Tsukuba, Japan
Tsukuba, Japan

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Umebayashi T.,Tokyo University of Science | Umebayashi T.,Japan National Agriculture and Food Research Organization | Fukuda K.,Tokyo University of Science | Haishi T.,MRTechnology Inc. | And 3 more authors.
Plant Physiology | Year: 2011

In pine wilt disease (PWD), embolized tracheids arise after virulent pine wood nematodes (PWN), Bursaphelenchus xylophilus, invade the resin canal of pine tree; infected pine trees finally die from significant loss of xylem water conduction. We used a compact magnetic resonance imaging system with a U-shaped radio frequency (rf) probe coil to reveal the developmental process of the xylem dysfunction in PWD. Multiple cross-sectional slices along the stem axis were acquired to periodically monitor the total water distribution in each 1-year-old main stem of two 3-year-old Japanese black pines (Pinus thunbergii) after inoculation of PWN. During the development of PWD, a mass of embolized tracheids around the inoculation site rapidly enlarged in all directions. This phenomenon occurred before the significant decrease of water potential. Some patch-like embolisms were observed at all monitoring positions during the experimental period. Patchy embolisms in a cross-section did not expand, but the number of patches increased as time passed. When the significant decrease of water potential occurred, the xylem dysfunctional rate near the inoculation point exceeded 70%. Finally, almost the whole area of xylem was abruptly embolized in all cross-sections along the stem. This phenomenon occurred just after water conduction was mostly blocked in one of the cross-sections. Thus, it appears that the simultaneous expansion of embolized conduit clusters may be required to induce a large-scale embolism across the functional xylem. Consequently, xylem dysfunction in infected trees may be closely related to both the distribution and the number of PWN in the pine stem. © 2011 American Society of Plant Biologists.


Kose K.,University of Tsukuba | Haishi T.,MRTechnology Inc.
Magnetic Resonance in Medical Sciences | Year: 2011

We measured the homogeneity and stability of the magnetic field of a high field (about 1.04 tesla) yokeless permanent magnet with 40-mm gap for high resolution nuclear magnetic resonance (NMR) imaging. Homogeneity was evaluated using a 3-dimensional (3D) lattice phantom and 3D spin-echo imaging sequences. In the central sphere (20-mm diameter), peak-to-peak magnetic field inhomogeneity was about 60 ppm, and the root-mean-square was 8 ppm. We measured room temperature, magnet temperature, and NMR frequency of the magnet simultaneously every minute for about 68 hours with and without the thermal insulator of the magnet. A simple mathematical model described the magnet's thermal property. Based on magnet performance, we performed high resolution (up to [20 mm] 2) imaging with internal NMR lock sequences of several biological samples. Our results demonstrated the usefulness of the high field small yokeless permanent magnet for high resolution NMR imaging.


Ogawa K.,Keio University | Haishi T.,MRTechnology Inc. | Itoc K.,Kyushu University
Journal of the Electrochemical Society | Year: 2014

In order to understand the water transport phenomenon in a membrane electrode assembly (MEA), the water transfer resistance through a platinum catalyst layers (CL) is required. In this study, the overall water transfer resistance through the CL is taken as the sum of the resistance to charge/discharge water from the surface of ionomer in the CL and the resistance for water to pass through the ionomer in the CL. The value of this quantity for a CL that is 4 [im thick and is coated on a 178 [im thick Nation 117, was estimated. The MEA was dried/wetted by supplying gas with controlled humidity to the surface of the MEA. The water concentration contained in the PEM was measured by nuclear magnetic resonance (NMR) using a small detection coil. The rates of drying/wetting of the MEA were calculated from time-dependent changes of the water concentration measured in the PEM. The overall water transfer resistance through a CL was estimated by comparing experiment and analytical results based on the analytical model. As a result, the overall water transfer resistances through the 4 [im thick CL during drying and wetting were 0-3 x 104 and 10 ± 6 x 104 s/m, respectively. © 2013 The Electrochemical Society. All rights reserved.


Tamada D.,University of Tsukuba | Kose K.,University of Tsukuba | Haishi T.,MRTechnology Inc.
Applied Physics Express | Year: 2012

We propose a new planar single-channel shim coil for magnetic resonance imaging (MRI) permanent magnets. The coil design is based on the superposition of multiple circular currents and the stream function method. The designed shim coil was implemented for a permanent magnet with 1.0T and a 90 mm gap. When the shim coil current was optimized, the magnetic field inhomogeneity decreased from 240 to 97ppm (peak-to-peak) in the central cylindrical area (54.6 mm diameter, 60.0 mm height), demonstrating that the single-channel shim coil proposed here is a useful device for permanent narrow-gap magnets with complicated magnetic field distribution. © 2012 The Japan Society of Applied Physics.


Hashimoto S.,University of Tsukuba | Kose K.,University of Tsukuba | Haishi T.,MRTechnology Inc.
Review of Scientific Instruments | Year: 2012

We have developed a pulse programmer for magnetic resonance imaging (MRI) using a personal computer and a commercially available high-speed digital input-output board. The software for the pulse programmer was developed using CC and.NET Framework 2.0 running under the Windows 7 operating system. The pulse programmer was connected to a digital MRI transceiver using a 32-bit parallel interface, and 128-bit data (16 bits × 8 words) for the pulse sequence and the digitally detected MRI signal were transferred bi-directionally every 1 μs. The performance of the pulse programmer was evaluated using a 1.0 T permanent magnet MRI system. The acquired MR images demonstrated the usefulness of the pulse programmer. Although our pulse programmer was developed for a specially designed digital MRI transceiver, our approach can be used for any MRI system if the interface for the transceiver is properly designed. Therefore, we have concluded that our approach is promising for MRI pulse programmers. © 2012 American Institute of Physics.


Ogawa K.,University of Tsukuba | Nakamura T.,RIKEN | Terada Y.,University of Tsukuba | Kose K.,University of Tsukuba | Haishi T.,MRTechnology Inc.
Applied Physics Letters | Year: 2011

We have developed the first magnetic resonance (MR) microscope using a high critical-temperature superconducting bulk magnet. The bulk magnet comprises six annular bulk superconductors (60 mm outer diameter, 28 mm inner diameter, 20 mm high) made of c-axis oriented single-domain EuBa2 Cu3 Oy crystals. The magnet was energized using a superconducting NMR magnet operating at 4.7 T. The inhomogeneity of the trapped magnetic field measured with MR imaging was 3.1 ppm (rms) in the φ6.2 mm×9.1 mm cylindrical region. Three-dimensional MR images of a chemically fixed mouse embryo acquired with voxels of (50 μm)3 demonstrated the potential of our system. © 2011 American Institute of Physics.


Kimura T.,University of Tsukuba | Geya Y.,University of Tsukuba | Terada Y.,University of Tsukuba | Kose K.,University of Tsukuba | And 3 more authors.
Review of Scientific Instruments | Year: 2011

By combining a 0.3 T permanent magnet with flexible rotation and translation mechanism, a probe with a local electromagnetic shielding, several electrical units, a mobile lift, and an electric wagon, a mobile magnetic resonance imaging (MRI) system was developed for outdoor tree measurements. 2D cross-sectional images of normal and diseased branches of a pear tree were acquired for measurements of T1, T2, proton density, and apparent diffusion constant (ADC). The ADC map clearly differentiated diseased from normal branches. A whole-day measurement of the ADC map demonstrated that microscopic water flow in the normal branch changed proportionally with solar radiation. Therefore, we have concluded that our mobile MRI system is a powerful tool for studies of plants in outdoor environments. © 2011 American Institute of Physics.


Patent
MRTechnology Inc. | Date: 2014-01-15

The imaging device includes an imaging unit producing images, and a control unit controlling the imaging unit. The imaging device further comprises: a reference clock unit generating a reference clock; and a signal input/output unit provided between the imaging unit and the control unit and inputting and outputting signals in synchronization with the reference clock generated by the reference clock unit. The control unit comprises: generating means generating a plurality of control signals for controlling the imaging unit and generating an extraction timing of extracting measurement signals from the imaging unit; transmitting means transmitting the plural control signals generated by the generating means to the imaging unit via the signal input/output unit in synchronization with the reference clock; receiving means receiving measurement signals from the imaging unit via the signal input/output unit in synchronization with the reference clock and counting reception times of the measurement signals; and extraction means extracting the measurement signal when the reception times of the measurement signals received by the receiving means agrees with the extraction timing generated by the generating means.


Patent
MRTechnology Inc. | Date: 2014-12-03

The present invention provides an imaging unit which can image small animals inexpensively and with high resolution. The imaging detector 22 of the imaging unit includes gradient magnetic field coils having a pair of bucket-shaped coils 51-53, 61-63 having the bottoms opposed to each other and generating gradient magnetic fields between the par of bucket-shaped coils 51-53, 61-63, and a detection coil 82 accommodated between the pair of bucket-shaped coils 51-53, 61-63, a housing portion 30 provided between the pair of bucket-shaped coils 51-53, 61-63 and housing an object to be imaged, and a detection coil 82 provided in the housing portion 30 and positioned near the housed object to be imaged.


Patent
MRTechnology Inc. | Date: 2012-12-12

The imaging device includes an imaging unit producing images, and a control unit controlling the imaging unit. The imaging device further comprises: a reference clock unit generating a reference clock; and a signal input/output unit provided between the imaging unit and the control unit and inputting and outputting signals in synchronization with the reference clock generated by the reference clock unit. The control unit comprises: generating means generating a plurality of control signals; transmitting means transmitting the plural control signals; receiving means receiving measurement signals; and extraction means extracting the measurement signal when the reception times of the measurement signals received by the receiving means agrees with the extraction timing generated by the generating means.

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