Shinji Gotoh

Development of a non-contact screening system for rapid medical inspection at a quarantine depot using a laser Doppler blood-flow meter, microwave radar and infrared thermography.

In order to conduct fast screening of passengers with infections such as severe acute respiratory syndrome (SARS) or pandemic influenza at a quarantine depot, we developed a non-contact screening system with a self-produced program to conduct a human screening within five seconds, via a linear discriminant function from non-contact derived variables, i.e. palmer pulse derived from a laser Doppler blood-flow meter, respiration rate determined by a 10-GHz microwave radar, and facial temperature measured by a thermography. The system evaluation was conducted on seven healthy male subjects (23 ± 1 years). In order to achieve a pseudo-infection condition, the subjects maintained an ergo-meter exercise load (100 W, 10 minutes). Before (normal condition) and after (pseudo-infection condition) exercise, a significant linear discriminant function (p < 0.001) was determined to distinguish the pseudo-infection condition from the normal condition (Mahalanobis D-square = 20.3, classification error rate <5%). The proposed system appears promising for future application in fast screening of infection at a quarantine depot.

A novel apparatus for non-contact measurement of heart rate variability: a system to prevent secondary exposure of medical personnel to toxic materials under biochemical hazard conditions, in monitoring sepsis or in predicting multiple organ dysfunction syndrome.

Abstract Background. The impaired balance of the low-frequency/high-frequency ratio obtained from spectral components of RR intervals can be a diagnostic test for sepsis. In addition, it is known that a reduction of heart rate variability (HRV) is useful in identifying septic patients at risk of the development of multiple organ dysfunction syndrome (MODS). We have reported a non-contact method using a microwave radar to monitor the heart and respiratory rates of a healthy person placed inside an isolator or of experimental animals exposed to toxic materials. Apparatus design and testing. With the purpose of preventing secondary exposure of medical personnel to toxic materials under biochemical hazard conditions, we designed a novel apparatus for non-contact measurement of HRV using a 1215 MHz microwave radar, a high-pass filter, and a personal computer. The microwave radar monitors only the small reflected waves from the subjects chest wall, which are modulated by the cardiac and respiratory motion. The high-pass filter enhances the cardiac signal and attenuates the respiratory signal. In a human trial, RR intervals derived from the non-contact apparatus significantly correlated with those derived from ECG (r=0.98, P<0.0001). The non-contact apparatus showed a similar power spectrum of RR intervals to that of ECG. Conclusions. Our non-contact HRV measurement apparatus appears promising for future pre-hospital monitoring of septic patients or for predicting MODS patients, inside isolators or in the field for mass casualties under biochemical hazard circumstances.

Development of Non-contact Monitoring System of Heart Rate Variability (HRV) - An Approach of Remote Sensing for Ubiquitous Technology -

The aim of this study was to develop a prototype system to monitor cardiac activity using microwave Doppler radar (24.05 GHz frequency, 7 mW output power in average) without making contact with the body and without removing clothing; namely, a completely noncontact, remote monitoring system. In addition, heart rate and changes in heart rate variability (HRV) during simple mental arithmetic and computer input tasks were observed with the prototype system. The experiment was conducted with seven subjects (23.00 ± 0.82 years old). We found that the prototype system captured heart rate and HRV precisely. The strong relationship between the heart rates during tasks (r = 0.963), LF (cross-correlation = 0.76) and LF/HF (cross-correlation = 0.73) of HRV calculated from the microwave radar data and from electrocardiograph (ECG) measurements were confirmed.

Development of a noncontact and long-term respiration monitoring system using microwave radar for hibernating black bear.

The aim of this study is to develop a prototype system for noncontact, noninvasive and unconstrained vital sign monitoring using microwave radar and to use the system to measure the respiratory rate of a Japanese black bear (Ursus thibetanus japonicus) during hibernation for ensuring the bears safety. Ueno Zoological Gardens in Tokyo planned to help the Japanese black bear (female, approximately 2 years of age) going into hibernation. The prototype system has a microwave Doppler radar antenna (10-GHz frequency, approximately 7 mW output power) for measuring motion of the body surface caused by respiratory activity without making contact with the body. Monitoring using this system was conducted from December 2006 to April 2007. As a result, from December 18, 2006, to March 17, 2007, similar behaviors reported by earlier studies were observed, such as sleeping with curled up posture and not eating, urinating or defecating. During this hibernation period and also around the time of hibernation, the prototype system continuously measured cyclic oscillations. The presence of cyclic vibrations at 8-sec intervals (about 7 bpm) was confirmed by the system before she entered hibernation on December 3, 2006. The respiratory rate gradually decreased, and during the hibernation period the respiratory rate was extremely low at approximately 2 bpm with almost no change. The results show that motion on the body surface caused by respiratory activity can be measured without touching the animals body. Thus, the microwave radar employed here can be utilized as an aid in observing vital signs of animals.

Development of a Stand-Alone Physiological Monitoring System for Noncontact Heart and Respiration Rate Measurements on Real-Time Linux Platform

We developed a stand-alone physiological monitoring system without any constraints on its users for daily life healthcare. The system measures tiny movements on a body surface induced by heartbeat and respiration in a noncontact manner using a 24-GHz microwave radar. To extract the related signals from the radar output, an analog band pass filter was designed and integrated into a printed circuit board. The software was developed on an embedded Linux platform for a stand-alone and modular design. To assess the performance of noncontact physiological monitoring, we conducted a laboratory test on eight healthy male subjects (ages: 22.0 ± 1.25 years). The heart and respiration rates determined by the proposed system correlated significantly with those measured by the contact-type electrocardiogram (r = 0.83, p < 0.01) and respiratory effort belt (r = 0.90, p < 0.01). The results showed that the respiration and heartbeat were accurately detected by the proposed system, which appears promising for monitoring physiological condition in daily life.

A novel stress monitoring method through stress-induced respiratory alterations: non-contact measurement of respiratory V(T)/T(I) alterations induced by stressful sound using a 10 GHz microwave radar.

We have developed a non-contact stress monitoring system which measures respiratory V(T)/T(I) (tidal volume/inspiration time) alterations using a 10 GHz microwave radar. The measurable distance of the system is 50 cm, which is 10 times longer than our previously developed stress monitoring system which measures heart rate variability using a 24-GHz microwave-radar. The study was conducted with eight subjects (23 ± 1years old) to evaluate the efficacy of the system. An audio stimulus at 95 dB sound pressure level was presented to the subjects following a silent period of 120 seconds. During the silent period, V(T)/T(I) averaged 826 ± 384 ml s−1, while it increased significantly (p < 0.05) with an average of 1227 ± 704 ml s−1 during audio stimulus low frequency component (LF)/high frequency component (HF), which reflects sympatho-vagal valance, showed a peak during audio stimuli. This paper aims to study the efficacy of the non-contact stress monitoring system for its future applications in many fields including health and safety.

The Development of a Dual-Radar System with Automatic Hypopnea Threshold Optimization for Contact-Free Sleep Apnea-Hypopnea Syndrome Screening

Full-night polysomnography (PSG) examination is regarded as the gold standard for the diagnosis of sleep apnea-hypopnea syndrome (SAHS). However, PSG requires the placement of multiple sensors on the head, face, and chest, which can impose a heavy strain on patients. Therefore, in the present study, we aimed to develop a contact-free, stand-alone SAHS screening system that eliminates body movement artifacts based on automatic optimization of the hypopnea threshold. Doppler radar sensors were placed beneath a mattress. In order to achieve high sensitivity and specificity, the hypopnea was based on the average amplitude of respiration during the full sleep period. The threshold was determined via receiver operating characteristic (ROC) analysis using PSG as a reference. We conducted full-night clinical tests of the proposed system in 27 patients with suspected SAHS (49 ± 12 years) at Tomei Atsugi Hospital. When predicting the severity of SAHS with an apnea-hypopnea index (AHI) of >30/h using PSG as a reference, the proposed system achieved a sensitivity of 100% and a specificity of 100%. These results represent a drastic improvement over those of our previous study (sensitivity: 90%; specificity: 79%).

Development of an Array Antenna Landmine Detection Radar System

We have developed an anti-personnel landmine detection radar system which uses an impulse signal of pulse-width 150 ps. We were able to reduce detection time by using an array of wideband spiral antennas of diameter 9 cm, with five transmitter antennas facing six receiver antennas. The resulting device is able to detect landmines in a 50 × 50 cm area in approximately two minutes. We were also able to produce an accurate image of the shape of the underground target by applying super-resolution signal processing (MUSIC processing) to the pulse signal.