The Experts below are selected from a list of 171 Experts worldwide ranked by ideXlab platform
Toshiyuki Arai - One of the best experts on this subject based on the ideXlab platform.
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method for introducing Oxygen 17 into tissue for imaging in a magnetic resonance imaging system
Magnetic Resonance Imaging, 1992Co-Authors: Toshiyuki Arai, Pradeep M Gupte, Sigmund E LaskerAbstract:A diagnostic imaging agent is provided for use in conjunction with a magnetic resonance imaging system for the imaging of spacial Oxygen distribution in tissue. The imaging agent is comprised of a complex of Oxygen-17, a biologically acceptable liquid carrier, such as a perfluorinated compound, and an emulsifying agent, and wherein the agent has an average particle size of less than about 0.6 microns, and an ionic composition essentially equal to that of blood. Useful information can be obtained, and in certain instances, therapy administered, by a non-envasive imaging technique relative to tissue perfusion by 19 F-NMR (imaging of 19 F) and Oxygen utilization by 1 H-NMR (imaging of H2 17 O as a metabolite).
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cerebral Oxygen utilization analyzed by the use of Oxygen 17 and its nuclear magnetic resonance
Biochemical and Biophysical Research Communications, 1990Co-Authors: Toshiyuki Arai, Shinichi Nakao, Kenjiro Mori, Koichiro Ishimori, Isao Morishima, Tomoaki Miyazawa, Bernhard FritzzierothAbstract:In order to assess the usefulness of Oxygen-17, a stable isotope of Oxygen, Oxygen-17, was administered to rats for studying cerebral Oxygen utilization, and the produced metabolic water was detected by 17O-NMR spectroscopy in vitro and an 1H-NMR imaging system in vivo. In the vitro study, the increment in signal amplitude of Oxygen-17 was observed in the brain extracted from rats that inhaled Oxygen-17 gas. The in vivo study demonstrated that there were changes in the 1H-NMR image intensity of brain of rats that inhaled Oxygen-17 gas. These facts indicate that Oxygen-17 can serve as a tracer in the study of cerebral Oxygen utilization.
A Pines - One of the best experts on this subject based on the ideXlab platform.
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isotropic chemical shifts and quadrupolar parameters for Oxygen 17 using dynamic angle spinning nmr
The Journal of Physical Chemistry, 1992Co-Authors: Karl T Mueller, Jay H Baltisberger, E W Wooten, A PinesAbstract:Several Oxygen- 17-enriched silicates were studied using dynamic-angle spinning (DAS) NMR spectroscopy at two magnetic field strengths. The DAS method averages wnd-order quadrupolar interactions by reorienting a sample about a hedependent axis, thereby yielding high-resolution spectra for half-odd integer spin quadrupolar nuclei such as Oxygen-17. A narrow spectral line is observed for each distinct Oxygen site in a powdered sample at the sum of the isotropic chemical shift and the field-dependent isotropic second-order quadrupolar shift. Using equations for the total shift observed at two field strengths, the chemical shift is uniquely determined together with a product of the quadrupolar coupling constant (CQ = $qQ/h) and the quadrupolar asymmetry parameter (7). For one silicate, we demonstrate a computer program that uses the isotropic shifts and quadrupolar products as constraints and provides simulations of overlapped magic-angle spinning line shapes. In this way the quadrupolar parameters, CQ and q, are determined separately for each crystallographic site. The silicates studied include the discrete orthosilicates lamite (Ca2Si04) and forsterite (Mg2Si04), as well as diopside (CaMgSi206), wollastonite (CaSi03), and clinocnstatite ( MgSi03), which are minerals composed of chains of silicon-Oxygen tetrahedra.
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high resolution Oxygen 17 nmr of solid silicates
Journal of the American Chemical Society, 1991Co-Authors: Karl T Mueller, Yue Wu, Bradley F Chmelka, Jonathan F Stebbins, A PinesAbstract:Several{sup 17}O-enriched silicates were studied by use of dynamic angle spinning (DAS) and double rotation (DOR) nuclear magnetic resonance spectroscopy. These methods average away second-order quadrupolar interactions by reorienting a sample about a time-dependent axis, thereby yielding high-resolution spectra of Oxygen-17 nuclei. A narrow spectral line is observed for each distinct Oxygen site at the sum of the isotropic chemical shift and the field-dependent isotropic second-order quadrupolar shift. Resolution is increased by up to 2 orders of magnitude compared to conventional magic angle spinning (MAS) spectra. Crystallographically inequivalent Oxygen are now observable as distinct resonances in spectra of polycrystalline silicates such as diopside (CaMgSi{sub 2}{sup 17}O{sub 6}), wollastonite (CaSi{sup 17}O{sub 3}), larnite (Ca{sub 2}Si{sup 17}O{sub 4}), and forsterite (Mg{sub 2}Si{sup 17}O{sub 4}).
J J Fontanella - One of the best experts on this subject based on the ideXlab platform.
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studies of water in nafion membranes using deuteron and Oxygen 17 nuclear magnetic resonance and dielectric relaxation techniques
Journal of The Electrochemical Society, 1993Co-Authors: R.s. Chen, J.r.p. Jayakody, M.g. Mclin, G. Xu, S G Greenbaum, J J FontanellaAbstract:Deuteron and Oxygen-17 nuclear magnetic resonance measurements and dielectric relaxation studies of Nafion-117 membranes with variable water content (approximately 5-18% by weight) have been carried out. Glassy behavior of the water domains at low temperature, below ca. 200 K, is evidenced by the specific nature of the 1 H NMR line shapes. Activation energies extracted from 1 H spin-lattice relaxation data on the high temperature side of the T 1 minimum exhibit a steady increase with increasing water content. In spite of a high degree of molecular mobility, angular-dependent spectra in both as-received and stretched samples reflect considerable anisotropy of the host polymer
R.s. Chen - One of the best experts on this subject based on the ideXlab platform.
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Dielectric relaxation measurements and deuteron and Oxygen-17 NMR of hydrated nafion membranes
1993Co-Authors: M.g. Mclin, R.s. Chen, J.r.p. Jayakody, Mary C. Wintersgill, John J. Fontanella, Steve GreenbaumAbstract:Perfluorinated ion exchange membranes, such as Nafion, are currently the object of intense interest due to their potential use as separators in fuel cells. It is well known that the presence of water in these membranes enhances the protonic conductivity, however, a detailed understanding of the role of water in protonic transport is still incomplete. As a contribution to this problem the authors will discuss the dependence of dielectric relaxation, deuteron and Oxygen-17 T{sub 1} NMR relaxation times on both pressure and water content.
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studies of water in nafion membranes using deuteron and Oxygen 17 nuclear magnetic resonance and dielectric relaxation techniques
Journal of The Electrochemical Society, 1993Co-Authors: R.s. Chen, J.r.p. Jayakody, M.g. Mclin, G. Xu, S G Greenbaum, J J FontanellaAbstract:Deuteron and Oxygen-17 nuclear magnetic resonance measurements and dielectric relaxation studies of Nafion-117 membranes with variable water content (approximately 5-18% by weight) have been carried out. Glassy behavior of the water domains at low temperature, below ca. 200 K, is evidenced by the specific nature of the 1 H NMR line shapes. Activation energies extracted from 1 H spin-lattice relaxation data on the high temperature side of the T 1 minimum exhibit a steady increase with increasing water content. In spite of a high degree of molecular mobility, angular-dependent spectra in both as-received and stretched samples reflect considerable anisotropy of the host polymer
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Studies of Water in Nafion Membranes Using Deuteron and Oxygen‐17 Nuclear Magnetic Resonance, and Dielectric Relaxation Techniques
Journal of The Electrochemical Society, 1993Co-Authors: R.s. Chen, J.r.p. Jayakody, Steve Greenbaum, M.g. Mclin, G. Xu, John J. FontanellaAbstract:Deuteron and Oxygen-17 nuclear magnetic resonance measurements and dielectric relaxation studies of Nafion-117 membranes with variable water content (approximately 5-18% by weight) have been carried out. Glassy behavior of the water domains at low temperature, below ca. 200 K, is evidenced by the specific nature of the 1 H NMR line shapes. Activation energies extracted from 1 H spin-lattice relaxation data on the high temperature side of the T 1 minimum exhibit a steady increase with increasing water content. In spite of a high degree of molecular mobility, angular-dependent spectra in both as-received and stretched samples reflect considerable anisotropy of the host polymer
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Studies of Water in Nafion Membranes: Dielectric Relaxation and Deuteron and Oxygen-17 NMR
1993Co-Authors: R.s. Chen, Steve Greenbaum, M.g. Mclin, Jay R. P. Jayakody, G. Xu, John J. FontanellaAbstract:Abstract : Dielectric relaxation and both deuteron and Oxygen-17 nuclear magnetic resonance measurements on NAFION-117 membranes with variable water content (approx. 5 - 18 % by weight) are reported. Glassy behavior of the water domains at low T (below approx. 200 K) is evidenced by the specific nature of the observed dielectric loss peaks and 2 H NMR lineshapes. Activation energies extracted from 2 H spin-lattice relaxation data on the high T side of the T sub one minimum exhibit a steady increase with increasing water content. In spite of a high degree of water molecular mobility, angular-dependent spectra in both as- received and stretched samples reflect considerable anisotropy of the host polymer. A dielectric loss peak is observed which has previously been attributed to the glass transition of the aqueous domains.
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Deuteron and Oxygen-17 NMR Studies of Molecular Motion in Methanol- Saturated Nafion Membranes
MRS Proceedings, 1992Co-Authors: R.s. Chen, J.r.p. Jayakody, Steve GreenbaumAbstract:Abstract : Deuteron and Oxygen-17 NMR linewidth and spin-lattice relaxation measurements in Nafion-117 films containing methanol at -75% and -100% saturation are reported. Molecular motion probed by room temperature measurements in stretched films and low T measurements in unstretched films is found to be quite rapid compared to previous results obtained for Nafion-117 containing water.
Martin Bendszus - One of the best experts on this subject based on the ideXlab platform.
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quantitative dynamic Oxygen 17 mri at 7 0 t for the cerebral Oxygen metabolism in glioma
Radiology, 2020Co-Authors: Daniel Paech, Armin M Nagel, Miriam Schultheiss, Reiner Umathum, Sebastian Regnery, Moritz Scherer, Antje Wick, Tanja Platt, Wolfgang Wick, Martin BendszusAbstract:Oxygen 17 MRI at 7.0 T showed that oxidative glycolysis was reduced in participants with glioma in accordance with the Warburg effect (increased glycolysis in malignancy followed by lactic acid fer...
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Quantitative Dynamic Oxygen 17 MRI at 7.0 T for the Cerebral Oxygen Metabolism in Glioma.
Radiology, 2020Co-Authors: Daniel Paech, Armin M Nagel, Miriam Schultheiss, Reiner Umathum, Sebastian Regnery, Moritz Scherer, Antje Wick, Tanja Platt, Wolfgang Wick, Martin BendszusAbstract:Background Altered metabolism is a characteristic of cancer. Because of a shift in glucose metabolism from oxidative phosphorylation to lactate production for energy generation, malignant tumors are characterized by increased glycolysis followed by lactic acid fermentation, even in the presence of abundant Oxygen (the Warburg effect). Purpose To quantitatively investigate dynamic Oxygen 17 ((17)O) MRI in healthy participants and participants with untreated glioma to understand altered cerebral Oxygen metabolism in glioma. Materials and Methods In this prospective study conducted from September 2016 to June 2018, individuals with newly diagnosed previously untreated glioma (World Health Organization grade II-IV) and healthy volunteers were included. Dynamic (17)O MRI was performed with a 7.0-T whole-body system. (17)O2 gas inhalation enabled dynamic measurement of the cerebral metabolic rate of Oxygen (CMRO2) consumption. In healthy volunteers and participants with glioma, CMRO2 values in gray matter and white matter volumes were compared by using Wilcoxon signed rank tests. In participants with glioma, the tumor volume and tumor subcompartments were compared with normal-appearing gray matter and white matter by using Friedman test followed by Holm-Sidak post hoc tests. Results Ten participants (mean age, 42 years +/- 18 [standard deviation]; nine men) with glioma and three healthy volunteers (mean age, 44 years +/- 21; all men) were evaluated. CMRO2 was higher in normal-appearing gray matter compared with white matter in both participants with glioma (2.36 mumol/g/min +/- 0.22 vs 0.75 mumol/g/min +/- 0.10, respectively) and healthy volunteers (2.38 mumol/g/min +/- 0.15 vs 0.63 mumol/g/min +/- 0.05, respectively) (P < .001 and P = .03, respectively). In the tumor region, CMRO2 was reduced (high-grade tumor CMRO2, 0.23 mumol/g/min +/- 0.07; low-grade tumor CMRO2, 0.39 mumol/g/min +/- 0.16; overall CMRO2, 0.34 mumol/g/min +/- 0.16) compared with normal-appearing gray matter (P < .001) and normal-appearing white matter (P < .001) in accordance with the Warburg theorem. Conclusion Dynamic Oxygen 17 MRI method at 7.0 T as a direct metabolic imaging technique in glioma enabled quantitative visualization of the Warburg effect. A general reduction in oxidative glycolysis was observed in accordance with the Warburg theorem. (c) RSNA, 2020 Online supplemental material is available for this article. See also the editorial by Rapalino in this issue.
