B₀ shimming for in vivo magnetic resonance spectroscopy: Experts' consensus recommendations

Abstract

Magnetic resonance spectroscopy (MRS) and spectroscopic imaging (MRSI) allow the chemical analysis of physiological processes in vivo and provide powerful tools in the life sciences and for clinical diagnostics. Excellent homogeneity of the static B 0 magnetic field over the object of interest is essential for achieving high-quality spectral results and quantitative metabolic measurements. The experimental minimization of B 0 variation is performed in a process called B 0 shimming. In this article, we summarize the concepts of B 0 field shimming using spherical harmonic shimming techniques, specific strategies for B 0 homogenization and crucial factors to consider for implementation and use in both brain and body. In addition, experts' recommendations are provided for minimum requirements for B 0 shim hardware and evaluation criteria for the primary outcome of adequate B 0 shimming for MRS and MRSI, such as the water spectroscopic linewidth.

High-resolution metabolic imaging of high-grade gliomas using 7T-CRT-FID-MRSI

“…In order to reliably image gliomas in the basal parts of the brain, significant improvements in B 0 shim hardware is warranted to improve B 0 homogeneity throughout the brain ( Juchem et al, 2020 , Wilson et al, 2019 ). Together with motion correction, this will improve the robustness of 7T MRSI, particularly when whole-brain coverage is required ( Maudsley et al, 2020 ).…”

Minimum Reporting Standards for in vivo Magnetic Resonance Spectroscopy (MRSinMRS): Experts' consensus recommendations

“…g. Shimming method, 10 reference peak used for assessing shim performance, and thresholds for "acceptance of shim" chosen.…”

Contribution of macromolecules to brain 1H MR spectra: Experts' consensus recommendations

“…2 However, the line broadening resulting from microscopic ΔB 0 increases linearly with B 0. 2,43 Even though the ΔB 0 , macro component can be substantially minimized by successful B 0 shimming, 45 the ΔB 0 , micro component cannot be eliminated as it originates from intrinsic tissue heterogeneity on a cellular level. Therefore, the effect of ΔB 0 , micro line broadening should be identical for metabolites and MM.…”