The separation of Gln and Glu in STEAM: a comparison study using short and long TEs/TMs at 3 and 7 T

Dou, Weiqiang; Kaufmann, Jörn; Li, Meng; Walter, Martin; Speck, Oliver

doi:10.1007/s10334-014-0479-7

Cited by 13 publications

(7 citation statements)

References 39 publications

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“…It would appear that a combination of LCModel peak fitting and spectral editing is a better choice to obtain more accurate quantification of metabolites that suffer from overlapping peaks. However, a study at 7 T, comparing phantom quantification of Gln and Glu obtained with short‐ and long‐TE STEAM sequences, demonstrated that the higher SNR, short‐TE spectra yielded comparable quantification with that obtained from the long‐TE spectra with lower CRLB values . In addition, T 2 values of metabolites can change with disease .…”

Section: Discussionmentioning

confidence: 99%

“…However, a study at 7 T, comparing phantom quantification of Gln and Glu obtained with short-and long-TE STEAM sequences, demonstrated that the higher SNR, short-TE spectra yielded comparable quantification with that obtained from the long-TE spectra with lower CRLB values. 67 In addition, T 2 values of metabolites can change with disease. 68,69 Therefore, if T 2 cannot be determined, a short-TE method may be a better alternative.…”

Section: Discussionmentioning

confidence: 99%

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Improved resolution of glutamate, glutamine and γ‐aminobutyric acid with optimized point‐resolved spectroscopy sequence timings for their simultaneous quantification at 9.4 T

2017

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Funding information Natural Sciences and Engineering Research Council of CanadaGlutamine (Gln), glutamate (Glu) and γ-aminobutyric acid (GABA) are relevant brain metabolites that can be measured with magnetic resonance spectroscopy (MRS). This work optimizes the point-resolved spectroscopy (PRESS) sequence echo times, TE 1 and TE 2 , for improved simultaneous quantification of the three metabolites at 9.4 T. Quantification was based on the proton resonances of Gln, Glu and GABA at ≈2.45, ≈2.35 and ≈2.28 ppm, respectively. Glu exhibits overlap with both Gln and GABA; in addition, the Gln peak is contaminated by signal from the strongly coupled protons of N-acetylaspartate (NAA), which resonate at about 2.49 ppm. J-coupling evolution of the protons was characterized numerically and verified experimentally. A {TE 1 , TE 2 } combination of {106 ms, 16 ms} minimized the NAA signal in the Gln spectral region, whilst retaining Gln, Glu and GABA peaks. The efficacy of the technique was verified on phantom solutions and on rat brain in vivo. LCModel was employed to analyze the in vivo spectra. The average T 2 -corrected Gln, Glu and GABA concentrations were found to be 3.39, 11.43 and 2.20 mM, respectively, assuming a total creatine concentration of 8.5 mM. LCModel Cramér-Rao lower bounds (CRLBs) for Gln, Glu and GABA were in the ranges 14-17%, 4-6% and 16-19%, respectively. The optimal TE resulted in concentrations for Gln and GABA that agreed more closely with literature concentrations compared with concentrations obtained from short-TE spectra acquired with a {TE 1 , TE 2 } combination of {12 ms, 9 ms}. LCModel estimations were also evaluated with short-TE PRESS and with the optimized long TE of {106 ms, 16 ms}, using phantom solutions of known metabolite concentrations. It was shown that concentrations estimated with LCModel can be inaccurate when combined with short-TE PRESS, where there is peak overlap, even when low (<20%) CRLBs are reported.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Improved resolution of glutamate, glutamine and γ‐aminobutyric acid with optimized point‐resolved spectroscopy sequence timings for their simultaneous quantification at 9.4 T

2017

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“…With the increased spectral dispersion at an ultra‐high field, the increased ability to assess Glu and GABA from the same measurement session provides a more reliable assessment of the association of these neurotransmitters with rsFC in the same individuals. Additionally, the validity of the applied measurement strategy in this study has been investigated (Dou et al, 2015), particularly in the human cingulate cortex subregions (Dou et al, 2013).…”

Section: Discussionmentioning

confidence: 99%

“…A single‐average water signal served as the internal reference for quantification and eddy‐current correction. The positioning of the two MRS voxels that followed anatomical landmarks is described in previous papers from our group (Dou et al, 2013; Dou et al, 2015).…”

Section: Methodsmentioning

confidence: 99%

The differential association between local neurotransmitter levels and whole‐brain resting‐state functional connectivity in two distinct cingulate cortex subregions

Zhang

Danyeli

Čolić

et al. 2022

Human Brain Mapping

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Reproducible resting-state functional connectivity (rsFC) patterns and their alterations play an increasing role in neuropsychiatric research. Studies that limit the analysis of metabolites and rsFC strengths to a predefined canonical network suggest that the rsFC strength positively correlates with the local glutamate (Glu) levels and negatively correlates with the gamma-aminobutyric acid (GABA) levels. The contribution of regional neurotransmitter activity to rsFC strengths from a given seed to the whole-brain remains unclear. In this study, 121 healthy participants (50 female/71 male) underwent multimodal resting-state functional magnetic resonance imaging (rsfMRI) and magnetic resonance spectroscopy (MRS) at 7 T, allowing for acquisition of multiple, neuroanatomically well-defined MRS voxels in the same session. We examined the association between rsFC and local neurotransmitter levels in the

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“…The modulation in the STEAM sequence arising from scalar coupling is governed by both TE and mixing time (TM). The optimisation of the STEAM sequence timing parameters has been investigated for the improved acquisition of scalar‐coupled metabolites at ultra high‐field, such as glutamate 12‐14 . For lactate measurement, previous work reported an analytical expression derived for the STEAM signal modulation in a weakly‐coupled spin system of the lactate form, 15 AX 3 , where A corresponds to the proton in the methine group and X to those in the methyl group.…”

Section: Introductionmentioning

confidence: 99%

Investigating the regional effect of the chemical shift displacement artefact on the J‐modulated lactate signal at ultra high‐field

et al. 2020

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The present work aims to show the applicability of an analytical model for the optimisation of the STEAM sequence timing parameters for lactate detection at ultra highfield. The effects of the chemical shift displacement artefact on the J-modulated signal for a weakly-coupled spin system were considered in the three applied directions of field gradients and the product operator formalism was used to obtain expressions for the signal modulation in each compartment of the excited volume. The validity of this model was demonstrated experimentally at 7 T in a phantom and acquisitions with optimised parameters were performed on a healthy volunteer. The spectra acquired with TE = 144 ms with the optimised mixing time and TE = 288 ms showed easily detectable lactate peaks in the normal human brain. Additionally, the acquisition with the longer TE resulted in a spectrum with less lipid/macromolecular contamination. The simulations shown here demonstrated that the proposed analytical model is suitable for correctly predicting the resulting lactate signal. With the optimised parameters, it was possible to use a simple sequence with sufficient signal-to-noise ratio to reliably distinguish lactate from overlapping resonances in a healthy brain.

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The separation of Gln and Glu in STEAM: a comparison study using short and long TEs/TMs at 3 and 7 T

Abstract: Based on the optimal separation for Gln and Glu, a short TE/TM at 7 T is proposed for future in vivo Gln and Glu acquisition.

Cited by 13 publications

References 39 publications

Improved resolution of glutamate, glutamine and γ‐aminobutyric acid with optimized point‐resolved spectroscopy sequence timings for their simultaneous quantification at 9.4 T

Improved resolution of glutamate, glutamine and γ‐aminobutyric acid with optimized point‐resolved spectroscopy sequence timings for their simultaneous quantification at 9.4 T

The differential association between local neurotransmitter levels and whole‐brain resting‐state functional connectivity in two distinct cingulate cortex subregions

Investigating the regional effect of the chemical shift displacement artefact on the J‐modulated lactate signal at ultra high‐field

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