Diffusion Weighted Magnetic Resonance Spectroscopy

Itamar Ronen, Hermien Kan, Chloé Najac, Andrew Webb, Ece Ercan


Background

Intracellular metabolites that give rise to quantifiable MR resonances are excellent structural probes for the intracellular space, and are oftentimes specific, or preferential enough to a certain cell type to provide information that is also cell-type specific. In the brain, N-acetylaspartate (NAA) and glutamate (Glu) are predominantly neuronal/axonal in nature, whereas soluble choline compounds (tCho), myo-inositol (mI) and glutamine (Gln) are predominantly glial. Similarly, in skeletal muscle, creatine and phosphocreatine (tCr), as well as choline compounds are abundant within muscle fibers. The diffusion properties of these metabolites, examined by diffusion weighted MR spectroscopy (DWS) predominantly and sometime exclusively reflect properties of the intracellular milieu, thus report on properties such as cytosolic viscosity, macromolecular crowding, tortuosity of the intracellular space, the integrity of the cytoskeleton and other intracellular structures, and in some cases – intracellular sub-compartmentation and exchange.
Above: examples of MR spectra taken from parietal white matter at diffusion weighting of b = 0 and 14,500 s/mm2. Right: metabolite ADC as measured in the corpus callosum of groups of healthy controls, patients with systemic lupus erythematosus (SLE) and SLE patients with neuropsychiatric symptoms (NP-SLE). Glial metabolites (tCr, tCho) showed higher ADC, indicating glial reactivity in response to neuroinflammation in NP-SLE.

Goal

  1. Development and implementation of acquisition methods for DWS for high and ultrahigh field MRI scanners,  covering both single volume acquisition and spectroscopic imaging.
  2. Investigation of tissue structure using DWS in combination with diffusion weighted imaging and other microstructural imaging methods to provide a compartment-specific account of tissue microstructure in health and disease.
  3. Study of physiology and brain function using functional DWS.

Collaborations


Institute for Brain and Spinal Cord (ICM), Paris, France
Molecular Imaging research center (MIRCen), Fontenay-aux-Roses, France
University of Ulm, Ulm, Germany
National Institutes for Neurological Disorders and Stroke (NIH/NINDS), Bethesda MA, USA
Danish Research Centre for Magnetic Resonance (DRCMR), Copenhagen, Denmark
Lund University Bioimaging Center, Lund, Sweden
Cardiff University Brain Research Imaging Centre (CUBRIC), Cardiff, UK

Selected publications

  • M Palombo, N Shemesh, I Ronen, J Valette, Insights into brain microstructure from in vivo DW-MRS, NeuroImage, 2017, , ISSN 1053-8119, https://doi.org/10.1016/j.neuroimage.2017.11.028.
  • A. E. Ercan, C. Magro-Checa, R. Valabregue, F. Branzoli, E. T. Wood, G. M. Steup-Beekman, A. Webb, T. Huizinga, M. A. van Buchem, and I. Ronen, Glial and Axonal Changes in Systemic Lupus Erythematosus Measured With Diffusion of Intracellular Metabolites, Brain. 2016 May;139(Pt 5):1447-57
  • Ronen, I., M. Budde, E. Ercan, J. Annese, A. Techawiboonwong, and A. Webb, Microstructural organization of axons in the human corpus callosum quantified by diffusion-weighted magnetic resonance spectroscopy of N-acetylaspartate and post-mortem histology, Brain Struct Funct. 2014 Sep;219(5):1773-85.