研究者データベース

平田 拓(ヒラタ ヒロシ)
情報科学研究院 生命人間情報科学部門 バイオエンジニアリング分野
教授

基本情報

所属

  • 情報科学研究院 生命人間情報科学部門 バイオエンジニアリング分野

職名

  • 教授

学位

  • 博士(工学)(東京工業大学)

ホームページURL

科研費研究者番号

  • 60250958

J-Global ID

研究キーワード

  • 電子スピン共鳴   イメージング   生体計測   共振器   電子常磁性共鳴   ニトロキシルラジカル   MRI   画像再構成   マイクロ波共振器   周波数変調   サーフェイス・コイル   自動マッチング制御   磁界変調   共振尖鋭度   磁気共鳴   安定性   高周波磁界発生効率   空洞共振器   スライス選択画像   実験動物   線形制御理論   平衡線路   pH   帰還制御   マイクロ波発振器   マウス   脳   分光   スペクトル   一酸化窒素   

研究分野

  • ものづくり技術(機械・電気電子・化学工学) / 計測工学
  • ライフサイエンス / 放射線科学
  • ライフサイエンス / 薬理学
  • ナノテク・材料 / 結晶工学
  • ナノテク・材料 / 応用物性
  • ライフサイエンス / 薬系分析、物理化学

職歴

  • 2019年04月 - 現在 北海道大学 大学院情報科学研究院 教授
  • 2008年10月 - 2019年03月 北海道大学 大学院情報科学研究科 教授
  • 2015年03月 - 2015年03月 ポーランド共和国 Jagiellonian University Faculty of Biochemistry, Biophysics and Biotechnology Visiting Professor
  • 2007年04月 - 2008年09月 山形大学 大学院理工学研究科 教授
  • 1996年04月 - 2007年03月 山形大学 工学部 助教授
  • 2006年09月 - 2006年09月 アメリカ合衆国 オハイオ州立大学 Davis Heart and Lung Research Institute Visiting Scholar
  • 2003年06月 - 2005年07月 文部科学省 研究振興局 学術調査官(科学研究費補助金担当)
  • 1999年04月 - 2000年03月 アメリカ合衆国 ダートマス大学 EPR Center for the Study of Viable Systems Research Associate
  • 1993年04月 - 1996年03月 山形大学 工学部 助手

学歴

  • 1990年04月 - 1993年03月   東京工業大学   総合理工学研究科   電子システム専攻(博士後期課程)
  • 1988年04月 - 1990年03月   山形大学   工学研究科   電気工学専攻(修士課程)
  • 1984年04月 - 1988年03月   東北工業大学   通信工学科

所属学協会

  • 電子情報通信学会   国際EPR(ESR)学会   国際磁気共鳴医学会   電子スピンサイエンス学会   

研究活動情報

論文

  • Denis A. Komarov, Alexandre Samouilov, Hiroshi Hirata, Jay L. Zweier
    Journal of Magnetic Resonance 329 107024  2021年08月 [査読有り][通常論文]
  • Yasuhiro Nakai, Ichiro Yamaguchi, Hiroshi Hirata, Harold M. Swartz, Ann Barry Flood, Benjamin B. Williams, Wilson Schreiber, Minoru Miyake
    Applied Magnetic Resonance 10.1007/s00723-021-01340-3  2021年07月 [査読有り]
  • Neil J Stewart, Tatsuyuki Sato, Norihiko Takeda, Hiroshi Hirata, Shingo Matsumoto
    Antioxidants & Redox Signaling 10.1089/ars.2021.0139  2021年07月 [査読有り]
  • Neil J. Stewart, Hitomi Nakano, Shuto Sugai, Mitsushi Tomohiro, Yuki Kase, Yoshiki Uchio, Toru Yamaguchi, Yujirou Matsuo, Tatsuya Naganuma, Norihiko Takeda, Ikuya Nishimura, Hiroshi Hirata, Takuya Hashimoto, Shingo Matsumoto
    ChemPhysChem 22 10 915 - 923 2021年05月 [査読有り]
  • Kota Kimura, Nami Iguchi, Hitomi Nakano, Hironobu Yasui, Shingo Matsumoto, Osamu Inanami, Hiroshi Hirata
    Antioxidants & Redox Signaling 10.1089/ars.2021.0003  2021年04月 [査読有り][通常論文]
  • Jong In Park, Kwon Choi, Chang Uk Koo, Jeonghun Oh, Hiroshi Hirata, Harold M. Swartz, Sung-Joon Ye
    Health Physics 120 2 152 - 162 2021年02月 [査読有り][通常論文]
  • Akihiro Taguchi, Stephen DeVience, Benoit Driesschaert, Valery V. Khramtsov, Hiroshi Hirata
    The Analyst 145 9 3236 - 3244 2020年05月 [査読有り]
     

    A simultaneous mapping method was established for the partial pressure of oxygen, pH and inorganic phosphate using electron paramagnetic resonance.

  • Takahito Yokoyama, Akihiro Taguchi, Harue Kubota, Neil J. Stewart, Shingo Matsumoto, Igor A. Kirilyuk, Hiroshi Hirata
    Journal of Magnetic Resonance 305 122 - 130 2019年08月 [査読有り]
  • Ririko Nakaoka, Hiroshi Hirata
    AIP Advances 9 7 075312  2019年07月 [査読有り][通常論文]
  • Denis A Komarov, Yuki Ichikawa, Kumiko Yamamoto, Neil J Stewart, Shingo Matsumoto, Hironobu Yasui, Igor A Kirilyuk, Valery V Khramtsov, Osamu Inanami, Hiroshi Hirata
    Analytical Chemistry 90 23 13938 - 13945 2018年12月 [査読有り][通常論文]
     
    An electron paramagnetic resonance (EPR)-based method for noninvasive three-dimensional extracellular pH mapping was developed using a pH-sensitive nitroxyl radical as an exogenous paramagnetic probe. Fast projection scanning with a constant magnetic field sweep enabled the acquisition of four-dimensional (3D spatial +1D spectral) EPR images within 7.5 min. Three-dimensional maps of pH were reconstructed by processing the pH-dependent spectral information on the images. To demonstrate the proposed method of pH mapping, the progress of extracellular acidosis in tumor-bearing mouse legs was studied. Furthermore, extracellular pH mapping was used to visualize the spatial distribution of acidification in different tumor xenograft mouse models of human-derived pancreatic ductal adenocarcinoma cells. The proposed EPR-based pH mapping method enabled quantitative visualization of regional changes in extracellular pH associated with altered tumor metabolism.
  • Impact of the characteristic impedance of coaxial lines on the sensitivity of a 750-MHz electronically tunable EPR resonator
    R. Nakaoka, D. A. Komarov, S. Matsumoto, H. Hirata
    Applied Magnetic Resonance 49 8 853 - 867 2018年08月 [査読有り][通常論文]
  • Tatsuya Amida, Ririko Nakaoka, Denis A Komarov, Kumiko Yamamoto, Osamu Inanami, Shingo Matsumoto, Hiroshi Hirata
    IEEE Transactions on Biomedical Engineering 65 5 1124 - 1132 2018年05月 [査読有り][通常論文]
     
    OBJECTIVE: The purpose of this work was to develop an electronically tunable resonator operating at 750 MHz for continuous-wave electron paramagnetic resonance (CW-EPR) imaging of a mouse tumor-bearing leg. METHODS: The resonator had a multi-coil parallel-gap structure with a sample space of 16 mm in diameter and 20 mm in length. Microstrip line couplers were used in conjunction with varactor diodes to enable resonance frequency adjustment and to reduce the nonlinear effects of the varactor diodes. The resonator was modeled by the finite-element method and a microwave circuit simulation was performed to clarify its radiofrequency characteristics. RESULTS: A tunable resonator was evaluated in terms of its resonance frequency, tunable frequency band, and conversion efficiency of the RF magnetic field. The developed resonator provided a tunable frequency band of 4 MHz at a central frequency of 747 MHz and a conversion efficiency of 34 μT/W1/2. To demonstrate the application of this tunable resonator to EPR imaging, three-dimensional EPR images of a sample solution and a mouse tumor-bearing leg were obtained. CONCLUSION: The developed tunable resonator satisfied our initial requirements for in vivo EPR imaging and may be able to be further improved using the present finite-element and circuit models if any problems arise during future practical applications. SIGNIFICANCE: This work may help to promote EPR imaging of tumor-bearing mice in cancer-related studies.
  • Hideo Sato-Akaba, Miho C. Emoto, Hiroshi Hirata, Hirotada G. Fujii
    JOURNAL OF MAGNETIC RESONANCE 284 48 - 58 2017年11月 [査読有り][通常論文]
     
    This paper describes the development of a digital console for three-dimensional (3D) continuous wave electron paramagnetic resonance (CW-EPR) imaging of a small animal to improve the signal-to-noise ratio and lower the cost of the EPR imaging system. A RF generation board, an RF acquisition board and a digital signal processing (DSP) & control board were built for the digital EPR detection. Direct sampling of the reflected RF signal from a resonator (approximately 750 MHz), which contains the EPR signal, was carried out using a band-pass subsampling method. A direct automatic control system to reduce the reflection from the resonator was proposed and implemented in the digital EPR detection scheme. All DSP tasks were carried out in field programmable gate array ICs. In vivo 3D imaging of nitroxyl radicals in a mouse's head was successfully performed. (C) 2017 Elsevier Inc. All rights reserved.
  • Michitaka Umakoshi, Ichiro Yamaguchi, Hiroshi Hirata, Naoki Kunugita, Benjamin B. Williams, Harold M. Swartz, Minoru Miyake
    HEALTH PHYSICS 113 4 262 - 270 2017年10月 [査読有り][通常論文]
     
    In vivo L-band electron paramagnetic resonance tooth dosimetry is a newly developed and very promising method for retrospective biodosimetry in individuals who may have been exposed to significant levels of ionizing radiation. The present study aimed to determine the relationships among enamel thickness, enamel area, and measured electron paramagnetic resonance signal amplitude with a view to improve the quantitative accuracy of the dosimetry technique. Ten isolated incisors were irradiated using well-characterized doses, and their radiation-induced electron paramagnetic resonance signals were measured. Following the measurements, the enamel thickness and area of each tooth were measured using micro-focus computed tomography. Linear regression showed that the enamel area at each measurement position significantly affected the radiation-induced electron paramagnetic resonance signal amplitude (p < 0.001). Simulation data agreed well with this result. These results indicate that it is essential to properly consider enamel thickness and area when interpreting electron paramagnetic resonance tooth dosimetry measurements to optimize the accuracy of dose estimation.
  • Denis A. Komarov, Hiroshi Hirata
    JOURNAL OF MAGNETIC RESONANCE 281 44 - 50 2017年08月 [査読有り][通常論文]
     
    In this paper, we introduce a procedure for the reconstruction of spectral-spatial EPR images using projections acquired with the constant sweep of a magnetic field. The application of a constant field-sweep and a predetermined data sampling rate simplifies the requirements for EPR imaging instrumentation and facilitates the backprojection-based reconstruction of spectral-spatial images. The proposed approach was applied to the reconstruction of a four-dimensional numerical phantom and to actual spectral-spatial EPR measurements. Image reconstruction using projections with a constant field sweep was three times faster than the conventional approach with the application of a pseudo-angle and a scan range that depends on the applied field gradient. Spectral-spatial EPR imaging with a constant field-sweep for data acquisition only slightly reduces the signal-to-noise ratio or functional resolution of the resultant images and can be applied together with any common backprojection-based reconstruction algorithm. (C) 2017 Elsevier Inc. All rights reserved.
  • Harue Kubota, Denis A. Komarov, Hironobu Yasui, Shingo Matsumoto, Osamu Inanami, Igor A. Kirilyuk, Valery V. Khramtsov, Hiroshi Hirata
    MAGNETIC RESONANCE MATERIALS IN PHYSICS BIOLOGY AND MEDICINE 30 3 291 - 298 2017年06月 [査読有り][通常論文]
     
    Objectives The aim of this study was to demonstrate the feasibility of in vivo three-dimensional (3D) relaxation time T-2* mapping of a dicarboxy-PROXYL radical using continuous-wave electron paramagnetic resonance (CW-EPR) imaging. Materials and methods Isotopically substituted dicarboxy-PROXYL radicals, 3,4-dicarboxy-2,2,5,5-tetra(H-2(3)) methylpyrrolidin-( 3,4-H-2(2))-(1-N-15)-1-oxyl (H-2, N-15-DCP) and 3,4-dicarboxy-2,2,5,5-tetra(H-2(3)) methylpyrrolidin-(3,4-H-2(2))1- oxyl (H-2-DCP), were used in the study. A clonogenic cell survival assay was performed with the H-2-DCP radical using squamous cell carcinoma (SCC VII) cells. The time course of EPR signal intensities of intravenously injected H-2, N-15-DCP and H-2-DCP radicals were determined in tumor-bearing hind legs of mice (C3H/HeJ, male, n = 5). CW-EPR-based single-point imaging (SPI) was performed for 3D T-2* mapping. Results H-2-DCP radical did not exhibit cytotoxicity at concentrations below 10 mM. The in vivo half-life of H-2, N-15-DCP in tumor tissues was 24.7 +/- 2.9 min (mean +/- standard deviation [SD], n = 5). The in vivo time course of the EPR signal intensity of the H-2, N-15-DCP radical showed a plateau of 10.2 +/- 1.2 min (mean +/- SD) where the EPR signal intensity remained at more than 90% of the maximum intensity. During the plateau, in vivo 3D T-2* maps with H-2, N-15-DCP were obtained from tumor-bearing hind legs, with a total acquisition time of 7.5 min. Conclusion EPR signals of H-2, N-15-DCP persisted long enough after bolus intravenous injection to conduct in vivo 3D T-2* mapping with CW-EPR-based SPI.
  • Minoru Miyake, Yasuhiro Nakai, Ichiro Yamaguchi, Hiroshi Hirata, Naoki Kunugita, Benjamin B. Williams, Harold M. Swartz
    RADIATION PROTECTION DOSIMETRY 172 1-3 248 - 253 2016年12月 [査読有り][通常論文]
     
    The aim of this study was to make direct measurements of the possible radiation-induced EPR signals in the teeth of volunteers who were residents in Fukushima within 80 km distance from the Fukushima Nuclear Power plant at the time of the disaster, and continued to live there for at least 3 month after the disaster. Thirty four volunteers were enrolled in this study. These measurements were made using a portable L-band EPR spectrometer, which was originally developed in the EPR Center at Dartmouth. All measurements were performed using surface loop resonators that have been specifically designed for the upper incisor teeth. Potentially these signals include not only radiation-induced signals induced by the incident but also background signals including those from prior radiation exposure from the environment and medical exposure. We demonstrated that it is feasible to transport the dosimeter to the measurement site and make valid measurements. The intensity of the signals that were obtained was not significantly above those seen in volunteers who had not had potential radiation exposures at Fukushima.
  • Xiaolei Wang, Miho Emoto, Yusuke Miyake, Kaori Itto, Shu Xu, Hirotada Fujii, Hiroshi Hirata, Hirokazu Arimoto
    BIOORGANIC & MEDICINAL CHEMISTRY LETTERS 26 20 4947 - 4949 2016年10月 [査読有り][通常論文]
     
    A novel blood-brain barrier (BBB)-permeable compound 10 was discovered, wherein the nitroxide moiety was linked to a nicotine acetylcholine receptor ligand. It was applied as a probe for electron paramagnetic resonance (EPR) imaging of the mouse brain. The results demonstrated that the newly synthesized compound 10 exhibited BBB permeability. These findings provide an essential discovery for in vivo EPR imaging. (C) 2016 Elsevier Ltd. All rights reserved.
  • Ann Barry Flood, The EPR Center Tooth Dosimetry Project Team, Benjamin B. Williams, Wilson Schreiber, Gaixin Du, Victoria A. Wood, Maciej M. Kmiec, Sergey V. Petryakov, Eugene Demidenko, Harold M. Swartz, Holly K. Boyle, Ruhong Dong, Shireen Geimer, Lesley A. Jarvis, Kyo Kobayashi, Roberto J. Nicolalde, Jason Crist, Ankit Gupta, Timothy Raynolds, Spencer Brugger, Pawel Budzioh, Brandon Carr, Matthew Feldman, Barjor Gimi, Oleg Grinberg, Vladimir Krymov, Piotr Lesniewski, Michael Mariani, Paul M. Meaney, Kevin M. Rychert, Ildar Salikhov, Dmitriy S. Tipikin, Mark Tseytlin, Brian R. Edwards, Christopher D. Herring, Catherine Lindsay, Traci Rosenbaum, Arif Ali, David Carlson, Wojciech Froncisz, Hiroshi Hirata, Jason Sidabras, Steven G. Swarts, Paul Calderone, Jamie Kennedy, Joseph Ianotti, Eric Elder, Barry Sands
    Radiation Protection Dosimetry 172 1-3 72 - 80 2016年 [査読有り][通常論文]
     
    Several important recent advances in the development and evolution of in vivo Tooth Biodosimetry using Electron Paramagnetic Resonance (EPR) allow its performance to meet or exceed the U.S. targeted requirements for accuracy and ease of operation and throughput in a large-scale radiation event. Ergonomically based changes to the magnet, coupled with the development of rotation of the magnet and advanced software to automate collection of data, have made it easier and faster to make a measurement. From start to finish, measurements require a total elapsed time of 5 min, with data acquisition taking place in less than 3 min. At the same time, the accuracy of the data for triage of large populations has improved, as indicated using the metrics of sensitivity, specificity and area under the ROC curve. Applying these standards to the intended population, EPR in vivo Tooth Biodosimetry has approximately the same diagnostic accuracy as the purported 'gold standard' (dicentric chromosome assay). Other improvements include miniaturisation of the spectrometer, leading to the creation of a significantly lighter and more compact prototype that is suitable for transporting for Point of Care (POC) operation and that can be operated off a single standard power outlet. Additional advancements in the resonator, including use of a disposable sensing loop attached to the incisor tooth, have resulted in a biodosimetry method where measurements can be made quickly with a simple 5-step workflow and by people needing only a few minutes of training (which can be built into the instrument as a training video). In sum, recent advancements allow this prototype to meet or exceed the US Federal Government's recommended targets for POC biodosimetry in large-scale events.
  • Ayano Enomoto, Keita Saito, Sankaran Subramanian, Murali C. Krishna, Hiroshi Hirata, Nallathamby Devasahayam
    APPLIED MAGNETIC RESONANCE 46 6 671 - 683 2015年06月 [査読有り][通常論文]
     
    This article describes a four-channel coil array for in vivo time-domain electron paramagnetic resonance (EPR) imaging applications. Decoupling of the individual element coils was achieved with the low-quality factors required in pulsed EPR at radiofrequency to accommodate the imaging bandwidth. No active decoupling method was used in the coil array. Remote control of a coaxial switch connected to the four-channel coil array was performed with voltage signals from a personal computer. To verify the operation of this four-channel coil array, a phantom tube filled with a solution of paramagnetic triarylmethyl radicals (OX063) was visualized by pulsed EPR imaging based on the single-point method involving pure phase encoding. In an in vivo experiment, OX063 in a mouse tumor-bearing right hind leg was visualized by pulsed EPR imaging. Even without active decoupling circuits, there was no shift in resonances for individual coils when those were tuned to the same frequency due to low quality factors and low coupling coefficients with neighboring coils. The coil assembly allowed us to study an object that was larger than an individual coil element, enabling the imaging of larger subjects with reduced overall specific absorption rate. Such strategies should be useful for studying larger objects by EPR imaging.
  • Wataru Takahashi, Yusuke Miyake, Hiroshi Hirata
    JOURNAL OF MAGNETIC RESONANCE 247 10 31 - 37 2014年10月 [査読有り][通常論文]
     
    This article describes an improved method for suppressing image artifacts in the visualization of N-14- and N-15-labeled nitroxyl radicals in a single image scan using electron paramagnetic resonance (EPR). The purpose of this work was to solve the problem of asymmetric EPR absorption spectra in spectral processing. A hybrid function of Gaussian and Lorentzian lineshapes was used to perform spectral line-fitting to successfully separate the two kinds of nitroxyl radicals. This approach can process the asymmetric EPR absorption spectra of the nitroxyl radicals being measured, and can suppress image artifacts due to spectral asymmetry. With this improved visualization method and a 750-MHz continuous-wave EPR imager, a temporal change in the distributions of a two-phase paraffin oil and water/glycerin solution system was visualized using lipophilic and hydrophilic nitroxyl radicals, i.e., 2-(14-carboxytetradecy1)-2-ethyl-4, 4-dimethyl-3-oxazolidinyloxy (16-DOXYL stearic acid) and 4-hydroxyl-2,2,6,6-tetramethylpiperidine-d(17)-1-N-15-1-oxyl (TEMPOL-d(17)-N-15). The results of the two-phase separation experiment verified that reasonable artifact suppression could be achieved by the present method that deals with asymmetric absorption spectra in the EPR imaging of N-14- and N-15-labeled nitroxyl radicals. (C) 2014 Elsevier Inc. All rights reserved.
  • Wataru Takahashi, Andrey A. Bobko, Ilirian Dhimitruka, Hiroshi Hirata, Jay L. Zweier, Alexandre Samouilov, Valery V. Khramtsov
    APPLIED MAGNETIC RESONANCE 45 9 817 - 826 2014年09月 [査読有り][通常論文]
     
    Variable radio frequency proton-electron double-resonance imaging (VRF PEDRI) enables extracting a functional map from a limited number of images acquired at pre-selected EPR frequencies using specifically designed paramagnetic probes with high-quality spatial resolution and short acquisition times. In this work we explored the potential of VRF PEDRI for pH mapping of aqueous samples using recently synthesized pH-sensitive phosphonated trityl radical, pTR. The ratio of Overhauser enhancements measured at each pixel at two different excitation frequencies corresponding to the resonances of protonated and deprotonated forms of pTR probe allows for a pH map extraction. Long relaxation times of pTR allow for pH mapping at EPR irradiation power as low as 1.25 W during 130 s acquisition time with spatial resolution of about 1 mm. This is particularly important for in vivo applications enabling one to avoid sample overheating by reducing RF power deposition.
  • Miho C. Emoto, Hideo Sato-Akaba, Hiroshi Hirata, Hirotada G. Fujii
    FREE RADICAL BIOLOGY AND MEDICINE 74 222 - 228 2014年09月 [査読有り][通常論文]
     
    Electron paramagnetic resonance (EPR) imaging using nitroxides as redox-sensitive probes is a powerful, noninvasive method that can be used under various physiological conditions to visualize changes in redox status that result from oxidative damage. Two blood-brain barrier-permeative nitroxides, 3-hydroxymethy1-2,2,5,5-tetramethylpyrrolidine-1-oxyl (HMP) and 3-methoxycarbony1-2,2,5,5-tetramethy (MCP), have been widely used as redox-sensitive probes in the brains of small animals, but their in vivo distribution and properties have not yet been analyzed in detail. In this study, a custom-made continuous-wave three-dimensional (3D) EPR imager was used to obtain 3D EPR images of mouse heads using MCP or HMP. This EPR imager made it possible to take 3D EPR images reconstructed from data from 181 projections acquired every 60 s. Using this improved EPR imager and magnetic resonance imaging, the distribution and reduction time courses of HMP and MCP were examined in mouse heads. EPR images of living mice revealed that HMP and MCP have different distributions and different time courses for entering the brain. Based on the pharmacokinetics of the reduction reactions of HMP and MCP in the mouse head, the half-lives of HMP and MCP were clearly and accurately mapped pixel by pixel. An ischemic mouse model was prepared, and the half-life of MCP was mapped in the mouse head. Compared to the half-life in control mice, the half-life of MCP in the ischemic model mouse brain was significantly increased, suggesting a shift in the redox balance. This in vivo EPR imaging method using BBB-permeative MCP is a useful noninvasive method for assessing changes in the redox status in mouse brains under oxidative stress. (C) 2014 Elsevier Inc. All rights reserved.
  • Hirotaka Sugawara, Hiroshi Hirata, Sergey Petryakov, Piotr Lesniewski, Benjamin B. Williams, Ann Barry Flood, Harold M. Swartz
    IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING 61 6 1894 - 1901 2014年06月 [査読有り][通常論文]
     
    This paper describes an optimized design of a surface coil resonator for in vivo electron paramagnetic resonance (EPR)-based tooth dosimetry. Using the optimized resonator, dose estimates with the standard error of the mean of approximately 0.5 Gy were achieved with irradiated human teeth. The product of the quality factor and the filling factor of the resonator was computed as an index of relative signal intensity in EPR tooth dosimetry by the use of 3-D electromagnetic wave simulator and radio frequency circuit design environment (ANSYS HFSS and Designer). To verify the simulated results of the signal intensity in our numerical model of the resonator and a tooth sample, we experimentally measured the radiation-induced signals from an irradiated tooth with an optimally designed resonator. In addition to the optimization of the resonator design, we demonstrated the improvement of the stability of EPR spectra by decontamination of the surface coil resonator using an HCl solution, confirming that contamination of small magnetic particles on the silver wire of the surface coil had degraded the stability of the EPR spectral baseline.
  • Jonathan Goodwin, Katsuya Yachi, Masaki Nagane, Hironobu Yasui, Yusuke Miyake, Osamu Inanami, Andrey A. Bobko, Valery V. Khramtsov, Hiroshi Hirata
    NMR IN BIOMEDICINE 27 4 453 - 458 2014年04月 [査読有り][通常論文]
     
    The in vivo quantification of extracellular pH (pH(e)) in tumours may provide a useful biomarker for tumour cell metabolism. In this study, we assessed the viability of continuous-wave electron paramagnetic resonance (CW-EPR) spectroscopy with a pH-sensitive nitroxide for the measurement of extracellular tumour pH in a mouse model. CW-EPR spectroscopy (750 MHz) of C3H HeJ mice hind leg squamous cell tumour was performed after intravenous tail vein injection of pH-sensitive nitroxide (R-SG, 2-(4-((2-(4-amino-4-carboxybutanamido)-3-(carboxymethylamino)-3-oxoproylthio)methyl)phenyl)-4-pyrrolidino-2,5,5-triethyl-2,5-dihydro-1H-imidazol-1-oxyl) during stages of normal tumour growth and in response to a single 10-Gy dose of X-ray irradiation. An inverse relationship was observed between tumour volume and pH(e) value, whereby, during normal tumour growth, a constant reduction in pH(e) was observed. This relationship was disrupted by X-ray irradiation and, from 2-3 days post-exposure, a transitory increase in pH(e) was observed. In this study, we demonstrated the viability of CW-EPR spectroscopy using R-SG nitroxide to obtain high-sensitivity pH measurements in a mouse tumour model with an accuracy of <0.1 pH units. In addition, the measured changes in pH(e) in response to X-ray irradiation suggest that this may offer a useful method for the assessment of the physiological change in response to existing and novel cancer therapies. Copyright (c) 2014 John Wiley & Sons, Ltd.
  • Xiaolei Wang, Miho Emoto, Atsushi Sugimoto, Yusuke Miyake, Kaori Itto, Mitsuo Amasaka, Shu Xu, Hiroshi Hirata, Hirotada Fujii, Hirokazu Arimoto
    TETRAHEDRON LETTERS 55 13 2146 - 2149 2014年03月 [査読有り][通常論文]
     
    A scalable synthetic route for N-15-labeled 4-oxo-2,2,6,6-tetraethylpiperidine nitroxide (N-15-TEEPONE) is described. This N-15-labeled nitroxide is suitable for electron paramagnetic resonance imaging of brain, and its higher sensitivity compared with that of its N-14-counterpart is an important advantage of the labeled derivative. (C) 2014 Elsevier Ltd. All rights reserved.
  • Ayano Enomoto, Hiroshi Hirata, Shingo Matsumoto, Keita Saito, Sankaran Subramanian, Murali C. Krishna, Nallathamby Devasahayam
    MAGNETIC RESONANCE IN MEDICINE 71 2 853 - 858 2014年02月 [査読有り][通常論文]
     
    Time-domain electron paramagnetic resonance imaging is currently a useful preclinical molecular imaging modality in experimental animals such as mice and is capable of quantitatively mapping hypoxia in tumor implants. The microseconds range relaxation times (T-1 and T-2) of paramagnetic tracers and the large bandwidths (tens of MHz) to be excited by electron paramagnetic resonance pulses for spatial encoding makes imaging of large objects a challenging task. The possibility of using multiple array coils to permit studies on large sized object is the purpose of the present work. Toward this end, the use of planar array coils in different configurations to image larger objects than cannot be fully covered by a single resonator element is explored. Multiple circular surface coils, which are arranged in a plane or at suitable angles mimicking a volume resonator, are used in imaging a phantom and a tumor-bearing mouse leg. The image was formed by combining the images collected from the individual coils with suitable scaling. The results support such a possibility. By multiplexing or interleaving the measurements from each element of such array resonators, one can scale up the size of the subject and at the same time reduce the radiofrequency power requirements and increase the sensitivity. Magn Reson Med 71:853-858, 2014. (c) 2013 Wiley Periodicals, Inc.
  • Ayano Enomoto, Hiroshi Hirata
    JOURNAL OF MAGNETIC RESONANCE 239 29 - 33 2014年02月 [査読有り][通常論文]
     
    This article describes a feasibility study of parallel image-acquisition using a two-channel surface coil array in continuous-wave electron paramagnetic resonance (CW-EPR) imaging. Parallel EPR imaging was performed by multiplexing of EPR detection in the frequency domain. The parallel acquisition system consists of two surface coil resonators and radiofrequency (RF) bridges for EPR detection. To demonstrate the feasibility of this method of parallel image-acquisition with a surface coil array, three-dimensional EPR imaging was carried out using a tube phantom. Technical issues in the multiplexing method of EPR detection were also clarified. We found that degradation in the signal-to-noise ratio due to the interference of RF carriers is a key problem to be solved. (C) 2013 Elsevier Inc. All rights reserved.
  • Miho C. Emoto, Hideo Sato-Akaba, Hiroshi Hirata, Hirotada G. Fujii
    FREE RADICAL BIOLOGY AND MEDICINE 65 S45 - S45 2013年11月 [査読有り][通常論文]
  • Ayano Enomoto, Miho Emoto, Hirotada Fujii, Hiroshi Hirata
    JOURNAL OF MAGNETIC RESONANCE 234 1 21 - 29 2013年09月 [査読有り][通常論文]
     
    This article describes a four-channel surface coil array to increase the area of visualization for continuous-wave electron paramagnetic resonance (CW-EPR) imaging. A 776-MHz surface coil array was constructed with four independent surface coil resonators and three kinds of switches. Control circuits for switching the resonators were also built to sequentially perform EPR image acquisition for each resonator. The resonance frequencies of the resonators were shifted using PIN diode switches to decouple the inductively coupled coils. To investigate the area of visualization with the surface coil array, three-dimensional EPR imaging was performed using a glass cell phantom filled with a solution of nitroxyl radicals. The area of visualization obtained with the surface coil array was increased approximately 3.5-fold in comparison to that with a single surface coil resonator. Furthermore, to demonstrate the applicability of this surface coil array to animal imaging, three-dimensional EPR imaging was performed in a living mouse with an exogenously injected nitroxyl radical imaging agent. (C) 2013 Elsevier Inc. All rights reserved.
  • Tadatsugu Haga, Hiroshi Hirata, Piotr Lesniewski, Kevin M. Rychert, Benjamin B. Williams, Ann B. Flood, Harold M. Swartz
    CONCEPTS IN MAGNETIC RESONANCE PART B-MAGNETIC RESONANCE ENGINEERING 43B 1 32 - 40 2013年02月 [査読有り][通常論文]
     
    A surface-coil resonator that is capable of voltage-control for impedance-matching is described in the context of its application in electron paramagnetic resonance (EPR)-based tooth dosimetry. Varactor-based coupling of an 1,150 MHz surface-coil resonator was achieved to supply RF power. The developed resonator consists of a single-turn loop, 9 mm in mean diameter; a capacitor made of a polytetrafluoroethylene (PTFE) substrate; a quarter-wavelength parallel transmission line; a half-wave line balun, and varactors. The surface coil and the PTFE substrate capacitor were connected to a quarter-wavelength parallel transmission line. For the newly developed resonator, an RF magnetic field-generation efficiency of 130 T/W1/2 was achieved, and the sensitivity of the surface-coil resonator was investigated with an irradiated tooth. Measurements consisting of six sets of EPR spectra on a 10 Gy irradiated tooth using this newly developed resonator achieved a standard error of the mean (SEM) of 1.1 Gy. This level of accuracy of dose measurements was comparable to the SEM with a previously developed resonator; however, the previous resonator was not capable of voltage-control for impedance-matching adjustment, which represents a significant advance in facilitating automation. (c) 2013 Wiley Periodicals, Inc. Concepts Magn Reson Part B (Magn Reson Engineering) 43B:3240, 2013
  • Yusuke Miyake, Xiaolei Wang, Mitsuo Amasaka, Kaori Itto, Shu Xu, Hirokazu Arimoto, Hirotada Fujii, Hiroshi Hirata
    Analytical Chemistry 85 2 985 - 990 2013年01月15日 [査読有り][通常論文]
     
    This Article describes the simultaneous imaging of chiral nitroxyl radicals using electron paramagnetic resonance (EPR). Chiral nitroxyl radicals could be simultaneously visualized with the labeling of isotopic nitrogen. Chiral nitroxyl radicals, hydroxylmethyl-2,2,5,5-tetramethylpyrrolidine-1-oxyl, were visualized using the method of simultaneous EPR imaging, which refers to the visualization of two kinds of molecules with unpaired electrons in a single image scan. EPR spectra of a racemic mixture of chiral nitroxyl radicals and those of the respective R and S configurations confirmed labeling by isotopic nitrogen. 1H nuclear magnetic resonance (NMR) imaging and simultaneous imaging of solutions of chiral nitroxyl radicals were performed. The advantages and limitations of simultaneous imaging using EPR are also discussed. Simultaneous imaging with chiral-labeled nitroxyl radicals is a new application of EPR imaging and may be useful for biological studies involving biologically active chiral molecules. © 2012 American Chemical Society.
  • Hirotada G Fujii, Hideo Sato-Akaba, Miho C Emoto, Kouichi Itoh, Yasuhiro Ishihara, Hiroshi Hirata
    Magnetic resonance imaging 31 1 130 - 8 2013年01月 [査読有り][通常論文]
     
    Increased reactive oxygen species (ROS) contribute to numerous brain disorders, and ROS generation has been examined in diverse experimental models of lipopolysaccharide (LPS)-induced inflammation. The in vivo electron paramagnetic resonance (EPR)/nitroxide spin probe method has been used to analyze the redox status in animal models modulated by ROS generation. In this study, a blood-brain barrier (BBB)-permeable nitroxide spin probe, 3-hydroxymethyl-2,2,5,5-tetramethylpyrrolidine-1-oxyl (HMP), was used as a redox-sensitive nitroxide probe. Magnetic resonance images of mouse head after the injection of HMP showed that HMP was distributed throughout all regions of the mouse head including the brain, suggesting that HMP can reveal redox information in all regions of the mouse head. After the injection of HMP through the mouse tail vein 6 h after the injection of LPS, three-dimensional (3D) EPR images were obtained each minute under a field scanning of 0.3 s and with 81 projections. The reduction reaction of HMP in septic mouse heads was remarkably accelerated compared to that in control mice, and this accelerated reaction was inhibited by aminoguanidine and allopurinol, which inhibit enzymatic activities of induced nitric oxide synthase and xanthine oxidase, respectively. Based on the pharmacokinetics of HMP in mouse heads, the half-life mapping of HMP was performed in LPS-treated mouse head. Half-life maps clearly show a difference in the redox status induced by ROS generation in the presence or absence of inhibitors of ROS-generating enzymes. The present results suggest that a 3D in vivo EPR imaging system combined with BBB-permeable HMP is a useful noninvasive tool for assessing changes in the redox status in rodent models of brain disease under oxidative stress.
  • Kouichi Nakagawa, Yasunori Ohba, Boris Epel, Hitoshi Hirata
    JOURNAL OF OLEO SCIENCE 61 8 451 - 456 2012年08月 [査読有り][通常論文]
     
    A 9 GHz EPR imager that is capable of the imaging surface area of thin materials has been built. The EPR imager resolved samples spaced 1 mm apart. The developed TEIII cavity was able to detect easily similar to 1.0 mM aqueous TEMPOL solution in similar to 1.0 mm (i.d.) glass capillary placed just above the cavity. The sensitivity measured using the TEMPOL solution showed similar to 0.3 of that for the modified JEOL cavity, which was in a qualitative agreement with the calculations considering the difference in the filling factors of the cavities. The relatively low measured sensitivity of the TEIII cavity is due to utilization of the microwave field from similar to 3 mm aperture (hole) in the cavity wall. More importantly, the TEIII cavity does not require inserting the sample into the cavity and placing samples into EPR tubes.
  • Shunichi Koda, Jonathan Goodwin, Valery V. Khramtsov, Hirotada Fujii, Hiroshi Hirata
    ANALYTICAL CHEMISTRY 84 8 3833 - 3837 2012年04月 [査読有り][通常論文]
     
    The development of electron paramagnetic resonance (EPR)-based mapping of pH is an important advancement for the field of diagnostic imaging. The ability to accurately quantify pH change in vivo and monitor spatial distribution is desirable for the assessment of a number of pathological conditions in the human body as well as the monitoring of treatment response. In this work we introduce a method for EPR-based pH mapping utilizing a method of spectral-spatial imaging of sequentially scanned spectra to decrease the missing gradient rotation angle, without increasing the spatial field of view. Repeated in vitro measurements of pH phantom tubes demonstrated higher precision measurements of the hyperfine coupling constant (HFC) compared to previous EPR-based methods, resulting in mean pH values accurate to less than 0.1 pH across a range of physiologically observed values.
  • Miho Emoto, Fumiya Mito, Toshihide Yamasaki, Ken-Ichi Yamada, Hideo Sato-Akaba, Hiroshi Hirata, Hirotada Fujii
    FREE RADICAL RESEARCH 45 11-12 1325 - 1332 2011年11月 [査読有り][通常論文]
     
    The loss of paramagnetism of nitroxide radicals due to reductant reactions in biological systems, places a fundamental time constraint on their application as an imaging probe in in vivo EPR imaging studies. However, in vitro studies of the newly synthesized tetraethyl-substituted piperidine nitroxide radical demonstrated high resistivity to paramagnetic reduction when exposed to ascorbic acid, a common reduction agent in biological systems. In this work we investigated the use of these nitroxides as an imaging probe in EPR imaging of small rodents. 2,2,6,6-Tetraethyl-piperidine nitroxide (TEEPONE) is not highly soluble in aqueous media, thus a lipid-based emulsion system of lecithin was used to solubilize TEEPONE. The obtained solution was homogenous and with low viscosity, allowing smooth intravenous injection into mice tail vein. Acquired three dimensional (3D) EPR images of mouse head clearly showed TEEPONE distributed in all tissues including brain tissues, with an average measurable signal half-life of more than 80 min, thus demonstrating high resistivity to reduction due to ascorbic acid in in vivo animal studies, and the potential for use of this compound in in vivo studies of animal model systems.
  • Masashi Ohfuchi, Jonathan Goodwin, Hirotada Fujii, Hiroshi Hirata
    CONCEPTS IN MAGNETIC RESONANCE PART B-MAGNETIC RESONANCE ENGINEERING 39B 4 180 - 190 2011年10月 [査読有り][通常論文]
     
    The coregistration of electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR) images in three-dimensional (3D) data space typically involves a process of visual inspection and manual alignment of the images. This is due primarily to the use of separate scanners, which can result in a number of potential differences between the two image types, such as resolution, field-of-view, and image orientation. In this article, we describe recently developed methodology and software that enables automatic coregistration of EPR and NMR acquired images without the need for manual alignment. The technique requires the use of fiducial markers during both EPR and NMR image acquisition, which contain a solution of free radical spin probes, and allow adjustment of the positions and the fields-of-view of the measured images. In this work we present results for EPR/NMR image coregistration using an isoflurane-anesthetized mouse, injected with triarylmethyl radical (Oxo63) spin probes. The same spin probes were also used inside the fiducial markers and in plastic tubes used for phantom measurements. Using our MATLAB-based software, we were able to successfully coregister EPR/NMR images in approximately 60 s. (C) 2011 Wiley Periodicals, Inc. Concepts Magn Reson Part B (Magn Reson Engineering) 39B: 180-190, 2011
  • Ayano Enomoto, Hiroshi Hirata
    JOURNAL OF MAGNETIC RESONANCE 209 2 244 - 249 2011年04月 [査読有り][通常論文]
     
    This paper describes the development of a surface coil array that consists of two inductively coupled surface-coil resonators, for use in continuous-wave electron paramagnetic resonance (CW-EPR) imaging at 760 MHz. To make sequential EPR image acquisition possible, we decoupled the surface coils using PIN-diode switches, to enable the shifting of the resonators resonance frequency by more than 200 MHz. To assess the effectiveness of the surface coil array in CW-EPR imaging, two-dimensional images of a solution of nitroxyl radicals were measured with the developed coil array. Compared to equivalent single coil acquired images, we found the visualized area to be extended approximately 2-fold when using the surface coil array. The ability to visualize larger regions of interest through the use of a surface coil array, may offer great potential in future EPR imaging studies. (C) 2011 Elsevier Inc. All rights reserved.
  • Hirotada Fujii, Hideo Sato-Akaba, Katsuya Kawanishi, Hiroshi Hirata
    MAGNETIC RESONANCE IN MEDICINE 65 1 295 - 303 2011年01月 [査読有り][通常論文]
     
    Electron paramagnetic resonance imaging using nitroxides is a powerful method for visualizing the redox status modulated by oxidative stress in vivo. Typically, however, data acquisition times have been too slow to obtain a sufficient number of projections for three-dimensional images, when using continuous wave-electron paramagnetic resonance imager in small rodents, using nitroxides with comparatively short T(2) and a half-life values. Because of improvements in imagers that enable rapid data-acquisition, the feasibility of three-dimensional electron paramagnetic resonance imaging with good quality in mice was tested with nitroxides. Three-dimensional images of mice were obtained at an interval of 15 sec under field scanning of 0.3 sec and with 46 projections in the case of strong electron paramagnetic resonance signals. Three-dimensional electron paramagnetic resonance images of a blood brain barrier-permeable nitroxide, 3-hydroxymethyl-2,2,5,5- tetramethylpyrrolidine-1-oxyl, in the mouse head clearly showed that 3-hydroxymethyl-2,2,5,5-tetramethylpyrrolidine-1-oxyl was distributed within brain tissues, and this was confirmed by MRI observations. Based on the pharmacokinetics of nitroxides in mice, half-life mapping was demonstrated in an ischemia-reperfusion model mouse brain. Inhomogeneous half-lives were clearly mapped pixel-by-pixel in mouse head under oxidative stress by the improved continuous wave-electron paramagnetic resonance imager noninvasively. Magn Reson Med 65: 295-303, 2011. (C) 2010 Wiley-Liss, Inc.
  • Anna Pawlak, Ryohei Ito, Hirotada Fujii, Hiroshi Hirata
    CHEMICAL COMMUNICATIONS 47 11 3245 - 3247 2011年 [査読有り][通常論文]
     
    The major advancement outlined in this communication is the simultaneous visualisation of two kinds of nitroxyl radicals using electron paramagnetic resonance (EPR) spectroscopy and imaging.
  • Hirotada G. Fujii, Hideo Sato-Akaba, Hiroshi Hirata
    FREE RADICAL BIOLOGY AND MEDICINE 49 S142 - S143 2010年 [査読有り][通常論文]
  • Yusuke Ikebata, Hideo Sato-Akaba, Takashi Aoyama, Hirotada Fujii, Kouichi Itoh, Hiroshi Hirata
    MAGNETIC RESONANCE IN MEDICINE 62 3 788 - 795 2009年09月 [査読有り][通常論文]
     
    A method of post-processing to enhance the image resolution of the distribution of free radical molecules obtained with continuous-wave electron paramagnetic resonance (CW-EPR) Imaging is reported. The low spatial resolution of EPR imaging, which has created difficulties in biomedical applications, was overcome by the method of resolution-recovery for EPR imaging. High spatial resolution images for the distribution of free radical molecules with a very short relaxation time were obtained with this method. The method's two-step postprocessing consists of conventional deconvolution and filtered back-projection and a process of iterative deconvolution. The resolution-recovery method was demonstrated with three-dimensional (3D) imaging of stable nitroxyl radicals in mouse head. In phantom experiments with a solution of triarylmethyl (TAM) radicals, the spatial resolution was improved by a factor of 7 with the resolution-recovery method. Magn Reson Med 62:788-795, 2009. (C) 2009 Wiley-Liss, Inc.
  • Hideo Sato-Akaba, Yoko Kuwahara, Hirotada Fujii, Hiroshi Hirata
    ANALYTICAL CHEMISTRY 81 17 7501 - 7506 2009年09月 [査読有り][通常論文]
     
    This technical note reports, a continuous-wave electron paramagnetic resonance (CW-EPR) imager that can visualize the distribution of free radicals with a half-life of subminutes in three-dimensional (3D) space. A total of 46 EPR spectra under magnetic field gradients, called projections, were obtained for image reconstruction at an interval of 3.6 s. A shortened data-acquisition time was achieved with the use of analog signals that drove field gradient coils in the imager. 3D mapping of the half-lives of nitroxyl radicals (4-hydroxyl-2,2,6,6-tetramethyl-piperidinyl-1-oxyl) was demonstrated in their reduction reaction with ascorbic acid. Inhomogeneous half-lives were clearly mapped pixel-by-pixel in a sample tube.
  • Hideo Sato-Akaba, Hirotada Fujii, Hiroshi Hirata
    REVIEW OF SCIENTIFIC INSTRUMENTS 79 12 123701  2008年12月 [査読有り][通常論文]
     
    This paper describes improved temporal resolution for three-dimensional (3D) continuous-wave electron paramagnetic resonance (EPR) imaging. To improve temporal resolution, the duration of magnetic filed scanning that is used to obtain an EPR spectrum for each projection was reduced to 40 ms. The Helmholtz coil pair for field scanning was driven by triangular waves. The uniform distribution of projections was also used to reduce the number of projections for 3D image reconstruction. The reduction reaction of 4-hydroxy-2,2,6,6-tetramethyl-piperidinooxy with ascorbic acid was visualized by improved 3D EPR imaging techniques with a temporal resolution of 5.8 s.
  • Hideo Sato-Akaba, Hirotada Fujii, Hiroshi Hirata
    JOURNAL OF MAGNETIC RESONANCE 193 2 191 - 198 2008年08月 [査読有り][通常論文]
     
    This article describes a method for reducing the acquisition time in three-dimensional (3D) continuous-wave electron paramagnetic resonance (CW-EPR) imaging. To visualize nitroxyl spin probes, which have a short lifetime in living organisms, the acquisition time for a data set of spectral projections should be Shorter than the lifetime of the spin probes. To decrease the total time required for data acquisition, the duration of magnetic field scanning was reduced to 0.5 s. Moreover, the number of projections was decreased by using the concept Of a uniform distribution. To demonstrate this faster data acquisition, two kinds of nitroxyl radicals with different decay rates were measured in mice. 3D EPR imaging of 4-hydroxy-2,2,6,6-tetramethylpiperidine-d(17)-1-N-15-1-oxyl in mouse head was Successfully carried out. 3D EPR imaging of nitroxyl spin probes with a half-life of a few minutes was achieved for the first time in live animals. (c) 2008 Elsevier Inc. All rights reserved.
  • Hideo Sato-Akaba, Haruhiko Abe, Hirotada Fujii, Hiroshi Hirata
    MAGNETIC RESONANCE IN MEDICINE 59 4 885 - 890 2008年04月 [査読有り][通常論文]
     
    Continuous wave (CW) electron paramagnetic resonance (EPR) imaging can be used to obtain slice-selective images of free radicals without measuring three-dimensional (3D) projection data. A method that incorporated a modulated magnetic field gradient (MFG) was combined with polar field gradients to select a slice in the subject noninvasively. The slice-selective in vivo EPR imaging of triarylmethyl radicals in the heads of live mice is reported. 3D surface-rendered images were successfully obtained from slice-selective images. In the experiment in mice, a slice thickness of 1.8 mm was achieved.
  • Hirotada Fujii, Koh-ichi Sakata, Yoshihiro Katsumata, Rikiya Sato, Makoto Kinouchi, Masanori Someya, Shin-ichiro Masunaga, Masato Hareyama, Harold M. Swartz, Hiroshi Hirata
    RADIOTHERAPY AND ONCOLOGY 86 3 354 - 360 2008年03月 [査読有り][通常論文]
     
    Purpose: The goal of this study was to clarify the dynamics of oxygenation (partial pressure of oxygen, PO2) in SCC VII murine tumors in mice after X-ray irradiation. Materials and methods: Changes in PO2 in tumors were measured by 1.2-GHz electron paramagnetic resonance (EPR) spectroscopy after they were exposed to various doses of irradiation. The PO2 in tumors was followed for up to six days after irradiation at doses of 0, 5, 10, 15, and 20 Gy. Paramagnetic crystals were used as an oximetry probe and implanted into normal or tumor tissues in mice for prolonged periods. Results: The pattern of tumor oxygen after a single dose of radiation with the 5-Gy dose was different from those with other doses (10, 15, and 20 Gy). After 5 Gy, pO(2) increased rapidly (P < 0.01, Student's t test) and then returned to the level observed before irradiation by 12 h (P < 0.01). In contrast, after 10, 15, or 20 Gy, PO2 increased rapidly by 6 h after irradiation, continued to increase until at least 24 h (P < 0.01), and then gradually decreased. Conclusions: In tumors that received 5 Gy, post-irradiation increases in PO2 at 4 h after irradiation were detected by EPR oximetry (P < 0.01) noninvasively. (c) 2007 Elsevier Ireland Ltd. All rights reserved.
  • Shingo Matsumoto, Michael Graham Espey, Hideo Utsumi, Nallathamby Devasahayam, Ken-Ichiro Matsumoto, Atsuko Matsumoto, Hiroshi Hirata, David A. Wink, Periarman Kuppusamy, Sankaran Subramanian, James B. Mitchell, Murali C. Krishna
    MAGNETIC RESONANCE IN MEDICINE 59 3 619 - 625 2008年03月 [査読有り][通常論文]
     
    Oxygenation status is a key determinant in both tumor growth and responses to therapeutic interventions. The oxygen partial pressure (1302) was assessed using a novel pulsed electron paramagnetic resonance (EPR) spectroscopy at 750 MHz. Crystals of lithium phthalocyanine (LiPc) implanted into either squamous cell carcinoma (SCC) tumor or femoral muscle on opposing legs of mice were tested by pulsed EPR. The results showed pO(2) of SCC tumor was 2.7 +/- 0.4 mmHg, while in the femoral muscle it was 6.1 +/- 0.9 mmHg. A major advantage of pulsed EPR oximetry over conventional continuous-wave (CW) EPR oximetry is the lack of influence from subject motion, while avoiding artifacts associated with modulation or power saturation. Resonators in pulsed EPR are overcoupled to minimize recovery time. This makes changes in coupling associated with object motion minimal without influencing spectral quality. Consequently, pulsed EPR oximetry enables approximately a temporal resolution of similar to one second in pO(2) monitoring in conscious subjects, avoiding significant influence of anesthetics on the physiology being studied. The pO(2) in SCC tumor and muscle was found to be higher without anesthesia (3.9 +/- 0.5 mmHg for tumor, 8.8 +/- 1.2 mmHg for muscle). These results support the advantage of pulsed EPR in examining pO(2) in conscious animals with LiPc chronically implanted in predetermined regions.
  • Hiroshi Hirata, Guanglong He, Yuanmu Deng, Ildar Salikhov, Sergey Petryakov, Jay L. Zweier
    JOURNAL OF MAGNETIC RESONANCE 190 1 124 - 134 2008年01月 [査読有り][通常論文]
     
    A loop resonator was developed for 300 MHz continuous-wave electron paramagnetic resonance (CW-EPR) spectroscopy and imaging in live rats. A single-turn loop (55 mm in diameter) was used to provide sufficient space for the rat body. Efficiency for generating a radiofrequency magnetic field of 38 mu T/W-1/2 was achieved at the center of the loop. For the resonator itself, an unloaded quality factor of 430 was obtained. When a 350 g rat was placed in the resonator at the level of the lower abdomen, the quality factor decreased to 18. The sensitive volume in the loop was visualized with a bottle filled with an aqueous solution of the nitroxide spin probe 3-carbamoyl-2,2,5,5-tetramethyl-3-pyrrolin-1-yloxy (3-CP). The resonator was shown to enable EPR imaging in live rats. Imaging was performed for 3-CP that had been infused intravenously into the rat and its distribution was visualized within the lower abdomen. (c) 2007 Elsevier Inc. All rights reserved.
  • Hiroshi Hirata, Hirotada Fujii
    MEASUREMENT SCIENCE AND TECHNOLOGY 18 5 N27 - N31 2007年05月 [査読有り][通常論文]
     
    This note describes an automatic matching control (AMC) circuit for use in in vivo continuous-wave (CW) electron paramagnetic resonance (EPR) spectroscopy. This AMC circuit is based on a phase-sensitive detection scheme, and can automatically stabilize the input impedance of a 1.1 GHz tunable resonator, even if the subject moves during data acquisition. The AMC circuit was designed for measuring small animals such as mice or rats. Noise suppression with the AMC circuit was investigated with a motion phantom and a live mouse. Experimental findings support the notion that the feedback loop in the developed AMC circuit is stable and provides good noise suppression. Moreover, AMC can improve the stability of the baselines in EPR spectra with an animal subject.
  • Shingo Matsumoto, Kenichi Yamada, Hiroshi Hirata, Keiji Yasukawa, Fuminori Hyodo, Kazuhiro Ichikawa, Hideo Utsumi
    MAGNETIC RESONANCE IN MEDICINE 57 4 806 - 811 2007年04月 [査読有り][通常論文]
     
    The present study describes the advantageous application of a surface coil to electron paramagnetic resonance (EPR) irradiation in Overhauser-enhanced MRI (OMRI). OMRI is a double-resonance method for imaging free radicals based on the Over-hauser effect. Proton NMR images are recorded without and with EPR irradiation of the free radical resonance, which results in a difference proton image that shows signal enhancement in spatial regions that contain the free radical. To obtain good signal enhancement in OMRI, very high RF power and a long EPR irradiation time are required. To improve sensitivity and shorten the image acquisition time, especially for localized (and topical) applications, we developed and tested a surface-coil-type EPR irradiation coil. Theoretical calculations and experimental data showed that EPR irradiation through the surface coil could ameliorate the localized Overhauser enhancement, which was related to the ratio of 8, surface coil/B-1 volume coil in the region of interest (ROI), as expected. The increased sensitivity could also be converted into a shortened EPR irradiation time, resulting in fast data acquisition. For biomedical applications, the use of a surface coil (as opposed to a conventional volume coil) could decrease the total RF power deposition in the sample required to obtain the same Overhauser enhancement in the ROI.
  • Rizwan Ahmad, Bradley Clymer, Deepti S. Vikram, Yuanmu Deng, Hiroshi Hirata, Jay L. Zweier, Periannan Kuppusamy
    JOURNAL OF MAGNETIC RESONANCE 184 2 246 - 257 2007年02月 [査読有り][通常論文]
     
    The broad spectrum of spin probes used for electron paramagnetic resonance imaging (EPRI) result in poor spatial resolution of the reconstructed images. Conventional deconvolution procedures can enhance the resolution to some extent but obtaining high resolution EPR images is still a challenge. In this work, we have implemented and analyzed the performance of a postacquisition deblurring technique to enhance the spatial resolution of the EPR images. The technique consists of two steps; noniterative deconvolution followed by iterative deconvolution of the acquired projections which are then projected back using filtered backprojection (FBP) to reconstruct a high resolution image. Further, we have proposed an analogous technique for iterative reconstruction algorithms such as multiplicative simultaneous iterative reconstruction technique (MSIRT) which can be a method of choice for many applications. The performance of the suggested deblurring approach is evaluated using computer simulations and EPRI experiments. Results suggest that the proposed procedure is superior to the standard FBP and standard iterative reconstruction algorithms in terms of mean-square-error (MSE), spatial resolution, and visual judgment. Although the procedure is described for 2D imaging, it can be readily extended to 3D imaging. (c) 2006 Elsevier Inc. All rights reserved.
  • Yuuki Kawada, Hiroshi Hirata, Hirodata Fujii
    JOURNAL OF MAGNETIC RESONANCE 184 1 29 - 38 2007年01月 [査読有り][通常論文]
     
    This article reports experimental investigations on the use of RF resonators for continuous-wave electron paramagnetic resonance (cw-EPR) and proton nuclear magnetic resonance (NMR) imaging. We developed a composite resonator system with multi-coil parallel-gap resonators for co-registration EPR/NMR imaging. The resonance frequencies of each resonator were 21.8 MHz for NMR and 670 MHz for EPR. A smaller resonator (22 mm in diameter) for use in EPR was placed coaxially in a larger resonator (40 mm in diameter) for use in NMR. RF magnetic fields in the composite resonator system were visualized by measuring a homogeneous 4-hydroxy-2,2,6,6-tetramethyl-piperidinooxy (4-hydroxy-TEMPO) solution in a test tube. A phantom of five tubes containing distilled water and 4-hydroxy-TEMPO solution was also measured to demonstrate the potential usefulness of this composite resonator system ill biomedical science. An image of unpaired electrons was obtained for 4-hydroxy-TEMPO in three tubes, and was successfully mapped oil the proton image for five tubes. Technical problems in the implementation of a composite resonator system are discussed with regard to co-registration EPR/NMR imaging for animal experiments. (c) 2006 Elsevier Inc. All rights reserved.
  • Hirotada Fujii, Kouichi Itoh, Ramasamy P. Pandian, Motomichi Sakata, Periannan Kuppusamy, Hiroshi Hirata
    Magnetic Resonance in Medical Sciences 6 2 83 - 89 2007年 [査読有り][通常論文]
     
    The in vivo measurement of oxygen in tissues is of great interest because of oxygen's fundamental role in life. Many methods have been developed for such measurement, but all have been limited, especially with regard to repeated measurement, degree of invasive-ness, and sensitivity. We describe electron spin resonance (ESR) oximetry with paramagnetic oxygen-sensing probe for in vivo measurement of oxygen in brain tissues by homemade ESRWMR dual imaging spectroscopy. Lithium 5, 9, 14, 18, 23, 27, 32, 36-octa-n-butoxy-2,3-naphthlocyanine (LiNc-BuO) radical was employed as the solid oxygen-sensing probe, and we confirmed its ability to report partial pressure of oxygen (pO2) in brain tissues of live animals under normal and pathological conditions for more than a month. pO2 measurements could also be made repeatedly on the same animal and at the same location. The implantation site of LiNc-BuO in examined rats was verified by 0.5T magnetic resonance (MR) imaging. Septic-shock rats were used to monitor tissue oxygenation during pathological state. A decline in pO2 levels from severe hypotension during sepsis was detected, and generation of nitric oxide (NO) in brain tissues was confirmed by NO spin trapping. ESR oximetry using oxygen-sensing probe and NO spin-trapping can be used to monitor pO2 change and NO production simultaneously and repeatedly at the same site in examined animals.
  • Hiroshi Hirata, Michi Wakana, Hitoshi Susaki
    APPLIED PHYSICS LETTERS 88 25 254103  2006年06月 [査読有り][通常論文]
     
    In this letter, we report that superresolution continuous-wave electron paramagnetic resonance (cw-EPR) imaging is feasible for enhancing spatial resolution in images of unpaired electrons. We demonstrate one-dimensional superresolution EPR imaging for phantoms of 1,1-diphenyl-2-picrylhydrazyl (DPPH) powder with a 650 MHz cw-EPR imager. The spatial resolution was improved up to fivefold with iterative deconvolution techniques. Our superresolution EPR imaging includes two-stage postprocessing, i.e., noniterative deconvolution for measured EPR spectra and iterative deconvolution processing for a blurred EPR image profile with the point spread function of the low-pass window function being applied. (c) 2006 American Institute of Physics.
  • K Takeshita, CP Chi, H Hirata, M Ono, T Ozawa
    FREE RADICAL BIOLOGY AND MEDICINE 40 5 876 - 885 2006年03月 [査読有り][通常論文]
     
    Although free radicals may be involved in various types of UV-induced injuries, only a few in vivo studies of the generation of free radicals, including oxygen radicals, during exposure to ultraviolet light (UV) have been reported. In this study, the nitroxyl probe 3-carbamoyl-2,2,5,5-tetramethylpyrrolidine-N-oxyl was intravenously injected into hairless mice, and its decay was monitored in the skin with an in vivo EPR spectrometer equipped with a surface-coil-type resonator. The rate of decay of the EPR signal increased during UV (UVA+B) irradiation. This increase in signal decay was suppressed by preadministration of a spin trap, N-tert-butyl-alpha-phenylnitrone (PBN). PBN did not change the rate of signal decay in nonirradiated mice. The correlation between signal decay rate and physiological parameters such as blood velocity, blood mass, or skin temperature was low. The decay rate responded rapidly and reversibly to starting and stopping the UV illumination. Hydroxyl and peroxyl radicals caused reduction of the probe signal in vitro, and PBN inhibited only the peroxyl radical-induced signal reduction. These observations suggest that peroxyl radicals are generated in the skin of live mice during UVA+B irradiation. (c) 2005 Elsevier Inc. All rights reserved.
  • H Hirata, T Itoh, K Hosokawa, Y Deng, H Susaki
    JOURNAL OF MAGNETIC RESONANCE 175 2 177 - 184 2005年08月 [査読有り][通常論文]
     
    This article describes a systematic method for determining the cutoff frequency of the low-pass window function that is used for deconvolution in two-dimensional continuous-wave electron paramagnetic resonance (EPR) imaging. An evaluation function for the criterion used to select the cutoff frequency is proposed, and is the product of the effective width of the point spread function for a localized point signal and the noise amplitude of a resultant EPR image. The present method was applied to EPR imaging for a phantom.. and the result of cutoff frequency selection was compared with that based on a previously reported method for the same projection data set. The evaluation function has a global minimum point that gives the appropriate cutoff frequency. Images with reasonably good resolution and noise suppression can be obtained from projections with an automatically selected cutoff frequency based on the present method. (c) 2005 Elsevier Inc. All rights reserved.
  • A composition resonator assembly suitable for EPR/NMR co-registration imaging
    Matsumoto S, Nagai M, Yamada K, Hyodo F, Yasukawa K, Muraoka M, Hirata H, Ono M, Utsumi H
    Concepts in Magnetic Resonance Part B Magnetic Resonance Engineering 25B 1 1 - 11 2005年01月 [査読有り][通常論文]
  • H Hirata, H Watanabe, M Kumada, K Itoh, H Fujii
    NMR IN BIOMEDICINE 17 5 295 - 302 2004年08月 [査読有り][通常論文]
     
    This article describes a systematic approach to decoupling automatic tuning control (ATC) and automatic matching control (AMC) systems in continuous-wave (CW) electron paramagnetic resonance (EPR) spectroscopy for animal experiments. This technique enables us to improve the stability of CW-EPR spectroscopy even if the animal is moving during the data acquisition of EPR spectra. The control systems are formulated to allow the behavior of interference between them to be investigated, since they are generally coupled due to the characteristics of the microwave resonator. The stability of the entire control system in a 1.1 GHz CW-EPR spectrometer is evaluated with the generalized Nyquist stability criterion. We compare the EPR spectra of a triarylmethyl (TAM) radical that is dosed in anesthetized mice in terms of the signal-to-noise ratio (SNR) to test the precompensator for decoupling the ATC and AMC systems. The experimental findings suggest that the present technique is useful for improving the SNR of E-PR spectra in animal experiments. The SNR of the measured EPR spectra was improved by about 50% with the precompensator. Copyright (C) 2004 John Wiley Sons, Ltd.
  • H Hirata, T Kuyama, M Ono, Y Shimoyama
    JOURNAL OF MAGNETIC RESONANCE 168 2 252 - 258 2004年06月 [査読有り][通常論文]
     
    We report a difference in the spectral lineshapes of continuous-wave (CW) electron paramagnetic resonance (EPR) spectroscopy between field and frequency modulation. This finding addresses the long-standing question of the effect of modulation in EPR absorption. We compared the first-derivative EPR spectra at 1.1 GHz for lithium phthalocyanine crystals, which have a single narrow linewidth in the EPR absorption spectrum, using field and frequency modulation. The experimental findings suggest that unpaired electrons have different behaviors under perturbation due to field and frequency modulation. (C) 2004 Elsevier Inc. All rights reserved.
  • K Takeshita, T Takajo, H Hirata, M Ono, H Utsumi
    JOURNAL OF INVESTIGATIVE DERMATOLOGY 122 6 1463 - 1470 2004年06月 [査読有り][通常論文]
     
    Although oxygen radicals are thought to play a key role in the skin injury that is caused by protoporphyria, there is no direct evidence of generation of these radicals in vivo. This study measured the generation of oxygen radicals caused by visible light non-invasively in the skin of griseofulvin-induced protoporphyria model mice, using an in vivo electron spin resonance spectrometer equipped with a surface-coil-type resonator that could detect radicals within about 0.5 mm of the skin surface. A durable nitroxyl radical was administered intravenously as a probe. Light irradiation enhanced the decay of the nitroxyl signal in griseofulvin-treated mice, whereas light irradiation did not enhance the signal decay in control mice. The enhanced signal decay was completely suppressed by intravenous administration of hydroxyl radical scavengers, superoxide dismutase or catalase, or the intraperitoneal administration of desferrioxamine. The enhanced signal decay with illumination was reversible, and quickly responded to turning the light on and off. These observations suggest that the hydroxyl radical is generated via an iron-catalyzed reaction in the skin. This paper demonstrates, for the first time, the specific generation of oxygen radicals in response to light irradiation of the skin of protoporphyria model mice.
  • H Hirata, T Kuyama, M Ono, Y Shimoyama
    JOURNAL OF MAGNETIC RESONANCE 164 2 233 - 241 2003年10月 [査読有り][通常論文]
     
    A frequency modulation (FM) method was developed to measure electron paramagnetic resonance (EPR) absorption. The first-derivative spectrum of 1,1-diphenyl-2-picrylhydrazyl (DPPH) powder was measured with this FM method. Frequency modulation of up to 1.6 MHz (peak-to-peak) was achieved at a microwave carrier frequency of 1.1 GHz. This corresponds to a magnetic field modulation of 57 muT (peak-to-peak) at 40.3 mT. By using a tunable microwave resonator and automatic control systems, we achieved a practical continuous-wave (CW) EPR spectrometer that incorporates the FM method. In the present experiments, the EPR signal intensity was proportional to the magnitude of frequency modulation. The background signal at the modulation frequency (1 kHz) for EPR detection was also proportional to the magnitude of frequency modulation. An automatic matching control (AMC) system reduced the amplitude of noise in microwave detection and improved the baseline stability. Distortion of the spectral lineshape was seen when the spectrometer settings were not appropriate, e.g., with a lack of the open-loop gain in automatic tuning control (ATC). FM is an alternative to field modulation when the side-effect of field modulation is detrimental for EPR detection. The present spectroscopic technique based on the FM scheme is useful for measuring the first derivative with respect to the microwave frequency in investigations of electron-spin-related phenomena. (C) 2003 Elsevier Inc. All rights reserved.
  • Salikhov, I, H Hirata, T Walczak, HM Swartz
    JOURNAL OF MAGNETIC RESONANCE 164 1 54 - 59 2003年09月 [査読有り][通常論文]
     
    An improved external loop resonator (ELR) used for L-band electron paramagnetic resonance (EPR) spectroscopy is reported. This improvement is achieved by shortening the parallel coaxial line. The resonant structure is formed by two single turn coils (10 mm in diameter) that are connected to a parallel coaxial line. A resonance frequency of 1197 MHz and a quality factor of 466 were obtained in the absence of biological tissue and similar to1130 MHz and similar to50 with a living animal, respectively. The sensitivity of the new ELR was compared to the previously developed ELR using three types of EPR samples: (1) paramagnetic material with no biological tissue, (2) paramagnetic material in a leg and in the peritoneal cavity of a dead rat, and (3) paramagnetic material in the back of an anesthetized rat. The sensitivity was 1.2-1.6 times greater in the rat and 4.2 times without tissue. (C) 2003 Elsevier Science (USA). All rights reserved.
  • H Hirata, Y Yamaguchi, T Takahashi, ZW Lu
    MAGNETIC RESONANCE IN MEDICINE 50 1 223 - 227 2003年07月 [査読有り][通常論文]
     
    A method for estimating the characteristics of an automatic matching control (AMC) system for in vivo electron paramagnetic resonance (EPR) spectroscopy is described. AMC is also known as automatic coupling control (ACC) and is used to compensate for perturbation due to movement of the subject animal. The open-loop function of the AMC system is derived and the characteristics (gain, phase margin, steady-state error, system bandwidth, and disturbance rejection) of the system are examined. The proposed method is supported by experimental findings. The frequency response of perturbation due to the movement of an anesthetized rat was measured with a 1.1-GHz continuous-wave EPR spectrometer. Disturbance rejection with the AMC system was also considered for respiratory motion and the heartbeat of the anesthetized rat, and these perturbations were reduced by about 40 dB in the power spectrum of the output of the diode detector in the spectrometer. (C) 2003 Wiley-Liss, Inc.
  • GL He, SP Evalappan, H Hirata, YM Deng, S Petryakov, P Kuppusamy, JL Zweier
    MAGNETIC RESONANCE IN MEDICINE 48 6 1057 - 1062 2002年12月 [査読有り][通常論文]
     
    Surface coil resonators have been widely used to perform topical EPR spectroscopy. They are usually positioned adjacent to or implanted within the body. For EPR applications these resonators have a number of important advantages over other resonator designs due to their ease of sample accessibility, mechanical fabrication, implementation of electronic tuning and coupling functions, and low susceptibility to sample motions. However, a disadvantage is their B-1 field inhomogeneity, which limits their usefulness for 3D imaging applications. We show that this problem can be addressed by mapping and correcting the B-1 field distribution. We report the use of EPR imaging (EPRI) to map the B-1 distribution of a surface coil resonator. We show that EPRI provides a fast, accurate, and reliable technique to evaluate the B-1 distribution. 3D EPRI was performed on phantoms, prepared using three different saline concentrations, to obtain the B-1 distribution. The information obtained from the phantoms was used to correct the images of living animals. With the use of this B-1 correction technique, surface coil resonators can be applied to perform 3D mapping of the distribution of free radicals in biological samples and living systems.
  • H Hirata, M Ueda, N Ono, Y Shimoyama
    JOURNAL OF MAGNETIC RESONANCE 155 1 140 - 144 2002年03月 [査読有り][通常論文]
     
    Continuous-wave EPR spectroscopy using a frequency modulation (FM) scheme was developed. An electronically tunable resonator and an automatic tuning control (ATC) system were used. Using the FM scheme instead of magnetic field modulation, we detected EPR absorption at the first derivative mode. We used a microwave frequency of 1.1 GHz in the present experiment. Similar signal-to-noise ratios were obtained with conventional field modulation and the FM method, and a low-quality factor EPR resonator was not necessary to suppress the significant microwave reflection from the resonator. The FM method with a tunable resonator may be an alternative solution to achieving phase-sensitive detection, when the side-effects of magnetic field modulation, such as microphonic noise and mechanical vibration, are detrimental for EPR detection. (C) 2002 Elsevier Science (USA).
  • M Ono, A Suenaga, H Hirata
    MAGNETIC RESONANCE IN MEDICINE 47 2 415 - 419 2002年02月 [査読有り][通常論文]
     
    The relationship between an RF magnetic field and an electric shielding plate called a bridge in a bridged loop-gap resonator (BLGR), which is used for EPR spectroscopy and imaging, is examined. The magnetic field in a BLGR is perturbed due to discontinuity of the conductive loop and electric fringing fields near the gaps. The magnetic field homogeneity in the BLGR can be improved with a bridge. The optimum angle for such bridges can be found by measuring the RF magnetic field. In this study, the RF magnetic field was measured for BLGRs 70 mm in diameter, with a resonance frequency of 302 +/- 5 MHz. The field uniformity on a circle with a radius of 27 mm was improved by 8% with bridges at optimal angles. Improved RF magnetic field homogeneity associated with a BLGR is demonstrated. Magn Reson Med 47:415-419, 2002. (C) 2002 Wiley-Liss, Inc.
  • H Hirata, ZW Luo
    MAGNETIC RESONANCE IN MEDICINE 46 6 1209 - 1215 2001年12月 [査読有り][通常論文]
     
    Stability analysis and design of an automatic frequency control (AFC) system for in vivo continuous-wave EPR spectroscopy is described. The open-loop function of the feedback control system for the AFC was derived and the stability of the feedback loop systematically examined. A stability analysis of the system is demonstrated and a systematic design procedure is proposed. The design is started from the required system specifications (phase margin, steady-state error, and system bandwidth) and clear guidelines for designing an AFC system are given. A case study of the design is presented based on the specific needs of in vivo EPR measurements. A phase margin of 53 degrees, a steady-state error of 1.6%, and a system bandwidth of up to 1.8 kHz were obtained in the designed AFC system. The system specifications defined in advance are satisfied in this case study. (C) 2001 Wiley-Liss, Inc.
  • H Hirata, T Walczak, HM Swartz
    REVIEW OF SCIENTIFIC INSTRUMENTS 72 6 2839 - 2841 2001年06月 [査読有り][通常論文]
     
    This note describes considerable additional information on the key parameters of an electronically tunable surface-coil-type resonator for L-band continuous-wave electron paramagnetic resonance (EPR) spectroscopy [Hirata , J. Magn. Reson. 142, 159 (2000)]. For the 1.1 GHz prototype tunable surface coil (10.6 mm in diameter), the measured efficiency for generating the rf magnetic field is 77 muT/W-1/2. The unloaded quality factor of the tunable surface coil is in the range of 260-310. In absence of an EPR sample, 57% of the magnetic energy in the system is stored in the parallel coaxial line, 16% in the surface coil, and a half of the energy is dissipated in the parallel coaxial line. The energy dissipation for the surface coil occurs mainly through radiation (25% of the total energy dissipation). The level of the second harmonic in the reflected microwaves generated by the tunable surface coil was measured. The varactor diodes used in the matching and tuning circuits are the dominant source of the second harmonic. (C) 2001 American Institute of Physics.
  • H Hirata, T Walczak, HM Swartz
    JOURNAL OF MAGNETIC RESONANCE 142 1 159 - 167 2000年01月 [査読有り][通常論文]
     
    The automatic frequency control (AFC) circuit in conventional electron paramagnetic resonance (EPR) spectrometers automatically tunes the microwave source to the resonance frequency of the resonator. The circuit works satisfactorily for samples stable enough that the geometric relations in the resonance structure do not change in a significant way. When EPR signals are measured during in vivo experiments with small rodents, however, the distance between the signal source and the surface-coil detector can change rapidly. When a conventional AFC circuit keeps the oscillator tuned to the resonator under those conditions, the resultant frequency change may exceed +/- 5 MHz and markedly shift the position of the EPR signal. Such a shift results in unacceptable effects on the spectra, especially when the experimenter is dealing with narrow EPR lines. The animal movement also causes a mismatching of the resonator and the 50-ohm transmission line. Direct results of this mismatching are increased noise; shifts in the position of the baseline; and a high probability of overdriving the signal preamplifier with consequent loss of the EPR signal. We therefore designed, built, and tested a new surface-coil resonator using varactor diodes for tuning the resonance frequency to the fixed frequency oscillator and for capacitive matching of the resonator to the 50-ohm transmission line. The performance of the automatic matching system was tested in vivo by measuring EPR spectra of lithium phthalocyanine implanted in rats. Stability and sensitivity of the spectrometer were evaluated by measuring EPR spectra with and without the use of the automatic matching system. The overall experimental performance of the spectrometer was found to significantly improve during in vivo experiments using the automatic matching system. Excellent matching between the 50-ohm transmission line and the resonator was maintained under all experimental circumstances that were tested. This should allow us now to carry out experiments that previously were not possible. (C) 2000 Academic Press.
  • H Hirata, M Ono
    REVIEW OF SCIENTIFIC INSTRUMENTS 68 9 3595 - 3596 1997年09月 [査読有り][通常論文]
     
    This note describes a newly developed flexible surface-coil-type resonator (FSCR) used for electron paramagnetic resonance (EPR) measurements. A conventional FSCR has used a balanced transmission line made by coaxial lines. The new resonator uses triaxial cable in order to avoid anisotropy of flexure of the transmission line. Experimental results show that the EPR signal measured with the triaxial FSCR is 35% stronger than that measured with the conventional FSCR. (C) 1997 American Institute of Physics.
  • H Hirata, M Ono
    REVIEW OF SCIENTIFIC INSTRUMENTS 68 9 3528 - 3532 1997年09月 [査読有り][通常論文]
     
    This article describes an impedance-matching system for a flexible surface-coil-type resonator (FSCR) used in electron paramagnetic resonance (EPR) experiments. To design the matching system, the input impedance of the FSCR was formulated using transmission line theory, and then the parameters of a matching circuit using varicap diodes were calculated. Experimental measurements of input impedance showed the validity of the formulation and the usefulness of the matching system. The matching circuit made by the varicap diodes 1SV186 offered the tunable bandwidth of 50 MHz for the prototype FSCR. Such a matching system also offers the possibility of remotely tuning EPR resonators electronically. (C) 1997 American Institute of Physics.
  • H Hirata, T Walczak, HM Swartz
    REVIEW OF SCIENTIFIC INSTRUMENTS 68 8 3187 - 3191 1997年08月 [査読有り][通常論文]
     
    The development of in vivo electron paramagnetic resonance spectrometers has generated a need for a better method of inductive coupling between a microwave resonator and a transmission Line, We describe here an approach, based on introducing an additional impedance transformer between a coupling loop and the transmission line. This additional transformer decreases (by a factor of 20) the resonance frequency shift that occurs during adjustment of the coupling. The calculated optimal length is slightly greater than a quarter of the wavelength of the electromagnetic waves. Experimental measurements of the return loss for the matching circuit has shown the validity of the calculations and the usefulness of the proposed theoretical model. (C) 1997 American Institute of Physics.
  • H Hirata, M Ono
    REVIEW OF SCIENTIFIC INSTRUMENTS 67 1 73 - 78 1996年01月 [査読有り][通常論文]
     
    This paper presents a method for estimating the resonance frequency of a bridged loop-gap resonator (BLGR). It first describes the structure of the BLGR and its equivalent electrical circuit, and then a procedure for calculating the resonance frequency is revealed. In this procedure, node analysis, which is a circuit theory, is applied to calculate the branch voltages of the equivalent circuit. Finally, this paper reports on the calculations and measurements of the resonance frequency, and the validity of the method for estimating resonance frequency. (C) 1996 American Institute of Physics.
  • H HIRATA, H IWAI, M ONO
    REVIEW OF SCIENTIFIC INSTRUMENTS 66 9 4529 - 4534 1995年09月 [査読有り][通常論文]
     
    This paper presents a method for analyzing the sensitivity of a flexible surface-coil-type resonator (FSCR). It first describes the configuration and the operation principle of the FSCR and then a method for estimating relative sensitivity of the FSCR. In this estimation, the quality factor and the filling factor of the FSCR are formulated because the strength of electron spin resonance (ESR) signals is proportional to the product of these factors. Finally, this paper reports experiments, measuring the ESR spectra of 1,1-Diphenyl-2-picrylhydrazyl powder, confirming the validity of the proposed method. (C) 1995 American Institute of Physics.
  • Y SAKAMOTO, H HIRATA, M ONO
    IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES 43 8 1840 - 1847 1995年08月 [査読有り][通常論文]
     
    The purpose of the present paper is to establish a method of design for a multicoupled loop-gap resonator used for pulsed electron paramagnetic resonance measurements, For the design of resonator characteristics, the method has an advantage of a systematic approach without iterative calculations, In this design, the number of loop-gap resonators used is first determined from the pass band required as the specifications of the resonator, To satisfy the specifications, electrical parameters of an equivalent circuit and the dimensions of the resonator are estimated, By the proposed method, a prototype resonator which has the operation frequency of 1,3 GHz is designed and fabricated, For the prototype resonator, the characteristics of the return loss agree with the required ones, As a result, the validity of the design method is experimentally confirmed.
  • Hiroshi Hirata, Sadayuki Ueha
    IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control 42 2 225 - 231 1995年 [査読有り][通常論文]
     
    The purpose of the present paper is to establish a method of design for a traveling wave type ultrasonic motor. This method is based on two models for the ultrasonic motor. A two-dimensional elastic contact model is used for estimating the friction drive between the rotor and vibrator of the motor. Moreover, an electrical equivalent circuit is used to estimate the interaction between the electrical and mechanical parts of the vibrator. The proposed method is applied to the design of a prototype motor. To determine applicability of the method, the load characteristics of the prototype motor are measured. The measured characteristics agree with the required ones which are specified in advance. As a result, the validity of the proposed method is experimentally confirmed. 0885-3010/95$04.00 © 1995 IEEE
  • M ONO, K ITO, N KAWAMURA, KC HSIEH, H HIRATA, N TSUCHIHASHI, H KAMADA
    JOURNAL OF MAGNETIC RESONANCE SERIES B 104 2 180 - 182 1994年06月 [査読有り][通常論文]
  • Hiroshi Hirata, Sadayuki Ueha
    IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 40 4 402 - 406 1993年07月 [査読有り][通常論文]
     
    The purpose of the present paper is to propose a method of calculation of load characteristics for a traveling wave type ultrasonic motor (TWUM). A method using an equivalent circuit is proposed for estimating the performance of the motor. Using this method, a systematic approach is achieved for estimating the performance, including the electrical and the mechanical parts of the motor. In the proposed method, a governing equation of the motor is derived to describe the relation between the applied voltage at an electrical terminal, vibration velocities, and the external forces at mechanical of a vibrator. An estimation method of the forces between the rotor and the vibrator o the motor is revealed to calculate the load characteristics. On the basis of the proposed method, the load characteristics are numerically calculated and compared with the measured ones. Since the calculated load characteristics curves agree well with the measured ones, the validity of the proposed method for estimating the load characteristics is confirmed.
  • Hiroshi Hirata, Sadayuki Ueha
    Journal of the Acoustical Society of Japan (E) 13 2 77 - 84 1992年 [査読有り][通常論文]
     
    A piezoelectric circular plate, which vibrates in non-axisymmetric or flexural vibration mode, is used for the stator vibrator of an ultrasonic motor. To design the stator vibrator adequately, the force factor of the vibrator should be estimated in advance. The theoretically calculated force factors for the two vibration modes are compared with the measured ones to obtain good agreement. In order to study how to control the force factor, the relation between the shape of the vibrator and the force factor is also considered. © 1992, Acoustical Society of Japan. All rights reserved.
  • H HIRATA, S UEHA
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 31 Suppl. 31-1 248 - 250 1992年 [査読有り][通常論文]
     
    Using a two-dimensional elastic contact theory, the pressure distribution on the area of contact between the rotor and the stator vibrator of an ultrasonic motor is calculated. In this calculation, the stator vibrator and the rotor are assumed to be a rigid body and an elastic half-space, respectively. The no-load revolution speed of the motor using the calculated pressure distribution is estimated, and is compared with the measured speed. As a result, it is proved that the revolution speed can be estimated by using the calculated pressure distribution if the assumption is satisfied.
  • Takehiro Takano, Hiroshi Hirata, Yoshiro Tomikawa
    Journal of the Acoustical Society of Japan (E) 11 3 161 - 172 1990年 [査読有り][通常論文]
     
    The mathematical analysis of non-axisymmetric vibration of a piezoelectric annular plate and its application to an ultrasonic motor had previously been reported. In this paper, analysis of the annular plate clamped on its inside or outside circumferences is stated from the view point of its application to an ultrasonic motor. Calculated results reveal the potential usage of the vibration modes for a thin-type ultrasonic motor. © 1990, Acoustical Society of Japan. All rights reserved.
  • Y TOMIKAWA, K ADACHI, H HIRATA, T SUZUKI, T TAKANO
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 29 Suppl. 29-1 179 - 181 1990年 [査読有り][通常論文]
     
    Excitation of a progressive wave in a straight and thin bar vibrating in the flexural mode can be utilized to construct a transport device such as a parts-feeder. A new method to excite the progressive wave is proposed herein which has been proved possible by simulation and experiment. Excitation of a progressive wave without utilizing the concept of impedance matching in a transmission line is done using two adjacent modes of flexural vibration.
  • Takehiro Takano, Hiroshi Hirata, Yoshiro Tomikawa
    IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 37 6 558 - 565 1990年 [査読有り][通常論文]
     
    The development of an ultrasonic motor using nonaxisymmetric vibration modes of a piezoelectric annular plate is described. A piezoelectric annular plate is analyzed to And its mode patterns, elliptic motions of displacement for the motor, distributions of the induced charge on the plate surface, and calculate electromechanical coupling factors. Then, on the basis of the analyzed results, motors using the annular plate have been built and their characteristics measured. © 1990, IEEE
  • Y TOMIKAWA, T TAKANO, H HIRATA, T OGASAWARA
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 28 suppl. 28-1 161 - 163 1989年 [査読有り][通常論文]
  • T TAKANO, Y TOMIKAWA, T OGASAWARA, H HIRATA
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 28 Suppl. 28-2 202 - 205 1989年 [査読有り][通常論文]

書籍

  • “Resonators for Clinical Electron Paramagnetic Resonance” in: Measuring Oxidants and Oxidative Stress in Biological Systems, L. J. Berliner and N. L. Parinandi (eds.)
    H. Hirata, S. Petryakov, W. Schreiber (担当:分担執筆範囲:pp. 189–218)
    Springer Nature Switzerland AG 2020年08月

講演・口頭発表等

  • Overview of Electron Paramagnetic Resonance-Based Human Tooth Dosimetry  [招待講演]
    H. Hirata, I. Yamaguchi, M. Miyake
    4th Conference on Nuclear Analytical Techniques (NAT2020) Jointed with 6th Symposium on Radiation in Medicine, Space, and Power (RMSP-VI), 2020年11月 口頭発表(招待・特別)
  • Recent Progress in 3D Extracellular pH Mapping of Tumors Using EPR  [招待講演]
    Hiroshi Hirata
    International Conference “Magnetic Resonance–Current Status and Future perspectives” (EPR-75) 2019年09月 口頭発表(招待・特別)
  • In vivo three-dimensional extracellular pH mapping of tumors using EPR  [招待講演]
    Hiroshi Hirata
    Joint Conference of 21st International Society for Magnetic Resonance (ISMAR) and 15th European Magnetic Resonance Congress (EUROMAR) 2019年07月 口頭発表(招待・特別)
  • In vivo extracellular pH mapping of tumors using EPR imaging  [招待講演]
    Hiroshi Hirata
    Joint Conference of Asia-Pacific EPR/ESR Symposium 2018 and 3rd International EPR (ESR) Society Symposium (APES-IES 2018) 2018年09月 口頭発表(招待・特別)
  • In vivo extracellular pH mapping of tumors using electron paramagnetic resonance  [招待講演]
    Hiroshi Hirata
    46th Annual Meeting of International Society on Oxygen Transport to Tissue (ISOTT 2018) 2018年07月 口頭発表(基調)
  • Three-dimensional oxygen mapping using a pair of isotopic nitroxyl radicals and CW-EPR-based single-point imaging  [招待講演]
    Hiroshi Hirata
    EPR 2017: International Conference on Electron Paramagnetic Resonance Spectroscopy and Imaging of Biological Systems 2017年07月 口頭発表(招待・特別)
  • CW-EPR-based oxygen mapping technique using a pair of isotopic nitroxyl radicals  [招待講演]
    Hiroshi Hirata
    Xth International Workshop on EPR in Biology and Medicine 2016年10月 口頭発表(招待・特別)
  • Development of a CW-EPR-based oxygen-mapping technique using a pair of isotopic nitroxyl radicals  [招待講演]
    Hiroshi Hirata
    Asia-Pacific EPR/ESR Symposium 2016 2016年08月 口頭発表(招待・特別)
  • In vivo tumor extracellular pH monitoring using EPR spectroscopy  [招待講演]
    Hiroshi Hirata
    Magnetic Resonance: Fundamental research and pioneering applications (MR-70) 2014年06月 口頭発表(招待・特別)
  • MR imaging of oxidative stress: Electron paramagnetic resonance imaging –Challenges to functional imaging–  [招待講演]
    Hiroshi Hirata
    COST Action BM1203 EU-ROS Working Group Meeting 2013年05月 口頭発表(招待・特別)

その他活動・業績

  • 電子常磁性共鳴イメージングと生物医学応用
    平田 拓 ぶんせき 2019 (12) 538 -544 2019年12月 [査読有り][招待有り]
  • 生体のESRイメージング
    平田 拓 分光研究 64 (6) 573 -581 2015年12月 [査読有り][招待有り]
  • 平田 拓 日本薬理学雑誌 140 (4) 146 -150 2012年 [査読無し][通常論文]
     
    不対電子のエネルギー吸収を特異的に検出することができる電子常磁性共鳴(EPR)分光(電子スピン共鳴,ESRとも呼ばれる)は,フリーラジカル分子の研究において強力な計測手法となっている.EPR分光は,核磁気共鳴(NMR)とは兄弟関係にある磁気共鳴分光法であり,NMRイメージング(核スピンの可視化)同様に電子スピンの分布を可視化するイメージング法も30年来研究されてきた.近年になり,短時間で電子スピンの3次元空間分布を計測する技術が開発された.本稿では,高速EPRイメージングを用いて,生体内の酸化還元状態を可視化する,レドックス計測について紹介する.電子スピンの緩和時間は,ナノ秒からマイクロ秒のオーダーであり,NMRと同様のパルス法による計測は容易ではない.特に,生体を対象とする低周波・低磁場のEPR計測では,連続波を用いた計測が主に用いられている.高速に磁場を掃引するEPRイメージング装置の開発により,生体内で寿命が短いフリーラジカル種の検出,測定が可能になった.また,ニトロキシルラジカルの寿命は溶液または生体中の還元作用の強さを反映するため,ニトロキシルラジカルの信号の消失速度を測定することにより,酸化還元状態(レドックス)をマッピングする方法を説明する.通常,3次元画像計測は長い計測時間が必要とされ,生体内でのレドックスマップを得ることは容易ではなかったが,計測技術の進歩に...
  • H Hirata, H Fujii CURRENT ORGANIC CHEMISTRY 10 (5) 521 -534 2006年03月 [査読無し][通常論文]
     
    This review article describes recently developed technologies in electron paramagnetic resonance (EPR) spectroscopy and imaging. Automatic control techniques used for a continuous-wave (CW) EPR spectrometer are discussed. These techniques can solve problems created by the motion of animals. Recent developments with timc-domain EPR spectroscopy are also reported. Time-domain EPR spectroscopy is a technically challenging method because of the very short relaxation time that free radicals have in biological tissue. EPR imaging techniques are also reviewed, which are able to visualize free radicals in animal subjects non-invasively. Current status and future trends in the development of instruments for EPR spectroscopy and imaging are also presented, especially for biomedical applications. An important and powerful application of in vivo EPR spectroscopy and imaging is the detection of free radicals generated in biological specimens, which are so-called bioradicals. This article reviews these bioradicals, such as reactive oxygen species (ROS), free radicals generated from xenobiotics, metal ions, and common drugs, and it especially focuses on the direct-detection of bioradicals, rather than indirect detection. Drug-induced reaction mechanisms with hydrazine-based drugs, carcinogenic nitroso compounds, and prescription drugs for patients with hypertension (nifedipine) are discussed in detail based on in vivo studies with small animals. Metal-related reactions in vivo are also discussed with irons, chromate, and manganese.
  • H Hirata, ZW Luo MAGNETIC RESONANCE IN MEDICINE 49 (5) 977 -977 2003年05月 [査読無し][通常論文]
  • K Takeshita, CP Chi, H Hirata, M Ono, H Suzaki, T Ozawa FREE RADICAL BIOLOGY AND MEDICINE 33 S176 -S176 2002年 [査読無し][通常論文]

受賞

  • 2019年06月 国際磁気共鳴医学会 優秀レビュアー賞 Magnetic Resonance in Medicine
     
    受賞者: 平田 拓
  • 2018年07月 国際磁気共鳴医学会 優秀レビュアー賞 Magnetic Resonance in Medicine
     
    受賞者: 平田 拓
  • 2003年10月 電子スピンサイエンス学会 奨励賞
     生命科学研究のための電子スピン共鳴装置の開発 
    受賞者: 平田 拓

共同研究・競争的資金等の研究課題

  • 電子スピンでセンシングする悪性腫瘍の高精度酸素イメージング法の開発
    日本学術振興会:科学研究費助成事業 (挑戦的研究(開拓))
    研究期間 : 2021年07月 -2025年03月 
    代表者 : 平田拓
  • 日本学術振興会:科学研究費助成事業 (基盤研究(B))
    研究期間 : 2019年04月 -2022年03月 
    代表者 : 平田 拓
  • 日本学術振興会:国際共同研究加速基金 (国際共同研究強化(B))
    研究期間 : 2018年10月 -2022年03月 
    代表者 : 平田 拓
  • 酸素分圧画像を指標とする強度変調放射線治療モデル実験
    日本学術振興会:科学研究費補助金(挑戦的萌芽研究)
    研究期間 : 2016年04月 -2018年03月 
    代表者 : 平田 拓
  • 日本学術振興会:科学研究費補助金 (基盤研究(A))
    研究期間 : 2014年04月 -2018年03月 
    代表者 : 平田 拓
  • キラリティー磁気共鳴分子イメージング
    内閣府:最先端・次世代研究開発支援プログラム
    研究期間 : 2011年02月 -2014年03月 
    代表者 : 平田 拓
  • 高速電子常磁性共鳴イメージング法の開発
    科学技術振興機構:先端計測分析技術・機器開発事業
    研究期間 : 2008年10月 -2011年03月 
    代表者 : 平田 拓
  • 文部科学省:科学研究費補助金 (基盤研究(B))
    研究期間 : 2009年 -2011年 
    代表者 : 平田 拓
     
    平成22年度は、計画通り電子スピン共鳴(ESR)スペクトルからpHおよび酸素分圧を可視化する実験を行った。pH感受性および酸素感受性のニトロキシルラジカル分子二種類を使用し、試験管による模擬試料を用いてpHおよび酸素分圧を可視化した。実験に先立ち取得したpHおよび酸素分圧の校正曲線を用いて、スペクトル空間ESRイメージング法により得られたスペクトル情報をpHおよび酸素感受性に変換した。実験の結果、pHの分解能0.1程度、酸素分圧の分解能5mmHgが得られた。しかしながら、酸素分圧の測定値の精度が十分ではないことが明らかとなったため、データ処理の方法等を再検討した。その結果、実験において次の課題が明らかとなり、データ処理により外乱の影響を取り除く補正を行った。すなわち、(1)マグネット温度のドリフトによる中心磁場の変化、(2)磁場掃引幅の誤差、(3)磁場掃引幅の変化に起因する中心磁場の変化、(4)水溶液試料中のうず電流によるスペクトルの歪み、が最終的に得られるスペクトル情報に対して外乱となることが分かった。pHの可視化については、ニトロキシルラジカルの超微細構造による3つのエネルギー吸収スペクトルの内、低磁場側のスペクトルと中間のスペクトルの間隔を測定することによりpHを測定した。それぞれのスペクトルを単独で測定したデータから二つのエネルギー吸収の間隔を求める方法においては、上...
  • 文部科学省:科学研究費補助金 (萌芽研究, 挑戦的萌芽研究)
    研究期間 : 2008年 -2010年 
    代表者 : 平田 拓
     
    平成22年度は、電子常磁性共鳴(EPR)イメージング法の解像度改善を目指した。大学内において動物実験の計画が承認されるまでの時間を用いて、模擬試料による解像度改善の実験を行った。また、三次元画像再構成時に自動的に解像度と信号対雑音比を最適化するプログラムを開発した。加えて、分子イメージングの一種であるEPRイメージングの画像を動物の解剖学的画像に重ね合わせるために、EPR/NMRコレジストレーション・イメージングに利用するソフトウエアを開発した。その結果、三次元画像再構成の最適化と、EPRおよびプロトンNMR画像の半自動重ね合せが実現した。画像の重ね合せには、キャピラリー管による位置合わせのマーカーを用いた。EPR画像の解像度改善のためには、正確に点広がり関数を推定する必要があるが、実験に使用したデータセットでは、繰り返しデコンボリューションによる一定の解像度改善は見られたが、目標とする5倍の解像度改善には至らなかった。一方、EPR/NMRコレジストレーション・イメージングは、実用的に使用可能なソフトウエアをMatlab上に構成することができたため、今後の実験に供することが可能である。特に、画像の重ね合せを半自動で行う点は、訓練されていないオペレータが操作することを容易にするため、実用的な観点からも前進したといえる。EPRイメージングの解像度改善には、いまだ考慮されていない要...
  • 文部科学省:科学研究費補助金(基盤研究(B))
    研究期間 : 2007年 -2009年 
    代表者 : 藤井 博匡, 黄田 育宏, 伊藤 康一, 平田 拓, 黄田 育宏
     
    活性酸素で代表されるフリーラジカルを画像化するESRイメージング法は、分子イメージングの研究にはなくてはならないイメージング技法である。本研究課題では、実験動物の解剖画像を高解像度でイメージングできるMRIとESRイメージング法とを融合し、実験動物の生理機能を画像表示できるESR・MRI融合装置を試作した。本装置を活用して生理機能のイメージングを行い、生活習慣病やメタボリックシンドローム抑制のためのスクリーニング法の開発に利用する。
  • 文部科学省:科学研究費補助金(基盤研究(B))
    研究期間 : 2006年 -2008年 
    代表者 : 平田 拓, 藤井 博匡, 伊藤 康一, 藤井 博匡, 伊藤 康一, 赤羽 英夫
     
    実験小動物として用いられるマウスを対象として、電子スピン共鳴(ESR)イメージング法の研究を行った。マウス頭部を計測する650MHzのマイクロ波共振器を作製し、ESR分光装置を改良した。また、スライス選択ESR画像を取得するイメージング法を開発した。さらに、データ取得を高速化することにより、マウス頭部において、半減時が短い六員環のナイトロキシルラジカルを可視化することに成功した。
  • 文部科学省:科学研究費補助金(基盤研究(B))
    研究期間 : 2005年 -2006年 
    代表者 : 藤井 博匡, 伊藤 康一, 平田 拓
     
    複数の計測手法を用いた分子イメージングに関する研究領域は、近年急激な進歩を遂げつつある。この研究手法は、"画像医学"と"分子生物学"とを連携し、生命現象の鍵となる物質の発現を非侵襲的に画像解析をする新たな技術が開発されている。分子イメージングの技術から貴重な生命科学情報が得られることから、基礎科学的にも臨床医学的にも、その将来性が大いに期待されている学問領域である。我々は、PETやMRIなどの既存の手法に比べ、より高感度にフリーラジカルなどの常磁性物質を非侵襲的に検出しうる電子スピン共鳴法(ESR)を駆逐し、超高感度であり、且つ、高解像度である分子イメージング手法の確立を目指しており、本研究を遂行するため、平成17年度では"分子イメージング用の高感度・高解像度の磁気共鳴画像化装置"の開発すすめた。平成17年度での開発の柱は、1)ESR・MRI同時画像化装置に適する新たな磁気標識法の開発、2)ESRイメージング装置の高磁場勾配化、3)ESR・MRI共用共振器の開発であった。平成18年度は、前年の開発を受けて以下の3つのサブプロジェクトを進めた。1)サブプロジェクト1:ESR・MRI同時共振器の設計について、2)サブプロジェクト2:ESR・MRI同時画像化システム用磁気回路の設計について、3)サブプロジェクト3:磁気標識を用いた分子イメージングの研究である。以上のプロジェクトで開...
  • 文部科学省:科学研究費補助金(基盤研究(C))
    研究期間 : 2004年 -2005年 
    代表者 : 平田 拓, 藤井 博匡
     
    本研究プロジェクトでは、マウスの頭部を測定する電子スピン共鳴分光装置の開発を行ってきた。当初設定した目的に関して、以下のような到達度であった。(1)電子スピン共鳴スペクトラムの信号対雑音比を向上する。4〜6週齢程度のマウスの頭部を測定可能な共振器を開発した。血中に存在するラジカルを頭部においてイメージングすることに成功した。腹腔内に投与した数十ミリモル/リットルの造影剤(Oxo-63)0.1mlが、血流で頭部に運ばれた画像を検出できるようになった。(2)直接フーリエ変換再構成法による二次元電子スピン共鳴画像化システムの開発系統的に画像再構成に用いるフィルタの遮断周波数を決定するための評価関数を提案し、計算コードを開発した。(3)電子スピン共鳴分光装置の安定性改善マウスを用いた実験おいて、十分にイメージングが行える程度の安定性を実現した。(4)動物実験による実証試験マウス頭部の電子スピン共鳴イメージングを行い、開発した技術の有効性を検討した。ハードウエアの面では、マイクロ波共振器に改良の余地があり、画像再構成においては、解像度の向上が重要な課題であることが分かった。当初の研究目的、「脳科学研究に用いる実験小動物(マウス)の頭部を高感度かつ安定に測定できる電子スピン共鳴分光装置を実現し、生命科学研究に用いる磁気共鳴スペクトロスコピーに関する基礎科学を開拓する」はほぼ達成された。今...
  • 文部科学省:科学研究費補助金(基盤研究(A))
    研究期間 : 2002年 -2004年 
    代表者 : 内海 英雄, 輿石 一郎, 門司 晃, 井口 登與志, 安井 久喬, 竹下 彰, 古賀 登, 平田 拓
     
    多くの循環器系疾患の成因・進展に活性酸素・フリーラジカルが関与することが示唆されている。生体内での活性酸素・フリーラジカルの産生を無侵襲解析するために、ニトロキシルラジカルをスピンプローブ剤として生体計測電子スピン共鳴(ESR)法で解析する方法を開発し、シグナル減衰速度を活性酸素産生の指標として、多くの病態モデル動物で活性酸素・フリーラジカルの関与を明らかにしてきた。そこで本研究では、循環器系疾患である糖尿病や肥満のモデル動物における活性酸素産生を無侵襲測定した。糖尿病や肥満のモデル動物にニトロキシルラジカルであるカルバモイルプロキシルを尾静脈内投与して無侵襲計測したところ、対照群と比較してシグナル減衰速度が亢進し、その亢進はα-トコフェロールやSODにより抑制されたことから、モデル動物の血管内における活性酸素の産生が示唆された。また、この亢進はプロテインキナーゼC阻害剤CGP41251やNADPHオキシダーゼ阻害剤アポシニンにより抑制されたことから、活性酸素産生は血管内のNADPHオキシダーゼに由来する可能性が考えられた。疾患における活性酸素動態の画像解析を行う上で、その生成部位を特定の臓器・組織と対応付けることは不可欠であることから、ESRI/MRI融像システムを試作した。膜透過性の異なるニトロキシルラジカルをマウスに尾静脈内投与してESRI/MRI計測を行い、血管内のみ...
  • 文部科学省:科学研究費補助金(若手研究(B))
    研究期間 : 2002年 -2003年 
    代表者 : 平田 拓
     
    生命科学研究に用いることを目的、マイクロ波周波数1.1GHzの電子スピン共鳴分光装置の開発を行った。動物実験における深刻な問題は感度の不足と、動物の動きによる擾乱である。本研究では、電子スピン共鳴スペクトロスコピーの高感度化を目指し、以下の研究を行った。(1)自動マッチング制御と自動チューニング制御の相互干渉を無くすための非干渉化法を開発した。この技術は、2入力2出力のフィードバック制御系において、伝達関数行列を対角化することにより非干渉化を実現する物である。実際の回路実装では、反転増幅器の利得を調整し、二つのフィードバックループ間の干渉を補償した。マウスを用いた実験により、相互干渉がない場合に、より安定に計測がおこなえ、実験動物の動き(呼吸や心拍)に起因する雑音が抑圧できる事を実証した。その結果、信号対雑音比を改善する事ができ、高感度化に寄与することが示された。(2)連続波電子スピン共鳴スペクトロスピーでは、磁界変調と位相検波を用いて高感度計測を行っている。磁界変調により、制御回路の電位が影響を受け、ベースラインが変動するといった問題がある。そのため、磁界変調の影響が少ない、光デバイスを用いたマイクロ波共振器の共振周波数チューニング法を開発した。光ファイバーを介して、離れた場所にあるLEDの光強度により、共振器に結合されたループに接続された光導電セルのインピーダンスを制御し...
  • 文部科学省:科学研究費補助金(基盤研究(A))
    研究期間 : 2002年 -2003年 
    代表者 : 小野 光弘, 平田 拓, 下山 雄平, 赤塚 孝雄, 鈴木 洋介
     
    本研究では、脳機能解析のためのEPRイメージング装置の開発を目的とした。その中で、特に画像再構成の中心に位置する問題に取り組んだ。すなわち、最適な画像を得る事が出来るフィルタ関数の系統的な決定法について検討を行った。直接フーリエ変換再構成法において、周波数領域でフィルタ関数を決定する方法は、理にかなっているとともにフィルタ特性(特にカットオフ周波数)の影響を直感的に理解しやすいと言える。本研究で提案した手法は、シグナルの周波数スペクトラムに注目するものであり、ノイズを白色雑音として取り扱うことにより、信号対雑音比を最大とするようなカットオフ周波数を決定する事が可能となる。この手法による画像再構成の有用性は、より詳細かつ実際的なイメージングの場で検証されるべきであるが、基本的なコンセプトを確認することができたと言えよう。また、体積コイル(本研究ではループ・ギャップ共振器を用いた)を光素子を用いて共振周波数を遠隔操作可能にする技術を開発した。これは、可変容量コンデンサーの使用に際し問題となる、磁場変調による電磁誘導が少ないチューニング回路を実現した。自動チューニング制御を用いる事により計測の安定化と引き換えに感度の低下が発生する。感度の低下と自動制御による実効的な感度の向上が同時に存在するため、感度を向上させるための研究が必要である。脳機能解析のためのEPRイメージング装置の開発...
  • 文部科学省:科学研究費補助金(萌芽研究)
    研究期間 : 2002年 -2003年 
    代表者 : 内海 英雄, 山田 健一, 輿石 一郎, 平田 拓
     
    フリーラジカルの生成と種々の疾患の成因・進展との関連性を視覚的に解明する上で、プロトン・電子スピン二重共鳴画像解析によって臓器・組織位置とフリーラジカル分布を重畳することは非常に重要であると考えられるが、未だ試みられていなかった。そこで今回、二重共鳴画像解析システムを開発するに当たり、ESRI用のサドル型磁場変調コイルの内側にMRIラジオパルス波のソレノイド型受信コイル、さらにその内側にESRマイクロ波のパラレルコイル型共振コイルを備えた共振デバイスを製作した。本デバイスのパラレルコイル内における磁場均一性に関して、磁束密度の標準偏差は軸長方向、動径方向ともに平均値の5%程度であった。また、最も内側のパラレルコイルを外して生理食塩水のMR画像を取得したところ、設置した状態と比べて画像の形状、信号雑音比ともにほぼ同じであった。次に、4本の試験管に各々濃度の異なるニトロキシルラジカルを封入した擬似試料を作成し、本デバイスを用いてESRI計測したところ、その画像輝度はラジカル濃度に比例して増加しており、このESR画像における各中心間距離はMR画像及び実際の試料における距離と一致した。以上より、MRI、ESRIともに計測可能な共振デバイスの開発に成功し、本デバイスを用いてフリーラジカル分布情報と解剖学的情報との重畳が可能であることを示した。本システムを動物計測に応用し、画像化システム...
  • 文部科学省:科学研究費補助金(基盤研究(B))
    研究期間 : 2000年 -2002年 
    代表者 : 小野 光弘, 山本 哲也, 平田 拓, 下山 雄平, 鈴木 洋介
     
    FM(Frequency Modulation,周波数変調)-EPR(電子常磁性共鳴)装置の開発を行った。磁界変調による機械的振動等の問題がEPR計測に重大な影響を与えている場合、周波数変調法によるCW(連続波)-EPRはEPRスペクトラムを取得するための新しい手法となりえる可能性がある。また、周波数変調CW-EPR法は、磁気共鳴に関係する物理量をマイクロ波周波数に関する微分値として計測できる利点を有している。以下に、本研究プロジェクトで得られた成果を列挙し整理する。1)1.6MHz_の周波数偏移を用いて、DPPH(1,1-dipheny1-2-picrylhydrazyl)粉末のEPRスペクトラムの取得に成功した。これは、40.3mTの中心磁束密度に対して、57μT_の磁界変調に相当する。DPPHのEPR吸収スペクトラムの線幅と比較し、2/3程度の変調振幅である。2)共振周波数1.1GHzのチューナブル・サーフェイスコイル型共振器を周波数変調法で使用するため、高速で動作するよう付加回路の回路定数を調整した。3)システムバンド幅104kHzのATC(自動同調回路)システムを実現した。位相遅れはEPR信号取得のためのFM周波数1kHzにおいて0.3度であった。FM変調されたマイクロ波周波数を高速で追従することが可能なATCシステムが実現した。4)ベースライン...
  • 文部科学省:科学研究費補助金(奨励研究(A))
    研究期間 : 2000年 -2001年 
    代表者 : 平田 拓
     
    本年度は二つのサブ・プロジェクトを実施した。【サブプロジェクト3】自動マッチング制御回路の開発:高周波検波回路と作動増幅器から構成される自動マッチング制御回路を開発した。共振器の入力インピーダンスが50オームよりも大きい場合には、反射波は入射波と同じ位相を有するが、インピーダンスが50オームより小さい場合には入射波と180度異なる位相を持つ反射波が観測される。この反射波の位相を検出する事によりインピーダンス整合の状態を検出する。インピーダンス制御のための帰還制御回路の応答は、実験動物の動きよりも速く、ESR信号を得るための磁界変調周波数よりも低くなければいけない。マウスの心拍数は最高で毎分600回程度(10Hz相当)、磁界変調周波数は通常100kHzである。帰還制御のカットオフ周波数は1kHz程度で十分動物の動きによる擾乱を補償できると考えられる。昨年度開発したサーフェイスコイルと帰還制御システムを現有する1.1GHzスペクトロメーターにおいてテストを行なった。スピーカーに取り付けたアームの振動により実験動物の擾乱を模擬し、インピーダンス不整合が補償されることを実験的に確認した。この実験では、信号対雑音比が約2倍に改善された。【サブプロジェクト4】自動マッチング制御回路の安定性解析:開発した自動マッチング制御システムのブロックダイアグラムと数学的モデルを定式化した。モデルは、...
  • 文部科学省:科学研究費補助金(基盤研究(B))
    研究期間 : 1999年 -2001年 
    代表者 : 小野 光弘, 湯浅 哲也, 山本 哲也, 下山 雄平, 赤塚 孝雄, 平田 拓
     
    0.2テスラPEDRI(Proton Electron Double Resonance Imaging,プロトン・エレクトロン二重共鳴イメージング)用マイクロ波アプリケータを開発するための実験を行った。周波数はNMR 8MHz、EPR 5.6GHzである。NMR RFアプリケータはソレノイドコイル又はバードケージコイルを用いる。EPRマイクロ波アプリケータに要求される性能はCW 5W以上の耐電力があり、約10mm×20mmの平面に均一度の高い磁界を照射し得ることである。本研究では、マイクロ波磁界を上述の平面状試料に集中的に照射するために、アプリケータの基本型はTE_<10>方形導波管とし、(1)切り離し導波管、(2)フランジ付導波管、(3)格子終端 TE_<101>空胴共振器、(4)細隙開口導波管の開口部磁界分布を測定した。磁界のピックアップコイルは線径0.3mm、内径1mmの1巻きのコイルで、シュペルトップバランを備えている。実験の結果、次の事柄が明らかになった。(1)切り離し導波管について:導波管開口部中心では磁界強度が最大値の約10分の1程度と低く、導波管壁長辺の中心に磁界が集中し、分布が不均一であることが分かった。磁界の均一度を磁界の最小値/同最大値と定義すると、開口部では0.09、開口部外では0.45である。(2)フランジ付導波管:磁界均一度は、開口部において0....
  • 文部科学省:科学研究費補助金(奨励研究(A))
    研究期間 : 1998年 -1999年 
    代表者 : 平田 拓
     
    共振周波数と整合状態を電圧により制御可能なサーフェイスコイル型共振器を試作した(共振周波数は1.2GHz)。この共振器は、印加する電圧により約10MHzの範囲で共振周波数を制御することが可能である。通常のキャビティー共振器を使用した自動周波数制御では、搬送波周波数の0.1%程度の周波数調整しかできない。今回試作した共振器を使用すれば、搬送波周波数の約1%の範囲で共振周波数を制御することが可能である。共振周波数を電子的に制御するために、自動周波数制御回路を開発した。周波数の差を直流出力に変換する位相検波回路と可変容量ダイオードに印可する逆バイアスを制御する回路を製作した。実験的に共振器の共振周波数を擾乱し、それを安定化する性能試験を実施した。その結果、共振周波数可変範囲と同程度の周波数擾乱に対しては極めて安定的に自動周波数制御が行えることを確認した。実際のESRスペクトロメーターに共振器と制御システムを組み込み、従来のESRスペクトロメーターとの性能比較を行った。その結果、今回試作した電子同調サーフェイスコイル型共振器と自動周波数制御回路を組み合わせたシステムにおいて、従来システムに比べ信号対雑音比が約二倍改善された。今回の試作において、帰還制御回路の発振が観測された。制御性能を低下させず、発振を除去し制御回路の安定性を向上させることが今後の課題である。
  • 文部科学省:科学研究費補助金(国際学術研究)
    研究期間 : 1997年 -1998年 
    代表者 : 大嶋 重利, Chaloupka He, 楠 正暢, 平田 拓, 沢谷 邦男, 小野 光弘, Heintz Chalo
     
    超伝導フィルタ、アンテナに関して、ドイツ ブッパタール大学のProf.Heintz Chaloupkaと共同研究を行い、次の様な成果を得ている。1. 平成9年度楠 正暢助手がProf.Heintz Chaloupkaの研究室に3週間滞在し、超伝導フィルタの設計・試作に関して共同研究を行ってきた。山形大学では高温超伝導薄膜(YBa_2Cu_3O_7-δ)の作製とその評価、超伝導フィルタの設計について主に研究し、ドイツ ブッパタール大学では、超伝導フィルタの設計・試作・評価を主に研究した。2. 平成10年度Prof.Heintz Chaloupkaが山形大学工学部大嶋研究室に3週間滞在し、超伝導フィルタに関する共同研究を行った。Prof.Heintz Chaloupkaが山形大学に滞在している期間に、日独超伝導フィルタシンポジウムを開催し、Prof.Heintz Chaloupka、移動体通信先端技術研究所、松下電器、山形大学から最近の研究成果を発表してもらった。超伝導フィルタの開発を目的とした、山形大学とブッパタール大学との研究交流は、平成10年度以降も継続される。
  • 文部科学省:科学研究費補助金(基盤研究(C))
    研究期間 : 1997年 -1998年 
    代表者 : 臼杵 尚志, 平田 拓, 小野 光弘, 合田 文則, 前田 肇
     
    1、 L-バンドESR分光装置システムの設計設置ESR分光装置を用い、生体において精度の高い組織酸素分圧測定の可能な装置の開発、改良を行た。従来のループギャップ共振器で計測できない寸法の生体内の電子スピン共鳴計測をL-バンESR分光装置で行うのに最適なサーフェイスコイル型共振器の設計製作を山形大学工学部Dartmouth大学(米国)EPR研究所の研究グループと共同で開発した。2、 動物実験での組織酸素分圧の計測動物実験によりESRによるin vivoでの組織酸素分圧測定を行い、その有用性を明らかにした。マスの筋肉、肝臓、腫瘍とラットの脳、腎臓を対象としての組織酸素分圧の測定を行い、1)麻酔にる組織酸素分圧への影響。2)放射線および化学療法後の腫瘍の再酸素化。3)エンドトキシンシック時の腎臓の酸素分圧の変化を直接証明した。3、 臨床応用のための酸素高感受性ESRプローベの発見、開発ある種の炭化物質は酸素に対する感受性をもっており、これらは酸素高感受性ESRプローベとなうる。120種類の炭化物質のスクリーニングを現在までおこなった。現在2種類が臨床応用可能とえられの安全性と安定性の検討を行っている。また、ESRプローベの感受性の向上のためLouva大学(ベルギー)医化学研究室とプローベにポリマー加工する研究を共同ですすめている。4、 各種フリーラジカルの計測現在ヘモグロビンの一酸...
  • 文部科学省:科学研究費補助金(基盤研究(B))
    研究期間 : 1996年 -1998年 
    代表者 : 小野 光弘, 塙 政利, 平田 拓, 下山 雄平
     
    生体のin vivo(生きたままでの)電子常磁性共鳴(EPR)計測、とりわけラットのホールボディ計測の実現を目標として、350MHzパルスEPR装置の開発を行った。本研究で得られた成果をまとめると次の様になる。(1) 数値解析により、最適なパルス幅と共振器の共振尖鋭度Qは、緩和時定数T_2=10〜100nsの生体ラジカルに対して夫々10〜68ns、10〜60、T_2=100〜800nsの固体のラジカルに対して夫々68〜158ns、60〜280であることが分かった。(2) 試作した350MHzパルスEPR装置を用いて、γ線照射クオーツ粉末37.5gの電子スピンエコー(ESE)信号の受信に成功した。受信信号電圧はパルス間隔が1400〜1600nsにおいて3〜5mVであった。(3) 本研究で得たESE信号から、γ線照射クオーツの緩和時定数はT_2=778nsと推定される。これは我々の研究室で既に開発した1.3GHzパルスEPR装置による測定結果T_2=759nsに極めて近い値である。(4) 生体計測を行うために、今後共振器のQを更に下げる必要がある。
  • 文部科学省:科学研究費補助金(一般研究(B), 基盤研究(B))
    研究期間 : 1995年 -1997年 
    代表者 : 大嶋 重利, 神戸 士郎, 平田 拓, 楠 正暢
     
    スーパーゲイン小形超伝導アンテナに関して、次の4点を重点的に検討し成果を得た。1.マイクロ波帯で動作するパッチアンテナの設計法の確立マイクロ波帯で動作するアンテナを伝送線路モデルおよび市販の電磁界解析ソフトを用いて行った。共振周波数5GHz、入力インピーダンス50オームとなるパッチアンテナを設計し、その設計に基づき銅薄膜のアンテナを試作し、伝送線路モデルの有効性を確認した。2.超伝導アンテナの設計、試作、評価YBCO薄膜を用いてパッチアンテナを試作し、アンテナ特性を評価した。その結果、共振周波数はほぼ設計通りの値を示したが、入力インピーダンスは設計値よりも大きな値となった。この違いを、電磁界シュミレーションにより検討した結果、超伝導薄膜の表面抵抗が設計値よりも小さいためであることがわかった。超伝導アンテナの利得は金薄膜で作製したアンテナよりも数dB以上高いことが明らかとなった。3.アンテナ用超伝導薄膜の作製法の検討超伝導アンテナを作製する場合、比較的面積の広い薄膜が要求される。我々は、誘導コイル結合型マグネトロンスパッタリング法によりその作製を検討し、アンテナに使用できる薄膜の作製法を確立した。4.アレーアンテナの検討2素子、4素子のパッチアレーアンテナを設計、試作、評価を行った。その結果、素子数を増やす事により利得の増加があること、超伝導アレーアンテナは銅薄膜アレーアンテナ...
  • 文部科学省:科学研究費補助金(奨励研究(A))
    研究期間 : 1994年 -1994年 
    代表者 : 平田 拓
     
    1.電子スピン共鳴計測用-フェイスコイル型共振器の共振尖鋭度と充填率(試料内にある磁気エネルギーと共振器の蓄えるエネルギーの比)の評価を可能にするためにそれらの定式化を行った。その際、生体試料内で生じる電磁波の損失を表す等価的な抵抗の値を求めることを可能にした。2.1でおこなった定式化に基づいて数値計算を行えるようにし、電子スピン共鳴計測の際に得られる信号強度の推定を可能にした。3.数値計算と定式化の妥当性を検証するために、計算モデルと同様の共振器を試作し、実際の電子スピン共鳴計測を行った。その結果、実験結果と数値計算の結果が一致することを確認した。4.信号強度の評価法が妥当であることが確認できたので、その評価法を用いたサーフェイスコイル型共振器の設計指針を明らかにした。その結果、試料の寸法と媒質の物理定数が与えられたとき、サーフェイスコイル型共振器の全長が短いものほど大きな信号が得られること、並びに信号強度が最大となるようなサーフェイスコイルの寸法が存在することが明らかになった。この研究により、当初の予定通り信号強度を最大とするようにサーフェイスコイル型共振器を設計することが可能になった。

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  • バイオイメージング特論
    開講年度 : 2019年
    課程区分 : 修士課程
    開講学部 : 情報科学研究科
    キーワード : 磁気共鳴イメージング, ハードウエア, 画像再構成, 医療応用
  • バイオイメージング特論
    開講年度 : 2019年
    課程区分 : 修士課程
    開講学部 : 情報科学院
    キーワード : 磁気共鳴イメージング, ハードウエア, 画像再構成, 医療応用
  • バイオエンジニアリング特論
    開講年度 : 2019年
    課程区分 : 修士課程
    開講学部 : 情報科学研究科
    キーワード : 遺伝情報, genetic information, バイオインフォマティクス, bioinformatics, イメージング, imaging, 生体医工学, biomedical engineering, 細胞力学, cell mechanics
  • バイオイメージング特論
    開講年度 : 2019年
    課程区分 : 博士後期課程
    開講学部 : 情報科学研究科
    キーワード : 磁気共鳴イメージング, ハードウエア, 画像再構成, 医療応用
  • バイオイメージング特論
    開講年度 : 2019年
    課程区分 : 博士後期課程
    開講学部 : 情報科学院
    キーワード : 磁気共鳴イメージング, ハードウエア, 画像再構成, 医療応用
  • バイオエンジニアリング特論
    開講年度 : 2019年
    課程区分 : 博士後期課程
    開講学部 : 情報科学研究科
    キーワード : 遺伝情報, genetic information, バイオインフォマティクス, bioinformatics, イメージング, imaging, 生体医工学, biomedical engineering, 細胞力学, cell mechanics
  • 情報学Ⅰ
    開講年度 : 2019年
    課程区分 : 学士課程
    開講学部 : 全学教育
    キーワード : 情報活用,情報社会,情報科学
  • 電磁気学
    開講年度 : 2019年
    課程区分 : 学士課程
    開講学部 : 工学部
    キーワード : クーロンの法則,アンペアの法則,ファラデーの法則,変位電流,マクスウェルの方程式
  • 電気回路
    開講年度 : 2019年
    課程区分 : 学士課程
    開講学部 : 工学部
    キーワード : 線形回路、オームの法則、キルヒホフの法則、インピーダンス、過渡現象

大学運営

委員歴

  • 2018年07月 - 現在   International Society on Oxygen Transport to Tissue   Executive Committee Member
  • 2018年01月 - 2020年12月   International EPR (ESR) Society   Vice President (Asia-Pacific)
  • 2012年01月 - 2015年12月   電子スピンサイエンス学会   理事
  • 2008年01月 - 2009年12月   電子スピンサイエンス学会   理事


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