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Purpose: The aim of this study was to establish a distortion correction applicable to whole-body imaging of live mice.Materials and Methods: All magnetic resonance imaging (MRI) scans were acquired on a compact 1-T permanent magnet unit for mouse imaging using a T1-weighted, three-dimensional (3D) fast low-angle shot sequence. We assessed geometric distortion in MR images of a small 3D grid phantom and determined 3D image transformations for distortion correction. The developed distortion correction was applied to MR images of the 3D grid phantom acquired on another day, and the correction was validated. A two-dimensional (2D) grid phantom was imaged with a mouse to investigate the applicability of the distortion correction to whole-body mouse imaging.Results: Obvious geometric distortion was observed in the MR images of the 3D grid phantom. The application of the developed 3D phantom-based distortion correction reduced distortion in the images of the 3D grid phantom acquired on another day. Geometric distortion was observed in the MR images of the 2D grid phantom acquired together with the mouse. The 3D phantom-based correction decreased the distortion substantially, regardless of mouse positioning.Conclusion: The developed distortion correction can reduce distortion in whole-body imaging of live mice and may enhance the capabilities of MRI in small animal experiments. [ABSTRACT FROM AUTHOR]

23 Na-MRI provides information on Na + content, and its application in the medical field has been highly anticipated. However, for existing clinical 1 H-MRI systems, its implementation requires an additional broadband RF transmitter, dedicated transceivers, and RF coils for Na + imaging. However, a standard medical MRI system cannot often be modified to perform 23 Na imaging. We have developed an add-on crossband RF repeater system that enables 23 Na-MRI simply by inserting it into the magnet bore of an existing 1 H MRI. The three axis gradient fields controlled by the 1 H-MRI system were directly used for 23 Na imaging without any deformation. A crossband repeater is a common technique used for amateur radio. This concept was proven by a saline solution phantom and in vivo mouse experiments. This add-on RF platform is applicable to medical 1 H MRI systems and can enhance the application of 23 Na-MRI in clinical usage.

We have developed a new device, consisting of a 3-cm RF coil and an immobilizer, to acquire high-resolution MR images of the testis. With the approval of our institutional review board, we conducted an MRI study on a cohort of healthy volunteers to test this device. With the participants in the supine position, we placed the dedicated immobilizer and RF coil on the scrotum for typically no more than 3 min. Subsequently, T2-weighted images were acquired with an in-plane resolution of 117 µm using a 3-T MR scanner and the periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) sequence. The total scan time ranged from 12 to 30 min (average 20 min). High-resolution MR images of the testis were acquired without deterioration by motion artifacts. Our results showed that the combined use of a small RF coil and an immobilizer is a feasible option for acquiring high-resolution MR images of the testis.

The dynamic behavior of alkali metal ions, Li + , Na + , K + , Rb + and Cs + in aqueous solutions is one of the most important topics in solution chemistry. Since these alkali metals contain nuclear magnetic resonance (NMR) active nuclei, it is possible to directly measure the diffusion constants of the alkali metal ions using the pulsed field gradient (PFG) NMR method. In this paper, the 7 Li, 23 Na, 87 Rb, 133 Cs and 1 H resonances are observed for diffusion constants in aqueous solution and the solvent H 2 O. Until now, the values of the diffusion constant have been lacking when discussing hydration effects around alkali metal ions. It is known that the static ionic radius ( R ion ) increases with increasing the atomic number, and the experimental diffusion constants also increase with increasing the atomic number, which is opposite to the Stokes-Einstein (SE) relation. It suggests that alkali metal ions diffuse through a space of 10 -6 m accompanying the hydrated spheres with a time interval of 10 -3 s. For each alkali metal ion, the dynamic ionic radius is evaluated., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Ion-conducting garnets are important candidates for use in all-solid Li batteries and numerous materials have been synthesized with high ionic conductivities. For understanding ion conduction mechanisms, knowledge on Li + diffusion behaviour is essential. The proposed nano-scale lithium pathways are composed of tortuous and narrow Li + channels. The pulsed gradient spin-echo (PGSE) NMR method provides time-dependent 7 Li diffusion on the micrometre space. For powder samples, collision-diffraction echo-attenuation plots were observed in a short observation time, which had not been fully explained. The diffraction patterns were reduced or disappeared for single-crystal garnet samples of Li 6.5 La 3 Zr 1.5 Ta 0.5 O 12 (LLZO-Ta) and Li 6.5 La 3 Zr 1.5 Nb 0.5 O 12 (LLZO-Nb). The inner morphology and grain boundaries affect importantly the collision-diffraction behaviours which is inherent to powder samples. The 7 Li diffusion observed by PGSE-NMR depends on the observation time (Δ) and the pulsed field gradient (PFG) strength (g) in both powder and single-crystal samples, and the anomalous effects were reduced in the single-crystal samples. The scattered Li diffusion constants converged to a unique value (D Li ) with a long Δ and a large g, which is eventually the smallest value. The D Li activation energy was close to that of the ionic conductivity (σ). The D Li values are plotted versus the σ values measured for four powder and two single-crystal garnet samples. Assuming the Nernst-Einstein (NE) relation which was derived for isolated ions in solution, the carrier numbers (N NE ) were estimated from the experimental values of D Li and σ. The N NE values of metal-containing garnets were large (<10 23 cm -3 ) and insensitive to temperature. They were larger than Li atomic numbers in cm 3 calculated from the density, molecular formula and Avogadro number for LLZOs except for cubic LLZO (Li 7 La 3 Zr 2 O 12 , N NE ∼ 10 20 cm -3 ).

The migration behaviours of Li+ in three garnet- and one NASICON-type solid oxide electrolytes were studied on the micrometre scale by pulsed-gradient spin-echo (PGSE) 7Li NMR diffusion spectroscopy to clarify common and specific characteristics of each electrolyte. In these solid electrolytes, clear evidences of grain boundary effects in the diffusion of Li+ were not observed. The Li+ diffusion constants were dependent on parameters such as observation time (Δ) and pulsed field gradient (PFG) strength (g) for all the studied inorganic solid electrolytes. For low Δ values, Li+ ions underwent collisions and diffractions with diffraction distance Rdiffraction [μm]. The apparent Li+ diffusion constants (Dapparent [m2 s-1]) exhibited distributions in a wide range. In this paper, we introduced the apparent diffusion radius, rradius [μm], and compared it with Rdiffraction and mean square displacement (MSD) [μm]; the lengths of these distances were of the micrometre order (10-6 m). The relations between the values of rradius, Rdiffraction and MSD suggested that the migration behaviours of Li+ on the micrometre scale were complicated. Using high Δ and high g values, we obtained an equilibrated value of DLi. The temperature dependences of the number of carrier ions were estimated from the DLi values and ionic conductivities in the four solid oxide electrolytes. For simple comparison and reference, the data of DLi and ionic conductivity of LiPF6 in 1 M solution of propylene carbonate were added.

Mobile lithium ions in a cubic garnet Li 7 La 3 Zr 2 O 12 (Al-stabilized) were studied using 7 Li NMR spectroscopy for membrane and powder samples, the latter of which was ground from the membrane. Lithium diffusion in a micrometer space was measured using the pulsed-gradient spin-echo 7 Li NMR method between 70 and 130 °C. When the observation time (Δ) was shorter than 20 ms, the echo attenuation showed diffusive diffraction patterns, indicating that the Li + diffusing space is not free but restricted. For longer Δ, the values of apparent diffusion constant (D apparent ) became gradually smaller to approach an equilibrated value (close to a tracer diffusion constant). In addition, the D apparent depends on the pulse field gradient strength (g) and became smaller as g became larger. These experimental results suggest that the lithium ions diffuse through Li + pathways surrounded by stationary anions and lithium ions, and are affected by collisions and diffractions. One-dimensional profiles of the membrane sample of thickness 0.5 mm were observed from 65 to 110 °C and the area intensity, as well as the lithium occurrence near the surface, increased with the increase in temperature. The temperature-dependent area intensity showed a correspondence to the number of Li + carrier ions estimated from the ionic conductivity and the equilibrated diffusion constant through the Nernst-Einstein relationship.

A small radio-frequency (rf) coil inserted into a polymer electrolyte fuel cell (PEFC) can be used to acquire nuclear magnetic resonance (NMR) signals from the water in a membrane electrode assembly (MEA) or in oxygen gas channels in the PEFC. Measuring the spatial distribution of the water in a large PEFC requires using many rf probes, so an NMR measurement system which acquires NMR signals from 128 rf probes at intervals of 0.5 s was manufactured. The system has eight rf transceiver units with a field-programmable gate array (FPGA) for modulation of the excitation pulse and quadrature phase detection of the NMR signal, and one control unit with two ring buffers for data control. The sequence data required for the NMR measurement were written into one ring buffer. The acquired NMR signal data were then written temporarily into the other ring buffer and then were transmitted to a personal computer (PC). A total of 98 rf probes were inserted into the PEFC that had an electrical generation area of 16 cm × 14 cm, and the water generated in the PEFC was measured when the PEFC operated at 100 A. As a result, time-dependent changes in the spatial distribution of the water content in the MEA and the water in the oxygen gas channels were obtained.

Although previous studies have suggested that branch dieback and whole-plant death due to drought stress occur at 50-88% loss of stem hydraulic conductivity (P 50 and P 88 , respectively), the dynamics of catastrophic failure in the water-conducting pathways in whole plants subjected to drought remain poorly understood. We examined the dynamics of drought stress tolerance in 3-year-old Japanese black pine (Pinus thunbergii Parl.). We nondestructively monitored (i) the spatial distribution of drought-induced embolisms in the stem at greater than P 50 and (ii) recovery from embolisms following rehydration. Stem water distributions were visualized by cryo-scanning electron microscopy. The percentages of both embolized area and loss of hydraulic conductivity showed similar patterns of increase, although the water loss in xylem increased markedly at -5.0 MPa or less. One seedling that had reached 72% loss of the water-conducting area survived and the xylem water potential recovered to -0.3 MPa. We concluded that Japanese black pines may need to maintain water-filled tracheids within earlywood of the current-year xylem under natural conditions to avoid disconnection of water movement between the stem and the tops of branches. It is necessary to determine the spatial distribution of embolisms around the point of the lethal threshold to gain an improved understanding of plant survival under conditions of drought., (© The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Development of xylem embolism during water stress in two diffuse-porous hardwoods, Katsura (Cercidiphyllum japonicum) and Japanese white birch (Betula platyphylla var. japonica), was observed non-destructively under a compact magnetic resonance imaging (MRI) system in addition to conventional quantitation of hydraulic vulnerability to cavitation from excised stem segments. Distribution of white and dark areas in MR images corresponded well to the distribution of water-filled/embolized vessels observed by cryo-scanning electron microscopy in both species. Water-filled vessels were observed in MR images as white areas in Katsura and as white dots in Japanese white birch, respectively, and embolisms could be detected as a change to dark areas. The increase in the relative embolized area (REA: %) in the cross-sectional area of total xylem during water stress, which was estimated from the binarized MR images, was consistent with the hydraulic vulnerability curves of these species. From the non-destructive MRI observations, cavitation induced by water stress was shown to develop earlier in 1- or 2-year-old xylem than in the current-year xylem in both species; that is, the vulnerability to cavitation differs between vessels in the current-year xylem and those in older annual rings., (© 2015 John Wiley & Sons Ltd.)

We constructed an arm holder for muscle exercise from a forearm-shaped plastic shell and magnetic resonance (MR) imaging position markers and determined the echo time (39 ms) for T₂-weighted spin-echo MR imaging from T₂values of the exercised (50 ms) and resting (32 ms) muscle at 0.2 tesla. The smallest detectable muscle was the extensor digiti minimi muscle (cross-sectional area 25 mm²). This combination could be useful to monitor finger exercise in patients undergoing physical therapy.

We critically evaluated analog and digital transceivers for magnetic resonance (MR) imaging systems under identical experimental conditions to identify and compare their advantages and disadvantages. MR imaging experiments were performed using a 4.74-tesla vertical-bore superconducting magnet and a high sensitivity gradient coil probe. We acquired 3-dimensional spin echo images of a kumquat with and without using a gain-stepping scan technique to extend the dynamic range of the receiver systems. The acquired MR images clearly demonstrated nearly identical image quality for both transceiver systems, but DC and ghosting artifacts were obtained for the analog transceiver system. We therefore concluded that digital transceivers have several advantages over the analog transceivers.

The water generation and water transport occurring in a polymer electrolyte fuel cell (PEFC) can be estimated from the current density generated in the PEFC, and the water content in the polymer electrolyte membrane (PEM). In order to measure the spatial distributions and time-dependent changes of current density generated in a PEFC and the water content in a PEM, we have developed an eight-channel nuclear magnetic resonance (NMR) system. To detect a NMR signal from water in a PEM at eight positions, eight small planar RF detection coils of 0.6 mm inside diameter were inserted between the PEM and the gas diffusion layer (GDL) in a PEFC. The local current density generated at the position of the RF detection coil in a PEFC can be calculated from the frequency shift of the obtained NMR signal due to an additional magnetic field induced by the local current density. In addition, the water content in a PEM at the position of the RF detection coil can be calculated by the amplitude of the obtained NMR signal. The time-dependent changes in the spatial distributions were measured at 4 s intervals when the PEFC was operated with supply gas under conditions of fuel gas utilization of 0.67 and relative humidity of the fuel gas of 70%RH. The experimental result showed that the spatial distributions of the local current density and the water content in the PEM within the PEFC both fluctuated with time., (Copyright © 2013 The Authors. Published by Elsevier Inc. All rights reserved.)

Longitudinal nuclear magnetic resonance (NMR) parameter measurements of Japanese pear fruit (Pyrus pyrifolia Nakai, Kosui) were performed using an electrically mobile magnetic resonance imaging (MRI) system with a 0.2 T and 16 cm gap permanent magnet. To measure the relaxation times and apparent diffusion coefficients of the pear fruit in relation to their weight, seven pear fruits were harvested almost every week during the cell enlargement period and measured in a research orchard. To evaluate the in situ relaxation times, six pear fruits were longitudinally measured for about two months during the same period. The measurements for the harvested samples showed good agreement with the in situ measurements. From the measurements of the harvested samples, it is clear that the relaxation rates of the pear fruits linearly change with the inverse of the linear dimension of the fruits, demonstrating that the relaxation mechanism is a surface relaxation. We therefore conclude that the mobile MRI system is a useful device for measuring the NMR parameters of outdoor living plants., (Copyright © 2012 Elsevier Inc. All rights reserved.)

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 C∕C++ 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.

We assessed lymph drainage in living mice by an integrated imaging method using fluorescence imaging (FLI) and magnetic resonance imaging (MRI). Mice were subcutaneously injected with quantum dots and gadofluorine 8 into the right rear footpad. They were fixed on a transparent flat plate and underwent FLI and MRI successively. Small markers were attached to the mouse surface for spatial coregistration, and image fusion of FLIs and MRIs was performed. Two-dimensional fluorescence reflectance imaging was used for FLI. FLI and MRI provided generally consistent results and demonstrated lymphatic flow to the popliteal, sacral, and iliac lymph nodes in most mice and to the renal, inguinal, and lumbar-aortic lymph nodes in some mice. On the fusion images, the locations of the lymph nodes in the mouse trunk were in good agreement between FLI and MRI, indicating successful spatial registration even for the deep structures. The popliteal node tended to be visualized a little farther caudally in FLI than in MRI, presumably because the overlying tissues were thicker in the cranial portion. Integrated FLI/MRI lymphography with image fusion appears to be a useful tool for analysis of the murine lymphatic system.

Infestation of harvested apple fruits by the peach fruit moth (Carposina sasakii Matsumura) was studied using a dedicated magnetic resonance imaging (MRI) apparatus equipped with a 0.2-T permanent magnet. Infested holes on the three-dimensional (3-D) images tracked ecological movements of peach fruit moth larvae within the food fruits, and thus in their natural habitat. Sensitive short solenoid coil and surface coil detectors were devised to shorten measurement times. The short solenoid coil detected infestation holes at a rate of 6.4 s per image by the single-slice 2-D measurement. The multi-slice 2-D measurement provided six slice images of a fruit within 2 min taken by the two detectors. These results indicate that the 0.2-T MRI apparatus allows one to distinguish sound fruits from infested ones, and also as a means for plant protection and the preservation of natural ecological systems in foreign trade.

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.

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.

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 µm](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.

We developed an integrated imaging method using bioluminescence imaging (BLI) and magnetic resonance imaging (MRI) and applied it to mouse tumor monitoring. BLIs and MRIs were successively acquired from mice fixed on a transparent flat plate and were registered using three small markers. After spatial coregistration, the two-dimensional BLI was fused with all MRI slices. The accuracy of image registration was evaluated using fluorescence imaging and MRI of many markers attached to the mice. Mice were inoculated with luciferase-expressing tumor cells subcutaneously or directly into the liver, and disease progression was evaluated repeatedly by integrated BLI-MRI. Image registration was achieved with acceptable accuracy, although the registration error increased with increasing distance from the center of the imaging field and was larger in imaging the convex dorsal side of the mouse than in imaging the flat ventral side. Integrated BLI-MRI allowed longitudinal assessment of disease progression and appeared to facilitate detailed interpretation of the imaging findings. It aided the anatomic localization of lesions demonstrated by BLI and recognition of MRI abnormalities corresponding to BLI foci. Integrated BLI-MRI is feasible and appears to be a practical method for comprehensive, longitudinal assessment of disease model mice.

Infestation of young apple fruits by the larvae of the peach fruit moth, Carposina sasakii Matsumura (Lepidoptera: Carposinidae), was studied by a small dedicated micro-magnetic resonance imaging (MRI) apparatus using the three-dimensional (3D) gradient-echo method and the two-dimensional (2D) and 3D spin-echo methods. Changes from a young larva at 1.8 mm in length to a mature one ready to leave the fruit were observed in relation to the progression of infestation of the fruit tissues. The trace of larva intrusion was demonstrated by a series of sliced images in the 3D image data of an infested fruit, where it entered from outside the calyx, and migrated to near the vasculature around the carpel through the core. The small, dedicated MRI device was proven useful for ecological studies of the growth and movement of insect larvae in their food fruits. It can also be applied to detect the infestation of small fruits by insect larvae.

A compact magnetic resonance imaging (MRI) system for a cold (-5 degrees C) room has been developed to acquire MR images below the freezing point of water. The MRI system consists of a 1.0 T permanent magnet, a higher-order shim coil set, and a gradient coil probe, installed in the cold room, and a compact MRI console installed in a room at normal temperature (20-25 degrees C). The most difficult problem for the installation of the MRI system in the cold room was the degradation of the field homogeneity of the permanent magnet shimmed at 25 degrees C. To overcome this problem, higher-order shim coils were developed and the temperature variation of the magnetic field distribution was measured using a standard phantom with and without shim coil currents. As a result, it was confirmed that the homogeneity (the difference between the minimum and maximum values) of the magnetic field in the 17x17x19 mm(3) rectangular parallelepiped region was improved from 117 to 59 ppm using an appropriate combination of shim coil currents. A snowpack immersed in dodecane (C(12)H(26)) was imaged using a driven-equilibrium three-dimensional (3D) spin-echo sequence at -5 degrees C. The visualized 3D structure of the snowpack demonstrated the effectiveness of our approach.

We repeatedly measured the trabecular bone (TB) microstructure of the distal radius in 5 healthy volunteers using a compact magnetic resonance (MR) imaging system to evaluate the reproducibility of the TB structural parameters. The compact system was specially developed with a 1.0-tesla permanent magnet for the distal radius in a previous study. We measured the distal radius using a 3-dimensional (3D), driven-equilibrium, spin-echo sequence (repetition time/echo time=80 ms/10 ms, number of excitations=1, field of view=76.8 mm x 57.6 mm x 16.0 mm, acquisition time=17 min, matrix size=512 x 384 x 32, voxel size=150 microm x 150 microm x 500 microm) and analyzed the acquired image datasets using the virtual bone biopsy system developed by the University of Pennsylvania. Root mean squares of the coefficients of variance expressed as percentages ranged from 2.9% to 14% for the TB structural parameters. Therefore, we concluded that this compact MR imaging system could be used to assess TB microstructure of the distal radius and provide results consistent with those using a whole-body MR imaging system and showing the promise of this system for evaluating bone quality in clinical settings.

A local radio frequency (rf) shielding consisting of a Cu plate and an LC balun circuit has been developed for a compact magnetic resonance imaging (MRI) system with a 0.3 T permanent magnet. Performance of the local rf shielding was evaluated using an artificial external noise source irradiating a human subject whose hand was inserted into the rf coil of the MRI system. Power spectra of the rf signal detected through the rf coil demonstrated that the local rf shield achieved 30.1 dB external noise suppression. With the local rf shielding, a MRI of the subject's hand was performed using a three-dimensional gradient-echo sequence. Anatomical structures of the subject's hand were clearly visualized. It was concluded that the local rf shielding could be used for the compact MRI system instead of a rf shielded room.

It is essential to visualize the structures of embryos and their internal organs three-dimensionally to analyze morphogenesis; this used to rely solely on serial histological sectioning and solid reconstruction, which were tedious and time-consuming. We have applied imaging with a magnetic resonance (MR) microscope equipped with a 2.35 T superconducting magnet to visualize human embryos; we were successful in acquiring high-resolution sectional images and in identifying the detailed structures of major organs. The imaging process was facilitated by using a super-parallel MR microscope. A dataset of MR images of more than 1,000 human embryos, now collected, will be important for future biomedical research and for education., ((c) 2007 Wiley-Liss, Inc.)

A compact MRI system for trabecular bone (TB) microstructure measurements of the distal radius was developed using a 1.0 T permanent magnet and a compact MRI console. TB microstructure of the distal radius was clearly visualized using a three-dimensional (3D) driven equilibrium spin-echo (DESE) sequence in 23 min. The image obtained had a sufficient spatial resolution (150 microm x 150 microm x 500 microm) and signal-to-noise ratio (SNR) (approximately 10) for 3D bone microstructure analysis. The system demonstrated the feasibility of using a permanent magnet compact MRI system as a clinical instrument for bone microstructure measurements of the distal radius.

We have developed a compact magnetic resonance (MR) imaging scanner with permanent magnet, gradient coil set, and radiofrequency (RF) coils optimized for whole-hand examination for the diagnosis of rheumatoid arthritis (RA). The system weighs about 600 kg, and installation space is 2 m(2), excluding the shield room. Hand examinations of normal volunteers and patients with RA were performed using a 3D T(1)-weighted gradient-echo (GRE) sequence and short T(I) inversion recovery 3D fast spin-echo (STIR-3DFSE) sequence, and anatomical structures and various lesions of the hand caused by RA were clearly visualized in a 16-min examination. It was concluded that the system could be used for diagnosis of RA in even a small clinic.

Using 4 and 8-channel super-parallel magnetic resonance (MR) microscopes with a horizontal bore 2.34T superconducting magnet developed for 3-dimensional MR microscopy of the large Kyoto Collection of Human Embryos, we acquired T(1)-weighted 3D images of 1204 embryos at a spatial resolution of (40 microm)(3) to (150 microm)(3) in about 2 years. Similarity of image contrast between the T(1)-weighted images and stained anatomical sections indicated that T(1)-weighted 3D images could be used for an anatomical 3D image database for human embryology.

The thawing process for boiled and frozen edible vegetables was traced by a dedicated MRI for food research. The MRI system is small, with a 1.0-T static magnetic field, and can be placed in an ordinary research room with a light air conditioner. Images of green soybeans, broad beans, okra, asparagus and taro were measured by the spin-echo method (echo time=7 ms) with 0.1 or 0.2 s and 1 s repetition times. The images appeared along with the thawing time, and signals uniformly covered the sliced plane of the samples in the thawed condition. Information about the thawing process and tissue structures of the materials was obtained during transit thawing conditions. The thawing kinetics were examined with increased signal intensity, which were divided into two types. The signal increased linearly and saturated for okra and asparagus but exhibited convex curves for soybeans, broad beans and taro. The small MRI was stable, its handling was simple, and the internal structures of food materials could be accurately identified, although the grey-scale of the images was insufficient for determining precise textural fluctuations of tissue organization. We conclude that the devised MRI is useful for examining the quality of frozen foods and for developmental research into frozen foods.

Purpose: To determine the feasibility of imaging living mice with a 1-T compact MRI system and investigate appropriate imaging techniques for use in routine animal experiments., Materials and Methods: An MRI system consisting of a 1-T permanent magnet and compact console was used. Images of the entire trunks of living mice were obtained on the system using a T1-weighted three-dimensional fast low-angle shot (3D FLASH) sequence, and image quality was evaluated in relation to imaging techniques., Results: Restraint of respiratory motion improved the image quality. Decreasing the slice thickness reduced artificial inhomogeneity in signal intensity (SI). Substantial effects of TR and FA on image quality were also demonstrated. With the determined techniques, images covering the entire trunk with a voxel size of 0.26x0.26x0.52 mm were acquired in an acquisition time of five minutes 28 seconds and a total experiment time of <20 minutes, and various organs and subcutaneous tumors were clearly visualized., Conclusion: The compact MRI system provides images of living mice with acceptable quality in a reasonable time. Considering its convenience, it appears to be suitable for use in routine mouse experiments., (Copyright (c) 2006 Wiley-Liss, Inc.)

A system combining electron spin resonance imaging (ESRI) with another imaging modality capable of enabling visualization of the distribution of bioradicals on an anatomical map of the specimens would be a superior biomedical imaging system. We describe the development of an ESR/MR dual-imaging system with one permanent magnet and the biomedical applications of this system. The magnetic circuit developed for the ESR/MR dual-imaging system consisted of the permanent magnet made of Fe-Nd-B, pole pieces, and poke. The permanent magnet was installed on the MR side only, and the ESR side was made of pole pieces only. The magnetic field was adjusted to 0.5T at MR and to 0.042T at ESR. The overall dimensions of the magnet developed for the ESR/MR imaging system were 460 (W)x440 (D)x460 (H) mm, and it weighed 220 kg. The distance of each center for the magnet for ESR and MR imaging could be set as close as 200 mm. The entire ESR/MR imaging system can be installed in a common laboratory without magnetic shielding. MR images of plants (myoga) and small animals (mice and rats) were successfully acquired with or without ESR operation. ESR spectra of nitroxyl spin probes were also measured, even with MRI operation. ESR signals of triarylmethyl derivatives with narrow line-width (0.026 mT) were observed in living mice while MRI was operating. The ESR/MR imaging dual functions work properly with no electric or magnetic interference. The ESR/MR dual images demonstrate that this system enables visualization of the distribution of bioradicals on the anatomical map of the object.

Purpose: To investigate the feasibility of an originally developed compact MRI system for evaluating rheumatoid arthritis (RA), and determine its advantages and disadvantages as an imaging modality for evaluating RA., Materials and Methods: We prospectively studied 13 healthy controls with no clinical symptoms of arthritis, and 13 patients with hand and wrist pains (including pain from RA) with a 0.2 T permanent-magnet compact MR imager. All MR images were obtained while the subjects were in a sitting position. Coronal three-dimensional spin-echo T1-weighted images and coronal two-dimensional short tau inversion recovery (STIR) images were obtained with image matrix = 256 x 128 and field of view (FOV) = 20.48 cm. Plain radiograph findings and MRI findings of patients were compared., Results: In three of the patients with suspected early RA (N = 7), early RA was evaluated based on STIR images. All RA patients showed morphologic or signal intensity changes that allowed an evaluation of RA from MR findings. Four of five RA patients showed high signal intensity on STIR images in the wrist, proximal interphalangeal (PIP) joint, or metacarpophalangeal (MCP) joint that suggested synovitis. Multiple erosions in the hand and wrist were seen in four RA patients, with low signal intensity on T1-weighted images., Conclusion: RA was correctly evaluated, and early RA could be identified with the compact MRI system. However, the current system has limitations, such as the nonselective STIR sequence used and magnetic field inhomogeneity., ((c) 2006 Wiley-Liss, Inc.)

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., (Copyright 2005 Wiley-Liss, Inc.)

Trabecular bone volume fraction (TBVF) and speed of sound (SOS) were measured for the right calcanei of 416 female volunteers. The TBVF was measured with a compact MRI developed in our laboratory. The SOS was measured with a commercial quantitative ultrasound system. It was observed that the correlation coefficient between TBVF and SOS and that between TBVF and age varied depending on the location of region of interest (ROI) in the calcaneus. As a result, an optimum circular ROI with a diameter of 20 mm was determined so that the correlation coefficients were maximized. In the optimum ROI, transverse relaxation time (T2) of the bone marrow protons of the calcaneus was found to be concentrated in a narrow range over the subjects. This result suggested that a 50% scan time reduction in the TBVF measurements could be made by skipping the T2 correction procedure.

An MR imaging system was developed to visualize brine drainage channels in sea spray icing. Brine pockets trapped in spray-ice matrices during ice growth are structural features of sea spray icing. Brine in the spray ice sample had drained out; therefore, using a suction pump, we filled the air gaps in the drainage channels with dodecane. In the experiments, 0.5-1.0 h was necessary to accumulate signals sufficient to obtain a 3-D micro-image; the image matrix comprised 128(3) voxels (each voxel was 200 microm per side). The MIP view showed that sea spray icing has a developed drainage-channel network structure.

A compact mouse MRI has been developed using a 1.0T yokeless permanent magnet and portable MRI console. The entire system was installed in a space measuring 2 m x 1 m. The imaging region was the cylindrical volume (35 mm diameter, 50 mm length) at the center of the magnet and was used for whole-brain or body imaging of mice. Whole-brain imaging took less than 90 min for T1- and T2-weighted 3D images with 2-mm slice thickness and 200-microm in-plane resolution. Body imaging took less than 30 min for T1-weighted spin-echo and FLASH 3D images with 0.5- to 1.0-mm slice thickness and 250- to 300-microm in-plane resolution. In addition to the compactness of the system, the mouse MRI has several advantages over high-field superconducting animal MRI systems in its accessibility to the specimen, similarity to clinical MRI in image contrast, capacity for biological isolation, and maintenance. The results obtained demonstrate the potential of this new system for routine imaging in biomedical laboratories.

A compact MRI system for measuring trabecular bone volume fraction (TBVF) of the calcaneus was developed with the use of a 0.21 T permanent magnet and portable MRI console. The entire system weighed < 600 kg and was installed in a 2 m x 2 m space. Two cross-sectional spin-echo images of a heel acquired with external reference phantoms (total measurement time = 5 min) were used to quantify the TBVF of the calcaneus. The linearity and reproducibility of the measurements were evaluated by means of proton density-adjusted phantoms. Comparative measurements with quantitative ultrasound (QUS) in groups of healthy female volunteers showed a relatively high positive correlation (R(2) = 0.4539, 0.2693) between TBVF and the speed of sound (SOS). These results demonstrate the potential of this new system for measuring bone density. Magn Reson Med 52:440-444, 2004., (Copyright 2004 Wiley-Liss, Inc.)

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 micro m(3) 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 micro m(3) 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., (Copyright 2003 Wiley-Liss, Inc.)

The present study was designed to evaluate the use of a 1.0T portable permanent magnet MR system in obtaining microscopic MR images of the hyaline cartilage in vitro. A clear laminar appearance was demonstrated with this system. In addition, it was possible to demonstrate cartilage surface irregularity, a decrease in cartilage thickness, and T2 alteration by proteoglycan depletion following up to 12 hours of trypsin treatment. In summary, the portable MR system is useful for investigating cartilage in vitro.

MR microscopy technique was introduced to visualize and quantify the three-dimensional structure of snowpack. Since the NMR signal from the ice was week, we looked at the air space instead filling with dodecane or aniline doped with iron acetylacetonate. Four types of snow were tested: ice spheres, large rounded poly crystals, small rounded mono-crystals and depth hoar crystals. A specific specimen-cooling system was developed to keep the temperature below 0 degrees C. In the experiments 0.5 to 2 h were necessary to accumulate the signals enough to obtain a 3D micro-image; the image matrix 128(3), voxel size (200 microm)3 or 256(3) (120 microm)3. Comparison with the 2D data using the conventional section plane method was also carried out and MR microscopy is proved to be a very useful method to visualize the microstructure of snowpack.

Objective: To evaluate MR microscopic images of normal-appearing porcine hyaline cartilage ( n=15) in vitro obtained with an MR microscope using an independent console system (MRMICS) at 1.5 T., Design and Results: The MRMICS is a portable imaging system consisting of a radiofrequency system, gradient power supplies and a personal computer. The images from the MRMICS showed a laminar structure of porcine cartilage similar to the structure demonstrated with other MR imaging techniques. The laminar structures of the articular cartilage, were, however heterogeneous in respect of signal intensity and thickness, which varied according to the site resected. The MR laminar appearance was most comparable to the staining with Masson's trichrome for collagen., Conclusion: MRMICS is a useful add-on system for obtaining microscopic MR images of articular cartilage in vitro.

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.

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.

We studied microscopic MR images of the normal appendix in vitro using a new MR microscope system: MR Microscope using an Independent Console System (MRMICS). The MRMICS was placed in the clinical MR room, and the probe box was fixed on the bed of the 1.5 T clinical MR machine. T1-, T2-, and proton density-weighted images were obtained using spin echo sequences with an in-plane pixel size of 100 x 100 microns. Zonal structures of the appendix were clearly demonstrated with different contrast by different sequences. Therefore, the MRMICS is a useful add-on system for investigating microscopic MR images of biological tissues in vitro.