Diffusion weighted MRS: methods, microstructural investigations and clinical applications
Intracellular metabolites that give rise to quantifiable MR resonances are unique 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. The diffusion properties of these metabolites, examined by diffusion weighted MR spectroscopy (DWS) exclusively reflect properties of the intracellular milieu, thus reflecting 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.
The presentation will introduce some of the methodological concepts of DWS and the particular challenges of acquiring robust DWS for accurate estimation of metabolite diffusion properties. Subsequently, the unique ability of DWS to characterize cell-type specific structural and physiological features will be demonstrated, as well as acquisition strategies aimed at characterizing compartment-specific microscopic anisotropy (µFA) in tissue. Finally, applications of DWS to discern cell-type specific intracellular damage in disease will be presented.
Itamar Ronen completed his PhD in physical chemistry in 1998 in Tel Aviv University under the supervision of Prof. Gil Navon, where he developed a method for indirect NMR detection of 17O, with potential applications to metabolic functional imaging. Subsequently he spent 5 years at the Center for Magnetic Resonance Research (CMRR) at the University of Minnesota, where he was a post-doctoral fellow under the guidance of Seong-Gi Kim, Dae-Shik Kim and Kamil Ugurbil. Itamar’s first faculty position was at the Department of Anatomy and Neurobiology in the Boston University School of Medicine, where he worked between 2003 and 2009. There he helped start the Center for Biomedical Imaging where he served as the Head of MR Physics, and co-founded and co-directed a Master’s degree in Bioimaging. Since 2009 Itamar is an Associate Professor at the department of Radiology at the LUMC and a principal investigator at the C.J. Gorter Center for High Field MRI. His main interest is in developing MR-based methods for quantifying neural tissue microstructure and physiology in health and disease.