Helge Jörn Zöllner¹, Ipek Özdemir¹, Dillip K. Senapati¹, Michal Považan², Georg Oeltzschner¹, Kimberly Chan³, Doris D. M. Lin¹, and Peter B. Barker^1,4
1Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, MD, United States, ²3 Danish Research Centre for Magnetic Resonance, Hvidovre Hospital, Copenhagen, Denmark, ³Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX, United States, ⁴F. M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, United States

Reproducibility of multi-slice GABA-edited MRSI of the human brain recorded at 3T was investigated in 6 healthy adult volunteers, with and without a retrospective motion compensation scheme applied (MoCo). Overall reproducibility was good with improved performance when MoCo was applied (relative GABA+/tCr difference between visits: 20.8% no Moco, 10.0% with MoCo). Retrospective MoCo is a viable alternative for edited-MRSI when prospective motion correction is unavailable, at least in relatively compliant subject groups.

Ashley L Louie¹, Gavin Hamilton¹, Alexandra N Schlein¹, Walter C Henderson¹, Danielle N Batakis¹, Lael K Ceriani¹, Yesenia Covarrubias¹, Tanya Wolfson¹, Nikolaos Panagiotopolous², David T Harris², McMillan Alan², Daiki Tamada², Kathryn J Fowler¹, Scott B Reeder², and Claude B Sirlin^1
1Radiology, University of California, San Diego, La Jolla, CA, United States, ²Radiology, University of Wisconsin, Madison, WI, United States

The purpose of this study was to examine the relationship between water T1 and T2 estimated by Flip Angle Corrected Multi-Parameter (CMP) MRS and biopsy-determined fibrosis. The sample of twenty-eight subjects with biopsy and MRS data is part of a dual-center, weight loss surgery study. Subjects without fibrosis were found to have significantly higher CMP MRS T1 water values than patients with fibrosis.

Jule Kuhn¹, Kolja Them¹, and Jan-Bernd Hövener^1
1Section Biomedical Imaging, Molecular Imaging North Competence Center (MOIN CC), Department of Radiology and Neuroradiology, University Medical Center Schleswig - Holstein, Kiel University, Kiel, Germany

The PHIP-X methodology is a novel approach to hyperpolarize nuclei from specific molecules that could function as contrast agents in metabolic MRI. PHIP-X combines the strong polarization of hydrogenative PHIP with the broad applicability of proton exchange and opens up the variety of potential hyperpolarizable biomolecules. The presented experimental setup facilitates the application of pH₂ pressures up to 30 bar and well-defined external magnetic fields up to 80 mT. Using this setup allowed to hyperpolarize glucose (830 mM) and achieved increasing polarization with increasing the pressure from 10 bar to 20 bar (molar polarization was more than doubled).

Helge Jörn Zöllner^1,2, Yulu Song^1,2, Steve C. N. Hui^1,2, Peter B. Barker^1,2, Richard A. E. Edden^1,2, and Georg Oeltzschner^1,2
1Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, MD, United States, ²F. M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, United States

Recent work identified a 'best practice' linear-combination modeling (LCM) strategy for GABA-edited spectra using parameterized basis functions for co-edited macromolecules. Here we introduce a measured macromolecular basis function to evaluate possible improvements in the modeling.

Anouk Schrantee¹, Adam Berrington², Petra J Pouwels¹, Bram F Coolen³, Oliver Gurney-Champion¹, and Chloé F Najac^4
1Department of Radiology and Nuclear Medicine, Amsterdam University Medical Centers, Amsterdam, Netherlands, ²Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham, Nottingham, United Kingdom, ³Department of Biomedical Engineering and Physics, Amsterdam University Medical Centers, Amsterdam, Netherlands, ⁴C.J. Gorter Center for High-Field MRI, Department of Radiology, Leiden University Medical Center, Leiden, Netherlands

fMRS stimulation paradigms and analysis strategies are highly heterogeneous, partially due to lack of knowledge of the underlying metabolic response function. To better understand the potential consequences of analysis methods, this simulation study evaluates the effect of different glutamate response functions (GRFs) and binning strategies. As the GRF becomes more delayed, analyzing bins from spectra directly after ‘task’ onset results in underestimation of the true change. In moving average analyses, the fitted time-courses co-varied significantly with the input glutamate time-course. Future simulation studies will expand on other variable sources, such as habituation and hemodynamic effects, and macromolecule fitting procedures.

André Döring¹, Derek K Jones¹, and Roland Kreis^2,3
1Cardiff University Brain Research Imaging Centre (CUBRIC), Cardiff University, Cardiff, United Kingdom, ²Magnetic Resonance Methodology, Institute of Diagnostic and Interventional Neuroradiology, University Bern, Bern, Switzerland, ³Translational Imaging Center, sitem-insel, Bern, Switzerland

We demonstrate that, even without having water as an internal reference, a combination of spectral registration and fitting can restore artificial signal loss promoted by incoherent averaging due to frequency/phase drifts and motion-induced dephasing for the cardinal brain metabolites (tCr, tCho, tNAA, Glx and Ins) by using a set of synthetically distorted diffusion MR spectra (including realistic phase, frequency and amplitude fluctuations).

Marc Jonuscheit^1,2, Stefan Wierichs^1,2, Yuliya Kupriyanova^1,2, Michael Roden^1,2,3, and Vera Schrauwen-Hinderling^1,2,4
1Institute for Clinical Diabetology, German Diabetes Center, Leibniz Institute for Diabetes Research at Heinrich Heine University, Düsseldorf, Germany, ²German Center for Diabetes Research (DZD e.V.), München-Neuherberg, Germany, ³Department of Endocrinology and Diabetology, Medical Faculty, Heinrich Heine University, Düsseldorf, Germany, ⁴Department of Radiology and Nuclear Medicine, Maastricht University Medical Center, Maastricht, Netherlands

We determined day-to-day variation and intra-session reproducibility of ³¹P-MRS-based hepatic phosphorus metabolite quantification. To this end, we compared a standard single loop with a custom-created quadrature surface coil. Absolute concentrations of γ-adenosine triphosphate and inorganic phosphate were assessed in 7 volunteers with both coils. Both coils showed comparable day-to-day and intra-session CVs < 10 %. Metabolite concentrations determined by the two coils were similar. Therefore, both coils yield robust absolute concentrations of hepatic phosphorous metabolites. The quadrature coil allows measurements at a higher distance from the coil which can be important for the application in obese patients.

 

Kimberly L Chan¹ and Anke Henning^2,3
1Advanced Imaging Research Center, The University of Texas Southwestern, Dallas, TX, United States, ²The University of Texas Southwestern, Dallas, TX, United States, ³Max Planck Institute for Biological Cybernetics, Tübingen, Germany

We have shown that MultiNet, a neural-network-based image reconstruction, can reconstruct variable-density k-space undersampling schemes to decrease MRSI acquisition times.  This used a 4-step method where points are predicted by 4 successively-applied neural-networks off both acquired and previously predicted k-space points.  Herein, a 1-step method where points are only predicted off acquired k-space points to reduce reconstruction error was explored.  This method was trained using a new augmented MRSI training set and compared to the 4-step reconstruction of new CAIPIRINHA-based schemes and the original schemes.  The new 1-step reconstruction method was found to increase SNR and improve metabolic maps.

Tiffany K Bell^1,2,3, Alexander R Craven^4,5, Kenneth HugDahl^4,6,7, Ralphe Noeske⁸, and Ashley D Harris^1,2,3
1Department of Radiology, University of Calgary, Calgary, AB, Canada, ²Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada, ³Alberta Children's Hospital Research Institute, University of Calgary, Calgary, AB, Canada, ⁴Department of Biological and Medical Psychology, University of Bergen, Bergen, Norway, ⁵Department of Clinical Engineering, Haukeland University Hospital, Bergen, Norway, ⁶Division of Psychiatry, Haukeland University Hospital, Bergen, Norway, ⁷Department of Radiology, Haukeland University Hospital, Bergen, Norway, ⁸GE Healthcare, Berlin, Germany

Functional magnetic resonance spectroscopy (fMRS) of GABA at 3T is challenging due to the difficulties of measuring GABA levels; GABA is present in the brain at relatively low concentrations and its signal is overlapped by higher concentration metabolites. Here we use a continuous MEGA-PRESS acquisition to show changes in GABA levels measured in the sensorimotor cortex during motor learning and during a control button pressing task. This indicates GABA levels can be tracked during a functional experiment, allowing fMRS of GABA to be accessible at 3T, the more commonly used field strength.

Antoine Naëgel^1,2, Magalie Viallon¹, Jabrane Karkouri^1,2,3, Thomas Troalen², Kevin Moulin^1,2, Pierre Croisille¹, and Hélène Ratiney^1
1Université de Lyon, INSA-Lyon, Université Claude Bernard Lyon 1, UJM-Saint Etienne, CNRS, Inserm, CREATIS UMR 5220, U1206, Lyon, France, ²Siemens Healthineers, Saint-Denis, France, ³Wolfson Brain Imaging Center, University of Cambridge, Cambridge, United Kingdom

Exploring spatial distribution of intra- and extramyocellular lipids linked to the orientation of muscle fibers is complex. We used a magnetic resonance spectroscopic imaging (MRSI) technique with a spiral encoding of k-t space and diffusion imaging tractography at 3T to reveal possible concomitant factors. The IMCL preponderance index, exploiting the spectroscopic dimension and proposed in this study, highlights interesting and relevant patterns in some calf muscle heads.

Justyna Platek^1,2, Vanessa L. Franke^1,2, Mark E. Ladd^1,2,3, Peter Bachert^1,2, and Andreas Korzowski^1
1Division of Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany, ²Faculty of Physics and Astronomy, University of Heidelberg, Heidelberg, Germany, ³Faculty of Medicine, University of Heidelberg, Heidelberg, Germany

The non-invasive detection of 2-hydroxyglutarate (2HG) via ¹H MRS is of particular interest in brain tumors, but quantification of 2HG may be challenging due the spectral overlap with Glutamate and Glutamine. In this study, we implemented a simulation framework for the assessment of the quantification reliability for 2HG under realistic conditions, and demonstrated its application to a PRESS sequence at B₀=9.4T with a representative set of different TEs and SNR levels. With this framework, we aim to identify optimal acquisition parameters for the detection of 2HG in glioma mouse models at a 9.4-T small animal scanner in the future.

Anna M Chen¹, Teresa Gerhalter¹, Seena Dehkharghani^1,2, Rosemary Peralta¹, Fatemeh Adlparvar¹, Martin Gajdošík¹, Mickael Tordjman^1,3, Julia Zabludovsky¹, Sulaiman Sheriff⁴, Sinyeob Ahn⁵, James S Babb¹, Tamara Bushnik⁶, Alejandro Zarate⁶, Jonathan M Silver⁷, Brian S Im⁶, Stephen P Wall⁸, Guillaume Madelin¹, and Ivan I Kirov^1,2,9
1Center for Biomedical Imaging, Department of Radiology, New York University Grossman School of Medicine, New York, NY, United States, ²Department of Neurology, New York University Grossman School of Medicine, New York, NY, United States, ³Department of Radiology, Cochin Hospital, Paris, France, ⁴Department of Radiology, University of Miami Miller School of Medicine, Miami, FL, United States, ⁵Siemens Medical Solutions USA Inc., Malvern, PA, United States, ⁶Department of Rehabilitation Medicine, New York University Grossman School of Medicine, New York, NY, United States, ⁷Department of Psychiatry, New York University Grossman School of Medicine, New York, NY, United States, ⁸Ronald O. Perelman Department of Emergency Medicine, New York University Grossman School of Medicine, New York, NY, United States, ⁹Center for Advanced Imaging Innovation and Research, Department of Radiology, New York University Grossman School of Medicine, New York, NY, United States

¹H-MRS has the potential to provide biomarkers for mild traumatic brain injury (mTBI), a diagnosis in which damage is often imaging-occult, but a lack of replicability and reproducibility studies hampers clinical translation. Here, we tested the replicability of previous MRSI results in mTBI with a different patient cohort. Five out of seven hypotheses were consistent with previous work, with key findings of globally diffuse white matter (WM) injury and limited gray matter injury. However, we report differences in choline and creatine, not N-acetyl-aspartate. Correlations were found between metabolite levels in WM and both symptomatology and neuropsychological testing.