96 results on '"Atsushi Takemura"'
Search Results
2. Data from E7386, a Selective Inhibitor of the Interaction between β-Catenin and CBP, Exerts Antitumor Activity in Tumor Models with Activated Canonical Wnt Signaling
- Author
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Yoichi Ozawa, Yasuhiro Funahashi, Takashi Owa, Hiroyuki Kouji, Kenichi Nomoto, Tomohiro Matsushima, Junji Matsui, Toshimitsu Uenaka, Akihiko Tsuruoka, Masao Iwata, Takenao Odagami, Masayuki Matsukura, Akira Yokoi, Taro Semba, Yu Kato, Kenji Kubara, Naomi Wakayama, Ikuo Kushida, Atsushi Takemura, Naoki Yoneda, Hitoshi Harada, Kazutaka Nakamoto, Masahiro Matsuki, Junichi Ito, Mai Uesugi, Takayuki Kimura, Atsumi Yamaguchi, Hiroshi Kamiyama, Kentaro Iso, Yuji Yamamoto, Satoshi Inoue, Yusaku Hori, and Kazuhiko Yamada
- Abstract
The Wnt/β-catenin signaling pathway plays crucial roles in embryonic development and the development of multiple types of cancer, and its aberrant activation provides cancer cells with escape mechanisms from immune checkpoint inhibitors. E7386, an orally active selective inhibitor of the interaction between β-catenin and CREB binding protein, which is part of the Wnt/β-catenin signaling pathway, disrupts the Wnt/β-catenin signaling pathway in HEK293 and adenomatous polyposis coli (APC)-mutated human gastric cancer ECC10 cells. It also inhibited tumor growth in an ECC10 xenograft model and suppressed polyp formation in the intestinal tract of ApcMin/+ mice, in which mutation of Apc activates the Wnt/β-catenin signaling pathway. E7386 demonstrated antitumor activity against mouse mammary tumors developed in mouse mammary tumor virus (MMTV)-Wnt1 transgenic mice. Gene expression profiling using RNA sequencing data of MMTV-Wnt1 tumor tissue from mice treated with E7386 showed that E7386 downregulated genes in the hypoxia signaling pathway and immune responses related to the CCL2, and IHC analysis showed that E7386 induced infiltration of CD8+ cells into tumor tissues. Furthermore, E7386 showed synergistic antitumor activity against MMTV-Wnt1 tumor in combination with anti-PD-1 antibody. In conclusion, E7386 demonstrates clear antitumor activity via modulation of the Wnt/β-catenin signaling pathway and alteration of the tumor and immune microenvironments, and its antitumor activity can be enhanced in combination with anti-PD-1 antibody.Significance:These findings demonstrate that the novel anticancer agent, E7386, modulates Wnt/β-catenin signaling, altering the tumor immune microenvironment and exhibiting synergistic antitumor activity in combination with anti-PD-1 antibody.
- Published
- 2023
3. Supplementary Tables from E7386, a Selective Inhibitor of the Interaction between β-Catenin and CBP, Exerts Antitumor Activity in Tumor Models with Activated Canonical Wnt Signaling
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Yoichi Ozawa, Yasuhiro Funahashi, Takashi Owa, Hiroyuki Kouji, Kenichi Nomoto, Tomohiro Matsushima, Junji Matsui, Toshimitsu Uenaka, Akihiko Tsuruoka, Masao Iwata, Takenao Odagami, Masayuki Matsukura, Akira Yokoi, Taro Semba, Yu Kato, Kenji Kubara, Naomi Wakayama, Ikuo Kushida, Atsushi Takemura, Naoki Yoneda, Hitoshi Harada, Kazutaka Nakamoto, Masahiro Matsuki, Junichi Ito, Mai Uesugi, Takayuki Kimura, Atsumi Yamaguchi, Hiroshi Kamiyama, Kentaro Iso, Yuji Yamamoto, Satoshi Inoue, Yusaku Hori, and Kazuhiko Yamada
- Abstract
Supplementary Table S1, Table S4, Table S5, Table S6, Table S7. Supplementary Table S1: The list of DEGs by nCounter analysis (|Fold change| > 1.25, P < 0.1). Supplementary Table S4: Top 10 enriched pathways identified by RNA-Seq analysis in MMTV-Wnt1 model. Supplementary Table S5: The result of CIBERSORT analysis. Supplementary Table S6: The lists of antibody for flow cytometry analysis. Supplementary Table S7: Comparison of Physicochemical property between E7386 and C-82.
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- 2023
4. Supplementary Materials and Methods from E7386, a Selective Inhibitor of the Interaction between β-Catenin and CBP, Exerts Antitumor Activity in Tumor Models with Activated Canonical Wnt Signaling
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Yoichi Ozawa, Yasuhiro Funahashi, Takashi Owa, Hiroyuki Kouji, Kenichi Nomoto, Tomohiro Matsushima, Junji Matsui, Toshimitsu Uenaka, Akihiko Tsuruoka, Masao Iwata, Takenao Odagami, Masayuki Matsukura, Akira Yokoi, Taro Semba, Yu Kato, Kenji Kubara, Naomi Wakayama, Ikuo Kushida, Atsushi Takemura, Naoki Yoneda, Hitoshi Harada, Kazutaka Nakamoto, Masahiro Matsuki, Junichi Ito, Mai Uesugi, Takayuki Kimura, Atsumi Yamaguchi, Hiroshi Kamiyama, Kentaro Iso, Yuji Yamamoto, Satoshi Inoue, Yusaku Hori, and Kazuhiko Yamada
- Abstract
Supplementary Materials and Methods
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- 2023
5. Estimation of a log-compressed Nakagami distribution and application to breast tumor discrimination in ultrasonic images.
- Author
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Atsushi Takemura
- Published
- 2009
6. MOBILE SYSTEM FOR SIMULATION OF PHYSICAL CIRCUIT OPERATION AND APPLICATION TO EDUCATION INVOLVING CIRCUIT CONSTRUCTION.
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Atsushi Takemura
- Subjects
MOBILE apps ,ELECTRONIC circuits ,INTEGRATED circuits ,IMAGE processing ,LEARNING - Abstract
This study proposes a mobile education system for learning experiments involving the design and construction of electronic circuits. The proposed system utilizes novel image processing techniques that employ a machine learning algorithm to automatically recognize the composition of a wide variety of circuits and translate that composition into a standard circuit description language (e.g., simulation program with integrated circuit emphasis (SPICE)). This feature enables a learner to examine and learn the functionality of the constructed physical circuit using a mobile PC. Moreover, the proposed system discovers the errors and inappropriate parts in a constructed circuit that could cause accidents and instruct to correct them. The effectiveness of the proposed system was verified in actual classes by 60 undergraduates. The comparison tests between two groups that comprised students who used or did not use the proposed system demonstrated the effectiveness of the system. [ABSTRACT FROM AUTHOR]
- Published
- 2023
7. E7386, a Selective Inhibitor of the Interaction between β-Catenin and CBP, Exerts Antitumor Activity in Tumor Models with Activated Canonical Wnt Signaling
- Author
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Masao Iwata, Masayuki Matsukura, Takenao Odagami, Kenichi Nomoto, Atsushi Takemura, Kenji Kubara, Hiroshi Kamiyama, Naoki Yoneda, Tomohiro Matsushima, Junji Matsui, Yuji Yamamoto, Yasuhiro Funahashi, Satoshi Inoue, Kentaro Iso, Naomi Wakayama, Atsumi Yamaguchi, Toshimitsu Uenaka, Takayuki Kimura, Kazuhiko Yamada, Akira Yokoi, Yoichi Ozawa, Masahiro Matsuki, Yusaku Hori, Takashi Owa, Hiroyuki Kouji, Junichi Ito, Ikuo Kushida, Kazutaka Nakamoto, Hitoshi Harada, Mai Uesugi, Yu Kato, Taro Semba, and Akihiko Tsuruoka
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0301 basic medicine ,Genetically modified mouse ,Cancer Research ,Genes, APC ,Adenomatous polyposis coli ,Sialoglycoproteins ,Mice, Nude ,Antineoplastic Agents ,Mice, Transgenic ,Wnt1 Protein ,Mice ,03 medical and health sciences ,0302 clinical medicine ,Immune system ,Neoplasms ,Animals ,Humans ,Wnt Signaling Pathway ,Cells, Cultured ,beta Catenin ,Cell Proliferation ,biology ,Triazines ,Chemistry ,Mouse mammary tumor virus ,Wnt signaling pathway ,biology.organism_classification ,Peptide Fragments ,Mice, Inbred C57BL ,Disease Models, Animal ,HEK293 Cells ,030104 developmental biology ,Oncology ,Pyrazines ,030220 oncology & carcinogenesis ,Catenin ,Cancer cell ,Cancer research ,biology.protein ,Female ,Signal transduction ,Protein Binding - Abstract
The Wnt/β-catenin signaling pathway plays crucial roles in embryonic development and the development of multiple types of cancer, and its aberrant activation provides cancer cells with escape mechanisms from immune checkpoint inhibitors. E7386, an orally active selective inhibitor of the interaction between β-catenin and CREB binding protein, which is part of the Wnt/β-catenin signaling pathway, disrupts the Wnt/β-catenin signaling pathway in HEK293 and adenomatous polyposis coli (APC)-mutated human gastric cancer ECC10 cells. It also inhibited tumor growth in an ECC10 xenograft model and suppressed polyp formation in the intestinal tract of ApcMin/+ mice, in which mutation of Apc activates the Wnt/β-catenin signaling pathway. E7386 demonstrated antitumor activity against mouse mammary tumors developed in mouse mammary tumor virus (MMTV)-Wnt1 transgenic mice. Gene expression profiling using RNA sequencing data of MMTV-Wnt1 tumor tissue from mice treated with E7386 showed that E7386 downregulated genes in the hypoxia signaling pathway and immune responses related to the CCL2, and IHC analysis showed that E7386 induced infiltration of CD8+ cells into tumor tissues. Furthermore, E7386 showed synergistic antitumor activity against MMTV-Wnt1 tumor in combination with anti-PD-1 antibody. In conclusion, E7386 demonstrates clear antitumor activity via modulation of the Wnt/β-catenin signaling pathway and alteration of the tumor and immune microenvironments, and its antitumor activity can be enhanced in combination with anti-PD-1 antibody. Significance: These findings demonstrate that the novel anticancer agent, E7386, modulates Wnt/β-catenin signaling, altering the tumor immune microenvironment and exhibiting synergistic antitumor activity in combination with anti-PD-1 antibody.
- Published
- 2021
8. Historical review of NOM (News of Osaka Micropaleontologists), Japanese Radiolarian Symposium and InterRad Meeting
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Atsushi Takemura
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History ,General Materials Science - Published
- 2019
9. Improved Visualization of Middle Ear Cholesteatoma with Computed Diffusion-weighted Imaging
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Akio Hiwatashi, Kouji Kobayashi, Osamu Togao, Koji Yamashita, Hiroshi Honda, Kazufumi Kikuchi, Yamato Shimomiya, Nozomu Matsumoto, Ryotaro Kamei, Taro Takahara, Atsushi Takemura, Thomas C. Kwee, Daichi Momosaka, Guided Treatment in Optimal Selected Cancer Patients (GUTS), and Basic and Translational Research and Imaging Methodology Development in Groningen (BRIDGE)
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Adult ,Male ,Adolescent ,Noise reduction ,TURBO SPIN-ECHO ,Image processing ,PLANAR ,030218 nuclear medicine & medical imaging ,Young Adult ,03 medical and health sciences ,0302 clinical medicine ,Nuclear magnetic resonance ,Signal-to-noise ratio ,Image Processing, Computer-Assisted ,Technical Note ,diffusion weighted imaging ,medicine ,Humans ,magnetic resonance imaging ,Middle Ear Cholesteatoma ,Effective diffusion coefficient ,Radiology, Nuclear Medicine and imaging ,cholesteatoma ,Aged ,Cholesteatoma, Middle Ear ,business.industry ,SINGLE-SHOT ,Cholesteatoma ,Middle Aged ,medicine.disease ,Noise ,Diffusion Magnetic Resonance Imaging ,middle ear ,Female ,signal-to-noise ratio ,business ,Algorithms ,030217 neurology & neurosurgery ,Diffusion MRI - Abstract
Computed DWI (cDWI) is a mathematical technique that calculates arbitrary higher b value images from at least two different lower b values. In addition, the removal of high intensity noise with image processing on cDWI could improve cholesteatoma-background contrast-to-noise ratio (CNR). In the present study, noise reduction was performed by the cut-off values of apparent diffusion coefficient (ADC) less than 0 and 0.4 x 10(-3) s/mm(2). The cholesteatoma to non-cholesteatoma CNR was increased using a noise reduction algorithm for clinical setting.
- Published
- 2019
10. LEARNING SYSTEM USING CROSS REALITY TECHNIQUE FOR PHYSICAL ELECTRONIC CIRCUIT CONSTRUCTION AND VIRTUAL MID-AIR OPERATIONS.
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Atsushi Takemura
- Subjects
SCIENCE education ,VIRTUAL reality ,ELECTRONIC circuits ,DIGITAL learning ,LEARNING ability - Abstract
Science and technology education necessitates teaching and learning experiments involving electronic circuit construction and measurements using experimental equipment. In this study, a novel cross reality system for learning physical circuit construction and performing virtual experiments using virtual experimental equipment with mid-air haptics is proposed. The proposed system possesses a technical novelty that enables a learner to operate virtual equipment with the same motions of his hand and fingers as the operations of the real equipment. An evaluation test using 150 patterns of virtual experiments verified the proposed system's effectiveness. [ABSTRACT FROM AUTHOR]
- Published
- 2022
11. Devonian chert in the Permian Kozuki Formation of the Ultra-Tamba Zone, eastern Okayama Prefecture, Southwest Japan
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Hikaru Ueno, Shizuo Takemura, Yoshiaki Sugamori, Atsushi Takemura, and Hiroshi Furutani
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Thesaurus (information retrieval) ,Paleontology ,Permian ,General Engineering ,General Earth and Planetary Sciences ,Geology ,Devonian ,General Environmental Science - Published
- 2018
12. Single-Breath-Hold Whole-heart Unenhanced Coronary MRA Using Multi-shot Gradient Echo EPI at 3T: Comparison with Free-breathing Turbo-field-echo Coronary MRA on Healthy Volunteers
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Yasuyuki Yamashita, Tomohiro Namimoto, Daisuke Utsunomiya, Hideaki Yuki, Masafumi Kidoh, Kenichiro Hirata, Seitaro Oda, Mika Kitajima, Takeshi Nakaura, Atsushi Takemura, Yasunori Nagayama, Yoshinori Funama, Tomoyuki Okuaki, Yuji Iyama, and Kosuke Morita
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Image quality ,media_common.quotation_subject ,men ,Magnetic resonance angiography ,030218 nuclear medicine & medical imaging ,Breath Holding ,03 medical and health sciences ,0302 clinical medicine ,medicine ,Image noise ,Humans ,magnetic resonance imaging ,Contrast (vision) ,Radiology, Nuclear Medicine and imaging ,media_common ,Artifact (error) ,medicine.diagnostic_test ,Echo-Planar Imaging ,business.industry ,Heart ,Magnetic resonance imaging ,Single breath ,Signal-to-noise ratio (imaging) ,coronary angiography ,Artifacts ,business ,Nuclear medicine ,Magnetic Resonance Angiography ,Major Paper ,respiration ,030217 neurology & neurosurgery - Abstract
Purpose: We investigated the feasibility of single breath hold unenhanced coronary MRA using multi-shot gradient echo planar imaging (MSG-EPI) on a 3T-scanner. Methods: Fourteen volunteers underwent single breath hold coronary MRA with a MSG-EPI and free-breathing turbo field echo (TFE) coronary MRA at 3T. The acquisition time, signal to noise ratio (SNR), and the contrast of the sequences were compared with the paired t-test. Readers evaluated the image contrast, noise, sharpness, artifacts, and the overall image quality. Results: The acquisition time was 88.1% shorter for MSG-EPI than TFE (24.7 ± 2.5 vs 206.4 ± 23.1 sec, P < 0.01). The SNR was significantly higher on MSG-EPI than TFE scans (P < 0.01). There was no significant difference in the contrast on MSG-EPI and TFE scans (1.8 ± 0.3 vs 1.9 ± 0.3, P = 0.24). There was no significant difference in image contrast, image sharpness, and overall image quality between two scan techniques. The score of image noise and artifact were significantly higher on MSG-EPI than TFE scans (P < 0.05). Conclusion: The single breath hold MSG-EPI sequence is a promising technique for shortening the scan time and for preserving the image quality of unenhanced whole heart coronary MRA on a 3T scanner.
- Published
- 2018
13. Progressive development of ocean anoxia in the end-Permian pelagic Panthalassa
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Takaaki Itai, Yoshiaki Aita, Hamish J. Campbell, Paul B. Wignall, Rie S. Hori, Yijun Xiong, Satoshi Yamakita, Atsushi Takemura, Bernard K. Spörli, Simon W. Poulton, Satoshi Takahashi, and Minoru Ikehara
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Ocean deoxygenation ,Extinction event ,Global and Planetary Change ,Oceanography ,Water column ,Permian ,Isotopes of carbon ,Ocean current ,Seawater ,Weathering ,Geology - Abstract
The end-Permian mass extinction (EPME) has been linked with the widespread development of oxygen-poor oceanic conditions. However, information on the spatial extent of anoxia in the Panthalassa super-ocean has been limited. This study reports oceanic redox records from a deep-sea chert succession (the Waiheke 1 section, WHK 1, New Zealand) that was located in southern mid-latitudes of Panthalassa. High-resolution carbon isotope (δ13C) correlation between Waiheke and the Permian-Triassic boundary (PTB) type section indicates that the EPME is recorded in a thin black claystone interbedded between siliceous mudstone beds at WHK 1. Pyrite-dominated enrichment in highly reactive iron, coupled with elevated U/Al and Mo/Al ratios, are prevalent through this black claystone bed and the overlying Permo-Triassic transition strata, suggesting the development of euxinic water column conditions. Similar redox variations across the EPME horizon have been reported from other Panthalassic deep-sea PTB sections. Comparison with these PTB sections indicates that euxinic conditions were widespread in low-latitude regions of the Panthalassan ocean, and such conditions developed earlier than in mid-latitude settings, up to 100,000 years before the EPME. This suggests there was a gradual expansion of ocean anoxia from low to middle-high latitude regions during the Permo-Triassic transition. The extent of ocean anoxia resulted in a decrease in the seawater inventory of redox sensitive trace metals (e.g., Mo), which is evident in the earliest Triassic strata of the studied section and other PTB sections. Panthalassic anoxia during the EPME coincides with extreme climate warming and the associated effects (e.g., changes in ocean circulation, marine eutrophication intensified by terrestrial weathering) were likely critical triggers for ocean deoxygenation.
- Published
- 2021
14. Differentiation of hypointense nodules on gadoxetic acid-enhanced hepatobiliary-phase MRI using T2 enhanced spin-echo imaging with the time-reversed gradient echo sequence: An initial experience
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Masanobu Nakamura, Hiroshi Honda, Marc Van Cauteren, Makoto Obara, Yasutomo Katsumata, Tomoyuki Okuaki, Yukihisa Takayama, Akihiro Nishie, Atsushi Takemura, and Masami Yoneyama
- Subjects
Gadoxetic acid ,business.industry ,General Medicine ,030218 nuclear medicine & medical imaging ,03 medical and health sciences ,0302 clinical medicine ,Flip angle ,030220 oncology & carcinogenesis ,Hepatobiliary phase ,Spin echo ,Medicine ,Radiology, Nuclear Medicine and imaging ,business ,Nuclear medicine ,medicine.drug ,Gradient echo - Abstract
Purpose To optimize the flip angle (FA) of the T2 enhanced spin-echo imaging using the time reversed gradient echo (T2FFE) and evaluate its utility for differentiating hypointensity nodules in the hepatobiliary phase (HBP) of gadoxetic acid-enhanced (Gd-EOB) MRI. Materials and methods First, FA optimization of the T2FFE in the HBP was investigated by comparing signal-to-noise ratio (SNR) among different FAs using phantoms. The liver-to-muscle contrast ratios (CRLiver-Muscle) and image quality among three FAs (20°, 50° and 80°) were compared using images of 10 patients. Next, the utility of the T2FFE with an optimized FA for differentiating hypointensity nodules in the HBP was assessed by comparing the lesion-to-liver contrast ratio (CRLesion-Liver) among cysts, hemangiomas, hepatocellular carcinomas, and metastatic tumors in 32 patients. Results SNR increased as FA increased, but leveled off at FAs of 50° and greater. The FA of 50° showed significantly better image quality scores than that of 80° (p Conclusion The T2FFE in the HBP of Gd-EOB-MRI is useful for differentiating benign and malignant liver lesions.
- Published
- 2017
15. EDUCATION SYSTEM FOR ELECTRONIC CIRCUIT CONSTRUCTION INVOLVING SOLDERING ON A CIRCUIT BOARD
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Atsushi Takemura
- Subjects
Printed circuit board ,Computer science ,business.industry ,Soldering ,Electrical engineering ,Educational technology ,business ,Mobile device ,Electronic equipment ,Electronic circuit - Published
- 2019
16. Usefulness of 3D hybrid profile order technique with 3T magnetic resonance cholangiography: Comparison of image quality and acquisition time
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Yuji Iyama, Takeshi Nakaura, Atsushi Takemura, Yasuyuki Yamashita, Seiji Sakamoto, Koichi Yokoyama, Tomoyuki Okuaki, and Kazunori Harada
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medicine.medical_specialty ,Magnetic resonance cholangiopancreatography ,Materials science ,medicine.diagnostic_test ,Image quality ,media_common.quotation_subject ,Magnetic resonance imaging ,Gastroenterology ,030218 nuclear medicine & medical imaging ,03 medical and health sciences ,0302 clinical medicine ,Cholangiography ,Internal medicine ,cardiovascular system ,medicine ,Image acquisition ,Contrast (vision) ,Radiology, Nuclear Medicine and imaging ,Acquisition time ,Imaging technique ,030217 neurology & neurosurgery ,circulatory and respiratory physiology ,media_common ,Biomedical engineering - Abstract
PURPOSE To evaluate the image quality and acquisition time of magnetic resonance cholangiopancreatography (MRCP) with and without the 3D hybrid profile order technique. MATERIALS AND METHODS We studied 32 consecutive patients at 3T. They underwent MRCP with and without the 3D hybrid profile order imaging technique during free breathing and MRCP with the 3D hybrid profile order technique during a single breath-hold. The image acquisition time was 82% shorter with the 3D hybrid profile order technique than without it. The contrast, signal-to-noise-ratio (SNR), and contrast-noise-ratio (CNR) between the common bile duct (CBD) and periductal tissues on 3D-MRCP were evaluated quantitatively. RESULTS The contrast, SNR, and CNR of the CBD under free breathing was significantly higher with the 3D hybrid profile order technique than without it (P < 0.01). The contrast, SNR, and CNR of the CBD under a single breath-hold was significantly higher with the 3D hybrid profile order technique than without it (P < 0.01). There were no significant differences in the contrast, SNR, and CNR of the CBD between the 3D hybrid profile order with a single breath-hold and with free breathing (P = 0.12, 0.28, 0.28, respectively). CONCLUSION Using 3T MRI for MRCP with the 3D hybrid profile order sequence yielded significantly improved contrast and CNR with a shorter image acquisition time without sacrificing image quality when compared to imaging without the 3D hybrid profile order sequence. J. Magn. Reson. Imaging 2016;44:1346-1353.
- Published
- 2016
17. Preface: The 15th Meeting of the International Association of Radiolarists (InterRad XV), 20 October–1 November, 2017, Niigata, Japan (Part 2)
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Atsushi Matsuoka, Toshiyuki Kurihara, Yoshihito Kamata, and Atsushi Takemura
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Paleontology ,Ecology, Evolution, Behavior and Systematics - Published
- 2020
18. E-LEARNING SYSTEM FOR THE COMPREHENSIVE LEARNING OF ELECTRONIC CIRCUITS.
- Author
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Atsushi Takemura
- Subjects
DIGITAL learning ,ELECTRONIC circuits ,SOLDER & soldering ,UNDERGRADUATES ,EXPERIMENTAL methods in education - Abstract
This paper proposes a novel e-learning system for comprehensive learning covering theoretical analysis, design, and experiments involving the construction of practical electronic circuits. The proposed system possesses technical novelty that enables a student to efficiently construct circuits according to an automated instruction of circuit design. Moreover, this system allows the student to select an appropriate type of circuit construction strategy, such as with/without soldering, depending on his purpose and ability. The effectiveness of the proposed system was verified by performing a comparison experiment using 40 undergraduate students at the Tokyo University of Agriculture and Technology. The comparison tests were done by two groups of students comprising students that used or did not use the proposed system demonstrated the effectiveness of the system. [ABSTRACT FROM AUTHOR]
- Published
- 2020
19. New high latitude Capnuchosphaera species (Triassic Radiolaria) from Waipapa Terrane, New Zealand
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Koji Takayama, Kazuto Kodama, Toyosaburo Sakai, Yoshiaki Aita, Bernhard Sporli, Rie S. Hori, Atsushi Takemura, and J.A. Grant-Mackie
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Paleontology ,Taxon ,biology ,Genus ,Fauna ,Mesozoic ,Subspecies ,biology.organism_classification ,Southern Hemisphere ,Geology ,Radiolaria ,Terrane - Abstract
Two new species and one new subspecies of genus Capnuchosphaera, (Capnuchosphaera tumida nov. sp., C. waihekeensis nov. sp. and C. texensis australis nov. ssp.) are described herein from phosphatic nodules included in mudstone and sandstone beds of the Waipapa Terrane, Waiheke Island, New Zealand. The phosphatic nodules yielded a rich Late Triassic (Carnian-Norian) radiolarian fauna, with a high abundance of spumellarian taxa including numerous species of the genera Capnuchosphaera, Vinassaspongus, Kahlerosphaera, Sarla and Dumitricasphaera. Waiheke Island Capnuchosphaera are characterized by a large cortical shell and a distinctively low ratio of spine length to cortical shell diameter. These features differ significantly from those of Capnuchosphaera in the Tethyan Realm and are considered to be the result of adaptation to an Austral-New Zealand peripheral ocean of Gondwanaland in the Mesozoic Southern Hemisphere.
- Published
- 2015
20. Optimization and Clinical Feasibility of Free-breathing Diffusion-weighted Imaging of the Liver: Comparison with Respiratory-Triggered Diffusion-weighted Imaging
- Author
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Daisuke Kakihara, Taro Takahara, Hiroshi Honda, Akihiro Nishie, Yoshiki Asayama, Atsushi Takemura, Nobuhiro Fujita, Yukihisa Takayama, Takashi Yoshiura, Yasuhiro Ushijima, Kousei Ishigami, and Makoto Obara
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Adult ,Liver Cirrhosis ,Male ,Respiratory-Gated Imaging Techniques ,medicine.medical_specialty ,Carcinoma, Hepatocellular ,Liver tumor ,Gastrointestinal Stromal Tumors ,Image quality ,Signal-To-Noise Ratio ,Liver disease ,Hepatitis B, Chronic ,Image noise ,Humans ,Medicine ,Effective diffusion coefficient ,Radiology, Nuclear Medicine and imaging ,cardiovascular diseases ,Image resolution ,Aged ,Aged, 80 and over ,medicine.diagnostic_test ,business.industry ,Liver Diseases ,Respiration ,Liver Neoplasms ,Magnetic resonance imaging ,Hepatitis C, Chronic ,Middle Aged ,Image Enhancement ,medicine.disease ,Healthy Volunteers ,Diffusion Magnetic Resonance Imaging ,Liver ,Feasibility Studies ,Female ,Radiology ,Artifacts ,business ,Nuclear medicine ,Diffusion MRI - Abstract
PURPOSE We compared the image quality of free-breathing diffusion-weighted imaging (FB-DWI) to that of respiratory-triggered DWI (RT-DWI) after proper optimization. MATERIALS AND METHODS Three healthy subjects were scanned to optimize magnetic resonance (MR) parameters of FB-DWI to improve image quality, including spatial resolution, image noise, and chemical shift artifacts. After this optimization, we scanned 32 patients with liver disease to assess the clinical feasibility of the optimized FB-DWI. Of the 32 patients, 14 had a total of 28 hepatocellular carcinomas (HCCs), four had a total of 15 metastatic liver tumors, and the other 14 had no tumor. Qualitatively, we compared the image quality scores of FB-DWI with those of RT-DWI with the Wilcoxon signed-rank test. Quantitatively, we compared the signal-to-noise ratios (SNRs) of the liver parenchyma, lesion-to-nonlesion contrast-to-noise ratios (CNRs) and apparent diffusion coefficient (ADC) values of the liver parenchyma and liver tumor by the paired t-test. RESULTS The average scores of image quality for sharpness of liver contour, image noise, and chemical shift artifacts were significantly higher for FB-DWI than RT-DWI (P < 0.05). SNRs, CNRs, and ADC values of the liver parenchyma and tumors did not differ significantly between the 2 DWI methods. CONCLUSION Compared with RT-DWI, the optimized FB-DWI provided better spatial resolution, fewer artifacts, and comparable SNRs, lesion-to-nonlesion CNRs, and ADC values.
- Published
- 2015
21. Reduction of respiratory ghosting motion artifacts in conventional two-dimensional multi-slice Cartesian turbo spin-echo: which k-space filling order is the best?
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Masami Yoneyama, Atsushi Takemura, Masanobu Nakamura, and Yuuji Inoue
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Turbo ,Movement ,Physical Therapy, Sports Therapy and Rehabilitation ,Imaging phantom ,030218 nuclear medicine & medical imaging ,law.invention ,Reduction (complexity) ,03 medical and health sciences ,Motion ,0302 clinical medicine ,law ,Humans ,Radiology, Nuclear Medicine and imaging ,Cartesian coordinate system ,Sensitivity (control systems) ,Ghosting ,Physics ,Sequence ,Radiation ,biology ,Phantoms, Imaging ,Respiration ,k-space ,General Medicine ,biology.organism_classification ,Image Enhancement ,Magnetic Resonance Imaging ,Artifacts ,Algorithm ,030217 neurology & neurosurgery - Abstract
The two-dimensional Cartesian turbo spin-echo (TSE) sequence is widely used in routine clinical studies, but it is sensitive to respiratory motion. We investigated the k-space orders in Cartesian TSE that can effectively reduce motion artifacts. The purpose of this study was to demonstrate the relationship between k-space order and degree of motion artifacts using a moving phantom. We compared the degree of motion artifacts between linear and asymmetric k-space orders. The actual spacing of ghost artifacts in the asymmetric order was doubled compared with that in the linear order in the free-breathing situation. The asymmetric order clearly showed less sensitivity to incomplete breath-hold at the latter half of the imaging period. Because of the actual number of partitions of the k-space and the temporal filling order, the asymmetric k-space order of Cartesian TSE was superior to the linear k-space order for reduction of ghosting motion artifacts.
- Published
- 2017
22. Differentiation of hypointense nodules on gadoxetic acid-enhanced hepatobiliary-phase MRI using T
- Author
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Masami, Yoneyama, Yukihisa, Takayama, Akihiro, Nishie, Masanobu, Nakamura, Yasutomo, Katsumata, Atsushi, Takemura, Makoto, Obara, Tomoyuki, Okuaki, Hiroshi, Honda, and Marc, Van Cauteren
- Subjects
Adult ,Aged, 80 and over ,Gadolinium DTPA ,Male ,Liver Neoplasms ,Contrast Media ,Reproducibility of Results ,Middle Aged ,Signal-To-Noise Ratio ,Image Enhancement ,Magnetic Resonance Imaging ,Diagnosis, Differential ,Liver ,Feasibility Studies ,Humans ,Female ,Prospective Studies ,Aged - Abstract
To optimize the flip angle (FA) of the TFirst, FA optimization of the T2FFE in the HBP was investigated by comparing signal-to-noise ratio (SNR) among different FAs using phantoms. The liver-to-muscle contrast ratios (CRSNR increased as FA increased, but leveled off at FAs of 50° and greater. The FA of 50° showed significantly better image quality scores than that of 80° (p0.05). After employing an FA of 50°, the CRThe T2FFE in the HBP of Gd-EOB-MRI is useful for differentiating benign and malignant liver lesions.
- Published
- 2017
23. Diffusivity of intraorbital lymphoma vs. inflammation: comparison of single shot turbo spin echo and multishot echo planar imaging techniques
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Osamu Togao, Ryotaro Kamei, Hiroshi Honda, Akio Hiwatashi, Koji Yamashita, Kazufumi Kikuchi, Hiroshi Yoshikawa, and Atsushi Takemura
- Subjects
Adult ,Male ,medicine.medical_specialty ,Eye Diseases ,Lymphoma ,Orbital lymphoma ,Eye ,030218 nuclear medicine & medical imaging ,Diagnosis, Differential ,03 medical and health sciences ,Young Adult ,0302 clinical medicine ,Medicine ,Effective diffusion coefficient ,Humans ,Radiology, Nuclear Medicine and imaging ,cardiovascular diseases ,Neuroradiology ,Aged ,Retrospective Studies ,Aged, 80 and over ,Inflammation ,business.industry ,Echo-Planar Imaging ,Ultrasound ,Single shot ,Reproducibility of Results ,General Medicine ,Middle Aged ,medicine.disease ,body regions ,Diffusion Magnetic Resonance Imaging ,ROC Curve ,Spin echo ,Orbital Neoplasms ,Female ,Radiology ,business ,Nuclear medicine ,030217 neurology & neurosurgery ,Diffusion MRI - Abstract
To compare the abilities of turbo spin-echo diffusion-weighted imaging (TSE DWI) and multi-shot echo planar DWI (MSh DWI) to discriminate orbital lymphoma from inflammatory lesions. Twenty-nine patients with pathologically confirmed lymphomas and 39 patients with inflammation were imaged with a 3.0-T system. The apparent diffusion coefficient (ADC) of each lesion was measured. Signal intensities compared to normal grey matter on conventional imaging were also measured. The ADCs derived from the TSE DWI of the lymphomas (0.68 ± 0.14 × 10−3 mm2/s) were significantly lower than those of the inflammation cases (1.04 ± 0.39 × 10−3 mm2/s; p 0.05). The ROC analysis showed the best diagnostic performance with ADCs derived from TSE DWI (the area under the curve: AUC = 0.831) followed by ADC derived from MSh DWI (AUC = 0.633). The ADCs derived from TSE DWI might help to differentiate orbital lymphomas from inflammation. • ADC of lymphoma was significantly lower than that of inflammation. • ADC derived from TSE DWI showed the best diagnostic performance. • This study was conducted by a 3-T MR scanner.
- Published
- 2017
24. Comparison between multi-shot gradient echo EPI and balanced SSFP in unenhanced 3T MRA of thoracic aorta in healthy volunteers
- Author
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Seitaro Oda, Shinichi Tokuyasu, Kosuke Morita, Takeshi Nakaura, Atsushi Takemura, Yuji Iyama, Tomohiro Namimoto, Yasuyuki Yamashita, Tomoyuki Okuaki, Masafumi Kidoh, Kenichiro Hirata, Hideaki Yuki, Yoshinori Funama, Yasunori Nagayama, Daisuke Utsunomiya, and Mika Kitajima
- Subjects
Adult ,Male ,medicine.medical_specialty ,Planar Imaging ,Image quality ,Aorta, Thoracic ,030204 cardiovascular system & hematology ,Signal-To-Noise Ratio ,Magnetic resonance angiography ,030218 nuclear medicine & medical imaging ,03 medical and health sciences ,0302 clinical medicine ,Reference Values ,medicine.artery ,Healthy volunteers ,Image Processing, Computer-Assisted ,Medicine ,Thoracic aorta ,Humans ,Radiology, Nuclear Medicine and imaging ,Balanced ssfp ,medicine.diagnostic_test ,business.industry ,Echo-Planar Imaging ,General Medicine ,Healthy Volunteers ,Signal-to-noise ratio (imaging) ,cardiovascular system ,Female ,Radiology ,business ,Nuclear medicine ,Artifacts ,Magnetic Resonance Angiography ,Gradient echo - Abstract
The purpose of this study was to compare scan time and image quality between magnetic resonance angiography (MRA) of the thoracic aorta using a multi-shot gradient echo planar imaging (MSG-EPI) and MRA using balanced steady-state free precession (b-SSFP).Healthy volunteers (n=17) underwent unenhanced thoracic aorta MRA using balanced steady-state free precession (b-SSFP) and MSG-EPI sequences on a 3T MRI. The acquisition time, total scan time, signal-to-noise ratio (SNR) of the thoracic aorta, and the coefficient of variation (CV) of thoracic aorta were compared with paired t-tests. Two radiologists independently recorded the images' contrast, noise, sharpness, artifacts, and overall quality on a 4-point scale.The acquisition time was 36.2% shorter for MSG-EPI than b-SSFP (115.5±14.4 vs 181.0±14.9s, p0.01). The total scan time was 40.4% shorter for MSG-EPI than b-SSFP (272±78 vs 456±144s, p0.01). There was no significant difference in mean SNR between MSG-EPI and b-SSFP scans (17.3±3.6 vs 15.2±4.3, p=0.08). The CV was significantly lower for MSG-EPI than b-SSFP (0.2±0.1 vs. 0.5±0.2, p0.01). All qualitative scores except for image noise were significantly higher in MSG-EPI than b-SSFP scans (p0.05).The MSG-EPI sequence is a promising technique for shortening scan time and yielding more homogenous image quality in MRA of thoracic aorta on 3T scanners compared with the b-SSFP.
- Published
- 2017
25. A probable shark dorsal fin spine fragment from the Early Triassic of the Arrow Rocks sequence, Whangaroa, northern New Zealand
- Author
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J.A. Grant-Mackie, Hamish J. Campbell, Satoshi Yamakita, Yoshiaki Aita, Rie S. Hori, Satoshi Takahashi, T Matsumoto, and Atsushi Takemura
- Subjects
Paleozoic ,biology ,Fauna ,Early Triassic ,Geology ,biology.organism_classification ,Dorsal fin ,Spine (zoology) ,Sequence (geology) ,Paleontology ,Geophysics ,Earth and Planetary Sciences (miscellaneous) ,Small fragment ,Conodont - Abstract
The ornament on a small external cast in pink chert shows considerable similarity with that of various Middle Palaeozoic and Triassic fish genera. It comes from the Permian–Triassic Oruatemanu Formation of Arrow Rocks, Whangaroa area, eastern Northland. Conodont faunas from a few metres above and below the sample allow correlation with the Neospathodus pakistanensis zone of the Early Triassic, which is assigned to the late Dienerian (late Induan), with adjacent conodont zone faunas in their correct stratigraphic association. The cast is assumed to be that of a small fragment of fin spine, most likely from the junction area of the crown and root on the right-hand side of a dorsal fin spine, possibly anterior, of a marine ctenacanthoid shark, a basal shark order not previously recorded from New Zealand.
- Published
- 2014
26. Quantification of Myocardial Iron Deficiency in Nonischemic Heart Failure by Cardiac T2* Magnetic Resonance Imaging
- Author
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Yoshio Matsuo, Kenji Sunagawa, Yuzo Yamasaki, Hiroshi Honda, Masato Yonezawa, Yasushi Mukai, Satoshi Kawanami, Atsushi Takemura, Taiki Higo, Hidetake Yabuuchi, Michinobu Nagao, Kohtaro Abe, Takashi Yoshiura, and Takeshi Kamitani
- Subjects
Male ,Cardiac function curve ,medicine.medical_specialty ,Anemia ,Magnetic Resonance Imaging, Cine ,Ventricular Function, Left ,Electrocardiography ,Internal medicine ,medicine ,Humans ,cardiovascular diseases ,Retrospective Studies ,Heart Failure ,Ejection fraction ,Anemia, Iron-Deficiency ,medicine.diagnostic_test ,business.industry ,Myocardium ,Stroke Volume ,Magnetic resonance imaging ,Iron Deficiencies ,Iron deficiency ,Stroke volume ,Middle Aged ,Prognosis ,medicine.disease ,Echocardiography ,Heart failure ,cardiovascular system ,Cardiology ,Female ,Cardiology and Cardiovascular Medicine ,Nuclear medicine ,business ,Follow-Up Studies - Abstract
The aim of this study was to use T2* cardiac magnetic resonance (CMR) imaging to quantify myocardial iron content in patients with heart failure (HF) and to investigate the relation between iron content, cardiac function, and the cause of HF. CMR data were analyzed from 167 patients with nonischemic and 31 with ischemic HF and 50 patients with normal ventricular function. Short-axis T2* imaging was accomplished using 3-T scanner and multiecho gradient-echo sequence. Myocardial T2* value (M-T2*) was calculated by fitting the signal intensity data for the mid-left ventricular (LV) septum to a decay curve. Patients with nonischemic HF were categorized into patients with LV ejection fraction (LVEF)35% or ≥35%. The relation between nonischemic HF with LVEF35% and the risk for major adverse cardiac events was analyzed by multivariate logistic regression analysis using M-T2* and HF biomarkers. M-T2* was significantly greater for patients with nonischemic HF (LVEF35%: 29 ± 7 ms, LVEF ≥35%: 26 ± 5 ms) than for patients with normal LV function (22 ± 3 ms, p0.0001) or ischemic HF (22 ± 4 ms, p0.001). The odds ratio was 1.21 for M-T2* (p0.0001) and 1.0015 for brain natriuretic peptide (p0.0001) in relation to nonischemic HF with LVEF35%. Furthermore, this value was 0.96 for systolic blood pressure (p = 0.012) and 1.02 for M-T2* (p = 0.03) in relation to the risk for major adverse cardiac events in patients with nonischemic HF. In conclusion, T2* CMR demonstrated the robust relation between myocardial iron deficiency and nonischemic HF. M-T2* is a biomarker that can predict adverse cardiac function in patients with nonischemic HF.
- Published
- 2014
27. Three-dimensional T2-weighted imaging for liver MRI: Clinical values of tissue-specific variable refocusing flip-angle turbo spin echo imaging
- Author
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Makoto Obara, Yukihisa Takayama, Takashi Yoshiura, Nobuhiro Fujita, Masami Yoneyama, Akihiro Nishie, Atsushi Takemura, Yasuhiro Ushijima, Dai Shimamoto, Yoshiki Asayama, and Hiroshi Honda
- Subjects
medicine.diagnostic_test ,Wilcoxon signed-rank test ,business.industry ,Magnetic resonance imaging ,Fast spin echo ,symbols.namesake ,Bonferroni correction ,McNemar's test ,Flip angle ,symbols ,medicine ,Tissue specific ,Radiology, Nuclear Medicine and imaging ,business ,T2 weighted ,Nuclear medicine - Abstract
Purpose To assess the clinical utility of tissue-specific variable refocusing flip-angle (VRFA) turbo-spin echo imaging for three-dimensional T2-weighted imaging (3D-T2WI) of the liver. Materials and Methods Fifty-nine patients were scanned with three types of fat-suppressed T2WI for the comparison: two-dimensional single-shot turbo spin echo T2WI (ssT2WI), 3D-T2WI with tissue-specific VRFA (VISTA-TSV), and 3D-T2WI with low-constant VRFA (VISTA). Qualitatively, artifacts in the left and right lobes of the liver and black-blood effects in the liver were compared using the Wilcoxon signed-rank test with the Bonferroni correction. The detection and correct characterization rates of liver lesions were compared using McNemar's test. Results VISTA-TSV showed reduced artifacts in the left and right lobes of the liver compared with VISTA (P
- Published
- 2014
28. Intravoxel Incoherent Motion in Normal Pituitary Gland: Initial Study with Turbo Spin-Echo Diffusion-Weighted Imaging
- Author
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Atsushi Takemura, Takashi Iwanaga, Masatoyo Nakajo, Tomoyuki Okuaki, Takashi Yoshiura, Michiro Sasaki, T Fujisaki, Yoshihiko Fukukura, Saito T, and Kiyohisa Kamimura
- Subjects
Adult ,Male ,Pituitary gland ,Intraclass correlation ,Splenium ,Corpus callosum ,030218 nuclear medicine & medical imaging ,03 medical and health sciences ,Motion ,0302 clinical medicine ,Nuclear magnetic resonance ,Anterior pituitary ,medicine ,Humans ,Radiology, Nuclear Medicine and imaging ,cardiovascular diseases ,Head & Neck ,Intravoxel incoherent motion ,business.industry ,Anatomy ,Lobe ,medicine.anatomical_structure ,Diffusion Magnetic Resonance Imaging ,Pituitary Gland ,Female ,Neurology (clinical) ,business ,Artifacts ,030217 neurology & neurosurgery ,Diffusion MRI - Abstract
BACKGROUND AND PURPOSE: DWI with conventional single-shot EPI of the pituitary gland is hampered by strong susceptibility artifacts. Our purpose was to evaluate the feasibility of intravoxel incoherent motion assessment by using DWI based on TSE of the normal anterior pituitary lobe. MATERIALS AND METHODS: The intravoxel incoherent motion parameters, including the true diffusion coefficient ( D ), the perfusion fraction ( f ), and the pseudo-diffusion coefficient ( D *), were obtained with TSE-DWI in 5 brain regions (the pons, the WM and GM of the vermis, and the genu and splenium of the corpus callosum) in 8 healthy volunteers, and their agreement with those obtained with EPI-DWI was evaluated by using the intraclass correlation coefficient. The 3 intravoxel incoherent motion parameters in the anterior pituitary lobe were compared with those in the brain regions by using the Dunnett test. RESULTS: The agreement between TSE-DWI and EPI-DWI was moderate (intraclass correlation coefficient = 0.571) for D , substantial (0.699) for f ', but fair (0.405) for D *. D in the anterior pituitary lobe was significantly higher than in the 5 brain regions ( P < .001). The f in the anterior pituitary lobe was significantly higher than in the 5 brain regions ( P < .001), except for the vermian GM. The pituitary D * was not significantly different from that in the 5 brain regions. CONCLUSIONS: Our results demonstrated the feasibility of intravoxel incoherent motion assessment of the normal anterior pituitary lobe by using TSE-DWI. High D and f values in the anterior pituitary lobe were thought to reflect its microstructural and perfusion characteristics. D : true diffusion coefficient D * : pseudo-diffusion coefficient f : perfusion fraction ICC : intraclass correlation coefficient IVIM : intravoxel incoherent motion
- Published
- 2016
29. Simple method for whole-brain volumetric T1-weighted turbo spin-echo imaging
- Author
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Satoshi Tatsuno, Seishi Sawano, Masanobu Nakamura, Makoto Obara, Masami Yoneyama, Atsushi Takemura, and Takashi Namiki
- Subjects
Adult ,Male ,Materials science ,Image quality ,media_common.quotation_subject ,Contrast Media ,Physical Therapy, Sports Therapy and Rehabilitation ,Image processing ,Signal-To-Noise Ratio ,Motion ,Young Adult ,Imaging, Three-Dimensional ,Quality (physics) ,Nuclear magnetic resonance ,Signal-to-noise ratio ,Simple (abstract algebra) ,Image Processing, Computer-Assisted ,Humans ,Contrast (vision) ,Radiology, Nuclear Medicine and imaging ,media_common ,Brain Mapping ,Radiation ,Spins ,Phantoms, Imaging ,Brain ,Reproducibility of Results ,General Medicine ,Middle Aged ,Magnetic Resonance Imaging ,Spin echo ,Female ,Artifacts - Abstract
We propose a simple scheme of 3D turbo spin echo (TSE) with low-refocusing flip angles (RFAs) for obtaining sufficient T1-weighted contrast. The low RFA can easily lead spins into a pseudo-steady-state (PSS) condition, but a preparation scheme is required for smooth transition into static PSS. For obtaining T1 contrast, PSS preparation is the most important factor, and therefore we focused on the PSS preparation. To optimize the T1 contrast in the proposed sequence, we compared the following parameters: RFAs of 90° and 30°, and a PSS preparation scheme of "90° + α/2" and asymptotic preparation. Subsequently, to demonstrate the quality of the proposed sequence, we compared the image quality regarding conventional 3D TSE and 2D spin echo (SE). A combination of an RFA of 30° and the "90° + α/2" preparation scheme showed the highest T1 contrast. The optimized sequence provided higher contrast and sharper images compared to 3D TSE, and it showed contrast and a signal-to-noise ratio similar to those of 2D SE.
- Published
- 2013
30. Sulfur isotope profiles in the pelagic Panthalassic deep sea during the Permian–Triassic transition
- Author
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Yoshiaki Aita, Rie S. Hori, Takahiro Watanabe, Masahiro Oba, Satoshi Takahashi, Takeshi Kakegawa, K. Bernhard Spörli, Atsushi Takemura, Kunio Kaiho, Paul Gorjan, and Satoshi Yamakita
- Subjects
Extinction event ,Global and Planetary Change ,Permian ,Paleozoic ,Stable isotope ratio ,chemistry.chemical_element ,Oceanography ,Sulfur ,Deep sea ,Paleontology ,chemistry ,Phanerozoic ,Mesozoic ,Geology - Abstract
Mesozoic accretionary complexes in Japan and New Zealand contain Panthalassic low latitude and southern mid-latitude deep-water sedimentary rock respectively. These sedimentary rocks record environmental changes in the pelagic Panthalassic Ocean during the transition associated with the severe Permian–Triassic mass extinction. This study presents sulfur isotope records of sulfide from continuous deep-sea Permian–Triassic boundary sections located in northeast Japan (the Akkamori section-2, the most continuous section among other previously reported deep-sea sections) and North Island of New Zealand (the Waiheke-1 section, providing the first sulfur isotopic record from a southern hemisphere deep-sea section). Both sections show sharp ~ 15‰ drops of the sulfur isotope ratio coupled with a negative shift of organic carbon isotope ratio. Similar decreases in sulfur isotope ratio of carbonate-associated sulfates by ~ 10‰ accompanied with a negative shift of inorganic carbon isotope ratio at the end-Permian mass extinction horizon have been reported in some shallow water Paleotethyan sections. These sulfur isotope changes suggest that a massive release of 32 S-enriched sulfur from the H 2 S-rich water to the oxic surface-waters coincided with the end-Permian mass extinction.
- Published
- 2013
31. Quantification of myocardial oxygenation in heart failure using blood-oxygen-level-dependent T2* magnetic resonance imaging: Comparison with cardiopulmonary exercise test
- Author
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Michinobu Nagao, Yuji Watanabe, Tomomi Ide, Taiki Higo, Satoshi Kawanami, Kenji Fukushima, Atsushi Takemura, Yuzo Yamasaki, Umiko Ishizaki, Koji Sagiyama, Takeshi Kamitani, and Hiroshi Honda
- Subjects
Adult ,Male ,medicine.medical_specialty ,medicine.medical_treatment ,Heart Ventricles ,Biomedical Engineering ,Biophysics ,030204 cardiovascular system & hematology ,030218 nuclear medicine & medical imaging ,03 medical and health sciences ,Hemoglobins ,0302 clinical medicine ,Oxygen Consumption ,Refractory ,Heart Rate ,Internal medicine ,medicine ,Humans ,Radiology, Nuclear Medicine and imaging ,Aged ,Heart transplantation ,Heart Failure ,Blood-oxygen-level dependent ,medicine.diagnostic_test ,Inhalation ,Pulse (signal processing) ,Chemistry ,Surrogate endpoint ,Myocardium ,Respiration ,Magnetic resonance imaging ,Heart ,Middle Aged ,medicine.disease ,Magnetic Resonance Imaging ,Surgery ,Oxygen ,Heart failure ,Oxyhemoglobins ,Cardiology ,Exercise Test ,Female - Abstract
Quantification of myocardial oxygenation (MO) in heart failure (HF) has been less than satisfactory. This has necessitated the use of invasive techniques to measure MO directly or to determine the oxygen demand during exercise using the cardiopulmonary exercise (CPX) test. We propose a new quantification method for MO using blood-oxygen-level-dependent (BOLD) myocardial T2* magnetic resonance imaging (M-T2* MRI), and investigate its correlation with CPX results.Thirty patients with refractory HF who underwent cardiac MRI and CPX test for heart transplantation, and 24 healthy, age-matched volunteers as controls were enrolled. M-T2* imaging was performed using a 3-Tesla and multi-echo gradient-echo sequence. M-T2* was calculated by fitting the signal intensity data for the mid-left ventricular septum to a decay curve. M-T2* was measured under room-air (T2*-air) and after inhalation of oxygen for 10min at a flow rate of 10L/min (T2*-oxy). MO was defined as the difference between the two values (ΔT2*). Changes in M-T2* at the two conditions and ΔT2* between the two groups were compared. Correlation between ΔT2* and CPX results was analyzed using the Pearson coefficient.T2*-oxy was significantly greater than T2*-air in patients with HF (29.9±7.3ms vs. 26.7±6.0ms, p0.001), whereas no such difference was observed in controls (25.5±4.0ms vs. 25.4±4.4ms). ΔT2* was significantly greater for patients with HF than for controls (3.2±4.5ms vs. -0.1±1.3ms, p0.001). A significant correlation between ΔT2* and CPX results (peak VOΔT2* is increased T2*-oxy is greater in patients with HF, and is correlated with oxygen metabolism during exercise as measured by the CPX test. Hence, ΔT2* can be used as a surrogate marker of MO instead of CPX test.
- Published
- 2016
32. Three-dimensional phase contrast magnetic resonance imaging validated to assess pulmonary artery flow in patients with chronic thromboembolic pulmonary hypertension
- Author
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Kazuya Hosokawa, Masateru Kawakubo, Kohtaro Abe, Hiroshi Akamine, Junji Morishita, Atsushi Takemura, Michinobu Nagao, and Yuzo Yamasaki
- Subjects
Novel technique ,Male ,medicine.medical_specialty ,Hypertension, Pulmonary ,Physical Therapy, Sports Therapy and Rehabilitation ,030204 cardiovascular system & hematology ,Pulmonary Artery ,Phase contrast magnetic resonance imaging ,030218 nuclear medicine & medical imaging ,03 medical and health sciences ,0302 clinical medicine ,Imaging, Three-Dimensional ,Internal medicine ,medicine.artery ,Healthy volunteers ,medicine ,Humans ,Radiology, Nuclear Medicine and imaging ,In patient ,Stroke ,Retrospective Studies ,Radiation ,business.industry ,General Medicine ,Middle Aged ,medicine.disease ,Magnetic Resonance Imaging ,Case-Control Studies ,Pulmonary artery ,Cardiology ,Chronic thromboembolic pulmonary hypertension ,Female ,business ,Pulmonary Embolism ,After treatment - Abstract
In this study, three-dimensional phase contrast magnetic resonance imaging (3D-PC MRI), a novel technique, was validated to assess pulmonary artery (PA) flow in patients with chronic thromboembolic pulmonary hypertension (CTEPH). The MR data of PAs from 3D-PC and two-dimensional PC (2D-PC) from before and after treatment for 3 patients with CTEPH were retrospectively analyzed. Additionally, 3D- and 2D-PC MR scans of PA were performed in 5 healthy volunteers. Correlation of stroke volumes (SVs) obtained by 3D-PC and 2D-PC was analyzed using Pearson’s correlation coefficients. There was an excellent correlation in the SV of main PA, left PA and right PA between 3D-PC and 2D-PC (main PA: r = 0.91, p
- Published
- 2016
33. Optimization of 3D-variable refocusing flip angle RARE imaging for high-resolution volumetric black-blood angiography
- Author
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Masanobu Nakamura, Masami Yoneyama, Makoto Obara, Takashi Tabuchi, and Atsushi Takemura
- Subjects
Radiation ,Materials science ,medicine.diagnostic_test ,Phantoms, Imaging ,Carotid arteries ,Black blood ,Angiography ,High resolution ,Physical Therapy, Sports Therapy and Rehabilitation ,General Medicine ,Fast spin echo ,Flow phantom ,Imaging, Three-Dimensional ,Nuclear magnetic resonance ,Rapid acquisition ,Flip angle ,medicine ,Humans ,Radiology, Nuclear Medicine and imaging - Abstract
3D rapid acquisition with relaxation enhancement or turbo spin-echo sequence is promising for black-blood angiography. In this paper, we propose a new scheme of sequence parameter optimization for "flow-void enhanced" volumetric black-blood angiography. Although black-blood imaging has numerous applications, we focused on the carotid artery in this study. All experiments were performed on a 3.0-T imager. The methods used were a flow phantom study and a volunteer study. From the results, the optimal parameters for black-blood angiography were the use of very-low refocusing flip angles, use of a "90° + α/2" refocusing flip angle sweep, and "flow sensitization" at the "in-plane flow" situational imaging plane. This sequence can be used for 3D volumetric black-blood angiography and vessel wall imaging.
- Published
- 2012
34. Usefulness of 3D hybrid profile order technique with 3T magnetic resonance cholangiography: Comparison of image quality and acquisition time
- Author
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Koichi, Yokoyama, Takeshi, Nakaura, Yuji, Iyama, Seiji, Sakamoto, Atsushi, Takemura, Tomoyuki, Okuaki, Kazunori, Harada, and Yasuyuki, Yamashita
- Subjects
Adult ,Male ,Time Factors ,Cholangiopancreatography, Magnetic Resonance ,Pancreatic Diseases ,Reproducibility of Results ,Bile Duct Diseases ,Workload ,Middle Aged ,Image Enhancement ,Multimodal Imaging ,Sensitivity and Specificity ,Imaging, Three-Dimensional ,Image Interpretation, Computer-Assisted ,Humans ,Female ,Aged - Abstract
To evaluate the image quality and acquisition time of magnetic resonance cholangiopancreatography (MRCP) with and without the 3D hybrid profile order technique.We studied 32 consecutive patients at 3T. They underwent MRCP with and without the 3D hybrid profile order imaging technique during free breathing and MRCP with the 3D hybrid profile order technique during a single breath-hold. The image acquisition time was 82% shorter with the 3D hybrid profile order technique than without it. The contrast, signal-to-noise-ratio (SNR), and contrast-noise-ratio (CNR) between the common bile duct (CBD) and periductal tissues on 3D-MRCP were evaluated quantitatively.The contrast, SNR, and CNR of the CBD under free breathing was significantly higher with the 3D hybrid profile order technique than without it (P0.01). The contrast, SNR, and CNR of the CBD under a single breath-hold was significantly higher with the 3D hybrid profile order technique than without it (P0.01). There were no significant differences in the contrast, SNR, and CNR of the CBD between the 3D hybrid profile order with a single breath-hold and with free breathing (P = 0.12, 0.28, 0.28, respectively).Using 3T MRI for MRCP with the 3D hybrid profile order sequence yielded significantly improved contrast and CNR with a shorter image acquisition time without sacrificing image quality when compared to imaging without the 3D hybrid profile order sequence. J. Magn. Reson. Imaging 2016;44:1346-1353.
- Published
- 2015
35. Early Triassic (Induan) Radiolaria and carbon-isotope ratios of a deep-sea sequence from Waiheke Island, North Island, New Zealand
- Author
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Kazuto Kodama, Minoru Ikehara, Toyosaburo Sakai, Yoshiaki Aita, Yoshihito Kamata, Atsushi Takemura, Rie S. Hori, Satoshi Yamakita, J.A. Grant-Mackie, Satoshi Takahashi, K. Bernhard Spörli, and Noritoshi Suzuki
- Subjects
biology ,Lithology ,Stratigraphy ,Early Triassic ,royalty.order_of_chivalry ,Paleontology ,royalty ,Biostratigraphy ,biology.organism_classification ,Deep sea ,Nassellaria ,Conodont ,Ecology, Evolution, Behavior and Systematics ,Radiolaria ,Geology ,Terrane - Abstract
This study examines a Triassic deep-sea sequence consisting of rhythmically bedded radiolarian cherts and shales and its implications for early Induan radiolarian fossils. The sequence, obtained from the Waipapa terrane, Waiheke Island, New Zealand, is composed of six lithologic Units (A–F) and, based on conodont biostratigraphy, spans at least the interval from the lowest Induan to the Anisian. Unit A (the basal unit) consists of black chert and shale beds containing fine pyrite minerals; this corresponds to the oceanic anoxic event described at Arrow Rocks further north in New Zealand. The δ13Corg values of Unit A show a pronounced negative shift between the pale-green chert and black shale/chert, which may represent the negative excursion across the Permian–Triassic boundary that has been documented worldwide. The black cherts, which give minimum C-isotopic ratios (around −30‰), are early Induan, and contain a rich radiolarian fauna characterized by Entactinosphaera? crassispinosa Sashida and Tonishi, E.? spoerlii Takemura and Aono, Bistarkum martiali Feng, Entactinia cf. itsukaichiensis Sashida and Tonishi, Ellipsocopicyntra? sp., and rare Nassellaria. A new Induan nassellarian species, Tripedocorbis? blackae n. sp., from the black chert bed, is described herein. Its presence indicates that Triassic-type Nassellaria had already appeared in the early Induan in the pelagic realms of southern hemisphere Panthalassa.
- Published
- 2011
36. A cost-sensitive extension of AdaBoost with markov random field priors for automated segmentation of breast tumors in ultrasonic images
- Author
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Atsushi Takemura, Akinobu Shimizu, and Kazuhiko Hamamoto
- Subjects
Cost-Benefit Analysis ,Biomedical Engineering ,Scale-space segmentation ,Breast Neoplasms ,Health Informatics ,Image processing ,Pattern Recognition, Automated ,Prior probability ,Image Processing, Computer-Assisted ,Humans ,Radiology, Nuclear Medicine and imaging ,Segmentation ,Computer vision ,AdaBoost ,Ultrasonography ,Mathematics ,Markov random field ,business.industry ,Segmentation-based object categorization ,Pattern recognition ,General Medicine ,Image segmentation ,Computer Graphics and Computer-Aided Design ,Computer Science Applications ,Female ,Surgery ,Computer Vision and Pattern Recognition ,Artificial intelligence ,business ,Algorithms - Abstract
A cost-sensitive extension of AdaBoost based on Markov random field (MRF) priors was developed to train an ensemble segmentation process which can avoid irregular shape, isolated points and holes, leading to lower error rate. The method was applied to breast tumor segmentation in ultrasonic images.A cost function was introduced into the AdaBoost algorithm that penalizes dissimilar adjacent labels in MRF regularization. The extended AdaBoost algorithm generates a series of weak segmentation processes by sequentially selecting a process whose error rate weighted by the cost is minimum. The method was tested by generation of an ensemble segmentation process for breast tumors in ultrasonic images. This was followed by a active contour to refine the extracted tumor boundary.The segmentation performance was evaluated by tenfold cross validation test, where 300 carcinomas, 50 fibroadenomas, and 50 cysts were used. The experimental results revealed that the error rate of the proposed ensemble segmentation was two-thirds the error rate of the segmentation trained by AdaBoost without MRF. By combining the ensemble segmentation with a geodesic active contour, the average Jaccard index between the extracted tumors and the manually segmented true regions was 93.41%, significantly higher than the conventional segmentation process.A cost-sensitive extension of AdaBoost based on MRF priors provides an efficient and accurate means for the segmentation of tumors in breast ultrasound images.
- Published
- 2010
37. On divisibility between Alexander polynomials of Turk’s head links
- Author
-
Atsushi Takemura
- Subjects
Combinatorics ,Algebra and Number Theory ,Head (linguistics) ,010102 general mathematics ,0103 physical sciences ,Alexander polynomial ,010307 mathematical physics ,Divisibility rule ,0101 mathematics ,Link (knot theory) ,01 natural sciences ,Mathematics - Abstract
We show that for any positive integers [Formula: see text] and [Formula: see text], the Alexander polynomial of the [Formula: see text]-Turk’s head link is divisible by that of the [Formula: see text]-Turk’s head link.
- Published
- 2018
38. Discrimination of Breast Tumors in Ultrasonic Images Using an Ensemble Classifier Based on the AdaBoost Algorithm With Feature Selection
- Author
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Atsushi Takemura, Akinobu Shimizu, and Kazuhiko Hamamoto
- Subjects
Databases, Factual ,Computer science ,ComputingMethodologies_IMAGEPROCESSINGANDCOMPUTERVISION ,Breast Neoplasms ,Feature selection ,Artificial Intelligence ,Breast Cyst ,Image Interpretation, Computer-Assisted ,Humans ,AdaBoost ,Electrical and Electronic Engineering ,Mahalanobis distance ,Radiological and Ultrasound Technology ,Contextual image classification ,Estimation theory ,business.industry ,Carcinoma ,Reproducibility of Results ,Pattern recognition ,Computer Science Applications ,Support vector machine ,ComputingMethodologies_PATTERNRECOGNITION ,Fibroadenoma ,Female ,Ultrasonography, Mammary ,Artificial intelligence ,business ,Classifier (UML) ,Algorithms ,Software ,K-distribution - Abstract
This paper proposes a novel algorithm to estimate a log-compressed K distribution parameter and presents an algorithm to discriminate breast tumors in ultrasonic images. We computed a total of 208 features for discrimination, including those based on a parameter of a log-compressed K-distribution, which quantifies the homogeneity of the echo pattern in the tumor, but is influenced by compression parameters in the ultrasonic device. The proposed algorithm estimates the parameter of the log-compressed K-distribution in a manner free from this influence. To quantify irregularities in tumor shape, pattern-spectrum-based features were newly developed in this paper. The discrimination process uses an ensemble classifier trained by a multiclass AdaBoost learning algorithm (AdaBoost.M2), combined with a sequential feature-selection process. A 10-fold cross-validation test validated the performance, and the results were compared with those of a Mahalanobis distance-based classifier and a multiclass support vector machine. A total of 200 carcinomas, 50 fibroadenomas, and 50 cysts were used in the experiments. This paper demonstrates that the combination of a classifier trained by AdaBoost.M2 and features based on the estimated parameter of a log-compressed K-distribution, as well as those of the pattern spectrum, are useful for the discrimination of tumors.
- Published
- 2010
39. Discrimination of Breast Tumors in Ultrasonic Images by Classifier Ensemble Trained with AdaBoost
- Author
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Atsushi Takemura, Akinobu Shimizu, and Kazuhiko Hamamoto
- Subjects
Computer Networks and Communications ,Computer science ,business.industry ,Applied Mathematics ,Speech recognition ,General Physics and Astronomy ,Pattern recognition ,medicine.disease ,Adaboost algorithm ,Fibroadenoma ,Breast tumor ,Signal Processing ,medicine ,Ultrasonic sensor ,AdaBoost ,Artificial intelligence ,Electrical and Electronic Engineering ,business ,Classifier (UML) - Abstract
In this paper, we propose a novel method for accurate automated discrimination of breast tumors (carcinoma, fibroadenoma, and cyst). We defined 199 features related to diagnostic observations noticed when a doctor judges breast tumors, such as internal echo, shape, and boundary echo. These features included novel features based on a parameter of log-compressed K distribution, which reflect physical characteristics of ultrasonic B-mode imaging. Furthermore, we propose a discrimination method of breast tumors by using an ensemble classifier based on the multiclass AdaBoost algorithm with effective features selection. Verification by analyzing 200 carcinomas, 30 fibroadenomas, and 30 cysts showed the usefulness of the newly defined features and the effectiveness of the discrimination by using an ensemble classifier trained by AdaBoost. © 2011 Wiley Periodicals, Inc. Electron Comm Jpn, 94(9): 18–29, 2011; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/ecj.10356
- Published
- 2009
40. Utility of Cardiac MRI in Pediatric
- Author
-
Atsushi Takemura
- Subjects
Male ,Pulmonary Circulation ,medicine.medical_specialty ,Heart Diseases ,business.industry ,Infant ,Coronary Disease ,General Medicine ,Mucocutaneous Lymph Node Syndrome ,Magnetic Resonance Imaging ,Text mining ,Child, Preschool ,Coronary Circulation ,Humans ,Medicine ,Female ,Medical physics ,Child ,business - Published
- 2007
41. E-LEARNING SYSTEM FOR ELECTRONIC CIRCUIT CONSTRUCTION USING HANDWRITING RECOGNITIONAND MIXED REALITY TECHNIQUES.
- Author
-
Atsushi Takemura
- Subjects
- *
HANDWRITING recognition (Computer science) , *ELECTRIC circuits , *MIXED reality , *MOBILE learning , *EDUCATIONAL technology - Abstract
This study proposes a novel e-learning system that can be used as a comprehensive learning resource for electronic circuits, covering design, theoretical analysis, and circuit construction experiments. The proposed system uses an automated recognition technique for schematic symbols that are handwritten on a touchscreen of a mobile tablet-type device and a mixed reality (MR) technique for technical experiments involving electronic circuit construction. The handwriting recognition technique improves the user-friendliness of the e-learning system, and the MR technique provides learners with a simulation of a circuit's operation (e.g., virtual measurements and machine control), which should effectively assist learners in constructing practical circuits. The effectiveness of the proposed system was verified by testing with 45 undergraduate students at Tokyo University of Agriculture and Technology. Positive results were received from all students, which indicate the usefulness of the proposed system. [ABSTRACT FROM AUTHOR]
- Published
- 2018
42. [Untitled]
- Author
-
Atsushi Takemura
- Subjects
Materials science ,chemistry ,Ultra-high vacuum ,Metallurgy ,chemistry.chemical_element ,Electrical and Electronic Engineering ,Condensed Matter Physics ,Surfaces, Coatings and Films ,Titanium - Published
- 2006
43. Synthesis of the EF-ring segment of ciguatoxin CTX1B based on novel regioselective reduction of unsaturated cyanohydrins and ring-closing olefin metathesis
- Author
-
Ken Shimawaki, Hidetoshi Kawai, Takanori Suzuki, Atsushi Takemura, Akio Murai, and Kenshu Fujiwara
- Subjects
Ciguatoxin ,Olefin metathesis ,Organic Chemistry ,Regioselectivity ,Total synthesis ,Tributyltin hydride ,Ring (chemistry) ,Biochemistry ,Silane ,Reduction (complexity) ,chemistry.chemical_compound ,chemistry ,Drug Discovery ,Organic chemistry - Abstract
Aiming at a convergent total synthesis of ciguatoxin CTX1B, its EF-ring segment has been synthesized. During the synthesis, a novel method for the construction of branched ethers, based on regioselective reduction of γ-alkoxy β,γ-unsaturated α-silyloxy nitriles with borontrifluoride etherate and trialkyl silane or tributyltin hydride, has been developed. Combination use of the method and ring-closing olefin metathesis successfully provided medium-sized cyclic ethers. Efficient site-selective reduction of vinyl epoxides into homoallyl alcohols has also been developed.
- Published
- 2005
44. Automatic Generating Algorithm of Locally Adaptive Smoothing Filter-An Application to Speckle Suppression of Ultrasonic Images
- Author
-
Atsushi Takemura
- Subjects
Speckle pattern ,Computer science ,Filter (video) ,business.industry ,Adaptive smoothing ,Computer vision ,Ultrasonic sensor ,Artificial intelligence ,Electrical and Electronic Engineering ,business - Published
- 2005
45. Novel branched ether formation via conjugate reduction of an unsaturated cyanohydrin derivative and its synthetic application to the EF-ring segment of ciguatoxin
- Author
-
Atsushi Takemura, Kenshu Fujiwara, Hidetoshi Kawai, Akio Murai, and Takanori Suzuki
- Subjects
Nitrile ,Chemistry ,Stereochemistry ,Organic Chemistry ,Alcohol ,Ether ,Ring (chemistry) ,Biochemistry ,chemistry.chemical_compound ,Drug Discovery ,Selective reduction ,Derivative (chemistry) ,Cyanohydrin ,Conjugate - Abstract
A synthetic method for a branched ether system was developed. The method was based on Lewis-acid-promoted γ-position selective reduction of a γ-alkoxy β,γ-unsaturated α-silyloxy nitrile, prepared through a process including intermolecular hetero-Michael reaction of a 2-butynoate ester derivative with an alcohol. The method was efficiently applied to the synthesis of fused medium-ring ethers involving the EF-ring segment ( 2 ) of ciguatoxin ( 1 ).
- Published
- 2004
46. Coordinate anionic ring-opening polymerization of oxetanes with aluminum benzyl alcoholate bis(2,6-di-tert-butyl-4-methylphenolate)
- Author
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Atsushi Takemura, Masatoshi Motoi, Charoen Chinwanitcharoen, Koh-ichi Fukuda, and Shigeyoshi Kanoh
- Subjects
Polymers and Plastics ,Chemistry ,Organic Chemistry ,Cationic polymerization ,Solution polymerization ,Ring-opening polymerization ,chemistry.chemical_compound ,Anionic addition polymerization ,Polymerization ,Benzyl alcohol ,Polymer chemistry ,Materials Chemistry ,Lewis acids and bases ,Boron trifluoride - Abstract
Aluminum benzyl alcoholate bis(2,6-di-tert-butyl-4-methylphenolate) (BnOAD), which was prepared through the mixing of equimolar amounts of benzyl alcohol and methylaluminum bis(2,6-di-tert-butyl-4-methylphenolate) (MAD), successfully polymerized four-membered cyclic ethers in a coordinate anionic ring-opening manner. The polymerization of 3-(4-bromobutoxymethyl)-3-methyloxetane (OxBr) with 5 mol % BnOAD proceeded slowly in toluene at 25 °C and produced sufficiently high-molecular-weight poly(OxBr) in a moderate yield in 24 h. The polymerization was greatly accelerated by the addition of a sterically hindered Lewis acid such as MAD, and this resulted in a nearly quantitative polymer yield within 24 h. In sharp contrast, conventional cationic polymerization with boron trifluoride etherate as a typical Lewis acid initiator produced low-molecular-weight poly(OxBr) along with a substantial amount of the cyclic tetramer. The polymerization of the simplest unsubstituted oxetane with BnOAD resulted in failure.
- Published
- 2004
47. [Untitled]
- Author
-
Yoji Muroo, Atsushi Takemura, Yoshihide Morimoto, Masahiko Uota, Yoshio Saito, and Yoshihiro Sato
- Subjects
Surface (mathematics) ,chemistry.chemical_compound ,Materials science ,chemistry ,Oxide ,chemistry.chemical_element ,Vacuum chamber ,Electrical and Electronic Engineering ,Composite material ,Condensed Matter Physics ,Surfaces, Coatings and Films ,Titanium - Published
- 2004
48. Fission-Track ages of the Miocene Shiomachi Formation in the Miyoshi Area, Hiroshima Prefecture, South-west Japan
- Author
-
Tohru Danhara, Hideki Iwano, Takaaki Matsuda, Atsushi Takemura, and Makoto Miyake
- Subjects
General Engineering ,General Earth and Planetary Sciences ,Fission track dating ,Archaeology ,Geology ,General Environmental Science - Abstract
広島県三次盆地の中新統備北層群は,下位より塩町,是松,板橋の3累層に区分される.従来,非海成の塩町累層からは年代のデータがなかったため,フィッション・トラック法による年代測定を行った.塩町累層の凝灰岩層の2試料からは信頼できる年代値が得られ,前期中新世初頭の約22~23Maである.是松累層は微化石などのデータより約16Maであり,塩町累層との層序関係は平行不整合であると考えられる.また中国地方中央部には,古第三系以外に中新世前期の陸成層も存在することが明らかになった.
- Published
- 2003
49. Segmentation of ultrasonic images by using locally adaptive filter and wavelet analysis: Detection of superficial peripheral vein by a high-frequency ultrasonic equipment
- Author
-
Atsushi Takemura and Masayasu Ito
- Subjects
Engineering ,business.industry ,Image processing ,Filter (signal processing) ,Adaptive filter ,Speckle pattern ,Wavelet ,Computer vision ,Ultrasonic sensor ,Segmentation ,Artificial intelligence ,Electrical and Electronic Engineering ,Focus (optics) ,business - Abstract
Ultrasonic diagnostic equipment is widely used, but has many problems such as acquiring noisy images and poorly quantifying the results for diagnosis. Therefore, a great deal of research has addressed the image processing of medical ultrasound images because of the need for automation and quantification of the diagnosis. This research began with the problem of region segmentation that automatically identifies living tissue or focus mass and currently relates to the quantification of tissue region information with the objective of tissue property diagnosis and the automatic diagnosis of 3D images. To achieve this, an accurate contour extraction method must be established. In this research, to achieve accurate region segmentation without losing the contour information in the medical ultrasound diagnostic images, we propose a new method based on an adaptive smoothing filter for suppressing speckle patterns and the 2D Gabor wavelet transform. Then we tried to automatically detect a superficial peripheral vein from an image of the forearm obtained by high-frequency ultrasonic diagnostic equipment, which is a difficult problem for conventional image analysis techniques. © 2002 Wiley Periodicals, Inc. Electron Comm Jpn Pt 3, 86(1): 36–45, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjc.10026
- Published
- 2002
50. Triassic radiolarians from the ocean‐floor sequence of the Waipapa Terrane at Arrow Rocks, Northland, New Zealand
- Author
-
Yoshiaki Aita, Toyosaburo Sakai, K. Bernhard Spörli, Rie S. Hori, Yasushi Higuchi, Hamish J. Campbell, Kazuto Kodama, and Atsushi Takemura
- Subjects
Basalt ,Sequence (geology) ,Plate tectonics ,Paleontology ,Geophysics ,Permian ,Earth and Planetary Sciences (miscellaneous) ,Geology ,Palaeogeography ,Oil shale ,Terrane ,Latitude - Abstract
Triassic radiolarians are reported from two horizons in Waipapa Terrane at Arrow Rocks, Whangaroa area, Northland. This relatively undisturbed succession represents an ocean‐floor sequence, consisting (in ascending order) of basalt with limestone layers, bedded chert, black shale, and red, maroon and green siliceous mudstone. The age of the lower part of the section is Middle‐Late Permian. The radiolarian assemblages reported here indicate Early or Middle Triassic and Middle Triassic (Anisian) ages for maroon siliceous mudstones in the upper part of the section. Between strata of known Permian and Triassic age there is a thin potential Permian/Triassic boundary interval consisting of alternating black shale and grey chert. Radiolarian paleogeography indicates that the Arrow Rocks sequence experienced long distance plate tectonic displacement from a position of relatively low latitude in the Middle Permian and to a high latitude in mid‐Triassic time.
- Published
- 2002
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