Dataset Information

Sensitivity and specificity of human brain glutathione concentrations measured using short-TE (1)H MRS at 7 T.

ABSTRACT: Although the MR editing techniques that have traditionally been used for the measurement of glutathione (GSH) concentrations in vivo address the problem of spectral overlap, they suffer detriments associated with inherently long TEs. The purpose of this study was to characterize the sensitivity and specificity for the quantification of GSH concentrations without editing at short TE. The approach was to measure synthetically generated changes in GSH concentrations from in vivo stimulated echo acquisition mode (STEAM) spectra after in vitro GSH spectra had been added to or subtracted from them. Spectra from five test subjects were synthetically altered to mimic changes in the GSH signal. To account for different background noise between measurements, retest spectra (from the same individuals as used to generate the altered data) and spectra from five other individuals were compared with the synthetically altered spectra to investigate the reliability of the quantification of GSH concentration. Using STEAM spectroscopy at 7 T, GSH concentration differences on the order of 20% were detected between test and retest studies, as well as between differing populations in a small sample (n = 5) with high accuracy (R(2) > 0.99) and certainty (p ? 0.01). Both increases and decreases in GSH concentration were reliably quantified with small impact on the quantification of ascorbate and ?-aminobutyric acid. These results show the feasibility of using short-TE (1)H MRS to measure biologically relevant changes and differences in human brain GSH concentration. Although these outcomes are specific to the experimental approach used and the spectral quality achieved, this study serves as a template for the analogous scrutiny of quantification reliability for other compounds, methodologies and spectral qualities.

SUBMITTER: Deelchand DK

PROVIDER: S-EPMC4833663 | biostudies-literature | 2016 May

REPOSITORIES: biostudies-literature

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Sensitivity and specificity of human brain glutathione concentrations measured using short-TE (1)H MRS at 7 T.

Deelchand Dinesh K DK Marjańska Małgorzata M Hodges James S JS Terpstra Melissa M

NMR in biomedicine 20160222 5

Although the MR editing techniques that have traditionally been used for the measurement of glutathione (GSH) concentrations in vivo address the problem of spectral overlap, they suffer detriments associated with inherently long TEs. The purpose of this study was to characterize the sensitivity and specificity for the quantification of GSH concentrations without editing at short TE. The approach was to measure synthetically generated changes in GSH concentrations from in vivo stimulated echo acq ...[more]

PMID: 26900755

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Project description:Mutations in isocitrate dehydrogenase 1 and 2 (IDH1/2) are frequently found in brain tumors, and the resulting onco-metabolite, 2-hydroxyglutarate (2HG), has been suggested to be a potential diagnostic and prognostic biomarker of the diseases. Indeed, recent studies have demonstrated the feasibility of non-invasively detecting 2HG by using proton magnetic resonance spectroscopy (1H-MRS). Due to severe spectral overlaps of 2HG with its background metabolites and spectral baselines, however, the majority of those previous studies employed spectral editing methods with long echo times (TEs) instead of the most commonly used short TE approach with spectral fitting. Consequently, the results obtained with spectral editing methods may potentially be prone to errors resulting from substantial signal loss due to relaxation. Given that the spectral region where the main signal of 2HG resides is particularly sensitive to spectral baseline in metabolite quantification, we have investigated the impact of incorporating voxel-specifically measured baselines into the spectral basis set on the performance of the conventional short TE approach in 2HG detection in rodent models (Fisher 344 rats; n = 19) of IDH1/2 mutant-overexpressing F98 glioma at 9.4T. Metabolite spectra were acquired (SPECIAL sequence) for a tumor region and the contralateral normal region of the brain for each animal. For the estimation of spectral baselines metabolite-nulled spectra were obtained (double-inversion-recovery SPECIAL sequence) for each individual voxels. Data were post-processed with and without the measured baselines using MRUI and LCModel-the two most widely used data post-processing packages. Our results demonstrate that in-vivo detection of 2HG using the conventional short TE approach is challenging even at 9.4T. However, incorporation of voxel-specifically measured spectral baselines may potentially improve its performance. Upon more thorough validation in a larger number of animals and more importantly in human patients, the potential utility of the proposed short TE acquisition with voxel-specific baseline measurement approach in 2HG detection may need to be considered in the study design.

Dataset Information

Sensitivity and specificity of human brain glutathione concentrations measured using short-TE (1)H MRS at 7 T.

Publications

Sensitivity and specificity of human brain glutathione concentrations measured using short-TE (1)H MRS at 7 T.

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