Lipid suppressed and tissue-fraction corrected metabolic distributions in human central brain structures using 2D ¹H Magnetic Resonance Spectroscopic Imaging at 7 tesla

Abstract

Magnetic resonance spectroscopic imaging (MRSI) has the potential to add a layer of understanding of the neurobiological mechanisms underlying brain diseases, disease progression, and treatment efficacy.Limitations related to metabolite fitting of low SNR data, signal variations due to partial volume effects, acquisition and extra-cranial lipid artefacts, along with clinically relevant aspects such as scan-time constraints, are among the factors that hinder the widespread implementation of in vivo MRSI. The aim of this work was to address these factors and to develop an acquisition, reconstruction and postprocessing pipeline to derive lipid suppressed metabolite values based on Free Induction Decay (FID-MRSI) measurements made using a 7 tesla MR scanner. Anatomical images were used to perform highresolution (1mm 3 ) partial-volume correction to account for grey matter, white matter and cerebralspinal fluid signal contributions. Implementation of automatic quality control thresholds and normalization of metabolic maps from 23 subjects to the MNI standard atlas facilitated the creation of high-resolution average metabolite maps of several clinically relevant metabolites in central brain regions, while accounting for macromolecular distributions. Reported metabolite values include glutamate, choline, (phospo)creatine, myo-inositol, glutathione, N-acetyl aspartyl glutamate(and glutamine) and N-acetyl aspartate. MNI-registered average metabolite maps facilitate group-based analysis; thus offering the possibility to mitigate uncertainty in variable MRSI.

Inter‐subject stability and regional concentration estimates of 3D‐FID‐MRSI in the human brain at 7 T

“…For metabolite ratios to tCr, we also compared our results with the 7 T MRSI results of Bhogal et al, 70 as seen in Table 8. Over the six compared ROIs, our ratios are consistently higher for all except GSH/tCr, which is mixed.…”