MR Spectroscopy

GABA (γ-Aminobutyric acid) and Glutamate are the main inhibitory and excitatory neurotransmitters in the brain, as well as important for energy metabolism. Using Magnetic Resonance Spectroscopy (MRS; an MRI-technique), it is possible to measure GABA and Glu (or more often Glx, combined glutamate + glutamine) in the living brain non-invasively. Our lab both develops and applies MR spectroscopy techniques

Edited MRS

Our lab has used “edited” MRS for over 10 years now. Dr. Puts first performed MRS during his PhD and then continued his training during his postdoc and faculty appointment at Johns Hopkins under Prof. Richard Edden. We continue to have a strong collaboration with his team and that of Dr. Georg Oeltzschner at JHU.

Edited MRS refers to ‘J-difference editing’ whereby the inherent J-coupling of a metabolite of interest is used to selectively edit this molecule. This is most-often used for low-concentration metabolites that are difficult to measure with conventional MRS approaches.

In brief:

  1. We use advanced edited MRS methods developed at Johns Hopkins (including multiplexed editing approaches such as HERMES and HERCULES)
  2. We apply these methods in health and clinical conditions, adults and children. We have expertise with children with autism, ADHD (3T and 7T, Tourette syndrome 3T and 7T, as well as adults e.g. with pain syndromes.
  3. We combine MRS with other imaging or behavioural approaches to link these measures with brain metabolism (GABA & Glu function) including EEG, TMS, and sensory/cognitive measures.

Collaboration

  1. We support the acquisition, analysis, and interpretation of edited MRS to sites world-wide (as well as in consortia such as AIMS-2-TRIALS)
  2. We support the development and dissemination of MRS analysis approaches and software (although less so since the move to London where our focus lies on application)

Functional MRS

We have recently begun to work with functional MRS or fMRS; using MRS to measure dynamic changes in metabolite concentration as a response to changes in condition (e.g. to a stimulus). fMRS is in it’s early days and we are learning day-by-day about the intricacies of these methods.

Our current focus lies on examining the impact of different measurement approaches (block vs event-related designs) as well as the impact of binning on signal quality and quantification, and development of sliding window analyses.

For now, watch this space.


Reporting standards

We have a strong emphasis on open and transparent science. All our upcoming work, data, and scripts will be shared online.

With respect to reporting standards, with Aimie Peek we developed an MRS-quality assessment and assurance tool, the MRS-Q, which can be used for reviewers or individuals undertaking meta-analysis to extract quality metrics for MRS papers. This tool was based on prior published consensus work. [Here]1

We were then also part of the MRSinMRS (Minimum Reporting Standards in MRS) consensus paper that more broadly outlines reporting standards for when publishing MRS data. [Here]2

  1. Peek AL, Rebbeck T, Puts NA, Watson J, Aguila MR, Leaver AM. Brain GABA and glutamate levels across pain conditions: A systematic literature review and meta-analysis of 1H-MRS studies using the MRS-Q quality assessment tool. Neuroimage. 2020 Apr 15;210:116532. doi.org/10.1016/j.neuroimage.2020.116532. Epub 2020 Jan 18. PMID: 31958584.
  2. Lin A, Andronesi O, Bogner W, Choi IY, Coello E, Cudalbu C, Juchem C, Kemp GJ, Kreis R, Krššák M, Lee P, Maudsley AA, Meyerspeer M, Mlynarik V, Near J, Öz G, Peek AL, Puts NA, Ratai EM, Tkáč I, Mullins PG; Experts’ Working Group on Reporting Standards for MR Spectroscopy. Minimum Reporting Standards for in vivo Magnetic Resonance Spectroscopy (MRSinMRS): Experts’ consensus recommendations. NMR Biomed. 2021 May;34(5):e4484. doi.org/10.1002/nbm.4484. Epub 2021 Feb 9. PMID: 33559967.