Itamar Ronen

Noam Shemesh¹, Jens T Rosenberg^2,3, Jean-Nicolas Dumez⁴, Lucio Frydman^2,5, and Samuel C Grant^2,3
1Champalimaud Neuroscience Programme, Champalimaud Centre for the Unknown, Lisbon, Portugal, ²National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL, United States, ³Chemical & Biomedical Engineering, Florida State University, Tallahassee, FL, United States, ⁴Institut de Chimie des Substances Naturelles, CNRS, UPR2301, Gif-sur-Yvette, France, ⁵Chemical Physics, Weizmann Institute of Science, Rehovot, Israel

Cellular-specific microarchitectures are altered with neurodegeneration and neuroplasticity, yet their characterization remains elusive, especially because most diffusion MR techniques rely on ubiquitous water signals. Here, we present a methodology capable of depicting cellular-specific microarchitectures in vivo. We employ Relaxation Enhanced 1H MRS at 21.1 T, and selectively target N-Acetylaspartate and myo-Inositol resonances as markers for neurons and astrocytes, respectively. When coupled with a double Pulsed Field Gradient filter, RE-MRS provides the sensitivity required for characterization of cellular-specific morphologies. Randomly oriented cell processes were selectively detected. These findings provide a framework for future characterizations of diseased and healthy tissues.

Stefan Posse^1,2, Kevin F Tagne³, and Stephen R Dager^4
1Neurology, U New Mexico, Albquerque, NM, United States, ²Physics and Astronomy, U New Mexico, Albuquerque, NM, United States, ³Neurology, U New Mexico, Albuquerque, NM, United States, ⁴Radiology, U Washington, Seattle, WA, United States

Diffusion tensor spectroscopic imaging (DTSI) in human brain provides intracellular markers for studying axonal development and neurological disorders. To address the strong motion sensitivity of existing phase encoded DTSI we developed single-shot narrow-bandwidth proton-echo-planar-spectroscopic-imaging with cardiac-gating and navigator correction. Data acquired in healthy volunteers demonstrate feasibility of mapping the tensor of water and the ADC of metabolites across an entire slice. The ADCs of tissue water, Cho, Cr and NAA were consistent with previous studies using single voxel measurements. Residual sensitivity to rotational motion that impacts mapping of the diffusion tensor of metabolites and navigator-based solutions will be discussed.

Xiaoyu Jiang¹, Hua Li¹, Ping Zhao¹, Jingping Xie¹, John C. Gore¹, and Junzhong Xu^1
1Institute of Imaging Science, vanderbilt university, nashville, Tennessee, United States

Oscillating gradient spin echo (OGSE) methods have been used previously to probe variations in tissues at cellular and subcellular scales, but their ability to accurately measure larger cell sizes (e.g. than 10 μm) is limited. Pulse gradient spin echo (PGSE) acquisitions use long diffusion times and sample the low frequency region of temporal diffusion spectra. Combinations of OGSE and PGSE acquisitions can sample a larger region of temporal diffusion spectra over a broader range of diffusion times than any single method on its own, and hence allow an accurate quantification of intracellular volume fractions and relatively large mean cell sizes.

Clemence Ligneul^1,2, Chloé Najac^1,2, Julien Flament^1,3, and Julien Valette^1,2
1CEA/DSV/I2BM/MIRCen, Fontenay-aux-Roses, France, ²CNRS URA 2210, Fontenay-aux-Roses, France, ³Inserm US27, CRC-MIRCen, Fontenay-aux-Roses, France

Measuring diffusion at ultra-short td may yield information about short-range obstacles and cytosol viscosity. However, reaching such td usually requires oscillating gradients, which in turn imply long echo times TE. Here we propose a new kind of stretched oscillating gradients that allow increasing b while preserving spectral and temporal properties of the gradient modulation. We then use these optimized gradients to measure metabolite diffusion in the mouse brain down to td=1 ms while keeping TE relatively short. The strong macromolecule signal can be used as an internal reference of null diffusivity, allowing us to discard spectra corrupted by motion artifacts.

Francesca Branzoli^1,2, Benedetta Bodini^1,2, Romain Valabrègue^1,2, Itamar Ronen³, Daniel Garcia-Lorenzo^1,2, Bruno Stankoff^1,2, and Stephane Lehéricy^1,2
1Institut du Cerveau et de la Moelle épinière – ICM, Centre de Neuroimagerie de Recherche – CENIR, Paris, France, ²Sorbonnes Université, Université Pierre et Marie Curie and Inserm UMR-S1127; CNRS, UMR 7225, Paris, France, ³C. J. Gorter Center for High Field MRI, Department of Radiology, Leiden University Medical Center, Leiden, Netherlands, Netherlands

Neuroaxonal degeneration is thought to play a major role in determining permanent disability in patients with multiple sclerosis. Diffusion-weighted MR spectroscopy offers the unique opportunity to investigate in vivo the diffusivity of N-acetylaspartate (NAA), which is considered to be a specific marker for axonal degeneration. Here, we provide our preliminary results on the comparison between the diffusion properties of water, NAA, total creatine and choline compounds measured in the normal appearing white matter (NAWM) of patients with multiple sclerosis and in the WM of aged-matched healthy controls . We found a decrease in ADC(NAA) in patients' normal-appearing white matter, which reflects the microstructural alterations resulting from the presence of axonopathy outside visible lesions.

Stefan Ruschke¹, Michael Dieckmeyer¹, Hendrik Kooijman², Axel Haase³, Ernst J. Rummeny¹, Jan S. Bauer⁴, Thomas Baum¹, and Dimitrios C. Karampinos^1
1Department of Diagnostic and Interventional Radiology, Technische Universität München, Munich, Bayern, Germany, ²Philips Healthcare, Hamburg, Hamburg, Germany, ³Zentralinstitut für Medizintechnik, Technische Universität München, Garching, Bayern, Germany, ⁴Neuroradiology, Technische Universität München, Munich, Bayern, Germany

Bone marrow fat composition has been attracting significant attention due to its connection to bone health. Vertebral bone marrow fat unsaturation has been traditionally quantified relying on the olefinic fat peak in the spectrum from a single-voxel short-TE MRS experiment. However, the broad peaks in the vertebral bone marrow MR spectrum and the presence of a strong water peak next to the olefinic peak can hinder a reliable extraction of the olefinic fat peak. The present work proposes a diffusion-weighted MRS experiment to extract the olefinic fat peak relying on the large difference in the diffusion coefficient between water and fat using a diffusion constraint fitting routine.

Llewellyn Jalbert¹, Evan Neill², Joanna Phillips³, Annette Molinaro³, Susan Chang³, and Sarah Nelson^1,2
1Joint Graduate Program in Bioengineering, UCSF, San Francisco, CA, United States, ²Radiology & Biomedical Imaging, UCSF, CA, United States,³Neurological Surgery, UCSF, CA, United States

Here we present quantitative in vivo MR imaging parameters capable of distinguishing the process of Malignant Transformation (MT) and IDH-mutation status in patients with recurrent, low-grade glioma.

Brice Tiret^1,2, Vincent Lebon^1,2, Julien Valette^1,2, and Pierre-Gilles Henry^3
1CEA/DSV/I2BM/MIRCen, Fontenay-aux-Roses, France, ²CNRS, URA 2210, Fontenay-aux-Roses, France, ³CMRR, Minneapolis, MN, United States

¹³C MRS together with labeled substrate infusion is a minimally invasive technique used to probe the TCA cycle. Despite previous efforts, traditional models fail to explain individual isotopomer (or more precisely, bonded cumomers) dynamics. Using a rapid model screening method, it becomes possible to use previously untapped information given by bonded cumomers to improve the bi-compartmental model. Such improvements include adding a vesicular glutamate pool and a double dilution of labeled plasmatic pyruvate.

Paul de Heer¹, Maurice B Bizino², Maarten J Versluis¹, Andrew G Webb¹, and Hildo J Lamb^2
1CJ Gorter Center for High Field MRI, Radiology, Leiden University Medical Center, Leiden, Zuid Holland, Netherlands, ²Radiology, Leiden University Medical Center, Leiden, Zuid Holland, Netherlands

Quantification of myocardial triglyceride content using cardiac proton magnetic resonance spectroscopy (1H-MRS) has proven to be important in the field of cardiovascular disease related to obesity, metabolic syndrome and diabetes mellitus type 2. However, cardiac 1H-MRS is challenging due to an intrinsic low signal-to-noise ratio (SNR). In this study we have shown in twenty healthy volunteers that by the application of the high permittivity pads the SNR increased from (mean±SD) 27.9±15.6 to 42.3±24.4 (p<0.0001), resulting in a mean gain factor of 1.6±0.51 allowing a reduction in acquisition time by a factor of 2.5, without compromising spectral quality.