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Non‐water‐excitation MR spectroscopy techniques to explore exchanging protons in human brain at 3 T

Type of publication Peer-reviewed
Publikationsform Original article (peer-reviewed)
Author Dziadosz Martyna, Bogner Wolfgang, Kreis Roland,
Project Metabolic Fingerprints from Magnetic Resonance: Levels, Maps, and Microstructure
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Original article (peer-reviewed)

Journal Magnetic Resonance in Medicine
Publisher Wiley
Volume (Issue) 84
Page(s) 2352 - 2363
Title of proceedings Magnetic Resonance in Medicine
DOI 10.1002/mrm.28322

Open Access

URL https://boris.unibe.ch/id/eprint/145135
Type of Open Access Green OA Embargo (Freely available via Repository after an embargo)

Abstract

Purpose To develop localization sequences for in vivo MR spectroscopy (MRS) on clinical scanners of 3 T to record spectra that are not influenced by magnetization transfer from water. Methods Image‐selected in vivo spectroscopy (ISIS) localization and chemical‐shift‐selective excitation (termed I‐CSE) was combined in two ways: first, full ISIS localization plus a frequency‐selective spin‐echo and second, two‐dimensional (2D) ISIS plus a frequency‐selective excitation and slice‐selective refocusing. The techniques were evaluated at 3 T in phantoms and human subjects in comparison to standard techniques with water presaturation or metabolite‐cycling. ISIS included gradient‐modulated offset‐independent adiabatic (GOIA)‐type adiabatic inversion pulses; echo times were 8‐10 ms. Results The novel 2D and 3D I‐CSE methods yield upfield spectra that are comparable to those from standard MRS, except for shorter echo times and a limited frequency range. On the downfield/high‐frequency side, they yield much more signal for exchangeable protons when compared to MRS with water presaturation or metabolite‐cycling and longer echo times. Conclusion Novel non‐water‐excitation MRS sequences offer substantial benefits for the detection of metabolite signals that are otherwise suppressed by saturation transfer from water. Avoiding water saturation and using very short echo times allows direct observation of faster exchanging moieties than was previously possible at 3 T and additionally makes the methods less susceptible to fast T2 relaxation.
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