We propose a wrist joint motion measuring device that can be applied to training devices. In this study, we developed a wrist motion measurement method that uses wearable parallel-link mechanisms to continuously measure the hand in exercise. The proposed method is non-invasive and has a simple mechanism that uses compact linear encoders. The equipment is attached to the human hand and lower arm via a glove and belts. In experiments, the radial flexion and ulnar flexion motions of 12 subjects were measured, and the obtained results were compared with previous anatomical results. The validity of the proposed method was demonstrated.
Reduction in arousal is one of the main causes that lead to lapses of driver's attention. Therefore, in order to keep a safe drive by the operation of driver's own, it is important to detect the reduced arousal as soon as possible. Currently we focused on saccadic eye movements, which can be measured noninvasively, as a possible detector of driver's reduced arousal. In this paper, we evaluated saccades while subjects were performing a simple reaction test and a driving simulation. We found that changes in characteristics of horizontal saccades, i. e. peak velocities and inter-saccadic intervals, were synchronized with the fluctuation of pupil area that is a well known objective measure of arousal level. Further, when the pupil area decreased because of reduced arousal, significant reductions of these saccade parameters were found prior to the occurrence of slow eye movement (SEM) that is another indicator of unconsciousness or aimlessness. Based upon these findings, we conclude that slowed peak horizontal saccade velocity (<40 deg/s) and shortened inter-saccadic interval (<0.2 s) are useful detector of driver's reduced arousal.
According to visually impaired people, in addition to guiding and safety support, assistance regarding the choice of appropriate colors and patterns for their clothes is required. Even though they cannot see their clothes, the visually impaired want to make a good impression upon others. This sort of social and psychological support is important in enabling the visually impaired to live independently and be able to socialize. A system that can recognize colors and patterns present on clothes is required. Therefore, we have previously developed an algorithm for such a system. In this study, a smartphone is employed to make the system easy to use. It is important to choose a light source for color recognition. In our experiments, we test a system with a cover containing a light inside and another system using environmental lighting that does not require a cover. Since the system with the cover provides a higher accuracy rate of color correction than one using environmental lighting, we implement it into a smartphone and perform evaluation experiments. The results of the experiments indicate that the accuracy rate is about 75% in color recognition and about 83% in pattern recognition, respectively.
Percutaneous coronary intervention (PCI) for ischemic heart disease became a common therapy. The improvement of treatment results was caused by invention of drug-eluting stent (DES) but its implantation procedure for pressure and inflation time has not been discussed. 3-time-balloon-inflation method is proved to be an effective method for inflation in in vitro experiments and it was practiced in the clinical field. The purpose of this study is to determine the effectiveness of the 3-time-balloon-inflation method and investigate the factors that cause suppression of stent expansion. From January 2011 to March 2012, PCI with drug-eluting stent (XIENCE V) were performed to 169 patients by a single-operator with 3-time-ballon-inflation method. Minimal lumen area (MLA), vessel cross-sectional area, and plaque cross-section in the MLA were measured by intravascular ultrasound (IVUS) before stent implantation. Minimum stent area (MSA) was measured after stent implantation. Stent expansion ratio (SER) was calculated from assumed area and MSA. Area acquisition ratio (AAR) was calculated from MSA and MLA. Subsequently, the ratio of calcification in the lesion was measured using the color mapping function mounted on the IVUS. The stent diameter used in this study was 2.89±0.35[mm] (mean±SD), stent length was 20.5±6.2[mm] (mean±SD), and the stent expansion pressure was 10.3±2.4[atm] (mean±SD). There was no difference in SER by stent size, target vessels, and MLA. Significant difference was seen in the calcification ratio between the group without pre-dilatation (n=27) and the group with pre-dilatation (n=142), but no difference in SER between the two groups. It was suggested that calcification ratio is one of the factors that causes the suppression of stent expansion because significance of calcification ratio came out in AAR.
Irreversible electroporation (IRE) is a technique to permanently perforate cell membrane by an application of intensive electric pulses. Since it is achieved via percutaneous electrodes, the IRE shows promise for a less-invasive and non-thermal treatment of tumor tissues. Treatment outcome is affected by various factors such as electrode configuration, physical properties of the targeted tissue, and pulse conditions. For a successful IRE, both ablated volume and unfavorable Joule heating attributed to the electric current must be predicted prior to the treatment depending on above factors. The aim of this study was, therefore, to demonstrate that the IRE parameters depending on the targeted volume could be determined by non-dimensional 3-D solutions to electric field and heat conduction. The Laplace equation and the heat conduction equation in non-dimensional forms were numerically solved using the finite element method for three analytical models with different electrode geometries. Although a number of previous studies have reported that numerical analysis was useful for the prediction of the IRE outcome, our study intended to show extensive usability of the non-dimensional analysis because of its high generality. The analyses provided a set of electric field and temperature distribution in non-dimensional forms, which could be translated to the actual field intensity, ablated lengths, temperature rise, and probability of thermal damage, depending on arbitrary electrode diameter, electrode spacing, pulse voltage, and pulse time. Additionally, a case study with an assumption of IRE ablation for 5-mm diameter tumor was conducted, which demonstrated that the optimal electrode geometry and pulse parameters including input voltage as well as acceptable pulse duration to avoid thermal damage could be determined by a set of the results from non-dimensional analyses.
We developed low power consumption methods for cardiac pacemakers by introducing two novel power-saving methods to the control mechanism with a special focus on the “energy-consuming” clock oscillator. These two methods are:1) a multi-clock method reducing clock pulses required for sensing (self-cardiac potential detection) and pacing (cardiac stimulation) both of which are pacemaker's essential functions mimicking the physiological phenomenon of the heart and 2) a clock-less method charging a self-cardiac potential by charging a capacitor and achieving the sensing and pacing functions by using charge oscillation as a timer. We then designed and assembled circuits by incorporating these two proposed methods. The power consumptions were about 60% for themulti-clock method and about 14% for the clock-less method when compared with the existing synchronous method circuit. It is thus concluded that these two novel methods would offer highly efficient power saving for a pacemaker system, enabling less frequent battery replacement.
We have previously reported our attempts for active control of microbubble aggregations, by making use of Bjerknes force, which acts to propel microbubbles and to adjust the size of aggregations. However, because we have used simple shape of artificial blood vessels, the behavior of aggregations in a capillary, e.g., probability to obstruct in bloodstream, possibility of embolization, has not been predicted. Thus we measured the sticked area of produced aggregation on a wall of artificial blood vessel before evaluating the volume flown to downstream. First we prepared the straight path model of artificial blood vessel with the diameter of 2 mm to produce aggregation by emitting ultrasound against flow, which conditions were with 5 MHz and 300-500 kPa-pp. The size of aggregation increased according to the sound pressure, whereas there would be an optimal flow velocity and suspension density to obtain maximum trapped performance. The flat rate of aggregation showed that sound pressure works to compress the shape of aggregation rather than the effect of flow velocity. Then we derived the conditions to obtain a desired volume of aggregation to apply to the multi-bifurcation model of artificial blood vessel, which has repeatedly divided paths until the middle of the model from the inflow path of 2 mm to the minimum diameter of 0.5 mm, to confirm the behavior of an aggregation. Using the flow velocity of 20 mm/s, maximum sound pressure of 300 kPa, and suspension density of 0.08 μl/ml, the volume of aggregation was expected to be 0.6 mm3, which is greater than the section area of the narrow path in the bifurcation model. The result showed that the aggregation, in 50 s after the injection of the suspension, flaked off the vessel wall, flew to downstream, and was caught at a bifurcation. Finally we clearly confirmed that the aggregation blocked a path, where colored water could not penetrate to downstream.
Dynamic deformation of foot structure has been measured mainly by fluoroscopy or 3D imaging using skin markers. However, these methods require large, expensive equipment, and their measurement range is very narrow. Because of this drawback, the dynamic deformation of foot structure during steady walking cannot be measured. To measure the dynamic deformation of foot structure during steady walking, we used a flexible polymer curvature sensor (2.0 mm×20.0 mm) that is capable of convert its vending curvature to voltage. This sensor was attached to the first tarsometatarsal joint, which is a part of the medial longitudinal arch;this joint consists of the first metatarsal bone and the medial cuneiform. Twelve healthy adult males (age, 22.2±1.0 years) participated in the measurement experiment, and the flexible polymer curvature sensor was attached to their skin at the first tarsometatarsal joint. The subjects were asked to walk barefoot on a treadmill. The measurement voltage, i.e., the deformation of the first tarsometatarsal joint, showed large individual differences in the curvature changing pattern and amplitude. However, we confirmed that the deformation of the first tarsometatarsal joint changed cyclically according to the gait cycle. Moreover, the amount of deflection at the center of the attached curvature sensor was increased to 0.29 mm on average, as estimated from the range of curvature changes.
To estimate the internal structures of the patient brain, several methods map a brain atlas to a patient brain shape using some landmarks, which are selected manually from the brain shape. The determination of the correspondence between small sulci of arbitrary two brains is complex. Moreover, the relationship between the surface shape and internal structure of the brain is unclear. Therefore, even if the surface the deformed atlas is fitted to the patient brain shape, the accurate internal structures of the brain can not always be obtained. To solve these problems, this paper proposes a method of selecting landmarks to estimate the internal structures of the patient brain by deforming brain atlas. Firstly, the brain shapes are represented by a simple shape. Secondly, a small number of initial landmarks are selected manually from the contours of the approximated brain shape and the internal structures which can be identified from MR images. Thirdly, some new landmarks are generated automatically on the contours based on the initial landmarks. Finally, the brain atlas is deformed non-rigidly using these landmarks. To evaluate our method, we estimate the patient brain structure using 4 methods. From the experimental results using 10 brain images, our method can estimate the patient brain structure reliably and stably using a small number of landmarks compared with the method using the landmarks on the original brain shape.
An “active” ultra sound Doppler (USD) method was newly developed for the direct, easy and quantitative discrimination of emboli from micro bubbles in blood flow. This method is based on the measurement of the sound axial velocity of the two induced by using acoustic radiation force of ultra sound wave. This force depends on the difference of characteristic acoustic impedances between ambient fluid and emboli or micro bubbles. In the case of a micro bubble, the change of the moving velocity is larger because of a much larger difference between the characteristic acoustic impedances of the two. In order to prove the availability of active USD method, an in-vitro experiment on discrimination of emboli from micro bubbles was performed in a flow modeled after human's middle cerebral arterial flow. As model emboli, blood clot and alginate gel particle were used, and as working fluid, calcium chlorite aqueous solution and bovine blood. In the experiment, model emboli and micro bubbles were irradiated from the downstream side by ultra sound wave from commercial ultrasound diagnostic equipment being used at clinical sites. It was found that there were obvious differences of moving acceleration in the sound axial direction between micro bubbles and model emboli in the modeled blood flow which was caused by the acoustic radiation force, and that this “active” USD method had high availability for a medical diagnosis system to directly, easily and quantitatively discriminate emboli from micro bubbles flowing in human vessel.
The objective of this paper was to investigate an influence of spontaneous spike firing rates on information transmission of the spike trains in a spherical bushy neuron model of anteroventral cochlear nuclei. In computer simulations, the mixture of sub- and supra-threshold synaptic current stimuli ascending from auditory nerve fibers were modeled by a filtered inhomogeneous Poisson process modulated by sinusoidal functions, while the stochastic sodium and high- and low-threshold potassium channels were incorporated into a single compartment model of the soma in a spherical bushy neuron model. The information rates were estimated from the entropy of the inter-spike intervals of the spike trains to quantitatively evaluate information transmission in the spherical bushy neuron model. The results show that the information rates increased, reached a maximum, and then decreased as the rate of spontaneous spikes increased in which the stimulating current was set as the supra- or sub-threshold stimulus, implying a resonance phenomenon dependent on the rate of spontaneous spikes. In conclusion, a specific rate of the spontaneous spike firings may play an important role in enhancing the information transmission in the spherical bushy neuron applied by the supra-threshold stimuli.