Language：English   Publishing type：Research paper (international conference proceedings)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：HINDAWI LTD  

Cortical dipole imaging has been developed to visualize brain electrical activity in high spatial resolution. It is necessary to solve an inverse problem to estimate the cortical dipole distribution from the scalp potentials. In the present study, the accuracy of cortical dipole imaging was improved by focusing on filtering property of the spatial inverse filter. We proposed an inverse filter that optimizes filtering property using a sigmoid function. The ability of the proposed method was compared with the traditional inverse techniques, such as Tikhonov regularization, truncated singular value decomposition (TSVD), and truncated total least squares (TTLS), in a computer simulation. The proposed method was applied to human experimental data of visual evoked potentials. As a result, the estimation accuracy was improved and the localized dipole distribution was obtained with less noise.

DOI： 10.1155/2016/8404565

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：HINDAWI LTD  

Cortical dipole imaging has been developed to visualize brain electrical activity in high spatial resolution. It is necessary to solve an inverse problem to estimate the cortical dipole distribution from the scalp potentials. In the present study, the accuracy of cortical dipole imaging was improved by focusing on filtering property of the spatial inverse filter. We proposed an inverse filter that optimizes filtering property using a sigmoid function. The ability of the proposed method was compared with the traditional inverse techniques, such as Tikhonov regularization, truncated singular value decomposition (TSVD), and truncated total least squares (TTLS), in a computer simulation. The proposed method was applied to human experimental data of visual evoked potentials. As a result, the estimation accuracy was improved and the localized dipole distribution was obtained with less noise.

DOI： 10.1155/2016/8404565

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

In the existing walking support system, the range of detection is limited, and it is very difficult to detect obstacles such as a step or a hollow. Therefore, we aim at the development of a new walking support system for a visually-impaired person detecting neighboring obstacles by making use of a smartphone which is a high-performance portable information terminal. In this study, we have developed a walking support system combining the orientation sensor of the smartphone and a small distance sensor at the first stage. When we investigated its precision in detecting an obstacle, it was found that the system could detect obstacles which disturbed the walking of a visually-impaired person such as a step and a wall. We will find an appropriate key to detection to improve the detection precision of the system and make further improvements in the system by trial experiments in the future.

DOI： 10.1109/EMBC.2015.7319929

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DOI： 10.17654/FJECMar2015-053-069

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

To provide speech prostheses for individuals with severe communication impairments, we investigated a classification method for brain computer interfaces (BCIs) using silent speech. Event-related potentials (ERPs) were recorded using scalp electrodes when five subjects imagined the vocalization of Japanese vowels, /a/, /i/, /u/, /e/, and /o/ in order and in random order, while the subjects remained silent and immobilized.
For actualization, we tried to apply relevance vector machine (RVM) and RVM with Gaussian kernel (RVM-G) instead of support vector machine with Gaussian kernel (SVM-G) to reduce the calculation cost in the use of 19 channels, common special patterns (CSPs) filtering, and adaptive collection (AC). Results show that using RVM-G instead of SVM-G reduced the ratio of the number of efficient vectors to the number of training data from 97% to 55%. At this time, the averaged classification accuracies (CAs) using SVM-G and RVM-G were, respectively, 77% and 79%, showing no degradation. However, the calculation cost was more than that using SVM-G because RVM-G necessitates high calculation costs for optimization. Furthermore, results show that CAs using RVM-G were weaker than SVM-G when the training data were few. Additionally, results showed that nonlinear classification was necessary for silent speech classification.
This paper serves as a beginning of feasibility study for speech prostheses using an imagined voice. Although classification for silent speech presents great potential, many feasibility problems remain. (C) 2013 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.asoc.2013.10.023

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

The spatial resolution of scalp potential mapping is limited because of low conductivity of a skull. Cortical dipole layer imaging has been proposed as a method to visualize brain electrical activity with high spatial resolution. According to this method, about 100 electrodes were required to measure whole brain electrical activity. In the present study, we investigated simplified cortical dipole imaging with a small number of electrodes. The density of electrodes and the spatial resolution are in a trade-off relation. Thus, the number of electrodes was reduced by limiting the visualization region of interest, without lowering the density of electrodes. Moreover, independent component analysis was applied to the multiple signal sources to extract an attention signal from the other signals and noise. In simulation, even if the number of electrodes was reduced to 25, the obtained results were almost equivalent to the case with whole brain electrodes. The proposed method was applied to human experimental data of movement-related potential. We confirmed that the proposed method provided high resolution cortical dipole imaging with localized distribution.

DOI： 10.1109/EMBC.2014.6944731

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：日本生体工学会  

DOI： 10.11239/jsmbe.51.24

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Cortical dipole imaging has been proposed as a method to visualize electroencephalogram in high spatial resolution. We investigated the inverse technique of cortical dipole imaging using a truncated total least squares (TTLS). The TTLS is a regularization technique to reduce the influence from both the measurement noise and the transfer matrix error caused by the head model distortion. The estimation of the regularization parameter was also investigated based on L-curve. The computer simulation suggested that the estimation accuracy was improved by the TTLS compared with Tikhonov regularization. The proposed method was applied to human experimental data of visual evoked potentials. We confirmed the TTLS provided the high spatial resolution of cortical dipole imaging.

DOI： 10.1109/EMBC.2013.6610772

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

To provide speech prostheses for individuals with severe communication impairments, we investigated a classification method for brain computer interfaces (BCIs) using silent speech. Event-related potentials (ERPs) obtained when four subjects imagined the vocalization of Japanese vowels, /a/, lit, /u/, /e/, and /o/ in order and in random order while the subjects remained silent and immobilized were recorded using Ill scalp electrodes and 3 reference electrodes. Regarding detection of the imagined voice, some problems occurred by which the related brain geometries and suitable electrodes for classifications differed between subjects. To overcome these problems, we used an adaptive collection that divided ERP data into small elements, performed evaluation relative to the elements, and selected better elements for classification. In earlier reports of studies using the common spatial patterns (CSPs) filter and support vector machines (SI/Ms), the classification accuracies (CAs) were 56-72% for the pairwise classification /a/ vs. /u/ in the case of 63 channel EEG measurement In this study, the CA was improved to 73-92% using the adaptive collection. According to the CA, 19 channel measurements were worse than 111 channel measurements, but 63 channel measurements were slightly worse that 111 channel measurements. Using 63 channel measurements, 73% of CA was achieved for all pairwise combinations of the five vowels. The average of the CAs was 85%. These results show that the proposed method exhibited great potential for use in classification of imagined voice for a speech prosthesis controller.

DOI： 10.1109/CIRAT.2013.6613816

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：Institute of Electrical Engineers of Japan  

In clinical situations, the objective evaluation of somatic sensations is expected without a patient's subjective opinions to reduce social problems such as those related to lawsuits for nerve injuries or malingering. In this study, the somatosensory evoked potential (SEP) using the mechanical stimulations of the tactile sensation was measured and analyzed in spatiotemporal domains. The cortical potential mapping projected onto the realistic-shaped model was estimated to improve the spatial resolution of the SEP maps by application of cortical dipole layer imaging. The experimentally obtained results suggest that the spatiotemporal distributions of the SEPs reflect the differences for positions, strengths, and patterns of somatosensory stimulations. © 2013 The Institute of Electrical Engineers of Japan.

DOI： 10.1541/ieejeiss.133.169

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical Engineers of Japan  

The purpose of this study is to investigate the efficient stroke patterns of manual wheelchair propulsion in the repetition operation. The state of the muscle fatigue was evaluated using the averaged rectified value and the mean power frequency of 5-channel surface electromyograms of the upper arm and the chest. In addition, the propulsion efficiency of was estimated from the driving torque and total muscle activities. Four different stroke patterns of arcing, semicircular, single looping over propulsion, and double looping over propulsion were examined by 6 healthy male subjects. The experimental results of the subjects with muscle fatigue tendency suggested that the stroke pattern of the semicircular which draws locus an oval was the most effective in four stroke patterns because of low muscle fatigue and high proportion efficiency. © 2012 The Institute of Electrical Engineers of Japan.

DOI： 10.1541/ieejeiss.132.1798

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

The objective evaluation of somatic sensations is expected without a patient's subjective opinions to reduce social problems such as those related to lawsuits for nerve injuries or malingering. In this study, the somatosensory evoked potential (SEP) using the mechanical stimulations of the tactile sensation was measured and analyzed in spatiotemporal domains. The cortical potential mapping projected onto the realistic-shaped model was estimated to improve the spatial resolution of the SEP maps by application of cortical dipole layer imaging. The experimentally obtained results suggest that the spatiotemporal distributions of the SEPs reflect the differences for positions, strengths, and patterns of somatosensory stimulations.

DOI： 10.1109/EMBC.2012.6347024

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical Engineers of Japan  

Cortical dipole imaging is one of the spatial enhancement techniques from the scalp electroencephalogram. We investigated the dipole imaging for multiple signal sources under time-varying non-uniform noise conditions. The effects of incorporating statistical information of noise into the spatiotemporal inverse filter were examined by computer simulations and experimental studies in three sphere volume conductor model. The parametric projection filter that incorporated with noise covariance was applied to the inverse problem of EEG measurements. The noise covariance matrix was estimated by applying independent component analysis to the scalp potentials. The spatial filter was expanded to apply to the time-varying non-uniform noise conditions such as eye blink artifact. Moreover, multiple dipole distributions were introduced to extract and to visualize individual signal sources. The proposed imaging technique was applied to human experimental data of visual evoked potentials. We obtained reasonable results that coincide to physiological knowledge. © 2011 The Institute of Electrical Engineers of Japan.

DOI： 10.1541/ieejeiss.131.1958

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Language：English   Publishing type：Research paper (international conference proceedings)  

Cortical dipole imaging is one of the spatial enhancement techniques from the scalp electroencephalogram. We investigated the cortical dipole imaging for multiple signal sources under time-varying non-uniform noise conditions. The effects of incorporating statistical information of noise into the spatiotemporal inverse filter were examined in three sphere volume conductor model. The parametric projection filter that incorporated with noise covariance was applied to the inverse problem of EEG measurements. The noise covariance matrix was estimated by applying independent component analysis to the scalp potentials. The spatial filter was expanded to apply to the time-varying non-uniform noise conditions such as eye blink artifact. Moreover, multiple dipole distributions were introduced to extract individual signal sources. The proposed imaging technique was applied to human experimental data of visual evoked potentials. © 2011 IEEE.

DOI： 10.1109/NFSI.2011.5936813

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY  

Equivalent cortical dipole layer imaging is proposed for high-resolution electroencephalogram (EEG) visualization. Equivalent dipole layer distribution parallel to the brain surface has been used in previous head models. In the present study, the additional dipole distribution on the median plane is introduced to identify the three-dimensional (3D) position and orientation of dipole sources. The parametric Wiener filter (PWF) using statistical signal and noise information was applied to solve an inverse problem of cortical dipole imaging. Simulations were performed in an inhomogeneous, concentric, three-sphere volume conductor head model under various signal conditions. Cortical dipole imaging provided localized brain electrical activity with better spatial resolution compared to the scalp potential map. These simulation results suggested that the depth and orientation of individual dipole sources could be observed by mapping on both spherical and median planes. We applied the proposed imaging technique to human experimental data of the visual evoked potential (VEP) and obtained reasonable results that coincide with physiological knowledge. (C) 2010 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

DOI： 10.1002/tee.20619

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

In clinical situations, the objective evaluation of somatic sensations is expected without a patient's subjective opinions to reduce social problems such as those related to lawsuits for nerve injuries and malingering. In this study, the somatosensory evoked potential (SEP) using the mechanical stimulations of the tactile sensation was measured and analyzed in spatiotemporal domains. The spatial resolution of SEP maps was improved by application of cortical dipole layer imaging. The experimentally obtained results suggest that the spatiotemporal distributions of the SEPs reflect the differences for positions, strengths, and patterns of somatosensory stimulations.

DOI： 10.1109/IEMBS.2011.6091775

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

We investigated suitable spatial inverse filters for cortical dipole imaging from the scalp electroencephalogram (EEG). The effects of incorporating statistical information of signal and noise into inverse procedures were examined by computer simulations and experimental studies. The parametric projection filter (PPF) and parametric Wiener filter (PWF) were applied to an inhomogeneous three-sphere volume conductor head model. The noise covariance matrix was estimated by applying independent component analysis (ICA) to scalp potentials. The present simulation results suggest that the PPF and the PWF provided excellent performance when the noise covariance was estimated from the differential noise between EEG and the separated signal using ICA and the signal covariance was estimated from the separated signal. Moreover, the spatial resolution of the cortical dipole imaging was improved while the influence of noise was suppressed by including the differential noise at the instant of the imaging and by adjusting the duration of noise sample according to the signal to noise ratio. We applied the proposed imaging technique to human experimental data of visual evoked potential and obtained reasonable results that coincide to physiological knowledge.

DOI： 10.1587/transinf.E93.D.2626

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Language：English   Publishing type：Research paper (international conference proceedings)  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

We have investigated the suitable spatial filters for inverse estimation of cortical dipole imaging from the scalp electroencephalogram. The effects of incorporating statistical information of noise into inverse procedures were examined by computer simulations and experimental studies. The parametric projection filter (PPF) was applied to an inhomogeneous three-sphere volume conductor head model. The noise covariance matrix was estimated by applying independent component analysis (ICA) to the scalp potentials. Moreover, the sampling method of the noise information was examined for calculating the noise covariance matrix. The simulation results suggest that the spatial resolution was improved while the effect of noise was suppressed by including the separated noise at the time instant of imaging and by adjusting the number of samples according to the signal to noise ratio.

DOI： 10.1109/IEMBS.2009.5334965

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Institute of Electrical Engineers of Japan  

A purpose of this study is to support communication of developmentally disabled individuals with motor paralysis, such as Guillain-Barre Syndrome, brain-stem infarction, having difficulty in conveying their intention. In the present paper, a pointing device controlled by DC-coupled electrooculograms (EOGs) has been developed. The optic angle of the subject was estimated from the amplitude of vertical and horizontal EOGs for determining the two dimensional pointing position on the PC screen in real time. The eye blinking artifact was reduced using a median filter. The displacement of electrode position was compensated by considering the potential gradient. Moreover, the position error caused by drift phenomenon was adjusted by using head movement. The accuracy and operating speed of the proposed method were evaluated in human experiments. © 2009 The Institute of Electrical Engineers of Japan.

DOI： 10.1541/ieejeiss.129.1792

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

The purpose of this study is to support communication of individuals with motor paralysis having difficulty verbally communicating due to illnesses such as Guillain-Barre Syndrome or brain-stem infarction. We have developed and describe a pointing device controlled by DC-coupled electrooculograms (EOGs). The visual angle of the subject is estimated from the amplitude of vertical and horizontal EOGs for determining the two-dimensional pointing position on a PC screen in real time. The eye blinking artifact is reduced using a median filter. Electrode displacement is corrected by considering the potential gradient. Moreover, the position error caused by drift phenomenon is adjusted using head movement based on the vestibule-ocular reflex. The accuracy and operating speed of the proposed method were evaluated among a group of human subjects.

DOI： 10.1109/IEMBS.2009.5334617

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Language：English   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Suitable spatial filters were explored for inverse estimation of cortical dipole imaging from a scalp electroencephalogram. Computer simulations were used to examine the effects of incorporating statistical information of signal and noise into inverse procedures. Actually, the parametric projection filter (PPF) and parametric Wiener filter (PWF) were applied to an inhomogeneous three-sphere head model. The signal and noise covariance matrices were estimated by applying independent component analysis (ICA) to the scalp potentials. The simulation results described herein suggest that the PPF using differential noise between EEG and separated signal were equivalent to those obtained using the method with actual noise. Moreover, the PWF using separated signals has better performance than traditional inverse techniques.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPRINGER-VERLAG BERLIN  

A number of efforts have been made in the development of high-resolution EEG techniques, which attempt to map spatially distributed brain electrical activity with substantially improved spatial resolution. The objective of this study is to explore suitable spatial filters for inverse estimation of cortical potential imaging from the scalp electroencephalogram. The effects of incorporating statistically signal and noise information into inverse procedures were examined by computer simulations and experimental study. The parametric Weiner filter (PWF) with signal and noise covariance was applied to an inhomogeneous head model under various signal and noise conditions. The present simulation results suggest that, the PWF provides better cortical imaging results than the Tikhonov regularization under the condition of moderate and high correlation between signal and noise distributions. The proposed methods were applied to self-paced movement-related potentials (MRPs). The cortical potential maps estimated by means of PWF were well-localized in the premotor cortex, which is consistent with the hand motor representation.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

We have developed new estimation method for equivalent dipole sources inside of the brain. We have solved an inverse problem that estimated an equivalent dipole-layer distribution from the scalp electroencephalogram by a spatio-temporal inverse filters. In the present study, we estimated the position and moment of equivalent dipole sources from dipole layer distributions. Moreover, we separated each dipole layer distribution using independent component analysis to identify the number, position, and moment of several dipole sources. The performance of the proposed estimation method was evaluated by computer simulation and human experimental studies in an inhomogeneous three-concentric sphere head model. The present simulation results indicated that the equivalent dipole sources were accurately estimated by our methods. We also applied the proposed method to human experimental data of movement-related potentials.

DOI： 10.1109/NFSI-ICFBI.2007.4387681

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SCHATTAUER GMBH-VERLAG MEDIZIN NATURWISSENSCHAFTEN  

Objective: The objective of this study is to explore suitable spatial filters for inverse estimation of cortical equivalent dipole layer imaging from the scalp electroencephalogram. We utilize cortical dipole source imaging to locate the possible generators of scalp-measured movement-related potentials (MRPs) in human.
Methods: The effects of incorporating signal and noise covariance into inverse procedures were examined by computer simulations and experimental study. The parametric projection filter (PPF) and parametric Weiner filter (PWF) were applied to an inhomogeneous three-sphere head model under various noise conditions.
Results: The present simulation results suggest that the PWF incorporating signal information provides better cortical dipole layer imaging results than the PPF and Tikhonov regularization under the condition of moderate and high correlation between signal and noise distributions. On the other hand, the PPF has better performance than other inverse filters under the condition of low correlation between signal and noise distributions. The proposed methods were applied to self-paced MRPs in order to identify the anatomic substrate locations of neural generators. The dipole layer distributions estimated by means of PPF are well-localized as compared with blurred scalp potential maps and dipole layer distribution estimated by Tikhonov regularization. The proposed methods demonstrated that the contralateral premotor cortex was preponderantly activated in relation to movement performance.
Conclusions: In cortical dipole source imaging, the PWF has better performance especially when the correlation between the signal and noise is high. The proposed inverse method was applicable to human experiments of MRPs if the signal and noise covariances were obtained.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

A horizontal and vertical dipole layer model was developed for three dimensional dipole layer imaging of brain electrical activity. Horizontal dipole layer being parallel to the brain surface has been used in previous head models. In the present study, the dipole layer distribution in the sagittal plane was also estimated from the scalp electroencephalogram. The parametric projection filter was applied to an inverse problem in a homogeneous plane head model under various signal conditions. The present simulation results suggest that the depth information of dipole sources could be observed by our method.

DOI： 10.1109/CNE.2007.369651

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

A communication support interface controlled by eye movements and voluntary eye blink has been developed for disabled individuals with motor paralysis who cannot speak. Horizontal and vertical electro-oculograms were measured using two surface electrodes attached above and beside the dominant eye and referring to an earlobe electrode and amplified with AC-coupling in order to reduce the unnecessary drift. Four directional cursor movements -up, down, right, and left- and one selected operation were realized by logically combining the two detected channel signals based on threshold settings specific to the individual. Letter input experiments were conducted on a virtual screen keyboard. The method's usability was enhanced by minimizing the number of electrodes and applying training to both the subject and. the device. As a result, an accuracy of 90.1 +/- 3.6% and a processing speed of 7.7 +/- 1.9 letters/min. were obtained using our method.

DOI： 10.1093/ietisy/e89-d.6.1790

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.3191/thermalmedicine.22.1

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Suitable spatial filters were explored for inverse estimation of cortical potential imaging from the scalp electroencephalogram. The effects of incorporating signal and noise covariance into inverse procedures were examined by computer simulations and experimental study. The parametric Wiener filter (PWF) was applied to an inhomogeneous three-sphere head model under various signal and noise conditions. We also examined estimation methods for the signal covariance in PWF. The present simulation results suggest that the PWF with modified matrix transformation method has better performance. The proposed methods were applied to self-paced movement-related potentials in order to identify the anatomic substrate locations of neural generators in realistic-shaped head model. The proposed methods demonstrated that the contralateral premotor cortex was preponderantly activated in relation to movement performance.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

A communication support interface controlled by eye movements and voluntary eye blink has been developed for disabled individuals with motor paralysis who cannot speak. Horizontal and vertical electro-oculograms were measured using two electrodes attached above and beside the dominant eye and referring to an earlobe electrode and amplified with AC-coupling in order to reduce the unnecessary drift. Eight directional cursor movements and one selected operation were realized by logically combining the two detected channel signals based on threshold setting specific to the individuals. As experimental results using a projected screen keyboard, processing speed was improved to 12.1 letters/min. while the accuracy was 90.4%.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

A smart video magnifier for the people with visual disabilities is now being developed to assist their stress-free reading. In a video magnifier, the users watch the monitor screen that is displaying the book page to be read. Eye movement is needed for reading a book. The difficulty of character recognition that is dependent on the environmental conditions is reflected to the eye movement. Accordingly, information on the visibility of the user is extracted as physiological signals accompanied by the gazing motion. These signals are basically used to control the video magnifier. The advantages and usefulness of the adaptive-type video magnifier are discussed in this paper.

DOI： 10.1109/IEMBS.2006.259900

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

A communication support interface controlled by eye movements and voluntary eye blink has been developed for disabled individuals with motor paralysis who cannot speak. Horizontal and vertical electro-oculograms were measured using two electrodes attached above and beside the dominant eye and referring to an earlobe electrode and amplified with AC-coupling in order to reduce the unnecessary drift. Eight directional cursor movements and one selected operation were realized by logically combining the two detected channel signals based on threshold setting specific to the individuals. As experimental results using a projected screen keyboard, processing speed was improved to 12.1 letters/min. while the accuracy was 90.4%.

DOI： 10.1109/IEMBS.2006.259914

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER-VERLAG BERLIN  

A communication support interface controlled by eye movements and voluntary eye blink has been developed for disabled individuals with motor paralysis who cannot speak. Horizontal and vertical electro-oculograms were measured using two surface electrodes attached above and beside the dominant eye and referring to an earlobe electrode and amplified with AC-coupling in order to reduce the unnecessary drift. Four directional cursor movements -up, down, right, and left- and one selected operation were realized by logically combining the two detected channel signals based on threshold settings specific to the individual. Letter input experiments were conducted on a virtual screen keyboard. As a result, operatablility, accuracy, and processing speed were improved using our method.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SCRIPTA TECHNICA-JOHN WILEY & SONS  

One of the methods of generating physical random numbers is the use of electrical signals. Previously, when random numbers have been generated from electrical signals, a threshold value has been imposed on the signal level and "0" and "1" have been assigned depending on whether this threshold value was exceeded. In the present paper, the lowest bit of an A-D converter is used so as to demonstrate that high-speed generation of random numbers, which is not achievable by the conventional method, is now possible. Further, it is demonstrated that random numbers can be generated by fluctuations of an oscillator instead by a special noise generator. (c) 2006 Wiley Periodicals, Inc.

DOI： 10.1002/ecjc.20215

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER-VERLAG BERLIN  

A communication support interface controlled by eye movements and voluntary eye blink has been developed for disabled individuals with motor paralysis who cannot speak. Horizontal and vertical electro-oculograms were measured using two surface electrodes attached above and beside the dominant eye and referring to an earlobe electrode and amplified with AC-coupling in order to reduce the unnecessary drift. Four directional cursor movements -up, down, right, and left- and one selected operation were realized by logically combining the two detected channel signals based on threshold settings specific to the individual. Letter input experiments were conducted on a virtual screen keyboard. As a result, operatablility, accuracy, and processing speed were improved using our method.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

We explored suitable estimation method for equivalent dipole sources in the brain. In a previous study, we solved an inverse problem that estimated an equivalent dipole-layer distribution from the scalp electroencephalogram by a spatio-temporal inverse filters constructed with parametric projection filter. In the present study, we estimated equivalent dipole sources from dipole layer distributions. Moreover, to identify the number, position, and moment of equivalent dipole sources, we separated each dipole layer distribution using independent component analysis (ICA). The performance of the proposed estimation method was evaluated by computer simulation and human experimental studies in an inhomogeneous three-concentric sphere head model. The present simulation results indicated that the equivalent dipole sources was accurately estimated by ICA and dipole imaging. We also applied the proposed method to human visual evoked potential.

DOI： 10.1109/IEMBS.2006.259907

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

We explored suitable estimation method for equivalent dipole sources in the brain. In a previous study, we solved an inverse problem that estimated an equivalent dipole-layer distribution from the scalp electroencephalogram by a spatio-temporal inverse filters constructed with parametric projection filter. In the present study, we estimated equivalent dipole sources from dipole layer distributions. Moreover, to identify the number, position, and moment of equivalent dipole sources, we separated each dipole layer distribution using independent component analysis (ICA). The performance of the proposed estimation method was evaluated by computer simulation and human experimental studies in an inhomogeneous three-concentric sphere head model. The present simulation results indicated that the equivalent dipole sources was accurately estimated by ICA and dipole imaging. We also applied the proposed method to human visual evoked potential.

DOI： 10.1109/IEMBS.2006.259907

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：International Society for Bioelectromagnetism  

CiNii Article

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Language：Japanese   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：International Society for Bioelectromagnetism  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SCRIPTA TECHNICA-JOHN WILEY & SONS  

The authors previously published a physical method for the generation of random numbers by a variable capacitance parametron, which can generate uniform random numbers without periodicity. It is considered possible to generate random numbers with an ordinary oscillator if the oscillation frequency is made unstable. As a method of introducing instability, frequency modulation of an LC oscillator with shot noise is considered. The present paper describes experiments with an LC oscillator to which shot noise is applied. An evaluation of statistical randomness (FIPS 140-2) is carried out for the generated number sequence as cryptographic random numbers. It is shown that generation of random numbers is possible. (C) 2005 Wiley Periodicals, Inc.

DOI： 10.1002/ecjc.20149

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Publisher：The Society of Life Support Engineering  

DOI： 10.5136/lifesupport.17.Supplement_38

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

In the present study, we explore suitable spatio-temporal filters for inverse estimation of an equivalent dipole-layer distribution from the scalp electroencephalogram (EEG) for imaging of brain electric sources. We propose a time-varying parametric projection filter (tPPF) for the spatio-temporal EEG analysis. The performance of this tPPF algorithm was evaluated by computer simulation studies. An inhomogeneous three-concentric-spheres model was used in the present simulation study to represent the head volume conductor. An equivalent dipole layer was used to represent equivalently brain electric sources and estimated from the scalp potentials. The tPPF filter was tested to remove time-varying noise such as instantaneous artifacts caused by eyes-blink. The present simulation results indicate that the proposed time-variant tPPF method provides enhanced performance in rejecting time-varying noise, as compared with the time-invariant parametric projection filter.

DOI： 10.1109/TBME.2004.824142

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ELSEVIER SCIENCE BV  

We explore suitable spatiotemporal filters for inverse estimation of an equivalent cortical dipole layer (DL) distribution from the scalp electroencephalogram (EEG) for imaging of brain electric sources. We have previously developed the parametric projection filter (PPF)-based cortical dipole layer imaging technique, which allows estimating cortical dipole layer inverse solutions in the presence of noise covariance. We have expanded the PPF to the time-varying filter in order to handle the spatiotemporally varying nature of brain electrical activity. The present simulation results indicate that the estimation error is reduced substantially by taking the spatiotemporal properties of the noise into consideration, such as eye-blink artefacts, and the proposed time-variant PPF method provides enhanced performance in rejecting time-varying noise. (C) 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.ics.2004.05.149

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：ELSEVIER SCIENCE BV  

We explore suitable spatiotemporal filters for inverse estimation of an equivalent cortical dipole layer (DL) distribution from the scalp electroencephalogram (EEG) for imaging of brain electric sources. We have previously developed the parametric projection filter (PPF)-based cortical dipole layer imaging technique, which allows estimating cortical dipole layer inverse solutions in the presence of noise covariance. We have expanded the PPF to the time-varying filter in order to handle the spatiotemporally varying nature of brain electrical activity. The present simulation results indicate that the estimation error is reduced substantially by taking the spatiotemporal properties of the noise into consideration, such as eye-blink artefacts, and the proposed time-variant PPF method provides enhanced performance in rejecting time-varying noise. (C) 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.ics.2004.05.149

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SCHATTAUER GMBH-VERLAG MEDIZIN NATURWISSENSCHAFTEN  

Objectives: The objective of this study was to explore suitable spatial filters for inverse estimation of cortical potentials from the scalp electroencephalogram. The effect of incorporating noise covariance into inverse procedures was examined by computer simulations and tested in human experiment.
Methods: The parametric projection filter, which allows inverse estimation with the presence of information on the noise, was applied to an inhomogeneous three-concentric-sphere model under various noise conditions in order to estimate the cortical potentials from the scalp potentials. The method for determining the optimum regularization parameter, which can be applied for parametric inverse techniques, is also discussed.
Results. Human visual evoked potential experiment was carried out to examine the performance of the proposed restoration method. The parametric projection filter gave more localized inverse solution of cortical potential distribution than the truncated SVD and Tikhonov regularization.
Conclusion: The present simulation results suggest that incorporation of information on the noise covariance allows better estimation of cortical potentials, than inverse solutions without knowledge about the noise covariance, when the correlation between the signal and noise is low.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

A communication interface controlled by eye movements and voluntary eye blink has been developed for disabled individuals who have motor paralysis and therefore cannot speak. Horizontal and vertical electro-oculograms were measured using two surface electrodes referring to an earlobe electrode. Four directional cursor movements and one selection were realized by logically combining the detected two channel signals. Virtual input experiments were conducted on a virtual screen keyboard. Its usability and accuracy were improved using our proposed method.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

The objective of this study was to explore suitable spatial filters for inverse estimation of cortical potentials from the scalp electroencephalogram. The effect of incorporating noise covariance into inverse procedures was examined by computer simulations. The parametric projection filter, which allows inverse estimation with the presence of information on the noise covariance, was applied to an inhomogeneous three-concentric-sphere model under various noise conditions in order to estimate the cortical potentials from the scalp potentials. The present simulation results suggest that incorporation of information on the noise covariance allows better estimation of cortical potentials, than inverse solutions without knowledge about the noise covariance. when the correlation between the signal and noise is low. The method for determining the optimum regularization parameter, which can be applied for parametric inverse techniques, is also discussed.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SCRIPTA TECHNICA-JOHN WILEY & SONS  

In the present study, a random number generator which physically produces nonperiodic uniform random number was developed using the parametron principle. The parametron is an oscillation circuit at one-half of the excited frequency. The phase of the parametron cannot be predicted because it depends on the noise in the parametron circuit. The random number was generated by detecting the unpredictable phase. The randomness of the data generated by the present method was confirmed by the spatial distribution and by statistical random tests. (C) 2002 Wiley Periodicals, Inc.

DOI： 10.1002/ecjc.10040

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

The objective of this study is to explore suitable spatial filters for inverse estimation of cortical equivalent dipole layer imaging from the scalp electroencephalogram. The effects of incorporating signal and noise covariance into inverse procedures were examined by computer simulations. The parametric projection filter (PPF) and parametric Weiner filter (PWF) were applied to an ideal 3D head model under various noise conditions. The present simulation results suggest that the PPF has better performance than the PWF, when the correlation between the signal And noise is low, and the PWF performs better than the PPF when the correlation is high.

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DOI： 10.3191/thermalmedicine.17.231

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

In the present study, spatial filters for inverse estimation of an equivalent dipole layer from the scalp-recorded potentials have been explored for their suitability in achieving high-resolution electroencephalogram (EEG) imaging. The performance of the parametric projection filter (PPF), which we propose to use for high-resolution EEG imaging, has been evaluated by computer simulations in the presence of a priori information on noise. An inhomogeneous three-concentric-sphere head model was used in the present simulation study to represent the head volume conductor. An equivalent dipole layer was used to model brain electric sources and estimated From the scalp potentials. Various noise conditions were simulated and the parametric projection filter was compared with standard regularization procedures such as the truncated singular value decomposition (TSVD) and the Tikhonov regularization (TKNV). The present simulation results suggest that the proposed method performs better than that of commonly used inverse regularization techniques, such as the general inverse using the TSVD and the TKNV, when the correlation between the original source distribution and the noise distribution is low, and performs similarly when the correlation is high. A method for determining the optimum regularization parameter, which can be applied to parametric inverse techniques, has also been developed. (C) 2001 Biomedical Engineering Society.

DOI： 10.1114/1.1366674

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

The restoration of biomedical images that have been blurred due to body movement are discussed. The observation system for these images is described using a mathematical operator and coordinate transformations. And a band-suppressed restoration filter composed of a series of such operators is proposed for improving the quality of images. In addition, redundancy is introduced into these restoration filters in order to suppress additive noise. The proposed method is applied to blurred X-ray images of a bone model of the elbow joint. The optimum position and number of markers, which are attached to the subject as a reference signal, are also discussed.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SCHATTAUER GMBH-VERLAG MEDIZIN NATURWISSENSCHAFTEN  

The restoration of X-ray images that have been blurred due to body movement are discussed. The observation system for these images is described using a mathematical model, and several restoration filters composed of a series of such models are proposed. These filters restore band-suppressed approximations of the original images. In addition, redundancy is introduced into these restoration filters in order to suppress additive noise. These filters are expanded to be applicable not only to parallel translations, but also to rotations by coordinate transformation. The proposed methods are applied to blurred X-ray images of a bone model of the elbow joint. The parameters of the restoration filter are estimated using a marker attached to the subject as a reference signal.

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DOI： 10.11239/jsmbe1963.38.102

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

The objective of this study was to explore suitable spatial filters for inverse estimation of cortical equivalent dipole layer from the scalp EEG The performance of the Weiner filter and the projection filter as a restoration filter was examined by computer simulations. The parametric Weiner filter (PWF) and the parametric projection filter (PPF) were applied to an idealized 3D head model under the various noise conditions in order to estimate the dipole layer distribution from scalp potentials. The PPF and PWF algorithms were compared with commonly used inverse regularization techniques, such as the general inverse using the truncated singular value decomposition (TSVD) and the Tikhonov regularization (TKNV), The present simulation results suggest that the PWF and PPF perform better than that of the TSVD and the TKNV in the condition of edge-concentrated non- uniform noise when the correlation between the signal and noise is low.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRONICS INFORMATION COMMUNICATIONS ENG  

In the present paper we shall examine the real-time restoration of biomedical signals under additive noises. Biomedical signals measured by instruments such as catheter manometers, ambulatory electrocardiographs and thermo-dilution sensors are susceptible to distortion and noise. Therefore, such signals must be restored to their original states. In the present study, nonstationary biomedical signals are observed and described using a mathematical model, and several restoration filters that are composed of a series of applications of this model are proposed. These filters restored band-limited approximations of the original signals in real-time. In addition, redundancy is introduced into these restoration filters in order to suppress additive noise. Finally, an optimum filter that accounts for restoration error and additive noise is proposed.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

In this paper we examined the restoration of X-ray images blurred by body motion. We described the observation of these images with a mathematical model and proposed several restoration filters composed of series of such models. These filters restored band-suppressed approximations of the original images in real-time. Furthermore, we introduced redundancy into these restoration filters in order to suppress the additive noise. We applied these methods to blurred X-ray images of an elbow bone model. The parameters of the restoration Filter were estimated by using a marker attached to the subject as a reference signal.

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DOI： 10.3191/thermalmedicine.13.68

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DOI： 10.3191/thermalmedicine.12.401

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Japanese Society for Thermal Medicine  

Basic heating characteristics of a flexible and variable shape electrode were measured for a new internal hyperthermic therapy under laparoscopy. A metal chain was used as an internal electrode in 13. 56 MHz RF heating. Heating characteristics were measured with various shapes of chain electrodes, <I>i. e</I>. zigzag, spiral, radiation and layers. From the results of experiments using muscle-equivalent phantoms, we conclude that concentrated heating characteristics were produced between the internal electrode and the reference electrode when spreading the chain electrode arranged in layers, parallel to the reference electrode.

DOI： 10.3191/thermalmedicine.12.393

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Adapting the principle of parametron oscillation, a small implantable temperature sensor requiring no internal power supply is described. Since this sensor's oscillation frequency is half that of the excitation frequency, the oscillated signal can be measured from the reception side, free of any signal, interference, simply by positioning the sensor and the excitation antenna so that; 1) they are separated up to 95 cm in the air; 2) a 41 cm gap, the phantom equivalent of the thickness of the human abdomen maintain between them. In the temperature-dependent quartz resonator sensor, oscillation occurs only when frequency and temperature correspond. The excitation power is then adjusted so that the frequency bandwidth narrows. As a result, the margin of error in measuring the temperature is minimized; (+/- 0.07 degrees C).

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A "reentrant resonant-cavity applicator" is a hyperthermic system having a resonant cavity, inside of which are two reentrants. In simulated heating test, the applicator produced a cylinder-shaped area of high temperature in the center of a heated object. This paper describes the heating characteristics of the applicator, in order to appraise its ability to produce concentrated heating for cylindrical-shaped phantoms of 24 cm diameter and 12 cm height. In experiments using these phantoms, concentrated heating characteristics were produced, which are superior to RF capacitive heating. In order to perform concentrated heating, 1) the height of the phantoms must be maintained at less than about 40% of the distance between the two reentrants, 2) the diameter of the plates concentrating the electric field must be about 1.5 times larger than the height of the phantom, 3) the impedance between the applicator and a power supply must be matched.

DOI： 10.3191/thermalmedicine.12.401

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When measuring the ejection fraction for the evaluation of the ventricular pumping function by means of the thermodilution technique, the slow response a conventional thermistor has caused it to be considered unsuitable, and fast thermistors have been proposed as an alternative. However, in this paper we propose improving the time-domain response of a conventional thermistor using a signal processing technique composed of a series of first-order high-pass filters which is known as the natural observation system. We considered the rise time of the thermistor in response to a step temperature change to effect correction for the measurement of the ejection fraction. The coefficients of the natural observation system were calculated by minimizing the square error between the step-response signal of the thermistor and the band-limited reference signal. In an experiment using a model ventricle, the thermodilution curve obtained from a conventional thermistor was improved using the proposed technique, thus enabling successful measurement of the ejection fraction of the ventricles.

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：JAPANESE SOCIETY FOR ARTIFICIAL ORGANS  

We studied the closing sound of SJM prosthetic heart valve(SJM) by the power-frequency-time analysis, using the fast Fourier transform; the method of Wigner-Ville. The peak of distribution of power-frequencytime surface was around 1.3 to 1.5KHz, and its maximal value was up to 5.0 KHz. As the frequency of the sound spectrum became higher, the power became weaker proportionally . By the pseudo-thrombus attachment to the SJM ring, decrease in the power was noted especially in the range of 1.5 to 3.0 KHz. When the size of the pseudo-thrombus was gotten to be bigger, decrease in the power in the range of 1.5 to 3.0 KHz was also noted. Furthermore, the appearance-time of the sound spectrum got shorter. When it was the maximal size of pseudo-thrombus, finally, the distribution of the continuous frequency peaked at 1.0 KHz was only noted. In this study, by analysis of the power-frequency-time analysis of the closing sound of SJM, the decrease in the power as well as shortening o f the appearance-time of the spectrum were noted in the case of the pseudo-thrombus attached on SJM. It was soncluded that the powerfrequency-time analysis of closing sound of SJM was useful for the early and accurate diagnosis for its malfunction.

DOI： 10.11392/jsao1972.23.151

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：I E E E  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRON INFO COMMUN ENG  

We use the B spline function and apply the Oslo algorithm to minimize the number of control points in electrocardiogram (ECG) waveform compression under the limitation of evaluation indexes. This method is based on dynamic programming matching to transfer the control points of a reference ECG waveform to the succeeding ECG waveforms. This reduces the execution time for beat-to-beat processing. We also reduced the processing time at several compression stages. When the difference percent normalized root mean square difference is around 10, our method gives the highest compression ratio at a sampling frequency of 250 Hz.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEICE-INST ELECTRON INFO COMMUN ENG  

The pressure waveforms indicated on a catheter manometer system are subject to serious distortion due to the resonance of the catheter itself, or the compliance of a particular transducer. Although several methods have been proposed for improving those characteristics, they have never been put into practice. We have focused on the transfer function of the catheter manometer, and made a pilot system, using the natural observation method. This method has been suggested as a means of studying the structure of the instantaneous waveform. In this manner, we were able to increase the bandwidth in the frequency domain and reduce the ringing in the time domain. Correction was performed automatically, using a step wave. Reproduction of the waveform with a flushing device, was a task of equal simplicity, that allowed us to estimate the system parameters so that the response waveform became step-like. In the experiment, our system provided distortion-free left-ventricular pressure waveform measurements and exact evaluation of the cardiac pumping system. The values obtained came much closer to the original figures arrived at by the catheter-tip manometer system.

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：JAPANESE SOCIETY FOR ARTIFICIAL ORGANS  

Using the technique of the fast Fourier transform, the influence of the circuit fluid and the closing pressure to the closing sound of SJM valve was studied by the power-spectrum analysis. Using the water as the test fluid, the power-spectrum curve of the closing sound showed two peaks at the points of 0.8 and 2.5 KHz, but using glycerol, the curve indicated one large peak at 0.7 KHz and a smaller peak at 2.1 KHz, and the power declined over 3 KHz. The power-spectrum curve showed no changes with the closing pressure change from 50 to 1.50 mmHg. By the fibrin glue attachment to the SJM valve ring, the power of each peak declined both in water and in glycerol. This change can be considered to suggest the thrombus formation of the SJM valve in the clinical state. The power-spectrum curve of closing sound of the SJM valve was changed by the circuit fluid, but not changed by the closing pressure.

DOI： 10.11392/jsao1972.21.635

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：JAPANESE SOCIETY FOR ARTIFICIAL ORGANS  

The closing sound of the SJM cardiac valve prosthesis was analysed both in vitro and in vivo, using the technique of the fast Fourier transform. In vitro, the power-spectrum curve of the closing sound contains a peak at 0.6 KHz, and the power gradually decline to 7 KHz. It also has small peaks at about 1.2, 1.8, 2.4 and 3.6 KHz. In vivo, the spectra of the normally functioning SJM cardiac valve prostheses show the same curve as the curve in vitro. In the case of the cardiac valve prosthesis attached with fibrin glue on the housing, the power declined to between 0.6 and 3 KHz. The same curve was shown clinically in two cases of the thrombosed SJM cardiac valve prosthesis and thromboembolism. The decline of the power between 0.6 and 3 KHz suggests the throm-bus or pannus formation of the SJM cardiac valve prosthesis.

DOI： 10.11392/jsao1972.20.915

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japanese Society for Medical and Biological Engineering  

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Language：Japanese   Publisher：JAPANESE SOCIETY FOR ARTIFICIAL ORGANS  

The closing sounds of eleven St. Jude Medical cardiac prostheses at mitral position were analysed using the technique of the fast Fourier transform. The frequency-spectra contain a peak at about 1KHz, and decline the power to 5 to 7KHz. In two patients, 8.3 years and 4.5 years postoperatively, their frequency spectra of one leaflet showed a dip at 2.5KHz, respectively. The closing sound analysis is a useful methodd for the early detection of thrambosed SJM cardiac prosthesis at mitral position as well as at aortic or pulmonary position.

DOI： 10.11392/jsao1972.19.382

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Language：Japanese   Publisher：JAPANESE SOCIETY FOR ARTIFICIAL ORGANS  

The closing sound of seven St. Jude Medical (SJM) cardiac prostheses were analysed for the power content as a function of frequency using the technique of the fast Fourier transform. The frequency specutra of normal SJM cardiac prostheses were seen to contain a peak at 1.2KHz, and decline the power to 7.5KHz at aortic position. The frequency specutra of the leaflet, opening angle of which were decreased, were seen to contain a dip at 2.5KHz at aortic and pulmonary position. Otherwise, the spectra of another one were seen to contain no dips. The dip at 2.5KHz gave useful information about the SJM cardiac prosthetic malfunction.

DOI： 10.11392/jsao1972.18.694

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Pressure waveforms obtained by catheter manometer systems are often distorted by resonance of catheter and so on. Corrections by Fourier analysis, low pass filter and digital signal proccessing have been reported, but they have never been put to practical use. We paid attention to the transfer function of catheter transducer systems and made a trial system that correct the distortion by natural observation method. This system increases the bandwidth in frequency domain and reduce the ringing in time domain. Advantages of this system are simple composition, a small number of adjusting points and real time performance without modifying the catheter or transducer. In an animal experiment, we corrected by our trial system the output waveforms recorded by a conventional catheter manometer system and compared these corrected output waveforms with catheter-tip manometer waveforms which are relatively distortionless. As a result, we could obtain less distorted pressure waveforms in left-ventricle and aorta and distinctly confirm dicrotic notch in aortic pressure waveforms. © 1988, Japanese Society for Medical and Biological Engineering. All rights reserved.

DOI： 10.11239/jsmbe1963.26.133

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Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (trade magazine, newspaper, online media)   Publisher：株式会社エイチ．ケイコネクション  

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Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (trade magazine, newspaper, online media)   Publisher：高松機械工業株式会社  

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Language：Japanese   Publisher：社団法人日本生体医工学会  

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J-GLOBAL

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J-GLOBAL

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

In the case of hearing examinations for abnormalities and fitting of a hearing aid, auditory brainstem evoked response (ABR) is often measured in clinical situations. In order to detect the ABR, a subject has to be given more than 1,000 hearing stimuli. We considered that the number of stimuli might be reduced by multi-channel measurements. Moreover, the accuracy of averaging was improved by verifying the accuracy of data for every stimulus. 9 channel ABR signals around the top of the head were measured in conducted experiments. Every ABR data of 10ms after the stimuli were statistically evaluated, and only the data suitable for averaging were selected. Although the number of averaging was very few, the ABR waveforms, which were equivalent to that of the conventional averaging, were obtained.

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Language：Japanese   Publisher：社団法人日本生体医工学会  

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Language：Japanese   Publisher：社団法人日本生体医工学会  

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Language：Japanese   Publisher：社団法人日本生体医工学会  

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Language：Japanese   Publisher：社団法人日本生体医工学会  

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Language：Japanese   Publisher：社団法人日本生体医工学会  

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Language：English   Publisher：The Institute of Electronics, Information and Communication Engineers  

In the present study, random number generator, which physically produces non-periodic uniform random number, was developed using the principle of parametron. The parametron is the oscillation circuit of one half of the excited frequency. The phase of the parametron cannot predict because it is decided by the noise in the parametron circuit. The random number was generated by detecting the unpredictable phase. The randomness of the data generated by the present method was confirmed by the space distribution and statistical random tests.

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

Reentrant resonant cavity applicator has been developed to obtain both a deep and concentrated heat for hyperthermic treatment. Moveover, the applicator was imporved for the purpose of realizing more effective heat for the subject with human body size. That is, the upside projection (reentrant) was separated from the applicator to approch to the downside projection. In this paper, we analyzed the modefied resonant cavity applicator by unified finite-difference method of electromagnetic field - heat transfer equations. As a result compared with measured temperature distributions, similar temperature distributions, the temperatures in a center and surroundings of the subject, are higher than the others. This paper suggested to be able to design more effective applicator by making suitable discrete data for resonant cavity applicator.

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Language：Japanese   Publisher：(一社)日本ハイパーサーミア学会  

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

A quasi-auditory filter based on normal natural-observation filter was proposed by Iijima for acoustic analysis or speech recognition. This filter did not realize nonlinear signal processing. observed in human auditory filter. In this study, we propose nonlinear auditory model by expanding the first-order fundamental element of normal natural-observation filter to second-order and introducing Q, that depends on the level of the input signal. The nonlinearity and the bandwidth of proposed filter are in good agreement with that of the human auditory filter.

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

Observed images are often degrated by the insufficient characteristics of the observation system. In this study we restore an original image from the degrated image, assuming that a degrated function is known and parameters that express a degration degree are unknown. A restoration filter for time-varying signal, which restored a band-limited signal on the original one, has been constructed by the finite-term filters. We expand this filter to the two-dimensional band-limited restoration filter, theoretically. The restoration results were evaluated by simulation, while considering the influence of additional noise.

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Language：Japanese   Publisher：The Institute of Electronics, Information and Communication Engineers  

Observed images are often degrated by an observation system. In this study we restore original images from degrated images, assuming that degrated functions are known and parameters that express a degrated degree are unknown. Original images are usually restored by the estimated parameters, but the estimates contained the error. Then, we applied the two-dimensional natural-observation method for compensating the estimation error. We estimated the parameters of degrated functions and the natural-observation coefficients, using a step image as a reference image. The results were evaluated by the estimation error of parameters for typical shift-invariant degrated functions such as Butterworth-type, Gaussian function, and Sinc function.

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