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Last Updated :2024/09/03

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Master

Affiliation (Master)

  • Faculty of Information Science and Technology　Bioengineering and Bioinformatics　Bioengineering

Affiliation (Master)

  • Faculty of Information Science and Technology　Bioengineering and Bioinformatics　Bioengineering

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Profile and Settings

Degree

  • Doctor(Engineering)（Tohoku University）

Profile and Settings

  • Name (Japanese)

    Kato

  • Name (Kana)

    Yuji

  • Name

    201301087920929779

Alternate Names

Achievement

Research Interests

  • 光CT   光散乱   散乱   中空導波路   後方散乱光   音響光学効果   赤外ファイバー   光生体計測   低コヒーレント干渉法   近赤外   低コヒーレント光干渉法   高分子薄膜   センサー   光薄膜   超音波   多重共鳴吸収   超音波変調法   音響光学特性   生体光計測   時間分解解析   近赤外光   生体透視   光拡散   近軸散乱光   snake photon   生体計測   誘電体内装中空導波路   医用画像   最小侵襲医療   断層イメージング   

Research Areas

  • Life sciences / Biomaterials
  • Life sciences / Biomedical engineering
  • Nanotechnology/Materials / Optical engineering and photonics

Research Experience

  • 2019/04 - Today 北海道大学大学院情報科学研究院 助教
  • 2007/04 - 2019/03 Hokkaido University Graduate School of Information Science and Technology
  • 2004/04 - 2007/03 Hokkaido University Graduate School of Information Science and Technology
  • 1998/04 - 2004/03 Hokkaido University Graduate School of Engineering
  • 1995/10 - 1998/03 Hokkaido University School of Engineering
  • 1994/04 - 1995/09 Tohoku University Faculty of Engineering

Education

  • 1989/04 - 1994/03  Tohoku University  Graduate School of Engineering
  • 1985/04 - 1989/03  Tohoku University  Faculty of Engineering

Published Papers

  • Tomoya Ishimaru, Taihiko Yamaguchi, Taishi Saito, Yoshinori Hattori, Takahiro Ono, Yoshiaki Arai, Yoko Hasegawa, Hiroshi Shiga, Katsushi Tamaki, Junko Tanaka, Kazuhiro Tsuga, Hitoshi Abekura, Shouichi Miyawaki, Aya Maeda-Lino, Saki Mikami, Akihito Gotouda, Kaoru Satoh, Koichi Shimizu, Yuji Kato, Takeshi Namita
    Journal of prosthodontic research 2024/01/12 [Refereed]
     
    PURPOSE: This study aimed to elucidate the relationship between diurnal masseter muscle activity and awareness of diurnal awake bruxism (d-AB) by conducting a comparative analysis of electromyographic (EMG) data from individuals with and without awareness of diurnal awake bruxism (d-AB), utilizing EMG data gathered from multiple subjects. METHODS: Unilateral masseter electromyography (EMG) recordings were performed during the daytime using an ultraminiature wearable EMG device. A total of 119 participants (59 with awareness of diurnal tooth clenching [d-TC] and 60 without awareness of d-TC) were included. Waveforms longer than 0.25 s with the two amplitude conditions, exceeding twice the baseline and >5% of maximum voluntary clenching, were extracted. In addition, the number of bursts and episodes (groups of bursts), burst duration, and burst peak amplitude were calculated for each participant. RESULTS: There were no significant differences in the EMG parameters between the groups with and without awareness of d-TC. Additionally, the frequency distribution of the number of EMG waveforms exhibited wide ranges and substantial overlap between the two groups. CONCLUSIONS: The variability in the number of bursts and episodes, burst peak amplitude, and burst duration among subjects suggests the need for an objective classification of d-AB severity based on EMG values. The absence of significant differences and large overlap in frequency distributions between the groups with and without awareness of d-TC indicate difficulty in predicting muscle activity solely based on awareness of d-AB.
  • Kazuhiro Nishida, Yuji Kato, Nobuki Kudo, Koichi Shimizu
    Japanese Journal of Applied Physics 60 (7) 0021-4922 2021/07 [Refereed]
     
    For a practical technique of cross-sectional imaging of animal bodies, we developed a new method using spatially resolved backscattered light. This method is based on the solution of the one-dimensional nonlinear inverse problem, and on the lateral scan of the source-detector pair along the object surface. Using this method, unknown variables in inverse problems can be reduced more greatly than when using conventional methods. A stable solution for the inverse problem becomes possible. The possibility of using the proposed method was assessed using simulation analysis. The results verified that cross-sectional imaging from several to 10 millimeter depths is possible for animal tissue. This analysis clarified the specific spatial resolution and accuracy in the estimated absorption coefficient. Distortionless imaging was confirmed. Results suggest that the proposed method represents new options as a stable and practical method for biological cross-sectional imaging.
  • 加藤祐次, 高見澤淳
    レーザー研究 49 (9) 0387-0200 2021 [Refereed][Invited]
  • Matsumura, K., Toda, S., Kato, Y.
    IEEE Access 8 80233 - 80242 2020 [Refereed][Not invited]
  • Nishida, K., Kato, Y., Kudo, N., Shimizu, K.
    Optics and Lasers in Engineering 126 1 - 11 0143-8166 2020 [Refereed][Not invited]
     
    This report presents a proposal of a new technique to estimate the cross-sectional absorption distribution of turbid media from backscattered light by solving a nonlinear inverse problem. After illuminating a beam of light on the surface of a turbid object and measuring the backscattered light as a function of distance from the light incident point, we divide the object into multiple virtual layers to estimate the absorption distribution. The path lengths of photon propagation in the respective layers are calculated using Monte Carlo simulation. The absorption coefficient of each virtual layer can be estimated from the backscattered intensity and the path length distribution in a depth direction. For solving this inverse problem, the linear calculation results are useful as initial solutions. Then the final solutions are obtained from iteration of the nonlinear calculation. Convergence into a unique solution and robustness of the solution against the measurement noise were confirmed. The effectiveness of the proposed technique was verified through simulation and measurement. By lateral scanning of a source detector pair, we can reconstruct a cross-sectional image of the turbid medium to the depth to which the detected light reaches.
  • Sogo Toda, Yuji Kato, Nobuki Kudo, Koichi Shimizu
    ADAPTIVE OPTICS AND WAVEFRONT CONTROL FOR BIOLOGICAL SYSTEMS V 10886 0277-786X 2019
  • Toda, S., Kato, Y., Kudo, N., Shimizu, K.
    Japanese Journal of Applied Physics 58 (3) 030903 - 030903 0021-4922 2019 [Refereed][Not invited]
     
    © 2019 The Japan Society of Applied Physics. For transillumination imaging of animal tissue, we have developed a technique to suppress the scattering effect in a turbid medium using the time-reversal principle of phase-conjugate light. In biomedical applications of this technique, the effects of absorption variation and the applicable tissue thickness must be clarified. Analysis of experimental data revealed that the scattering suppression capability of the proposed technique is independent of the absorption change of a turbid medium. Results also verified that the applicable thickness of animal tissue can be extended using a light source with greater coherence length.
  • Toda, S., Kato, Y., Kudo, N., Shimizu, K.
    Biomedical Optics Express 9 (4) 1570 - 1581 2156-7085 2018 [Refereed][Not invited]
     
    For transillumination imaging of animal tissues, we have attempted to suppress the scattering effect in a turbid medium using the time-reversal principle of phase-conjugate light. We constructed a digital phase-conjugate system to enable intensity modulation and phase modulation. Using this system, we clarified the effectiveness of the intensity information for restoration of the original light distribution through a turbid medium. By varying the scattering coefficient of the medium, we clarified the limit of time-reversal ability with intensity information of the phase-conjugate light. Experiment results demonstrated the applicability of the proposed technique to animal tissue.
  • Yamakoshi, Y., Matsumura, K., Yamakoshi, T., Lee, J., Rolfe, P., Kato, Y., Shimizu, K., Yamakoshi, K.-I.
    Journal of Biomedical Optics 22 (6) 1083-3668 2017 [Refereed][Not invited]
     
    The aim of this study was to discover a simple/convenient geometrical arrangement of radiation sources and detector to acquire finger-photoplethysmograms (PPGs) with wavelength regions of blood glucose (BGL) absorption, toward practical noninvasive BGL measurement. First, we compared PPGs with three wavelengths: 808 nm (without water absorption), 1160 nm (with weak water absorption), and 1600 nm (with nearly peak BGL absorption and strong water absorption), while the source-detector spacing was successively increased circumferentially around a fingertip. In 10 healthy subjects, we observed clear cardiac-related pulsatile components of PPG signals at 808 and 1160 nm in any incident positions with more than 15 dB of signal-to-noise ratio (S/N), but reliable PPG detections at 1600 nm with more than 10 dB of S/N was only possible when the source-detector distance was less than 3mm around the fingertip circumference. Second, with this arrangement, an experiment was performed using six wavelengths to cover glucose absorption bands (from 1550 to 1749 nm), obtaining pulsatile PPG signals with more or less 15 dB of S/N. Through the present experiments, this orthogonal arrangement of the source and detector to detect forward-and side-scattered radiation through the tissue is appropriate for PPG measurements with wavelength regions where there is potential for BGL measurement. (C) The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License.
  • Toda, S., Kato, Y., Kudo, N., Shimizu, K.
    Transactions of Japanese Society for Medical and Biological Engineering 54 (PROC) 2016 [Refereed][Not invited]
  • Kazuhiro Nishida, Takeshi Namita, Yuji Kato, Koichi Shimizu
    Progress in Biomedical Optics and Imaging - Proceedings of SPIE 9319 1605-7422 2015 [Refereed][Not invited]
     
    We have proposed a new nonlinear inversion technique to estimate the spatial distribution of the absorption coefficient (μa) in the depth direction of a turbid medium by spatially resolved backscattering measurement. With this technique, we can obtain cross-sectional image of μa as deep as the backscattered light traveled even when the transmitted light through the medium cannot be detected. In this technique, the depth distribution of absorption coefficient is determined by iterative calculation using the spatial path-length distribution (SPD) of traveled photons as a function of source-detector distance. In this calculation, the variance of path-length of many photons in each layer is also required. The SPD and the variance of path-length are obtained by Monte Carlo simulation using a known reduced scattering coefficient (μs€™). Therefore, we need to know the μs€™ of the turbid medium beforehand. We have shown in computer simulation that this technique works well when the μs€™ is the typical values of mammalian body tissue, or 1.0 /mm. In this study, the accuracy of the μa estimation was analyzed and its dependence on the μs€™ was clarified quantitatively in various situations expected in practice. 10% deviations in μs€™ resulted in about 30% error in μa estimation, in average. This suggested that the measurement or the appropriate estimation of μs€™ is required to utilize the proposed technique effectively. Through this analysis, the effectiveness and the limitation of the newly proposed technique were clarified, and the problems to be solved were identified.
  • Tran, T.N., Yamamoto, K., Namita, T., Kato, Y., Shimizu, K.
    Biomedical Optics Express 5 (5) 1321 - 1335 2156-7085 2014 [Refereed][Not invited]
     
    To realize three-dimensional (3D) optical imaging of the internal structure of an animal body, we have developed a new technique to reconstruct optical computed tomography (optical CT) images from two-dimensional (2D) transillumination images. In transillumination imaging of an animal body using near-infrared light, the image is blurred because of the strong scattering in the tissue. To overcome this problem, we propose a novel technique to apply the point spread function (PSF) for a light source located inside the medium to the transilluminated image of light-absorbing structure. The problem of the depth-dependence of PSF was solved in the calculation of the projection image in the filtered back-projection method. The effectiveness of the proposed technique was assessed in the experiments with a model phantom and a mouse. These analyses verified the feasibility of the practical 3D imaging of the internal light-absorbing structure of a small animal. (C) 2014 Optical Society of America
  • Yamamoto, K., Tran, T.N., Namita, T., Kato, Y., Shimizu, K.
    Transactions of Japanese Society for Medical and Biological Engineering 52 150 - O-151 1347-443X 2014 [Refereed][Not invited]
     
    To attain high spatial-resolution in transillumination imaging with near-infrared light, a new technique was developed to estimate the depth of the absorber in turbid medium by convolution operation with a point spread function (PSF). We choose two wavelength at which the scattering property of the medium is different. The transillumination image at one of the wavelength is convolved with the PSF of another wavelength. Two images of alternative wavelengths are compared while changing the depth of the PSF. We can obtain the correct depth that gives minimum difference between the two convoluted images. This technique does not require the repetition of the unstable deconvolution operation. The effectiveness of the proposed technique was verified in experiments.
  • Tanaka, H., Namita, T., Kato, Y., Shimizu, K.
    Transactions of Japanese Society for Medical and Biological Engineering 52 141 - O-142 1347-443X 2014 [Refereed][Not invited]
     
    Transillumination image becomes blurred significantly by the strong scattering of biological tissue. Analyzing the beam wave propagation inside the scattering medium, we have shown possibility to improve the transillumination image in the beam-incident case. However, uniformity of the background was still insufficient. In a plane-wave incident case, the original image is effectively restored by inverting the transillumination image before the PSF deconvolution. In this paper, we newly introduced this principle to the case with inhomogeneous light beam illumination. We combined the background homogenization and the scattering suppression processes into a simple equation. The effectiveness of this technique was confirmed in experiments.
  • Yokoyama, N., Oba, K., Namita, T., Kato, Y., Shimizu, K.
    Transactions of Japanese Society for Medical and Biological Engineering 52 143 - O-144 1347-443X 2014 [Refereed][Not invited]
     
    With the view toward the realization of optical CT imaging, we have developed the simultaneous estimation technique of scattering (μ'< inf> s< /inf> ) and absorption (μ< inf> a< /inf> ) distributions and verified the feasibility in simulation. The usefulness of the proposed technique was verified in experiment with three-layer-structure models. The μ< inf> a< /inf> estimation error was less than 20% in the range of μ'< inf> s< /inf> = 0.75 – 2 /mm. Through this analysis, the usefulness of the proposed technique was verified.
  • Sasaki, H., Ogawa, D., Namita, T., Kato, Y., Shimizu, K.
    Transactions of Japanese Society for Medical and Biological Engineering 52 148 - O-149 1347-443X 2014 [Refereed][Not invited]
     
    To improve the transcutaneous fluorescent image of an animal body, we derived a point-spread function (PSF) at a cylindrical surface of a turbid medium. In this technique, distortion problem of the restored shape remained. For this problem, new scattering suppression technique using the PSFs divided into the symmetric and asymmetric components was developed. The usefulness of the proposed technique was examined in experiment with biological tissue. The internal fluorescent object, which was hardly seen in the image from observed images, became visible by the proposed technique. Through this analysis, the applicability of the proposed technique to biological tissues was verified.
  • Natsume, Y., Namita, T., Kato, Y., Kitama, M., Shimizu, K.
    Transactions of Japanese Society for Medical and Biological Engineering 52 126 - O-127 1347-443X 2014 [Refereed][Not invited]
     
    For transcutaneous imaging of arteriovenous fistula in dialysis treatment, we have developed a technique to improve the transillumination image. In this technique, we obtain an appropriate point spread function (PSF) using a fluorescent source implanted near the fistula inside the body. The effectiveness of the proposed technique was examined in the experiment using the model phantom with known internal structure. The possibility to detect the diameter-change in blood vessel by suppressing image deterioration caused by the scattering effect was confirmed. The applicability to animal tissue was also verified in the experiment.
  • Oba, K., Yokoyama, N., Namita, T., Kato, Y., Shimizu, K.
    Transactions of Japanese Society for Medical and Biological Engineering 52 146 - O-147 1347-443X 2014 [Refereed][Not invited]
     
    We have developed a technique to estimate the absorption coefficient (μ < inf> a< /inf> ) distribution of turbid medium using the backscattered light, and verified its feasibility in simulations and experiments. For accurate estimation of μa, accurate scattering property (μ'< inf> s< /inf> ) is essential. Here, we newly developed the simultaneous estimation technique for μ'< inf> s< /inf> and μ < inf> a< /inf> by attaching the diffuser plate with known μ'< inf> s< /inf> and μ < inf> a< /inf> . The validity of the proposed technique was verified in simulation. The accuracy was apparently improved.
  • Trung Nghia Tran, Kohei Yamamoto, Takeshi Namita, Yuji Kato, Koichi Shimizu
    Progress in Biomedical Optics and Imaging - Proceedings of SPIE 8952 1605-7422 2014 [Refereed][Not invited]
     
    To realize three-dimensional (3D) optical imaging of the internal structure of animal body, we have developed a new technique to reconstruct CT images from two-dimensional (2D) transillumination images. In transillumination imaging, the image is blurred due to the strong scattering in the tissue. We had developed a scattering suppression technique using the point spread function (PSF) for a fluorescent light source in the body. In this study, we have newly proposed a technique to apply this PSF for a light source to the image of unknown light-absorbing structure. The effectiveness of the proposed technique was examined in the experiments with a model phantom and a mouse. In the phantom experiment, the absorbers were placed in the tissue-equivalent medium to simulate the light-absorbing organs in mouse body. Near-infrared light was illuminated from one side of the phantom and the image was recorded with CMOS camera from another side. Using the proposed techniques, the scattering effect was efficiently suppressed and the absorbing structure can be visualized in the 2D transillumination image. Using the 2D images obtained in many different orientations, we could reconstruct the 3D image. In the mouse experiment, an anesthetized mouse was held in an acrylic cylindrical holder. We can visualize the internal organs such as kidneys through mouse's abdomen using the proposed technique. The 3D image of the kidneys and a part of the liver were reconstructed. Through these experimental studies, the feasibility of practical 3D imaging of the internal light-absorbing structure of a small animal was verified. © 2014 SPIE.
  • Kazuhiro Nishida, Takeshi Namita, Yuji Kato, Koichi Shimizu
    Progress in Biomedical Optics and Imaging - Proceedings of SPIE 8578 1605-7422 2013 [Refereed][Not invited]
     
    To estimate the depth distribution of the absorption coefficient in a turbid medium, a new nonlinear inversion technique was developed. It can resolve important shortcomings of the nonlinear error of conventional linear inversion techniques. First, a turbid medium is divided into imaginary layers with arbitrary thickness. The spatial pathlength distribution (SPD) is obtained for each layer in the Monte Carlo simulation as a function of source-detector distance. In the integral operation using SPDs, we can obtain the absorption coefficient of each layer, or the depth distribution of absorption. This inversion process is based on the assumption that the light attenuation is linear with respect to the small pathlength of a photon. However, if we consider the variance of pathlength of many photons in each layer, then this assumption produces nonlinear error. We developed a technique to solve this problem in the following three steps. First, the initial values of absorption coefficient of each layer are obtained using a conventional linear inverse matrix assuming that variance of pathlength of many photons does not exist. Then, improved absorption coefficients are obtained with these initial values and the pathlength variance of many photons using the same matrix. In this way, the nonlinear error is corrected. Repeating this process, the improved absorption coefficient approaches a true value. The effectiveness of the proposed technique was confirmed in the Monte Carlo simulation. The effect of measurement noise was analyzed in the simulation. © 2013 Copyright SPIE.
  • Tran Trung Nghia, Takeshi Namita, Yuji Kato, Koichi Shimizu
    IFMBE Proceedings 40 22 - 24 1680-0737 2013 [Refereed][Not invited]
     
    Using an array of near-infrared (NIR) LED's, we can obtain transillumination images of an animal body and visualize the veins and arteries in the adult forearm as thick as 6 cm. To examine the feasibility of three dimensional (3D) reconstruction using these transillumination images, experiments were conducted to evaluate the image of an absorber in a tissue-equivalent phantom. An experimental system was designed to obtain a transillumination image of a model of blood vessels in the adult forearm. Imaging was accomplished with a high-resolution cooled digital CCD camera, placed at the opposite side of the phantom to the light source. The transillumination images were obtained with different depths of the absorber from the container wall. © 2013 IFMBE.
  • K. Shimizu, N. Tobisawa, T. T. Nghia, T. Namita, Y. Kato
    IFMBE Proceedings 40 13 - 16 1680-0737 2013 [Refereed][Not invited]
     
    A technique of near-infrared (NIR) transillumination imaging was applied to develop an injection assist system. We have developed a simultaneous observation system for a body surface image and a transillumination image of blood vessels. The system consists of a high-intensity and low-leak light source, near-infrared CMOS camera and a small and light one-eye head mounted display. In transillumination imaging, we could visualize the veins in the adult forearm with the thickness of as much as 67 mm. A model phantom of the veins in the forearm was fabricated with the blood-contained tubes buried in pork thigh meat. The blood tube was hardly observable with a naked eye. Using the developed system, we could identify the blood tube in the NIR transillumination image, and could extract the blood successfully with the assist of the NIR image. © 2013 IFMBE.
  • Naoya Tobisawa, Takeshi Namita, Yuji Kato, Koichi Shimizu
    5th International Conference on Bioinformatics and Biomedical Engineering, iCBBE 2011 2011 [Refereed][Not invited]
     
    To assist vascular injection, we have developed a simultaneous observation system for a body surface image and a transillumination image of blood vessels. The system consists of a high-intensity and low-leak light source, near-infrared CMOS camera and a small and light one-eye head mounted display. Using the developed system, we could obtain the transillumination images in all part of the adult forearm with as much as 67 mm thickness. In addition to the superficial veins, we could visualize the arteries in the forearm. © 2011 IEEE.
  • Moto Shimano, Takeshi Namita, Yuji Kato, Koichi Shimizu
    2011 Symposium on Photonics and Optoelectronics, SOPO 2011 2011 [Refereed][Not invited]
     
    To see through a turbid medium, an imaging technique was developed to reconstruct a three-dimensional structure inside the medium. Clear transillumination images were obtained with a scattering suppression technique in which the weakly scattered light component is extracted from the strongly diffused light. The possibility of the proposed technique was examined in the experiment using the turbid medium with known internal structure. Through the experimental analysis, the feasibility of the proposed technique and the effectiveness of the scattering suppression were verified. © 2011 IEEE.
  • Takeshi Namita, Masafumi Otani, Yuji Kato, Koichi Shiniizu
    2011 Int. Quantum Electron. Conf., IQEC 2011 and Conf. Lasers and Electro-Optics, CLEO Pacific Rim 2011 Incorporating the Australasian Conf. Optics, Lasers and Spectroscopy and the Australian Conf. 701 - 703 2011 [Refereed][Not invited]
     
    To reconstruct cross-sectional absorption distribution of diffuse medium, a new technique to estimate non-absorbing temporal point spread function in time-resolved measurement was developed. The feasibility and effectiveness were verified in Monte Carlo simulation. © 2011 IEEE.
  • KATO Yuji, SHIMIZU Koichi
    The IEICE transactions on information and systems (Japanese edetion) 一般社団法人電子情報通信学会 92 (6) 944 - 950 1880-4535 2009/06 [Refereed][Not invited]
     
    生体内の構造情報及び機能情報を取得することを目指し,光と超音波を共用した新たな計測手法を提案し,基礎的検討を行った.超音波で散乱体内の伝搬光を変調し,低コヒーレンス光干渉法を用いることにより,変調部位の光学情報を得ることができる.まず,本手法を実現する実験システムを構築し,超音波変調信号の検出可能性を確かめた.また,検出信号の散乱体内伝搬経路を調べ,本手法によって散乱の影響を抑制しつつほぼ直線的に伝搬する光のみを抽出できることを確かめた.更に本手法による吸光度計測を試み,散乱媒質内であっても吸光度の定量計測が可能なことを示した.また,光源のコヒーレンス長と検出信号強度の関係の評価より,コヒーレンス長の増加により計測深度が深くなる可能性が明らかとなった.更に,生体軟組織を模擬したファントムを用い,本手法により散乱係数または屈折率不連続界面が検出可能なことを示した.これらより提案手法の有効性が明らかになった.
  • K. Takagi, Y. Kato, K. Shimizu
    Appl. Opt. 48 (10) D36  0003-6935 2009/04 [Refereed][Not invited]
  • Takeshi Namita, Yuji Kato, Koichi Shimizu
    APPLIED OPTICS 48 (10) D208 - D217 1559-128X 2009/04 [Refereed][Not invited]
     
    Backscattered light was used to reconstruct cross-sectional images of absorption distributions in diffuse media. For efficient and accurate reconstruction, the inverse problem was solved for one dimension, thereby yielding the absorption distribution in a depth direction. A cross-sectional image or three-dimensional structure is reconstructed by shifting a source-detector pair along the object surface. The object is divided into imaginary layers to solve the inverse problem. This solution's accuracy is further improved by solving the problem for two groups of layers successively instead of solving for all layers simultaneously The technique's effectiveness was verified using solid phantoms and biological tissues. (C) 2009 Optical Society of America
  • Namita, T., Kato, Y., Shimizu, K.
    Applied Optics 48 (10) D208  0003-6935 2009 [Refereed][Not invited]
  • Takagi, K., Kakinuma, H., Kato, Y., Shimizu, K.
    Optics Express 17 (10) 8332 - 8342 1094-4087 2009 [Refereed][Not invited]
     
    Transmitted light through a diffuse scattering medium includes strongly diffused light (SDL) and weakly scattered light (WSL). To realize clear transillumination imaging through thick body tissue, which is typically more than 10 mm, we developed a technique to extract the WSL component from diffused light. In experiments using a 15-mm-thick scattering medium (mu(s)' = 1.0/mm), the cross-section of the light propagation area at the center of the medium was confined to a 50% area. This method's usefulness was demonstrated by transillumination imaging through a 40-mm-thick piece of chicken meat. The possibility of depth evaluation was also verified. (C) 2009 Optical Society of America
  • Takagi, K., Kato, Y., Shimizu, K.
    Applied Optics 48 (10) D36 - D44 1559-128X 2009 [Refereed][Not invited]
     
    To suppress the scattering effect in transillumination imaging, a technique was developed to extract a near-axis scattered light (NASL) component from diffused light through a scattering medium. A diffuser is inserted between the light source and the incident surface of a scattering medium. We can extract the NASL component by subtracting the light intensity at the output surface with a diffuser from that without a diffuser. The principle to determine the subtraction weight was presented. In experiments using model phantoms of mammalian tissue, the proposed technique's effectiveness was verified. The cross-section of the propagation area of scattered light was confined to an 8% area around the optical axis of the incident light beam. The usefulness of this technique was demonstrated by transillumination imaging of the blood column through a diffuse medium. (C) 2009 Optical Society of America
  • Kazuto Takagi, Hiroyuki Kakinuma, Yuji Kato, Koichi Shimizu
    2009 3RD INTERNATIONAL CONFERENCE ON BIOINFORMATICS AND BIOMEDICAL ENGINEERING, VOLS 1-11 1829 - 1832 2009 [Refereed][Not invited]
     
    Transmitted light through a diffuse scattering medium includes strongly diffused light (SDL) and weakly scattered light (WSL). To realize clear transillumination imaging through thick body tissue, which is typically more than 10 mm, we developed a technique to extract the WSL component from diffused light. A diffuser is placed on the incident surface of a scattering medium. We can extract the WSL component by subtracting the light intensity at the output surface with a diffuser from that without a diffuser. In CW measurements using a 15-mm-thick scattering medium (reduced scattering coefficient mu(s)' = 1.0/mm), the spatial intensity distribution of the scattered light at the output surface was confined to an approximately 50% area by the proposed technique. It was confirmed in a time-resolved measurement that the earlier time component with a smaller temporal spread was extracted by the proposed technique.
  • CT imaging of biological tissue using backscattered light
    T. Namita, Y. Kato, K. Shimizu
    Biomedical Optics, BIOMED 2008 BMD35  2008/03 [Refereed][Not invited]
  • K Shimizu, K Tochio, Y Kato
    APPLIED OPTICS 44 (11) 2154 - 2161 1559-128X 2005/04 [Refereed][Not invited]
     
    The point-spread function (PSF) for transcutaneous fluorescent imaging was obtained as an analytical solution in a closed form. It is applicable to cases in which the optical property of the image-blurring turbid medium is considered to be fairly homogeneous. We proposed a technique to improve a transcutaneous image by using depth-dependent PSF. Contrast of the fluorescent image was improved for depths of 1-15 mm in a scattering medium (mu(s)' = 1/mm). The visible depth was more than doubled with this technique. An experiment with a rat demonstrated considerable improvement of a transcutaneous image of the cerebral vein at a specified depth. The spread image of the heart was reduced to the correct size by use of the PSF with the actual depth of the heart. (c) 2005 Optical Society of America.
  • Shimizu, K., Tochio, K., Kato, Y.
    Applied Optics Optical Society of America 44 (11) 2154 - 2161 0003-6935 2005 [Refereed][Not invited]
     
    The point-spread function (PSF) for transcutaneous fluorescent imaging was obtained as an analytical solution in a closed form. It is applicable to cases in which the optical property of the image-blurring turbid medium is considered to be fairly homogeneous. We proposed a technique to improve a transcutaneous image by using depth-dependent PSF. Contrast of the fluorescent image was improved for depths of 1-15 mm in a scattering medium (µ_s' = 1/mm). The visible depth was more than doubled with this technique. An experiment with a rat demonstrated considerable improvement of a transcutaneous image of the cerebral vein at a specified depth. The spread image of the heart was reduced to the correct size by use of the PSF with the actual depth of the heart.
  • Koichi Shimizu, Ruriko Koizumi, Kazuto Takagi, Yuji Kato
    Pacific Rim Conference on Lasers and Electro-Optics, CLEO - Technical Digest 2005 662 - 663 2005 [Refereed][Not invited]
     
    For transcutaneous fluorescent imaging, a PSF was derived theoretically as an analytical solution in a closed form. In experiments, the validity of the PSF was verified and the effectiveness of scattering-suppression by PSF-deconvolution was confirmed.
  • Koichi Shimizu, Koji Tochio, Yuji Kato
    2005 27TH ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY, VOLS 1-7 3141 - 3144 1094-687X 2005 [Refereed][Not invited]
     
    The transcutaneous fluorescent imaging (TFI) method was applied to the imaging of a small experimental animal such as a rat. The feasibitity of the functional imaging in TFI was verified. To make this method more practical, a technique of scattering suppression was proposed. The depth-dependent PSF was derived as an analytical solution in a closed form. The applicability of this technique to the functional TFI and its usefulness were demonstrated in animal experiments.
  • Derivation of PSF from diffusion equation for transcutaneous fluorescent imaging
    Koichi Shimizu, Ruriko Koizumi, Koji Tochio, Yuji Kato
    Second Asian and Pacific Rim Symposium on Biophotonics - Proceedings, APBP 2004 121 - 122 2004 
    For transcutaneous fluorescent imaging, a point spread function (PSF) was newly derived from the diffusion equation. Using an experimental PSF, the usefulness of the PSF was confirmed in the fluorescent imaging of the rat head. © 2004 IEEE.
  • Murakami, N., Kato, Y., Baba, N., Ishigaki, T.
    Optics Communications 237 (1-3) 2004 [Refereed][Not invited]
  • Koji Akiyama, Yuji Kato, Koichi Shimizu
    Pacific Rim Conference on Lasers and Electro-Optics, CLEO - Technical Digest 2 466  2003 [Refereed][Not invited]
     
    For cross-sectional imaging of animal body using backscattered light, the measurement of depth-distribution of optical absorption is required. A technique has been developed to reconstruct the depth-distribution using the pulse shape of backscattered light obtained in a time-resolved measurement. In this technique, the temporal path-length distribution (TPD) in each arbitrary layer of the scattering object is essential. We have developed a technique to obtain this TPD in a measurement. The feasibility of the proposed technique was verified in a phantom experiment and the cross-sectional imaging with this technique was demonstrated.
  • Awata, A., Kato, Y., Shimizu, K.
    IEICE Transactions on Information and Systems E85-D (1) 124 - 132 0916-8532 2002 [Refereed][Not invited]
     
    A technique was developed to reconstruct the cross-sectional image of the absorption distribution in a diffuse medium using backscattered light. In this technique, we illuminate an object with an ultra-short pulse, and measure the time-resolved pulse shape of the light backscattered from the object. The absorption distribution of the scattering object can be estimated using the propagation-path distribution of photons at each detection time and the optical impulse response of backscattered light. In a simulation, the effectiveness of this technique Wa's verified in the cases of a layered absorber and a three dimensional absorber. The nonlinear relationship between the depth of the probing region and the propagation time was clarified. The accuracy of the image reconstruction was significantly improved by the aperiodic sampling of the backscattered impulse response according to the nonlinear relation. The feasibility of the proposed technique was verified in the experiment with a model phantom.
  • F Sato, Y Kato, M Kitama, K Shimizu
    CLEO(R)/PACIFIC RIM 2001, VOL I, TECHNICAL DIGEST 382 - 383 2001 [Refereed][Not invited]
     
    To realize a quantitative optical CT, a technique was developed to detect near-axis scattered light. Using time-resolved measurement technique, the integrated value of the absorption coefficient along the propagation path was obtained.
  • H Horie, Y Kato, K Shimizu
    CLEO(R)/PACIFIC RIM 2001, VOL I, TECHNICAL DIGEST 360 - 361 2001 [Refereed][Not invited]
     
    To realize optical CT using backscattered light, an algorithm to obtain depth-distribution of absorption coefficient in diffuse medium was newly developed. This technique is based on the time-resolved measurement and the solution of linear equations.
  • Transillumination imaging of physiological functions by NIR light
    Y. Taka, Y. Kato, K. Shimizu
    Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings 1 771 - 774 0589-1019 2000 
    With a near-infrared (NIR) light, we can get transillumination image of a living body. Further, we can quantify the physiological change in the body as the change in light attenuation. A fundamental study has been conducted to visualize the functional change inside a living biological body using the NIR light. A technique was developed to visualize the attenuation change occurred in a diffuse scattering medium. Transillumination images are obtained before and after the physiological change. By taking the ratio of transmitted intensity of these two images, we can obtain the spatial distribution of attenuation change while suppressing the effect of scattering. This principle was derived in theoretical analysis and its effectiveness was verified in experiments. To examine the applicability of this principle to a biological body, localized physiological changes were made in the mouse abdomen and the rat brain. The hypoxia in one of the mouse kidneys was visualized selectively from another normal kidney. The local increase in the blood volume was detected in the somatosensory area of a rat brain when its forelimb was electrically stimulated. The blood increase occurred in a symmetrical position with respect to the sagittal plane, when the forelimb of the opposite side was stimulated. Through these experiments, it was found that the changes in the tissue oxygenation and the blood volume could be detected noninvasively and that they are visualized in the transillumination images using the NIR light.
  • K Takagi, Y Kato, M Kitama, K Shimizu
    BIOMEDICAL TOPICAL MEETINGS, TECHNICAL DIGEST 38 441 - 443 1094-5695 2000 [Refereed][Not invited]
     
    In the transmitted light through scattering mammalian tissue, there should be a component that traveled along the optical axis of incident light beam. To detect this near-axis scattered component efficiently, we have introduced a time-resolved measurement technique to the previously developed spatially differential technique. With this technique, we can accurately determine the weighting coefficient for the differential process. In addition, we can estimate the increase of the path length in near-axis scattering. Through experimental study, the effectiveness of this technique to detect the near-axis scattered light was verified. (C) 1999 Optical Society of America.
  • TAKA Yoshinori, SAKATANI Kaoru, KATO Yuji, SHIMIZU Koichi
    Med Imaging Technol. 日本医用画像工学会 17 (5) 545 - 555 0288-450X 1999/09 [Refereed][Not invited]
  • K. Shimizu, Y. Taka, K. Sakatani, Y. Kato
    CLEO/Pacific Rim 1999 - Pacific Rim Conference on Lasers and Electro-Optics 4 1235 - 1236 1999 [Refereed][Not invited]
     
    Near-IR light has relatively high transmittance through a biological body. In addition, the important chromophores such as hemoglobin show characteristic absorption spectra in this near-infrared range. Since the physiological change inside the body is often accompanied by the change of blood volume and the blood oxygenation state, we can obtain the functional change inside a living body in a transillumination image. We have conducted the fundamental study for the possibility of the functional imaging of animal body by a laser transillumination technique.
  • Y. Onodera, Y. Kato, K. Shimizu
    CLEO/Pacific Rim 1999 - Pacific Rim Conference on Lasers and Electro-Optics 4 1305 - 1306 1999 [Refereed][Not invited]
     
    The scattering effect in biological tissue is one of the most difficult problems to realize an optical computerised tomography (CT). To suppress the scattering effect in a reconstructed image, a fundamental study has been conducted on the deconvolution technique using a point spread function (PSF). The image blurring due to the scattering can be considered as the convolution of the PSF of a scattering medium. Therefore, if we can find an appropriate PSF, we can suppress the scattering effect by the deconvolution. To improve the deconvolution technique further, we have applied the frequency-distance relation to optical CT reconstruction and examined its effectiveness.
  • A Awata, Y Kato, K Shimizu
    IGARSS '98 - 1998 INTERNATIONAL GEOSCIENCE AND REMOTE SENSING SYMPOSIUM, PROCEEDINGS VOLS 1-5 36 - 38 1998 [Refereed][Not invited]
  • Y Matsuura, H Hiraga, Y Wang, Y Kato, M Miyagi, S Abe, S Onodera
    APPLIED OPTICS 36 (30) 7818 - 7821 0003-6935 1997/10 [Refereed][Not invited]
     
    A new type of launching coupler for small-bore, hollow fibers, consisting of a lens and a tapered hollow waveguide, is proposed to increase the alignment tolerance between an input laser beam and small bore fibers. First, we designed the structural dimensions of the coupler by using a ray-tracing method. Then, a series of experiments employing tapered hollow waveguides made of Pyrex glass was performed to investigate the effectiveness of the new coupler. It is shown that the coupler has a high efficiency with attenuation of around 0.5 dB, especially when the inside of the taper section is coated with a polymer and silver film. In addition, we also show that the coupler has great tolerance for the transverse displacement of a waveguide axis, which gives a 0.1-dB loss increase for a 300-mu m displacement. (C) 1997 Optical Society of America.
  • KUBOTA Satoshi, KATO Yuji, ABE Shinichi, ONODERA Shinji, AKAMA Yosuke, BABA Kazutaka, MIYAGI Mitsunobu
    The Review of laser engineering レ-ザ-学会 25 (6) 438 - 441 0387-0200 1997/06 [Refereed][Not invited]
  • Y Wang, A Hongo, Y Kato, T Shimomura, D Miura, M Miyagi
    APPLIED OPTICS 36 (13) 2886 - 2892 0003-6935 1997/05 [Refereed][Not invited]
     
    The variation in properties of a fluorocarbon polymer (FCP) film during a drying-curing process is investigated for fabricating FCP-coated silver (FCP/Ag) hollow glass waveguides. A dynamic liquid-phase coating procedure is used. Through the analyses of the loss spectra of hollow waveguides made in various conditions, a relationship between the thickness of the FCP film and the coating velocity is obtained. The optimum fabrication condition is also established for producing FCP/Ag hollow glass waveguides for the mid-IR. (C) 1997 Optical Society of America.
  • Onodera, Y., Kato, Y., Shimizu, K.
    Japanese Journal of Medical Electronics and Biological Engineering 日本エム・イー学会 35 (4) 400 - 406 0021-3292 1997 [Refereed][Not invited]
  • H Hiraga, Y Matsuura, Y Wang, Y Kato, M Miyagi, S Abe, S Onodera
    SPECIALTY FIBER OPTICS FOR BIOMEDICAL AND INDUSTRIAL APPLICATIONS, PROCEEDINGS OF 2977 47 - 50 1997 [Refereed][Not invited]
     
    A launching coupler for hollow fibers consisting of a convex lens and a tapered hollow-guide piece is proposed. We fabricated the coupler which has a conical-tapered, Pyrex glass tube as the tapered section. The bore size of the taper-guide's input end is 3 mm and the output end is 0.7 mm which is the same as the size of coupled hollow fibers. The results of preliminary experiments show that the launching system has a large tolerance for the coupling condition between laser light and hollow fibers.
  • 橋新 裕一, 大内田 貴之, 田中 紘幸, 久保 宇市, 四方 淳史, 王 攸, 加藤 祐次, 下村 剛弘, 宮城 光信, 鈴村 将人, 熊崎 建二, 松谷 貴臣, 中山 斌義, 中野 人志, 秋田 大介, 林 琢也, 荒井 恒憲, 野上 弥志郎, 川内 聡子, 矢野 政人, 菊地 眞, 田中 豊之, 仲田 宗弘, 峰久 次郎, 猪 吉輝, 金田 明, 遊津 隆義, 林 潤一, 會沢 勝夫, 陳 建培, 山田 誠, 稲場 文男, 伊藤 晴美, 小原 實, 中島 勇人, 原 煕, 大越 昌幸, 井上 陽子, 豊田 浩一, 村原 正隆, X. Ilyar, 斉藤 光一, 山田 公人, 渋谷 洋, 奥仲 哲弥, 古川 欣也, 酒井 治正, 小中 千守, 加藤 治文, 飯野 徹, 山本 剛, 多加谷 明広, 二瓶 栄輔, 小池 康博, 佐々木 敬介, 南谷 晴之
    レーザー研究 The Laser Society of Japan 24 317 - 326,331 0387-0200 1996
  • M Osawa, Y Kato, T Watanabe, M Miyagi, S Abe, M Aizawa, S Onodera
    OPTICS AND LASER TECHNOLOGY 27 (6) 393 - 396 0030-3992 1995/12 [Refereed][Not invited]
     
    Fluorocarbon polymer-coated silver hollow-glass waveguides have been fabricated based on the method of silver mirror reaction for silver, and the dipping method for the fluorocarbon polymer, The waveguides show low-loss properties for the infrared wavelengths except for the wavelength regions of large absorption of the polymer, Er:YAG laser light has been successfully transmitted through the flexible waveguides with small bending losses.
  • M Saito, T Gojo, Y Kato, M Miyagi
    INFRARED PHYSICS & TECHNOLOGY 36 (7) 1125 - 1129 1350-4495 1995/12 [Refereed][Not invited]
     
    The refractive indices and absorption coefficients of fluorocarbon, polymethyl methacrylate, and polyimide were measured in the wavelength range of 2-12 mu m. The reflection losses of KRS-5 and CsI windows were reduced successfully by coating fluorocarbon polymers on the surfaces.
  • Y KATO, M OSAWA, M MIYAGI, S ABE, M AIZAWA, S ONODERA
    ELECTRONICS LETTERS 31 (1) 31 - 32 0013-5194 1995/01 [Refereed][Not invited]
     
    As durable and nontoxic infra-red waveguides, polyimide-coated silver hollow waveguides have been proposed and fabricated based on the liquid phase coating method in the whole process. Er:YAG laser light has been successfully transmitted through the waveguide with small bending losses.
  • 野村 直人, 中野 人志, 田中 紘幸, 久保 宇市, 橋新 裕一, 大道 雄一郎, 中島 章夫, 荒井 恒憲, 菊地 眞, 辻 明, 小田島 邦男, 中島 史雄, 早川 正道, 中村 宏, 福井 勝, 内海 厚, 野上 弥志郎, 林 琢也, 徳野 慎一, 田中 良昭, 奥森 雅直, 伊藤 晴美, 秋田 大介, 中山 斌義, 仲田 宗弘, 四方 淳史, 山川 禎貴, 加藤 祐次, 大澤 光生, 宮城 光信, 阿部 眞一, 相澤 勝, 小野寺 信治, 中桐 啓太郎, 岡田 昌義, 吉田 正人, 辻 義彦, 山下 輝夫, 森本 真人, 井上 鐵三, 中之坊 学, 田部 哲也, 小倉 雅実, 水野 有武, 北島 具秀, 尾崎 幸洋, 本田 尚葆, 村原 正隆, 堀 清太郎, 松谷 貴臣, 島田 智史
    レーザー研究 The Laser Society of Japan 23 295 - 303,308 0387-0200 1995
  • Y KATO, M MIYAGI
    IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES 42 (12) 2336 - 2342 0018-9480 1994/12 [Refereed][Not invited]
     
    The changes of the mode structures and attenuation constants in dielectric-coated circular metallic hollow waveguides are numerically investigated by solving the exact characteristic equations. It is shown that the mode structures in the small-core waveguides change drastically,vith the thickness of the coated-dielectric.
  • Y KATO, M OSAWA, M MIYAGI, M AIZAWA, S ABE, S ONODERA
    BIOMEDICAL OPTOELECTRONIC DEVICES AND SYSTEMS II, PROCEEDINGS OF 2328 16 - 21 1994 [Refereed][Not invited]
  • Y KATO, M MIYAGI
    PROCEEDINGS OF BIOMEDICAL OPTOELECTRONIC DEVICES AND SYSTEMS 2084 27 - 34 1994 [Refereed][Not invited]
  • Y KATO, M OSAWA, M MIYAGI, M AIZAWA, S ABE, S ONODERA
    BIOMEDICAL FIBER OPTIC INSTRUMENTATION, PROCEEDINGS OF 2131 4 - 10 1994 [Refereed][Not invited]
  • Y KATO, M MIYAGI
    IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES 41 (4) 733 - 736 0018-9480 1993/04 [Refereed][Not invited]
     
    Correspondence between hybrid modes in small and large core circular hollow waveguides is discussed by using an asymptotic theory for the infrared. The mode changes or mode transitions in several hollow waveguides are discussed which depend on the cladding material and the mode order. For the dielectric-coated metallic waveguides, mode changes also depend on the thickness of the coated dielectric. For the singly cladded hollow waveguides, the region is shown in the plane of complex refractive index (n - jk) of cladding material where the HE11 mode in large core waveguides approaches the TE or TM mode.
  • Yuj i KATO, Mitsunobu MIYAGI
    Journal of the Surface Finishing Society of Japan The Surface Finishing Society of Japan 43 (8) 750 - 754 0915-1869 1992/08 [Refereed][Invited]
  • Y KATO, M MIYAGI
    IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES 40 (4) 679 - 685 0018-9480 1992/04 [Refereed][Not invited]
     
    The mode structures and attenuation constants in circular hollow waveguides are evaluated numerically based on the exact characteristic equations. Mode properties, which are strongly dependent on waveguide materials, and attenuation constants are discussed when the core diameter becomes small. Special modes are also analyzed in oversized metallic waveguides which approach very familiar modes in perfect-conducting cylindrical waveguides when the core diameter becomes mall.
  • Yuji Kato, Mitsunobu Miyagi
    Applied Optics 30 (27) 3790 - 3791 2155-3165 1991/09/20 [Refereed][Not invited]
     
    Attenuation constants in circular hollow waveguides are numerically evaluated based on the exact characteristic equation. Mode transition takes place when waveguides become thinner. © 1991 Optical Society of America.
  • Y KATO, M MIYAGI
    APPLIED OPTICS 30 (27) 3790 - 3792 0003-6935 1991/09 [Refereed][Not invited]
     
    Attenuation constants in circular hollow waveguides are numerically evaluated based on the exact characteristic equation. Mode transition takes place when waveguides become thinner.
  • 加藤 祐次
    電子情報通信学会論文誌 C-(0xF9C1) エレクトロニクス (0xF9C1)-光・波動 電子情報通信学会エレクトロニクスソサイエティ 73 (6) p481 - 483 0915-1893 1990/06 [Refereed][Not invited]

MISC

  • 加藤祐次  電気学会研究会資料(Web)  (MBE-21-035.037.039.041)  2021
  • 加藤祐次  電子情報通信学会技術研究報告(Web)  121-  (77(MBE2021 6-11))  2021
  • 体動アーチファクトが波長および測定モードの異なる光電容積脈波に与える影響
    松村 健太, 任田 崇吾, 加藤 祐次  電子情報通信学会技術研究報告(MEとバイオサイバネティックス)  120-  (62)  9  -11  2020/06  
    本研究では、10Hz以上の体動アーチファクト成分が波長および測定モードの異なる光電容積脈波に与える影響について調べた。用いた光源は青、緑、赤、近赤外の4種のLEDであり、測定モードは反射と透過の2種とした。12人の被験者を対象に指振り実験を行い、心拍数帯域を信号、10〜20Hzをノイズとして、脈波波形のS/N比を求めた。その結果、S/N比は高い方から、緑色反射型、青色反射型、近赤外反射型、近赤外透過型、赤色反射型、赤色透過型の順であった。これより、体動アーチファクトに高周波成分が含まれる場合でも、緑色あるいは青色反射型、近赤外反射型を用いるのが良いと分かった。(著者抄録)
  • 体動アーチファクトが波長および測定モードの異なる光電容積脈波に与える影響
    松村 健太, 任田 崇吾, 加藤 祐次  電子情報通信学会技術研究報告(MEとバイオサイバネティックス)  120-  (62)  9  -11  2020/06  
    本研究では、10Hz以上の体動アーチファクト成分が波長および測定モードの異なる光電容積脈波に与える影響について調べた。用いた光源は青、緑、赤、近赤外の4種のLEDであり、測定モードは反射と透過の2種とした。12人の被験者を対象に指振り実験を行い、心拍数帯域を信号、10〜20Hzをノイズとして、脈波波形のS/N比を求めた。その結果、S/N比は高い方から、緑色反射型、青色反射型、近赤外反射型、近赤外透過型、赤色反射型、赤色透過型の順であった。これより、体動アーチファクトに高周波成分が含まれる場合でも、緑色あるいは青色反射型、近赤外反射型を用いるのが良いと分かった。(著者抄録)
  • ディジタル位相共役光による散乱抑制におけるコヒーレンス長の影響
    任田 崇吾, 加藤 祐次, 清水 孝一  電子情報通信学会技術研究報告(MEとバイオサイバネティックス)  119-  (97)  11  -15  2019/06  
    光イメージングにおいて、生体組織の光散乱特性は透視像を劣化させるため、大きな問題となる。我々は散乱抑制にディジタル位相共役光を利用した生体内部構造の透視イメージングの実現を目指している。今回は、以前に比べコヒーレンス長の長い光源を用い、提案手法による散乱抑制能に対する光源コヒーレンス長の影響を明らかにした。また、散乱体の散乱係数および厚さを変えながら、散乱体通過後の光から通過前の光形状復元を行った。その結果より、長コヒーレンス長光源を用いて開発したシステムの適用範囲を明らかにするとともに、適用範囲の決定要因を明確化した。(著者抄録)
  • 光による生体内部3次元透視イメージングおよび機能イメージングの実現
    清水 孝一, 加藤 祐次, 北間 正崇, 立野 繁之  福田記念医療技術振興財団情報  (31)  133  -139  2018/12
  • 加藤 祐次, 宮島 文佳, 清水 孝一  レーザー学会研究会報告 = Reports on topical meeting of the Laser Society of Japan  17-  (13)  27  -32  2017/08/04
  • 後方散乱光を用いた血中トリグリセリド濃度の非侵襲的計測法 予備的検証
    松村 健太, 加藤 祐次, 飯永 一也, 清水 孝一  脂質栄養学  26-  (2)  208  -208  2017/08
  • 光透視による支台歯マージン形状の検出の試み(第3報)
    上田 康夫, 加藤 祐次, 山口 泰彦, 清水 孝一  日本補綴歯科学会誌  9-  (特別号)  235  -235  2017/06
  • Sogo Toda, Yuji Kato, Nobuki Kudo, Koichi Shimizu  Proceedings of SPIE - The International Society for Optical Engineering  10251-  2017  [Not refereed][Not invited]
     
    For transillumination imaging of an animal body, we have attempted to suppress the scattering effect in a turbid medium. It is possible to restore the optical image before scattering using phase-conjugate light. We examined the effect of intensity information as well as the phase information for the restoration of the original light distribution. In an experimental analysis using animal tissue, the contributions of the phase-and the intensity-information to the image restoration through turbid medium were demonstrated.
  • 上田康夫, 加藤祐次, 山口泰彦, 清水孝一  日本補綴歯科学会誌(Web)  9-  2017
  • 宮島 文佳, 加藤 祐次, 清水 孝一  電子情報通信学会技術研究報告 = IEICE technical report : 信学技報  115-  (513)  77  -81  2016/03/22
  • 任田 崇吾, 加藤 祐次, 清水 孝一  電子情報通信学会技術研究報告 = IEICE technical report : 信学技報  115-  (513)  83  -88  2016/03/22
  • 岡崎 恵祐, 加藤 祐次, 清水 孝一  電子情報通信学会技術研究報告 = IEICE technical report : 信学技報  115-  (513)  107  -112  2016/03/22
  • 王 磊, 飯永 一也, 加藤 祐次, 清水 孝一  電子情報通信学会技術研究報告 = IEICE technical report : 信学技報  115-  (513)  101  -106  2016/03/22
  • HIRAKIDA Shoichi, MATSUMURA Kenta, KATO Yuji, SHIMIZU Koichi  IEICE technical report. ME and bio cybernetics  114-  (514)  29  -33  2015/03/16  
    The personal authentication with blood vessel image of a finger or a palm has been commonly used in many areas. But the blood vessel image of the wrist has not been used for personal authentication. Recently, wristwatch type wearable devices are becoming common, and the personal authentication at the wrist would be very useful. To answer this demand, we have devised a technique to realize the personal authentication using the transillumination image of the blood vessels at the wrist with a watch-type wearable device. In experiments, the transillumination images were obtained at the adult wrists, and the personal authentication was attempted by the relatively simple algorithm that can be easily implemented in a wearable device. Through these analyses, the feasibility of the personal authentication at the wrist with a wearable device was verified.
  • SASAKI Hirotaka, NAMITA Takeshi, KATO Yuji, SHIMIZU Koichi  IEICE technical report. ME and bio cybernetics  114-  (514)  41  -46  2015/03  [Not refereed][Not invited]
     
    To improve the transcutaneous fluorescent image of an animal body, we derived a point-spread function (PSF) at a cylindrical surface of a diffuse scattering medium. For practical applications, a new CT algorithm was developed. In this technique, an orthogonal function system was used to reconstruct tomographic image. The feasibility of the proposed technique was verified in the simulation and experiments.
  • 田中 宏幸, 浪田 健, 加藤 祐次  電子情報通信学会技術研究報告 = IEICE technical report : 信学技報  114-  (514)  35  -40  2015/03  [Not refereed][Not invited]
  • 関 大輔, 浪田 健, 加藤 祐次  電子情報通信学会技術研究報告 = IEICE technical report : 信学技報  114-  (514)  47  -52  2015/03  [Not refereed][Not invited]
  • SEKI DAISUKE, NAMITA TAKESHI, KATO YUJI, SHIMIZU KOICHI  Transactions of Japanese Society for Medical and Biological Engineering  53-  S176_03  -S176_03  2015  
    To realize practical optical communication through human body, an experimental study was conducted using the near-infrared light through a human hand. A wrist-watch type light transmitter was made and the possibility of the optical signal transmission from the wrist to the fingertip was confirmed. A practical light receiver was installed in a door-knob. Fig.1 shows a wearable light transmitter and a door-knob type receiver. The feasibility of the optical data transmission through the adult hand was verified. The optical radiation from the hand was found to be confined in close proximity (within 100 mm range) of the hand. This controllability of radiation guarantees high security in practice.
  • OKAZAKI KEISUKE, KATO YUJI, SHIMIZU KOICHI  Transactions of Japanese Society for Medical and Biological Engineering  53-  S218_01  -S218_01  2015  
    The depth-dependent point spread function (PSF) is useful to improve the transillumination image blurred by the strong scattering in body tissue. We have proposed a technique to estimate the depth of an absorber by the PSF convolution of the images in different wavelengths. To evaluate the effectiveness of this technique, experiments were conducted. An absorber was placed at 2 mm depth in a scattering medium with 40 mm thickness. The proposed technique was applied to the images at 760 nm and 800 nm wavelengths. Fig.1 shows an example of the results. A correlation peak was observed near the given depth of the absorber. In these analyses, the feasibility of the proposed technique was verified.
  • MIYAJIMA FUMIKA, KATO YUJI, SHIMIZU KOICHI  Transactions of Japanese Society for Medical and Biological Engineering  53-  S217_03  -S217_03  2015  
    In 3D optical imaging of a living body with near-infrared light, image deterioration caused by scattering effect is a fundamental and serious problem. To solve this problem, we have newly developed a technique to reconstruct a CT image from tranillumination images with scattering suppression. In an experiment, the effectiveness of the developed technique was verified. The cause of the reconstruction error was found to be not from the technique itself but from the artefact of the experiment. Figure 1 shows the cross sectional images of 10 mm∅ perfect absorber in a scattering medium (μ's =1.0 /mm). The size and the position of the absorber were restored correctly using the proposed technique.
  • SASAKI HIROTAKA, NAMITA TAKESHI, KATO YUJI, SIMIZU KOICHI  Transactions of Japanese Society for Medical and Biological Engineering  53-  S216_01  -S216_01  2015  
    To improve the transcutaneous fluorescent image of an animal body, we derived a point-spread function (PSF) at a cylindrical surface of a turbid medium. For practical applications, a new CT algorithm was developed. In this technique, an orthogonal function system was used to reconstruct tomographic image. The usefulness of the proposed technique was examined in experiment with tissue- simulated phantom. Figure 1 shows the result of tomographic reconstruction. The internal fluorescent objects, which are hardly seen in Fig. 1(a), became visible by the proposed technique. Through this analysis, the applicability of the proposed technique was verified.
  • TANAKA HIROYUKI, NAMITA TAKESHI, KATO YUJI, SHIMIZU KOICHI  Transactions of Japanese Society for Medical and Biological Engineering  53-  S216_03  -S216_03  2015  
    We have analyzed the beam-wave propagation in random media, and applied it to the transillumination imaging using practically useful light-beam illumination. In light-beam illumination, it is difficult to distinguish the absorber in a transillumination image. The effectiveness of proposed scattering suppression was examined when the absorber existed in off-axis area. Fig. 1 shows the result with the absorber in 10 mm depth from the an observation plane and 20 mm from the light axis. Using the proposed technique, we can recognize the absorber in the transillumination image even if we cannot recognize it in the observed image. The effectiveness of the proposed technique was verified.
  • WANG LEI, IINAGA KAZUYA, KATO YUJI, SHIMIZU KOICHI  Transactions of Japanese Society for Medical and Biological Engineering  53-  S217_01  -S217_01  2015  
    For the diagnosis of postprandial hyperlipidemia, it is necessary to measure the temporal change of the serum triglyceride level by sampling the blood frequently. To solve this problem, we have developed an optical technique to evaluate the scattering property of the blood serum noninvasively. The scattering coefficient can be measured by the spatially resolved measurement of backscattered light with the diffusion approximation for light propagation. However, this approximation is not necessarily valid for the blood. Figure 1 shows the result of the Monte Carlo simulation. It shows that we can estimate the scattering coefficient accurately even with the human blood (μa=0.5/mm).
  • TODA SOGO, KATO YUJI, SHIMIZU KOICHI  Transactions of Japanese Society for Medical and Biological Engineering  53-  S216_02  -S216_02  2015  
    To suppress the scattering of light in a transillumination image, a new imaging technique using time-reverse technique with phase conjugate light has been reported. We have proposed the possibility of biological transillumination imaging using digital phase conjugate light generated with a spatial light modulator. In experiment, we attempted to restore the incident light image from the light passed through a scattering layer. Figure 1 shows the image of the incident light (a) and the observed image (b) through the scattering layer. The feasibility to generate appropriate phase conjugate light was verified as shown in Fig. 1(c).
  • Kazuhiro Nishida, Takeshi Namita, Yuji Kato, Koichi Shimizu  OPTICAL TOMOGRAPHY AND SPECTROSCOPY OF TISSUE XI  9319-  2015  [Refereed][Not invited]
     
    We have proposed a new nonlinear inversion technique to estimate the spatial distribution of the absorption coefficient (mu(a)) in the depth direction of a turbid medium by spatially resolved backscattering measurement. With this technique, we can obtain cross-sectional image of mu(a) as deep as the backscattered light traveled even when the transmitted light through the medium cannot be detected. In this technique, the depth distribution of absorption coefficient is determined by iterative calculation using the spatial path-length distribution (SPD) of traveled photons as a function of source-detector distance. In this calculation, the variance of path-length of many photons in each layer is also required. The SPD and the variance of path-length are obtained by Monte Carlo simulation using a known reduced scattering coefficient (mu(s)'). Therefore, we need to know the mu(s)' of the turbid medium beforehand. We have shown in computer simulation that this technique works well when the mu(s)' is the typical values of mammalian body tissue, or 1.0 /mm. In this study, the accuracy of the mu(a) estimation was analyzed and its dependence on the mu(s)' was clarified quantitatively in various situations expected in practice. 10% deviations in mu(s)' resulted in about 30% error in mu(a) estimation, in average. This suggested that the measurement or the appropriate estimation of mu(s)' is required to utilize the proposed technique effectively. Through this analysis, the effectiveness and the limitation of the newly proposed technique were clarified, and the problems to be solved were identified.
  • TANAKA HIROYUKI, NAMITA TAKESHI, KATO YUJI, SHIMIZU KOICHI  Optics & Photonics Japan講演予稿集(CD-ROM)  2014-  ROMBUNNO.6AA7  2014/10  [Not refereed][Not invited]
  • TRAN Trung Nghia, Yamamoto Kohei, Namita Takeshi, Kato Yuji, Shimzu Koichi  IEICE technical report. ME and bio cybernetics  114-  (79)  71  -76  2014/06  [Not refereed][Not invited]
     
    To realize three-dimensional optical imaging using transillumination images, we developed a novel technique to suppress the scattering effect in a transillumination image and reconstruct a three-dimensional image of the internal light-absorbing structure of animal body from two-dimensional images. The problem of the depth-dependence of PSF was solved by the calculation of the projection image in the filtered back-projection method. The feasibility and the effectiveness of the proposed technique were verified in the experiments with tissue-equivalent phantom and a living mouse. Using the proposed technique, the high-absorption organs such as kidneys and the bottom parts of the liver were reconstructed in a 3D image of mouse abdomen.
  • Seki D, Namita T, Kato Y, Shimizu K  20th Symposium of the International Society on Biotelemetry Proceedings  29  -31  2014/05  
    19–22 May 2022 Kyoto, JapanFundamental study was conducted to apply the optical biotelemetry technique to the body area network (BAN). With this technique, we can expect many advantages over the conventional BAN with electric signal transmission. The bandwidth was evaluated to be 2.80 GHz. The optical signal reached the longer distance in the narrower channel due to the light-guide effect in diffuser. For a prototype of a practical system, an array of LEDs was attached to the wrist area and transmitted light was detected with an avalanche photodiode. The signal transmission (100 kHz, ASK) from the wrist to the fingertips was attained in an adult hand. In the experiment, the following facts were newly found. When the transmission range in the hand exceeds 70 mm, the intensity of radiation from the hand surface became larger than that of the internal propagation through the hand tissue. The transmission range became larger with the lower duty ratio of the optical ASK signal. These results provide useful information for the realization of the optical BAN as an application of optical biotelemetry.
  • YAMAMOTO KOHEI, TRAN TRUNG NGHIA, NAMITA TAKESHI, KATO YUJI, SHIMIZU KOICHI  電子情報通信学会技術研究報告  113-  (499(MBE2013 115-148))  115  -120  2014/03/17  [Not refereed][Not invited]
     
    To improve near-infrared transillumination images of biological tissue, a new scattering suppression technique was developed. It enables us to apply the point spread function (PSF) derived for light source to the transillumination image of an absorbing structure. The feasibility of the proposed technique was verified in experiment with tissue-equivalent phantom and biological tissue. If we know the depth of the absorber, we can effectively suppress the scattering effect in the image. To apply this technique to an unknown absorber in turbid medium, we also developed the depth estimation technique for the absorbing structure. The effectiveness of the proposed technique was verified in experiments.
  • OGAWA Daiki, NAMITA Takeshi, KATO Yuji, SHIMIZU Koichi  IEICE technical report. ME and bio cybernetics  113-  (499)  121  -126  2014/03/10  [Not refereed][Not invited]
     
    To improve the transcutaneous fluorescent image of an animal body, we derived a point-spread function (PSF) at a cylindrical surface of a diffuse scattering medium. In this technique, distortion problem of the restored shape was remained. To solve this problem, a new technique was developed. In this technique, the asymmetric 2 dimensional PSF was divided into parts, or the symmetric and asymmetric parts. The feasibility of the proposed technique was verified in the simulation and experiments. The applicability to the biological tissue was also verified.
  • Natsume Yuya, Namita Takeshi, Kato Yuji, Kitama Masataka, Shimizu Koichi  IEICE technical report. ME and bio cybernetics  113-  (499)  127  -131  2014/03/10  [Not refereed][Not invited]
     
    For optical observation of arteriovenous fistula in dialysis treatment, we have developed a transmission image improvement technique using the measured point spread function (PSF) of implanted fluorescent source inside the body. In the experimental study of model phantom, the effectiveness of the proposed technique was confirmed. Then, it was applied to the biological tissue, and its usefulness in practice was verified.
  • OBA Kazuhiro, YOKOYAMA Naoya, NAMITA Takeshi, KATO Yuji, SHIMIZU Koichi  IEICE technical report. ME and bio cybernetics  113-  (499)  109  -114  2014/03  [Not refereed][Not invited]
     
    We have developed a technique to estimate the spatial distribution of the absorption coefficient (μ_a) of turbid medium by the time-resolved measurement of backscattered light, and verified its feasibility in simulation and experiments. For accurate estimation of the μ_a distribution, accurate scattering property of the medium is essential. Here, we newly developed a technique to estimate the accurate scattering coefficient (μ_s) by reducing the effect of the absorption heterogeneity. To estimate the μ_a more accurately, we also devised a new technique in which we attach a diffuser plate with known μ_s at the body surface. The feasibility and the usefulness of these techniques were verified in the Monte Carlo simulation.
  • Tran Trung Nghia, Yamamoto Kohei, Namita Takeshi, Kato Yuji, Shimizu Koichi  BIOMEDICAL APPLICATIONS OF LIGHT SCATTERING VIII  8952-  2014  [Refereed][Not invited]
     
    To realize three-dimensional (3D) optical imaging of the internal structure of animal body, we have developed a new technique to reconstruct CT images from two-dimensional (2D) transillumination images. In transillumination imaging, the image is blurred due to the strong scattering in the tissue. We had developed a scattering suppression technique using the point spread function (PSF) for a fluorescent light source in the body. In this study, we have newly proposed a technique to apply this PSF for a light source to the image of unknown light-absorbing structure. The effectiveness of the proposed technique was examined in the experiments with a model phantom and a mouse. In the phantom experiment, the absorbers were placed in the tissue-equivalent medium to simulate the light-absorbing organs in mouse body. Nearinfrared light was illuminated from one side of the phantom and the image was recorded with CMOS camera from another side. Using the proposed techniques, the scattering effect was efficiently suppressed and the absorbing structure can be visualized in the 2D transillumination image. Using the 2D images obtained in many different orientations, we could reconstruct the 3D image. In the mouse experiment, an anesthetized mouse was held in an acrylic cylindrical holder. We can visualize the internal organs such as kidneys through mouse's abdomen using the proposed technique. The 3D image of the kidneys and a part of the liver were reconstructed. Through these experimental studies, the feasibility of practical 3D imaging of the internal light-absorbing structure of a small animal was verified.
  • 小川大貴, 浪田健, 加藤祐次, 清水孝一  Optics & Photonics Japan講演予稿集(CD-ROM)  2013-  ROMBUNNO.14AD8  2013/11  [Not refereed][Not invited]
  • 大場一寛, 横山直弥, 浪田健, 加藤祐次, 清水孝一  Optics & Photonics Japan講演予稿集(CD-ROM)  2013-  ROMBUNNO.14AD9  2013/11  [Not refereed][Not invited]
  • 夏目裕也, 浪田健, 加藤祐次, 北間正崇, 清水孝一  Optics & Photonics Japan講演予稿集(CD-ROM)  2013-  ROMBUNNO.12AA2  2013/11  [Not refereed][Not invited]
  • 山本航平, 田中宏幸, NGHIA Tran Trung, 浪田健, 加藤祐次, 清水孝一  Optics & Photonics Japan講演予稿集(CD-ROM)  2013-  ROMBUNNO.14PD1  2013/11  [Not refereed][Not invited]
  • Seki Daisuke, Namita Takeshi, Kato Yuji, Shimizu Koichi  Proceedings of the Society Conference of IEICE  2013-  (2)  "S  -147"-"S-148"  2013/09  [Not refereed][Not invited]
  • AKIYAMA JUNKICHI, NAMITA TAKESHI, KATO YUJI, SHIMIZU KOICHI  電子情報通信学会技術研究報告  112-  (479(MBE2012 88-129))  179  -184  2013/03/13  [Not refereed][Not invited]
     
    To realize practical optical communication through human body, an experimental study was conducted on the near-infrared light propagation through model phantoms and a human hand. In a backscattering configuration, the optical data transmission over 200 mm distance was possible. Using a practically compact equipment, the optical data transmission from the wrist to fingertips was attained. It was found that the light attenuation was lower along a narrow diffusing object than the object with large scattering volume. These results suggested the feasibility of the optical communication through a human palm.
  • OBATA KYOHEI, NAMITA TAKESHI, KATO YUJI, SHIMIZU KOICHI  電子情報通信学会技術研究報告  112-  (479(MBE2012 88-129))  133  -138  2013/03/13  [Not refereed][Not invited]
     
    A technique was newly developed to estimate the thickness of a fluorescent object in a turbid medium, such as an animal body. In this technique. we estimate the thickness from the different in the fluorescent intensity caused by the difference in the absorption of excitation light between two wavelengths. We analyzed the relation between the thickness of a fluorescent object and the intensity ratio of the fluorescent light, and confirmed the validity of this principle. Using this principle, we attempted to estimate the thickness and the depth of a fluorescent object simultaneously. We found that we can make better estimation for both parameters by estimating the depth first. In an experiment, we estimated the depth and the thickness of the fluorescent object in a tissue equivalent phantom. With the depth. we obtained a point spread function for image restoration. Using the restored image and the estimated depth, we could construct three dimensional image of a fluorescent object in a turbid medium.
  • OKUYAMA Yuki, NAMITA Takeshi, KATO Yuji, SHIMIZU Koichi  IEICE technical report. ME and bio cybernetics  112-  (479)  121  -126  2013/03/06  [Not refereed][Not invited]
     
    To realize the practical transillumination imaging with beam-wave incidence. we had derived the equation of beam-wave propagation in a turbid medium theoretically, and formulated the procedure of image processing. The validity and effectiveness of the proposed technique was verified in experiment. The effectiveness of our technique to correct the deviation of the blurred image caused by the inhomogeneity of the incident light and the applicability of the proposed technique to the biological tissue was also examined.
  • XIA Jiao, NAMITA Takeshi, Kato Yuji, Shimizu Koichi  IEICE technical report. ME and bio cybernetics  112-  (479)  127  -132  2013/03/06  [Not refereed][Not invited]
     
    To obtain a clear image in transcutaneous fluorescent imaging, we have newly developed a technique to simultaneously estimate the depth and optical coefficients which have to be known a priori to improve fluorescent images. The feasibility of the proposed technique was verified in both numerical analysis and experiment. It was demonstrated that we could restore the blurred fluorescent images well with a point spread function (PSF), which is dependent on the estimated depth and optical coefficients. Finally, the applicability of the proposed technique to the biological body was verified in the experiment with a biological sample tissue.
  • MORIMOTO Takuro, NAMITA Takeshi, KATO Yuji, SHIMIZU Koichi  IEICE technical report. ME and bio cybernetics  112-  (479)  139  -144  2013/03/06  [Not refereed][Not invited]
     
    To realize the tissue oxygen saturation imaging by time-resolved measurement of backscattered light, appropriate wavelengths have been chosen from the absorption spectrum of hemoglobin. For the precise estimation in the medium with spatially inhomogeneous scattering coefficient (μs),a new technique was developed to estimate the tissue oxygen saturation using the Us estimation technique in the same measurement scheme. The effectiveness of the proposed technique was verified in the simulation with the layer model that simulates spatially inhomogeneous scattering and absorption coefficients.
  • YOKOTA Shun, NAMITA Takeshi, KATO Yuji, SHIMIZU Koichi  IEICE technical report. ME and bio cybernetics  112-  (479)  173  -177  2013/03/06  [Not refereed][Not invited]
     
    The absorption at a specific position inside a turbid medium can be measured by back-propagating the scattered light using phase conjugate light and focused ultrasonic modulation. With the view toward clear imaging through turbid medium, we constructed an experimental system to make the back-propagation of scattered light possible using phase conjugate light. We confirmed the fundamental performance for the extraction of a localized area in turbid medium. In experiment, we attempted to restore the incident light from the scattered light by back-propagating the scattering process using phase conjugate light.
  • Matsuura Taiki, Namita Takeshi, Kato Yuji, Shimizu Koichi  IEICE technical report. ME and bio cybernetics  112-  (479)  167  -172  2013/03  [Not refereed][Not invited]
     
    For the 3D non-invasive imaging of shallow regions of a human body, we have developed a new technique to reconstruct the absorbing structure from optical transillumination images obtained in limited view angle. The effectiveness of the proposed technique was verified in the experiment using the model phantom that simulates the veins in the human forearm. Further, we extended the technique so that we can apply it to the turbid medium with unknown internal structure and the usefulness was verified. The applicability of the proposed technique to the biological tissue was also examined.
  • Shimizu, K., Namita, T., Kato, Y.  Lecture Notes of the Institute for Computer Sciences, Social-Informatics and Telecommunications Engineering, LNICST  61-  173  -178  2013  [Refereed][Not invited]
     
    For a new optical body area network (BAN) technique, a fundamental study was conducted of optical data transmission through a human body using diffusely scattered light. The frequency bandwidth for data transmission was restricted by the effect of strong scattering inside body tissues. In experiments using human bodies, the possibility of the transmission up to 100 MHz was confirmed. Using the linear equalization process, we can transmit an 800 MHz square wave signal. Data transmission of around 200 mm distance in a human hand was possible. To overcome problems of noise, multipath transmission, and the instantaneous interruption of data transmission, the space diversity (SD) technique was applied to stabilize data communications. The SD technique effectiveness was confirmed through analysis using real optical impulse responses. The feasibility of BAN using diffusely scattered light in the body was verified through these analyses. © Institute for Computer Sciences, Social Informatics and Telecommunications Engineering 2013.
  • Junkichi Akiyama, Daisuke Seki, Takeshi Namita, Yuji Kato, Koichi Shimizu  2013 7TH INTERNATIONAL SYMPOSIUM ON MEDICAL INFORMATION AND COMMUNICATION TECHNOLOGY (ISMICT)  14  -17  2013  [Refereed][Not invited]
     
    To examine the practical potential of an optical body area network (BAN) technique, a feasibility study was conducted of optical data transmission through a human hand using diffusely scattered light. The data transmission of 170 mm distance in a human hand was accomplished to show the possibility of the data transmission from the wrist to the fingertips in an adult hand. The frequency bandwidth for data transmission was restricted by the effect of strong scattering inside body tissues. In experiments using a human hand, the bandwidth was measured to be 2.80 GHz. The feasibility of BAN using diffusely scattered light in the body was verified through these analyses.
  • Kazuhiro Nishida, Takeshi Namita, Yuji Kato, Koichi Shimizu  OPTICAL TOMOGRAPHY AND SPECTROSCOPY OF TISSUE X  8578-  2013  [Refereed][Not invited]
     
    To estimate the depth distribution of the absorption coefficient in a turbid medium, a new nonlinear inversion technique was developed. It can resolve important shortcomings of the nonlinear error of conventional linear inversion techniques. First, a turbid medium is divided into imaginary layers with arbitrary thickness. The spatial pathlength distribution (SPD) is obtained for each layer in the Monte Carlo simulation as a function of source-detector distance. In the integral operation using SPDs, we can obtain the absorption coefficient of each layer, or the depth distribution of absorption. This inversion process is based on the assumption that the light attenuation is linear with respect to the small pathlength of a photon. However, if we consider the variance of pathlength of many photons in each layer, then this assumption produces nonlinear error. We developed a technique to solve this problem in the following three steps. First, the initial values of absorption coefficient of each layer are obtained using a conventional linear inverse matrix assuming that variance of pathlength of many photons does not exist. Then, improved absorption coefficients are obtained with these initial values and the pathlength variance of many photons using the same matrix. In this way, the nonlinear error is corrected. Repeating this process, the improved absorption coefficient approaches a true value. The effectiveness of the proposed technique was confirmed in the Monte Carlo simulation. The effect of measurement noise was analyzed in the simulation.
  • Taiki Matsuura, Takeshi Namita, Yuji Kato, Koichi Shimizu  2013 35TH ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY (EMBC)  1795  -1798  2013  [Refereed][Not invited]
     
    In transillumination imaging of an animal body with near-infrared light, the shallower structure appears clearer. Therefore, we can reconstruct the three dimensional (3D) image of the shallow structure using the transillumination images as the projection images. In the 3D reconstruction, it may be better to use the projection images of limited observation-angle range rather than those from 360 degrees range. We investigated this possibility and devised a new technique to reconstruct the 3D image of the light absorbing structure in shallow region of a turbid medium. This technique is applicable to the turbid object without any a priori knowledge on the angular position of the absorbing structure. The feasibility of the proposed technique was verified in experiments.
  • Tran Trung Nghia, Takeshi Namita, Yuji Kato, Koichi Shimizu  2013 35TH ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY (EMBC)  2644  -2647  2013  [Refereed][Not invited]
     
    In transillumination imaging of an animal body using near-infrared light, the image is blurred due to the strong scattering in the tissue. We have devised the depth-dependent point spread function (PSF) to suppress the scattering effect in fluorescent imaging. In this study, we applied this principle and developed a technique to reconstruct the absorbing structure in turbid medium without using fluorescent material. In experiments, the feasibility and effectiveness of the proposed technique were verified.
  • Jiao Xia, Takeshi Namita, Yuji Kato, Koichi Shimizu  Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS  2648  -2651  2013  [Refereed][Not invited]
     
    The depth of fluorescent source is required to suppress the scattering effect in transcutaneous fluorescent imaging. We have developed a technique to estimate the depth using two light sources. However, with this technique, the reduced scattering coefficient (μs') and the absorption coefficient (μa) of the scattering medium have to be known a priori. To eliminate this requirement, we devised a technique that uses three excitation sources. The feasibility of the proposed technique was verified in both computer simulation and experiment. It was demonstrated that we could estimate the depth of the fluorescent source and improve the fluorescent image even with μs' and μa variation. © 2013 IEEE.
  • 加藤祐次, 浪田健, 清水孝一  電気・情報関係学会北海道支部連合大会講演論文集(CD-ROM)  2012-  ROMBUNNO.134  2012/10  [Not refereed][Not invited]
  • 森本拓朗, 浪田健, 加藤祐次, 清水孝一  生体医工学  50-  (4)  358  2012/08  [Not refereed][Not invited]
  • 西田 浩平, 浪田 健, 加藤 祐次  電子情報通信学会技術研究報告 : 信学技報  111-  (482)  13  -18  2012/03  [Not refereed][Not invited]
  • TOZAWA Eiji, NAMITA Takeshi, KATO Yuji, SHIMIZU Koichi  IEICE technical report. ME and bio cybernetics  111-  (482)  123  -128  2012/03  [Not refereed][Not invited]
     
    To improve the transcutaneous fluorescent image of an animal body, we derived the depth dependent point-spread function (PSF) for the fluorescent object in scattering medium and demonstrated scattering suppression technique using the depth dependent PSF. We have newly developed a technique to reconstruct 3-dimentional image of a fluorescent object using this scattering suppression technique and the common 2-dimentional tomography technique. The validity of the proposed technique was verified in simulation and experiment with model phantom. A PSF at a cylindrical surface of a diffuse scattering medium was also newly developed. The validity of this PSF and the applicability of this PSF to reconstruct the 3-dimensional image were verified in experiments.
  • OTANI Masafumi, NAMITA Takeshi, KATO Yuji, SHIMIZU Koichi  IEICE technical report. ME and bio cybernetics  111-  (482)  1  -6  2012/03  [Not refereed][Not invited]
     
    We have developed a technique to estimate the absorption coefficient (μ_a) of turbid medium by the time-resolved measurement of backscattered light, and verified its feasibility in simulation and experiments. For accurate estimation of the absorption distribution in a diffuse scattering medium, accurate scattering property of the medium is essential. Here, we newly developed a technique to obtain the important parameters required for the absorption estimation by measuring the scattering property of the medium using backscattered light. The results using the proposed technique were compared with those using the former technique in which the scattering property of the medium was assumed to be known and homogeneous. Through these simulations, the feasibility and the effectiveness of the proposed technique were verified.
  • WEI Dingding, NAMITA Takeshi, KATO Yuji, SHIMIZU Koichi  IEICE technical report. ME and bio cybernetics  111-  (482)  7  -12  2012/03  [Not refereed][Not invited]
     
    A dynamic light scattering (DLS) technique has been applied to quantify the amount of the small dense low-density lipoprotein (sdLDL) which is clinically significant for coronary diseases. A technique to obtain the size distribution of LDL particles in the DLS measurement was newly developed. This technique is applicable even to the relatively narrow size-range (20-30 nm) of sdLDL, and vulnerable against the random noise in the autocorrelation function of DLS. The effectiveness of the proposed technique was verified in the computer simulation and in the experiment with latex spheres and LDL particles.
  • TAKAHASHI Hiroki, NAMITA Takeshi, KATO Yuji, SHIMIZU Koichi  IEICE technical report. ME and bio cybernetics  111-  (482)  19  -24  2012/03  [Not refereed][Not invited]
     
    To improve NIR transillumination images of animal body, the application of the point spread function (PSF) derived for fluorescent source inside the body was attempted. Through experimental study, the applicability was demonstrated. In addition, the step-wise deconvolution technique using partial PSF's was newly devised to solve the problem of instability in the deconvolution using the wide PSF for deep seated structure under the skin. In simulation and experiments with a model phantom, the effectiveness of the proposed technique was confirmed. Then, it was applied to the human body, and its usefulness in practice was verified.
  • SUGIYAMA Keita, NAMITA Takeshi, KATO Yuji, SHIMIZU Koichi  IEICE technical report. ME and bio cybernetics  111-  (482)  25  -30  2012/03  [Not refereed][Not invited]
     
    The absorption distribution along the depth direction in a turbid medium can be estimated in the time-resoloved measurement. For accurate estimation of the absorption distribution in scattering medium, a new technique which is applicable even to large inhomogeneity was developed. In this technique, the difference of the propagation path for every photon was considered. The effectiveness of the proposed technique was verified in computer simulation. To examine the applicability of the proposed technique, Monte Carlo simulation was conducted with the model of the human head. Through this analysis, the applicability of the proposed technique to a human body was verified.
  • MATSUDA Yasushi, NAMITA Takeshi, KATO Yuji, SHIMIZU Koichi  IEICE technical report. ME and bio cybernetics  111-  (482)  151  -156  2012/03  [Not refereed][Not invited]
     
    We have shown the possibility of transillumination imaging of the arteries in the adult forearm as well as the veins. Using the change of absorption spectra of blood hemoglobin, we can expect to discriminate the arteries from the veins in the transillumination images. First, the validity of the proposed principle was confirmed in the measurement of the contrast change with the wavelength of light. We have developed a practical technique to visualize blood vessels with arteriovenous discrimination. The proposed technique was applied to the subjects with different ages and gender. The feasibility of transcutaneous imaging with arteriovenous discrimination was verified in experiments.
  • 秋山潤吉, 浪田健, 加藤祐次, 清水孝一  日本生体医工学会大会プログラム・論文集(CD-ROM)  51st-  2012
  • 松浦太紀, 浪田健, 加藤祐次, 清水孝一  日本生体医工学会大会プログラム・論文集(CD-ROM)  51st-  ROMBUNNO.O3-09-2  2012  [Not refereed][Not invited]
  • 杉山慶多, 浪田健, 加藤祐次, 清水孝一  日本生体医工学会大会プログラム・論文集(CD-ROM)  51st-  ROMBUNNO.O3-10-3  2012  [Not refereed][Not invited]
  • 小幡恭平, 浪田健, 加藤祐次, 清水孝一  日本生体医工学会大会プログラム・論文集(CD-ROM)  51st-  ROMBUNNO.O3-10-5  2012  [Not refereed][Not invited]
  • 小幡恭平, 浪田健, 加藤祐次, 清水孝一  Optics & Photonics Japan講演予稿集(CD-ROM)  2012-  ROMBUNNO.24PA9  2012  [Not refereed][Not invited]
  • 奥山雄基, 浪田健, 加藤祐次, 清水孝一  日本生体医工学会大会プログラム・論文集(CD-ROM)  51st-  ROMBUNNO.O3-09-4  2012  [Not refereed][Not invited]
  • 松田康志, 浪田健, 加藤祐次, 清水孝一  日本生体医工学会大会プログラム・論文集(CD-ROM)  51st-  ROMBUNNO.O3-10-1  2012  [Not refereed][Not invited]
  • 高橋博樹, 浪田健, 加藤祐次, 清水孝一  日本生体医工学会大会プログラム・論文集(CD-ROM)  51st-  ROMBUNNO.O3-09-3  2012  [Not refereed][Not invited]
  • 奥山雄基, 浪田健, 加藤祐次, 清水孝一  Optics & Photonics Japan講演予稿集(CD-ROM)  2012-  ROMBUNNO.24PA12  2012  [Not refereed][Not invited]
  • 森本拓朗, 浪田健, 大場一寛, 加藤祐次, 清水孝一  Optics & Photonics Japan講演予稿集(CD-ROM)  2012-  ROMBUNNO.24PA14  2012  [Not refereed][Not invited]
  • NGHIA Tran Trung, YAMAMOTO Kohei, NAMITA Takeshi, KATO Yuji, SHIMIZU Koichi  Optics & Photonics Japan講演予稿集(CD-ROM)  2012-  ROMBUNNO.23PA6  2012  [Not refereed][Not invited]
  • WEI Dingding, NAMITA Takeshi, KATO Yuji, SHIMIZU Koichi  日本生体医工学会大会プログラム・論文集(CD-ROM)  51st-  ROMBUNNO.O3-10-2  2012  [Not refereed][Not invited]
  • TOBISAWA Naoya, NAMITA Takeshi, KATO Yuji, SHIMIZU Koichi  IEICE technical report. ME and bio cybernetics  110-  (460)  147  -152  2011/02  [Not refereed][Not invited]
     
    To assist vascular injection, we have developed a simultaneous observation system using a body surface image and a transillumination image of blood vessels. Light source was devised to make homogeneous, wide-area and low-leak illumination possible. Using the developed system, we could obtain the transillumination images in all part of the adult forearm with as much as 67 mm thickness. In addition to the superficial veins, we could visualize the arteries in the forearm. Its usefulness was examined in the simulation of injection with a phantom of the human forearm.
  • SHIMANO Moto, NAMITA Takeshi, KATO Yuji, SHIMIZU Koichi  IEICE technical report. ME and bio cybernetics  110-  (460)  153  -158  2011/02  [Not refereed][Not invited]
     
    To see through a turbid medium, a technique was developed to reconstruct a three-dimensional structure inside the medium. Clear transillumination images were obtained with a scattering suppression technique in which the weakly scattered light component can be extracted from the strongly diffused light. The possibility of the proposed technique was examined in the experiment using the turbid medium with known internal structure. Through the experimental analysis, the feasibility of the proposed technique and the effectiveness of the scattering suppression were verified.
  • Takeshi Namita, Masayuki Kawashima, Yuji Kato, Koichi Shiniizu  2011 Int. Quantum Electron. Conf., IQEC 2011 and Conf. Lasers and Electro-Optics, CLEO Pacific Rim 2011 Incorporating the Australasian Conf. Optics, Lasers and Spectroscopy and the Australian Conf.  1696  -1698  2011  [Not refereed][Not invited]
     
    The effect of absorption inhomogeneity on μ s estimation of a scattering medium with a newly proposed technique was investigated. The estimation error was significantly reduced from that with a conventional technique. © 2011 IEEE.
  • 高橋博樹, 浪田健, 加藤祐次, 清水孝一  日本生体医工学会大会プログラム・論文集(CD-ROM)  50th-  2011
  • 高橋博樹, 浪田健, 加藤祐次, 清水孝一  Optics & Photonics Japan講演予稿集(CD-ROM)  2011-  ROMBUNNO.29PD12  2011  [Not refereed][Not invited]
  • XIA Jiao, 浪田健, 加藤祐次, 清水孝一  Optics & Photonics Japan講演予稿集(CD-ROM)  2011-  ROMBUNNO.29PD11  2011  [Not refereed][Not invited]
  • 大谷真史, 浪田健, 加藤祐次, 清水孝一  Optics & Photonics Japan講演予稿集(CD-ROM)  2011-  ROMBUNNO.29PD3  2011  [Not refereed][Not invited]
  • 西田和弘, 浪田健, 加藤祐次, 清水孝一  Optics & Photonics Japan講演予稿集(CD-ROM)  2011-  ROMBUNNO.29AD4  2011  [Not refereed][Not invited]
  • 西田浩平, 浪田健, 加藤祐次, 清水孝一  Optics & Photonics Japan講演予稿集(CD-ROM)  2011-  ROMBUNNO.30AF7  2011  [Not refereed][Not invited]
  • 松田康志, 飛澤直哉, 浪田健, 加藤祐次, 清水孝一  Optics & Photonics Japan講演予稿集(CD-ROM)  2011-  ROMBUNNO.29PD9  2011  [Not refereed][Not invited]
  • 戸澤英二, 浪田健, 加藤祐次, 清水孝一  日本生体医工学会大会プログラム・論文集(CD-ROM)  50th-  ROMBUNNO.O3-6-6  2011  [Not refereed][Not invited]
  • 嶋野心, 浪田健, 加藤祐次, 清水孝一  日本生体医工学会大会プログラム・論文集(CD-ROM)  50th-  ROMBUNNO.O3-6-4  2011  [Not refereed][Not invited]
  • 飛澤直哉, 松田康志, 浪田健, 加藤祐次, 清水孝一  日本生体医工学会大会プログラム・論文集(CD-ROM)  50th-  ROMBUNNO.O3-6-5  2011  [Not refereed][Not invited]
  • 西田浩平, 浪田健, 加藤祐次, 清水孝一  日本生体医工学会大会プログラム・論文集(CD-ROM)  50th-  ROMBUNNO.O3-7-3  2011  [Not refereed][Not invited]
  • XIA Jiao, 浪田健, 加藤祐次, 清水孝一  日本生体医工学会大会プログラム・論文集(CD-ROM)  50th-  ROMBUNNO.O3-7-2  2011  [Not refereed][Not invited]
  • 嶋野心, 浪田健, 加藤祐次, 清水孝一  Optics & Photonics Japan講演予稿集  2010-  324  -325  2010/11  [Not refereed][Not invited]
  • 飛澤直哉, 浪田健, 加藤祐次, 清水孝一  Optics & Photonics Japan講演予稿集  2010-  326  -327  2010/11  [Not refereed][Not invited]
  • KAKINUMA Hiroyuki, KATO Yuji, SHIMIZU Koichi  IEICE technical report. ME and bio cybernetics  109-  (460)  95  -100  2010/03/02  [Not refereed][Not invited]
     
    To realize a technique applicable to thicker body, the effectiveness of a transillumination imaging using weakly diffused light was examined in experiments. The possibility to extract the weakly diffused component from strongly diffused light was clarified in spatial and temporal analyses. Apparent improvement of transillumination images was demonstrated with a model phantom and a biological specimen. A technique to estimate the depth of an absorber in disuse medium was newly developed. The stability of the depth estimation technique and its applicability to animal tissue were verified in e...
  • KAKITA Shun, KATO Yuji, SHIMIZU Koichi  IEICE technical report. ME and bio cybernetics  109-  (460)  101  -106  2010/03/02  [Not refereed][Not invited]
     
    To realize new optical communication through a human body, the feasibility of data transmission using diffusely scattered light in a human body was examined. Transmissible range of optical data in the human maniphalanx was measured. The data transmission through about 100 mm distance was possible with our experimental system. To overcome the problems of the noises, multipath transmission, and the cut of transmission paths, the space diversity (SD) method was applied to stabilize the data communication. In simulation, the effectiveness of the SD method was confirmed. For the SD method, diffe...
  • SHIMIZU Atsushi, KATO Yuji, SHIMIZU Koichi  IEICE technical report. ME and bio cybernetics  109-  (460)  133  -138  2010/03/02  [Not refereed][Not invited]
     
    Transcutaneous fluorescent images are deteriorated due to the optical scattering of body tissues. Using a depth-depending PSF(point spread function), this effect can be suppressed effectively. We have newly developed a technique to estimate the depth of a fluorescent object in a scattering medium with two light sources. The effectiveness of this technique was confirmed in the experiment with a simple fluorescent object in a scattering medium. Then the proposed technique was improved so as to be applicable to the case of multiple fluorescent objects at different depths. Using model phantoms ...
  • TAKESHITA Yusuke, KATO Yuji, DATE Hiroyuki, SHIMIZU Koichi  IEICE technical report. ME and bio cybernetics  109-  (460)  139  -143  2010/03/02  [Not refereed][Not invited]
     
    A new technique was developed to realize the fluorescence angiography based on the image restoration with point-spread function (PSF). In this technique, the PSF can be obtained using a fluorescence-marked stent placed in a blood vessel. A clear image of the blood vessel can be restored by deconvolving the blurred transcutaneous image with measured PSF. In simulation, the feasibility of the basic idea was confirmed. In the experiments with tissue phantoms, the effectiveness of the proposed technique was verified. Those results suggest the feasibility of the repetitive examination of vessel ...
  • YOSHIMURA Hitoshi, NAMITA Takeshi, KATO Yuji, SHIMIZU Koichi  IEICE technical report. ME and bio cybernetics  109-  (460)  89  -94  2010/03  [Not refereed][Not invited]
     
    To realize functional imaging by time-resolved measurement of backscattered light, a technique has been developed to estimate the spatial distribution of tissue oxygen saturation. In theoretical analysis on the estimation error, the measurement conditions to suppress the error were clarified. The effectiveness of the proposed technique was verified in the Monte Carlo simulation with the three-layer model that simulates the hemoglobin concentrations of the cerebral gray matter and the thigh muscle. The noise tolerance of the proposed technique in solving an inverse problem was evaluated. In ...
  • CHIKAHISA Tomoya, NAMITA Takeshi, KATO Yuji, SHIMIZU Koichi  IEICE technical report  109-  (460)  127  -132  2010/03  [Not refereed][Not invited]
     
    The possibility of new biological measurement by time resolved analysis of the optical backscattering enhancement was pursued. Through simulation analysis for various optical parameter changes, the extinction time of the enhancement peak was selected as an index to evaluate the scattering property of the turbid medium such as an animal tissue. The effectiveness of this index was verified in experiments. The range of measurable depth in a scattering medium was analyzed. The results with our experimental system suggested that we can measure the scattering coefficient up to 5 mm depth from the surface of the biological body. The feasibility of imaging the spatial distribution of a scattering coefficient using the extinction time of the enhancement peak was verified in experiments.
  • SHIMIZU Koichi, NAMITA Takeshi, KATO Yuji  電気学会研究会資料. IM, 計測研究会  2010-  (1)  33  -38  2010/02  [Not refereed][Not invited]
  • CHIKAHISA Tomoya, NAMITA Takeshi, KATO Yuji, SHIMIZU Koichi  日本生体医工学会大会プログラム・論文集(CD-ROM)  49th-  2010
  • KAWASHIMA Masayuki, NAMITA Takeshi, OTANI Masafumi, KATO Yuji, SHIMIZU Koichi  日本生体医工学会大会プログラム・論文集(CD-ROM)  49th-  2010
  • YOSHIMURA Hitoshi, NAMITA Takeshi, KATO Yuji, SHIMIZU Koichi  日本生体医工学会大会プログラム・論文集(CD-ROM)  49th-  2010
  • TRIRONGJITMOAH Suchin, SAKURAI Toshihiro, NISHIBATA Yuka, NAMITA Takeshi, KATO Yuji, IINAGA Kazuya, CHIBA Hitoshi, SHIMIZU Koichi  日本生体医工学会大会プログラム・論文集(CD-ROM)  49th-  ROMBUNNO.PS3-5-1  2010  [Not refereed][Not invited]
  • KAWASHIMA Masayuki, NAMITA Takeshi, KATO Yuji, SHIMIZU Koichi  IEICE technical report  109-  (406)  97  -102  2010/01  [Not refereed][Not invited]
     
    We developed a technique to estimate the reduced scattering coefficient (μ_s') of turbid medium by the time-resolved measurement of backscattered light, and verified its feasibility in simulation. Here, we examined the accuracy and the characteristics of the proposed technique in experiments. The estimated values agreed well with those measured by a conventional technique and with those reported by references. The effect of absorption inhomogeneity on μ_s' estimation was investigated. The term that represents the estimation error was successfully separated in the equation of μ_s' estimation. In an experimental analysis, it was confirmed that the proposed technique is less affected by the μ_a-inhomogeneity and more practical than conventional techniques.
  • TAKESHITA YUSUKE, KATO YUJI, DATE HIROYUKI, SHIMIZU KOICHI  Optics & Photonics Japan講演予稿集  2009-  52-53  2009/11/24  [Not refereed][Not invited]
  • SHIMIZU ATSUSHI, KATO YUJI, SHIMIZU KOICHI  Optics & Photonics Japan講演予稿集  2009-  54-55  2009/11/24  [Not refereed][Not invited]
  • KAKINUMA HIROYUKI, TAKAGI KAZUTO, KATO YUJI, SHIMIZU KOICHI  Optics & Photonics Japan講演予稿集  2009-  48-49  2009/11/24  [Not refereed][Not invited]
  • TRIRONGJITMOAH Suchin, SAKURAI Toshihiro, NISHIBATA Yuka, NAMITA Takeshi, KATO Yuji, IINAGA Kazuya, CHIBA Hitoshi, SHIMIZU Koichi  Optics & Photonics Japan講演予稿集  2009-  64  -65  2009/11  [Not refereed][Not invited]
  • NAMITA TAKESHI, OTANI MASAFUMI, KAWASHIMA MASAYUKI, KATO YUJI, SHIMIZU KOICHI  Optics & Photonics Japan講演予稿集  2009-  62  -63  2009/11  [Not refereed][Not invited]
  • KAWASHIMA MASAYUKI, NAMITA TAKESHI, KATO YUJI, SHIMIZU KOICHI  Optics & Photonics Japan講演予稿集  2009-  50  -51  2009/11  [Not refereed][Not invited]
  • トライロンジットモア・スチン, 櫻井 俊宏, 西端 友香, 浪田 健, 加藤 祐次, 飯永 一也, 千葉 仁志, 清水 孝一  電子情報通信学会技術研究報告(MEとバイオサイバネティックス)  109-  (106)  23  -28  2009/06  
    LDL(low density lipoprotein)の中でも、小型で比重の大きいsdLDL(small dense LDL)は、心疾患との高い相関から、臨床検査における重要性が指摘されている。従来法は煩雑で長時間を要する。このsdLDLの定量評価をめざし、動的光散乱(DLS:dynamic light scattering)の応用を考えた。DLS測定により得られる平均粒径や相関関数を用いてLDL中のsdLDL量の割合を求める手法を3種新たに考案した。sdLDLの割合を直接求める数式解を導出した。粒径の異なるラテックス標準粒子および実際のLDLを用いた実測により、提案手法の有効性を実証した。(著者抄録)
  • TRIRONGJITMOAH Suchin, SAKURAI Toshihiro, NISHIBATA Yuka, NAMITA Takeshi, KATO Yuji, IINAGA Kazuya, CHIBA Hitoshi, SHIMIZU Koichi  電気学会研究会資料. MBE, 医用・生体工学研究会  2009-  (71)  23  -28  2009/06  [Not refereed][Not invited]
  • トライロンジットモア スチン, 浪田健, 西端友香, 櫻井俊宏, 加藤祐次, 飯永一也, 千葉仁志, 清水孝一  生体医工学  47-  (3)  321  -321  2009/06  [Not refereed][Not invited]
  • TANAKA YOSHINORI, KITAMA MASATAKA, ARISAWA JUNJI, TAKAGI KAZUTO, KATO YUJI, SHIMIZU KOICHI  北海道工業大学研究紀要  (37)  271  -277  2009/03/24  [Not refereed][Not invited]
  • NEMOTO Tomoyuki, KATO Yuji, SHIMIZU Koichi  IEICE technical report. ME and bio cybernetics  108-  (479)  133  -137  2009/03/04  [Not refereed][Not invited]
     
    For the measurement of the functional information in a biological body such as the oxygenation of the blood in the blood vessel in vivo, a technique was developed to measure scattering and absorption characteristic of flowing scattering medium by Doppler OCT principle. The intensity of the Doppler signal caused by the blood flow is measured in the spatially resolved measurement of OCT. We can estimate the optical characteristics of the blood from the attenuation of this signal with the distance in the depth direction. The concentration of an absorbing component in the blood can be also esti...
  • AMAI Kenji, TAKAGI Kazuto, KATO Yuji, AMANO Kazuhiko, SHIMIZU Koichi  IEICE technical report. ME and bio cybernetics  108-  (479)  127  -132  2009/03/04  [Not refereed][Not invited]
     
    To realize next-generation actionless personal authentication, fundamental study was conducted to develop a wearable sensor for vein authentication. A transillumination image of blood vessels was obtained in a circular light source of epi-illumination. The major inhomogeneity over the total view area could be compensated by the attenuation filter designed from the diffusion theory. The effect of discrete light sources and the image processing for local inhomogeneity were investigated. Through this study, we could obtain the transillumination image of sufficient quality for vein authentication.
  • SHIDA Genki, KATO Yuji, SHIMIZU Koichi  IEICE technical report. ME and bio cybernetics  108-  (479)  89  -93  2009/03/04  [Not refereed][Not invited]
     
    A new technique was developed to obtain the CT image for the fluorescent material in a biological body. Fluorescent images blurred by scattering are obtained at the body surface from all the circumferential directions. Deblurred images are restored using the depth-dependant point spread function. A CT image can be reconstructed using the deblurred images by the filtered back projection method. The feasibility and the effectiveness of the proposed technique were verified in the simulation and the experiments with a model phantom and a biological sample.
  • TANAKA Yoshinori, KITAMA Masataka, ARISAWA Junji, TAKAGI Kazuto, KATO Yuji, SHIMIZU Koichi  IEICE technical report  2009-  (1)  27  -32  2009/01/23  [Not refereed][Not invited]
     
    A fundamental study was conducted on the tomographic imaging using near-axis scattered light for small experimental animals. We velified the feasibility of CT imaging by extracting the near-axis scattered light using the optical difference principle. We showed that the quantitative CT imaging of absorption distribution is possible. The spatial resolution of CT images obtained with our experimental system was evaluated as about 1mm.
  • TRIRONGJITMOAH Suchin, NAMITA Takeshi, SAKURAI Toshihiro, KATO Yuji, IINAGA Kazuya, CHIBA Hitoshi, SHIMIZU Koichi  日本生体医工学会大会プログラム・論文集(CD-ROM)  48th-  2009
  • 近久智哉, 浪田健, 加藤祐次, 清水孝一  日本生体医工学会大会プログラム・論文集(CD-ROM)  48th-  ROMBUNNO.23AMP1-1-7  2009  [Not refereed][Not invited]
  • 浪田健, 川島雅之, 加藤祐次, 清水孝一  日本生体医工学会大会プログラム・論文集(CD-ROM)  48th-  ROMBUNNO.23AMP1-1-6  2009  [Not refereed][Not invited]
  • 清水孝一, 金澤瑠維, 川島雅之, 浪田健, 加藤祐次  電気学会基礎・材料・共通部門大会講演論文集(CD-ROM)  2008-  ROMBUNNO.XIX-3  2008/08  [Not refereed][Not invited]
  • Goto Yasuo, Kato Yuji, Shimizu Koichi  IEICE technical report. ME and bio cybernetics  107-  (541)  49  -52  2008/03/06  [Not refereed][Not invited]
     
    To realize a simple depth-selective imaging of diffuse medium, a new technique was developed that uses multiple circular light sources, an imaging device, and image subtraction process. If the position of a light source on the body surface changes, the propagation region of scattered light in the body becomes different. The proposed technique detects this difference by image subtraction. In the simulation based on the diffusion theory, the effectiveness of the technique was confirmed. Using a model phantom, the applicability of the technique to mammalian tissue was verified. The possibility...
  • SAITO Toshihide, KAKITA Shun, KATO Yuji, SHIMIZU Koichi  IEICE technical report. ME and bio cybernetics  107-  (541)  57  -60  2008/03/06  [Not refereed][Not invited]
     
    For advanced data communication from implanted device, a fundamental study was conducted on the information transmission inside a biological body using light. To examine the effect of strong optical scattering inside the body, the frequency bandwidth for data transmission was evaluated. In the experiment using meat, the possibility of the transmission up to 100MHz was confirmed. To expand the bandwidth, various signal processing techniques were compared. With the linear equalizing process, we can transmit an 800MHz square wave signal. It was confirmed that 900Mcps transmission becomes possi...
  • KUBO Yoshihiro, NAMITA Takeshi, KATO Yuji, SHIMIZU Koichi  IEICE technical report. ME and bio cybernetics  107-  (541)  53  -56  2008/03  [Not refereed][Not invited]
     
    The backscattering enhancement has been studied with continuous light. We attempted the time-resolved analysis for this phenomenon. It was newly found that the width of the backscattering enhancement peak becomes narrower as time goes in the rising time of the time-resolved backscattering pulse from diffuse scattering medium. In the falling time of the backscattering pulse, the backscattering enhancement peak disappears as the time goes. We can evaluate the multiple-scattering characteristics of a sample by measuring the extinction time of the peak. Using latex beads and the Intralipid susp...
  • 浪田健, 金澤瑠維, 川島雅之, 加藤祐次, 清水孝一  日本生体医工学会大会プログラム・論文集(CD-ROM)  47th-  2008
  • 川島雅之, 金澤瑠維, 浪田健, 加藤祐次, 清水孝一  日本生体医工学会大会プログラム・論文集(CD-ROM)  47th-  2008
  • TRIRONGJITMOAH Suchin, NAMITA Takeshi, KATO Yuji, IINAGA Kazuya, CHIBA Hitoshi, SHIMIZU Koichi  Optics & Photonics Japan講演予稿集  2008-  2008
  • TRIRONGJITMOAH Suchin, NAMITA Takeshi, SAKURAI Toshihiro, KATO Yuji, IINAGA Kazuya, CHIBA Hitoshi, SHIMIZU Koichi  日本生体医工学会大会プログラム・論文集(CD-ROM)  47th-  2008
  • 浪田健, 川島雅之, 加藤祐次, 清水孝一  Optics & Photonics Japan講演予稿集  2008-  2008
  • 川島雅之, 浪田健, 加藤祐次, 清水孝一  Optics & Photonics Japan講演予稿集  2008-  2008
  • KANAZAWA Rui, NAMITA Takeshi, KATO Yuji, SHIMIZU Koichi  IEICE technical report  107-  (460)  29  -32  2008/01  [Not refereed][Not invited]
     
    A technique was developed to estimate the scattering coefficient of diffuse medium such as a biological body by the time-resolved measurement of backscattered light. The effectiveness of the technique was confirmed in the Monte Carlo simulation. In the analysis of measurement noise, appropriate conditions of the measurement were obtained. The effect of the inhomogeneity of the absorption coefficient was investigated. The possibility to suppress the effect was demonstrated. In the case of an inhomogeneous scattering coefficient, the meaning of the time-dependent estimated value was clarified.
  • NAMITA Takeshi, KANAZAWA Rui, KATO Yuji, SHIMIZU Koichi  電気学会研究会資料. MBE, 医用・生体工学研究会  2007-  (36)  9  -12  2007/06  [Not refereed][Not invited]
  • BETTOYASHIKI Genta, TAKAGI Kazuto, KATO Yuji, SHIMIZU Koichi  IEICE technical report. ME and bio cybernetics  106-  (592)  25  -28  2007/03/09  [Not refereed][Not invited]
     
    For transillumination imaging of biological body, the previously proposed technique was improved to extract near-axis scattered light efficiently. In experiments, it was verified that extraction efficiency can be improved about 10dB using the newly proposed technique. It was confirmed that the propagation area of scattered light can be largely restricted to the near-axis region. In the measurement of absorption distribution in scatterers, the possibility of accurate absorption measurement with good spatial resolution was demonstrated.
  • Endo Tomoki, Kato Yuji, Shimizu Koichi  IEICE technical report. ME and bio cybernetics  106-  (592)  33  -36  2007/03/09  [Not refereed][Not invited]
     
    For the optical measurement in a scattering medium, a fundamental study was conducted on the combination of the ultrasonic modulation and the low-coherence optical interferometry. We have succeeded to detect the optical signal from the focal point of ultrasound in an optical scattering medium without using the reflecting object such as mirror. Using this optical signal, we showed the possibility of the absorption measurement in a scattering medium and clarified the application limit of this technique. Based on these results, we attempted the imaging of the absorption distribution in a scatt...
  • Matsubara Shinichi, Takagi Kazuto, Kato Yuji, Amano Kazuhiko, Shimizu Koichi  IEICE technical report. ME and bio cybernetics  106-  (592)  61  -64  2007/03/09  [Not refereed][Not invited]
     
    For the application to biometrics idenfitication, a fundamental study was conducted on the reflection-type transillumination imaging that is applicable to thick biological tissue. An inhomogeneous attenuation filter was designed to compensate the inhomogeneity in the transillumination image. With this filter, the intensity resolution was improved 8 times higher and the field of view was enlarged more than 4 times larger. Considering the variation of scattering and absorption characteristics among subjects, an inhomogeneous attenuation filter was manufactured. With this filter, transillumina...
  • ITAGAKI Hidenobu, KOIZUMI Ruriko, KATO Yuji, SHIMIZU Koichi  電気学会研究会資料. LAV, 光応用・視覚研究会  2007-  (1)  1  -5  2007/01/12  [Not refereed][Not invited]
  • ENDO Tomoki, KATO Yuji, SHIMIZU Koichi  電気学会研究会資料. LAV, 光応用・視覚研究会  2007-  (1)  7  -12  2007/01/12  [Not refereed][Not invited]
  • 久保善弘, 浪田健, 加藤祐次, 清水孝一  日本生体医工学会大会プログラム・論文集(CD-ROM)  46th-  ROMBUNNO.PS1-14-9  2007  [Not refereed][Not invited]
  • 浪田健, 金澤瑠維, 加藤祐次, 清水孝一  日本分光学会講演要旨集  2006-  136  -137  2006/11  [Not refereed][Not invited]
  • 浪田健, 金澤瑠維, 加藤祐次, 清水孝一  電気・情報関係学会北海道支部連合大会講演論文集(CD-ROM)  2006-  ROMBUNNO.142  2006/10  [Not refereed][Not invited]
  • TAKAGI Kazuto, BETTOYASHIKI Genta, KATO Yuji, SHIMIZU Koichi  IEICE technical report. ME and bio cybernetics  106-  (253)  13  -16  2006/09/18  [Not refereed][Not invited]
     
    Due to the strong scattering of biological tissue, a beam of light propagates in an off-axis area in the body. This makes the spatial resolution of the transillumination image significantly poor. To solve this problem, we propose a new technique to suppress this effect of scattering. By controlling the light propagation path in a scattering medium, we can obtain the near-axis component of the incident light beam. In experiments, the feasibility of the proposed principle was confirmed and the effectiveness was verified using a model-phantom of a biological body.
  • 高木 一人, 加藤 祐次, 清水 孝一  生体医工学 : 日本エム・イー学会誌  44-  (2)  314  -315  2006/06/10  [Not refereed][Not invited]
  • 浪田健, 金澤瑠雄, 加藤祐次, 清水孝一  日本生体医工学会大会プログラム・論文集  45th-  604  2006/05  [Not refereed][Not invited]
  • KOIZUMI Ruriko, KATO Yuji, SHIMIZU Koichi  IEICE technical report. ME and bio cybernetics  105-  (578)  29  -32  2006/01/21  [Not refereed][Not invited]
     
    The image observed at the body surface is deteriorated due to the strong scattering of the body tissue. To solve this problem, a fundamental study was conducted. It was confirmed that the image was improved effectively by the deconvolution with the theoretically derived point spread function (PSF). It was effective only when the depth of the fluorescent source was known a priori. We have developed a new technique to estimate the depth of the fluorescent source in the deconvolution with the derived PSF. With this technique, we can recover the correct image of the fluorescent source from the ...
  • 浪田健, 加藤祐次, 清水孝一  日本ME学会大会論文集  44th-  331  2005/04  [Not refereed][Not invited]
  • TAKAGI Kazuto, KATO Yuji, SHIMIZU Koichi  IEICE technical report. ME and bio cybernetics  104-  (757)  1  -4  2005/03/23  [Not refereed][Not invited]
     
    For practical transillumination imaging of biological body, we have to suppress the scattered component in transmitted light. With the previously proposed technique, mechanical scanning was necessary to obtain 2-dimensional transillumination images. We propose a new technique to eliminate this mechanical scanning. We can suppress the scattered component in the transmitted light by the weighted subtraction of the image after the scattering-increase from the image before the scattering-increase. Using a scattering plate, we can apply this technique to an animal body. The feasibility was verif...
  • WATANABE Eijiro, KATO Yuji, SHIMIZU Koichi  IEICE technical report. ME and bio cybernetics  104-  (757)  5  -8  2005/03/23  [Not refereed][Not invited]
     
    For the measurement of NIR absorption distribution in a biological body, a new technique to use the interaction of light and ultrasound has been devised. In this technique, we provide a plural number of ultrasonic modulation regions in the scattering medium in which light propagates. Using the modulation frequency, we can selectively detect the light which passed along the straight line between the modulation regions. In experimental study, the feasibility of the proposal technique was verified. In the absorption measurement, the possibility to suppress the scattering effect was demonstrated.
  • NAMITA Takeshi, KATO Yuji, SHIMIZU Koichi  IEICE technical report. ME and bio cybernetics  104-  (757)  9  -12  2005/03  [Not refereed][Not invited]
     
    A technique has been developed to obtain tomographic image of scattering object by the time-resolved measurement of backscattered light. A fundamental study was conducted to make the proposed technique practicable. The estimation error could be reduced less then half by increasing the optical power of the ultra-short pulse-laser by 100 times. The feasibility of stable CT imaging was verified by stabilizing the object. The results of this experimental study suggest that the problems of the proposed technique are not essential and that they can be technically overcome.
  • Shimizu K, Tochio K, Kato Y  Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference  3-  3141  -3144  2005  [Refereed][Not invited]
  • Shimizu Ken, Kato Yuji, Shimizu Koichi  IEICE technical report. ME and bio cybernetics  103-  (730)  31  -36  2004/03/10  [Not refereed][Not invited]
     
    For transillumination of small animal and near-surface imaging of animal body, fundamental study was conducted on the light propagation in random media. Through the measurement of attenuation, degree of polarization and coherency, it was found that the effect of multiple scattering appeared in the biological tissue with the thickness of more than 1-3 mm. Since the conventional solution of the diffusion equation is not applicable in this scattering region, new solution was derived from the equation of transfer by applying the small angle approximation. The reasonability of the solution was v...
  • TAKAHARA Shusaku, KATO Yuji, SHIMIZU Koichi  IEICE technical report. ME and bio cybernetics  103-  (730)  37  -41  2004/03/10  [Not refereed][Not invited]
     
    Fundamental study was conducted to obtain structural and functional information in a biological body using light and ultra-sound. The low coherence interferometry technique was applied to suppress the effect of the optical scattering between the modulated point and light incidence/output points. The characteristics of a measurement system and the delectability of the modulated signal by the proposed method were investigated. It was shown experimentally that the detectable depth of the modulated signal increased with the increase of the coherence length of a light source. In a phantom experi...
  • AKIYAMA Koji, NISHIDA Yohei, KATO Yuji, SHIMIZU Koichi  IEICE technical report. ME and bio cybernetics  102-  (727)  1  -4  2003/03/11  [Not refereed][Not invited]
     
    A fundamental study was conducted to realize CT imaging using backscattered light. To estimate the depth-distribution of absorption, a temporal pathlength distribution (TPD) in a scattering object is required. The TPD has been obtained in computer simulation. In this study, we proposed a technique to obtain the TPD in a real measurement. In the experiment using three-layer model phantoms, the effectiveness of the proposed technique was verified. The possibility of CT imaging was demonstrated in the reconstruction of a cross-sectional image of an absorber in a scattering object.
  • TOCHIO Koji, TAKA Yoshinori, KATO Yuji, SHIMIZU Koichi  IEICE technical report. ME and bio cybernetics  102-  (727)  57  -60  2003/03/11  [Not refereed][Not invited]
     
    To realize reflection-type transcutaneous fluorescent imaging, a fundamental study was conducted. The degree of image degradation due to scattering was investigated. The degradation can be improved by the deconvolution using a point spread function(PSF). The fluorescent image of a known object was measured and the PSF was obtained as a function of the object-depth. In a model experiment, the effectiveness of this technique was examined. The visible depth in a scattering medium became almost twice as deep using the depth-depended PSF. The usefulness of this technique was demonstrated in the ...
  • WATANABE Hiromu, TAKAHARA Shusaku, KATO Yuji, SHIMIZU Koichi  IEICE technical report. ME and bio cybernetics  102-  (727)  61  -64  2003/03/11  [Not refereed][Not invited]
     
    Fundamental study was conducted to obtain structural and functional information in a biological body using light and ultrasound. When we use the light modulated the light by ultrasound, a technique is required to extract the information of the modulated position from received light. Based on the principle of optical coherence tomography(KOCT), we propose a technique to detect the light component which has propagated along the straight line between the two points of ultrasonic modulation and light incidence/detection. An experimental system was constructed, and the detectability of the ultra...
  • Okamoto Yasushi, Kitama Masataka, Misawa Kenji, Arisawa Junji, Kato Yuji, Shimizu Koichi  Memoirs of the Hokkaido Institute of Technology  31-  (0)  81  -86  2003/03  [Not refereed][Not invited]
  • OKAMOTO Yasushi, KITAMA Masataka, MISAWA Kenji, ARISAWA Junji, KATO Yuji, SHIMIZU Koichi  IEICE technical report. ME and bio cybernetics  102-  (481)  17  -20  2002/11/21  [Not refereed][Not invited]
     
    Optical imaging of biological tissue has been difficult due to strong scattering. To realize the imaging with near-axis scattered light, we have applied the scattering-angle differential technique and the time-resolved measurement technique to the quantitative CT imaging in a turbid medium. We used a model phantom which contained a cylindrical structure with a coaxial absorption layer. CT images were reconstructed with the proposed technique and compared with those obtained with the conventional collimation technique. The spatial resolution and the accuracy of absorption were improved signi...
  • SATO Fumihiko, SASAKI Toshikazu, KATO Yuji, SHIMIZU Koichi  生体・生理工学シンポジウム論文集  17-  (0)  333  -336  2002/09/09  [Not refereed][Not invited]
  • KATO Y, AKIYAMA K, SHIMIZU K  生体・生理工学シンポジウム論文集  17-  (0)  337  -340  2002/09/09  [Not refereed][Not invited]
  • SATO Fumihiko, SASAKI Toshikazu, KATO Yuji, SHIMIZU Koichi  IEICE technical report. ME and bio cybernetics  101-  (733)  79  -84  2002/03/11  [Not refereed][Not invited]
     
    The detectability and the usefulness of the near-axis scattered light using differential time-resolved method was investigated. The efficient detection of the near-axis scattered light by the proposed technique was confirmed in the examination of the temporal and the spatial characteristics of the detected light. In the absorption measurement of inhomogeneous scatterer, the possibility and the error of the μ_a estimation was shown in comparison with the time-gatng method. The CT image obtained by the proposed technique was superior to those by the time-gating method in the spatial resolutio...
  • KATO Y, AKIYAMA K, SHIMIZU K  レーザー学会学術講演会年次大会講演予稿集 = Annual meeting of the Laser Society of Japan digest of technical papers  22-  (0)  229  -230  2002/01/01  [Not refereed][Not invited]
  • AKIYAMA Koji, KATO Yuji, SHIMIZU Koichi  電気学会基礎・材料・共通部門大会講演論文集 = Proceeding of Annual Conference of Fundamentals and Materials Society, IEE Japan  2001-  (0)  242  -242  2001/09/21  [Not refereed][Not invited]
  • SHIMIZU K, HORIE H, AKIYAMA K, KATO Y  レーザー学会研究会報告 = Reports on the Topical meeting of the Laser Society of Japan  289-  (0)  17  -23  2001/09/07  [Not refereed][Not invited]
  • Horie Hirobumi, Kato Yuji, Shimizu Koichi  IEICE technical report. ME and bio cybernetics  100-  (685)  63  -70  2001/03/15  [Not refereed][Not invited]
     
    For the crosssectional imaging of a biological body, a technique has been developed to reconstruct absorption distribution using time-resolved backscattered light. In this technique, we estimate the absorption distribution quantitatively by applying the operator made from a path-length distribution. In a simulation, the layered absorption distribution of a biological model was reconstructed. The reconstructed distribution agreed well with the given distribution, and the effectiveness of the proposed technique was verified. The stability of the solution in solving the inverse problem was con...
  • Fujiwara Isao, Taka Yoshinori, Kato Yuji, Shimizu Koichi  IEICE technical report. ME and bio cybernetics  100-  (685)  71  -76  2001/03/15  [Not refereed][Not invited]
     
    For transillumination imaging of biological body, image degradation in scattering medium was investigated. The small-angle approximation was applied to the transfer equation to describe the light propagation in scattering medium. As an analytical solution, the point spread function (PSF) was obtained in a closed form for the case of plane-wave incidence and a Gaussian scattering pattern. The solution could well describe the spread of the PSF. To examine the reasonability of the solution, experiments were conducted to measure the PSF through scattering medium. The measured results agreed wel...
  • YAMAOKA M, KATO Y, SHIMIZU K  IEICE technical report. ME and bio cybernetics  100-  (685)  91  -96  2001/03/15  [Not refereed][Not invited]
     
    For the reconstruction of absorption distribution in biological tissue, the application of ultrasound was proposed. The effect of the refraction-index change caused by ultrasound irradiation on the impulse response (time-resolved pulse shape) of backscattered light was investigated in a simulation study. It was found that the peak-time and the peak-magnitude of the impulse response were varied by the ultrasound irradiation on a scattering object. The relation between these variations and the wavelength/phase of ultrasound was clarified. It was also found that the optical path-length distrib...
  • FUKAMI Yuko, Ashidai Hiroshi, Obara Minoru, Morimoto Yuji, Hashishin Y., Tomita K., Nagata H., Fukai T., Nakanishi J., Matsuoka H., Shimizu Koichi, HEYA Manabu, Takagi Kentaro, Kato Yuji, Kitama Masataka, Ohmi Masato, Kurata Takayuki, Haruna Masamitsu, Mohri Shintaro, Abe Yukio, Matsuura Yuji, Kasai Takao, AWAZU Kunio, Shi Yi-Wei, Miyagi Mitsunobu, Pan Zhi-Yun, Konno Yuji, Aizawa Yoshizo, Sasaki R., Nunoyama H., Awazu K., Nakamura Masahiro, Kuwata Masahiro, Shimada Tomoaki, Nakayama Takeyoshi, Matsutani Takaomi, Nishida Yoshio, Yamanaka Masanobu, Izawa Yasukazu, Nakai Sadao, Sato Y., Tokunaga H., Ogawa Y., Oomuro H., Sato Shunichi, Harada N., Parel J. M., Murahara M., OGURA Makoto, WAKISAKA Hitoshi, Naruse Kyota, Sumiyoshi Tetsumi, Kiyoshima Shoichi, Seguchi Kenji, Arai Tsunenori, Asanuma Hiroshi, Sakata Isao, Takemura Takeshi, Nakajima Susumu, Ishihara Miya, Kawauchi Satoko, Kikuchi Makoto  The Review of Laser Engineering  29-  (0)  221  -222,224  2001  [Not refereed][Not invited]
  • TAKA Yoshinori, KATO Yuji, SHIMIZU Koichi  レーザー学会研究会報告 = Reports on the Topical meeting of the Laser Society of Japan  268-  (0)  23  -27  1999/11/12  [Not refereed][Not invited]
  • YAMAZAKI Kinya, KATO Yuji, SHIMIZU Koichi  IEICE technical report. ME and bio cybernetics  98-  (671)  39  -46  1999/03/18  [Not refereed][Not invited]
     
    With intensity-modulated CW light, the same analysis is possible as the time-resolved technique for the scattering phenomena in mammalian tissues. Mainly in simulation, we analyzed the frequency response of scattering medium with inhomogeneous absorption coefficient. Two models were analyzed, i.e. a transmission-type and a reflection-type. In practical conditions, the frequency response of the reflection-type was more sensitive to the absorption change than that of the transmission-type. In the reflection-type, it was found that the frequency response was sensitive to the positions and the ...
  • TAKAGI Kentaro, KATO Yuji, KITAMA Masataka, SHIMIZU Koichi  IEICE technical report. ME and bio cybernetics  98-  (671)  53  -59  1999/03/18  [Not refereed][Not invited]
     
    In the transmitted light through scattering mammalian tissue, there should be a component which traveled along the optical axis of incident light beam. To separate this near-axis scattered light, we have introduced a time-resolved measurement technique to the previously developed spatially differential technique. With this technique, we can accurately determine the weighting coefficient for the differential process. In addition, we can estimate the increase of the pathlength in near-axis scattering. Through experimental study, the effectiveness of this technique was verified, and the useful...
  • IKEYA Masao, KATO Yuji, SHIMIZU Koichi  IEICE technical report. ME and bio cybernetics  97-  (621)  57  -63  1998/03/19  [Not refereed][Not invited]
     
    Fundamental stydy was conducted for the functional imaging with the OCT technique. The possibility of imaging with the spatial resolution of 17μm was confirmed. The interference signals were measured at the surfaces with different scattering and absorption coefficients. The following facts were found. The signal intensity does not depend largely on the change in a scattering coefficient. We can detect the surface of different absorption coefficients, and measure the change in an absorption coefficient. With the developed system, the surface of a light-absorbing object was visualized in a sc...
  • AWATA Aki, KATO Yuji, SHIMIZU Koichi  IEICE technical report. ME and bio cybernetics  97-  (525)  87  -94  1998/01/31  [Not refereed][Not invited]
     
    A technique was developed to reconstruct the cross-sectional image of the absorption distribution in a diffuse medium using backscattered light. With this technique we can get physiological information such as hemoglobin oxygenation in the body noninvasively. In this technique, we illuminate an object with an ultra-short pulse, and measure the time-resolved pulse shape of the light backscattered from the object. The absorption distribution of the scattering object can be estimated using the path-length distribution of photons at each detection time and the intensity of backscattered light a...
  • HARADA T, KATO Y, SHIMIZU K  IEICE technical report. ME and bio cybernetics  96-  (581)  57  -62  1997/03/17  [Not refereed][Not invited]
     
    For the analysis of light propagation in scattering random media, a technique was developed which enables us to reconstruct a time-resolved pulse-shape using intensity modulated CW light. A measurement system was developed, and the feasibility of this technique was verified experimentally. Using the medium with different scattering and absorption coefficients, time-resolved pulse shapes were reconstructed. The reasonability of the result was ascertained in the comparison with the pulse-shapes measured in a time-domain.
  • HIRAYAMA T, KATO Y, SHIMIZU K  IEICE technical report. ME and bio cybernetics  96-  (581)  63  -69  1997/03/17  [Not refereed][Not invited]
     
    To improve the visibility in a scattering medium, a new technique was developed which suppresses the effect of scattering by averaging out the randomness of scattering. First, the degree of the improvement was investigated by quantifying the visibility. The effectiveness of this technique was verified in the imaging of the structure behind various scattering objects. In practical use, this technique can be used with a pair of collimated light source and detector in a rotate-translate mode. The possibility of this mode was demonstrated.
  • TOYA N, KATO Y, SHIMIZU K  IEICE technical report. ME and bio cybernetics  96-  (581)  85  -90  1997/03/17  [Not refereed][Not invited]
     
    To realize the wireless integration of many medical equipments, a fundamental study was conducted. The possibility of multichannel data-transmission using a spread spectrum technique and indirectlight communication was investigated. Instead of ASK, PSK was used for the primary modulation. For the error control, ARQ technique was introduced. The input level of a SAW convolver was stabilized with an AGC circuit. With these improvements, the data transmission became possible even in the condition with a negative CNR. In ECG transmission, the quality was satisfactory even when the CNR is close ...
  • Suzumura Masato, Kato Yuji, Miyagi Mitsunobu  Proceedings of the IEICE General Conference  1997-  (1)  215  -215  1997/03/06  
    Er:YAGレーザは光を含む電磁波の中で水に対する吸収が最も大きいということから, 歯科無痛治療等の医療分野で大きく注目されている。筆者等は, このEr:YAGレーザ光用の伝送路としてポリイミド樹脂内装銀中空ガラス導波路の開発を行ってきている。今回, 導波路の長さをこれまでの1 m程度から2 m程度と長尺にして製作を行い, その伝送特性の測定を行った。また, 導波路の機械強度の評価も行ったので, 併せて報告する。
  • SHIMIZU Koichi, KATO Yuji, YAMAMOTO Katsuyuki  rle  17-  (0)  308  -311  1997/01/01  [Not refereed][Not invited]
  • SUZUMURA Masato, WANG You, KATO Yuji, HONGO Akihito, MIYAGI Mitsunobu  レーザー学会研究会報告 = Reports on the Topical meeting of the Laser Society of Japan  230-  7  -11  1996/07/25
  • SHIMIZU Koichi, KATO Yuji, YAMAMOTO Katsuyuki  レーザー学会研究会報告 = Reports on the Topical meeting of the Laser Society of Japan  230-  (0)  37  -42  1996/07/25  [Not refereed][Not invited]
  • Takaya J, Kitama M, Kato Y, Shimizu K, Yamamoto K, Kaneko M  IEICE technical report. ME and bio cybernetics  95-  (597)  19  -24  1996/03/19  [Not refereed][Not invited]
     
    A fundamental study has been conducted on the applicability of low-coherence interferometry to the functional CT imaging of biological tissues with light. First, we examined the effectiveness of the proposed technique to suppress the scattering component in the transmitted light. Then, it was shown that we could estimate the absorption coefficient of a scattering medium even in the strong scattering like in a living tissue. Finally, this technique was applied to a rat blood. Using two different wavelengths of light, we could detect the local change in the redox state of the blood.
  • Kubota Satoshi, Kato Yuji, Akama Yosuke, Miyagi Mitsunobu  Proceedings of the IEICE General Conference  1996-  (1)  265  -265  1996/03/11  
    赤外域に発振波長を持つ高出力レーザ光の伝送路として、石英キャピラリーチューブ内に銀層並びに有機樹脂薄膜を有する、誘電体内装中空導波路が提案されている。銀層の成膜には簡便な銀鏡反応が用いられているが、銀中空導波路の特性は誘電体内装後の伝送路の特性に大きな影響を及ぼす。本報告では、光学特性の測定及びSEMによる銀中空導波路の内面観察から、銀中空導波路製作の最適条件について報告する。
  • SUZUMURA Masato, KATO Yuji, SHIMOMURA Takehiro, MIYAGI Mitsunobu  レーザー学会学術講演会年次大会講演予稿集 = Annual meeting, of the Laser Society of Japan digest of technical papers  16-  321  -321  1996/01/01
  • WANG You, KATO Yuji, SHIMOMURA Takehiro, MIYAGI Mitsunobu  レーザー学会学術講演会年次大会講演予稿集 = Annual meeting, of the Laser Society of Japan digest of technical papers  16-  320  -320  1996/01/01
  • Osawa M., Kato Y., Miyagi M., Abe S., Aizawa M., Onodera S.  Proceedings of the IEICE General Conference  1995-  (1)  272  -272  1995/03/27  
    Er:YAGレーザ等の高出力赤外レーザ光は医療分野、工業加工分野においての応用が盛んに進められている。それらレーザ光をフシキシブルかつ高効率に伝送する装置として誘電体内装中空導波路が研究されており、筆者らはガラスキャピラリーチューブ内面に銀鏡反応及び弗素樹脂(FCP)のDip-coatingによりFCP内装銀中空ガラス導波路(FCP/Ag導波路)を製作している。本論文において、銀鏡反応による銀チューブ製作の再現性の向上及び低損失化、また製作したFCP/Ag導波路の損失波長特性、及びEr.YAGレーザ光伝送特性について報告する。
  • KATO Y., OSAWA M., KUBOTA S., MIYAGI M., ABE S., AIZAWA M., ONODERA S.  レーザー学会学術講演会年次大会講演予稿集 = Annual meeting, of the Laser Society of Japan digest of technical papers  15-  308  -308  1995/01/01
  • 加藤祐次  レーザ学会研究会報告  37  -41  1995
  • Kato Yuji, Ohsawa Mitsuo, Miyagi Mitsunobu, Aizawa Masaru, Abe Shin-ichi, Onodera Shinji  Technical report of IEICE. OCS  94-  (335)  1  -6  1994/11/17  
    Polyimide-polymer coated silver hollow infrared waveguides with 700 μm inner diameter and 1 m length have been fabricated for the medical applications.By measurements of the loss spectra and loss for the Er:YAG laser light of the wave guides,it is shown that this waveguides have low-loss characteristics.The heat resisting polyimide-polymer has many advantages over other dielectrics such as non-toxicity and durability.Furthermore,by using silica capillary tube as a base tube,this waveguide is shown to be very flexible.
  • Osawa M., Kato Y., Miyagi M., Abe S., Aizawa M., Onodera S.  電子情報通信学会秋季大会講演論文集  1994-  (1)  224  -224  1994/09/26  
    現在医療分野へのEr:YAG、CO、CO_2等の赤外レーザの応用が盛んに進められており、それら赤外レーザ光をフレキシブルかつ高効率に伝送する装置として誘電体内装金属中空導波路が研究されている。医療用の導波路には量産性及び細径化が必要であり、内装する誘電体としては人体に対して無害かつ対環境性に優れているものが望まれる。今回これらの要件を念頭に置き、ガラスパイプ内面に銀及びフッ素樹脂を内付け法により成膜し、導波路を製作した。
  • Kato Y., Osawa M., Miyagi M., Abe S., Aizawa M., Onodera S.  電子情報通信学会秋季大会講演論文集  1994-  (1)  223  -223  1994/09/26  
    近年、Er:YAGやCO_2レーザ等の赤外レーザは医療用の治療デバイスとして大きく注目されている。これらレーザ光の効率的な利用には、フレキシブルな伝送媒体が重要であり、大きな切開を必要としない最小侵装医療やレーザの特徴を生かした歯科無痛治療の進展に、伝送路は不可欠である。筆者等は、これら赤外レーザ光用の伝送路として誘電体内装中空導波路の開発を行ってきているが、導波路の細径化と低損失化が大きな課題となっている。この課題を解決するために、内付け技術を用いた銀及び有機材料の成膜による導波路の製作技術について研究を行っている。本報告では、内装する誘電体としてポリイミド樹脂を新たに取り上げ、製作した導波路の伝送特性等について述べる。

Books etc

Presentations

  • Evaluation of controlled release from doxorubicin-loaded nanoparticles under ultrasound irradiation
    新里美瑠, 加藤祐次, 橋本守, 工藤信樹
    日本生体医工学会大会プログラム・抄録集(Web)  2021
  • Influence of optical properties of surrounding medium on vein diameter and depth estimation for non-invasive measurement of lipid concentration in blood
    難波昂暉, 加藤祐次
    応用物理学会北海道支部/日本光学会北海道支部合同学術講演会講演予稿集  2021
  • Sogo Toda, Yuji Kato, Nobuki Kudo, Koichi Shimizu
    Progress in Biomedical Optics and Imaging - Proceedings of SPIE  2019/01  SPIE-INT SOC OPTICAL ENGINEERING
     
    © COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only. Strong scattering in turbid medium is a severe difficulty for optical imaging and measurement in an animal body. Therefore, the suppression of scattering effect is crucially important in many applications of biomedical optics. In the optical transillumination imaging of an animal body, this effect appears as strong blurring of the image. This blurring poses a fundamentally important difficulty restricting the practical application of transillumination imaging. Therefore, we have attempted to suppress scattering effect using the time-reversal ability of phase-conjugate light. For our previous study, we constructed a digital system to generate light not only with conjugated phase but also with the same intensity distribution as non-scattered signal light. Using this system, we were able to restore the pattern of incident light from the blurred image because of time-reversal propagation of the phase-conjugate light. In comparison to a case with phase information only, we found that addition of the intensity information greatly improves the scattering suppression capability of the time-reversal principle. However, our pilot study showed this ability was valid only for the scattering medium with the optical distance OD less than 1. This report describes the improvement of our measurement system to make the scattering suppression possible for turbid media with OD of more than 1 using a light source with a longer coherence length. Scattering suppression was effective for spatial frequencies of 0.4-1.0 lp/mm through the scattering medium up to OD=1.8.
  • 下川部一真, 高見澤淳, 飯永一也, 橋本守, 加藤祐次
    日本生体医工学会大会プログラム・抄録集(Web)  2019
  • 任田崇吾, 加藤祐次, 工藤信樹, 清水孝一
    レーザー学会研究会報告  2018
  • 後方散乱光を用いた血中トリグリセリド濃度の非侵襲的計測法 予備的検証
    松村 健太, 加藤 祐次, 飯永 一也, 清水 孝一
    脂質栄養学  2017/08  日本脂質栄養学会
  • 上田康夫, 加藤祐次, 山口泰彦, 清水孝一
    日本デジタル歯科学会誌(Web)  2017/04
  • 加藤祐次, 宮島文佳, 清水孝一
    レーザー学会研究会報告  2017
  • 上田康夫, 加藤祐次, 山口泰彦, 清水孝一
    日本補綴歯科学会誌(Web)  2017
  • 松村健太, 加藤祐次, 飯永一也, 清水孝一
    脂質栄養学  2017
  • 任田崇吾, 加藤祐次, 工藤信樹, 清水孝一
    Optics & Photonics Japan講演予稿集(CD-ROM)  2016/10
  • 任田崇吾, 加藤祐次, 清水孝一
    電子情報通信学会技術研究報告  2016/03
  • 岡崎恵祐, 加藤祐次, 清水孝一
    電子情報通信学会技術研究報告  2016/03
  • WANG Lei, 飯永一也, 加藤祐次, 清水孝一
    電子情報通信学会技術研究報告  2016/03
  • 宮島文佳, 加藤祐次, 清水孝一
    電子情報通信学会技術研究報告  2016/03
  • Sogo Toda, Yuji Kato, Nobuki Kudo, Koichi Shimizu
    Transactions of Japanese Society for Medical and Biological Engineering  2016/01 
    © 2016, Japan Soc. of Med. Electronics and Biol. Engineering. All rights reserved. The scattering effect in light propagation through random media can be suppressed with the phase-conjugate optics. We have applied this technique to the transillumination imaging of animal body using a digital phase-conjugate system. In the experiment, we attempted to restore various incident light patterns through a scattering medium. As a result, the feasibility of scattering suppression using digital phase-conjugate light was verified.
  • 任田崇吾, 加藤祐次, 清水孝一
    電気・情報関係学会北海道支部連合大会講演論文集(CD-ROM)  2015/11
  • 宮島文佳, 加藤祐次, 清水孝一
    Optics & Photonics Japan講演予稿集(CD-ROM)  2015/10
  • WANG Lei, 飯永一也, 加藤祐次, 磯村哲, 清水孝一
    Optics & Photonics Japan講演予稿集(CD-ROM)  2015/10
  • 岡崎恵祐, 加藤祐次, 清水孝一
    Optics & Photonics Japan講演予稿集(CD-ROM)  2015/10
  • 任田崇吾, 加藤祐次, 清水孝一
    Optics & Photonics Japan講演予稿集(CD-ROM)  2015/10
  • 開田翔一, 松村健太, 加藤祐次, 清水孝一
    電子情報通信学会技術研究報告  2015/03
  • 佐々木洋天, 浪田健, 加藤祐次, 清水孝一
    電子情報通信学会技術研究報告  2015/03
  • 田中宏幸, 浪田健, 加藤祐次, 清水孝一
    電子情報通信学会技術研究報告  2015/03
  • 関大輔, 浪田健, 加藤祐次, 清水孝一
    電子情報通信学会技術研究報告  2015/03
  • 開田翔一, 松村健太, 加藤祐次, 清水孝一
    電気学会全国大会講演論文集(CD-ROM)  2015/03
  • 開田翔一, 松村健太, 加藤祐次, 清水孝一
    応用物理学会北海道支部・日本光学会北海道地区合同学術講演会講演予稿集  2015/01
  • 宮島文佳, 加藤祐次, 清水孝一
    応用物理学会北海道支部・日本光学会北海道地区合同学術講演会講演予稿集  2015/01
  • WANG Lei, 飯永一也, 加藤祐次, 清水孝一
    日本生体医工学会大会プログラム・論文集(CD-ROM)  2015
  • 宮島文佳, 加藤祐次, 清水孝一
    日本生体医工学会大会プログラム・論文集(CD-ROM)  2015
  • 岡崎恵祐, 加藤祐次, 清水孝一
    日本生体医工学会大会プログラム・論文集(CD-ROM)  2015
  • 任田崇吾, 加藤祐次, 清水孝一
    日本生体医工学会大会プログラム・論文集(CD-ROM)  2015
  • WANG Lei, 飯永一也, 加藤祐次, 清水孝一
    電気・情報関係学会北海道支部連合大会講演論文集(CD-ROM)  2014/10
  • 岡崎恵祐, 加藤祐次, 清水孝一
    電気・情報関係学会北海道支部連合大会講演論文集(CD-ROM)  2014/10
  • 田中宏幸, 浪田健, 加藤祐次, 清水孝一
    Optics & Photonics Japan講演予稿集(CD-ROM)  2014/10
  • Development of new optical CT for 3D animal imaging using NIR transillumination images  [Not invited]
    Tran Trung Nghia, Kohei Yamamoto, Takeshi Namita, Yuji Kato, Koichi Shimizu
    IEICE Tech. Rep  2014/06
  • Development of new optical CT for 3D animal imaging - Practical technique using transillumination images -  [Not invited]
    Trung Nghia Tran, Kohei Yamamoto, Takeshi Namita, Yuji Kato, Koichi Shimizu
    Biomedical Imaging and Sensing Conference, part of Optics & Photonics International 2014 Congress  2014/05
  • Attempt for optical BAN on human body  [Not invited]
    Daisuke Seki, Takeshi Namita, Yuji Kato, Koichi Shimizu
    Proceedings of 20 th Symposium of the Internationa Society on Biotelemetry  2014/05
  • 後方散乱光時間分解計測による吸収係数分布の高精度推定の試み  [Not invited]
    大場一寛, 横山直弥, 浪田 健, 加藤祐次, 清水孝一
    電子情報通信学会技術研究報告  2014/03
  • 光による生体透視イメージングのための拡散媒質内部吸光像の画像改善  [Not invited]
    山本航平, チャン チュン ギア, 浪田 健, 加藤祐次, 清水孝一
    電子情報通信学会技術研究報告  2014/03
  • 円柱状光拡散体における内部蛍光体イメージング手法の開発 ～ 生体内部蛍光体の経皮透視をめざして ～  [Not invited]
    小川大貴, 浪田 健, 加藤祐次, 清水孝一
    電子情報通信学会技術研究報告  2014/03
  • 実測点拡がり関数を用いた前腕血管の光透視 ～ 人工透析における内シャント管理への応用 ～  [Not invited]
    夏目裕也, 浪田 健, 加藤祐次, 北間正崇, 清水孝一
    電子情報通信学会技術研究報告  2014/03
  • 3D reconstruction of internal structure of animal body using near-infrared light  [Not invited]
    Tran Trung Nghia, Kohei Yamamoto, Takeshi Namita, Yuji Kato, Koichi Shimizu
    Proc. SPIE  2014/02
  • Trung Nghia Tran, Kohei Yamamoto, Takeshi Namita, Yuji Kato, Koichi Shimizu
    Progress in Biomedical Optics and Imaging - Proceedings of SPIE  2014/01 
    To realize three-dimensional (3D) optical imaging of the internal structure of animal body, we have developed a new technique to reconstruct CT images from two-dimensional (2D) transillumination images. In transillumination imaging, the image is blurred due to the strong scattering in the tissue. We had developed a scattering suppression technique using the point spread function (PSF) for a fluorescent light source in the body. In this study, we have newly proposed a technique to apply this PSF for a light source to the image of unknown light-absorbing structure. The effectiveness of the proposed technique was examined in the experiments with a model phantom and a mouse. In the phantom experiment, the absorbers were placed in the tissue-equivalent medium to simulate the light-absorbing organs in mouse body. Near-infrared light was illuminated from one side of the phantom and the image was recorded with CMOS camera from another side. Using the proposed techniques, the scattering effect was efficiently suppressed and the absorbing structure can be visualized in the 2D transillumination image. Using the 2D images obtained in many different orientations, we could reconstruct the 3D image. In the mouse experiment, an anesthetized mouse was held in an acrylic cylindrical holder. We can visualize the internal organs such as kidneys through mouse's abdomen using the proposed technique. The 3D image of the kidneys and a part of the liver were reconstructed. Through these experimental studies, the feasibility of practical 3D imaging of the internal light-absorbing structure of a small animal was verified. © 2014 SPIE.
  • Koichi Shimizu, Takeshi Namita, Yuji Kato
    Lecture Notes of the Institute for Computer Sciences, Social-Informatics and Telecommunications Engineering, LNICST  2013/12 
    For a new optical body area network (BAN) technique, a fundamental study was conducted of optical data transmission through a human body using diffusely scattered light. The frequency bandwidth for data transmission was restricted by the effect of strong scattering inside body tissues. In experiments using human bodies, the possibility of the transmission up to 100 MHz was confirmed. Using the linear equalization process, we can transmit an 800 MHz square wave signal. Data transmission of around 200 mm distance in a human hand was possible. To overcome problems of noise, multipath transmission, and the instantaneous interruption of data transmission, the space diversity (SD) technique was applied to stabilize data communications. The SD technique effectiveness was confirmed through analysis using real optical impulse responses. The feasibility of BAN using diffusely scattered light in the body was verified through these analyses. © Institute for Computer Sciences, Social Informatics and Telecommunications Engineering 2013.
  • Trung Nghia Tran, Takeshi Namita, Yuji Kato, Koichi Shimizu
    Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS  2013/10 
    In transillumination imaging of an animal body using near-infrared light, the image is blurred due to the strong scattering in the tissue. We have devised the depth-dependent point spread function (PSF) to suppress the scattering effect in fluorescent imaging. In this study, we applied this principle and developed a technique to reconstruct the absorbing structure in turbid medium without using fluorescent material. In experiments, the feasibility and effectiveness of the proposed technique were verified. © 2013 IEEE.
  • Taiki Matsuura, Takeshi Namita, Yuji Kato, Koichi Shimizu
    Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS  2013/10 
    In transillumination imaging of an animal body with near-infrared light, the shallower structure appears clearer. Therefore, we can reconstruct the three dimensional (3D) image of the shallow structure using the transillumination images as the projection images. In the 3D reconstruction, it may be better to use the projection images of limited observation-angle range rather than those from 360° range. We investigated this possibility and devised a new technique to reconstruct the 3D image of the light absorbing structure in shallow region of a turbid medium. This technique is applicable to the turbid object without any a priori knowledge on the angular position of the absorbing structure. The feasibility of the proposed technique was verified in experiments. © 2013 IEEE.
  • OBATA KYOHEI, NAMITA TAKESHI, KATO YUJI, SHIMIZU KOICHI
    電子情報通信学会技術研究報告  2013/03
  • MORIMOTO TAKURO, NAMITA TAKESHI, KATO YUJI, SHIMIZU KOICHI
    電子情報通信学会技術研究報告  2013/03
  • XIA JIAO, NAMITA TAKESHI, KATO YUJI, SHIMIZU KOICHI
    電子情報通信学会技術研究報告  2013/03
  • OKUYAMA YUKI, NAMITA TAKESHI, KATO YUJI, SHIMIZU KOICHI
    電子情報通信学会技術研究報告  2013/03
  • AKIYAMA JUNKICHI, NAMITA TAKESHI, KATO YUJI, SHIMIZU KOICHI
    電子情報通信学会技術研究報告  2013/03
  • MATSUURA TAIKI, NAMITA TAKESHI, KATO YUJI, SHIMIZU KOICHI
    電子情報通信学会技術研究報告  2013/03
  • YOKOTA SHUN, NAMITA TAKESHI, KATO YUJI, SHIMIZU KOICHI
    電子情報通信学会技術研究報告  2013/03
  • 加藤祐次, 浪田健, 清水孝一
    電気・情報関係学会北海道支部連合大会講演論文集(CD-ROM)  2012/10
  • 関大輔, 浪田健, 加藤祐次, 清水孝一
    電子情報通信学会大会講演論文集(CD-ROM) 2013 ROMBUNNO.BS-9-5  2012/09
  • 森本拓朗, 浪田健, 加藤祐次, 清水孝一
    生体医工学  2012/08
  • OTANI MASAFUMI, NAMITA TAKESHI, KATO YUJI, SHIMIZU KOICHI
    電子情報通信学会技術研究報告  2012/03
  • TOZAWA EIJI, NAMITA TAKESHI, KATO YUJI, SHIMIZU KOICHI
    電子情報通信学会技術研究報告  2012/03
  • SUGIYAMA KEITA, NAMITA TAKESHI, KATO YUJI, SHIMIZU KOICHI
    電子情報通信学会技術研究報告  2012/03
  • NISHIDA KOHEI, NAMITA TAKESHI, KATO YUJI, SHIMIZU KOICHI
    電子情報通信学会技術研究報告  2012/03
  • MATSUDA YASUSHI, NAMITA TAKESHI, KATO YUJI, SHIMIZU KOICHI
    電子情報通信学会技術研究報告  2012/03
  • TAKAHASHI HIROKI, NAMITA TAKESHI, KATO YUJI, SHIMIZU KOICHI
    電子情報通信学会技術研究報告  2012/03
  • 小幡恭平, 浪田健, 加藤祐次, 清水孝一
    日本生体医工学会大会プログラム・論文集(CD-ROM)  2012
  • 秋山潤吉, 浪田健, 加藤祐次, 清水孝一
    日本生体医工学会大会プログラム・論文集(CD-ROM)  2012
  • Koichi Shimizu, Takeshi Namita, Yuji Kato
    Wireless Mobile Communication and Healthcare - Third International Conference, MobiHealth 2012, Paris, France, November 21-23, 2012, Revised Selected Papers  2012
  • SHIMANO Moto, NAMITA Takeshi, KATO Yuji, SHIMIZU Koichi
    IEICE technical report. ME and bio cybernetics  2011/02 
    To see through a turbid medium, a technique was developed to reconstruct a three-dimensional structure inside the medium. Clear transillumination images were obtained with a scattering suppression technique in which the weakly scattered light component can be extracted from the strongly diffused light. The possibility of the proposed technique was examined in the experiment using the turbid medium with known internal structure. Through the experimental analysis, the feasibility of the proposed technique and the effectiveness of the scattering suppression were verified.
  • TOBISAWA Naoya, NAMITA Takeshi, KATO Yuji, SHIMIZU Koichi
    IEICE technical report. ME and bio cybernetics  2011/02 
    To assist vascular injection, we have developed a simultaneous observation system using a body surface image and a transillumination image of blood vessels. Light source was devised to make homogeneous, wide-area and low-leak illumination possible. Using the developed system, we could obtain the transillumination images in all part of the adult forearm with as much as 67 mm thickness. In addition to the superficial veins, we could visualize the arteries in the forearm. Its usefulness was examined in the simulation of injection with a phantom of the human forearm.
  • Injection Assist System with Surface and Transillumination Images  [Not invited]
    Naoya Tobisawa, Takeshi Namita, Yuji Kato, Koichi Shimizu
    The 5th International Conference on Bioinformatics and Biomedical Engineering  2011
  • Reconstruction of Three-Dimensional Structure in Turbid Medium by Scattering Suppression  [Not invited]
    Moto Shimano, Takeshi Namita, Yuji Kato, Koichi Shimizu
    The International Symposium on Photonics and Optoelectronics (SOPO 2011)  2011
  • New technique to estimate non-absorbing temporal point spread function for diffuse optical tomography using backscattered light  [Not invited]
    Takeshi Namita, Masafumi Otani, Yuji Kato, Koichi Shimizu
    IQEC/CLEO Pacific Rim 2011 Conference Proceedings  2011
  • 3D reconstruction of internal structure of animal body using NIR light – Preliminary results for feasibility study -  [Not invited]
    Trung Nghia TRAN, Takeshi Namita, Yuji Kato, Koichi Shimizu
    The 1st International Symposium on Engineering Physics and Mechanics  2011
  • Feasibility study for 3D reconstruction of internal structure of animal body using NIR light  [Not invited]
    Trung Nghia Tran, Takeshi Namita, Yuji Kato, Koichi Shimizu
    Proceedings of the 4th International Conference on the Development of Biomedical Engineering  2011
  • Application of transillumination imaging to injection assist system  [Not invited]
    Koichi Shimizu, Naoya Tobisawa, Trung Nghia Tran, Takeshi Namita, Yuji Kato
    Proceedings of the 4th International Conference on the Development of Biomedical Engineering  2011
  • Point Spread Function for Optical Transillumination Imaging of Animal Body  [Not invited]
    Koichi Shimizu, Hiroki Takahashi, Takeshi Namita, Yuji Kato
    The 31st PIERS  2011
  • TAKESHITA Yusuke, KATO Yuji, DATE Hiroyuki, SHIMIZU Koichi
    IEICE technical report. ME and bio cybernetics  2010/03 
    A new technique was developed to realize the fluorescence angiography based on the image restoration with point-spread function (PSF). In this technique, the PSF can be obtained using a fluorescence-marked stent placed in a blood vessel. A clear image of the blood vessel can be restored by deconvolving the blurred transcutaneous image with measured PSF. In simulation, the feasibility of the basic idea was confirmed. In the experiments with tissue phantoms, the effectiveness of the proposed technique was verified. Those results suggest the feasibility of the repetitive examination of vessel ...
  • SHIMIZU Atsushi, KATO Yuji, SHIMIZU Koichi
    IEICE technical report. ME and bio cybernetics  2010/03 
    Transcutaneous fluorescent images are deteriorated due to the optical scattering of body tissues. Using a depth-depending PSF(point spread function), this effect can be suppressed effectively. We have newly developed a technique to estimate the depth of a fluorescent object in a scattering medium with two light sources. The effectiveness of this technique was confirmed in the experiment with a simple fluorescent object in a scattering medium. Then the proposed technique was improved so as to be applicable to the case of multiple fluorescent objects at different depths. Using model phantoms ...
  • CHIKAHISA Tomoya, NAMITA Takeshi, KATO Yuji, SHIMIZU Koichi
    IEICE technical report. ME and bio cybernetics  2010/03 
    The possibility of new biological measurement by time resolved analysis of the optical backscattering enhancement was pursued. Through simulation analysis for various optical parameter changes, the extinction time of the enhancement peak was selected as an index to evaluate the scattering property of the turbid medium such as an animal tissue. The effectiveness of this index was verified in experiments. The range of measurable depth in a scattering medium was analyzed. The results with our experimental system suggested that we can measure the scattering coefficient up to 5 mm depth from the...
  • KAKITA Shun, KATO Yuji, SHIMIZU Koichi
    IEICE technical report. ME and bio cybernetics  2010/03 
    To realize new optical communication through a human body, the feasibility of data transmission using diffusely scattered light in a human body was examined. Transmissible range of optical data in the human maniphalanx was measured. The data transmission through about 100 mm distance was possible with our experimental system. To overcome the problems of the noises, multipath transmission, and the cut of transmission paths, the space diversity (SD) method was applied to stabilize the data communication. In simulation, the effectiveness of the SD method was confirmed. For the SD method, diffe...
  • KAKINUMA Hiroyuki, KATO Yuji, SHIMIZU Koichi
    IEICE technical report. ME and bio cybernetics  2010/03 
    To realize a technique applicable to thicker body, the effectiveness of a transillumination imaging using weakly diffused light was examined in experiments. The possibility to extract the weakly diffused component from strongly diffused light was clarified in spatial and temporal analyses. Apparent improvement of transillumination images was demonstrated with a model phantom and a biological specimen. A technique to estimate the depth of an absorber in disuse medium was newly developed. The stability of the depth estimation technique and its applicability to animal tissue were verified in e...
  • YOSHIMURA Hitoshi, NAMITA Takeshi, KATO Yuji, SHIMIZU Koichi
    IEICE technical report. ME and bio cybernetics  2010/03 
    To realize functional imaging by time-resolved measurement of backscattered light, a technique has been developed to estimate the spatial distribution of tissue oxygen saturation. In theoretical analysis on the estimation error, the measurement conditions to suppress the error were clarified. The effectiveness of the proposed technique was verified in the Monte Carlo simulation with the three-layer model that simulates the hemoglobin concentrations of the cerebral gray matter and the thigh muscle. The noise tolerance of the proposed technique in solving an inverse problem was evaluated. In ...
  • SHIMIZU Koichi, NAMITA Takeshi, KATO Yuji
    電気学会研究会資料. LAV, 光応用・視覚研究会  2010/02
  • KAWASHIMA Masayuki, NAMITA Takeshi, KATO Yuji, SHIMIZU Koichi
    IEICE technical report. ME and bio cybernetics  2010/01 
    We developed a technique to estimate the reduced scattering coefficient (μ_s') of turbid medium by the time-resolved measurement of backscattered light, and verified its feasibility in simulation. Here, we examined the accuracy and the characteristics of the proposed technique in experiments. The estimated values agreed well with those measured by a conventional technique and with those reported by references. The effect of absorption inhomogeneity on μ_s' estimation was investigated. The term that represents the estimation error was successfully separated in the equation of μ_s' estimation...
  • New Technique to Estimate Scattering Coefficient by Time-Resolved Measurement of Backscattered Light  [Not invited]
    Masayuki Kawashima, Takeshi Namita, Yuji Kato, Koichi Shimizu
    Biomedical Optics, OSA Technical Digest (CD)  2010
  • TRIRONGJITMOAH Suchin, SAKURAI Toshihiro, NISHIBATA Yuka, NAMITA Takeshi, KATO Yuji, IINAGA Kazuya, CHIBA Hitoshi, SHIMIZU Koichi
    IEICE technical report. ME and bio cybernetics  2009/06 
    The amount of small dense low density lipoprotein (sdLDL) is known to have high correlation with coronary diseases. To realize a practical quantitative evaluation of sdLDL, we applied the dynamic light scattering (DLS) technique. Three methods were newly developed to estimate the sdLDL fraction in the total LDL using the mean size or the autocorrelation function of the scattered intensity obtained in the DLS measurement. The mathematical solutions for sdLDL fraction were derived in a closed form. The feasibility of the proposed technique was verified in the experiments using latex standard ...
  • SHIDA Genki, KATO Yuji, SHIMIZU Koichi
    IEICE technical report. ME and bio cybernetics  2009/03 
    A new technique was developed to obtain the CT image for the fluorescent material in a biological body. Fluorescent images blurred by scattering are obtained at the body surface from all the circumferential directions. Deblurred images are restored using the depth-dependant point spread function. A CT image can be reconstructed using the deblurred images by the filtered back projection method. The feasibility and the effectiveness of the proposed technique were verified in the simulation and the experiments with a model phantom and a biological sample.
  • AMAI Kenji, TAKAGI Kazuto, KATO Yuji, AMANO Kazuhiko, SHIMIZU Koichi
    IEICE technical report. ME and bio cybernetics  2009/03 
    To realize next-generation actionless personal authentication, fundamental study was conducted to develop a wearable sensor for vein authentication. A transillumination image of blood vessels was obtained in a circular light source of epi-illumination. The major inhomogeneity over the total view area could be compensated by the attenuation filter designed from the diffusion theory. The effect of discrete light sources and the image processing for local inhomogeneity were investigated. Through this study, we could obtain the transillumination image of sufficient quality for vein authentication.
  • NEMOTO Tomoyuki, KATO Yuji, SHIMIZU Koichi
    IEICE technical report. ME and bio cybernetics  2009/03 
    For the measurement of the functional information in a biological body such as the oxygenation of the blood in the blood vessel in vivo, a technique was developed to measure scattering and absorption characteristic of flowing scattering medium by Doppler OCT principle. The intensity of the Doppler signal caused by the blood flow is measured in the spatially resolved measurement of OCT. We can estimate the optical characteristics of the blood from the attenuation of this signal with the distance in the depth direction. The concentration of an absorbing component in the blood can be also esti...
  • TANAKA Yoshinori, KITAMA Masataka, ARISAWA Junji, TAKAGI Kazuto, KATO Yuji, SHIMIZU Koichi
    IEICE technical report. ME and bio cybernetics  2009/01 
    A fundamental study was conducted on the tomographic imaging using near-axis scattered light for small experimental animals. We velified the feasibility of CT imaging by extracting the near-axis scattered light using the optical difference principle. We showed that the quantitative CT imaging of absorption distribution is possible. The spatial resolution of CT images obtained with our experimental system was evaluated as about 1mm.
  • 北山敬士, 高木一人, 加藤祐次, 清水孝一
    日本生体医工学会大会プログラム・論文集(CD-ROM)  2009
  • 志田元毅, 加藤祐次, 清水孝一
    日本生体医工学会大会プログラム・論文集(CD-ROM)  2009
  • 吉村仁志, 浪田健, 加藤祐次, 清水孝一
    日本生体医工学会大会プログラム・論文集(CD-ROM)  2009
  • 近久智哉, 浪田健, 加藤祐次, 清水孝一
    日本生体医工学会大会プログラム・論文集(CD-ROM)  2009
  • Effect of imaginary layer division in diffuse optical tomography using backscatterd light  [Not invited]
    Takeshi Namita, Yuji Kato, Koichi Shimizu
    The 4th Asian and Pacific Rim Symposium on Biophotonics  2009
  • xtraction of Weakly Scattered Light of Transillumination Imaging  [Not invited]
    Kazuto Takagi, Hiroyuki Kakinuma, Yuji Kato, Koichi Shimizu
    The 4th Asian and Pacific Rim Symposium on Biophotonics  2009
  • CW Detection of Weakly Scattered Light for Transillumination Imaging of Thick Body  [Not invited]
    Kazuto Takagi, Hiroyuki Kakinuma, Yuji Kato, Koichi Shimizu
    The 3rd International Conference on Bioinformatics and Biomedical Engineering  2009
  • SAITO Toshihide, KAKITA Shun, KATO Yuji, SHIMIZU Koichi
    IEICE technical report. ME and bio cybernetics  2008/03 
    For advanced data communication from implanted device, a fundamental study was conducted on the information transmission inside a biological body using light. To examine the effect of strong optical scattering inside the body, the frequency bandwidth for data transmission was evaluated. In the experiment using meat, the possibility of the transmission up to 100MHz was confirmed. To expand the bandwidth, various signal processing techniques were compared. With the linear equalizing process, we can transmit an 800MHz square wave signal. It was confirmed that 900Mcps transmission becomes possi...
  • KUBO Yoshihiro, NAMITA Takeshi, KATO Yuji, SHIMIZU Koichi
    IEICE technical report. ME and bio cybernetics  2008/03 
    The backscattering enhancement has been studied with continuous light. We attempted the time-resolved analysis for this phenomenon. It was newly found that the width of the backscattering enhancement peak becomes narrower as time goes in the rising time of the time-resolved backscattering pulse from diffuse scattering medium. In the falling time of the backscattering pulse, the backscattering enhancement peak disappears as the time goes. We can evaluate the multiple-scattering characteristics of a sample by measuring the extinction time of the peak. Using latex beads and the Intralipid susp...
  • Goto Yasuo, Kato Yuji, Shimizu Koichi
    IEICE technical report. ME and bio cybernetics  2008/03 
    To realize a simple depth-selective imaging of diffuse medium, a new technique was developed that uses multiple circular light sources, an imaging device, and image subtraction process. If the position of a light source on the body surface changes, the propagation region of scattered light in the body becomes different. The proposed technique detects this difference by image subtraction. In the simulation based on the diffusion theory, the effectiveness of the technique was confirmed. Using a model phantom, the applicability of the technique to mammalian tissue was verified. The possibility...
  • KANAZAWA Rui, NAMITA Takeshi, KATO Yuji, SHIMIZU Koichi
    IEICE technical report. ME and bio cybernetics  2008/01 
    A technique was developed to estimate the scattering coefficient of diffuse medium such as a biological body by the time-resolved measurement of backscattered light. The effectiveness of the technique was confirmed in the Monte Carlo simulation. In the analysis of measurement noise, appropriate conditions of the measurement were obtained. The effect of the inhomogeneity of the absorption coefficient was investigated. The possibility to suppress the effect was demonstrated. In the case of an inhomogeneous scattering coefficient, the meaning of the time-dependent estimated value was clarified.
  • CT imaging of diffuse medium by time-resolved measurement of backscattered light – Evaluation of spatial resolution with biological tissue –  [Not invited]
    Takeshi Namita, Yuji Kato, Koichi Shimizu
    6th International Conference on Optics-photonics Design & Fabrication(CD-ROM)  2008
  • NAMITA Takeshi, KANAZAWA Rui, KATO Yuji, SHIMIZU Koichi
    IEICE technical report. ME and bio cybernetics  2007/06 
    A technique has been developed to obtain tomographic image of scattering object by the time-resolved measurement of backscattered light. In this technique, the object was divided into a few hypothetical layers. To increase the number of the layers, we proposed a new technique based on repetitive estimation processes. The effectiveness of the proposed technique was confirmed using a model phantom with known structure. We could estimate the absorption distribution up to 7mm depth from the surface. The applicability of the proposed technique to real biological tissue was examined experimentall...
  • Matsubara Shinichi, Takagi Kazuto, Kato Yuji, Amano Kazuhiko, Shimizu Koichi
    IEICE technical report. ME and bio cybernetics  2007/03 
    For the application to biometrics idenfitication, a fundamental study was conducted on the reflection-type transillumination imaging that is applicable to thick biological tissue. An inhomogeneous attenuation filter was designed to compensate the inhomogeneity in the transillumination image. With this filter, the intensity resolution was improved 8 times higher and the field of view was enlarged more than 4 times larger. Considering the variation of scattering and absorption characteristics among subjects, an inhomogeneous attenuation filter was manufactured. With this filter, transillumina...
  • Endo Tomoki, Kato Yuji, Shimizu Koichi
    IEICE technical report. ME and bio cybernetics  2007/03 
    For the optical measurement in a scattering medium, a fundamental study was conducted on the combination of the ultrasonic modulation and the low-coherence optical interferometry. We have succeeded to detect the optical signal from the focal point of ultrasound in an optical scattering medium without using the reflecting object such as mirror. Using this optical signal, we showed the possibility of the absorption measurement in a scattering medium and clarified the application limit of this technique. Based on these results, we attempted the imaging of the absorption distribution in a scatt...
  • BETTOYASHIKI Genta, TAKAGI Kazuto, KATO Yuji, SHIMIZU Koichi
    IEICE technical report. ME and bio cybernetics  2007/03 
    For transillumination imaging of biological body, the previously proposed technique was improved to extract near-axis scattered light efficiently. In experiments, it was verified that extraction efficiency can be improved about 10dB using the newly proposed technique. It was confirmed that the propagation area of scattered light can be largely restricted to the near-axis region. In the measurement of absorption distribution in scatterers, the possibility of accurate absorption measurement with good spatial resolution was demonstrated.
  • ENDO Tomoki, KATO Yuji, SHIMIZU Koichi
    電気学会研究会資料. LAV, 光応用・視覚研究会  2007/01
  • ITAGAKI Hidenobu, KOIZUMI Ruriko, KATO Yuji, SHIMIZU Koichi
    電気学会研究会資料. LAV, 光応用・視覚研究会  2007/01
  • TAKAGI Kazuto, BETTOYASHIKI Genta, KATO Yuji, SHIMIZU Koichi
    IEICE technical report. ME and bio cybernetics  2006/09 
    Due to the strong scattering of biological tissue, a beam of light propagates in an off-axis area in the body. This makes the spatial resolution of the transillumination image significantly poor. To solve this problem, we propose a new technique to suppress this effect of scattering. By controlling the light propagation path in a scattering medium, we can obtain the near-axis component of the incident light beam. In experiments, the feasibility of the proposed principle was confirmed and the effectiveness was verified using a model-phantom of a biological body.
  • 高木 一人, 加藤 祐次, 清水 孝一
    生体医工学 : 日本エム・イー学会誌  2006/06
  • KOIZUMI Ruriko, KATO Yuji, SHIMIZU Koichi
    IEICE technical report. ME and bio cybernetics  2006/01 
    The image observed at the body surface is deteriorated due to the strong scattering of the body tissue. To solve this problem, a fundamental study was conducted. It was confirmed that the image was improved effectively by the deconvolution with the theoretically derived point spread function (PSF). It was effective only when the depth of the fluorescent source was known a priori. We have developed a new technique to estimate the depth of the fluorescent source in the deconvolution with the derived PSF. With this technique, we can recover the correct image of the fluorescent source from the ...
  • NAMITA Takeshi, KATO Yuji, SHIMIZU Koichi
    IEICE technical report. ME and bio cybernetics  2005/03 
    A technique has been developed to obtain tomographic image of scattering object by the time-resolved measurement of backscattered light. A fundamental study was conducted to make the proposed technique practicable. The estimation error could be reduced less then half by increasing the optical power of the ultra-short pulse-laser by 100 times. The feasibility of stable CT imaging was verified by stabilizing the object. The results of this experimental study suggest that the problems of the proposed technique are not essential and that they can be technically overcome.
  • WATANABE Eijiro, KATO Yuji, SHIMIZU Koichi
    IEICE technical report. ME and bio cybernetics  2005/03 
    For the measurement of NIR absorption distribution in a biological body, a new technique to use the interaction of light and ultrasound has been devised. In this technique, we provide a plural number of ultrasonic modulation regions in the scattering medium in which light propagates. Using the modulation frequency, we can selectively detect the light which passed along the straight line between the modulation regions. In experimental study, the feasibility of the proposal technique was verified. In the absorption measurement, the possibility to suppress the scattering effect was demonstrated.
  • TAKAGI Kazuto, KATO Yuji, SHIMIZU Koichi
    IEICE technical report. ME and bio cybernetics  2005/03 
    For practical transillumination imaging of biological body, we have to suppress the scattered component in transmitted light. With the previously proposed technique, mechanical scanning was necessary to obtain 2-dimensional transillumination images. We propose a new technique to eliminate this mechanical scanning. We can suppress the scattered component in the transmitted light by the weighted subtraction of the image after the scattering-increase from the image before the scattering-increase. Using a scattering plate, we can apply this technique to an animal body. The feasibility was verif...
  • TAKAHARA Shusaku, KATO Yuji, SHIMIZU Koichi
    IEICE technical report. ME and bio cybernetics  2004/03 
    Fundamental study was conducted to obtain structural and functional information in a biological body using light and ultra-sound. The low coherence interferometry technique was applied to suppress the effect of the optical scattering between the modulated point and light incidence/output points. The characteristics of a measurement system and the delectability of the modulated signal by the proposed method were investigated. It was shown experimentally that the detectable depth of the modulated signal increased with the increase of the coherence length of a light source. In a phantom experi...
  • Shimizu Ken, Kto Yuji, Shimizu Koichi
    IEICE technical report. ME and bio cybernetics  2004/03 
    For transillumination of small animal and near-surface imaging of animal body, fundamental study was conducted on the light propagation in random media. Through the measurement of attenuation, degree of polarization and coherency, it was found that the effect of multiple scattering appeared in the biological tissue with the thickness of more than 1-3 mm. Since the conventional solution of the diffusion equation is not applicable in this scattering region, new solution was derived from the equation of transfer by applying the small angle approximation. The reasonability of the solution was v...
  • WATANABE Hiromu, TAKAHARA Shusaku, KATO Yuji, SHIMIZU Koichi
    IEICE technical report. ME and bio cybernetics  2003/03 
    Fundamental study was conducted to obtain structural and functional information in a biological body using light and ultrasound. When we use the light modulated the light by ultrasound, a technique is required to extract the information of the modulated position from received light. Based on the principle of optical coherence tomography(KOCT), we propose a technique to detect the light component which has propagated along the straight line between the two points of ultrasonic modulation and light incidence/detection. An experimental system was constructed, and the detectability of the ultra...
  • TOCHIO Koji, TAKA Yoshinori, KATO Yuji, SHIMIZU Koichi
    IEICE technical report. ME and bio cybernetics  2003/03 
    To realize reflection-type transcutaneous fluorescent imaging, a fundamental study was conducted. The degree of image degradation due to scattering was investigated. The degradation can be improved by the deconvolution using a point spread function(PSF). The fluorescent image of a known object was measured and the PSF was obtained as a function of the object-depth. In a model experiment, the effectiveness of this technique was examined. The visible depth in a scattering medium became almost twice as deep using the depth-depended PSF. The usefulness of this technique was demonstrated in the ...
  • AKIYAMA Koji, NISHIDA Yohei, KATO Yuji, SHIMIZU Koichi
    IEICE technical report. ME and bio cybernetics  2003/03 
    A fundamental study was conducted to realize CT imaging using backscattered light. To estimate the depth-distribution of absorption, a temporal pathlength distribution (TPD) in a scattering object is required. The TPD has been obtained in computer simulation. In this study, we proposed a technique to obtain the TPD in a real measurement. In the experiment using three-layer model phantoms, the effectiveness of the proposed technique was verified. The possibility of CT imaging was demonstrated in the reconstruction of a cross-sectional image of an absorber in a scattering object.
  • OKAMOTO Yasushi, KITAMA Masataka, MISAWA Kenji, ARISAWA Junji, KATO Yuji, SHIMIZU Koichi
    IEICE technical report. ME and bio cybernetics  2002/11 
    Optical imaging of biological tissue has been difficult due to strong scattering. To realize the imaging with near-axis scattered light, we have applied the scattering-angle differential technique and the time-resolved measurement technique to the quantitative CT imaging in a turbid medium. We used a model phantom which contained a cylindrical structure with a coaxial absorption layer. CT images were reconstructed with the proposed technique and compared with those obtained with the conventional collimation technique. The spatial resolution and the accuracy of absorption were improved signi...
  • KATO Y, AKIYAMA K, SHIMIZU K
    生体・生理工学シンポジウム論文集  2002/09
  • SATO Fumihiko, SASAKI Toshikazu, KATO Yuji, SHIMIZU Koichi
    生体・生理工学シンポジウム論文集  2002/09
  • SATO Fumihiko, SASAKI Toshikazu, KATO Yuji, SHIMIZU Koichi
    IEICE technical report. ME and bio cybernetics  2002/03 
    The detectability and the usefulness of the near-axis scattered light using differential time-resolved method was investigated. The efficient detection of the near-axis scattered light by the proposed technique was confirmed in the examination of the temporal and the spatial characteristics of the detected light. In the absorption measurement of inhomogeneous scatterer, the possibility and the error of the μ_a estimation was shown in comparison with the time-gatng method. The CT image obtained by the proposed technique was superior to those by the time-gating method in the spatial resolutio...
  • KATO Y, AKIYAMA K, SHIMIZU K
    レーザー学会学術講演会年次大会講演予稿集 = Annual meeting of the Laser Society of Japan digest of technical papers  2002/01
  • AKIYAMA Koji, KATO Yuji, SHIMIZU Koichi
    電気学会基礎・材料・共通部門大会講演論文集 = Proceeding of Annual Conference of Fundamentals and Materials Society, IEE Japan  2001/09
  • SHIMIZU K, HORIE H, AKIYAMA K, KATO Y
    レーザー学会研究会報告 = Reports on the Topical meeting of the Laser Society of Japan  2001/09
  • YAMAOKA M, KATO Y, SHIMIZU K
    IEICE technical report. ME and bio cybernetics  2001/03 
    For the reconstruction of absorption distribution in biological tissue, the application of ultrasound was proposed. The effect of the refraction-index change caused by ultrasound irradiation on the impulse response (time-resolved pulse shape) of backscattered light was investigated in a simulation study. It was found that the peak-time and the peak-magnitude of the impulse response were varied by the ultrasound irradiation on a scattering object. The relation between these variations and the wavelength/phase of ultrasound was clarified. It was also found that the optical path-length distrib...
  • Fujiwara Isao, Taka Yoshinori, Kato Yuji, Shimizu Koichi
    IEICE technical report. ME and bio cybernetics  2001/03 
    For transillumination imaging of biological body, image degradation in scattering medium was investigated. The small-angle approximation was applied to the transfer equation to describe the light propagation in scattering medium. As an analytical solution, the point spread function (PSF) was obtained in a closed form for the case of plane-wave incidence and a Gaussian scattering pattern. The solution could well describe the spread of the PSF. To examine the reasonability of the solution, experiments were conducted to measure the PSF through scattering medium. The measured results agreed wel...
  • Horie Hirobumi, Kato Yuji, Shimizu Koichi
    IEICE technical report. ME and bio cybernetics  2001/03 
    For the crosssectional imaging of a biological body, a technique has been developed to reconstruct absorption distribution using time-resolved backscattered light. In this technique, we estimate the absorption distribution quantitatively by applying the operator made from a path-length distribution. In a simulation, the layered absorption distribution of a biological model was reconstructed. The reconstructed distribution agreed well with the given distribution, and the effectiveness of the proposed technique was verified. The stability of the solution in solving the inverse problem was con...
  • TAKA Yoshinori, KATO Yuji, SHIMIZU Koichi
    レーザー学会研究会報告 = Reports on the Topical meeting of the Laser Society of Japan  1999/11
  • TAKAGI Kentaro, KATO Yuji, KITAMA Masataka, SHIMIZU Koichi
    IEICE technical report. ME and bio cybernetics  1999/03 
    In the transmitted light through scattering mammalian tissue, there should be a component which traveled along the optical axis of incident light beam. To separate this near-axis scattered light, we have introduced a time-resolved measurement technique to the previously developed spatially differential technique. With this technique, we can accurately determine the weighting coefficient for the differential process. In addition, we can estimate the increase of the pathlength in near-axis scattering. Through experimental study, the effectiveness of this technique was verified, and the useful...
  • YAMAZAKI Kinya, KATO Yuji, SHIMIZU Koichi
    IEICE technical report. ME and bio cybernetics  1999/03 
    With intensity-modulated CW light, the same analysis is possible as the time-resolved technique for the scattering phenomena in mammalian tissues. Mainly in simulation, we analyzed the frequency response of scattering medium with inhomogeneous absorption coefficient. Two models were analyzed, i.e. a transmission-type and a reflection-type. In practical conditions, the frequency response of the reflection-type was more sensitive to the absorption change than that of the transmission-type. In the reflection-type, it was found that the frequency response was sensitive to the positions and the ...
  • IKEYA Masao, KATO Yuji, SHIMIZU Koichi
    IEICE technical report. ME and bio cybernetics  1998/03 
    Fundamental stydy was conducted for the functional imaging with the OCT technique. The possibility of imaging with the spatial resolution of 17μm was confirmed. The interference signals were measured at the surfaces with different scattering and absorption coefficients. The following facts were found. The signal intensity does not depend largely on the change in a scattering coefficient. We can detect the surface of different absorption coefficients, and measure the change in an absorption coefficient. With the developed system, the surface of a light-absorbing object was visualized in a sc...
  • AWATA Aki, KATO Yuji, SHIMIZU Koichi
    IEICE technical report. ME and bio cybernetics  1998/01 
    A technique was developed to reconstruct the cross-sectional image of the absorption distribution in a diffuse medium using backscattered light. With this technique we can get physiological information such as hemoglobin oxygenation in the body noninvasively. In this technique, we illuminate an object with an ultra-short pulse, and measure the time-resolved pulse shape of the light backscattered from the object. The absorption distribution of the scattering object can be estimated using the path-length distribution of photons at each detection time and the intensity of backscattered light a...
  • TOYA N, KATO Y, SHIMIZU K
    IEICE technical report. ME and bio cybernetics  1997/03 
    To realize the wireless integration of many medical equipments, a fundamental study was conducted. The possibility of multichannel data-transmission using a spread spectrum technique and indirectlight communication was investigated. Instead of ASK, PSK was used for the primary modulation. For the error control, ARQ technique was introduced. The input level of a SAW convolver was stabilized with an AGC circuit. With these improvements, the data transmission became possible even in the condition with a negative CNR. In ECG transmission, the quality was satisfactory even when the CNR is close ...
  • HIRAYAMA T, KATO Y, SHIMIZU K
    IEICE technical report. ME and bio cybernetics  1997/03 
    To improve the visibility in a scattering medium, a new technique was developed which suppresses the effect of scattering by averaging out the randomness of scattering. First, the degree of the improvement was investigated by quantifying the visibility. The effectiveness of this technique was verified in the imaging of the structure behind various scattering objects. In practical use, this technique can be used with a pair of collimated light source and detector in a rotate-translate mode. The possibility of this mode was demonstrated.
  • HARADA T, KATO Y, SHIMIZU K
    IEICE technical report. ME and bio cybernetics  1997/03 
    For the analysis of light propagation in scattering random media, a technique was developed which enables us to reconstruct a time-resolved pulse-shape using intensity modulated CW light. A measurement system was developed, and the feasibility of this technique was verified experimentally. Using the medium with different scattering and absorption coefficients, time-resolved pulse shapes were reconstructed. The reasonability of the result was ascertained in the comparison with the pulse-shapes measured in a time-domain.
  • Suzumura Masato, Kato Yuji, Miyagi Mitsunobu
    Proceedings of the IEICE General Conference  1997/03 
    Er:YAGレーザは光を含む電磁波の中で水に対する吸収が最も大きいということから, 歯科無痛治療等の医療分野で大きく注目されている。筆者等は, このEr:YAGレーザ光用の伝送路としてポリイミド樹脂内装銀中空ガラス導波路の開発を行ってきている。今回, 導波路の長さをこれまでの1 m程度から2 m程度と長尺にして製作を行い, その伝送特性の測定を行った。また, 導波路の機械強度の評価も行ったので, 併せて報告する。
  • SHIMIZU Koichi, KATO Yuji, YAMAMOTO Katsuyuki
    レーザー学会学術講演会年次大会講演予稿集 = Annual meeting, of the Laser Society of Japan digest of technical papers  1997/01
  • SHIMIZU Koichi, KATO Yuji, YAMAMOTO Katsuyuki
    レーザー学会研究会報告 = Reports on the Topical meeting of the Laser Society of Japan  1996/07
  • SUZUMURA Masato, WANG You, KATO Yuji, HONGO Akihito, MIYAGI Mitsunobu
    レーザー学会研究会報告 = Reports on the Topical meeting of the Laser Society of Japan  1996/07
  • Takaya J, Kitama M, Kato Y, Shimizu K, Yamamoto K, Kaneko M
    IEICE technical report. ME and bio cybernetics  1996/03 
    A fundamental study has been conducted on the applicability of low-coherence interferometry to the functional CT imaging of biological tissues with light. First, we examined the effectiveness of the proposed technique to suppress the scattering component in the transmitted light. Then, it was shown that we could estimate the absorption coefficient of a scattering medium even in the strong scattering like in a living tissue. Finally, this technique was applied to a rat blood. Using two different wavelengths of light, we could detect the local change in the redox state of the blood.
  • Kubota Satoshi, Kato Yuji, Akama Yosuke, Miyagi Mitsunobu
    Proceedings of the IEICE General Conference  1996/03 
    赤外域に発振波長を持つ高出力レーザ光の伝送路として、石英キャピラリーチューブ内に銀層並びに有機樹脂薄膜を有する、誘電体内装中空導波路が提案されている。銀層の成膜には簡便な銀鏡反応が用いられているが、銀中空導波路の特性は誘電体内装後の伝送路の特性に大きな影響を及ぼす。本報告では、光学特性の測定及びSEMによる銀中空導波路の内面観察から、銀中空導波路製作の最適条件について報告する。
  • SUZUMURA Masato, KATO Yuji, SHIMOMURA Takehiro, MIYAGI Mitsunobu
    レーザー学会学術講演会年次大会講演予稿集 = Annual meeting, of the Laser Society of Japan digest of technical papers  1996/01
  • WANG You, KATO Yuji, SHIMOMURA Takehiro, MIYAGI Mitsunobu
    レーザー学会学術講演会年次大会講演予稿集 = Annual meeting, of the Laser Society of Japan digest of technical papers  1996/01
  • KATO Yuji, MIYAGI Mitsunobu
    レーザー学会研究会報告 = Reports on the Topical meeting of the Laser Society of Japan  1995/08
  • Osawa M, Kato Y, Miyagi M, Abe S, Aizawa M, Onodera S
    Proceedings of the IEICE General Conference  1995/03 
    Er:YAGレーザ等の高出力赤外レーザ光は医療分野、工業加工分野においての応用が盛んに進められている。それらレーザ光をフシキシブルかつ高効率に伝送する装置として誘電体内装中空導波路が研究されており、筆者らはガラスキャピラリーチューブ内面に銀鏡反応及び弗素樹脂(FCP)のDip-coatingによりFCP内装銀中空ガラス導波路(FCP/Ag導波路)を製作している。本論文において、銀鏡反応による銀チューブ製作の再現性の向上及び低損失化、また製作したFCP/Ag導波路の損失波長特性、及びEr.YAGレーザ光伝送特性について報告する。
  • KATO Y, OSAWA M, KUBOTA S, MIYAGI M, ABE S, AIZAWA M, ONODERA S
    レーザー学会学術講演会年次大会講演予稿集 = Annual meeting, of the Laser Society of Japan digest of technical papers  1995/01
  • Kato Yuji, Ohsawa Mitsuo, Miyagi Mitsunobu, Aizawa Masaru, Abe Shin-ichi, Onodera Shinji
    Technical report of IEICE. OCS  1994/11 
    Polyimide-polymer coated silver hollow infrared waveguides with 700 μm inner diameter and 1 m length have been fabricated for the medical applications.By measurements of the loss spectra and loss for the Er:YAG laser light of the wave guides,it is shown that this waveguides have low-loss characteristics.The heat resisting polyimide-polymer has many advantages over other dielectrics such as non-toxicity and durability.Furthermore,by using silica capillary tube as a base tube,this waveguide is shown to be very flexible.

Association Memberships

  • THE JAPAN SOCIETY OF APPLIED PHYSICS   THE INSTITUTE OF ELECTRONICS, INFORMATION AND COMMUNICATION ENGINEERS.   THE LASER SOCIETY OF JAPAN   JAPANESE SOCIETY FOR MEDICAL AND BIOLOGICAL ENGINEERING   

Research Projects

  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2023/04 -2026/03 
    Author : 加藤 祐次, 清水 孝一, 松村 健太, 橋本 守
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2022/06 -2025/03 
    Author : 橋本 守, 工藤 信樹, 加藤 祐次
  • 日本学術振興会：科学研究費助成事業 基盤研究(C)
    Date (from‐to) : 2021/04 -2024/03 
    Author : 北間 正崇, 清水 孝一, 加藤 祐次
     
    慢性腎不全患者が人工透析を行う際に造設する内シャントの血管異常（狭窄，閉塞）を早期に診断・治療することは，患者QOLの点から重要である．透析患者の狭窄原因として症例の多い血管壁の石灰化状態を無侵襲で体外からイメージングできれば，早期診断の一助となる．本研究では，従前に研究・開発してきた非侵襲内シャント光イメージング技術を応用することで血管石灰化状態のイメージング手法の確立を目指す．今年度は，前年度に検討・評価を行った最適波長光源と検出系を用いてイメージングに焦点を絞り，以下の実験的検証を行った． １．計測の定量性を評価するために，血管壁全体が均等に石灰化する狭窄状態を模擬した前腕部ファントムを作製した．前腕部ファントムの基本構造は従前の研究で確立しており，新たにリン酸カルシウムを基材とした石灰化狭窄部を組み込んだ．作製したファントムの構造評価にはX線透視装置を利用した． ２．前年度に構築した2次元分布計測システムを拡張し，波長810 nmと1,208 nmの複数光源での撮影を可能とするシステムを構築した．このシステムを用いて，前述の前腕部ファントムにおける模擬石灰化病変の描出を目指した．その結果，波長810 nmでは，血管壁部と血液部は鮮明に描出されるものの，石灰化部は透過性が高く描出されないことが示唆された．また，波長1,208 nmでは，石灰化部は高コントラストで描出されたものの，正常血管壁や血液部のコントラストが低いことが再確認された．これらの結果から，両波長での透視像を統合することにより，石灰化部，血液部の分離描出が可能となり，限定条件下ではあるが狭窄部外径が最大誤差率2.8％の精度で検出可能なことが明らかとなった．
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Challenging Research (Pioneering)
    Date (from‐to) : 2020/07 -2023/03 
    Author : 清水 孝一, 加藤 祐次, 北間 正崇, 任田 崇吾, 犬島 浩
     
    本研究は、位相共役波による時間反転という新原理を散乱分光の分野に新たに導入することにより、これまで実現が困難であった強い散乱体内部における局所領域分光計測技術の開発を目的とする。第三年度の研究実績は次のとおりである。 １．これまでの理論解析の結果をもとに、着想を具現化するための計測方法、計測条件、計測範囲等につき解析をさらに進め、問題点を明確化した。具体的には、生体のような濃厚系散乱体内部の光伝搬につき、次のように詳しい解析を行った。(1)均一散乱体に対しては、光エネルギーの輸送方程式に基づき、拡散近似解を適用して解析を行った。より具体的システムに対し、実測において必要とされる入射光量を明らかにするとともに、変調周波数、検出感度、計測系のＳＮ比、計測可能深さ等に関する問題点を特定した。 (2)血管や筋肉層など不均一な対象に検討を進め、モンテカルロ法に基づくシミュレーションにより、計測条件の特定を行った。 ２．初年度に独自に考案したイノベーション、つまり超音波変調周波数を時間に対し掃引するチャープ方式を実用化に近づけた。具体的には、 (1) 原理解析をさらに進め、チャープ方式を組み込んだシステムの働きを、より実用レベルでシミュレーションできるようにした。その結果、(2)生体組織のような濃厚系散乱体内部において、光計測領域を局所化する性能の向上が図られた。 ３．体内血管のモデルを構築し、位相共役波による時間反転イメージングを行った。超音波変調の部分に対し、従来法と新規チャープ方式を適用し、有意な空間分解能の向上を確認した。これに伴い、チャープ方式の利点ならびに問題点を明らかにした。 ４．これらの成果を国際会議や国内学会で発表した。2022年度は、8回の国際会議においてのべ10件の研究発表（Plenary1件、Keynote3件、学生受賞1件）を行った。
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)
    Date (from‐to) : 2020/04 -2023/03 
    Author : 加藤 祐次, 清水 孝一, 橋本 守, 松村 健太
     
    本研究の大きな目標である血中中性脂肪濃度の無侵襲光学計測の実現のため、計測手法は生体透過性の高い可視から近赤外の波長領域での後方散乱光の空間分解計測を基礎としている。前年度まで、計測対象の一つとしている前腕部静脈の数値モデルに対するモンテカルロ・シミュレーションにより、静脈の形状・位置に対して光源と検出器の距離を調整する必要性が分かったため、センサー配置の最適化について検討した。また、推定アルゴリズム精度のさらなる向上のため、静脈が走行していない箇所での周囲媒質のみの光学特性推定を組み合わせて、個人差や計測箇所による変動を抑えたロバスト性の向上を進めた。さらに、メディカルフォトニクス社の協力により試作機を用いて、これまで準備してきた実験ファントムを用いて実測し、シミュレーションや光拡散理論と比較検討を行った。その結果シミュレーションで検討してきた推定アルゴリズムに対して修正指針を得た。 一方、毛細血管を対象とした光電式脈波計測法の応用について、スマートフォンアプリおよび多色のLEDとPDからなる計測モジュールを用い、前年度までの検討を踏まえて接触圧力をコントロールしつつ、脂肪食摂取前後の光電脈派信号の変化について評価した。その結果、現状では脂質濃度変化に対する光電脈波信号の変化は見出すことはできなかった。今後、脈波信号の解析について単純な信号強度の変化のみではなく、周波数解析等による解析を要することが課題となった。さらに、ハードウェア面で通常の光電脈波計測のみならず、干渉法に基づくスペックル計測法の適用等の計測法の拡張についても今後の課題とし、基礎実験データを得た。
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2018/04 -2021/03 
    Author : 松村 健太, 山越 健弘, 加藤 祐次, 任田 崇吾
     
    開発中の測定装置については、安静状態であれば安定して計測を行える段階まで作成が進んだ。具体的には、光電式容積脈波の測定回路をブレッドボード上に構築し、これにチップLED(発光ダイオード)とPD(フォトダイオード)を組み合わせた自作センサーを接続した。そして、センサーLEDのチョッピング制御を行う基板上のマイクロコンピューター(mbed)と、シリアルポートを介してこれを制御するパソコン(Apple Mac)双方の自作ソフトウェアーに更なる改良を施した。これにより、反射型の青色、緑色、赤色、近赤外光脈波と、透過型の赤色、近赤外光脈波の、計6種類の脈波が同時測定可能となった。 以上の装置を用いて予備実験を実施した。その結果、安静状態においてデータが安定して取れていることが確認された。一方で、激しい体動を加えると、理由不明のノイズが入り測定できなくなることも確認された。多角的にこの現象を検証した結果、(1) 激しい体動によって脈波センサーの固定状態が著しく悪くなる場合があること、(2) 腕に固定したコードがセンサーを引っ張ることでセンサー回路がショートしているらしいこと、が分かった。これより、引き続きセンサー部の改良、特に、センサー部分のプリント基板化が必須であることが分かった。 一貫したデータ処理を行うため、データ解析専用ソフトウェアーを開発した。これにより、高速フーリエ変換、区間平均処理、信号ノイズ(SN)比の算出、心拍数の計算、体動アーチファクトの周期と振幅の算出、といった一連の解析を効率良く行うことが可能となった。このソフトを用いて、これまでに測定したデータのSN比を解析した結果、反射型の青色、緑色、近赤外光脈波において、高い体動アーチファクト耐性が示されていることが明らかとなった。
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Challenging Research (Exploratory)
    Date (from‐to) : 2018/06 -2020/03 
    Author : Koichi Shimizu
     
    For noninvasive spectral analysis in a human body, we attempted the development of a localized absorption measurement technique in a turbid medium by introducing a new time-reversal principle using a phase-conjugate light. The following accomplishments were achieved, and clear imaging of internal structure in a turbid medium became possible. (1) A new technique to generate phase-conjugate light with intensity modulation was devised. (2) An experimental system for the time-reversal phenomenon was developed and improved. (3) The scattering suppression ability of the proposed technique was evaluated. (4) The independence of the scattering suppression on the light absorption in the medium was confirmed. (5) The system performance was improved by increasing the coherent length of light source. (6) The applicability of the proposed technique to animal tissue was verified.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
    Date (from‐to) : 2017/04 -2020/03 
    Author : Shimizu Koichi
     
    To realize 3D transillumination imaging of internal body structure and physiological function, we integrated our principles to establish a new technique, and developed a test system. Through this study, we achieved the following results. (1) An inverse scattering problem was solved to obtain internal structure in a turbid medium using scattered light from the medium. (2) Blurred transillumination image could be improved by the deconvolution with a point spread function. (3) The problem of image blur was resolved using the convolutional neural network obtained by deep learning. (4) The feasibility of 3D transillumination imaging was confirmed using a tissue-simulated model phantom. (5) A test system was designed and manufactured. (6) The feasibility of functional imaging was confirmed in the identification of vein and artery in a transillumination image. (7) 3D functional transillumination imaging was achieved in animal experiments.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
    Date (from‐to) : 2017/04 -2020/03 
    Author : Hashimoto Mamoru
     
    By reducing the noise of observation data and improvement of observation time using deep learning, we succeeded in the imaging rate improvement of 1.6–1.2 image/min. to 12.5-4.0 image/min. In tissue classification by machine learning of nonlinear Raman scattering images, pre-training with fluorescence images significantly improved the segmentation ability. Besides, we have developed a new microscope for acquiring a large number of hyperspectral nonlinear Raman scattering images and succeeded in increasing the speed 14 times and reducing the excitation light peak irradiance 1/12 compared to the conventional method. It was shown that hyperspectral images of cultured cells were classified by deep learning, and that unsupervised learning could classify cells with different culture conditions.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
    Date (from‐to) : 2017/04 -2020/03 
    Author : Yamaguchi Taihiko
     
    With the aim of establishing diagnostic criteria for diurnal awake bruxism (d-AB), we performed electromyography with an ultraminiature wearable electromyographic device in collaboration with multiple facilities. As a result, we were able to construct a database of daily daytime masseter muscle activity without restraint and various clinical findings in more than 150 subjects. The distribution of the number and magnitude of muscle activity was wide in both the d-AB conscious group and the d-AB non-conscious group, and the overlap between the two groups was also very large. It was shown that it was difficult to explain the amount and magnitude of daytime masticatory muscle activity only by classification of d-AB based on self-awareness.Therefore, based on the numerical distribution of the newly established database, a method of grading masticatory muscle activity during the day in several stages and using the grading as an index for d-AB evaluation was suggested.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)
    Date (from‐to) : 2017/04 -2020/03 
    Author : Masataka Kitama
     
    We have developed the technique to visualize the structure of inner AV fistula with diffuse light that we have established and also developed the simple non-invasive system for the measurement of inner diameter of the artery, which is the criterion for percutaneous transluminal angioplasty (PTA) as it had traditionally depended on X-ray. We also developed the compact measurement system in order to reduce patients' mental and physical burden. In this system, the feasibility of depicting changes in vascular characteristics and the improvement of spatial resolution have been shown by incorporating light sources with multiple wavelengths for simultaneous measurement. The accuracy of the estimation of vessels inner diameter also improved with machine learning. Therefore, the effectiveness of the proposed system was demonstrated.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Exploratory Research
    Date (from‐to) : 2016/04 -2018/03 
    Author : Shimizu Koichi
     
    We conducted this research to open a new possibility for the localized spectral measurement in a turbid medium by introducing the new time-reversal principle using a phase-conjugate wave. The following accomplishments were achieved. 1. In theoretical analysis, we made the fundamental measurement technique to realize the proposed method clear. 2. Through repeated simulation, we optimized the function of the proposed technique. 3. We developed the measurement system to realize the time-reversal principle using the phase-conjugate light. 4. We confirmed the ability of the developed system using a model phantom of animal tissue. 5. We verified the applicability of the system to an animal body in the experiment with chicken breast meat. 6. The result of this study is published in a prestigious journal, Biomedical Optics Express of the Optical Society of America.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)
    Date (from‐to) : 2015/04 -2018/03 
    Author : UEDA YASUO, TAGUCHI Yuu
     
    We investigated the use of near infrared as a method to capture the part that can not be measured with the intraoral scanner. Instead of soft tissue, we wrapped raw ham around abutment teeth made by melamine resin. Light scattered inside the resin tooth was imaged with an infrared camera installed at a position orthogonal to the incident light axis. The margin shape of the abutment tooth was generated by analyzing the pixel value of the fluoroscopic images. But, the shape that can be generated had a error with respect to the depth direction of the image, which was considerably shifted from the original shape. In order to generate a more accurate shape, it is considered necessary to increase the amount of information, review the intensity of light, direction of irradiation and imaging direction, narrow down the search area in consideration of the shape of the preparation tools.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A)
    Date (from‐to) : 2014/04 -2018/03 
    Author : Yamakoshi Ken-ichi
     
    According to a statement issued by International Diabetes Federation, diabetes population in 2015 runs up to 415 million people and Japan has diabetes powers ranked 9th in the world. In a diabetic patient blood glucose (BGL) measurement, most desirably non-invasive method without blood sampling, is needed to control BGL level. Unfortunately such practical non-invasive method has not yet been developed up to now. We have previously developed a novel non-invasive BGL measurement using a finger called “pulse glucometry” and evaluated its validity on an experimental basis. To realize technical practicability of this method, it is essential to develop a new finger-photoplethysmography (PPG) in a wavelength region with BGL absorption having quite high accuracy and sensitivity as well as convenient use. The present study was carried out focusing especially on this PPG development, aiming a basic establishment towards the world’s first non-invasive BGL measurement device for practical use.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
    Date (from‐to) : 2013/04 -2016/03 
    Author : Shimizu Koichi, KUDO Nobuki, KATO Yuji, KITAMA Masataka
     
    To realize 3D transillumination imaging of macroscopic internal body structure, we integrated our principles to develop a new technique. Through optimization using Monte Carlo simulation, a measurement system was constructed. We analyzed the characteristics of the developed system, and necessary improvements were made. In the animal experiments, the feasibility of imaging the internal body structure with the safe near-infrared light without radio-active exposure was verified. The feasibility of functional imaging such as tissue oxygenation state was also verified.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)
    Date (from‐to) : 2012/04 -2015/03 
    Author : KITAMA Masataka, SHIMIZU Koichi, NAMITA Takeshi, KATO Yuji
     
    We conducted a study to realize the imaging system of the blood vessel in order to detect the abnormality of the blood vessel structure in the arteriovenous fistula for hemodialysis. We have developed the measuring system to observe the arteriovenous structure that is non-invasive and compact utilizing the diffuse light in the body tissue positively based on our previous research on the optical bioinstrumentation. We have developed the image processing algorithm to depict the structure in the blood vessel and verified it with the experiment with the phantom. Moreover we have presented the possibility to depict the changes of the blood vessel property in combination with spectroscopic technology. Herewith, we have shown the validity of our proposed system.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)
    Date (from‐to) : 2011 -2013 
    Author : KATO Yuji, SHIMIZU Koichi
     
    A simple technique was newly developed to estimate the depth and the thickness of a fluorescent object in a turbid medium, such as an animal body. In this technique, we estimate the depth and the thickness using multiple excitation light sources with multiple wavelength. We analyzed the relation between the depth and thickness of a fluorescent object and the intensity ratio of the fluorescent light, and confirmed the validity of this principle. Using this principle, we have successfully estimated both the depth and the thickness of a fluorescent object in a tissue or tissue equivalent phantoms simultaneously. Finaly, using the estimated depth, blurred images have successfully restored by decovolution with a pointspread function. Using the restored images and the estimated depth, we could construct three dimensional image of a fluorescent object in a turbid medium.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Exploratory Research
    Date (from‐to) : 2011 -2012 
    Author : SHIMIZU Koichi, KUDO Nobuki, KATO Yuji, NAMITA Takeshi
     
    We conducted a study to realize the selective spectral analysis at a local area in strong scattering medium, such as biological tissues. In two years study, we have developed a technique to quantitatively measure the optical absorption at a local area in the body. This result opened the new possibility; for the non-invasive transcutaneous measurement of accurate optical absorption; and for the tissue spectral measurement while eliminating the effect of the interstitial tissue. We have reported these results in academic journals and international/domestic conferences, and applied patents.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A)
    Date (from‐to) : 2009 -2012 
    Author : SHIMIZU Koichi, KUDO Nobuki, KATO Yuji, KITAMA Masataka, CHIBA Hitoshi
     
    To realize 3D transillumination imaging of internal structure and function of biological body, we developed new techniques based on original principles and created the systems to verify them. In this study, the feasibility of imaging the internal structure of experimental animals and human limbs using safe near-infrared light without radio-active exposure was verified. The feasibility of functional imaging such as tissue oxygenation state was also verified.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Exploratory Research
    Date (from‐to) : 2008 -2009 
    Author : 清水 孝一, 加藤 祐次, 山下 政司, 北間 正崇
     
    従来、カプセル内視鏡など体内機器との通信には、電波による単純な通信方式が用いられてきた。これに対し本研究は、体内を伝搬する散乱光を積極的に用いた光通信を新たに提案し、その実現可能性を実証することを目的とする。 体内深部からの光信号は、生体組織で散乱され広く拡散していく。体表面に装着した複数の光センサでこの信号をとらえ、体内生理情報を復元する。光散乱を積極的に利用し、体表上いくつかの点に光センサを配置することにより、死角のない常に安定した信号伝送が期待できる。 本年度は、前年度までの検討内容を踏まえ、提案手法の基本をなす体内散乱光による信号伝送実験装置を試作すると共に、それを用いた実験により信号伝送方式の最適化を図った。具体的内容は次のとおりである。 1.生体内・光通信システムを試作した。 2.試作システムを用い、生体モデルファントムと生体において本手法の特性を実験的に解析した。その結果、提案手法の実現可能性が実証された。 3.種々のダイバーシティ方式の比較などを通し、提案手法の最適化を図った。その結果、提案手法の実用における有用性が実証された。 研究成果の発表:国際学術誌(Applied Optics 2件、Optics Express 1件)および国際会議(invited talk 2件を含め4件)において、本研究の成果を報告した。
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
    Date (from‐to) : 2006 -2008 
    Author : SHIMIZU Koichi, SHIMOOKA Toshiyuki, KATO Yuji, KITAMA Masataka, SHIMIZU Chikara
     
    生体の実用的な光透視実現のためには、光散乱の問題の解決が必要である。未知の点の多いsnake photonの特性を調べて生体透視へ応用することをめざし、理論的・実験的研究を行った。その結果、次の成果が得られた。イメージングに必要なsnake photonの特性を明らかにした。Snake photon の効率的な検出法を新たに考案した。実験システムを開発し、生体模擬ファントムおよび生体試料を用いたイメージングを行って、開発手法の有効性および有用性を実証した。
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
    Date (from‐to) : 2003 -2005 
    Author : SHIMIZU Koichi, KATO Yuji, YAMASHITA Masaji, KITAMA Masataka
     
    For transillumination imaging of a biological body by near-infrared light, a technique has been developed to realize the imaging of absorption distribution in diffuse scattering medium. Through this study, the following results were obtained. (1)In theoretical and experimental analyses, it was verified that a detectable amount of snake photons is emitted through the dense medium which could not see through with the conventional technique using ballistic photons. (2)A technique has been developed to detect the snake photon efficiently through the scattering object which corresponds to the mammalian tissue with 10-20 mm thickness. This technique is based on the time-resolved measurement of output pulse shape for ultra-fast light-pulse incidence. (3)A new technique has been developed to apply the above principle to the much simpler continuous wave (CW) measurement using a CW light source. (4)An experimental system was newly developed which consisted of a snake-photon detection device, a model phantom to simulate the optical property of mammalian tissue and an imaging system. (5)The effectiveness of the proposed principle and the usefulness of the developed system were verified in the imaging experiment using the above experimental system. (6)The proposed principle and the developed system were applied to the transcutaneous fluorescent imaging. (7)An analytical solution was obtained to describe the photon propagation in a dense random medium by applying the diffusion approximation to the equation of transfer. Using this solution, a technique to improve the transillumination image through a diffusing medium was newly developed. (8)Through this study, a concrete measure was obtained to realize the transillumination imaging using snake photons as well as clarifying the problems to be solved.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Young Scientists (B)
    Date (from‐to) : 2003 -2004 
    Author : 加藤 祐次
     
    生体のような高濃度散乱体おける深さ方向の光学定数分布を後方散乱光より、超音波変調法及び低コヒーレント光干渉法の機能的な結合による生体断層撮影技術開発を最終目的とする。そこで、当初の2年の研究期間内で本計測法における基礎特性の実験的検討に的を絞り、本年度は以下の事項の研究を行った。 1.吸収分布計測の計測特性の評価 前年度の結果を基に、散乱体に吸収体を均一に付加して実験ファントムを作成し、吸収係数の計測について実験的に評価を行った。更には、吸収分布を不均一の状態での計測を行い検証した。これにより計測システムの基礎技術確立を図られた。 2.本計測手法の波長特性評価システムへの拡張 生体内機能情報をより高度に取得するために、広い波長帯にわたる本手法の適用について検討を進めた。その結果より、より高機能な断層撮影技術への拡張への可能性を検討した。その結果、本手法における広帯域な波長においても本手法の有効性の確認ができた。 3.双超音波振動子による散乱体内部光伝搬経路制限の試み 近赤外光による生体内部吸光度分布計測をめざして、光と超音波の相互作用を利用する新たな手法を提案し、その可能性に関する基礎的検討を行った。提案手法は,散乱体内に2箇所以上の超音波変調領域を設け、それらを結ぶ直線に沿った伝搬光を選択的に検出するものである。
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)
    Date (from‐to) : 2003 -2003 
    Author : 清水 孝一, 田村 守, 加藤 祐次, 山本 克之, 青柳 卓雄, 岡田 英史
     
    光応用技術や近代医療技術のそれぞれのレベルにおいては、わが国は先進諸国中、最高水準にある。しかし生科学における光応用技術の研究や実用化については、欧米諸国に比べ遅れていると言わざるを得ない。とくに、創造的な発想や未来を切り拓く新技術開発の多くは、国外からのものに依存しているのが現状である。これに対し、最近はわが国でも、直接医療応用をめざした光応用技術の研究が盛んになりつつある。また、世界トップレベルの先端的光応用技術を利用できる環境も、徐々にではあるが整いつつある。このような背景に対し本企画調査は、医療における光応用技術の知識体系を充実させるとともに先端的光学技術の医学・医療応用の道を拓くことをめざして、特定領域研究の準備調査を行った。 医療のための光応用技術は、大きく基礎研究技術から臨床応用技術まで、目的別には観察・計測・診断・治療など、実に多岐にわたる。本企画調査では、これらを次の5分野に分けて調査活動を行った。すなわち、(1)光学基礎、(2)光学デバイス・装置、(3)光応用計測、(4)光応用イメージング、(5)光応用治療である。これらのうち(3)の分野については5月に、(5)の分野については7月に、(1),(2),(5)の分野については12月にそれぞれ発表会を行った。また、Optics Japan(日本光学会年次大会)の中で、パネルディスカッション「医療のための先端的光応用技術の今後を考える」(司会:研究代表者,パネリスト:すべて本研究の研究分担者)を開催し、本研究の重要性およびその成果を広く一般に公表した。さらに、わが国におけるこの分野の研究を体系的に総括し、特定領域研究形成に向けた具体的基盤とするため、選抜論文集の刊行を企画した。欧米の選抜論文集(Selected Papers)は多く存在するが、わが国のこの分野の選抜論文集は皆無に近いからである。各分担研究者の調査結果を集約し、取捨選択の後、400ページに及ぶ選抜論文集「医療のための光応用技術」を完成し、発行に至った。 これらの活動を通し、特定領域研究の準備という本研究の主たる目的は達成されたと考える。
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Exploratory Research
    Date (from‐to) : 2001 -2002 
    Author : 清水 孝一, 北間 正崇, 加藤 祐次
     
    生体のような高濃度散乱体にビーム光を入射しコリメート受光系で検出した場合、2種類の透過光が得られる。すなわち一度も散乱を受けずに散乱体を通過した光(ballistic photon)と、前方散乱を繰り返しつつ入射光軸にまつわりつくように散乱体を通過した光(snake photon、以下SP)である。SPの発見により、これまで不可能と考えられてきたいくつかの重要な応用に新たな可能性が開かれる。本研究では、未知の点の多いSPに対し、その基礎的な特性を明らかにするとともに、その生体透視への応用ひいては光CT実現へ向け新たな可能性を拓くことを目的とした。 本研究をとおし以下の成果が得られた。 1.散乱体中の光伝搬に対し、輸送方程式に微小角近似および拡散近似を適用することにより理論的解析を行った。それぞれの場合の出射光の空間的・時間的特性から、SPの伝搬特性を理論的に明らかにした。 2.散乱体内光伝搬のシミュレーションを行い、理論解析の結果の妥当性を検証した。また種々の実験条件に対するSPの特性を求めた。これらのうち実現可能な条件に対し実験システムを構築し、SPの検出可能性を実証するとともに、その特性の一端を実験的に明らかにした。 3.SP検出に向け、いくつかの方法を試みた。それらのうち効率的にSPを検出する方法として、差動原理に基づく手法を新たに開発した。このように検出した成分が近軸散乱成分であることを確かめるため、散乱体内部に挿入したナイフエッジのイメージングを行った。その結果、検出成分が確かにSP成分であることが実験的に検証された。これらの成果は、高濃度散乱体におけるSPの検出可能性および有効な検出法を実証したものとして、国内外ともに初めてのものと考えられる。 以上の研究により、本研究の当初の目的はほぼ達成された。今後この成果をさらに応用発展させていきたい。
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Encouragement of Young Scientists (A)
    Date (from‐to) : 2000 -2001 
    Author : 加藤 祐次
     
    超音波技術等を導入した高性能な光生体計測技術の完成を目的として、局在的に照射された超音波による散乱粒子の振動の評価および振動周辺の光学特性の評価を中心に行った。結果は以下のようにまとめられる。 ・低コヒーレント光干渉法による振動中心と光入出射点間の光学特性検出に関する評価 前年度の結果を踏まえて、超音波の焦点と光の入出射点間を散乱成分を除き光軸上の光学特性を取得する手法を超音波照射と低コヒーレント光干渉法を組み合わせる方法を用いて検討を進めた。従来の低コヒーレント光干渉法で用いられる可干渉距離数10μmの光源では到達深度が小さいため、より可干渉距離の長い光源により到達深度が大きくする必要がある。本研究において、可干渉距離4mm程度のTi:Sapphireレーザを用いることを検討した。その結果、無散乱状態において、従来の光源と同様に変調信号を検出することが可能であることが明らかとなった。 次に、現状において不明である長い可干渉距離の光源を用いた場合における、散乱係数に対する干渉強度の評価を行い、到達深度について検討を行った。その結果、干渉強度自体は可干渉距離4mmでは、数10μmの場合より散乱係数の増加に対して減衰の割合が小さいが明らかとなり、到達深度として可干渉距離4mが有利である可能性が得られた。 以上の結果より、超音波照射と低コヒーレント光干渉法を組み合わせる方法より空間分解能mm程度、到達深度数cm程度の光生体計測法の可能性が見出された。
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
    Date (from‐to) : 2000 -2001 
    Author : SHIMIZU Koichi, YASUDA Kazunori, KATO Yuji, SHIMOOKA Toshiyuki, MATSUDA Seiji, YAMASHITA Masaji
     
    A telemetry technique and a test-system have been developed to realize continuous vital-sign monitoring for the senior citizens living alone and the patient in home care. The following research has been conducted. 1. A ring-type sensor was designed to measure pulse-wave optically without interfering a daily activity of the subject. The telemeter using the ring-type sensor satisfied the practical demands for signal fidelity, transmission range, size, weight and battery life. 2. A technique of two-step telemetry was newly devised to meet the antagonizing requirements for low constraint and wide coverage-area at the same time. 3. Using a PHS terminal, an ultra-wide area telemonitoring system has been developed to realize the above technique. 4. Using the developed system, the practicality and the usefulness of the proposed technique was tested in normal and unfavorable environmental conditions. Through this study, the following results were obtained. A vital-sign can be continuously monitored almost unconsciously. Usually the range of telemonitoring had been confined in a home. With this technique, the range has been expanded to the extent of almost all the domestic areas. A practical technique has been developed to monitor a vital-sign using a wearable common terminal both inside and outside the home. In the home, the cellular phone terminal serves as a cordless phone and no network charge is required. Through the experiments, the feasibility of the proposed technique and the practical usefulness of the developed system were verified.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B).
    Date (from‐to) : 1998 -2000 
    Author : SHIMOOKA Toshiyuki, KATO Yuji, YAMAMOTO Katsuyuki, SHIMIZU Koichi, FUKUSHIMA Kikuro
     
    With a view toward the realization of an optical CT, this study was conducted to develop an advanced measurement technique to obtain physiological information using multi wavelength and ultra-short pulse of light. Through this study, the following results were obtained. 1) A principle to suppress the strong scattering in biological tissue was developed. With this principle, we can detect a weak near-axis scattered component of light which is usually buried in a strong scattered component. 2) A time-resolved measurement technique with an ultra-short pulse was applied to the detection of the near-axis scattered light. A technique to obtain the integral of absorption along the optical axis of the incident beam of light was developed. 3) An experimental system was developed to use the above technique. In the experiment with this system, the absorption distribution in a scattering medium was obtained. With this technique, the spatial resolution of the reconstructed image was improved significantly. In addition, the quantitative measurement of absorption distribution became possible, which had been difficult without this technique. 4) A principle of cross-sectional imaging using backscattered light was newly developed for the body part in which transmitted light could not be detected. To utilize this principle, a measurement technique was developed. In a simulation study, the effectiveness and the property of this technique were clarified. 5) An experimental system was developed to use this technique. The absorption distribution in a model phantom of biological tissue was reconstructed. As a result, the reconstructed image agreed well qualitatively with the given distribution. However, further improvement was required for the quantitative measurement. It was also found that the effect of measurement error was not negligible. A new reconstruction algorithm was developed to overcome these problems by the use of multi-wavelength and ultra-short pulse of light. In the simulation and experiment, the effectiveness of this new technique was verified.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
    Date (from‐to) : 1998 -1999 
    Author : SHIMOOKA Toshiyuki, FUKUSHIMA Kikuro, KATO Yuji, SHIMIZU Koichi, YAMASHITA Masaji
     
    The first aim of this study is to establish the methods for the analysis and the evaluation of the electric field exposure to a human body. The second aim is to clarify the biological effect of electric field quantitatively using biotelemetry techniques. This study included the development of numerical analysis techniques and measurement techniques, the measurement of exposure dose in a living human body and the search for the biological effects that can be evaluated quantitatively. Through this study, the following results were obtained. 1) We have developed a numerical analysis technique and a measurement technique of an electric field, which are applicable to a living human body. The distribution of the electric field and the induced current could be measured successfully over all parts of a human body. 2) Using the techniques developed in the study, the electric field and the induced current were measured in the human body when it was exposed to the electric field in the instrument of an electric field therapy. 3) We could obtain the distribution of the surface electric field and the induced current with a living human body. The results revealed the manners of the field concentration on specific parts of the body. It also revealed that the density of the induced current became high (hot spots) at some parts of the body. 4) Through the quantitative analysis of this study, a part of the mechanism of the field perception and the cause of the individual difference in the perception level were made clear. 5) As a physiological change caused by the electric field exposure, the phenomenon of blood flow change in a human body surface was newly discovered. In conclusion, the most part of the purpose of this study was accomplished, and some significant new findings were obtained.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Encouragement of Young Scientists (A)
    Date (from‐to) : 1997 -1998 
    Author : 加藤 祐次
     
    近年、光による生体計測の研究が盛んに行なわれているが、生体組織は強い散乱性を有し光計測の発展に大きな妨げとなっている。そのため本研究では、従来の光のみによる計測に対して、音響光学効果を用いて媒質の局所的な特性を変化させることによる光生体計測の計測能力向上を目指し、より高機能な計測手法を開発することを最終目的とした。この目的のため、本研究期間において光散乱体における音響光学効果について2つの視点から検討を行った。得られた研究成果は、以下に示す通りである。 1. 音響光学効果に伴う屈折率の変化による局所反射光検出 媒質に超音波を照射すると媒質中の屈折率は正弦的に変化するため、局所的な屈折率変化による反射により局所的な光学特性の検出が可能である考えられる。そこで、超音波を照射した媒質に光を入射してOptical Coherence Tomography法を用いて局所的な反射光の検出について検討を行った。その結果、局所的な反射光は確認できなかった。しかしながら要因としてパワー及び周波数が小さいために屈折率変化やその勾配が小さいことか挙げられるため、今後それらの改善により検出の可能性はまだあるものと考えられる。 2. 音響光学効果による後方散乱光の時間分解波形への影響 光散乱媒質に短パルス光を入射し、その後方散乱光の時間分解波形をストリークカメラを用いて、音響光学効果の後方散乱光への影響について評価を行った。その結果、音響光学効果により後方散乱光の時間分解波形に局所的な変化が現れることが明らかとなった。また、それは超音波の位相に応じて変化の様子も異なることが明らかとなった。 以上の結果より、光生体計測に領域において利用価値の高い後方散乱光の時間分解波形に、局所的に能動的な変化を与えることが可能となった。そのため、従来の光のみの計測に対し、本手法はより空間的に高分解能計測の可能性を有することが明らかとなった。
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Exploratory Research
    Date (from‐to) : 1997 -1998 
    Author : 清水 孝一, 北間 正崇, 加藤 祐次
     
    未だ未知の点の多いsnake photonに対し、その基礎的な特性を明らかにすること、またその生体透視への応用ひいては光CT実現へ向けたbreakthroughの可能性を拓くことをめざし、次の研究を行った。 1.高濃度散乱体におけるsnake photonの理論的解析 モンテカルロシミュレーションにより、snake photonのふるまいを調べた。 2.生体に近い散乱体溶液を用いたsnake photonの実験的解析 試料には、散乱吸収特性が既知で、生体組織の光学パラメータとの関係が明らかなIntralipid水溶液を用いた。高出力レーザ、高感度受光器、分光系を中心とする実験システムを設計・製作し、snake photonの特性を実験的に解析した。 これらの結果、次の成果が得られた。 1.生体組織のような高濃度散乱体を透過した光の中にsnake photonが、既存技術で十分検出可能なレベル含まれることが明らかとなった。 2.snake photonの時間分割解析を行ったところ、一般的なtime-gating法による散乱抑制で用いられる時間範囲を超えた部分にも、無視できぬ量のsnake photonが存在していることが見出された。 これらの結果は、snake photonを有効に分離抽出することができれば、生体の光透視イメージングにおける新たな散乱抑制法が得られる可能性を示唆するものと考えられる。
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
    Date (from‐to) : 1996 -1997 
    Author : SHIMIZU Koichi, FUKUSHIMA Kikuro, KUDO Nobuki, KAYTO Yuji, YAMAMOTO Katsuyuki
     
    A fundamental study was conduced to realize the transilumination and the CT imaging of biological functions using multi-wavelength and ultra-short light pulse. Through this research the following progresses were made. (1) Through theoretical and experimental study, it was shown that we can get the image of functional change occurred inside an animal body using the light of multiple wavelengths in near-infrared region. The imaging can be perfomed noninvasively with a relatively simple apparatus. (2) A transilumination imaging system was developed based on the proposed principle. Using this system, the imaging of brain functions was attempted using small experimental animals. As a result, we could succeeded in imaging the transmission change localized in the rat brain when a somatosensory stimulation was applied. It was confirmed that the change appeared in symmetrical positions of left and right cerebral hemispheres at the contra-lateral side of the stimulated limbs. This result seems to be the first case which verified the feasibility of transilumination imaging of the cerebral functions. (3) An optical CT system was developed, and the functional imaging in the crosssectional image was attempted. Using this system, we could detect the oxygenation change of the kidney in the CT image of the mouse abdomen. (4) An experimental system of an ultra-short light pulse was constructed with a femto-second laser and a streak camera. This enabled us to analyze a time-resolved light pulse from a svattering medium. (5) A reconstruction technique was newly developed to obtain crosssectional image of highly scattering medium using backscattered light. In computer simulations and phantom experiments, the effectiveness of this technique was confirmed. (6) The scattered component in transmitted light was investigated in the time-resolved analysis of an ultra-short light pulse. The behavior and prepertes of a snake photon or near-axis scattered light which propagates along the optical axis of the incident beam of light were clarified. Based on this result, the possibility was found to suppress the scattering effect much more effective than the conventional time-gating method.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
    Date (from‐to) : 1996 -1997 
    Author : SHIMIZU Koichi, MIKAMI Tomohisa, YAMASHITA Masaji, HATSUDA Takeshi, KATO Yuji
     
    For advanced emergency medicine, a multi-channel data transmission system was developed. This system can send the color image, audio signal and biosignals of a patient such as electrocardiograms and blood pressures form moving ambulance to an emergency room of a hospital. With this system, the medical doctor in a hospital can understand the condition of the patient in an ambulance and can give instructions of treatment to a paramedic staff in the ambulance. They can start the advanced treatments in the ambulance which have been legally prohibited without the instruction of a licensed medical doctor. The process and the results of this resarch are as follows. (1) The technical difficulties and problems were identified to transmit many kinds of information through a common narrow-band communication network which has been designed mainly for vocal communications. The techniques to overcome these problems were developed. (2) An experimental system was developed. It consists of a mobile station to be mounted in an ambulance and a fixed station in an emergency room in a hospital. They were connected by a mobile communication network. (3) The mobile station was equipped in a car and transmission experiment was conducted from a moving car. There was no problem found in the transmission from the moving car in a regular running condition. (4) To examine the effects of terrain, high buildings and bad weather, the transmission experiments were repeated in conceivable adverse conditions. The quality of transmitted data was deteriorated to some extent. However, it was confirmed that the signal quality was still satisfactory for practical use in emergency medicine. (5) The feasibility was investigated to extend this technique to cover much wider global area using movile satellite communication. It was shown that the wide-area emergency care was feasible by solving the problem of transmission delay due to satellite communication link. Through the experiment using the satellite communication, this feasibility was verified. (6) The developed system was equipped on an operating ambulance of Sapporo Fire Department, and the practical usefulness of this technique was examined. As a result, the satisfactory evaluation was given by a medical doctor specialized in an emergency medicine.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A)
    Date (from‐to) : 1995 -1997 
    Author : MIYAGI Mitsunobu, HONGO Akihito, KATO Yuji, HARA Hiroaki, MATSUURA Yuji
     
    The purpose of this research is development of optical delivery systems for dentistry which enables painless dental treatment. The system utilizes Er : YAG laser as the light source and hollow waveguides as the beam delivery medium. In this research, in addition to flexible waveguides, fixedbent waveguides, visible light delivery systems, and beam launching couplers are studied for development of total laser systems. The hollow waveguides that is the basis of this research deliver high-powered, infrared laser light and the waveguides are robust and stable for long term. The following is the main result of this research : 1.Loss reduction of hollow glass waveguides for Er : YAG laser light Hollow glass waveguides are fabricated by a liquid-phase deposition technique using mirror plating method and polymer liquid coating method. The waveguides consist of a silica capillary tube, a silver layr on the inside of the tube, and a polyimide thin film on the further inside of the silver layr. The waveguides withstand more tna 100mJ of input energy and also has a low transmission loss less than 0.3dB/m. 2.Development of additional devices fro hollow wveguides A lensed-taper, launching coupler for hollow waveguides is newly proposed and developed. The coupler enhance the coupling between the input laser beam and the hollow waveguides. In addition, a beam homogenizer for hollow waveguides is develped by utilizing a silver-halide, infrared fiber. 3.Biological test of the beam delivery system for Er : YAG laser Under the corroboration with a manufacturer of dental systems, biological tests using a polyimidecoated, hollow glass waveguide were performed and obtained a good result of painless treatment.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research on Priority Areas
    Date (from‐to) : 1996 -1996 
    Author : 清水 孝一, 清水 久恵, 福島 菊郎, 加藤 祐次
     
    近年,高圧送電線・各種の高出力電気機器など強力な電磁源が日常空間に現れ,我々は人類史上未経験の人工電磁環境にさらされている.各国でそれぞれ個別の安全基準が暫定的に設けられてはいるが,国によりその値が大きく異なっているのが現状である.その原因としては,生物学的および工学的根拠に基づく客観的評価法の欠如によるところが大きい. 我々はこれまでの研究をとおし,人体のような複雑な構造に対する電磁界ならびに空間イオン流の曝露量の解析・評価法を確立してきた.またこれまでの動物実験の結果をもとに,電界感知閾値を指標としてヒトにおける影響を定量評価することを考えた.今年度はこれをさらに進め,交直両電界の生体影響の違いについて詳しい解析を行うとともに,電界感知に伴う生理的変化について調べた. まず,人工電磁環境の生体影響の定量解析をめざし,独自に開発した体表刺激反応計測法を用いてヒトに対する電界曝露実験を行った.その結果電界の生体作用の変化を,感知閾値の変化として定量化することができた.またこの定量解析をとおし,電界感知の主因である体表刺激作用が主として体毛の動きによって生ずること,その刺激作用が交流と直流で異なること,またその違いは相対湿度による閾値変化に比べると小さいことなどが明らかとなった.さらに曝露実験をとおし,感知閾値レベルの電界による体表刺激でも,人体に生理的変化をもたらす可能性を示唆する結果を得た.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for international Scientific Research
    Date (from‐to) : 1995 -1996 
    Author : MIYAGI Mitsunobu, SU D, CROITORU N, HARA Hiroaki, MATSUURA Yuji, BABA Kazutaka, BAKER H.J, HALL D.R, HARRINGTON J.A, KATZIR A
     
    There has been increasing interest in minimal invasive medicine that is a new type of treatment and diagnosis technique making no large damage or pain to human body. Biomedical optics is a main research area of the minimal invasive medicine and various lasers have been developed for medical applications. For high performance of the medical laser system, an efficient beam delivery equipment is necessary. A purpose of this project is to develop a highly efficient, laser delivery system equipped with a hollow waveguide as a flexible delivery medium. Main results achieved this term are as follows : 1) Held international conferences on biomedical optics BiOS Europe '96 : September '96 (Vienna, Austria) BiOS '97 : February '97 (San Jose, USA) GCL/HPL '96 : August '96 (Edinburgh, UK) 2) Development of extremely-low-loss hollow fiber and efficient fabrication process Hollow waveguides with multiple dielectric layrs were fabricated to obtain an extremely low-loss hollow fibers. Basic experiments to choose an appropriate dielectric material was performed and the result showed that polymers, such as polyimide and fluorocarbon, and inorganic materials, for example, zinc sulfide, germanium, silver iodide, were chosen as suitable materials for low-loss hollow fibers. As for development of highly efficient fabrication process, we developed an all liquid-phase deposition method. In this method, coating of dielectric as well as metal layr is performed by using a liquid-flow-and-dry method. For this method, we also found that polymer films are appropriate dielectric material. 3) Development of optical attachment for hollow waveguides Optical attachments for a high-performance, laser delivery system were developed. For input end of hollow waveguides, we proposed a lensed-taper launching coupler for high efficient coupling between incident laser beam and hollow waveguides. This coupler also prevent a guide's end from a damage due to miscoupling. For output end, we developed a fixed-bent, hollow fiber piece and a beam homogenizer for easy handling of total delivery system.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A)
    Date (from‐to) : 1994 -1996 
    Author : MIYAGI Mitsunobu, KATO Yuji, HORIGUCHI Tsuyoshi, ONODERA Shinji, MATSUURA Yuji
     
    We have investigated transmission devices of infrared laser light for minimally invasive medicine. The results obtained under the project are summarized as follows : 1.Development of zinc sulfide-coated silver hollow nickel waveguide Based on sputtering, electroplating, and etching techniques, we have successfully fabricated zinc sulfide-coated silver hollow nickel waveguides with small losses. THe waveguides are durable and can transmit Er : YAG laser light with the energy of 1.6 J,which suggests the necessity of developing an efficient fabrication method of dielectric-coated hollow waveguides. 2.Fabrication method of polymer-coated silver hollow waveguides In order to fabricate long hollow waveguides efficiently, a new fabrication method based on all liquid phase method has been developed and polyimide or fluorocarbon polymer-coated silver hollow glass waveguides have been obtained for practical dental applications. 3.Proposal of "Total Delivery System" and design of optical elements A new idea of total delivery system has been introduced which uses hollow waveguides and several optical devices such as input launching coupler and and output optical elements are fabricated. The input launching coupler is consisting of a lens and tapered hollow waveguides which has large tolerance in optical misalignment of input beam.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Encouragement of Young Scientists (A)
    Date (from‐to) : 1995 -1995 
    Author : 加藤 祐次
     
    光薄膜の多重共鳴吸収を用いた超細径中空ファイバー型光センサーの開発を目的として、中空導波路の製造プロセスの改善、更に理論的な検討によるセンシングデバイスとしての有効性を検討した。結果は以下のようにまとめられる。 1.超細径伝送路の製作技術の確立 赤外領域で重要とされるEr:YAG、CO_2レーザ光用の高性能な伝送路の実現のため、内径540〜700μm、長さ1m程度のポリイミド及びフッ素樹脂内装銀中空導波路の製作手法を確立することを目的として、製作条件の改善を中心に検討を行った。基本的には、母材パイプに内面精度が高くフレキシブルな石英キャピラリーチューブを用いて、内面に銀及び高分子層を成膜する工程である。このプロセスの中で、銀層成膜時における銀鏡反応条件およびポリイミド層成膜時における乾燥条件について詳細な検討およびプロセス改善を行った結果、光学特性の観点から導波路の安定した製作が可能となり、またプロセスの改善に伴う低損失化も図ることができた。更に、従来まで2μ以上の中赤外領域での特性評価に加え、可視・近赤外領域における特性評価を行った結果、製作した導波路の内装高分子層の膜厚の均一性が従来のものに比べて非常に向上したことが明らかとなった。 2.中空導波路のセンシングデバイスへの応用のための基礎検討 高分子層内装中空導波路をセンシングデバイスの性能について理論的に基礎検討を行った。測定原理はセンシング媒体と高分子層との相互作用による光の干渉効果の変化であり、この原理では光の絶対量に変化に依存せず安定な手法である。検討事項については、液体の屈折率の濃度依存性や環境温度に対する高分子層の屈折率及び膜厚の変化に依存する光の干渉ピークのシフト量との関係を中心に調査した結果、センシングデバイスの基礎特性として液体の屈折率に対して比較的精度の良いセンシングの可能性が見いだされた。
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Developmental Scientific Research (B)
    Date (from‐to) : 1992 -1994 
    Author : MIYAGI Mitsunobu, HONGO Akihito, ONODERA Shinji, KATO Yuji
     
    In this research project, we tried to realize infrared glass hollow waveguides with ultra-low losses which can transmit the laser light such as Er : YAG,CO,and CO_2 laser light with several wavelengths simultaneously or independently for medical applications. The main results obtained during the research period are as follows : 1.Fabrication of ZnS-coated Ag hollow waveguides by outer deposition technique In order to fabricate dielectric-coated waveguides with a completely circular cross section along the propagation axis, we employed a new mandrel for the outer deposition method. By using a polyimide-coated glass pipe as a mandrel, ZuS-coated Ag hollow waveguides have been fabricated and the maximum energy of 1.6 J of Er : YAG laser light has been successfully transmitted without siginificant degradation of waveguides. This shows that ZuS-coated Ag waveguide can be used for high-energy transmission media and for dental application. 2.Fabrication of polymer-coated Ag hollow glass waveguides by liquid phase method After depositing a this silver layr inside a fused silica tube with an ultra-smooth inner surface by using a silver mirror reaction method, polyimide or fluorocarbon polymer has been deposited by using a liquid flow coating method or dipping method. Thin hollow waveguides with inner diameters of 700 mum and 540 mum have been fabricated for transmitting Er : YAG laser light with small losses. 3.Studies on mode structures of hollow waveguides Based on the exact characteristic equation, mode structures and mode transitions of circular hollow waveguides with and without inner dielectric layr have been fully clarified. Properties of lower order modes in a uniformly bent circular hollow waveguide are also made clear.

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