We report on the reliability of Leave-One-Out (LOO) cross validation of a two class classifier, which classifies lesion images from false positive ones. It is known that the LOO is an unbiased estimator of generalization errors of classifiers but that it cannot estimate the deviations of the estimated errors from the true ones. In this article, we study on estimation of the deviations based on a uniform stability. We firstly demonstrate the relationship between the uniform stability and the deviation between the estimated error and the true one in simulated experiments. It was shown that the deviation became larger when the numbers of training samples of two classes were unbalanced and that the uniform stability could capture such the relationship. Secondly, we experimentally show the relationship between the uniform stability and the dimension of input data based on simulated experiments and clinical PET/CT images. It was experimentally found that the estimated error of a classifier could be improved only by increasing the dimension of input data but that the stability of the classifier became worse by the increase of the dimension.

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The measurement of axial length and the evaluation of three dimensional (3D) form of an eye are essential to evaluate the mechanism of myopia progression. We propose a method of automatic measurement of axial length including adjustment of the pulse sequence of short-term scan which could suppress influence of eyeblink, using a magnetic resonance imaging (MRI) which acquires 3D images noninvasively. Acquiring T₂-weighted images with 3.0 tesla MRI device and eight-channel phased-array head coil, we extracted left and right eye ball images, and then reconstructed 3D volume. The surface coordinates were calculated from 3D volume, fitting the ellipsoid model coordinates with the surface coordinates, and measured the axial length automatically. Measuring twenty one subjects, we compared the automatically measured values of axial length with the manually measured ones, then confirmed significant elongation in the axial length of myopia compared with that of emmetropia. Furthermore, there were no significant differences (p<0.05) between the means of automatic measurements and the manual ones. Accordingly, the automatic measurement process of axial length could be a tool for the elucidation of the mechanism of myopia progression, which would be suitable for evaluating the axial length easily and noninvasively.

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The mechanomyogram (MMG) is a recording of small vibration on the body surface due to lateral expansion of contracting muscle fibers. The present investigation aimed to determine appropriate recording area in measuring the MMG from diaphragm and to clarify its reliability using intraclass correlation coefficient (ICC) for promoting clinical application of the MMG. A single twitch contraction of diaphragm was elicited by applying electric stimulation to phrenic nerve. The MMG and electromyogram (EMG) were recorded at six different areas over the surface of thorax, i. e., each two positions on 7th to 9th intercostal space. Both MMG and EMG demonstrated excellent reliability in all the recording areas with mean ICC of 0.973. The significantly greater amplitude in both signals was observed on body surface at the intersection of the 8th or 9th intercostal space and the sagittal line on the 9th rib margin. The findings suggest that the diaphragmatic MMG and EMG are derived most appropriately from these surface areas of thorax.

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Recently, there are various studies to recognize and trace the shape of the left ventricle in the echogram. Especially speckle-tracking method is very useful to evaluate heart motion. However, most of these techniques require initial settings to indicate initial region or point of interest of the examiner. Additionally, real-time recognition of left ventricle has not been considered by the conventional researches. In this study, we propose an automatic recognition algorithm of left ventricular cavity using successive echocardiograms, which is not required any initial settings by examiner. This system plots a point in a left ventricular cavity, and then depicts the cavity automatically. We have applied this algorithm to 10 normal hearts and 60 diseased hearts. As the result, the proposed method correctly recognized 82% of left ventricular cavities throughout all of the recorded frames, which was judged by professional sonographers. Furthermore, this software was applied to real-time visualization of the cavity through analog video signal, where automatic calculation of ejection fraction was agreed with the results of conventional method by a sonographer.

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It has been reported to be difficult to differentiate Lumbar Spinal Canal Stenosis (LSS) at the L4 level and Hip Osteoarthritis (HipOA) since Macnab reported that these diseases show very similar symptoms. Although the walking on these diseases have been analyzed separately, the comparison between them has not been done yet. In this paper, the walking on thirteen normal healthy persons, nine L4 patients and eighteen HipOA patients were analyzed for disease differentiation. The walking of the subject with LED markers was captured on the treadmill. The markers are attached on acrominon, spina iliaca anterior superior, head of fibulae, lateral malleolus and the fifth metatarsal head of the subject. Motion ranges of thigh angle (corresponding to hip angle), knee angle, upper body angle, and single stance ratio by the diseased leg were picked up as the important features for the differentiation. The motion ranges of the thigh angle and the single stance ratio on HipOA patients were smaller than those on normal healthy persons, as previously reported by other researchers. The motion range of thigh angle on HipOA patients was also smaller than that on L4 patients, and statistical significant difference between L4 and HipOA patients was obtained at the ten percent significant level. The motion ranges of knee angle became small in the order of normal healthy persons, L4 patients and HipOA patients while that of upper body angle became large in the order of L4 patients, normal healthy persons and HipOA patients. With respect to the angles of knee and upper body, statistical significant difference between L4 and HipOA patients was obtained at the five percent significant level. In conclusion, the above four feature factors, especially the motion ranges of upper body angle and knee angle are effective to differentiate the HipOA and L4 patients.

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A DPC code expresses a primary disease, a complication, and procedures, etc. In 2010, 1334 hospitals use DPC codes for calculations of medical fees. Since, in the hospitals, the medical fee of each case is calculated based on one DPC code, each case must be classified into one DPC code. However, the classification is difficult in some cases because patients sometimes have various conditions. Therefore, automatic DPC code selections using machine learning are being studied. Suzuki et al. evaluated automatic DPC code selections from discharge summaries using a vector space method. However, there are general machine learning methods except for the vector space method. Hence, we must evaluate other machine learning methods exhaustively for improvement of accuracy of automatic DPC code selections. Therefore, we evaluated automatic DPC code selections from discharge summaries using naïve Bayes method, SVM, concept base method, and another vector space method which is different from the vector space model used by Suzuki et al. We considered these machine learning methods as general ones. We also focus on characteristics of each machine learning methods on automatic DPC code selections and we utilize a method which combines some machine learning methods. First, the combining method estimates confidences of the machine learning methods bases on classification scores that the machine learning methods regard as classification evidence. Next, the combining method adopts the method whose confidence is highest. We compared accuracy of the methods using discharge summaries created in 2008 fiscal year in Kyoto University Hospital. As a result, SVM classified 72.2% of the cases into correct DPC codes though the vector space model utilized by Suzuki et al. classified 64.8% into correct DPC codes. Moreover the combining method classified 76.1% into correct DPC codes. In conclusion, we achieved significant improvement.

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The aim of this study was to estimate changes in hemodynamic (systolic blood pressure and heart rate) and respiratory (oxygen uptake, carbon dioxide elimination, minute ventilation, tidal volume, and respiratory rate) responses of 26 healthy men while performing interval training with three different pause time distributions (60, 120, and 180 s) under an anaerobic threshold as a load of the exercise phase of 60 s by cycle ergometry with 10 bouts. The hemodynamic and respiratory responses in the tenth exercise phase tended to increase, compared with those in the first bout, but did not change significantly over the three sessions, with the exception of minute ventilation and tidal volume. Responses were not influenced by the length of the pause phases. However, we recommend setting the pause phase at more than 120 s because biogenic stress is still high at 60 s, and may lead to the appearance of breathlessness owing to minute ventilation at 60 s, which was significantly increased, compared with the others.

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As handheld tool navigation including surgical navigation, presenting tactile information is required in addition to the visual information. Especially, to present virtual tactile distribution at the holding parts of the fingers according to the contact condition between the tool and the important object such as organs enables users to minimize injuring them. However, spatially transparent stimulation which can superpose the tactile distribution at the holding parts without mediating the device has not been achieved. This study proposed a spatially transparent electrotactile display by using sensory shift which is caused by transcutaneous electrical nerve stimulus (TENS). We achieved tactile superposition by using the nerve anatomy and TENS. For developing the tactile Augmented Reality (AR) navigation system, tactile representation of the force vector which acts on the tool was proposed. The control of pulse rates at two electrodes enabled users to perceive the direction of the force vector. The subjective experiment letting a subject manipulate a tool without invading it into virtual obstacles was carried out. The result of the experiment showed that users could avoid invading virtual obstacles with less than 3mm depth.

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Complex fractionated atrial electrograms (CFAEs) have been reported as effective targets for ablation in the treatment of atrial fibrillation. CFAEs are defined as atrial electrograms with a very short cycle length (<120ms) or continuous electrical activities. However, methods for detecting CFAE automatically and quantitatively using intracardiac electrograms have not yet been established. The purpose of this study is to propose a method to automatically detect CFAE by detecting atrial electrograms that have either a short cycle length (<120ms) or continuous electrical activities, as well as to confirm the effectiveness of the method using clinical data. The measured electrograms were squared in order to amplify electric potential differences between the atrial electrograms and continuous electrical activities. This method detects CFAE by counting the numbers of times the squared electrogram exceeds one of two thresholds. The first threshold for detecting atrial electrograms with a short cycle length (<120ms) is generated from the variance of the electrograms. The second threshold for detecting continuous electrical activities is obtained from the maximum value of atrial electrograms multiplied by a reduction factor. We analyzed 100 electrograms consisting of 62 CFAEs and 38 non-CFAEs, measured from eight persistent atrial fibrillation patients, with durations ranging from 4 to 32 s. It was confirmed that the proposed method could automatically detect CFAE and non-CFAE with 93% accuracy (positive predictive value: 97%, negative predictive value: 88%). In conclusion, the result of this study indicates that the proposed method is effective for automatic CFAEs detection. We found that it is feasible to use the proposed method for automated CFAEs detection without the need for an operator's judgments during the treatment of persistent atrial fibrillation. Further studies are warranted to determine the clinical significance of the proposed method.

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We quantified exercise capacity using admittance plethysmography. We simultaneously measured the tissue blood volume change in the legs using admittance plethysmography and near-infrared spectroscopy (NIRS) during graded exercise on a bicycle ergometer and compared both signals. We also compared the normalized tissue blood volume change according to the maximum blood volume change (NTM) with the total workload during graded exercises, and studied whether NTM is a useful index for evaluating exercise capacity. Furthermore, we compared the maximum tissue blood volume change with a bioelectrical impedance (BI) index of skeletal muscle volume, and investigated whether it is possible to estimate the maximum tissue blood volume change using the BI index. We found that both admittance plethysmography and NIRS showed that tissue blood volume increased during exercise and that NTM correlated significantly with total workload (p<0.01). Moreover, the maximum tissue blood volume change correlated significantly with the BI index (p<0.01). Our results suggest that admittance plethysmography may be useful in the quantitative evaluation of exercise capacity.

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SPECT study provides local pulmonary function information. However, the spatial resolution of SPECT is low, and it is difficult to point out local ventilatory impairment. In this study, we propose the registration method for analyzing pulmonary function by using high-resolution CT images. The high quality registration is necessary to know pulmonary function. But the shapes of the lung in CT images are greatly different between inspiration and expiration CT images. Therefore, we performed two phases of registration of global matching and local matching. We created a displacement map using displacement vector. And, we evaluated our method by use of the cases of CT images and SPECT images.

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Ischemia is a main cause for many cardiovascular diseases, and can be caused by increases in the vascular resistance at the artery (R_a), as a result of a decreased artery diameter. Although R_a is useful for cardiovascular diagnoses, its evaluation was difficult in the past because R_a cannot be measured directly. The purpose of this study is to construct and verify a method for the quantitative evaluation of R_a for the future application of cardiovascular diagnosis. R_a cannot be measured directly; therefore, we developed a method for identifying R_a using the Aortic blood-pressure (AoP) and the blood-flow volume (Flow), which are measurable. In this method, we use a mathematical model that represents the characteristics of the vascular dynamics. Here, R_a is a parameter in the model, and is identified using the least square method applied to the measured AoP and Flow volume. Thus, R_a can be evaluated quantitatively as a reflection of the actual vascular resistance at the artery. Through animal experiments on seven pigs, we verified that R_a reflects the actual vascular resistance at the artery. First, the femoral arteries were exposed in order to install a flow-meter probe and a catheter for AoP measurement. Next, the femoral artery near the flow-meter probe was intentionally stenosed. As a result, the identified value of R_a significantly increased (P<0.05) by a factor of 3.58 (from 0.233±0.151 to 0.836±0.654 [mmHg min/ml] ). This result indicates that the identified resistance, R_a, reflected the vascular resistance at the artery. In conclusion, we showed it is possible to realize an evaluation method for vascular resistance at artery that can improve cardiovascular diagnoses.

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The aim of this research was to evaluate the autonomic nervous reaction using photoploethysmography under the emotional stimuli. Twenty healthy adults (11 males and 9 females) with a mean age of 25.0±5.0 were assessed for their psychosomatic states using Cornell Medical Index (CMI) and classified into two groups: group I (healthy) and II-IV (neurotic tendency). The photoplethysmography under emotional stimuli using the audiovisual video footages for 40 seconds and during recalling the contents of the footages soon after the stimuli for 180 seconds was measured. These series were repeated three times. The emotional stimuli consisted of "positive stimuli" and "negative stimuli". The "positive stimuli" such as relaxed and pleasant stimuli could evoke a positive feeling, while the "negative stimuli" such as unpleasants #1 (human-relation problem) and #2 (fear) stimuli could evoke a negative feeling. Pulse waves from photoplethysmography were analyzed for estimating the pulse wave amplitude, reflection index (RI). and pulse wave length, and these values of two groups were compared using analysis of variance (ANOVA). The results showed that the pulse wave amplitudes of group I under and after the positive simuli were significantly larger than the amplitudes under and after the negative stimuli, respectively. On the other hand, there was no obvious difference of the pulse wave amplitudes of group II-IV between the positive and negative stimuli. RI of group I during and before the stimuli was smaller than the base line, and RI under the unpleasant #2 stimuli was smallest in all the stimuli. However, RI of group II-IV under the unpleasant #2 stimuli was largest in all the stimuli. The pulse wave length under the unpleasant #1 stimuli was significantly larger than the other stimuli, and the pulse wave length after the stimuli was significantly smaller than the base line. These results suggested that the autonomic nervous reaction under emotional stimuli would be regulated based on the psychosomatic states.

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In the present study, we investigated the mechanism of the central nervous system to adapt the finger movement to the stable force field overlapped on the unstable force field. In the experiments, we analyzed after-effects on adaptation of a point-to-point index finger movement to a static force field (SF), divergent force field (DF) and composite force field (CF), in which the SF overlapped on the DF. Experimental results indicated that the adaptation to the SF was achieved by the generation of counteracting forces through the feed-forward motor command, whereas the modification of the limb impedance was utilized for the unpredictable interaction in the DF. Moreover, it was suggested that the adaptation to the CF was operated by the generation of counteracting forces in the feed-forward manner rather than the modification of the limb impedance.

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In Japan, 33.4% of traffic fatalities in 2008 were pedestrian, and 69.2% of pedestrian fatalities were over 65 year old people. Establishment of the evaluation method for the human risk factor related to traffic accident is not only useful for prevention of traffic accident but also useful for the evaluation of light decline of higher brain function that is difficult to notice symptoms by themselves. In this paper, as an application of a VR technology for a traffic safety, we developed the walking environment simulator system (Pedestrian environment simulator) that combined a motion capture system and treadmill. Using this simulator, the human factor related to elder pedestrian traffic accidents was examined. In the results, we confirmed that the rate of traffic accident of elder pedestrian was larger than that of younger pedestrian. Especially, the traffic accident rate was increased in the condition of no engine sound. It became clear that one of the risk factor of elder pedestrian's traffic accident was the decline of cognitive function related to the recognition of the approach speed. The evaluation method for elder pedestrian traffic accidents in this paper might be useful as a screening method in order to find the decline factor of total function that includes perception, cognition, estimation and action.

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The degeneration of articular cartilage impairs primal functions such as load transfer and distribution, and consequently, harms activities of daily life seriously. Evaluation of the mechanical property will be of help in clinical diagnosis of the degenerative disease of cartilage. Articular cartilage shows the depth-dependent laminar structure. The tissue composition and its microstructure are involved in the cartilage degeneration. Thus, the establishment of an evaluation method considering its microstructure is favorable for the accurate evaluation of the mechanical property. To examine the depth-dependent mechanical property that is difficult to be estimated by experiment, this study proposes a model-based evaluation method of the cartilage material property by means of the mechanical model reproducing tissue microstructure properties. Using the present model, the mechanical properties of normal and enzymatically degenerated cartilage of the bovine femoral heads were identified, and the degeneration in the medial (load-supporting) and the lateral (non load-supporting) regions were investigated. The elastic modulus was decreased by collagenase-treatment at both regions throughout all layers of cartilage. The mobility of interstitial fluid in tissue was increased by the treatment at both regions.

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Repetitive Transcranial Magnetic Stimulation (rTMS) is effective for intractable diseases of the nervous system. As the effects of rTMS last only several hours, rTMS therapies need to be continued daily. Under present circumstances, it is difficult to use rTMS in patients' home, because only experienced physicians in limited hospitals can use the expensive and complicated rTMS system. Therefore, we developed a magnetic navigation system for home use of rTMS. The proposed system uses inexpensive and small magnetic sensors; hence it is suitable for home use. By using the proposed method, even people who have no medical knowledge and technique can easily navigate the coil to the optimal position preliminarily specified by expert physicians. Our system needs to collect some dataset which consists of magnetic field and the corresponding position of the coil at the patients' initial visit. Since it is bothersome to collect a large number of dataset, we reduced the dataset by approximation using multi-regression analysis.

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Pulse rates obtained from photoplethysmography (PPG) sensors are important for monitoring cardiovascular condition, especially during exercise, because it is a simple, low-cost, and easy to use. However, it is difficult to precisely count pulse rates during exercise because PPG is sensitive to body movement. When a motion artifact occurs, changes in vascular volume cause noise. Differences in cutaneous blood supply to different anatomic regions are apparent from the literature. Here, we consider motion artifacts as related to anatomical measurement sites and light sources. In order to eliminate the motion artifacts, we compared the signal obtained from green PPG to that from infrared PPG with related to different anatomical sites during body movement. PPG were collected simultaneously from three anatomical sites: upper arm, wrist and finger. Eleven young healthy subjects without any indication of peripheral arterial disease were recruited to participate in the experiment. To produce artifacts, the subjects were asked to walk at a pace of 4 km/hr on the treadmill. 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 results, the magnitude and variability of the green PPG have different nature to those of the infrared PPG. In a resting state, the maximum magnitude of green PPG was located at upper arm, but that of infrared was located at wrist. During walking, all site of infrared PPG were more sensitive to motion artifact than those of green PPG. These results suggested that green PPG reflected different vascular distribution to infrared PPG. Additionally, the green PPG from the upper arm showed less error rate than did the peripheral one. Therefore, the green PPG located at the upper arm may be a suitable for pulse rate monitoring during walking.

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Recently, magnetic resonance diffusion tensor imaging (MR-DTI) has been used to analyze the structure and the function of the human brain. MR-DTI is a noninvasive method of measuring the diffusion phenomenon of water molecules in vivo. Tractographies using MR-DTI give the information of nerve fibers. They are promising for diagnoses of the disorder that has abnormalities in cerebral nerve fibers and analyses of functional connectivity among activated areas. In general, tractographies are able to track nerve fibers between near areas. However, it is difficult to track nerve fibers between distant areas due to partial volume effect in nerve fiber crossing areas. In this paper, we proposed a new tractography by searching minimum curvature deviation in fiber crossing areas using the trajectory of before and after the crossing areas. First, the method was evaluated by simulation images that illustrate the bilateral visual cortex through the corpus callosum. Subsequently, the method was applied to the real data. The results demonstrate the usefulness of the proposed method.

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Advanced clinical diagnosis of a cardiac function requires quantitative evaluation of myocardium deformation. It is however still challenging to quantify myocardium deformations due to noises caused by entire cardiac movements and limits of imaging modalities. Here, we propose a novel method for gaining strain rates of myocardium with better spatiotemporal accuracy compared with conventional methods. The proposed method is based on the theory of geometrical constraints which provides a deformation gradient tensor to relate undeformed to deformed configuration of an object. The deformed configuration of the left ventricle was estimated from the present configuration and velocity data obtained by phase contrast (PC)-MR imaging. The proposed method has two major advantages. First, because of no need to use temporally sequential images in estimating velocity as in conventional methods, strain rates calculated from the proposed method are basically free from temporal resolutions of imaging modalities. Second, because of unnecessity of spatially interpolating data, calculated strain rates retain the same spatial resolution as PC-MR images. On comparing a spatial field of strain rates obtained with the proposed method to that with a conventional method, we found that the proposed method was capable of providing spatially smoother field of strain rates in the left ventricular myocardium.

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Waist circumference as an estimate value of the visceral fat is measured for the diagnostic criteria of the metabolic syndrome. At the medical examination, waist circumference is usually measured with tape measure manually. Thus, obtained values should include non-neglective error. Additionally, the values of waist circumference will be personal information not to be known to others and it is also discomfort for women that someone touches their abdomen area. From this point, we have developed the new system for the non-contact measurement of abdominal cross section and waist circumference using a laser displacement meter. In this system, the laser displacement meter was attached at the waist level on the fulcrum which turned around the body segment. By the measured distance between the body surface and the laser sensor, the length from the center of the platform to the body surface was calculated by every small angle of 0.72degree so as to calculate the waist circumference and an abdominal cross-section. The designed system consists of pulse motor driving controller, distance measurement amplifier and the personal computer system for the operation of measurement and the graphical indication of data. The subjects were stood at a standstill position at least three seconds on the platform during the measurement. For the evaluation of the accuracy of the system, the five known circumferences with seven different cross-sections were measured. The linear correlation between the measurement value and the known data (y=1.0002x, R²=0.9998) was obtained within the 0.6% error range. The measured waist circumferences (60 to 100 cm) by 34 subjects were compared to manually obtained values. The differences were about 2-3 cm (within 3.5% error range of circumference).

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We have measured the body surface perception threshold using the quantitative evaluation system for pain (Pain Vision®). This system produced the increasing electrical stimulation (frequency: 50 Hz, pulse width: 0.3 ms) without causing of pain. The concept of pain quantification is to compare the magnitude of the subject's pain to the magnitude of comparative pain-free stimulus to actual pain. The pain degree was calculated from pain evaluating stimulation current and perception threshold. The electrical current perception threshold (CPT) is also available for the evaluation of the peripheral nerve function. The purpose of this study is to determine the standard value of CPT in healthy person as the control CPT range for evaluating the CPT change due to peripheral neuropathy. CPT were measured on the upper limbs (forearm) and the lower limbs (tarsal, and Achilles' tendon) of both of normal group (from 20's to 80's; total number 1658) and diabetes mellitus group (from 40's to 80's; total number 829). As a result in both of male and female of normal group, the average CPT of the lower limbs was 2-3 times higher than that of upper limbs and the average CPT increased by aging. In comparison, the average CPT in 80's was 1.5 times to that of 20's. The average CPT obtained from diabetes mellitus group showed significantly higher levels than normal group. It was considered that the influence of the diabetic neuropathy reflected with the change in CPT. In particular, the changes in upper limb CPT were clearly larger than that of lower limb in every generation. Diabetic neuropathy frequently appears in lower limbs. However, this study suggests that the change in CPT should be focused its attention on the upper limbs.

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Motion-defined pattern perception includes two perceptions: motion and pattern perception. The purpose of this study was to clarify the difference in time courses and activated areas between motion detection and pattern perception. Psychophysical experiments were carried out by employing a random dot kinematogram to ask the direction of a coherently moving dot in a core rectangle toward upper left or lower right (a direction discrimination task), and the shape of that rectangle oblong vertically or horizontally (a pattern discrimination task) by varying dot velocity in four levels (14.4, 28.8, 43.2 and 57.6 deg/s). When the stimuli were presented in the lower half of visual field, the mean correct rate of ten participants for both motion and pattern was larger than 0.75 (the psychophysical threshold of perception) at the velocity of 14.4 deg/s, whereas at the velocity of 43.2 deg/s, only that of motion perception exceeded the threshold. When the magneto-encephalogram (MEG) and visual evoked potential (VEP) were measured with similar stimuli, the root mean square (RMS) of MEG difference between 14.4 deg/s and 43.2 deg/s was explicitly elevated at the latency from 250 ms to 290 ms. This result was consistent with those in the previous study, demonstrating that the peak of VEP at around 290 ms were a common phenomenon elicited by every type of figure perception. The multi dipole (2-dipoles) estimation of MEG at this latency revealed that the activated areas for the pattern perception were located in both ventral and dorsal portions of the occipital cortex, while the motion perception activated the dorsal portion of occipital cortex alone.

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Stochastic resonance (SR) is a phenomenon whereby detection of sub-threshold signal is improved by additive background noise in nonlinear systems. It has been unclear how this phenomenon is affected by the characteristics of background noise. In this paper, we investigate the effects of background noise characteristics on information transmission in a realistic hippocampal CA1 neuron model, i. e., the effect of input locations of the background noise and the influence of power spectra of the background noise. Using the computer simulation, the random sub-threshold input signal generated by a filtered homogeneous Poisson process was applied to a distal portion of the apical dendrite, while the background noise having a 1/f^β(β=0, 1, 2) power spectrum generated by a fractional integration was further applied to a variable location to investigate the effects of background noise input location on information transmission. Our results showed that SR was observed as the information rate reached a maximum value for optimal noise amplitude. The results also showed that the background noise input location and the coefficient β did not alter the maximum information rate generated by SR. The noise amplitude required to the maximum information rate increased when the noise input location was set at distal or the coefficient β was approached to zero from two. It is concluded that the variance of the noise having a frequency component of less than 200 Hz can play a key role in the information processing of sub-threshold signal transmission in the hippocampus.

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Near-infrared spectroscopy (NIRS) is intensively used for measuring changes in muscle oxygenation during dynamic and static exercises, especially in the field of exercise physiology. In general, volumetric blood flow rate is associated with significant changes in the velocity of blood flow in muscles during dynamic exercise. However, it remains unclear how measurements of hemoglobin concentration by NIRS are influenced by changes in blood flow or velocity in the muscular beds. It is important to determine this relationship during muscular contractions, because measuring oxygen consumption in the tissue is of paramount importance for understanding the relationship between muscular activity and energy expenditure and between oxygen delivery and oxygen utilization. Here, we assessed the relationship between changes in hemoglobin concentration and blood flow velocity in an in vitro NIRS experiment, which the relationship should contribute to explain the oxygen dynamics in the vascular beds and the contracting muscular tissues. We found that the changes in hemoglobin concentration that measured in this experiment were independent of the increase in blood flow velocity. Our results support those of the several studies showing that changes in deoxyhemoglobin concentration measured by NIRS reflect the changes in arteriovenous oxygen difference in muscle tissues at rest and during exercise.

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The purpose of this study is to develop a computer aided surgical planning system of acetabular cup with haptic device for total hip arthroplasty. In the preprocessing process, this system determines 3-dimensional safety-zone and critical-zone for cup placement with various criteria, and generates the reaction force at an each vertex of the grid map. In the planning phase, the system enables surgeons to feel the reaction force for guiding to the safety-zone. In the experiments, we used primary and secondary osteoarthritis cases and confirmed that this system could display the reaction force real time and manipulation cursor was guided properly.

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Magnetic Resonance Elastography (MRE) is a technique for quantitative and noninvasive assessment of tissue elasticity. MRE is often described as image-based palpation that can be used to characterize disease because the mechanical properties of tissues are often dramatically affected by the presence of disease processes. MRE pulse sequences obtain shear wave images by synchronizing motion sensitized gradients (MSG) with an external vibrator. A quantitative shear modulus map is calculated from the shear wave images. However, the magnitude property of the external vibrator and nonlinearity of the imaged object often induce unwanted higher harmonics that distort the shear wave images and impair the estimation of the elastic modulus. In this study, we optimize the MSGs to minimize the contribution of higher harmonics to the shear wave images and therefore improve the accuracy of shear modulus estimation. Simulation and phantom studies were performed to confirm the performance of the proposed MRE pulse sequence. The results show that the optimized MSG is able to acquire single frequency shear wave images even when large amplitude harmonic waves are present in the imaged object.

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The purpose of this study was to distinguish the changes of MR signals during relaxation and contraction of muscles. First, MR images were acquired in relaxation and contraction states. The subject clasped his hands in relaxation state and unclasped in contraction state. Next, the images were segmented using mixture Gaussian distributions and EM algorithm. Finally, we evaluated statistical values gotten from mixture Gaussian distributions. As a result, mixing coefficients were different during relaxation and contraction. The experimental results indicated that the proposed analysis has the potential to discriminate between two states.

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In this study, we attempted to develop a wearable motion measurement system and to propose a quantitative judgment method of walking independence in poststroke hemiplegic patients based on information of relative angles. The system was consisted of three sensor units with a tri-axial accelerometer and three gyroscopes, a transmitter, a buttery and a personal computer with a receiver. The sensor units were fixed to the subject's waist and both of thighs, respectively. 35 hemiplegic patients participated and performed 10 m walking test. 20 subjects were able to walk independently and the others could only walk under supervision. As criterion indexes for judgment of walking independence, walking cycle, ratio of extension-flexion time, excursion, their coefficients of variance, regularity of angle patterns, dependency between waist and thigh angles were calculated from information of relative angles. The analysis showed that it was difficult to classify the independent group and the supervised group with each criterion index. In almost all supervised subjects, however, either of those criterion indexes deviated from the standard range of independent group. Our proposed quantitative judgment method of walking independence consisted of eight criterion indexes, which were selected by their test sensitivities and positive predictive values. The subject was judged to be a walk under supervision when two criterion indexes or more were positive. As a result, the proposed method classified 33 subjects correctly. Our results suggest that the proposed system and judgment method of walking independence can be very useful to assess the independence measure for walking quantitatively.

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A measurable depth of the blood glucose level by using photoacoustic spectroscopy (PAS) was discussed experimentally in order to improve detection sensitivity. Since a measurable depth of the PAS based on a modulation frequency of the chopped light irradiated to a sample, the relationship between modulation frequency and the thickness of a sample was evaluated. In our experiments, the photoacoustic detector consisted of an acoustic resonant pipe and an optical microphone, and a two-layer model composed of silicone sheets with the different optical absorption were used. We varied the thickness of the upper-layer for the two-layer model from 0.50 to 5.00 mm at each modulation frequencies to investigate the relationship between the measurable depth and the modulation frequency. As results, it is shown that the measurable depth was 2-3 mm with modulation frequency of 1.6-1.9 kHz. Furthermore, the reason for the measurable depth to be deeper than the thermal diffusion length of a sample was discussed. From these analyses of thermoelastic wave, the relation between the photoacoustic signal propagation and the measurable depth in a tissue was clarified.

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As induction heating and RFID, both of which emit intermediate-frequency magnetic fields (IMF; 300 Hz-10 MHz), have been in wide use recently, possible side-effects of IMF on biological objects have become our major concerns. In this study, we aimed at clarifying possible influence of IMF on germination and growth of white radish sprouts. Two patterns of exposure to IMF (25 kHz, 10 μT) were studied. 1) Exposure before seeding for 100 hrs (group 1). 2) Exposure from seeding for 48 hrs during which 85% or more of seeds germinate (group 2). 3) Exposure to an environmental magnetic field (about 0.14 μT) (control group). Root and stalk lengths at 76 or 168 hrs after seeding were measured. Compared with the control group, the duration between seeding and germination did not affect germination ratio in any of the two groups. However, the average root length of group 2 was 1.28 times longer than control group (p<0.05 vs control). In conclusion, it is suggested that exposure of plant seeds to IMF between seeding and germination would possibly enhance productivity by decreasing cultivation time owing to accelerated growth rate of roots.

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We studied the possibility of detection of sleep apnea or hypopnea events from photoplethysmography (PPG) wave variation patterns during sleep. In three patients with suspected sleep apnea syndrome, polysomnography (PSG) and the PPG wave were measured simultaneously during sleep. The characteristics of the PPG wave variation patterns in apnea or hypopnea events detected by PSG were investigated. It was found that pulse rate increases and pulse wave amplitude decreases during apnea or hypopnea events, and the respiratory component of heart rate variability has a tendency to decrease before the apnea or hypopnea events. Also, compared to hypopnea, the ratio of the pulse rate is higher, the reduction of the pulse amplitude is more significant, and the decrease of the degree of respiratory variation component in the apnea event is greater. We devised the apnea/hypopnea detection algorithm using these characteristics and evaluated its effectiveness.

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In general, the sinc function is the standard RF pulse employed in MRI studies. In the present study, we experimentally produced “the original function” by extending the Fourier cosine transform to the sinc-Gaussian function. Theoretic slice profiles obtained using the original function showed a greater improvement in the rectangular shape compared with the sinc function. As to the physical evaluation performed with 1T-MRI clinical equipment, the suppressed decrease in Contrast to Noise Ratio was higher with the original function than the sinc function in the volunteer head image multi-slice evaluation. Thus, all the results from the simulation and the clinical equipment evaluation demonstrate that the original function can improve the quality of MRI images even with shorter Echo Time.

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In recent years, wearable technology has been advanced for the purpose of physiological monitoring system during daily life. However, conventional compact and lightweight sensors are expensive to use in the field of wearable monitoring, such as walking rehabilitation. This paper presents compact, lightweight, and inexpensive thin-film force sensor for wearable monitoring system. The thin-film force sensor requires a “puck” that is placed on the sensing area to ensure that the entire load path goes through this area. However, heterogeneous load distribution may appear on the sensor depending on the material of the puck. The difference between the outputs of the sensor using aluminum puck upon the application of surface and point forces was less than that of the sensor using PET puck. This result suggested that rigid materials are suitable for puck, thus we utilized thin-film force sensor with an aluminum-puck for planter pressure measurement to estimate ground reaction force. The performance of the thin-film force sensor was confirmed equivalent to that of the force plate. It is expected that a simple and inexpensive system to evaluate daily movement behavior has been developed.

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We have developed a novel technique for modeling the realistic lung microstructure using phase-field method. In the phase-field method for the lung microstructure, the state (air and tissue) of a system is measured with an order parameter and the time-evolutions of the order parameters in the system, a tissue initially including seeds of the air, are obtained by solving the time-dependent bistable reaction-diffusion equations modified from the Allen-Cahn equation. The field of the order parameters is reconstructed as the 3D lung microstructure model by using the binalized slice images with a certain threshold of the order parameter between the two states (air and tissue) on the binalization. We found that irrespective of the number of the initial seeds, the results demonstrate isotropic evolution of alveolar regions (air) from the initial seeds, and the alveolar regions came closer with evolution, but were never merged because of the presence of alveolar wall (tissue). A further evolution of alveolar regions develops into spatially compartmentalized pore structure, which appeared to be similar to a natural lung. Variations in the number of, and the shape of the initial seeds, and the threshold of the order parameter for binalization result in various patterns of the ductal porous structure (i. e., alveolar duct or alveolar sac), satisfying the experimentally-obtained mean alveolar volume and mean alveolar wall thickness. Furthermore, the radial distribution function calculated from the centroids of alveoli were saturated to one without any significant peaks when the inter-alveolar distance exceeds a certain value, indicating that the alveoli in our model are disorderly distributed and repel each other with a certain distance. In conclusion, those results demonstrate that the method developed here is the promising method for parametric control and anatomically realistic production of lung microstructure model.

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We developed a “ubiquitous” healthcare system using active tag technologies. Our system does not require any kind of PC operation, and the workload borne by users is low. In addition, we developed a data browsing terminal (called the Kiosk terminal) for our system. The terminal also uses active tag technologies and does not require any keyboard or mouse operation to browse data. We are currently conducting a field trial of our system in Zamami village, Okinawa, supported by the Ministry of Internal Affairs and Communications. Unlike another system using USB data transmission technologies, our system can collect vital data without fail. Heavily used facilities can be revealed by analyzing the usage frequency of active tag data receivers, and such knowledge is important for optimizing the system. After the installation of Kiosk terminals, the average number of steps per day of Kiosk users, as recorded by their pedometers, increased by more than twice that before installation.

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We previously reported (2009) that EEG data in the particular θ band might provide the characteristic difference between healthy adults and dementia patients. Therefore, in the present study, we recorded EEG in all subjects (healthy controls and dementia patients) during Sternberg task, and made EEG topography based on the power spectrum values calculated in the θ band ranging from 5.4 Hz to 6.3 Hz. In healthy elderly, EEG topography showed maximal θ activation in the central electrode (Cz). In mild cognitive impairment (MCI) patients, EEG topography also showed θ activation at Cz with less prominent activity in the frontal area (Fz, F3 and F4). In dementia, there was no common trend of EEG topography compared to healthy elderly and MCI patients. These results suggest that MCI patients are belong to the transient state between normal aging and dementia. Therefore, we conclude that EEG topographical map in the particular θ band is an electrophysiological marker of early diagnosis for dementia.

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