Chronic and age-related diseases are posing great challenges on the present healthcare system in the developed and developing countries. To lower the cost and improve the efficiency and quality of the current healthcare delivery, health informatics has emerged as a new field of study that is anticipated to transform the current hospital-centered medical system into a p-Health or 6-P's health model. One of the technological challenges in developing p-health system is to advance innovative sensing technologies for the acquisition of multi-scale and multimodal health information. In this review, we mainly focus on the two types of sensing technologies, i.e., biosensing and wearable sensing, to acquire a multi-scale set of health information from the genetic and molecular level to the body system level. Firstly, we address the current state of point-of-care bio-sensing technology for rapid and high-sensitivity biomarker detection. Some critical challenges and enabling technologies such as microfluidic technology for sample processing and nanotechnology for high-sensitivity detection will be discussed. Then the state-of-the-art of wearable sensing systems which aim to provide continuous physiological monitoring and long-term tracking of the chronic diseases will be presented. Major challenges in the development of wearable sensing systems including continuous and noninvasive sensing, motion artifacts cancellation, and the low power, low frequency and low noise integrated circuit design will be discussed. These sensing technology advancements are essential to the realization of the future p-Health model.
This study was performed to examine the effects of weekly exercise in subjects classified as support_1 according to the Japanese health care insurance system. We evaluated the ability of eight elderly subjects to walk using wireless inertia sensors with an embedded triaxial accelerometer and angular velocity sensor. The subjects participated in training once a week and were evaluated once a month over a study period of 3 months. Wearable motion sensors were attached to the lower back and both thighs of each subject. The subjects performed high-performance walking over a distance of 10 m. The speed, cadence, gait cycle, thigh pitch angle, and autocorrelation function on the lower back were determined. The subjects attained high-performance walking sooner after 3 months. Although most of the subjects showed an improvement in walking ability, there were no significant improvements in the cadence gait cycle or autocorrelation function. Exercise once a week can significantly improve the ability of elderly subjects to walk. Thus, home exercise is recommended to improve walking ability in the elderly.
Current imaging technologies such as magnetic resonance imaging (MRI). X-ray computed tomography (X-ray CT), and positron emission tomography (PET) are utilized in the medical field. Moreover, a new imaging technology called magnetic particle imaging (MPI) has been proposed, and has attracted attention. This technology can image a distribution of internally administered magnetic nanoparticles (MNPs). In MPI, since a signal generated from MNPs is detected directly, high sensitivity and high spatial resolution are expected compared to MRI that uses the same MNPs as a medical contract media. In this method, a magnetization response from MNPs from a target region is detected by scanning a local distribution of magnetic field. However, the image blurring and artifacts appear due to the interference of magnetization response generated from the MNPs outside target region, so that image resolution is degraded. We have already proposed a new image reconstruction method that focused on the difference between the waveform of electromotive force generated from a target region and outside region. In this paper, we verified the validity of this proposed method by using the prototype system and numerical experiment considering the prototype system's specifications. As a result, the image artifacts were suppressed, and the image resolution was about 10.3 mm in numerical experiment. We also indicated that the image artifacts were decreased by 32% compared with conventional method in the experiment with the prototype system. However, since the image resolution was about 12 mm in this experiment, it needed to be more improved.
The present study aimed to develop an effective method for detecting the symptoms of accumulated fatigue in order to select candidates for interview guidance as a measure to prevent health impairments due to overwork. We created a simple system by which non-experts can quickly and independently detect signs of accumulated fatigue, including subjective indices, work-related strain, task performance and physiological indices (stabilometry, autonomic nervous system indicators obtained from electrocardiogram and plethysmogram). Four university students who were busy with their undergraduate theses were asked to use the system. They used the system by themselves 16 to 21 times in a two-month period. Participants took measurements on the days when they were busy completing graduation theses and preparing for research presentations, indicating that the measurement system was easy to use. We then investigated a method for detecting signs of accumulated fatigue based on the measurement data. First, we established thresholds based on the standard deviations for each measurement. The days when a number of measurements exceeded thresholds were considered the days when signs of accumulated fatigue were detected. Symptoms were detected in all the participants on the day before or the day of graduation research oral presentation rehearsal. There was also a correspondence between days when signs were detected and events causing accumulated fatigue, indicating the validity of the present method. In order to develop a system for detecting signs of accumulated fatigue that incorporates the present method and to elicit routine use, further simplification of the measurement methods are required, and techniques for motivating users are necessary.
In this study, we developed a point-contact force sensor, and this sensor was used to develop a measurement system that was shaped in the form of a feeding bottle. Unlike in a cantilever force sensor, in the proposed force sensor, the point of force measurement does not move. Thus, the force sensor can measure a force at a specified point. The force sensor consists of a pressure transducer and a steel ball with a diameter of 3 mm. Any force applied to the artificial nipple is transmitted to the pressure transducer, which is in point contact with the steel ball. The force sensor is linear up to a load of 3.92 N, has a hysteresis of 1%, and has a response time of 4 ms. The force is measured at distances of 8 mm (channel 1) and 14 mm (channel 2) from the tip of the nipple. In the measurement system, the sensor signals are converted (A/D) at a sampling rate of 100 Hz and a quantization resolution of 10 bits. After the A/D conversion, the force signals are transferred to a data indicator and a data logger for real-time display on an LCD and for storage ona micro SD card, respectively. Using this system, we performed measurements on four infants. A signal peak was observed from channel 2 and then from channel 1. This result could be attributable to the peristaltic movements of the infant's tongue. The same result was observed for all subjects. These results indicate that the proposed system can be used to measure any force that is applied to an artificial nipple. Moreover, the mother of a subject also performed measurements using the system. This confirmed that the system was easy to operate and that measurements could be performed in a normal feeding posture.
In order to determine the cause of pump-tube damage during cardiac surgery, periodic-stress-induced morphological change in the inside surface of a polyvinyl chloride (PVC) pump tube was observed by atomic force microscopy. Numerous polygonal lamellae several micrometers in size were found to spread over the inside surface of the PVC pump tube before deformation. The number of lamellae decreased after deformation of the pump tube. It was confirmed by transmission electron microscopy that the lamellae are single crystals. The results of an energy dispersive X-ray spectrometry analysis further show that the lamellae are composed of aluminum (Al), silicon (Si), and oxygen (O), which is the chemical composition of an aluminosilicate compound. The numerous polygonal lamellae could be the initial cause of the damage due to stress application on the roller pump tube and/or friction between opposite inner surfaces caused by tube deformation.
Haptic information is crucial in the execution of precise and dexterous manipulations. This paper addresses the challenge of skill evaluation during laparoscopic surgery by (1) automatic classification of basic manipulations, (2) evaluation of similarity between professional doctors and novices by a DP matching technique. First, manipulations with forceps during a laparoscopic surgery were categorized into four basic manipulations based on a video observation. Then, we developed forceps with a force sensing capability, and the basic manipulations were automatically classified based on the measured force information. By comparing with professional doctors' basic manipulations database, the difference of manipulation skills between novices and doctors was evaluated by the DP matching method. We conducted (I) a tape peeling task and (II) a tissue cutting task with novices and doctors. The experimental results show that the manipulations done by the doctors were much closer to the manipulations stored in the database than those done by the novices (p=0.0013 for the tape peeling task, p=0.021 for the tissue cutting task).
Although many numerical simulations have been proposed to determine the mechanisms of cardiac excitation-contraction coupling, neither potential distribution nor mobility of the cytosol and ions has been taken into consideration in these models. Therefore, we applied the triphasic theory to our previously reported 3D finite element model of cardiomyocytes to examine the significance of these factors in cardiac physiology. The salient feature of triphasic theory allowed us to study the behavior of solids (proteins), fluids (cytosol) and ions governed by mechanics and electrochemistry in an integrative manner in detailed subcellular structures, including myofibrils, mitochondria, the sarcoplasmic reticulum, membranes and t-tubules. Simulation results showed that there was a 0.5 mV electrical potential difference inside t-tubules at the onset of depolarization, and that this potential distribution was inverted when Na+ channel density was altered. We also found a significant movement of the cytosol from the A-zone to the I-zone of myofibrils and ejection of fluid from t-tubules to the extracellular compartment during contraction. Our results indicated the capability and necessity of triphasic theory in the detailed analysis of cardiac physiology.
Visual evoked potentials (VEPs) are the electrical response of the brain concerned with visual information processing. Amplitudes of VEPs are smaller than that of background EEG activity, and then the stimulus-locked averaging method is usually used for obtaining the waveform. VEP response to each stimulus is not completely the same but has variability for its amplitude and duration. Therefore, amplitude of averaged VEP waveform deteriorates due to their variability in raw data. Feature extraction of background EEG activity during visual stimulation is also one of significant items in VEP analysis. In that case, separation of VEP component and background EEG component (mainly posterior dominant rhythm) is crucial. In this study, amplitudes of VEP component and posterior dominant rhythm were simultaneously estimated by using the EEG model. Usefulness of the proposed method was investigated by comparing the conventional stimulus-locked averaging method and power spectrum averaging method. Influence of the VEP variability and the background activity for estimating amplitudes of VEP and posterior dominant rhythm were analyzed through the simulation study. In addition, the proposed method was applied to actual recorded VEP data and its effectiveness was evaluated. The proposed method will be applicable to accurate VEP analysis and characteristic analysis of background activity under visual stimulus.
Most vital-sign transmission systems utilize wireless technology using radio wave. However the radio wave transmission has some problems such as electro-magnetic compatibility. We propose a novel vital-sign telemetry system using NF-IBC (Near-Field Intra-Body Communication) which communicates without radio wave, in order to solve any issues that radio wave transmission has. In previous research, we developed and tested NF-IBC transmitter. In this paper, SS (spread spectrum) technique was applied to NF-IBC to improve the communication reliability. First of all, we changed the condition of the transmission path, and evaluated the error rate of transmitted data. As the next step, we compared and evaluated noise immunity on SS and non-SS NF-IBC. Finally, we tried to transmit ECG data measured on the body. The results from these experiments show that SS NF-IBC has sufficient reliability on basic performance and applicability to ECG transmission.
The purpose of the present study is to establish a method to estimate viscoelasticity of muscle, subcutaneous tissue and skin by using mechanical stimulation. Six healthy male subjects participated in the experiment. The tibialis anterior muscle in voluntary isometric contraction was stimulated with a vibrator. The driving force(f), the vibrator acceleration(a), and the acceleration on the skin(y) were detected with an impedance head close to the muscle belly, and two acceleration sensors attached on the skin of 2 cm proximal and distal site of the muscle belly. The frequency response function between f and a, G(ω), biomechanical impedance, and the frequency response function between a and y, H(ω), were calculated. The undamped natural frequency, which mainly reflected the elasticity, was calculated as the frequency at which the real part of G(ω) or H(ω) become equal to zero. Effective vibration mass, elastic modulus, viscous modulus, and damping factor were estimated by approximating the frequency response function to that of a mass-damper-spring model with the nonlinear least square method. The undamped natural frequency of G(ω) increased as the contraction level increased, while that of H(ω) did not. The function G(ω) dominantly reflected the muscle characteristics because the vibrator was forced into the skin. The elastic modulus of the muscle increased, and effective vibration mass and viscous modulus did not increase, and damping factor decreased as the contraction level increased. At 2 cm proximal or distal site, the subcutaneous tissue and the skin had a dominant effect because they were the propagating medium of the vibration. In conclusion, viscoelasticity of the muscle, the subcutaneous tissue and the skin could be estimated with G(ω) and H(ω), respectively.
Rhythm in biology such as walking patterns (gait) is thought as being controlled by a neural network called central pattern generator, or CPG. However, its mechanism from a viewpoint of physiology has not been clear. Rybak et al. (2006) proposed a neural network model of the CPG using Hodgkin-Huxley type equations, and showed that the dynamics calculated by their model reproduced the experimental results using the decerebrate cat. Furthermore, they made several improvements on their model by means of adding the afferent stimulations from the extensor and flexor sites. In this paper, we constructed a similar network model from the viewpoint of the electronic circuit design, and, as such, reproduce completely the dynamics obtained from Rybak's mathematical model. Using such hardware simulations, one can design and control walking patterns of the locomotion robot without using software program, and implement its real-time simulation.
The purpose of the present study is to develop an accessible electronic musical instrument “Cymis” for persons with motor dysfunction to play and enjoy by controlling their breath pressure. The instrument consists of a computer, a monitor, a breath pressure controller, speakers and a touch panel. It is significant characteristics of Cymis that pre-programmed music scores are stored in the computer. It is indispensable for the practical use of the breath pressure controller that sterilization, maintenance, overhaul and trial manufacture can be easily carried out by end users, e. g., staffs of social welfare facilities and school teachers as well as technical experts. The controller was devised from this viewpoint. For safety the breath pressure was measured indirectly with the aid of a silicone diaphragm and a pneumatic sensor. Accurate measurement of the breath pressure was experimentally indicated. Taking account of their own physical conditions and music making abilities, clients can choose an appropriate one among four types of musical performances, measure-, beat-, note- and standard type-performance. Subjects without motor dysfunction could play Cymis properly with the controller in laboratory experiments. Field trial in a social welfare facility commenced in 2008;one client with cerebral palsy has enjoyed playing Cymis with the controller about half an hour a week for four years. These results seemed to indicate the usefulness that Cymis was attractive to the disabled and permitted them to do an enjoyable activity.
Hitherto, we have made the body-region separately weighing system by way of trial, and clarified the measurement of six body regions by taking a horizontal position to be possible under a certain specified measuring condition, and also, reported the measurement of the weight of trunk composed of upper and lower trunk might be possible by measuring their weights separately. In this study, the details of the measurement method of seven body region weights by use of a body-region separately weighing system were described. By using a body-region separately weighing system which was made with commercially obtained seven platform weighing machine and a laptop computer by way of trial, the weights of the seven body regions of a human body in a horizontal position, namely, the head, right and left arms, upper and lower trunk and right and left legs were confirmed to be measurable almost at the same time, with a good reproducibility. Thus, it was found that the measurement of the seven body regions of a subject was possible, and especially, by holding breath of the subject for a while, a remarkable reduction in the variation of the measured weight values, especially those of upper and lower trunk was clearly observed.
Single needle dialysis (SND) is performed with a single needle that often causes blood recirculation. To date, optimal operating conditions of SND have not been determined to minimize recirculation. In this study, we evaluated whether the stopping position of a blood pump roller affected dialysis efficiency. First, we determined three stopping positions with different venous pressures. Then, we estimated recirculation volume at each position based on the flow rate. When a stopping position could achieve the most effective tube occlusion, the recirculation volume was minimized, suggesting that the position allowed optimal dialysis operation.
A pulse oximeter measures the percutaneous arterial oxygen saturation (SpO2) by the absorption ratio of two different wavelengths of light that pass through the tissue. Sensor misalignment and incorrect position can cause inaccurate results. Especially in the case of neonates and infants, finger size or sensor location can create a gap between the sensor and finger. This gap may cause light leakage that does not pass through the tissue (“shunted light”). This might be one cause of inaccurate SpO2 measurement. We investigated the effect of shunted light on SpO2 value while displacing the sensor laterally from the center to the outside of the finger. We found that lateral sensor displacement caused shunted light which degrades measurement accuracy. We also found that if the LED or photodiode is firmly attached to the finger and the shunted light is shielded, there were very few errors in the measurement value. We think that sensors which shield the shunted light and fit the finger firmly will improve measurement accuracy in pulse oximetry.
This paper proposes a surgical assistance scheme, which enables to locate small cancer lesion using RFID (Radio Frequency Identification Tags). State-of-the-art systems for endoscopic surgery are expected to be capable of finding very small cancer lesions in the diagnostic imaging although such small lesions have been difficult to be identified for excision through an endoscope. To find such small lesions surely during endoscopic excision surgery, a new endoscope supporting system is desired. In our proposed system we use a RFID tag to label each small lesion part during diagnostic imaging, then use a RFID tag signal sensor antenna at the time of an operation and supports discovery of a lesion area. In this report, it is possible to estimate a small lesion area using the RFID tag system, which is composed of the signal sensor antenna and RFID tags. The measurement system using a RFID tag and 4 sensor-antennas was made as an experiment, and the experiment using phantom was conducted. As a result, the difference with a theoretical value of less than 40 mm of distance of a RFID tag and a sensor antenna and the value acquired in 10 mm of phantom thickness was less than 2 mm. Furthermore, the value acquired when moving the spatial relationship of a RFID tag and a sensor antenna 20 mm each in x, y and z was verified, and it was shown clearly that errors are a minimum of 2.6 mm and a maximum of 22 mm.
The coupling of cellular processes at the tissue and organ level usually involves the handling of partial differential equations (PDEs). Since physiological computational models using PDEs have varied greatly in terms of complexity, most solutions are tailored for specific problems. Space-time discretization schemes like FTCS (Forward-Time Centered-Space), BTCS (Backward-Time Centered-Space), Dufort-Frankel, Crank-Nicolson and Lax-Friedrichs exist. We propose a general approach for handling PDEs in computational models using a replacement scheme for discretization. The replacement scheme involves substituting all the partial differential terms with the numerical solution equations. During the replacement algorithm, the time and spatial indices are also appended to the model variables. This method allows for handling of different forms of equation. Once the derivatives are replaced with the discretized terms, the resulting equations are then written in a recurrence relation form. Finally, the equations for solving the unknown variables are generated. The solution to the linear system of equations uses iterative methods like Gauss-Jacobi and Gauss-Seidel algorithm. If the system is explicit, corresponding loop structure is generated as program code to solve the system. We could successfully generate an excitation propagation simulation program for FTCS scheme with a complex cell model.
When measuring the surface EMG with bipolar lead, we must paste electrodes alonga muscle fiber direction. However, the pinnate muscle is known as that the pinnate angle will change by its contraction strength. Also, there is a research that we must consider about the 3-dimential positional relationship between the muscle bundle and the aponeurosis, when we measure the pinnate angle. Therefore, we think the muscle fiber direction of the pinnate muscle will change by its contraction strength. The aim of this study is development of new EMG measurement method responding to muscle movement. Our new EMG measurement method can calculate the EMG signal among to muscle fiber direction if muscle fiber direction changes during movement. In this study, we have confirmed the usefulness of our estimation method using simulated EMG generated by an EMG model. In addition, we measured the surface EMG of the vastus lateralis muscle and estimated the muscle fiber direction by our estimation method.
Recently, we easily access 3-dimensional (3D) entertainments, i.e. 3D broadcastings or 3D cinemas. Stereoscopic visions in humans use binocular and monocular depth cues such as binocular parallax, vergence, lens accommodation, size of visual object, shading, and so on. Strong depth cues, however, may affect human visual systems and it may induce dizziness or headaches. Then it should be very important to know optimal condition of depth cues and interaction within the cues. In this study, we focused on two depth cues;binocular parallax and object size. We investigated how these cues affect depth perception and the interactions of the cues. We stereoscopically presented two visual stimuli on a 3D TV for subjects and they were required to answer which stimulus was presented nearby them. They answered correctly when viewing normal size condition, i. e. nearer stimulus presented larger than the farther one. On the other hand, their performances dropped when they watched illusion-condition stimulus, i.e. farther stimulus presented larger than the nearer one. These results indicate the object size may one of the important factors for stereoscopic depth perception in the virtual 3D environments. The subjects were divided into two groups according to their performance (cutoff was 50% correct). We found vergence eye movements in the lower score subjects were dysfunctional, especially on convergence. Vergence functions may affect depth perception.
Since collagen fibers are crucial in determining the mechanical properties of the aorta at large strain levels, they may affect aortic rupture profoundly. In this study, we observed change in collagen fiber direction in the aortic media under equibiaxial stretch. The media of porcine thoracic aorta was sliced into 50 or 100-μm-thick sections perpendicular to the radial direction and stretched under a microscope equipped with birefringent imaging system to measure slow axis azimuth θ (circumferential direction is taken as 0°) as an index of the direction of collagen fibers. At no-load state, collagen fibers sharply oriented in the circumferential direction in sub-intimal specimens. The distribution of the orientation became broad as one goes toward adventitia, and had two symmetric peaks in sub-adventitial specimens. The differences between the two peaks were 2.9° and 40.0° for sub-intimal and sub-adventitial sides, respectively. The collagen fiber direction corresponded to the long axis of the cell nuclei, indicating that the collagen fibers were oriented in the long axis of cell direction. Standard deviation of the collagen fiber angle in each specimen was 19°±7° (mean±SD, n=6) at no-load state. By applying the equibiaxial stretch to the mid-medial specimens, the standard deviation of the fiber angle decreased gradually to 13°±6° (n=6) just before failure, indicating that more collagen fibers oriented in the circumferential direction. It has been reported that cracks of specimens obtained from porcine thoracic aortas always run in circumferential direction at rupture. The direction of collagen fibers might be a determinant factor for the aortic failure.
The purpose of this study was to investigate the effect of an uneven surface on muscle spindle function in lower-leg muscles during walking. Subjects included 10 healthy young adult males. Normal and high-speed walking motion was measured on two surfaces:an even surface and an uneven surface. Healthy and reduced muscle spindle function conditions were compared. The ice immersion approach was applied on the lower-leg muscles as a method of reducing muscle spindle function. By varying the material from which the surface was made (sponge or hard acrylic), changes in the surface were induced. During high-speed walking on this uneven surface, the standard deviation for step width increased significantly (p<0.05). In the reduced muscle spindle function condition, velocity increased when subjects stepped on the sponge (p<0.01). In addition, adjustment of step length significantly reduced. The increased standard deviation for step width suggested instability of gait. Therefore we concluded that muscle spindle function is important in order to walk on the uneven surface. The increased velocity after subjects stepped on the sponge portion of the surface and the reduced adjustment in step length suggested that muscle spindle function is important for the purpose of walking on uneven surfaces.
Elution of polyvinylpyrrolidone (PVP) from the membrane surface is one of the important problems with polysulfone (PS) membrane dialyzers. The aim of this study was to investigate the influence of a vitamin E-coated PS membrane dialyzer on the elution of PVP. A vitamin E-coated PS membrane dialyzer (VPS) and a conventional PS dialyzer (APS) were compared in this study. The amount of PVP eluted into sterile water obtained from the blood compartment of fresh dialyzers was measured. Then, each dialyzer was washed with 1.0 L of 0.9% NaCl and the amount of PVP eluted from the dialyzer was measured. Subsequently, experimental use of each dialyzer was performed by circulating 1.0 L of 0.9% NaCl solution for 4 hours at 37°C, and the amount of PVP eluted was measured. As the results, there was no significant difference in the elution of PVP into sterile water from the APS and VPS dialyzers. The amount of PVP eluted in the APS dialyzer washings was 0.5 (0.1-2.3) mg, expressed as median value (25th-75th percentile), while it was not detected in VPS washings. Also, the amount of PVP eluted at experimental circulation of the APS dialyzer was 2.1 (1.7-2.9) mg, while that of the VPS dialyzer was 0.1 (0.0-0.3) mg. There was a significant difference between two dialyzer groups (P=0.018). Except for the vitamin E coating on the membrane surface, both PS membrane dialyzers (VPS and APS) were manufactured by identical processes. These results suggested that coating a PS membrane with vitamin E suppresses the elution of PVP during hemodialysis therapy.