National Institutes for Environmental Studies

Tsukuba, Japan

National Institutes for Environmental Studies

Tsukuba, Japan
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Watanabe H.,National Institutes for Environmental Studies | Takaya N.,National Institutes for Environmental Studies | Mitsumori F.,National Institutes for Environmental Studies
Magnetic Resonance in Medical Sciences | Year: 2013

Purpose: We propose a post-processing framework for localized two-dimensional (2D) magnetic resonance spectroscopy (MRS) in vivo. Methods: Our framework consists of corrections on eddy current and subject motion along with the framework used in conventional analytical 2D nuclear magnetic resonance (NMR) spectroscopy. In the eddy current correction, the phases of the free induction decays (FIDs) of the metabolite 1H are corrected along the t2 direction by the phase of the FID of water 1H. The corrected FIDs are Fourier transformed along the t2 direction, and interferograms of F(t1, ω2) are calculated. In the motion correction, the zero-order phase of the N-acetyl aspartate (NAA) singlet peak for each t1 axis is corrected after correction of frequency drift. We applied this framework in phantom and human brain measurements in a 4.7T wholebody MR system. Two-dimensional data were collected by the localized 2D constant-time correlation spectroscopy (CT-COSY) sequence. We used a phantom containing a brain metabolite mixture of NAA, creatine (Cr), glutamate (Glu), glutamine (Gln) and γ-amino butyric acid (GABA).We demonstrated the eddy current correction procedure in the phantom experiments and the subject motion correction in human measurements. Results: Though asymmetric patterns of the singlets of NAA and Cr were shown around the peak along the F2 direction in the reconstructed phantom spectra without eddy current correction, symmetric patterns arose after the correction. The t1 noise caused by those singlets was found in the human brain spectra without motion correction. The t1 noise was sufficiently suppressed by the motion correction. Conclusion: Our proposed post-processing framework for localized 2D MRS can improve the quality of in vivo 2D spectra and may allow improved quantitation and robustness of in vivo 2D spectroscopy. © 2013 Japanese Society for Magnetic Resonance in Medicine.


Das L.,Japan Agency for Marine - Earth Science and Technology | Annan J.D.,Japan Agency for Marine - Earth Science and Technology | Hargreaves J.C.,Japan Agency for Marine - Earth Science and Technology | Emori S.,National Institutes for Environmental Studies
Climate Research | Year: 2012

In the present study we investigate the performance of climate models which contributed to the past 3 Intergovernmental Panel for Climate Change (IPCC) assessment reports for the Gangetic West Bengal region of east India (6° × 6°). Analysing present-day seasonal rainfall and temperature over the domain, we compare the results of the models (from the 6 modelling centres common to the second, third and fourth assessment reports-SAR, TAR and AR4, respectively) in order to judge to what extent these global models have improved on a regional scale. Metrics for model evaluation are not yet firmly established in the literature, so in this paper we compare and contrast the results from a number of different statistics used in previous studies. We also analyse the impact of topography on the results obtained for the AR4 models. We find that most models improved from SAR to AR4, although there is some variation in this result depending on seasons, variables and on which statistical methods are used in the analysis. The multi-model mean of the 6 models improves from SAR to TAR to AR4. The overall best performance in this region in the AR4 is the Japanese model, MIROC, but the best model in terms of improving skill from SAR to AR4 is the GFDL model from the United States. Correcting for errors in the model topographies produced an overall improvement of spatial patterns and error statistics, and greatly improves the performance of 1 model (CGCM) which has poor topography, but does not affect the ranking of the other models. © Inter-Research 2012.


Watanabe H.,National Institutes for Environmental Studies | Takaya N.,National Institutes for Environmental Studies | Mitsumori F.,National Institutes for Environmental Studies
Magnetic Resonance in Medical Sciences | Year: 2014

Purpose: We propose an absolute quantitation method for metabolites with strongly coupled spin systems using localized 2-dimensional (2D) constant-time correlation spectroscopy (CT-COSY). We also develop two methods for improving the quality of in vivo CT-COSY spectra. Methods: We substituted an image selected in vivo spectroscopy (ISIS) pulse for a 180° slice pulse in the CT-COSY module to decrease the slice displacement error caused by the chemical shift difference. We measured the slice displacement error due to the differences in the carrier frequency of slice pulse in a phantom experiment to demonstrate this feature. We also developed an asymmetric sampling scheme along the t1 direction to resolve diagonal peaks even in the magnitude mode of 2D spectra. We collected CT-COSY signals of a human brain for a 14% asymmetric sampling scheme. After reconstruction, we obtained a 2D CTCOSY spectrum in magnitude mode and compared a peak of glutamate (Glu) C4H on that spectrum to a peak displayed in absorption mode. In our proposed absolute quantitation method, we developed T2 correction, curve-fitting for computing peak volume and calibration by an internal water reference. We used the method to measure the Glu concentration in 10- mM glutamate phantom experiments. We also attempted to measure concentrations of Glu, γ- aminobutyric acid (GABA) and glutamine (Gln) in a human brain. Results: Slice displacement error was decreased by a factor of 2.5 using the proposed sequence. Spectra with narrow linewidths could be obtained using the asymmetric sampling scheme in the magnitude mode. Measured Glu concentration in the solution phantom was 9.4mM. Concentrations of Glu (9.5mM), GABA (0.61 mM) and Gln (3.6mM) in a human brain measured by our method agreed well with previously reported values. Conclusion: Concentrations of metabolites with strongly coupled spin systems can be measured using our proposed absolute quantitation method on 2D CT-COSY spectra. © 2014 Japanese Society for Magnetic Resonance in Medicine.


Das L.,Japan Agency for Marine - Earth Science and Technology | Annan J.D.,Japan Agency for Marine - Earth Science and Technology | Hargreaves J.C.,Japan Agency for Marine - Earth Science and Technology | Emori S.,National Institutes for Environmental Studies
Atmospheric Science Letters | Year: 2011

In this study, we used two novel methods to estimate urban contamination in the Japanese temperature record of the last century. First, we tested different criteria for choosing the rural stations, and found little sensitivity to the method, though the presence of a decreasing local population trend appeared to be a useful indicator. Second, we investigated the relationship between the regional sea surface temperature (SST) and surface air temperature over land, and found a very strong relationship across the coupled model intercomparison project phase 3 multi-model ensemble. Applying this relationship to observational SST data indicates little or no contamination of the trends from the stations identified as rural. © 2011 Royal Meteorological Society.


Watanabe H.,National Institutes for Environmental Studies | Takaya N.,National Institutes for Environmental Studies | Mitsumori F.,National Institutes for Environmental Studies
Journal of Magnetic Resonance | Year: 2011

A new method of non-uniform image correction is proposed. Image non-uniformity is originated from the spatial distribution of RF transmission and reception fields, represented as B1+ and B1-, respectively. In our method, B1+ mapping was performed in vivo by a phase method. In B1- mapping, images with multiple TEs were acquired with a multi-echo adiabatic spin echo (MASE) sequence which enables homogeneous excitation. By T 2 fitting of these images an M 0 map (M0MASE) was obtained, in which signal intensity was expressed as the product of B1- and M0(1-e -TR/T1). The ratio of this M0MASE map to the B1+ map showed a similar spatial pattern in different human brains. These ratios of M0MASE to B1+ in 24 subjects were averaged and then fitted with a spatially polynomial function to obtain a ratio map of B1-/B1+(α). Uniform image was achieved in spin echo (SE), MASE and inversion recovery turboFLASH (IRTF) images using measured B1+ and calculated B1- by αB1+. Water fractions in gray and white matters obtained from the M 0 images corrected by this method were in good agreement with previously reported values. From these experimental results, the proposed method of non-uniformity correction is validated at 4.7 T imaging. © 2011 Elsevier Inc. All rights reserved.


Okamoto H.,Kyushu University | Sato K.,Kyushu University | Hagihara Y.,Kyushu University | Nishizawa T.,National Institutes for Environmental Studies
AIP Conference Proceedings | Year: 2013

We develop algorithms that can be applied to EarthCARE Cloud Profiling Radar (CPR) and Atmospheric backscatter LIdar (ATLID) and discuss about the expected products. EarthCARE will carry CPR and ATLID and these combination corresponds to the CloudSat and CALIPSO for the A-train. Due to the similarities between the EarthCARE and the A-train, it will be possible to apply the similar types of algorithms that have been already developed and extensively used for the analyses of the A-train satellites and it is therefore expected to obtain the similar cloud products for the EarthCARE. On the other hand, there are some differences between the EarthCARE and A-train satellites, e.g., the EarthCRAE CPR has better sensitivity compared with the CloudSat. And Doppler capability of the EarthCARE-CPR is a new element and is expected to provide the better constraint for the retrievals of cloud/precipitation microphysics. And the vertical air motion and sedimentation velocity of cloud particles will be inferred. © 2013 AIP Publishing LLC.


Watanabe H.,National Institutes for Environmental Studies | Takaya N.,National Institutes for Environmental Studies | Mitsumori F.,National Institutes for Environmental Studies
Magnetic Resonance in Medical Sciences | Year: 2012

In constant time (CT) point-resolved spectroscopy (PRESS), echo centers shift with the fast decay of short T2* on two-dimensional (2D) time domain (TD) data under inhomogeneous B0 field like in vivo conditions. Though 1H decoupling along the F1 direction is a feature of this method, the tilted and broadened peak pattern on the F1-F2 plane after reconstruction causes the peaks to overlap. To enhance resolution to achieve highly resolved 2D CT-PRESS spectra in the human brain, we propose a 2-part window function that comprises an enhancement part for shifting echoes with fast decay and a conventional part, such as Lorentzian, Gaussian, or sinebell function. We obtained 2D spectra from human brains at 4.7T. The 3 diagonal peaks of C4H of glutamate (Glu C4H) at 2.35 ppm, C2H of γ-amino butyric acid (GABA C2H) at 2.28 ppm, and C4H of glutamine (Gln C4H) at 2.44 ppm-overlapped on the spectra processed with the conventional window but clearly resolved on the spectra using the proposed enhancement window. The signal-to-noise ratio per unit measurement time of Glu C4H on a CT-PRESS spectrum of the human brain was 1.7 times higher than that on a spectrum obtained by CT-correlation spectroscopic (COSY). In conclusion, 2D CT-PRESS spectra processed with the proposed window function to enhance resolution can resolve peaks of coupled 1H spins with higher accuracy and sensitivity.


Watanabe H.,National Institutes for Environmental Studies
Magnetic Resonance in Medical Sciences | Year: 2012

When radiofrequency (RF) transmission field represents B1 +, the reception field represents B1 -*. The distribution of those maps demonstrates asymmetric features at high field magnetic resonance (MR) imaging. Both maps are in mirror symmetry to one another. Almost symmetric distribution of the B1 field was expected on the laboratory frame in a symmetric sample loaded inside the RF coil designed to achieve a homogeneous B1 field. Then, a simple change was made in the coordinate transformation equation of RF fields between the rotating and laboratory frames in both linear and quadrature modes to investigate the source of this feature of asymmetry. The magnitude of rotating frame components, B1 + and B1 -, consists of the magnitude and the phase difference of the laboratory frame components. The rotating frame components differ in the sign of the sinusoidal phase difference. B1 + is equal to B1 - at lower field because phase changes that depend on position can be ignored. At higher fields, the magnitude component has a symmetric profile, and distribution in the phase component is antisymmetric. Thus, the distributions of B1 + and B1 - maps demonstrate mirror symmetry. Maps of magnitude and phase components were examined in the laboratory frame. Their maps were computed from B1 + and B1 - maps of the human brain and of a spherical saline phantom measured at 4.7T. It was concluded from these analytical and experimental results that the asymmetric and mirror symmetric distributions in B1 + and B1 - are derived from the phase difference in the laboratory frame.


Watanabe H.,National Institutes for Environmental Studies
Magnetic Resonance in Medical Sciences | Year: 2012

We demonstrated that the radiofrequency (RF) reception field is proportional to B1 -*straightforwardly in magnetic resonance (MR) imaging experiments at 4.7T. We compared maps of the reception field and the B1 - of a saline phantom in magnitude and phase. First, we measured the image using an adiabatic spin echo (ASE) sequence with homogeneous excitation. That image corresponds to a map of the reception field. Next, we rotated the RF coil with the sample 180° around the vertical axis to measure the map of the transmission field that corresponded to B1 - in the original configuration. The magnitude of the distribution fields of the reception field and B1 - maps was almost identical. Examining the phases of the ASE images in the original and inverted configurations, we observed almost the same distribution in both phase maps, which indicated the proportionality of the reception field to B1 -*.


PubMed | National Institutes for Environmental Studies
Type: Journal Article | Journal: Magnetic resonance in medical sciences : MRMS : an official journal of Japan Society of Magnetic Resonance in Medicine | Year: 2014

We propose an absolute quantitation method for metabolites with strongly coupled spin systems using localized 2-dimensional (2D) constant-time correlation spectroscopy (CT-COSY). We also develop two methods for improving the quality of in vivo CT-COSY spectra.We substituted an image selected in vivo spectroscopy (ISIS) pulse for a 180 slice pulse in the CT-COSY module to decrease the slice displacement error caused by the chemical shift difference. We measured the slice displacement error due to the differences in the carrier frequency of slice pulse in a phantom experiment to demonstrate this feature. We also developed an asymmetric sampling scheme along the t1 direction to resolve diagonal peaks even in the magnitude mode of 2D spectra. We collected CT-COSY signals of a human brain for a 14% asymmetric sampling scheme. After reconstruction, we obtained a 2D CT-COSY spectrum in magnitude mode and compared a peak of glutamate (Glu) C4H on that spectrum to a peak displayed in absorption mode. In our proposed absolute quantitation method, we developed T2 correction, curve-fitting for computing peak volume and calibration by an internal water reference. We used the method to measure the Glu concentration in 10-mM glutamate phantom experiments. We also attempted to measure concentrations of Glu, -aminobutyric acid (GABA) and glutamine (Gln) in a human brain.Slice displacement error was decreased by a factor of 2.5 using the proposed sequence. Spectra with narrow linewidths could be obtained using the asymmetric sampling scheme in the magnitude mode. Measured Glu concentration in the solution phantom was 9.4 mM. Concentrations of Glu (9.5 mM), GABA (0.61 mM) and Gln (3.6 mM) in a human brain measured by our method agreed well with previously reported values.Concentrations of metabolites with strongly coupled spin systems can be measured using our proposed absolute quantitation method on 2D CT-COSY spectra.

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