The Experts below are selected from a list of 81 Experts worldwide ranked by ideXlab platform
Jun Shen - One of the best experts on this subject based on the ideXlab platform.
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selective homonuclear hartmann hahn transfer method for in vivo spectral editing in the human brain
Magnetic Resonance in Medicine, 2005Co-Authors: In-young Choi, Sang-pil Lee, Jun ShenAbstract:A novel selective homonuclear Hartmann–Hahn transfer method for in vivo spectral editing is proposed and applied to measurements of γ-aminobutyric acid (GABA) in the human brain at 3 T. The proposed method utilizes a new concept for in vivo spectral editing, the spectral selectivity of which is not based on a conventional editing pulse but based on the stringent requirement of the doubly selective Hartmann–Hahn match. The sensitivity and spectral selectivity of GABA detection achieved by this doubly selective Hartmann–Hahn match scheme was superior to that achievable by conventional in vivo spectral editing techniques providing both sensitivity enhancement and excellent suppression of overlapping resonances in a single shot. Since Double-Quantum Filtering gradients were not employed, singlets such as the NAA methyl group at 2.02 ppm and the creatine methylene group at 3.92 ppm were detected simultaneously. These singlets may serve as navigators for the spectral phase of GABA and for frequency shifts during measurements. The estimated concentration of GABA in the frontoparietal region of the human brain in vivo was 0.7 ± 0.2 μmol/g (mean ± SD, n = 12). Magn Reson Med 53:503–510, 2005. Published 2005 Wiley-Liss, Inc.
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Selective homonuclear Hartmann–Hahn transfer method for in vivo spectral editing in the human brain
Magnetic resonance in medicine, 2005Co-Authors: In-young Choi, Sang-pil Lee, Jun ShenAbstract:A novel selective homonuclear Hartmann–Hahn transfer method for in vivo spectral editing is proposed and applied to measurements of γ-aminobutyric acid (GABA) in the human brain at 3 T. The proposed method utilizes a new concept for in vivo spectral editing, the spectral selectivity of which is not based on a conventional editing pulse but based on the stringent requirement of the doubly selective Hartmann–Hahn match. The sensitivity and spectral selectivity of GABA detection achieved by this doubly selective Hartmann–Hahn match scheme was superior to that achievable by conventional in vivo spectral editing techniques providing both sensitivity enhancement and excellent suppression of overlapping resonances in a single shot. Since Double-Quantum Filtering gradients were not employed, singlets such as the NAA methyl group at 2.02 ppm and the creatine methylene group at 3.92 ppm were detected simultaneously. These singlets may serve as navigators for the spectral phase of GABA and for frequency shifts during measurements. The estimated concentration of GABA in the frontoparietal region of the human brain in vivo was 0.7 ± 0.2 μmol/g (mean ± SD, n = 12). Magn Reson Med 53:503–510, 2005. Published 2005 Wiley-Liss, Inc.
Hao Lei - One of the best experts on this subject based on the ideXlab platform.
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the effects of slice selective excitation refocusing in localized spectral editing with gradient selected double quantum coherence transfer
Journal of Magnetic Resonance, 2001Co-Authors: Hao Lei, Jeff F. DunnAbstract:Spectral editing using gradient-selected Double-Quantum Filtering (DQF) with PRESS localization has been used for selective observation of metabolites in vivo. In previous studies using localized DQF sequences, it is generally assumed that the slice-selective pulses used in the sequence have no roles in coherence transfer, and do not interfere with DQF. To validate this assumption, the effects of slice-selective excitation/refocusing on DQF were investigated in DQF lactate editing sequences combined with PRESS localization. Contrary to the previous assumption, the results show that, due to chemical shift displacement artifact and J coupling, slice selection in DQF does interfere with coherence transfer, affecting both the accuracy of spatial localization and the detection sensitivity adversely. In the case of lactate editing, the effects of this interference can be accounted for simply by adjusting the strength of the slice-selection gradients and by using narrowband slice-selective refocusing pulses.
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The Effects of Slice-Selective Excitation/Refocusing in Localized Spectral Editing with Gradient-Selected Double-Quantum Coherence Transfer
Journal of magnetic resonance (San Diego Calif. : 1997), 2001Co-Authors: Hao Lei, Jeff F. DunnAbstract:Spectral editing using gradient-selected Double-Quantum Filtering (DQF) with PRESS localization has been used for selective observation of metabolites in vivo. In previous studies using localized DQF sequences, it is generally assumed that the slice-selective pulses used in the sequence have no roles in coherence transfer, and do not interfere with DQF. To validate this assumption, the effects of slice-selective excitation/refocusing on DQF were investigated in DQF lactate editing sequences combined with PRESS localization. Contrary to the previous assumption, the results show that, due to chemical shift displacement artifact and J coupling, slice selection in DQF does interfere with coherence transfer, affecting both the accuracy of spatial localization and the detection sensitivity adversely. In the case of lactate editing, the effects of this interference can be accounted for simply by adjusting the strength of the slice-selection gradients and by using narrowband slice-selective refocusing pulses.
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A localized Double-Quantum filter for in vivo detection of taurine.
Magnetic resonance in medicine, 1999Co-Authors: Hao Lei, James PeelingAbstract:Noninvasive detection of taurine, an important amino acid involved in numerous physiological processes, by in vivo 1H magnetic resonance (MR) spectroscopy is complicated by severe overlap of the taurine resonances with those of a number of other metabolites. Unambiguous differentiation of the taurine resonances requires spectral editing. In this study, the development of a localized spectral editing technique based on Double-Quantum Filtering optimized for in vivo detection of taurine is described. The sequence recovers the taurine signal while substantially eliminating overlapping resonances and provides excellent three-dimensional spatial localization. The performance of the sequence is demonstrated both in phantoms and in rat brain in vivo. Magn Reson Med 42:454–460, 1999. © 1999 Wiley-Liss, Inc.
Jeff F. Dunn - One of the best experts on this subject based on the ideXlab platform.
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the effects of slice selective excitation refocusing in localized spectral editing with gradient selected double quantum coherence transfer
Journal of Magnetic Resonance, 2001Co-Authors: Hao Lei, Jeff F. DunnAbstract:Spectral editing using gradient-selected Double-Quantum Filtering (DQF) with PRESS localization has been used for selective observation of metabolites in vivo. In previous studies using localized DQF sequences, it is generally assumed that the slice-selective pulses used in the sequence have no roles in coherence transfer, and do not interfere with DQF. To validate this assumption, the effects of slice-selective excitation/refocusing on DQF were investigated in DQF lactate editing sequences combined with PRESS localization. Contrary to the previous assumption, the results show that, due to chemical shift displacement artifact and J coupling, slice selection in DQF does interfere with coherence transfer, affecting both the accuracy of spatial localization and the detection sensitivity adversely. In the case of lactate editing, the effects of this interference can be accounted for simply by adjusting the strength of the slice-selection gradients and by using narrowband slice-selective refocusing pulses.
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The Effects of Slice-Selective Excitation/Refocusing in Localized Spectral Editing with Gradient-Selected Double-Quantum Coherence Transfer
Journal of magnetic resonance (San Diego Calif. : 1997), 2001Co-Authors: Hao Lei, Jeff F. DunnAbstract:Spectral editing using gradient-selected Double-Quantum Filtering (DQF) with PRESS localization has been used for selective observation of metabolites in vivo. In previous studies using localized DQF sequences, it is generally assumed that the slice-selective pulses used in the sequence have no roles in coherence transfer, and do not interfere with DQF. To validate this assumption, the effects of slice-selective excitation/refocusing on DQF were investigated in DQF lactate editing sequences combined with PRESS localization. Contrary to the previous assumption, the results show that, due to chemical shift displacement artifact and J coupling, slice selection in DQF does interfere with coherence transfer, affecting both the accuracy of spatial localization and the detection sensitivity adversely. In the case of lactate editing, the effects of this interference can be accounted for simply by adjusting the strength of the slice-selection gradients and by using narrowband slice-selective refocusing pulses.
In-young Choi - One of the best experts on this subject based on the ideXlab platform.
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selective homonuclear hartmann hahn transfer method for in vivo spectral editing in the human brain
Magnetic Resonance in Medicine, 2005Co-Authors: In-young Choi, Sang-pil Lee, Jun ShenAbstract:A novel selective homonuclear Hartmann–Hahn transfer method for in vivo spectral editing is proposed and applied to measurements of γ-aminobutyric acid (GABA) in the human brain at 3 T. The proposed method utilizes a new concept for in vivo spectral editing, the spectral selectivity of which is not based on a conventional editing pulse but based on the stringent requirement of the doubly selective Hartmann–Hahn match. The sensitivity and spectral selectivity of GABA detection achieved by this doubly selective Hartmann–Hahn match scheme was superior to that achievable by conventional in vivo spectral editing techniques providing both sensitivity enhancement and excellent suppression of overlapping resonances in a single shot. Since Double-Quantum Filtering gradients were not employed, singlets such as the NAA methyl group at 2.02 ppm and the creatine methylene group at 3.92 ppm were detected simultaneously. These singlets may serve as navigators for the spectral phase of GABA and for frequency shifts during measurements. The estimated concentration of GABA in the frontoparietal region of the human brain in vivo was 0.7 ± 0.2 μmol/g (mean ± SD, n = 12). Magn Reson Med 53:503–510, 2005. Published 2005 Wiley-Liss, Inc.
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Selective homonuclear Hartmann–Hahn transfer method for in vivo spectral editing in the human brain
Magnetic resonance in medicine, 2005Co-Authors: In-young Choi, Sang-pil Lee, Jun ShenAbstract:A novel selective homonuclear Hartmann–Hahn transfer method for in vivo spectral editing is proposed and applied to measurements of γ-aminobutyric acid (GABA) in the human brain at 3 T. The proposed method utilizes a new concept for in vivo spectral editing, the spectral selectivity of which is not based on a conventional editing pulse but based on the stringent requirement of the doubly selective Hartmann–Hahn match. The sensitivity and spectral selectivity of GABA detection achieved by this doubly selective Hartmann–Hahn match scheme was superior to that achievable by conventional in vivo spectral editing techniques providing both sensitivity enhancement and excellent suppression of overlapping resonances in a single shot. Since Double-Quantum Filtering gradients were not employed, singlets such as the NAA methyl group at 2.02 ppm and the creatine methylene group at 3.92 ppm were detected simultaneously. These singlets may serve as navigators for the spectral phase of GABA and for frequency shifts during measurements. The estimated concentration of GABA in the frontoparietal region of the human brain in vivo was 0.7 ± 0.2 μmol/g (mean ± SD, n = 12). Magn Reson Med 53:503–510, 2005. Published 2005 Wiley-Liss, Inc.
Hellmut Eckert - One of the best experts on this subject based on the ideXlab platform.
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Spectral editing in MAS NMR of aprotic solids 31P113Cd cross-polarization and heteronuclear Double-Quantum Filtering studies in II-IV-V2 semiconductor alloys
Solid state nuclear magnetic resonance, 1993Co-Authors: Deanna Franke, Christopher Hudalla, Hellmut EckertAbstract:Abstract Magic-angle-spinning NMR spectra of aprotic solids, ceramics and glasses frequently suffer from poor site resolution due to wide chemical shift distribution effects. In such cases, cross-polarization and heteronuclear Double-Quantum Filtering experiments involving nuclei other than 1H offer unique spectral editing capabilities. The utility of such assignment techniques for examining site populations in semiconductor alloys is demonstrated for the chalcopyrite systems CdGeAs2−xPx, CdSiAs2−xPx and ZnxCd1−xGeP2. The results permit a distinction between local and non-local effects on experimental chemical shift trends and reveal that compositional dependences observed in these alloys are dominated by non-local chemical shift contributions.
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atomic distribution in zinc cadmium germanium phosphide znxcd1 xgep2 semiconductor alloys phosphorus 31 and cadmium 113 magic angle spinning 31p spin echo and 31p 113cd heteronuclear double quantum Filtering mas nmr studies
The Journal of Physical Chemistry, 1992Co-Authors: Deanna Franke, Kesha Banks, Hellmut EckertAbstract:Cation substitution in the Zn x Cd 1-x GeP 2 (0≤x≤1) system results in homogeneous solid solutions which crystallize in the chalcopyrite structure. The distribution of local (nearest-neighbor) environments in these materials has been examined on the basis of complementary solid-state NMR experiments, including 31 P and 113 Cd magic-angle spinning (MAS), 31 P spin-echo, and 31 P- 113 Cd heteronuclear double quantum Filtering (HDQF) MAS-NMR