evaluated in an in vitro situation. The results indicate that the stimulation artifacts are well suppressed by this method. Secondly, this method was tested in vivo in Parkinson’s disease (PD) patients. It was used to process the LFP signals recorded intraoperatively from PD patients to preliminarily explore the quantitative dependencies of beta band synchronization variations in the subthalamic nucleus (STNs) on the applied DBS parameters, including stimulation voltage, frequency and pulse width. The results confirm that DBS therapy can suppress excessive beta frequency activity and that the degree of attenuation increases with increasing DBS voltage within a range of 1–3 V and increasing DBS frequency within a range of 60–120 Hz. The proposed artifact suppression method provides technical support for exploring the direct effect of electrical stimulation on the brain activities.

Design and analysis of a transcutaneous telemetry device for brain stimulator

This paper proposes a transcutaneous bidirectional telemetry solution using resonant electromagnetic coupling and pulse interval modulation for low power loss and high performance in neuro-stimulator. The resonant electromagnetic coupling model is established on the base of resonance electromagnetism theory, and relationships between coupling coefficient, displacement tolerance, resonance frequency and telemetry distance are studied experimentally. One air-core coil is used as a time-shared transmitter and receiver antenna for controller, and one ferrite-core coil is used as the counter part for implantable device, which decreases the volume of the implantable part. Experiments verified that the average power consumption was about 33 uW for implantable part in this device under the testing condition of over 10cm telemetry distance between the implantable part in titanium container and controller. Simultaneously, telemetry device is with good displacement tolerance.

Study on DBS device for small animals

Although deep brain stimulation (DBS) therapy has been achieved, fine tuning on the operational parameters and the equipment are needed in order to make the stimulation treatment more applicable. Thus, the purpose of this study is to design and produce a deep brain stimulation device for DBS experiments for small animals (e.g. rats). Physical size, durability, cost of device and convenience of operation are the major focuses in this study. The designed pulse generator can produce pulses with adjustable frequencies, pulse widths and amplitudes. Telemetry and remote control of the system reduced the physical size of the implant component. Battery voltage measurement and electrode impedance measurement justified the values of parameters applied for stimulation. Power consumption is low enough and test results show it is expected to work for more than three months when using typical pulse parameters. Finally, we use the device on the DBS experiment of rats. The results prove that the design of the device can fulfill the requirements for deep brain stimulation in animal experiments.

System of magnetic coupled PPM transcutaneous wireless communication

There are still some problems in telemetry technique for implantable medical systems now, such as relatively high power consumption, complex circuits or large bulk. In order to solve above problems, an effective pulse position modulation (PPM) method is adopted in this paper, that make possible the design of simultaneously lower power consumption, good communication distance and good displacement tolerance while keeping circuitry simple, particularly in the implantable device. PPM is frequently used in lower power consumption or high reliability systems. We use 2-PPM in this paper, all the coding and decoding processes of PPM are completed with microchip. The approach of transmitting signal is via two magnetic coupling coils, air-cored coil of φ50mm for programmers and ferrite-cored coil of φ3.8mm for implantable device. A magnetic coupled PPM transcutaneous wireless communication resolution is presented in this paper. Full-bridge topology with push-pull driving is adopted as amplifier in programmer. Compared with the common-used class-E amplifier, the full-bridge one is simple and reliable. In this paper, over two inches bidirectional communication distance between implantable device in the body, with titanium container, and programmer outside the body is realized, at the same time, the communication system is with good displacement tolerance and coil displacement mismatch question is well solved. The average power consumption is about 33uA under typical condition for implantable communication device in the PPM system, it is lowered greatly compared with our amplitude shift-keying (ASK) system, ASK’s average power consumption is about 10.3mA at the same test condition.

Burn-in method study of surface mounted plastic encapsulated devices and board-level verification

Industry-level plastic encapsulated devices have been used gradually in high reliability field. The screening and qualification procedures of package-level and board-level are necessary for high reliability, in which burn-in is a key part. In this paper, board-level test was carried out based on implantable brain simulator circuits of our lab. A burn-in method for surface mounted plastic encapsulated devices is presented in this paper, and the junction temperature control is based on case temperature control and equivalent thermal resistance value between case and junction, board-level test was carried out after package-level devices burn-in for avoiding devices potential invalidation caused by unsuitable stress during burn-in.

A new respiratory training system for astronauts

More and more astronauts and common people will be sent to space. When going to space from the earth or return to the earth from space in a spaceship, especially in emergency, men will suffer from hyper-gravity. Hyper-gravity can induce much sickness, and endanger the life of human. Respiratory training in advance can help astronauts to tolerate much higher gravity values. A new respiratory training system was developed for astronauts. The system can be well worked for astronauts now.

A new method of radio frequency links by coplanar coils for implantable medical devices

A new method based on coplanar coils for the design of radio frequency links has been developed, to realize the communication between the programming wand and the implantable medical devices with shielding container simply and reliably. With the analysis of electronic and magnetic field theory, the communication model has been established and simulated, and the circuit has been designed and tested. The experimental results are consistent with the simulation fairly well. The voltage transfer ratio of the typical circuit with present parameters can reach as high as 0.02, which can fulfil the requirements of communication

Data security: a novel robust regulator design for Portable/implantable multimedia models

Portable/implantable multimedia tools have become increasingly popular in recent years, and data transfer’s security is so important in models of these tools. To ensure data’s stable transfer, a robust voltage regulator is required. Meanwhile, this data transfer usually requires relative complex voltage supplies from limited voltage sources. These specific voltage supplies, which are usually higher than the battery’s output voltage, are widely used by multimedia tools to accomplish interactive communication with the human body. This paper describes a novel regulator design to generate higher voltages from a lower voltage supply (e.g. battery’s voltage), and the robustness of this regulator could ensure data transfer’s security in multimedia models. We first designed a reconfigurable output voltage for compatibility with different multimedia applications. The regulator was made to be highly efficient, fulfilling a critical characteristic for portable/implantable multimedia models. This design also demonstrated reliability and robustness, allowing the highest output voltage to approach to the process tolerance. From simulation, it was indicated that the regulator design had better electrical parameters and more robustness than previous studies, which could ensure the data security for multimedia models.