Masaki Kyoso

Application of Near-field intra-body communication and spread spectrum technique to vital-sign monitor

As a novel vital sign monitor, we have developed wireless ECG monitoring system with Near-field intra-body communication technique. However, communication reliability is not so high because transmission channel is noisy and unstable. In order to improve the problem, we utilize spread spectrum (SS), which is known as robust communication technique even through poor transmission channel. First of all, we evaluated characteristics of human body to SS signal. The results show that SS can be used even through human body. Based on this result, we developed and tested near-field intra-body communication device enhanced by SS. The test result shows that SS can solve the problem mentioned above.

Individual identification with high frequency ECG : Preprocessing and classification by neural network

In this research, we proposed that high frequency component of HFECG was applicable biometric feature for new identification system. We developed identification method by using neural network (NN), and aimed at the improvement of the classification rate. Preprocessing prior to NN is performed by justification on time axis and normalization on amplitude. As a result, an average of 99% classification rate was obtained from 9 subjects. We also made an attempt to identify in shorter time by shifting of the HFECG by a few samples to NN.

Improvement of temporal resolution in blood concentration imaging using NIR speckle patterns

In the imaging of blood concentration change using near infrared bio-speckles, temporal averaging of speckle images is necessary for speckle reduction. To improve the temporal resolution in blood concentration imaging, use of spatial averaging is investigated to measured data in rat experiments. Results show that three frames in temporal averaging with (2×2) pixels in spatial averaging can be accepted to obtain the temporal resolution of ten concentration images per second.

Application of near-field intra-body communication and spread spectrum technique to vital-sign monitor evaluation of error rate in ambulatory status

As a novel vital sign monitor, we have developed wireless ECG monitoring system with Near-field intra-body communication (NF-IBC) technique. However, it was hard to ensure communication reliability because transmission channel is noisy and unstable. In order to improve the problem, we utilize spread spectrum (SS), which is known as robust communication technique even through poor transmission channel. In previous study, we have already developed an ECG monitor using NF-IBC enhanced by SS. In this paper, we evaluated bit error rate (BER) of the system devices in ambulatory status of the user such like walking. The test result shows that communication reliability depends on walking speed. However, it was found that reliability was high enough for practical use. These results indicated that the wireless monitor based on SS NF-IBC was applicable to unrestrained vital-sign monitor.

A study on reception electrodes for the vital-sign monitor using near-field intra-body communication enhanced by spread spectrum technique

As a novel vital sign monitor, we have developed wireless ECG monitoring system with Near-field intra-body communication (NF-IBC) technique. However, it was hard to ensure communication reliability because transmission channel is noisy and unstable. In order to solve the problem, we utilize spread spectrum (SS), which is known as robust communication technique even through poor transmission channel. In previous study, we have already developed an ECG monitor using NF-IBC enhanced by SS. In this paper, we evaluated on structure of the reception electrode for reliable communication. Based on the evaluations with bit error rate, we suggested the reception electrode structure which can keep the communication reliability. As the results we considered that we can expand the reception electrode up to 2.25m2. Moreover, we proposed the structure of the reception electrodes that can keep the communication reliability. Finally we suggested how to use the SS NF-IBC vital-sign monitor in room that larger than 2.25m2, and we had shown the practicability of the systems.

Dynamic Electrical Characteristics of the Muscle with the Fatigue during Exercise

Although there is an invasive method, the procedure to quantitate the muscle fatigue today is not fully established. This study analyzes the muscle fatigue by measuring cross electric property of the muscle with working load noninvasively. We measured the electrical impedance of the muscle to obtain the relationship between the electrical property and the fatigue during exercise. Several Ag/AgCl electrodes are placed the biceps brachii muscle crossing the arm. The baseline drift due to the sweat glands on the skin was effectively eliminated by subtracting one of the exercised arm from one of the resting arm, and the interelectrode impedance was measured. The fatigue of the arm was loaded by flexing exercise with a 2 kg iron array. The rate of flexing was once per second. The impedance was acquired every 30 seconds. The flexing was constant but ceased while acquiring the impedance value for 5 seconds. As a result impedance increased at the beginning, and then decreased after 90 seconds, or started decreasing after the beginning of the exercise. These phenomena were well reproducible. The initial increase of the impedance was concluded as with the fatigue which may triggered the increase of the lactic acid in the muscle. The decrease of the impedance in the latter part was probably due to the influence of increased blood flow, which was simultaneously measured in this study.

Estimation of individual response in finger blood concentration change under occlusion on human arm using speckle patterns

We have developed the method for imaging blood flow and blood concentration change by using laser speckle in fiber illumination. We experimentally discuss the relationship of blood occlusion condition and individual response of blood concentration change measured by the method.

Biometric identification with high frequency electrocardiogram: Unregistered user refusal method and performance evaluation

As a new modality for biometric identification, electrocardiogram-based identification technique has been developed. We proposed a technique with high frequency component of electrocardiogram (HFECG) in QRS segment. In this report, an unregistered user refusal algorithm was combined with the artificial neural network based waveform classifier. The refusal function was realized by simple thresholding technique. HFECGs from twenty collaborators were used for supervised learning. Twenty HFECGs from the same collaborators were tested and false acceptance rate (FAR) and false rejection rate (FRR) were evaluated. Ten HFECGs from other collaborators were also tested to find unregistered user refusal performance. The results show that FAR and FRR in the registrants can be kept within 1%, however, unregistered user refusal performance was not acceptable under the same condition.

An implantable neural activity monitor with nonlinear gain-controlled amplifier

An implantable neural spike monitor with nonlinear amplifier was proposed for robust measurement against noise. In embedded electrophysiological signal processing systems, detection performance depends on signal to noise ratio (SNR), however, it is getting worth after implantation because of neoformation surrounding the electrodes and so on. We proposed a spike enhancer in this study. It has two remarkable function; automatic gain optimization with feedback loop and SNR improvement by nonlinear amplifier. In this report, the system performance was evaluated without feedback loop. A prototype circuit is prepared with small number of parts and tested on input-output characteristics. For the final evaluation, neural spike signal from somatosensory cortex of a rat was applied to the circuit. The test results show that system can expand SNR on neural spike signal from rat. It indicates that the spike enhancer can improve total performance of neural activity processing system.