Nicole D Fichtner1,2,3,4, Ioannis-Angelos Giapitzakis5,6, Nikolai Avdievich5, Ralf Mekle7, Daniel Zaldivar5, Anke Henning5,8, Roland Kreis1,2. 1. Department of Radiology, Neuroradiology, and Nuclear Medicine, University of Bern, Bern, Switzerland. 2. Department for BioMedical Research, University of Bern, Bern, Switzerland. 3. Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland. 4. Institute for Biomedical Engineering, UZH and ETH Zurich, Zurich, Switzerland. 5. Max Planck Institute for Biological Cybernetics, Tübingen, Germany. 6. Graduate School of Neural and Behavioural Sciences, Tübingen, Germany. 7. Center for Stroke Research Berlin (CSB), Charité Universitätsmedizin Berlin, Berlin, Germany. 8. Institute of Physics, Ernst-Moritz Arndt University Greifswald, Greifswald, Germany.
Abstract
PURPOSE: To perform exchange-rate measurements on the in vivo human brain downfield spectrum (5-10 ppm) at 9.4 T and to compare the variation in concentrations of the downfield resonances and of known upfield metabolites to determine potential peak labels. METHODS: Non-water-suppressed metabolite cycling was used in combination with an inversion transfer technique in two brain locations in healthy volunteers to measure the exchange rates and T1 values of exchanging peaks. Spectra were fitted with a heuristic model of a series of 13 or 14 Voigt lines, and a Bloch-McConnell model was used to fit the exchange rate curves. Concentrations from non-water-inverted spectra upfield and downfield were compared. RESULTS: Mean T1 values ranged from 0.40 to 0.77 s, and exchange rates from 0.74 to 13.8 s-1 . There were no significant correlations between downfield and upfield concentrations, except for N-acetylaspartate, with a correlation coefficient of 0.63 and P < 0.01. CONCLUSIONS: Using ultrahigh field allowed improved separation of peaks in the 8.2 to 8.5 ppm amide proton region, and the exchange rates of multiple downfield resonances including the 5.8-ppm peak, previously tentatively assigned to urea, were measured in vivo in human brain. Downfield peaks consisted of overlapping components, and largely missing correlations between upfield and downfield resonances-although not conclusive-indicate limited contributions from metabolites present upfield to the downfield spectrum. Magn Reson Med 79:2863-2873, 2018.
PURPOSE: To perform exchange-rate measurements on the in vivo human brain downfield spectrum (5-10 ppm) at 9.4 T and to compare the variation in concentrations of the downfield resonances and of known upfield metabolites to determine potential peak labels. METHODS: Non-water-suppressed metabolite cycling was used in combination with an inversion transfer technique in two brain locations in healthy volunteers to measure the exchange rates and T1 values of exchanging peaks. Spectra were fitted with a heuristic model of a series of 13 or 14 Voigt lines, and a Bloch-McConnell model was used to fit the exchange rate curves. Concentrations from non-water-inverted spectra upfield and downfield were compared. RESULTS: Mean T1 values ranged from 0.40 to 0.77 s, and exchange rates from 0.74 to 13.8 s-1 . There were no significant correlations between downfield and upfield concentrations, except for N-acetylaspartate, with a correlation coefficient of 0.63 and P < 0.01. CONCLUSIONS: Using ultrahigh field allowed improved separation of peaks in the 8.2 to 8.5 ppm amide proton region, and the exchange rates of multiple downfield resonances including the 5.8-ppm peak, previously tentatively assigned to urea, were measured in vivo in human brain. Downfield peaks consisted of overlapping components, and largely missing correlations between upfield and downfield resonances-although not conclusive-indicate limited contributions from metabolites present upfield to the downfield spectrum. Magn Reson Med 79:2863-2873, 2018.
Authors: Ivan Tkáč; Dinesh Deelchand; Wolfgang Dreher; Hoby Hetherington; Roland Kreis; Chathura Kumaragamage; Michal Považan; Daniel M Spielman; Bernhard Strasser; Robin A de Graaf Journal: NMR Biomed Date: 2020-12-16 Impact factor: 4.478
Authors: Roland Kreis; Vincent Boer; In-Young Choi; Cristina Cudalbu; Robin A de Graaf; Charles Gasparovic; Arend Heerschap; Martin Krššák; Bernard Lanz; Andrew A Maudsley; Martin Meyerspeer; Jamie Near; Gülin Öz; Stefan Posse; Johannes Slotboom; Melissa Terpstra; Ivan Tkáč; Martin Wilson; Wolfgang Bogner Journal: NMR Biomed Date: 2020-08-17 Impact factor: 4.044