Yosuke Kurihara

Accelerometry-Based Gait Analysis and Its Application to Parkinson's Disease Assessment— Part 1: Detection of Stride Event

Gait analysis is widely recognized as a promising tool for obtaining objective information on the walking behavior of Parkinsons disease (PD) patients. It is especially useful in clinical practices if gait properties can be captured with minimal instrumentation that does not interfere with the subjects usual behavioral pattern under ambulatory conditions. In this study, we propose a new gait analysis system based on a trunk-mounted acceleration sensor and automatic gait detection algorithm. The algorithm identifies the acceleration signal with high intensity, periodicity, and biphasicity as a possible gait sequence, from which gait peaks due to stride events are extracted by utilizing the cross-correlation and anisotropy properties of the signal. A total of 11 healthy subjects and 12 PD patients were tested to evaluate the performance of the algorithm. The result indicates that gait peaks can be detected with an accuracy of more than 94%. The proposed method may serve as a practical component in the accelerometry-based assessment of daily gait characteristics.

Measurement of Angular Motion in Golf Swing by a Local Sensor at the Grip End of a Golf Club

This paper describes a novel method for measuring golf swing angular motion in a global coordinate system using the 3-D acceleration and angular velocity detected by a local motion sensor set at the grip end of a golf club. Optical direct linear transformation (DLT) is the conventional method for measuring sports motion; however, accurate localization of global coordinates and precise setting of infrared high-speed cameras in the test field are essential. Furthermore, infrared reflectors must be attached to the moving object. The system itself and the fine-tuning are expensive, but an accurately set system can provide precise positions for the moving reflectors. It is effective for measuring translational motion but not angular motion that is based on the principles of measurement. The alternative method that is proposed here is easier in terms of setting and fine-tuning, more reasonable in cost, and more accurate in measuring rotational motion compared with the DLT method. Furthermore, the systems wireless transmitter enables noninvasive measurement. When addressing the golf club, its initial angles and posture matrix are calculated using the 3-D acceleration; when the swing begins, the motion sensor measures the changing angular velocity and the acceleration. The application of step-by-step Euler transformation for each sampling interval yields the angular velocity and angle in the global coordinate system. The mean RMSE of ten trials with five subjects was 3.06°, 26.64°, and 4.43° for the 3-D angle of the club shaft.

NIRS-Based Language Learning BCI System

This paper describes a non-invasive, less restrictive, stable measurement system for a brain-computer interface (BCI) for second-language (L2) learning. The system outputs the arousal of the Yerkes-Dodson law. We employ non-invasive near-infrared spectroscopy (NIRS) as a basic device to measure the blood volume. However, the blood volume measured by NIRS includes base-line drift and is not stable. Here, we introduce a new drift-free variable defined as blood flow, which is the time derivative of the blood volume. Problems to be considered are: 1) Can the blood flow represent brain activity? 2) Where are the fewest brain areas strongly influenced by the language listening? 3) What parameter expresses arousal? We also present a measurement system. To verify the system, we carried out experiments with 40 listeners (10 advanced, 15 intermediate, and 15 novice listeners). When advanced L2 listeners were listening to the first and second languages, the distribution patterns of the root mean squares of the blood flow in the prefrontal regions were close to the correlation coefficient of 0.89, which shows that blood flow can represent brain activity in language processing. The center of BA10 and the right and left BA46 in the prefrontal regions were sufficient to detect language processing. The root mean squares of the differences of the left and right BA46 from BA10 peaked at a certain L2 readability level for all L2 listeners; they can be the parameter that expresses arousal. Thus, the measurement system can function as an input measurement device for BCI.

A noninvasive heartbeat, respiration, and body movement monitoring system for neonates

Long-term monitoring of heart rate, respiratory rate, and body movement in neonates would be useful for preventing illnesses, such as respiratory disorders. However, currently, there is no noninvasive monitoring system available for neonates. Therefore, in this study, we proposed a modified, noninvasive, piezoceramic-facilitated biometric system to allow measurements of heart rate, respiratory rate, and body movement of neonates. We designed a monitoring system for neonates based on a sensor device with four piezoceramics, which were placed beneath the four legs of a neonatal bed. The output signal from the sensor device was measured as overlaps of the heartbeat, respiration, and body movement components. To test our system, we studied a 7-week-old male preterm infant who was admitted to the neonatal intensive care unit. To determine the validity of our system, electrocardiogram and respiratory waveform output from a conventional bedside monitor were used as references. We observed that the heartbeat signal that was detected by a piezoceramic sensor and that by ECG was similar. Similar findings were also observed between the respiration signal detected by a piezoceramic sensor and the reference respiration signal. In our method, the heartbeat and respiration signals could be accurately measured in the segments in which no body movement was generated. Use of piezoceramics avoids the need for applying sensors to the neonatal body. Our proposed monitoring method would be useful for neonates who require long-term monitoring in the hospital and after discharge, as well as for research purposes.

Development of vibration sensing system with wide dynamic range: monitoring of scratching and turning-over motions during sleep

This paper describes a novel vibration sensing system with wide dynamic range for measuring “scratching”, “turning over” and “sitting up/lying down” motions in an unconstrained manner while the patient is sleeping. The sensing device used in the proposed system is composed of a piezoceramic sensor sandwiched between two metal plates. Under the system’s configuration, each piezoceramic sensor generates a measurable output voltage proportional to the wide-ranging amplitude of vibrations produced by “scratching”, “turning over” and “sitting up/lying down” motions. Furthermore, in order to detect the direction of “turning over” and “sitting up/lying down” motions, we defined two indices that could be calculated based on three output signals from the piezoceramic sensors placed under three legs of the bed. A validity experiment was carried out for comparison with a conventional sensing method for measuring “scratching”, “turning over” and “sitting up/lying down” motions. The results showed that the proposed vibration sensing system is valid in terms of accuracy without the need for attaching sensors to the patient’s body.

Biosignals Sensing by Novel Use of Bidirectional Microphones in a Mobile Phone for Ubiquitous Healthcare Monitoring

This paper describes a novel application of the bidirectional audio microphones in mobile phones to measure biosignals for ubiquitous health monitoring. The bidirectional microphone has two pressure-detecting ports. A pressure-detecting film receives the differential pressure between the ports. We apply this idea to biosignal measurements for a mobile phone. We used the microphone as 1) a sphygmograph at the fingertip, 2) a stethoscope in which a delay time sensor of pulse wave arrivals from the neck near the carotid or chest near the heart to the fingertip, and 3) a bed sensing device for biosignals. When used as a sphygmograph, it detects the wave similar to the second derivative of the conventional optical pulse oxymeter output wave. When used as a stethoscope, it detects cardiac sound and the pulse wave and respiration. With two microphones, the delay time from the neck carotid to the fingertip is detected.

Development of a Non-Contact Sensing Method for Scratching Activity Measurement

The severity of skin diseases accompanied by itch is related to the frequency of itching; thus, the ratio of total scratching time to total measurement time (TST [%]) is a useful index for diagnosing skin diseases such as atopic dermatitis. To grasp the trend of the patients TST [%], daily monitoring of scratching motion is effective, but it is important to carry out the measurements under unconstrained conditions so as not to burden the patient. In this paper, we propose a non-wearing sensing method for measuring scratching motions while the patient is sleeping. The sensing device used in the proposed method is composed of a piezoceramic sensor sandwiched between two metal plates and placed under the legs of the bed. This sensing device is able to measure micro-vibrations produced by the scratching motion. In carrying out the validation experiment, the TST [%] is obtained using the proposed sensing device. The results are then compared with the TST [%] obtained from conventional, more constrained measurement methods, such as electromyography, ceramic sheets, microphones, strain gauges, acceleration sensors, and gyro sensors. Therefore, the sensing device positioned near the subjects head, where the scratching points are closer together, is capable of determining the TST [%] at an accuracy nearly equal to that of the conventional method that shows the highest accuracy TST [%] among all conventional sensors.

Room Ventilation Control by a Self-Sensing Fan

This paper describes a scheme for room ventilation control using a self-sensing actuator in a time-sharing manner. Electromagnetic motors and piezoelectric actuators contain internal feedback. Electromagnetic motors function as electromagnetic generators and piezoelectric actuators generate a voltage when a force is applied to them. These characteristics are referred to as reversibility. We consider the automatic control of an air ventilation system for an airtight house. We found that an aeration fan functioned as a fine-gauge pressure sensor. When there is a pressure difference between the inside and the outside of the room owing to exhaust, the unused aeration fan rotates as a windmill and an induction motor generates a voltage. The control scheme is as follows. When the voltage from the aeration fan, which is at a standstill, exceeds a threshold value, the aeration fan begins to rotate as a fan for a certain period and then returns to the standstill mode to monitor the pressure. These operations are continued in turn. An aeration fan with a diameter of 0.1 m acts as a gauge pressure sensor at pressures exceeding 2.5 Pa with linearity and a cut-off frequency 0.1 Hz. The controller, which turns the aeration fan ON when the pressure exceeds 3 Pa for 10 s and returns it to the standstill mode, worked well in an actual airtight room.

Monitoring system to detect fall/non-fall event utilizing frequency feature from a microwave Doppler sensor: validation of relationship between the number of template datasets and classification performance

A fall event is a serious issue for the elderly because it may cause critical aftereffects. To reduce the risk of these aftereffects, early detection of the fall event is essential. However, it is difficult for caregivers to detect fall events early themselves, because they are required to constantly monitor the elderly to confirm their safety. Therefore, an automatic monitoring system which could detect fall events early is helpful in the healthcare field. We have proposed a fall event detection system utilizing a microwave Doppler sensor. The frequency feature is calculated, and compared with known fall or non-fall event data. However, for real-time detection, the number of template datasets must be as low as possible while maintaining high performance of the classification. In this paper, we attempt to identify the relationship between the number of template datasets and the performance of the proposed system.

A development of system monitors adl by microwave Doppler sensor-classification of presence/absence system incorporating respirational signals

Aging is a serious issue in our global society. Additionally, a smaller working population increases the burden on nurses and other healthcare professionals. To reduce the monitoring burden on nursing, a system that enables quantitative monitoring of the elderly automatically in their home is very desirable. In this paper, we propose a novel system to classify the presence of a person within a designated area using a single microwave Doppler sensor. The proposed system utilizes the respirational signal observed from the sensor and classifies it using a support vector machine. The system was evaluated using 21 subjects and performed as accurately as 99.68%.