Shigeyoshi Nakajima

Clinical tests and evaluations of a Wireless ECG sensor for realization of ubiquitous health care systems

This paper introduces the concept of an online medical diagnosis system for ubiquitous health care using a wireless ECG sensor. To confirm the feasibility ofthe system, we conducted clinical tests by 67 subjects with a wireless ECG sensor and a Holter ECG monitor simultaneously for comparison purpose. We made five types of evaluations such as analyses on data loss rate, burst data loss length, ECG waveforms comparison, normalized cross-correlation and heart rate variability (HRV) by RR50. The results show that, as long as the sensed data are successfully received at a receiver, the wireless ECG sensor has a comparable performance with the Holter ECG monitor.

Continuous ECG data gathering by a wireless vital sensor — Evaluation of its sensing and transmission capabilities

This paper investigates the possibility of a realtime electrocardiogram (ECG) data gathering by a wireless vital sensor in houses and hospitals. First of all, to evaluate the ECG capability, we conducted clinical tests with 67 subjects comparing 24-hour data obtained at houses between the wireless vital sensor and a Holter monitor. Secondly, to evaluate the wireless transmission capability, we conducted experiments with 8 subjects in patient rooms at a hospital. The clinical test results conclude that, as long as the sensed data are successfully received at a receiver, the wireless vital sensor has a comparable performance with the Holter ECG monitor, on the other hand, the experimental results show that the data transmission capability with a single receiver is not satisfactory for real-time continuous monitoring, but the use of three receivers can significantly improve the data transmission quality by receive diversity effect.

A receiver diversity technique for ensuring high reliability of wireless vital data gathering in hospital rooms

Sensing and wireless technologies have made remarkable advance recently, so wireless vital sensors for medical use, which are light-weight but accurate, have been commercially available. However, because of the low reliability of the wireless data transmission, sensed vital data are often lost in the wireless channel and this is a fatal drawback of the devices for continuous monitoring of patients in hospitals. This paper investigates the effect of using multiple receivers (receiver diversity technique) on the improvement of data loss rate for wireless vital data gathering. Experiments with a wireless vital sensor in hospital rooms reveal that putting receivers to higher positions such as ceiling is advantageous and the use of three receivers can sufficiently improve the data loss rate as compared with the use of a single receiver.

Estimation of Human Movements from Body Acceleration Monitoring Using One Nearest Neighbor Method - Ubiquitous Health Care

We are developing an ubiquitous system for constant monitoring of human health that uses a 3D accelerometer and an electrocardiogram communicating wirelessly to a personal computer. The should provide an automatic alert whenever a person’s condition indicates a risk of heart attack or other danger. We collected acceleration data and bodily movement records from our staffs and from volunteer in order to determine from the movement data what sorts of movements, such as walking or riding a bicycle, a person is engaging in. Our system is able to infer the type of human movements from the acceleration data and use this in combination with ECG data to decide whether to issue an alert. Recently, we used a threshold method for the estimating what types of movements were being detected. Then we recently improved on our movement estimates by using normalization and the one nearest neighbor method.

Three-dimensional motion analysis and structure recovering by multistage Hough transform

A new approach for the detection of motion of three-dimensional rigid bodies from two- dimensional images is presented. The approach is based on two main stages. In the first stage, the positions and velocities of feature points are detected from two-dimensional images. In the second stage, the rotation and the translation velocity of each body is detected from the positions and velocities of the set of feature points. We employ the Hough transform method in both stages. We describe the details of the second stage and the method of computation reduction in Hough transform. The effectiveness of our method is confirmed through computer experiment.

Measurement of a Translation and a Rotation of a Tooth after an Orthodontic Treatment Using GA

The purpose of our study is measurement of the value of the translation and the rotation between the corresponding teeth of digital dental models before and after an orthodontic treatment. We used digital models from plaster models digitized by 3D scanner, and divide the polygons into several teeth using our original GUI. We measured the distance from a polygon in the jaw before the treatment to the nearest polygon in the after jaw and consider the distance as a fitness value. We got the best motion (translation and rotation) parameters using GA and reported them as the measurement of the tooth motion after the treatment. And we checked the accuracy of the result

Development of a triage engine enabling behavior recognition and lethal arrhythmia detection for remote health care system

For ubiquitous health care systems which continuously monitor a persons vital signs such as electrocardiogram (ECG), body surface temperature and three-dimensional (3D) acceleration by wireless, it is important to accurately detect the occurrence of an abnormal event in the data and immediately inform a medical doctor of its detail. In this paper, we introduce a remote health care system, which is composed of a wireless vital sensor, multiple receivers and a triage engine installed in a desktop personal computer (PC). The middleware installed in the receiver, which was developed in C++, supports reliable data handling of vital data to the ethernet port. On the other hand, the human interface of the triage engine, which was developed in JAVA, shows graphics on his/her ECG data, 3D acceleration data, body surface temperature data and behavior status in the display of the desktop PC and sends an urgent e-mail containing the display data to a pre-registered medical doctor when it detects the occurrence of an abnormal event. In the triage engine, the lethal arrhythmia detection algorithm based on short time Fourier transform (STFT) analysis can achieve 100 % sensitivity and 99.99 % specificity, and the behavior recognition algorithm based on the combination of the nearest neighbor method and the Naive Bayes method can achieve more than 71 % classification accuracy.

Evaluation of a wireless vital sensor for ubiquitous health monitoring systems

Vital sensor and wireless information communication technologies play important roles in providing continuous health monitoring systems. The key elements required for the vital sensor device are its simplicity and accuracy, whereas those for the wireless communication tool are its connectivity and comfortability. For a commercially available wireless vital sensor with capability of measuring three-dimensional acceleration, electrocardiogram and body surface temperature, we conducted a clinical test for evaluating its accuracy and connectivity. The result of the clinical test revealed that the accuracy of the vital sensor was almost the same as that of the Holter monitor in term of electrocardiogram recording capability, but its wireless connectivity was much lower, that is, the average data loss rate was 0.22 for the data from all the subjects with variance of 0.025. In addition to the clinical test, we conducted an experiment on improving the wireless connectivity by receiver diversity in a patient room. The experimental result revealed that the average data loss rate, which was 0.041 for the use of a single receiver, was effectively reduced to 0.0023 only for the use of two antenna receivers.

Collision Detection of 4-legged Robots Using Acceleration Sensors

Institute of Laser Engineering, Osaka University, launches FIREX (Fast ignition Realization Experiment) project to demonstrate the fast-ignition scheme. For achieving high-gain with the fast ignition scheme, fuel plasma must be heated locally. In this paper, advanced penumbral imaging technique has been proposed to obtain a two-dimensional image of hard x-rays and/or neutrons from nuclear reaction region for identifying locality of the heated region. Neutron yield predicted for FIREX project is not high enough to obtain sufficient neutron image with the conventional penumbral imaging. Uniformly redundant array (URA) of penumbral aperture is used to increase image intensity. In addition to the URA, a heuristic method was applied to image reconstruction procedure for reducing image distortion. The proposed technique was used to image x-ray from laser-irradiated targets. The proposed method was demonstrated in the experiment.

A Method of Calculating Image Saliency and of Optimizing Efficient Distribution of ImageWindows

In this paper we propose a method of calculating the saliency map of an input image. In this method the saliency gets higher in the areas where the image features are different than those in the surrounding areas and where the features are unfamiliar. Based on this method, we also propose a method to apply the idea of calculating the saliency to the problem of determining the most efficient distribution of image windows to acquire the information. This distribution might be considered to correspond to the distribution of attention. We conducted two experiments. The first is the experiment to apply the saliency model to a moving image and shows that in the area where the feature about motion is different than those in other areas the saliency gets higher. In the second experiment it is shown that a definite number of image windows to acquire the information can be efficiently distributed owing to the local image features