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The Capital Region of Denmark - a part of Copenhagen University Hospital
E-pub ahead of print

Identifying the source of spurious signals caused by B0 inhomogeneities in single-voxel 1 H MRS

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  • Zahra Shams
  • Dennis W J Klomp
  • Vincent O Boer
  • Jannie P Wijnen
  • Evita C Wiegers
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PURPOSE: Single-voxel MRS (SV MRS) requires robust volume localization as well as optimized crusher and phase-cycling schemes to reduce artifacts arising from signal outside the volume of interest. However, due to local magnetic field gradients (B0 inhomogeneities), signal that was dephased by the crusher gradients during acquisition might rephase, leading to artifacts in the spectrum. Here, we analyzed this mechanism, aiming to identify the source of signals arising from unwanted coherence pathways (spurious signals) in SV MRS from a B0 map.

METHODS: We investigated all possible coherence pathways associated with imperfect localization in a semi-localized by adiabatic selective refocusing (semi-LASER) sequence for potential rephasing of signals arising from unwanted coherence pathways by a local magnetic field gradient. We searched for locations in the B0 map where the signal dephasing due to external (crusher) and internal (B0 ) field gradients canceled out. To confirm the mechanism, SV-MR spectra (TE = 31 ms) and 3D-CSI data with the same volume localization as the SV experiments were acquired from a phantom and 2 healthy volunteers.

RESULTS: Our analysis revealed that potential sources of spurious signals were scattered over multiple locations throughout the brain. This was confirmed by 3D-CSI data. Moreover, we showed that the number of potential locations where spurious signals could originate from monotonically decreases with crusher strength.

CONCLUSION: We proposed a method to identify the source of spurious signals in SV 1 H MRS using a B0 map. This can facilitate MRS sequence design to be less sensitive to experimental artifacts.

Original languageEnglish
Article number29222
JournalMagnetic Resonance in Medicine
Volume88
Issue number1
Pages (from-to)71-82
Number of pages12
ISSN0740-3194
DOIs
Publication statusE-pub ahead of print - 28 Mar 2022

Bibliographical note

© 2022 International Society for Magnetic Resonance in Medicine.

    Research areas

  • H MRS, B inhomogeneity gradients, coherence pathways, spurious signals

ID: 75961462