Infant of muscle strength and skeleton have not enough provided stimulus which become a factor for defective bone formulation of feet as the results induced podiatric problems. In this study, we focused on lower limb muscle strength in children. We developed quantitative, easy-to-use measurement devices for assessing toe-gap force and knee-gap force in children. The aim of this study was to examine the following 3 factors: (1) to examine the efficiency of measurement devices by using a field test; (2) to examine the basis of development process on lower limb muscle strength in infants; and (3) to examine the effect of habitual exercise on lower limb muscle strength development. The study subjects consisted of 579 kindergartners aged between 3 and 6 years. In all subjects, toe-gap force and knee-gap force were measured using measurement devices, and development of age related was indicated by both measurement methods. It is supposed a threshold as 0.4 kgf of toe-gap force in three to four years old, as 0.6 kgf in five years old, as 0.8 kgf in six years old. Especially, children who were not enough developed found on toe-gap force in the experiment. Age-related development was found to increase knee-gap force in children (4 kgf in 3-year-olds, 5 kgf in 4-year-olds, and 6 kgf in 5-and 6-year-olds, at the peak of frequency distribution). It is supposed a threshold as 2 kgf of knee gap force in three, as 3 kgf in four years old, as 4 kgf in five years old, as 5 kgf in six years old. Habitual exercise was found to improve toe-gap force in 6-year-olds; children who exercised regularly showed 1.4-times higher improvement in toe-gap force than those who did not exercise regularly. It is suggested that habitual exercise increases toe-gap force in children.
In this study we propose a new method of texture analysis to detect aMCI (Amnestic Mild Cognitive Impairment) by using an MRI (Magnetic Resonance Imaging). The problem in the conventional texture analysis for aMCI diagnosis is that is only one pixel was applied to the detection. we therefore proposed to reconsider the pixel distance of texture features and gray scales by examining 70 MRI images of 37 aMCI patients against a 33 healthy elderly control group (70 subjects in total). In our method we increased the pixel distance to 2 or more and lowered considerably the graduation level. This allowed us to observe a clear difference between aMCI patients and the healthy control group. This discriminating analysis using the proposed texture features demonstrated an overall accuracy of 100% in our dataset. Thus, this indicates that our proposed method can be used as the new detection technique for aMCI.
Recently, in order to achieve the prevention or early detection of diseases, many studies have been carried out to measure physiological information in everyday life. The purpose of this study is to develop the mat-type device to measure physiological information fro6m the sole. ECG (Electrocardiogram) and PPG (Photoplethysmogram) that are the indices of the cardiovascular system were adopted as physiological information. ECG is measured by conductive coupling without using the paste and capacitive coupling that is able to obtain ECG and PPG with socks. PPG is obtained by measuring the reflected light to incident infrared light at periphery. PWV (Pulse wave velocity) which is the index of the arteriosclerosis is able to be calculated from ECG and PPG. The subjective experiment reveals that the developed system can measure ECG and PPG. In addition, the system can measure ECG and PPG in case of wearing socks. Moreover, by simultaneous measurement of blood pressure, PWV was calculated by the developed system and the good correlation was found between PWV and blood pressure. In addition, the experiment showed that the PWV were changed with the blood pressure changes due to exercise. Therefore, result of this experiment showed this system has the potential to monitor the condition of cardiovascular system, and suggested the possibility to estimate the blood pressure without compression by the cuff.
Because the tongue is controlled by the cranial nerve, even people with cervical cord injury can usually perform various voluntary tongue movements. With attention to voluntary tongue motion, which is capable of communicating the intentions of a person with a disability, we estimated the tongue movement using EMG signals of the underside of the jaw, where the suprahyoid muscles are crowded. Suprahyoid muscles usually function to open the mouth, and to control the position of the hyoid, the base of the tongue. We affixed a multi-channel electrode with nine electrodes to the underside of the jaw. Then, deriving many EMG signals using monopolar leads, we calculated 36 (=9C2) channel EMG signals between any two of the nine electrodes. Associating these EMG signals and tongue movements using a neural network, we confirmed our ability to estimate tongue movement with 91.5% precision. Furthermore, building a neural network for estimating mouth opening and deglutition, which are potential origins of false estimation, and discriminating that movement with 92.0% precision, we suggest precise extraction of only the signal of voluntary tongue movement from EMG signals of the suprahyoid muscles.
This paper proposes the use of electrode grid for Japanese vowel recognition based on surface electromyography (sEMG). Previous studies have indicated the potential effectiveness of sEMG-based speech recognition, not only for healthy people, but also for dysarthric patients. In these studies, however, disc electrodes or parallel bar electrodes were used and located empirically, although there exist relatively small muscles in proximity to each other in the face or neck region. In order to avoid missing out information about speech, we examined the effectiveness of using an electrode grid, which consists of densely-spaced multielectrodes. In our experiments, we measured sEMG signals from the submental region with the electrode grid during the production of 5 vowel sounds. Continuous hidden Markov models were applied to the sEMG signals for vowel recognition. We compared the recognition accuracies between the two methods: One was based on signals from all channels and the other was based on virtually reconstructed single bipolar signal. The former achieved considerably higher recognition accuracy than the latter. This result indicates that using electrode grid is more effective in extracting information for sEMG-based speech recognition.
External fetal monitoring by phono or Doppler uses a cumbersome strapping belt around the torso of gravida, in order to apply the transducer at an appropriate position on her abdomen. The belt causes bother and stress to her. Here in this study we successfully devised a self-sticking suction cup type fetal phono microphone and fetal Doppler transducer, to eliminate the strapping belt or to mount the transducer to abdominal wall. A deformable silicone rubber cup is used as housing for the transducer assembly, to make either an air chamber type phono microphone or coupling chamber type Doppler transducer. When the deformable cup is flipped and pressed to target position of body surface and again flipped back, the chamber keeps air-tight coupling to abdominal wall having slightly negative pressure supported by its forming-back force while sucking-sticking in situ. Prototype phono transducer has a general purpose condenser microphone unit, while prototype Doppler transducer has 1MHz unbacked 10mm dia PZT element with diverging lens. The prototypes yielded diagnostic quality of fetal heart trace for minimum 30 minutes continuity at as-attached state without interruption.
Multiunit recording has been widely used in neuroscience studies. In this recording, some spike-sorting method is required. For the spike-sorting, independent component analysis (ICA) has recently been used because ICA potentially separates overlapped multiple neuronal spikes into the singles. However, multiunit signals are recorded in each electrode channel possibly with channel-dependent waveform transformation (spatio-temporal mixture). This situation does not satisfy the instantaneous mixture condition prerequisite for most of ICA algorithms. To address this problem, we have proposed a novel spike sorting method incorporating wavelet transform and complex-valued ICA and have evaluated the performance. In this paper, firstly we compared proposed method with the real-valued ICA-based method by applying them to a synthetic multiunit signal. This application result showed that the ICA algorithm extended to complex-valued signals makes much more improvement in spike sorting performance. However, the accuracy of spike-sorting decreases commonly in both ICA-based methods, as S/N ratio becomes lower. Further investigation disclosed a possible mechanism that the noise disturbs accurate estimation of the basis vectors for separation. To the actual multiunit signals, our method outperformed the real-valued ICA-based method as well. Shortly, although the proposed method can solve the spatio-temporal mixture, it should equip with robustness against noise and should be improved for handling over-complete situations. For this to be realized, a hybrid method combining a pattern recognition-based method with the proposed method will be one of valuable options in the future.
During surgery to remove a brain tumor it is important to discriminate normal tissue from cancerous tissue. Here we report a method to identify tumor tissue using a confocal microscope with laser illumination. The confocal microscope has several useful qualities for this work:it has high resolution and can also reject light that is not from the focal plane. The microscope was set up with an illumination laser of wavelength 405nm and a red fluorescence filter at wavelength 610-680nm in front of the CCD camera. This arrangement attenuated the direct light of the laser to increase the contrast in the fluorescence image. The field of view of the microscope was about 100μm square with a×40 objective. Before surgery, the patient drank a solution containing 5-ALA which induces formation of fluorescent porphyrins in tumors of type glioblastoma. Tissue samples taken during surgery were put onto the microscope stage. CCD images were obtained and it was found that tumor tissue emitted more red light and could be visually distinguished from normal tissue in the images. To quantify the difference, the intensity of all red pixels was added to form a total intensity in several images. The CCD red response to tumor tissue was found to be more than 2 times the response to normal tissue. We conclude that the confocal microscope method can distinguish tumor tissue at distance scale 100μm.
Physiology models written in a description language such as CellML are becoming a popular method to handle complex cellular physiological models in biological function simulations. However, in order to fully simulate a model, boundary conditions and ordinary differential equation (ODE) solving schemes have to be combined with it. Though the former can be described in CellML, it is difficult to explicitly specify ODE solving schemes using existing tools. In this study, we defined an ODE solving scheme description language based on XML and proposed a code generation system for biological function simulations. By using the proposed system, biological simulation programs using various ODE solving schemes can be easily generated. We designed a two-stage approach where the system generates a set of equation associating with the physiological model variable values at a certain time t with values at t plus delta t in the first stage and generates the programs calculating the time evolution of the model in the second stage. This approach enables the flexible construction of code generation modules that can support complex sets of formulas. We evaluated the relationship between models and their calculation accuracies by simulating complex biological models using various ODE solving schemes. Using the FHN model simulation, results showed good qualitative and quantitative correspondence with the theoretical predictions. Results for the LuoRudy1991 model showed that only first order precision was achieved. In addition, running the generated code in parallel on GPU made it possible to speed up the calculations by a factor of 50.
This report evaluates the efficacy of contact pressure to the probe of photoplethysmography (PPG). The problem facing the PPG is motion artifact superimposed on PPG. When a body movement occurs, changes in vascular volume cause motion artifact. Thus it is difficult to precisely count pulse rates. We consider the contact pressure of attaching probe related to motion artifact. In order to eliminate the motion artifacts, we compared the effects of pressure applied to attaching probe of PPG. Eight young healthy subjects without any indication of peripheral arterial disease were recruited to participate in the experiment. To determine the contact pressure, the pressures ranged from 0 to 70 mmHg were applied to the probe. At the 30 mmHg, the amplitude of PPG signal reached its peak without vessel occlusion and so we set contact pressure at 30 mmHg. Then seven young healthy subjects without any indication of peripheral arterial disease and gait disorder were recruited to participate in the experiment. They attached the green PPG on the upper arm with either no pressurization or applied contact pressure and monitored heart rate as a standard. To produce artifacts, the subjects were asked to walk at a speed of 3km/hr on the treadmill. Then the PPG and ECG signals were measured for 2 minutes. PPG magnitude and intervals were calculated by peak detection using predetermined thresholds, and the error rate between the PPG pulse rate and the heart rate was then compared. As the result, the pressured green PPG showed the lower error rate at 3.6%. The error rate of pressurization was significantly decreased in comparison to that of no pressurization (p<0.05). In conclusion, the pressure applied to the green PPG may be useful for pulse rate monitoring during body movement.
In neurosurgery, the retraction using the suction tube is one of the most difficult techniques according to the experience and the sensation. As the navigation for the retraction, the measurement of the retraction state and its feedback by using tactile display seems to be effective. This research aims at developing the small and simple feedback system which can tactually present the current state of retraction according to the desired retraction. Previous navigation systems measured the applied force to the object and presented the forces by a tactile display. On the other hand, the proposed system focuses on the energy of the retraction stored in the instrument and presents the energy by electrotactile display to establish the small and simple feedback system. In actual, we estimate the applied energy to the object based on the measurement of the strain of the instrument, and present overloaded energy by the electrical stimulus at the media of the index finger. The subjective evaluation was conducted by using a phantom material. The results indicated that users could keep the error of less than 10% between the desired and real retraction forces and completed the stable retraction.
We have developed a system for measuring the viscoelastic property of the skin that involves no direct contact with the body surface. By applying the air pressure, the quantitative value of elastic modulus was calculated based on Boussinesq equation with the displacement of the body surface which was non-contact measured using laser displacement meter. This system needs about 3s measuring time and the accuracy of the elastic modulus was within 10% error range. In this study, the elastic moduli of the extensor and flexor forearm surface were measured for the determination of standard range of these regions so as to compare these with that of systemic sclerosis. As the results, no significant difference was recognized in the laterality of the forearm and the difference between extensor and flexor position. On the other hand, the normal forearm elastic modulus measured in the male showed the tendency that was larger than that of female, and the elastic modulus showed decrease with age in both of male and female. To applying this system to measure the forearm of systemic sclerosis patients, loading air pressure was changed to higher level in compare with normal subjects. Obtained elastic modulus was compared with modified Rodnan total skin thickness score (m-Rodnan TSS) that was used regularly clinically. In the higher m-Rodnan TSS in the systemic sclerosis patients, the elastic modulus was also higher than that of normal subjects. These results suggested that the clinical efficacy of diagnosis will increase by adding the quantitative numerical value obtained by this method to four stages of indexes of skin score. This system is clinically useful to quantitatively evaluate the body surface as the elastic modulus, because of the non-invasive and non-contact measurement in addition to satisfactory operability of the system.
Accurate assessment of the sleep cycle at home will improve self-awareness regarding the necessity of sleep for relieving fatigue. Previous studies have shown that a large number of body movements occur during light sleep compared to deep sleep. In the present study, sleep was assessed by monitoring body movements using an infrared motion sensor and Polysomnography (PSG) for a 420-min period from 00:00 to 07:00. The findings of sleep cycle based on body movements were compared with PSG findings. One cycle of sleep cycle was defined as a set of “REM, sleep level 1, 2, 3 or 4” period and subsequent “SWS, sleep level 5 or 6” period. We defined Body Movement Density (BMD) as an index of sleep cycle. BMD was a value representing the number of body movement occurrences during a 30-minutes period. The cross-correlation coefficient between BMD and sleep levels was significant in all subjects (13 males, 3 females;age, 20-23 years). In this study, a concordance rate of 76.9% (SD±24.0) between BMD cycle and sleep cycle was obtained. This study indicates the possibility of estimation for sleep cycle by using BMD without using PSG. One of the greatest advantages of BMD is that it comprises only body movement data, so measurements of breath, heart rate or brain waves are not required. Moreover, measuring BDM is both inexpensive and noninvasive.
The purpose of this study is to propose a method of a walking assistance by using an exoskeletal system “Hybrid Assistive Limb (HAL)” for cerebral palsy (CP) patients who cannot stand up and walk due to the abnormal generation of the bioelectrical signals (BES) in their lower limbs associated with the brain disease, and to verify the effectiveness of the proposed method through a clinical trial. HAL was developed to support the voluntary movement of the wearer based on the BES. The proposed method consists of two algorithms, that is, an assistance of voluntary movement in the swing phase and an assistance of weight bearing in the stance phase. The assistance of the voluntary movement determines the rotational direction of the actuator from the ratio of the abnormal BES by using sigmoid function during the swing phase. On the other hand, the assistance of the weight bearing adjusts automatically the stiffness and viscosity of the joint during the stance phase. In the clinical walking trial with a 3-meter walk using parallel bars, we confirmed that HAL including the proposed method achieved the patient's walking assistance. Especially, the assistance of the voluntary movement in the swing phase produced his leg-swing based on the BES signals. As a result, the walking speed, cadence and stroke width of the patient with HAL during this trial are 1.6m/min, 11.4 steps/min and 0.14m, respectively. In conclusion, we have proposed the method of the walking assistance method and thus, confirmed the effectiveness of the proposed method.
Low back pain (LBP) is one of severe diseases due to an overload onto lumbar area such as vertebrae, disks and nerves. The pathogenesis of LBP are caused by the physical load on the lumbar during the task of keeping a static posture, lifting a weight, spinning a lower back. To reduce the physical load, exoskeletal robots are researched and developed. However, it is difficult to verify non-invasively the load reduction of wearer's endoskeletal by motion assist. The load reduction of endoskeletal such as lumbar disks of area of injury can not be verified. The purpose of this paper is to propose and develop 3D skeletal model and the method that verify load reduction of wearer's endoskeletal, and to verify the effectiveness of HAL for lumbar support on lumbar load reduction. 3D skeletal model that consists of vertebrae and disks was developed based on anatomical insight and the radiograph of ordinary person. Finite element method (FEM) by using this model was proposed as the evaluation method of motion assist of exoskeletal robots. We simulated this model of wearer holding a weight, and analyzed the lumbar stress, without or with HAL support. The wearer held weights of 5-20kg in a flexed posture. The effectiveness of this model was confirmed, because the stress concentrates on lumbar disks in a flexed posture. The analysis results showed that motion assist by using HAL decreases lumbar stress when it is compared to without HAL support. We proposed and developed the method that verify load reduction of wearer's endoskeletal, and verified the effectiveness of HAL on lumbar load reduction. The evaluation method of motion assist of exoskeletal robots was developed by this study. The proposed method can be applied to upper and lower body. It is expected as new index of motion assist.
The importance of voluntary exercise and sensory input in rehabilitation training after spinal cord injury (SCI) or cerebrovascular disease has been demonstrated by recent studies. However, the voluntary exercise is an impossible task for severe paraplegic and hemiplegic patients who cannot move their lower limbs by themselves. The purpose of this study is to verify whether these patients can perform a new voluntary exercise by using a robot suit which generates walking motion in place of the wearer's paralyzed muscles by detecting their voluntary bioelectrical signals. Two severe SCI patients who can barely produce neuromuscular activation but cannot move their lower limb participated in this study. Experimental results demonstrated that the robot suit was able to detect their voluntary neuromuscular activities via bioelectrical signals and provide stepping and walking motion having appropriate temporal relationship with the voluntary activities. In addition, the proposed voluntary exercise using the robot suit can significantly promote neuromuscular activities of the target muscles more than passive exercise.
Hospital use a variety of medical equipment (ME). Some of this equipment, such as infusion pumps and syringe pumps, are regularly moved around the hospital ward. Occasionally this equipment can get misplaced. The equipment can be moved if the locations are detected automatically. However, battery-less identification media is necessary. Authors newly developed battery-less, 950MHz passive RFID tag with a range of approximately 11 meters. In this study, identification area of the tag attached to infusion pump is verified in hospital. Identification area is enough to detect the ME device with tag. It is considered that the ME equipment in hospital can be managed inclusively by the new RFID tag.
In this study we proposed a new noncontact sleep stage estimation method using environmental, forehead and nasal skin temperatures by Support Vector Machine (SVM). The forehead and nasal skin temperature and environmental temperature were measured by a thermography, and the sleep stage was estimated from these temperatures by use of nonlinear SVM with RBF kernel. The polysomnography and thermography were measured simultaneously. Sleep stages were classified into 6 classes:Wake, REM and Stages 1, 2, 3, 4 that are non-REM based on Rechtschaffen and Kales (R & K) scoring rules. When using SVM, measured environmental, forehead and nasal skin temperature data were input to SVM, and the reference data was given as the corresponding correct label. Subjects were five healthy males (age 24.0±7.9 years;mean±SD), and ten data sets were created from the data of all subjects using boot strap random sampling. SVM was trained using the ten data sets, and we evaluated the estimate accuracy as each class. Tuning parameters of the RBF kernel were decided heuristically by grid search, and the generalization capability was tested using cross validation test. Results showed that the classification rate of each sleep classes is as follows;Stage 1:73.2%, Stage 2:96.1%, Stage 3:45.5%, Stage 4:97.1%, REM:89.6%, Wake:63.6% and no error were found in the estimation of sleep state change from each sleep stage to wake stage. The total classification rate was 88.5%, and the 10-fold cross validation test was 81.7%. These results demonstrate that SVM could be classifying the sleep stages by using of the environmental, forehead and nasal skin temperatures.
Microbubbles form aggregates by secondary Bjerknes force, which behaves as attractive or repulsive force between the bubbles, in an ultrasound field. However, not only the mechanism to form aggregates but also the size of aggregates, or the length of time for the aggregate formation were not entirely clarified yet because of the complexity of the parameters involved. In this study, we have observed aggregate size development with an elapse of time and measured their average size under various conditions of ultrasound field by using a high-speed camera. We also evaluated the influence of the presence of red blood cells in the suspension with microbubbles. We prepared microbubbles (microcapsules) with a hard shell of poly(vinyl chloride) to compare with Sonazoid, which is commercially available for clinical use. First we have measured their resonance frequency and determined the range of frequency varying from 3 to 10 MHz. We found that the saturation size of aggregates at 3 MHz of central frequency was two times greater than that at 10 MHz in both types of microbubbles and the shortest formation time of Sonazoid aggregates that confirmed at the resonance frequency. Then, we showed that the saturation size of aggregates was inversely proportional to the ultrasound frequency and the formation time became short at the resonance of bubbles. In addition, we confirmed that the aggregate formation of bubbles is unaffected by the presence of red blood cell with the concentration less than 6.50×106 cells/ml.
A system for real-time monitoring of cell population behavior is required to noninvasively evaluate cellular function and to assess the quality of the cell culture process. The purpose of this study has been to develop a real-time monitoring system using particle image velocimetry (PIV) for visualizing and measuring the behavior of individual cells in a cell population. Proliferation of mouse embryonic fibroblast cells (NIH3T3) plated at 0.005×104, 0.01×104, 0.02×104, 0.20×104, 0.50×104, 0.80×104 cells/cm2 was captured using the developed system over a 72-h period. Direction and rate of cellular migration in the cell population were analyzed. Results show that the migration rate of individual cells decreased as the plating density increased. Cells in a low-density culture exhibited a high migration ratio and the migrating direction deviated over time. On the other hand, cells in a high-density culture exhibited a low migration ratio and the migration direction did not deviate. In conclusion, PIV analysis indicates that the migration direction of individual cells depends on cell density.
In this paper, we discuss our development of a hands-free pointing system which uses a laser pointer as a computer interface for persons with physical disabilities. The user can start the system by mounting a laser pointer on his head and placing a USB camera which is able to capture the entire LCD monitor. This camera does not require calibration. The system can solve problems found in previous systems using the laser pointer by controlling the exposure of the camera for detecting the irradiated spot. By comparing the estimated coordinates with the irradiated coordinates, we confirmed the accuracy of the system. And we measured the time needed to locate, point and click on a target, 10 mm by 10 mm squared, that is displayed randomly. The results suggest that the system has a higher degree of user's freedom than previously developed.
Biometric personal authentication is an emerging technology in information security. One resulting problem has been a recent increase in fraud based on falsified biometric data concerning biological information. Brainwave-based identification is a promising biometric tool to prevent impostor attacks. Many researchers have reported biometric results using electroencephalogram (EEG) activity. The brainwave features of each individual are unique and have the potential for use in biometric authentication. Security can be enhanced by employing as many EEG features of an individual as possible. Although it takes time to measure brain waves at present, this authentication method can potentially be used for special security areas in the future. There are several approaches to brainwave biometrics using cognitive processes. We investigated the motor imagery for movements of the left hand, right hand, tongue, and both feet for brainwave biometrics. The nature of brain signal analysis parallels voice signal analysis in some respects. Hence, we applied the cepstral analysis method, which is commonly used in speech recognition, for feature extraction for brainwave biometrics. In our results, we identified almost all nine of the subjects correctly. We tested the performance of our biometric system using the Mahalanobis distance as the threshold and estimated the equal error rate (EER) value to be 0.17.
Total Liquid Ventilation (TLV) is an innovative experimental method of mechanical-assisted ventilation in which lungs are totally filled and then ventilated with a tidal volume of Perfluorocarbon (PFC) by using a dedicated liquid ventilator. So far, we developed the TLV system which consists of membrane oxygenator and a cylinder pump. In this system, PFC gas exchange is performed when passing through the oxygenator. Therefore, this system is largely dependent on the oxygenator performance, and carbon dioxide removal is difficult. In this study, we developed the recirculation TLV system and examined gas exchange ability. This system consists of the conventional TLV system and the recirculation circuit. As a result, the recirculation TLV system as compared to the conventional systems, improved about 25% carbon dioxide removal capability, and partial pressure of carbon dioxide was less than 5 mmHg. This system has a high gas exchange performance.
In laser coagulation therapies, it is important to evaluate a coagulated layer and the depth precisely for preventing excessive laser irradiation. In this paper, we have developed the combination system of a coagulation laser and an optical coherence tomography (OCT). The continuous wave solid-state laser with a wavelength of 532 nm was used as a coagulation laser. The Swept laser with a center wavelength of 1.3μm was used in the swept-source OCT (SS-OCT) imaging system. The frame rate and axial resolution were 50 fps and 12μm, respectively. Real-time tomographic images of the coagulated layers of chicken tissues and liver tissues were obtained by this system. The attenuation coefficient was evaluated from the raster-scan signal of the reflection light intensity of the OCT image. The measured attenuation coefficient of the coagulated layer was much higher than that of the normal tissue. Furthermore, we demonstrated the automatic measurement of the attenuation coefficient by the LabVIEW program originally developed. As a result, the attenuation coefficients increase consistently with a progress of coagulation.
We previously proposed an eccentric figure-eight coil design which induces sufficient currents in the brain at lower output powers of stimulator. In the present study, numerical analyses were performed with various coil design parameters, such as outer and inner diameters and number of turns, to investigate the influence of these parameters on the eddy current distribution in the brain and the coil characteristics. Increases in the inner diameter, the outer diameter, and the number of turns caused increases in the induced currents. In order to downsize the stimulator system, we need to strengthen the eddy current in the brain, maintaining inductance as small as possible. Our results show that it is effective to enlarge outer diameter. In addition, there is only small difference in the eddy current distributions between the eccentric coil and the concentric coil in direction along with the coil plane and with depth of the brain.
We used admittance plethysmography to evaluate hemodynamic changes in the brachial region in response to a dumbbell exercise. Hemodynamic changes were assessed as the change in tissue blood (ΔVdc) calculated from the DC component of the bio-admittance, the pulse wave height (ΔVac) calculated from the pulsatile (AC) component of the bio-admittance, and the arterial blood flow (ABF) calculated from the first derivative of the bio-admittance pulse wave. The change in vascular tone caused by the metabolic vasodilatation was evaluated using d/a, which is the ratio of post-systolic negative waves to early-systolic positive waves and is derived from the second derivative of the bio-admittance pulse wave. Both ΔVdc and ΔVac were significantly increased after the dumbbell exercise. ABF also was increased after the exercise, but not significantly. Furthermore, d/a was increased significantly after the dumbbell exercise, indicating that metabolic vasodilatation caused angiohypotonia in the active muscles. These results suggest that admittance plethysmography is useful for assessing hemodynamics in exercise-induced hyperemia.