Katsumi Kose

Development of a 1.0 T MR microscope using a Nd-Fe-B permanent magnet

A compact 1.0 T MR microscope was developed using a permanent magnet made of high performance Nd-Fe-B magnetic material and a compact MRI console (54 cm (W) x 77 cm (H) x 60 cm (D), 80 kg weight). Since the magnetic field of the permanent magnet had a large temperature coefficient (-1200 ppm/deg), an internal NMR locking technique was developed for the imaging sequences. The performance of the system was evaluated using several biological specimens. As a result, good SNR 3D images at (50 microm)(3)-(200 microm)(3) voxel dimensions were obtained in practical imaging times (0.5-7.5 hours). Thus we have concluded that the permanent-magnet compact MR microscope has great promise as a research or analytical tool.

Super‐parallel MR microscope

A super‐parallel MR microscope in which multiple (up to 100) samples can be imaged simultaneously at high spatial resolution is described. The system consists of a multichannel transmitter–receiver system and a gradient probe array housed in a large‐bore magnet. An eight‐channel MR microscope was constructed for verification of the system concept, and a four‐channel MR microscope was constructed for a practical application. Eight chemically fixed mouse fetuses were simultaneously imaged at the 200 μm3 voxel resolution in a 1.5 T superconducting magnet of a whole‐body MRI, and four chemically fixed human embryos were simultaneously imaged at 120 μm3 voxel resolution in a 2.35 T superconducting magnet. Although the spatial resolutions achieved were not strictly those of MR microscopy, the system design proposed here can be used to attain a much higher spatial resolution imaging of multiple samples, because higher magnetic field gradients can be generated at multiple positions in a homogeneous magnetic field. Magn Reson Med 50:183–189, 2003.

NMR Flow Imaging

The present study describes a method for measuring a spatial distribution of flow velocity in fluid. This method employs two selective irradiation pulses; the first pulse is used for selective saturation and the second pulse is used for selective observation. To image flowing fluid correctly, images are reconstructed from a set of second echoes in a pulse sequence similar to Carr-Purcell-Meiboom-Gill sequence. The velocity image is computed using two images; one is that of the nuclear spin density and the other is that with 100 msec delay time between the two selective irradiation pulses. The obtained velocity distribution of water in a circular pipe is parabolic and agrees well with that of Poiseuille flow, which has proved the method developed here of great use in the study of fluid flow.

Architecture of baked breads depicted by a magnetic resonance imaging

The architecture of baked breads made of fresh dough and frozen dough was depicted by magnetic resonance imaging (MRI). Pieces of bread (16 mm cubic cakes) were soaked in organic solvents containing various concentrations of heavy metals (Cu(2+), Co(2+) and Fe(3+)) and images of the grain structure of the breads were obtained. Of the organic solvents tested, acetone was preferable because of its single peak that prevents chemical shift effects on images, the retention of the bread structure, and the solubility of heavy metals. The heavy metals, especially Fe(3+), shortened the overly long relaxation times of acetone to practical lengths for imaging and stained the materials to provide high contrasts. The images obtained in acetone with 8 mM Fe(3+) were suitable for analyzing crumb grain structures. The bread of fresh dough showed a uniform distribution of pores of various sizes made of thin gluten sheets, whereas the pores in the bread of frozen dough were less, prominently large, non-uniformly distributed, and made of thick gluten sheets.

Skeletal Age Assessment in Children Using an Open Compact MRI System

MRI may be a noninvasive and alternative tool for skeletal age assessment in children, although few studies have reported on this topic. In this article, skeletal age was assessed over a wide range of ages using an open, compact MRI optimized for the imaging of a childs hand and wrist, and its validity was evaluated. MR images and their three‐dimensional segmentation visualized detailed skeletal features of each bone in the hand and wrist. Skeletal age was then independently scored from the MR images by two raters, according to the Tanner–Whitehouse Japan system. The skeletal age assessed by MR rating demonstrated a strong positive correlation with chronological age. The intrarater and inter‐rater reproducibilities were significantly high. These results demonstrate the validity and reliability of skeletal age assessment using MRI. Magn Reson Med, 2013.

Development of a magnetic resonance microscope using a high Tc bulk superconducting magnet

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 EuBa2Cu3Oy 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.

Graphic and movie illustrations of human prenatal development and their application to embryological education based on the human embryo specimens in the Kyoto collection

Morphogenesis in the developing embryo takes place in three dimensions, and in addition, the dimension of time is another important factor in development. Therefore, the presentation of sequential morphological changes occurring in the embryo (4D visualization) is essential for understanding the complex morphogenetic events and the underlying mechanisms. Until recently, 3D visualization of embryonic structures was possible only by reconstruction from serial histological sections, which was tedious and time‐consuming. During the past two decades, 3D imaging techniques have made significant advances thanks to the progress in imaging and computer technologies, computer graphics, and other related techniques. Such novel tools have enabled precise visualization of the 3D topology of embryonic structures and to demonstrate spatiotemporal 4D sequences of organogenesis. Here, we describe a project in which staged human embryos are imaged by the magnetic resonance (MR) microscope, and 3D images of embryos and their organs at each developmental stage were reconstructed based on the MR data, with the aid of computer graphics techniques. On the basis of the 3D models of staged human embryos, we constructed a data set of 3D images of human embryos and made movies to illustrate the sequential process of human morphogenesis. Furthermore, a computer‐based self‐learning program of human embryology is being developed for educational purposes, using the photographs, histological sections, MR images, and 3D models of staged human embryos. Developmental Dynamics 235:468–477, 2006.

NMR imaging of advanced ceramics during the slip casting process

The slip casting process in advanced ceramics was observed using an NMR imaging system. After the Al2O3 water suspension (Al2O3 slip) was poured into the mould, cross section of the mould was imaged. In the sequentially taken NMR images the Al2O3 slip was clearly distinguishable from the deposit because of the difference in relaxation time T2 and an increase of the deposit thickness with time was observed. These results indicate that NMR imaging is useful in the nondestructive monitoring of the slip casting process.

Development of a mobile magnetic resonance imaging system for outdoor tree measurements

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 T(1), T(2), 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.

NMR imaging of turbulent structure in a transitional pipe flow

One-shot NMR imaging with a very short data acquisition time ( approximately 20 ms) is used to reveal the structure of a turbulent equilibrium puff in a transitional pipe flow. Longitudinal vortices in the downstream region of a puff are very clearly visualised in the NMR images. The structure of a puff derived from the images agrees with that suggested by a flow visualisation experiment done previously. The present study demonstrates that one-shot NMR imaging is a very powerful tool in visualising large-scale coherent structures in turbulent flow.