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Tsukuba, Japan

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

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. Source

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

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. Source

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

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. Source

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

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. Source

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

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. Source

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