研究者業績

山口 匡

ヤマグチ タダシ  (Tadashi Yamaguchi)

基本情報

所属
千葉大学 フロンティア医工学センター 教授
(兼任)工学研究院 教授
(兼任)医学部附属病院 超音波センター 教授
学位
博士(工学)(千葉大学)

J-GLOBAL ID
200901007599937458
researchmap会員ID
1000357236

外部リンク


論文

 157
  • Kenji YOSHIDA, Masaaki Omura, Shinnosuke Hirata, Tadashi YAMAGUCHI
    Japanese Journal of Applied Physics 2025年3月7日  
    Abstract This study investigates the dependence of the translational velocity of lipid-coated microbubbles in an ultrasound field on the viscosity of the surrounding Newtonian fluid. Plane burst waves with a center frequency of 7.34 MHz were used to uniformly drive microbubbles with a radius of 1.4 ± 0.3 m (mean ± standard deviation) in a flow channel. Bubbles were detected using the Doppler method using pulse waves with a center frequency of 5.2 MHz, and the velocities of individual bubbles were analyzed by tracking them in consecutive images. Examinations were conducted at various viscosities from 1 to 3 mPa∙s. The experimentally determined velocity–viscosity relationship qualitatively agreed with numerical simulations. This was written as a power-law dependence and used as a calibration curve to evaluate the local viscosity coefficient for the trajectories of individual bubbles. We succeeded in demonstrating viscosity imaging by multiplying the obtained viscosity coefficient with the bubble trajectories, convoluted with the point spread function of ultrasound imaging.
  • Miyu Nagaoka, Koichi Ito, Shinnosuke Hirata, Kenji YOSHIDA, Tadashi YAMAGUCHI
    Japanese Journal of Applied Physics 2025年2月14日  査読有り最終著者責任著者
    Abstract We conducted a fundamental study to elucidate the relationship between acoustic and electrical properties in the context of liver steatosis. The speed of sound, attenuation coefficient, conductivity, and relative permittivity were measured in rat livers with varying degrees of fat deposition. Fat deposition result in a decrease in the speed of sound, an increase in the attenuation coefficient, and reductions in conductivity and relative permittivity. However, no linear correlation was observed between these properties and fat content or droplet size individually. However, a notable correlation between changes in acoustic and electrical properties was identified when the structural and organizational effects of fat were considered in combination. Especially, attenuation changes were found to correlate with corresponding changes in electrical properties. These findings underscore the importance of comprehensively considering structural factors, such as fat droplet size and distribution, to better understand the physical mechanisms underlying the relationship between acoustic and electrical properties.
  • Masaaki Omura, Kunimasa Yagi, Ryo Nagaoka, Kenji Yoshida, Tadashi Yamaguchi, Hideyuki Hasegawa
    Ultrasonics 149 107589-107589 2025年1月30日  査読有り
    Hemorheological properties, such as erythrocyte aggregation can be assessed by ultrasonic backscatter coefficient analysis. In this study, a data-acquisition sequence with dual-frequency (dual-f) excitation was proposed to expand the ultrasonic frequency bandwidth with high-frame-rate imaging. The approach was experimentally validated using ex vivo porcine blood measurements and in vivo human imaging. The center frequency of the excitation wave was alternated between 7.8 (f1) and 12.5 (f2) MHz in the frequency spectral analysis using the reference phantom method. The frequency spectra revealed that the dual-f sequence achieved a bandwidth of 4.5-15 MHz at -20 dB, almost equivalent to those achieved with conventional single-frequency excitation (5.0-15 MHz) with a short-duration wave at 10 MHz (mono-f) in reference media with the sufficient condition of signal-to-noise ratio. The aggregation and disaggregation states of porcine blood suspended in high-molecular-weight dextran were determined by the isotropic diameter and packing factor using the structure factor size estimator. The discrimination performance of the dual-f approach increased, owing to the broadband frequency responses, in contrast with the limited performance of mono-f due to a low signal-to-noise ratio. This approach incorporating dual-f sequence is beneficial for obtaining robustly frequency spectra of hemorheological properties from in vivo scenarios.
  • Akiho Isshiki, Kisako Fujiwara, Takayuki Kondo, Kenji Yoshida, Tadashi Yamaguchi, Shinnosuke Hirata
    Journal of Medical Ultrasonics 52(1) 5-15 2024年11月23日  査読有り
    Abstract Purpose Early detection and quantitative evaluation of liver steatosis are crucial. Therefore, this study investigated a method for classifying ultrasound images to fatty liver grades based on echo-envelope statistics (ES) and convolutional neural network (CNN) analyses. Methods Three fatty liver grades, i.e., normal, mild, and moderate-to-severe, were defined using the thresholds of the magnetic resonance imaging-derived proton density fat fraction (MRI-PDFF). There were 10 cases of each grade, totaling 30 cases. To visualize the texture information affected by the deposition of fat droplets within the liver, the maps of first- and fourth-order moments and the heat maps formed from both moments were employed as parametric images derived from the ES. Several dozen to hundreds of regions of interest (ROIs) were extracted from the liver region in each parametric image. A total of 7680 ROIs were utilized for the transfer learning of a pretrained VGG-16 and classified using the transfer-learned VGG-16. Results The classification accuracies of the ROIs in all types of the parametric images were approximately 46%. The fatty liver grade for each case was determined by hard voting on the classified ROIs within the case. In the case of the fourth-order moment maps, the classification accuracy of the cases through hard voting mostly increased to approximately 63%. Conclusions The formation of parametric images derived from the ES and the CNN classification of the parametric images were proposed for the quantitative diagnosis of liver steatosis. In more than 60% of the cases, the fatty liver grade could be estimated solely using ultrasound images.
  • Jungtaek Choi, Jeffrey A. Ketterling, Jonathan Mamou, Cameron Hoerig, Shinnosuke Hirata, Kenji Yoshida, Tadashi Yamaguchi
    Sensors 24(22) 7118-7118 2024年11月5日  査読有り最終著者責任著者
    The objective of this work is to address the need for versatile and effective tissue characterization in abdominal ultrasound diagnosis using a simpler system. We evaluated the backscattering coefficient (BSC) of several tissue-mimicking phantoms utilizing three different ultrasonic probes: a single-element transducer, a linear array probe for clinical use, and a laboratory-made annular array probe. The single-element transducer, commonly used in developing fundamental BSC evaluation methods, served as a benchmark. The linear array probe provided a clinical comparison, while the annular array probe was tested for its potential in high-frequency and high-resolution ultrasonic observations. Our findings demonstrate that the annular array probe meets clinical demands by providing accurate BSC measurements, showcasing its capability for high-frequency and high-resolution imaging with a simpler, more versatile system.

MISC

 569
  • 平井 一樹, 山口 匡, 神山 直久, 蜂屋 弘之
    電子情報通信学会技術研究報告. US, 超音波 105(619) 1-6 2006年2月28日  
    びまん性肝疾患の終末像である肝ガンによる死亡者数は年々増加傾向にあり,びまん性肝疾患の早期発見を可能とする定量評価法の開発が臨床から強く望まれている.我々はこれまでに,超音波を用いたびまん性肝疾患の定量評価法の開発を試みており,その一つとして超音波エコー信号の統計的性質を利用して線維組織構造を抽出するFSET(Fiber Structure Extraction Technique)処理を提案している.本報告では,超音波ビームが3次元的に広がっていることを考慮し,FSET処理における処理窓を従来の2次元のものから3次元に拡張することで処理精度の向上を試みた.計算機シミュレーションによって作成したエコーデータを用いてその効果の検証を行った結果,処理窓を3次元に拡張したことで,2次元のROIでは抽出できていなかった部分を3次元のROIによって抽出していることを確認した.さらに,ROIのフレーム方向のサイズを変化させた場合の構造物の変化を調べたところ,構造物によって連続性が最大となるROIサイズが異なることが分かった.
  • Hiroyuki Yamada, Masaaki Ebara, Tadashi Yamaguchi, Shinichirou Okabe, Hiroyuki Fukuda, Masaharu Yoshikawa, Takashi Kishimoto, Hisahiro Matsubara, Hiroyuki Hachiya, Hiroshi Ishikura, Hiromitsu Saisho
    Journal of Hepatology 44(1) 68-75 2006年1月  査読有り
    Background/Aims: Ultrasound is noninvasive and useful to evaluate liver disease despite its operator dependency. This pilot study was conducted to quantitatively assess liver fibrosis using ultrasound. Methods: Fibrosis extraction ratios (FER) (fiber volume/total volume) of ultrasound and histological images of 8 autopsy specimens were compared. We also compared FER of ultrasound images from clinical patients (n=79) with histological fibrosis stages. Results: In the autopsy study, FER correlation coefficient between histological images and ultrasound images was 0.992. Regarding clinical patients, there was sufficient evidence to indicate differences in the distributions of FER for each fibrosis stage (Kruskal-Wallis test P<0.0001). With FER cut-off to distinguish ≥F2 from F0 and F1 defined as mean plus standard deviation of F0 and F1, sensitivity, specificity, positive predictive value, negative predictive value, and likelihood ratio were 62, 75, 78, 57%, and 2.47, respectively. Regarding HCV cohort (n=44), they were 55, 87, 89, 50%, and 4.14, respectively. Areas under receiver operating characteristic curves were 0.78, 0.79, 0.83 and 0.83 for ≥F1, ≥F2, ≥F3 and =F4, respectively. Regarding HCV cohort, they were 0.74, 0.71, 0.79 for ≥F2, ≥3 and =4, respectively. Conclusions: The FER method has great potential for diagnosing liver fibrosis using ultrasound. © 2005 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.
  • 蜂屋 弘之, 山口 匡
    海洋音響学会誌 33(1) 17-24 2006年  
  • Nishihara Kuramitsu, Yamaguchi Tadashi, Hachiya Hiroyuki
    超音波エレクトロニクスの基礎と応用に関するシンポジウム講演論文集 27 387-388 2006年  
  • 蜂屋 弘之, 山口 匡
    海洋音響学会誌 33(1) 17-24 2006年  
    Development of coastal acoustic tomography is carried out as a long term measurement technique to get shallow water information. Since sound is propagated with reflection at sea bed and sea surface, it is important to estimate characteristics of sound propagation in shallow water. In this paper, we investigated the characteristic of the propagating sound wave using data of a reciprocal acoustic transmission experiment in Uchiura Bay. Direct wave was used to estimate travel time and amplitude variation. We estimated water temperature with high accuracy and observed that an amplitude fluctuation happened with a rapid change of travel time. We got basic acoustic characteristics of reciprocal transmission signals that are useful for temperature and current measurements in shallow water.
  • Yamaguchi Tadashi, Furihata Hiroyuki, Kamiyama Naohisa, Ae Lee Sung, Hachiya Hiroyuki
    超音波エレクトロニクスの基礎と応用に関するシンポジウム講演論文集 27 139-140 2006年  
  • 山口 匡, 蜂屋 弘之
    信号処理 10(1) 5-10 2006年1月  
  • YAMAGUCHI Tadashi, HIRAI Kazuki, AOKI Masami, MIYAGI Jin, SUZUKI Masahiko, MORIYA Hideshige, HACHIYA Hiroyuki
    超音波エレクトロニクスの基礎と応用に関するシンポジウム講演予稿集 26th 295-296 2005年11月16日  
  • 蜂屋 弘之, 山口 匡
    電子情報通信学会技術研究報告. US, 超音波 105(239) 19-24 2005年8月16日  
    沿岸域や湾のような浅海域の海洋情報は環境保全, 漁業などの面で需要が多く, 温度, 流速場の3次元構造を長期連続的に観測する浅海域海洋音響トモグラフィーの開発が行われている。浅海域における広域音響計測では, 深海域と異なり海底や海面で反射するなど, 浅海域特有の音波伝搬特性を把握することが重要である。本報告では, 静岡県三津湾沿岸での双方向音波伝搬実験で得られた信号から双方向の伝搬音波の伝搬時間差を高精度で評価した結果について述べる。広域での水温変化が検出され, さらに位相を用いた高精度な伝搬時間差評価より, 非常に小さな流速成分を安定に求めることができた
  • Yamaguchi Tadashi, Hirai Kazuki, Yamada Hiroyuki, EBARA Masaaki, HACHIYA Hiroyuki
    Japanese journal of applied physics. Pt. 1, Regular papers & short notes 44(6) 4615-4621 2005年6月30日  
  • 降籏 洋行, 山口 匡, 平井 一樹, 神山 直久, 蜂屋 弘之
    電子情報通信学会技術研究報告. US, 超音波 105(135) 27-32 2005年6月17日  
    現在, 医療現場では超音波診断装置の利点(非観血, 低侵襲, リアルタイム性)を活かした, びまん性肝疾患の定量診断法を実現することが強く望まれている.我々はこれまでに, 肝組織から得られるエコー信号の振幅分布特性に着目し, 統計的な信号処理を用いることで肝臓のRFエコー信号から特異な信号成分を抽出する手法を提案し, 病変組織と思われる情報を抽出してきたが, 抽出情報の物理的意味が明らかではなかった.そこで本研究では, 剖検肝試料を用いてin vitro実験を行い, 肝臓の病変組織とエコー信号からの抽出結果との関係について検証した.スライス方向に高密度でエコー信号を収集し, 同一の試料から複数毎の病理組織標本を作成し, エコー画像と病理組織画像からそれぞれ病変組織情報を抽出し, 両抽出結果から3次元像を構築した.両3次元像を用いて病変組織の抽出率及び構造の2つの観点から比較を行ったところ, 両者ともに高い相関が見られ, 提案手法の有効性を確認できた.
  • YAMAGUCHI Tadashi, HIRAI Kazuki, YAMADA Hiroyuki, EBARA Masaaki, HACHIYA Hiroyuki
    Japanese Journal of Applied Physics 44(6B) 4615-4621 2005年6月  
  • T Yamaguchi, K Hirai, H Yamada, M Ebara, H Hachiya
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS 44(6B) 4615-4621 2005年6月  
    It is very important to diagnose liver cirrhosis noninvasively and correctly. In our previous studies, we proposed a processing technique to detect changes in liver tissue in vivo. In this paper, we propose the evaluation of the relationship between liver disease and echo information using autopsy specimens of a human liver in vitro. It is possible to verify the function of a processing parameter clearly and to compare the processing result and the actual human liver tissue structure by in vitro experiment. In the results of our processing technique, information that did not obey a Rayleigh distribution from the echo signal of the autopsy liver specimens was extracted depending on changes in a particular processing parameter. The fiber tissue structure of the same specimen was extracted from a number of histological images of stained tissue. We constructed 3D structures using the information extracted from the echo signal and the fiber structure of the stained tissue and compared the two. By comparing the 3D structures, it is possible to evaluate the relationship between the information that does not obey a Rayleigh distribution of the echo signal and the fibrosis structure.
  • T Yamaguchi, K Hirai, H Yamada, M Ebara, H Hachiya
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS 44(6B) 4615-4621 2005年6月  
    It is very important to diagnose liver cirrhosis noninvasively and correctly. In our previous studies, we proposed a processing technique to detect changes in liver tissue in vivo. In this paper, we propose the evaluation of the relationship between liver disease and echo information using autopsy specimens of a human liver in vitro. It is possible to verify the function of a processing parameter clearly and to compare the processing result and the actual human liver tissue structure by in vitro experiment. In the results of our processing technique, information that did not obey a Rayleigh distribution from the echo signal of the autopsy liver specimens was extracted depending on changes in a particular processing parameter. The fiber tissue structure of the same specimen was extracted from a number of histological images of stained tissue. We constructed 3D structures using the information extracted from the echo signal and the fiber structure of the stained tissue and compared the two. By comparing the 3D structures, it is possible to evaluate the relationship between the information that does not obey a Rayleigh distribution of the echo signal and the fibrosis structure.
  • 山口 匡, 平井 一樹, 神山 直久, 山田 博之, 江原 正明, 蜂屋 弘之
    Journal of medical ultrasonics = 超音波医学 32 S306 2005年4月15日  
  • 小熊 一豪, 飯島 尋子, 森安 史典, 山口 匡, 神山 直久, 蜂屋 弘之, 平井 一樹, 吉田 昌弘, 釜本 寛之, 鈴木 史朗, 清水 雅文, 宮原 健夫, 横井 正人
    Journal of medical ultrasonics = 超音波医学 32 S410 2005年4月15日  
  • 山口 匡, 平井 一樹, 宮城 仁, 鈴木 昌彦, 守屋 秀繁, 蜂屋 弘之
    Journal of medical ultrasonics = 超音波医学 32 S563 2005年4月15日  
  • 山口 匡, 平井 一樹, 神山 直久, 山田 博之, 江原 正明, 蜂屋 弘之
    Japanese journal of medical ultrasonics = 超音波医学 32 S306 2005年4月15日  
  • 小熊 一豪, 飯島 尋子, 森安 史典, 山口 匡, 神山 直久, 蜂屋 弘之, 平井 一樹, 吉田 昌弘, 釜本 寛之, 鈴木 史朗, 清水 雅文, 宮原 健夫, 横井 正人
    Japanese journal of medical ultrasonics = 超音波医学 32 S410 2005年4月15日  
  • 山口 匡, 平井 一樹, 宮城 仁, 鈴木 昌彦, 守屋 秀繁, 蜂屋 弘之
    Japanese journal of medical ultrasonics = 超音波医学 32 S563 2005年4月15日  
  • 山口 匡, 大泉 貴之, 平井 一樹, 神山 直久, 蜂屋 弘之
    日本音響学会研究発表会講演論文集 2005(1) 723-724 2005年3月8日  
  • 山口 匡, 畦上 友美, 平井 一樹, 守屋 秀繁, 蜂屋 弘之
    電子情報通信学会技術研究報告. US, 超音波 104(704) 7-12 2005年3月3日  
    人工膝関節置換術後の重大な合併症として下肢深部静脈血栓症及びこれに伴う肺血栓塞栓症がある.これらは施術中に発生する血栓などの塞栓子が引き起こす疾患であるため, 塞栓子の流量や流れの様子を知ることが, 治療及び予防において重要とされている.そこで本研究では, 人工膝関節置換術直後に取得した経食道心エコー画像に対してFSET(Fiber Structure Extraction Technique)処理を適用することにより, 画像中から心腔を流れる塞栓子情報の抽出を行い, その経時変化を観察した.
  • S Matsumoto, H Ueno, S Hosokawa, T Kitamura, M Miura-Mattausch, HJ Mattausch, T Ohguro, S Kumashiro, T Yamaguchi, K Yamashita, N Nakayama
    IEICE TRANSACTIONS ON ELECTRONICS E88C(2) 247-254 2005年2月  
    A systematic experimental and modeling study is reported. which characterizes the low-frequency noise spectrum of 100 nm-MOSFETs accurately. Two kinds of measured spectra are observed: 1/f and non-1/f spectra. The non-1/f spectrum is analysed by forward and backward measurements with exchanged source and drain, and shown to be due to a randomly distributed inhomogeneity of the trap density along the channel and within the gate oxide. By averaging the spectra of identical MOSFETs on a wafer the measured non-1/f noise spectra reduce to a 1/f characteristics. On the basis of these measurement data a noise model for circuit simulation is developed. which reproduces the low-frequency noise spectrum with a single model parameter for all gate lengths and under any bias conditions.
  • 信学技報 US2005(20) 27-32 2005年  
  • YAMAGUCHI Tadashi, HIRAI Kazuki, AOKI Masami, MIYAGI Jin, SUZUKI Masahiko, MORIYA Hideshige, HACHIYA Hiroyuki
    超音波エレクトロニクスの基礎と応用に関するシンポジウム講演論文集 26 295-296 2005年  
  • 山口 匡
    信号処理 9(1) 35-40 2005年1月  
  • 蜂屋 弘之, 山口 匡
    超音波エレクトロニクスの基礎と応用に関するシンポジウム講演論文集 26 179-180 2005年  
  • O Pagamjav, T Sakata, T Matsumura, T Yamaguchi, H Fukushi
    MICROBIOLOGY AND IMMUNOLOGY 49(2) 167-179 2005年  
    Equine herpesvirus 1 (EHV-1) is a pathogen causing rhinopneumonia in young horses, abortion in mares, and myeloencephalitis in adult horses. Two types, EHV-1 P and EHV-1 B, have recently been dominant among 16 electropherotypes. EHV-1 P and EHV-1 B viruses were compared by long and accurate polymerase chain reaction (LA-PCR) and restriction fragment length polymorphism (RFLP) analysis. Differences in restriction sites were found to be focused in ORF64, which encodes the infected cell protein 4 (ICP4), and downstream of the ICP4 gene. The 3'-end and downstream of ICP4 gene of EHV-1 B were found to be replaced by the corresponding region of EHV-4, indicating that EHV-1 B is a naturally occurring recombinant virus between progenitors of EHV-1 P and EHV-4. This is the first report showing a natural interspecies recombinant in alphaherpesviruses.
  • H Ogawa, T Yamaguchi, H Fukushi
    MICROBIOLOGY AND IMMUNOLOGY 49(3) 227-237 2005年  
    Two common viral diseases in psittacine birds including budgerigar fledgling disease (BFD), generally called avian polyomavirus (APV) infection, and psittacine beak and feather disease (PBFD) have similar clinical manifestations characterized by feather disorders. A duplex shuttle PCR was developed for detection of APV and PBFD virus (PBFDV). Two pairs of oligonucleotide primers were designed to amplify a 298-bp fragment of the t/T antigen region of APV genome and a 495-bp fragment of the capsid protein region encoded by open reading frame (ORF) C1 of PBFDV genome, respectively. In the present study, APV and PBFDV were detected simultaneously in one tube by duplex shuttle PCR using these two pairs of primers. The detection limits were 2 viral copies of APV and 3 viral copies of PBFDV. In the clinical application, we detected 16 APV-positive, 15 PBFDV-positive, and 3 mixed infected samples in 39 samples examined. Sequences of the amplified products were read. The t/T antigen region was conserved in the APV-positive samples as expected. ORF C1 of PBFDV genome showed diversity. Phylogenic analysis indicated that PBFDV ORF C1 consisted of 6 clusters which were related to subfamilies of psittacine birds. Our duplex shuttle PCR could be a useful method for differential diagnosis and molecular epidemiology of BFD and PBFD.
  • T Okumura, J Akiyama, S Maeda, T Yamaguchi, A Takahashi
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 43(10) 7097-7101 2004年10月  
    Adaptive equalization is essential in achieving wider system margins, such as tilt margin and defocus margin, in optical disk systems using partial response maximum likelihood (PRML) detection method. The most conventional method is the combination of the use of the least-mean-squares (LMS) algorithm and partial response (PR) equalization, but it does not optimize the characteristics of equalizers in terms of bit error rate (BER) performance. Integrating the concept of sequenced amplitude margin (SAM) with LMS, we developed a new adaptive equalization method, called least-mean-squared SAM error (LMSAM), which can minimize BER. After explaining the basic idea of LMSAM, we theoretically derived its implementable algorithm. We also reported favorable experimental results on the remarkable improvement of the tangential tilt margin and defocus margin with LMSAM. Furthermore, we analyzed the result from the viewpoint of frequency response and clarified why LMSAM can improve tilt margin.
  • 平井 一樹, 山口 匡, 蜂屋 弘之
    電子情報通信学会技術研究報告. US, 超音波 104(142) 23-28 2004年6月18日  
    我々はこれまでに,超音波エコーを用いて,慢性肝炎・肝硬変などのびまん性肝疾患を対象とした定量的な評価法の検討を試みてきた.その手法はエコー信号の振幅特性に着目したもので,振幅分布特性解析および非正常組織情報の抽出の2つの解析処理を用いている.本報告では,これらの解析処理をシミュレーションデータおよび臨床データに対して行うことで,用いた解析処理の有効性・妥当性について検討した。また,用いた指標の相関性を検討したところ,両者にはよい相関があるが,正常肝臓に対して異なる特性があることがわかった。さらに,病変進行に伴う組織構造の変化に処理結果がどのように反応しているのか,ROI中のエコー情報にどの程度の組織性状・構造が反映されているかを,総計情報の2次元分布を求めることで検討し,臨床データで安定な結果を得るための知見を得た.
  • 小熊 一豪, 飯島 尋子, 山口 匡, 神山 直久, 深町 桂一, 吉田 昌弘, 鈴木 史朗, 清水 雅文, 横井 正人, 釜本 寛之, 杉本 勝俊, 目時 亮, 蜂屋 弘之, 森安 史典
    Journal of medical ultrasonics = 超音波医学 31 S179 2004年4月15日  
  • 陳 勇, 山口 匡, 山田 博之, 江原 正明, 蜂屋 弘之
    日本音響学会研究発表会講演論文集 2004(1) 1011-1012 2004年3月17日  
  • H Hachiya, T Yamaguchi
    ADVANCES IN NONDESTRUCTIVE EVALUATION, PT 1-3 270-273 2085-2092 2004年  
    The medical diagnosis using the ultrasonic cross section image has made remarkable result, and the ultrasonic diagnostic equipment is widely used. However, experience and skill of the doctor are required for the diagnosis using the ultrasonic image. We have been developing quantitative diagnostic techniques of liver diseases which can be applied to the clinical field. In this paper, we present the quantitative estimation results of diffused liver diseases. In the normal liver, many scatterers are distributed randomly, and the cross-section image obtained using an ultrasonic imaging system has many granular patterns referred to as a speckle pattern. The probability density function of the echo amplitude from the normal livers agrees well with the Rayleigh distribution function. The cirrhotic liver has many fibrotic tissue structures known as nodule structures. This echographic pattern changes with the progression of a disease such as cirrhosis. Using the processing technique that can suppress the signals from the randomly distributed scatterers which correspond to the normal liver, we extracted the quantitative information of the diseased tissue from RF echo signal of liver cirrhosis and chronic hepatitis.
  • 平井 一樹, 山口 匡, 江原 正明, 山田 博之, 蜂屋 弘之
    超音波エレクトロニクスの基礎と応用に関するシンポジウム講演論文集 25 381-382 2004年  
  • M Andoh, T Naganawa, T Yamaguchi, H Fukushi, K Hirai
    MICROBIOLOGY AND IMMUNOLOGY 48(9) 661-664 2004年  
    Coxiella burnetti is the agent of the worldwide zoonosis, Q fever. The in vitro susceptibility to tetracycline and fluoroquinolones of Japanese isolates of C burnetii was evaluated for the first time. The MICs against Japanese isolates were almost the same as the MICs against the foreign reference isolates. The results suggest that the common antibiotics therapy for Q fever used in other countries is also effective for Japanese Q fever patients.
  • ESM Ibrahim, O Pagmajav, T Yamaguchi, T Matsumura, H Fukushi
    MICROBIOLOGY AND IMMUNOLOGY 48(11) 831-842 2004年  
    Nucleotide sequences of the intergenic region between ORF 62 and ORF 63 of equine herpesvirus 1 (EHV-1) isolates were analyzed. The sequences of this region consisted of variable and conserved domains among EHV-1 isolates. An EHV-1 mutant, Ab4-GFP, was constructed by inserting a green fluorescent protein (GFP) expression cassette flanked by loxP at both ends into the intergenic region between ORF 62 and ORF 63. Another mutant, Ab4-loxP, which contains one loxP site, was constructed by excision of the GFP cassette from the Ab4-GFP virus genome by cre enzyme. The recombinant Ab4-GFP formed smaller plaques than the wild type in MDBK cells. Virus production also decreased for Ab4-GFP in multistep growth analyses. Virulence of Ab4-GFP in both mice and hamsters was weaker than that of the wild type. Ab4-loxP exhibited properties similar to those of the wild type. These results suggest that the intergenic region between ORF 62 and ORF 63 plays various roles in the virus growth.
  • M Andoh, H Nagaoka, T Yamaguchi, H Fukushi, K Hirai
    MICROBIOLOGY AND IMMUNOLOGY 48(12) 971-975 2004年  
    The genetic variation of Japanese isolates of Coxiella burnetii, the agent of Q fever, was found for the first time. Forty-nine out of 72 isolates had the chronic pattern of the isocitrate hydrogenase gene. Sequence analysis revealed that the isolates have a specific nucleotide sequence. The putative amino acid sequence was the same as that of chronic reference strains. These results suggest the variation of C. burnetii isolates in Japan.
  • 熊 剣波, 陳 勇, 山口 匡, 神山 直久, 蜂屋 弘之
    日本音響学会研究発表会講演論文集 2003(2) 1151-1152 2003年9月17日  
  • 陳 勇, 熊 剣波, 山口 匡, 神山 直久, 蜂屋 弘之
    日本音響学会研究発表会講演論文集 2003(2) 1167-1168 2003年9月17日  
  • 深町 桂一, 山口 匡, 神山 直久, 蜂屋 弘之
    日本音響学会研究発表会講演論文集 2003(2) 1169-1170 2003年9月17日  
  • 陳 勇, 熊 剣波, 山口 匡, 江原 正明, 蜂屋 弘之
    電子情報通信学会技術研究報告. US, 超音波 103(158) 35-40 2003年6月21日  
    本研究では,エコー信号の振幅特性を用いた組織性状診断法を確立するために,生体組織の音響特性と組織の物理的・化学的構造変化の関係を考慮し,複数のアプローチで検証を行っている。生体から摘出した6例の硬変肝剖検試料を対象とし,水槽実験において収集した200枚のエコー信号において非レイリー分布となる情報のみを抽出し,3次元構造を構築した結果,複数の線状の構造物が確認された。また,エコー信号を収集後に組織切片を作成し,超音波顕微鏡を用いて生体音響特性(音速・減衰)を計測した結果,正常肝及び結節組織に比較して線描組織では分散が大きいことが確認された。生体組織構造を詳細に把握するために,剖検試料から複数の病理組織写真を作成し,染色情報を元に線維組織構造を3次元で再構築し,エコー信号の処理結果及び生体音響特性の計測結果と比較したところ,エコー信号から得られた線状の構造物及び減衰が大きい部位が繊維部であることが確認された。
  • K Yamazaki, T Yamaguchi, H Namatsu
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 42(6B) 3833-3837 2003年6月  
    A novel method of electron-beam (EB) writing to reduce line-edge roughness (LER) called edge-enhancement writing (EEW) is described. EEW involves writing a fine line along a pattern edge at a high dose. This provides a steep profile of the energy deposited at the edge. The high exposure dose breaks up aggregates of resist polymer at the edge, which cause LER. Moreover, in EEW the background energy in unexposed regions due to proximity effects is also reduced by control of the dose. This increases the energy contrast at the edge, thereby preventing the appearance of aggregates on the sidewall due to undesired dissolution of the edge region. The resulting energy profile is quite different from that obtained with conventional proximity effect corrections. Experimental results and simulations of the deposited energy profile have demonstrated the effectiveness of EEW.
  • Yamaguchi Tadashi, Nakamura Keigo, Hachiya Hiroyuki
    Japanese journal of applied physics. Pt. 1, Regular papers & short notes 42(5) 3292-3298 2003年5月30日  
    Ultrasonic B-mode images are affected by changes in scatterer distribution. It is hard to estimate the relationship between the ultrasonic image and the tissue structure quantitatively because we cannot observe the continuous stages of liver cirrhosis tissue clinically, particularly the beginning stage. In this paper, we propose a three-dimensional modeling method of scatterer distribution for normal and cirrhotic livers to confirm the influence of the change in the form of scatterer distribution on echo information. The algorithm of the method includes parameters which determine the expansion of nodules and fibers. Using the B-mode images which are obtained from these scatterer distributions, we analyze the relationship between the changes in the form of biological tissue and the changes in the B-mode images during progressive liver cirrhosis.
  • YAMAGUCHI T, NAKAMURA K, HACHIYA H
    Japanese Journal of Applied Physics 42(5B) 3292-3298 2003年5月  
  • Tadashi Yamaguchi, Keigo Nakamura, Hiroyuki Hachiya
    Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers 42 3292-3298 2003年5月1日  
    Ultrasonic B-mode images are affected by changes in scatterer distribution. It is hard to estimate the relationship between the ultrasonic image and the tissue structure quantitatively because we cannot observe the continuous stages of liver cirrhosis tissue clinically, particularly the beginning stage. In this paper, we propose a three-dimensional modeling method of scatterer distribution for normal and cirrhotic livers to confirm the influence of the change in the form of scatterer distribution on echo information. The algorithm of the method includes parameters which determine the expansion of nodules and fibers. Using the B-mode images which are obtained from these scatterer distributions, we analyze the relationship between the changes in the form of biological tissue and the changes in the B-mode images during progressive liver cirrhosis.
  • 蜂屋 弘之, 山口 匡
    Medical imaging technology 21(2) 95-100 2003年3月25日  

講演・口頭発表等

 449

担当経験のある科目(授業)

 20

共同研究・競争的資金等の研究課題

 44

社会貢献活動

 53