Layla Tabea Riemann¹, Christoph Stefan Aigner¹, Ralf Mekle², Sebastian Schmitter^1,3,4, Bernd Ittermann¹, and Ariane Fillmer^1
1Physikalisch-Technische Bundesanstalt (PTB), Berlin, Germany, ²Center for Stroke Research Berlin, Charité Universitätsmedizin, Berlin, Germany, ³Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States, ⁴Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany

For simultaneous multi-voxel spectroscopy (sMVS), it is necessary to optimize the B₀ shimming and the B₁⁺ adjustment simultaneously for two voxels. The impact of these adjustments on the smallest possible distance for simultaneous two-voxel MRS acquisitions is determined by Bloch simulations, and the influence on the spectral quality is assessed for three different brain regions. To this end, the previously introduced 2 spin-echo full-intensity acquired localization (2SPECIAL) sequence and the voxel-GeneRalized Autocalibrating Partial Parallel Acquisition (vGRAPPA) decomposition algorithm are utilized to simultaneously acquire and retrospectively decompose in vivo brain ¹H-MRS data from two voxels at short echo times at 7T.

Mohamed Tachrount¹, Jason Lerch^1,2, and Stuart Clare^1
1Wellcome Centre for Integrative Neuroimaging (FMRIB), Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom, ²Mouse Imaging Centre (MICe), University of Toronto, Toronto, ON, Canada

The goals of this study were to implement a MEGA-sLASER sequence with prospective field drift correction on a preclinical scanner, develop the processing tools and validate them on a group of wild type mice.

Lisa Y Hung¹, Karl-Heinz Herrmann¹, Renat Sibgatulin¹, Lydiane Hirschler^2,3, Jan Warnking³, Emmanuel L Barbier³, Otto W Witte⁴, Knut Holthoff⁴, Jürgen R Reichenbach¹, and Alexander Joerk^4
1Medical Physics Group, Institute of Diagnostic Radiology, Jena University Hospital, Jena, Germany, ²Department of Radiology, Leiden University Medical Center, Leiden, Netherlands, ³Grenoble Institut Neurosciences, Univ. Grenoble Alpes, Inserm, U1216, Grenoble, France, ⁴Hans-Berger Department of Neurology, Jena University Hospital, Jena, Germany

Attaining reproducible, time-efficient, high spatial resolution and quantitative MRI perfusion images in small animal MRI @9.4T is still challenging. To take a step toward this goal, perfusion data from arterial spin labeling (ASL), Flow-sensitive Alternating Inversion Recovery (FAIR), dynamic susceptibility contrast (DSC), and pseudo-continuous arterial spin labeling (pCASL) sequences are compared by assessing cerebral perfusion in 5 rats, each scanned 3 times. Differences in (cerebral blood flow) CBF in major brain regions were analyzed, and the repeatability of perfusion MRI was assessed.

Sriranga Kashyap^1,2, Dimo Ivanov², Roy A. M. Haast³, Francisco J. Fritz⁴, Robbert L. Harms², Benedikt A. Poser², and Kamil Uludag^5,6
1Techna Institute, University Health Network, Toronto, ON, Canada, ²Department of Cognitive Neuroscience, Maastricht University, Maastricht, Netherlands, ³Aix-Marseille Universite, CNRS, CRMBM, Marseille, France, ⁴Institute for Systems Neuroscience, Universitätsklinikum Hamburg-Eppendorf, Hamburg, Germany, ⁵Techna Institute & Koerner Scientist in MR Imaging, University Health Network, Toronto, ON, Canada, ⁶Center for Neuroscience Imaging Research, Institute for Basic Science & Department of Biomedical Engineering, Sungkyunkwan University, Suwon, Korea, Republic of

In this work, we use 3D-EPI ASL to acquire perfusion maps of the human brain at an unprecedented spatial resolution of 0.7 mm isotropic at 7T. This multi-session, single-subject ASL dataset offers a unique opportunity to investigate the cortical distribution of baseline perfusion across and within brain areas, as well as studying the physiological basis for the interpretation of laminar and columnar fMRI. In this abstract, we use an open-source, memory-efficient, CPU/GPU accelerated coil-combine Python toolbox to probe the impact of using covariance-weighted sum-of-squares (CovSoS) and tSNR optimised RF coil-combination (STARC) on high-resolution perfusion imaging at 7T. 

Ashok Kumar P Reddy¹, Harsh Kumar Agarwal¹, Rajdeep Das¹, Rajagopalan Sundaresan¹, Shaik Ahmed¹, Sajith Rajamani¹, Bhairav Mehta¹, Gaohong Wu¹, M Ramasubba Reddy², and Ramesh Venkatesan^1
1GE Healthcare, Bangalore, India, ²Indian Institute of Technology Madras, Chennai, India

Obesity is a key biomarker of liver pathology. Diffusion MRI in liver is key protocol in the absence on intravenous contrast agent and also provides additional insights on diffuse liver diseases and lesions However, its usage is limited by the inability to use multi-channel surface coil for obese liver patients in non-wide-bore MRI scanners. A variable k-space sampling scheme and auto-calibrating image reconstruction technique, vARC, is proposed in this abstract to reduce the amount of distortion and improve the image quality of Liver DWI acquired with single channel volume coil.

Rajakumar Nagarajan¹, Gwenael Layec², and Jane A Kent^2
1Human Magnetic Resonance Center, Institute for Applied Life Sciences, University of Massachusetts Amherst, Amherst, MA, United States, ²Kinesiology, University of Massachusetts Amherst, Amherst, MA, United States

Given its central role in substrate metabolism, the ability to quantify muscle glycogen (Gly) continuously and noninvasively using natural abundance ¹³C MR spectroscopy presents an important opportunity for understanding human metabolism. This study evaluated the reproducibility of Gly measured by ¹³C MRS in the quadriceps muscle using three methods for signal standardization at 3T: Gly/total creatine (TCr) from ¹³C, Gly/TCr using ¹³C and ¹H, and Gly/water. The novel results from this study suggest that Gly/TCr measurements using the creatine peak from ¹H MRS is highly reproducible and may be an advantageous approach to measuring muscle glycogen in the future. 

Emile Schjeldsøe Berg¹ and John Georg Seland^1
1Department of Chemistry, University of Bergen, Bergen, Norway

The editing capabilities of the MEGA-PRESS sequence are combined with diffusion-weighing to enable both quantification and diffusion measurements of less abundant brain metabolites. The technique, labelled DW-MEGA-PRESS, was tested for combined editing and diffusion-weighting of GABA. Obtained data give reliable results for GABA concentrations and corresponding diffusion coefficients from in vitro experiments. When applied to in vivo acquisitions, reliable diffusion coefficients for the dominating metabolites were obtained. GABA could be reliably quantified, but the signal-to-noise ratio was not sufficient for a reliable determination of its diffusion coefficient. This could be improved by further optimization of scanning and post-processing protocols.

Songi Lim^1,2, Mark Stephan Widmaier^1,2, and Lijing Xin^1,3
1CIBM Center for Biomedical Imaging, Lausanne, Switzerland, ²Laboratory for Functional and Metabolic Imaging, EPFL, Lausanne, Switzerland, ³Animal Imaging and Technology, EPFL, Lausanne, Switzerland

Phase-cycled spectroscopic imaging (PCSI) method was implemented and validated for ³¹P PCSI imaging at 7T. The PCSI method uses a balanced steady-state free precession sequence with an ultra-low flip angle (<1°) to achieve sharp passband with 2.52-ms of TR, which enable to accelerate the acquisition. With prior knowledge of ³¹P spectra, it is feasible to acquire major ³¹P peaks by changing the frequency offset and non-uniform phase sweeping instead of acquiring full spectra uniformly. To investigate feasibility of the method, a multi-compartment KH₂PO₄ phantom with in vivo equivalent concentrations was prepared and ³¹P PCSI was compared with conventional FID-CSI.

Gaurav Verma¹, Seena Dehkharghani², Leeor Alon³, and Priti Balchandani^1
1Biomedical Engineering and Imaging Institute, Icahn School of Medicine at Mount Sinai, New York, NY, United States, ²Radiology and Neurology, New York University, New York, NY, United States, ³Radiology, New York University, New York, NY, United States

A spectrally-interleaved semi-adiabatic magnetic resonance spectroscopic imaging sequence was developed to simultaneously acquire water and metabolite resonances within the same repetition time. A water interleave enables eddy current correction, absolute quantification through water reference and thermometry using empirically-derived formulae based on chemical shifts of temperature-sensitive water and temperature-insensitive metabolites. The sequence successfully acquired both 1-minute single voxel and 4-minute multi-voxel acquisitions in phantom and in vivo, producing temperature estimates of 21.2 °C, and 35.7 °C, respectively. LCModel fitting of metabolites provided reliable fitting of multiple metabolite peaks including separation of glutamate and glutamine.

Lorenz Pfleger^1,2, Wolfgang Bogner², Albrecht Ingo Schmid³, Thomas Scherer¹, Peter Wolf¹, Michael Krebs¹, and Martin Krššák^1,4
1Division of Endocrinology and Metabolism, Department of Medicine III, Medical University of Vienna, Vienna, Austria, ²High Field MR Centre, Department of Biomedical Imaging and Image-guided Therapy, Medical University of Vienna, Vienna, Austria, ³High Field MR Centre, Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria, ⁴Christian Doppler Laboratory for Clinical Molecular MR Imaging, Vienna, Austria

This study focuses on the comparison of different in vivo data-acquisitions for quantifying hepatic ³¹P metabolite concentrations using a phantom replacement method. We have compared a 1D-slab localized DRESS, a single-voxel-spectroscopy (SVS) ISIS as well as a 3D-CSI ³¹P MRS acquisition at 7T. Each method has its own advantages and disadvantages and needs to be chosen according to the focus and design of the study.

Alexandru V Avram^1,2, Magdoom Kulam¹, Joelle E Sarlls³, Raisa Freidlin⁴, and Peter J Basser^1
1Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, United States, ²Center for Neuroscience and Regenerative Medicine, The Henry Jackson Foundation, Bethesda, MD, United States, ³National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, United States, ⁴Center for Information Technology, National Institutes of Health, Bethesda, MD, United States

We describe a comprehensive pipeline for super-resolution reconstruction of clinical diffusion-weighted MRIs acquired with isotropic diffusion encoding (IDE), or spherical tensor encoding. The pipeline integrates blip-up/down EPI distortion correction and slice-to-volume registration (SVR). Multiple low-resolution IDE-MRIs with different slice orientations relative to the brain are processed to reconstruct high-resolution IDE-MRIs. From high-resolution IDE-MRIs with a wide range of b-values we estimate spectra of subvoxel MD values to describe the distribution of water mobilities in microscopic brain tissue microenvironments. Integrating SVR-reconstruction with IDE is an important step in the clinical translation of MD spectroscopic MRI for fetal MRI applications.

Tal Finkelman¹, Edna Furman-Haran², Rony Paz³, and Assaf Tal^1
1Chemical and Biological Physics, Weizmann, Rehovot, Israel, ²Life Sciences Core Facilities, Weizmann, Rehovot, Israel, ³Brain Sciences, Weizmann, Rehovot, Israel

Glutamate (Glu) and γ‑aminobutyric-acid (GABA) are central neurotransmitters participating in many cognitive processes, and their combined measurement is of great relevance. Proton Magnetic Resonance Spectroscopy (¹H-MRS) allows the no–invasive, in-vivo, measurement of GABA and Glu. At magnetic fields below 7T, GABA is detected by spectral editing strategies, while Glu is detected by non-editing strategies. We compared both edited and non‑edited approaches at 7T for simultaneously quantifying Glu and GABA from 21 volunteers, and found that non-edited sequences at TE=80ms provide better combined-reproducibility than either edited sequences at the same TE, or non-edited sequence at a shorter TE (42ms).

Tobit Führes¹, Marc Saake ¹, Hannes Seuss^1,2, Astrid Müller¹, Sebastian Bickelhaupt¹, Alto Stemmer³, Thomas Benkert³, Michael Uder¹, Bernhard Hensel⁴, and Frederik Bernd Laun^1
1University Hospital Erlangen, Erlangen, Germany, ²Klinikum Forchheim, Forchheim, Germany, ³Siemens Healthcare GmbH, Erlangen, Germany, ⁴Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany

Diffusion-weighted imaging of the liver is prone to the cardiac pulsation artifact, which can lead to reduced lesion visibility. We addressed this problem with a two-fold approach. First, flow-compensated diffusion weightings were used, which are known to reduce this artifact. Using a dataset of 40 patients suffering from focal liver lesions, we addressed the remaining signal voids with different postprocessing techniques, namely weighted averaging, the p-mean approach, and an outlier exclusion algorithm. The algorithms substantially increased the lesion visibility and further reduced the pulsation artifact. An evaluation of CNR and calculation time showed that weighted averaging was suited best.

Leo Cheng¹, Matteo Sanchez-Dahl¹, Isabella Muti¹, JianXiang Weng¹, and Anya Zhong^1
1Massachusetts General Hospital, Charlestown, MA, United States

The lack of a standard universal protocol for sample preparation in MRS experiments results in instrumental and biological variability across reported studies. The purpose of this experiment is to evaluate a quality assurance protocol for performing HRMAS ¹H MRS experiments with human biofluid samples, such as blood serum. The research objective is to determine if the spectral results measured from pooled samples can be used to assess results from individual samples as controls. These findings will help better develop efficient standard protocols for researchers and clinicians to use in the future.