Yusuke Sakaue

Development of Wireless Biosignal Monitoring Device

In this study we have developed a wireless biosignal monitoring device. This device consists of a chip micro processing unit, a three axis acceleration sensor, an ECG amplifier and a wireless serial communication module. This device was set on subjects waist near the center of gravity and was evaluated in filed exercises. As a result it was proved that real time remote monitoring of these biosignals in filed exercise can be achieved using this wireless communication device.

Signal Source Estimation Inside Brain Using Switching Voltage Divider

Visualization of neural activities inside the brain is useful for clarifying human brain function. Electroencephalogram (EEG) using a surface electrode is the most popular visualization method in laboratories, and estimation of the signal source using EEG has been extensively studied. Owing to the low spatial resolution of EEG, many surface electrodes are currently required for highly accurate estimates. In an attempt to improve the resolution, we developed a new EEG method in which the position information and potential of the signal source inside a human brain are obtained simultaneously from one signal electrode. A prototype device for proposed method has been developed, and experiments focused on EEG when the eyes were open and closed are conducted to validate our proposed method and device. Results show that the signal source position changes for the two conditions, and our method is plausible.

Development of Portable Monitoring Device with an Accelerometer and GPS Receiver for Health Management

In this study, we have developed a portable monitoring device for health management. The portable monitoring device is consisted of a one chip microprocessor, a GPS receiver, a tri-axial accelerometer and a memory card. The device is possible to get the physical activity from a tri-axial accelerometer, the speed, the position and number of satellites from a GPS receiver. When the GPS receiver tracks one or more target’s signel, it is estimateded that the subject is in outdoor. Because this device cannot receive the GPS signal in the case of the subject is indoor. We tried to measure the signal for a long term by using the portable monitoring device. As a result, a portable monitoring device worked accurately.

A new approach to estimate ECG signal source using voltage divider technology

In this study a new method for electrocardiogram (ECG) signal source estimation using voltage divider technology has been developed. This method enables simultaneous acquisition of two kinds of information from one single electrode, i.e., the signals source potential and its position. Conventional methods require many electrodes to estimate the signal source accurately, and this imposes extra burden on the subjects. Our new signal source estimation method would improve the accuracy of the signal source estimation and reduce the number of surface electrodes. In this study, we evaluated our estimation method in a human ECG measurement model. Results demonstrated that the signal source position could be estimated well in this model.

Evaluation of lower leg swelling using EMG measured with voltage divider.

The purpose of this study is to evaluate the lower leg swelling using EMG measured with our new voltage divider technology, by which the internal impedance of lower leg can be estimated. The amplitude of EMG measured without voltage divider was compared to it with voltage divider. Eleven healthy subjects (24.3±5.1 y.o.) participated in this study. Six female (swelling group) were asked to work at desk for six hours, and five male (control group) were asked to work a regular day. The internal impedance was calculated and calf circumference was measured before and after desk work. Results show that internal impedance in swelling group significantly decreased with increase in calf circumference, and our new evaluation method was proved to be effective for the evaluation of lower leg swelling.

Measurement of swallowing using flexible polymer sensor

We proposed a new method to measure swallowing in this study. A flexible polymer sensor was used to measure human swallowing. Electromyogram (EMG) of suprahyoid muscles were measured as a reference of swallowing. We also developed a measurement system for the flexible polymer sensor, which consists of two measurement circuits; the 1st one measures the voltage of flexible polymer sensor, and the 2nd one EMG of suprahyoid muscles. We conducted measurement experiments focused on human swallowing to confirm the ability of this sensor. At the experiment one subject was asked to sit in three different postures and to drink a cup of water. Results show that human swallowing can be detected by this flexible polymer sensor.

Signal source estimation inside the human heart during ventricular activation using switching voltage divider

A novel signal source estimation method using switching voltage divider technology was developed in our previous works. The aim of this method is to reduce the number of electrodes required for signal source estimation. Using this method, voltage and position information about the signal source inside the human body can be obtained simultaneously. The purpose of this paper is to estimate the changes in the signal source location according to ventricular activation. One healthy male (31 years old) participated in an ECG measurement experiment that utilized switching voltage divider technology. Nine signal electrodes and one ground electrode were attached to the participants body surface, and the electrocardiogram was measured with the patient seated. The signal sources for early QRS, mid QRS, and late QRS, were estimated. Results suggest that changes in the signal source location could be estimated during ventricular activation.