ISMRM 21st Annual Meeting & Exhibition 20-26 April 2013 Salt Lake City, Utah, USA

MRS of the Brain
Friday 26 April 2013
Room 255 EF  10:30 - 12:30 Moderators: Penny Anne Gowland, Tracy R. McKnight

10:30 0854.   Quantitative Standardization of Volumetric Whole-Brain MR Spectroscopic Imaging
Mohammad Sabati1, Sulaiman Sheriff1, Meng Gu2, Henry Zhu3, Peter B. Barker3, Daniel Spielman2, and Andrew A. Maudsley1
1Radiology, University of Miami, Miami, FL, United States, 2Radiology, Stanford University, Stanford, CA, United States, 3Radiology, Johns Hopkins University, Baltimore, MD, United States

MR spectroscopic imaging (MRSI) offers considerable potential for detection of alterations in tissue metabolism; however, the use of current techniques for clinical studies and multi-center trials remains limited due to variability of implementations across sites and manufactures scanners; restrictive implementations in terms of the spatial extent over which data is obtained; and relative complexity of the data analysis. To address these limitations a standardized volumetric ‘whole-brain’ 1H MRSI sequence has been implemented on scanners from three different manufacturers at three sites and combined with a fully automated MRSI processing procedure. Results were compared using a spectroscopic phantom and thirty aged-matched normal subjects.

10:42 0855.   Real-Time Motion and Shim Correction by Volumetric EPI Navigators Improves 3D LASER Localized Spiral MRSI of the Brain at 3T
Wolfgang Bogner1,2, Aaron T. Hess3, Borjan Gagoski4, Matthew Dylan Tisdall1, André J. W. van der Kouwe1, Siegfried Trattnig2, and Ovidiu C. Andronesi1
1Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States, 2MR Center of Excellence, Department of Radiology, Medical University Vienna, Vienna, Austria, 3Department of Cardiovascular Medicine, University of Oxford, Oxford, United Kingdom, 4Fetal-Neonatal Neuroimaging & Developmental Science Center, Children’s Hospital Boston, Harvard Medical School, Boston, MA, United States

High-field MR spectroscopic imaging (MRSI) is limited by localization artifacts (i.e., imperfect selection profiles, chemical shift errors, B1 inhomogeneities), motion-related artifacts (i.e., position changes, phase artifacts, B0 changes, lipid artifacts), and long measurement times (i.e., causing reduced spatial coverage and low spatial resolution). Low-power localized adiabatic selective refocusing (LASER) provides accurate selection even at high fields. Real-time position- and B0-updating using volumetric navigators suppresses motion-related artifacts. Spiral encoding accelerates MRSI acquisition and thereby enables 3D-coverage with high spatial resolution. Our study illustrates the benefits of combining all three approaches to allow fast and robust 3D-MRSI of the brain at 3T.

10:54 0856.   A Pilot Evaluation of Accelerated Echo-Planar J-Resolved Spectroscopic Imaging in the Human Brain Using Compressed Sensing
Manoj K. Sarma1, Rajakumar Nagarajan1, Jonathan Furuyama1, Jenny Li1, Paul M. Macey2, Rajesh Kumar3, and M. Albert Thomas1
1Radiological Sciences, UCLA School of Medicine, Los Angeles, CA, United States, 2School of Nursing, UCLA School of Medicine, Los Angeles, CA, United States, 3Neurobiology, UCLA School of Medicine, Los Angeles, CA, United States

Compressed Sensing (CS) has revolutionized medical imaging with optimal encoding/reconstruction schemes for MRI and hyperpolarized MRSI. There have been no reports on combining 2 spectral dimensions with 2D or 3D spatial encoding applicable to human brain pathologies so far and the CS-based approaches are well-suited for MRSI combining 2 spectral and 2 spatial dimensions. We have evaluated a novel four dimensional (4D) echo-planar J-resolved spectroscopic imaging (EP-JRESI) sequence using non-uniform under-sampling (NUS) approaches for acceleration and CS for reconstruction in healthy human brain in vivo. The sequence has been implemented on a 3T MRI scanner equipped with a 12-channel head coil. Eight healthy volunteers and one patient with obstructive sleep apnea (OSA) have been evaluated. The 2D J-resolved spectra extracted from the CS-reconstructed 4D EP-JRESI data were processed using the prior-knowledge fitting (ProFit) algorithm to quantify cerebral metabolites in hippocampus and other locations.

11:06 0857.   Two-Dimensional J-Resolved LASER Spectroscopy of Human Brain at 3T
Meijin Lin1, Anand Kumar1, and Shaolin Yang1,2
1Department of Psychiatry, University of Illinois at Chicago, Chicago, IL, United States, 2Department of Radiology, University of Illinois at Chicago, Chicago, IL, United States

In this report, two-dimensional (2D) J-resolved spectroscopy using localization by adiabatic selective refocusing (LASER), named as “J-resolved LASER”, was introduced to suppress the chemical shift artifacts, additional J-refocused artifactual peaks resulted from spatially dependent J-coupling evolution, and the sensitivity to radiofrequency field inhomogeneity. Phantom and human experiments were performed to demonstrate the feasibility and advantages of J-resolved LASER spectroscopy over conventional J-resolved spectroscopy (JPRESS).

11:18 0858.   NAAG Detection in the Human Brain by Wiener Filtering and TE Optimization at 7T
Li An1, Shizhe Li1, Emily T. Wood2,3, Daniel S. Reich2,3, and Jun Shen1
1National Institute of Mental Health, National Institutes of Health, Bethesda, MD, United States, 2NeuroImmunology Branch (NINDS), National Institutes of Health, Bethesda, MD, United States, 3Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD, United States

The accuracy and precision of in vivo measurements of n-acetyl-aspartyl-glutamate (NAAG) are often limited because the NAAG singlet at 2.05 ppm overlaps with the n-acetyl-aspartate singlet at 2.01 ppm and the NAAG multiplet at 2.19 ppm is buried by other signals. In this work, we optimize the TEs of the PRESS sequence to improve NAAG detection at 7T. In addition, we also develop a water reference deconvolution algorithm to enhance spectral resolution by reducing lineshape distortions due to B0 inhomogeneities and residual eddy currents.

11:30 0859.   In Vivo MR Study of Intracellular NAD Contents and Redox State in Healthy Human Brain -permission withheld
Xiao-Hong Zhu1, Ming Lu1, Byeong-Yeul Lee1, Kamil Ugurbil1, and Wei Chen2
1Center of Magnetic Resonance Research, Department of Radiology, University of Minnesota Medical School, Minneapolis, MN, United States, 2Center of Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, MN, United States

Intracellular NAD (nicotinamide adenine dinucleotide) concentrations and redox state (define as the ratio between oxidized and reduced NAD) have been closely linked to the energy production, metabolic regulation and signal transduction processes occur in all living cells. Thus, the ability to study the intracellular NAD contents and redox state is essential for understanding their pivotal roles in brain function and dysfunctions. Despite the importance, however, the level of NAD or its redox ratio in normal human brain is virtually unknown because the lack of proper tools for in vivo measurements. In this study, we applied a novel 31P MRS approach recently developed in our lab to directly measure the NAD contents and the NAD+/NADH redox ratio in healthy human brains at 7T. The results reveal, for the first time, that i) it is feasible to robustly measure and identify the MRS signals of NAD+and NADH in the human brain; ii) the knowledge regarding the NAD and its redox state in human brain can be readily and non-destructively obtained; and iii) age-dependent changes exist in the intracellular NAD concentrations and NAD+/NADH redox states of the healthy human brains. This work presents a MR technology breakthrough and provides new opportunities for studying the central roles of the NAD and its redox in human health and diseases.

11:42 0860.   
Slice-Selective FID Acquisition of Proton Spectroscopic Imaging to Access Functional Metabolic Changes During GABAergic Stimulation with µl Resolution in the Mouse Brain
Aline Seuwen1, Aileen Schröter1, and Markus Rudin1,2
1ETH & University of Zürich, Zürich, Zürich, Switzerland, 2Institute of Pharmacology & Toxicology, Zürich, Zürich, Switzerland

Spectroscopic imaging (SI) in the mouse brain is very attractive in view of the many transgenic lines available for mechanistic study. However, due poor SNR and long acquisition times the investigation of dynamic processes remains difficult. In this work, slice-selective FID acquisition was used to access functional metabolic changes in the mouse brain upon systemic infusion of the GABAA antagonist bicuculline. Repeated acquisition of SI data with µl spatial resolution in 13 min enabled a reliable quantification of dose-dependent spectral changes induced by the administration of bicuculline.

11:54 0861.   In Vivo 31P MRS Imaging of Intracellular NAD Contents and NAD+/NADH Redox States in Normal and Ischemic Brains -permission withheld
Xiao-Hong Zhu1, Ming Lu1, Yi Zhang1, and Wei Chen2
1Center of Magnetic Resonance Research, Department of Radiology, University of Minnesota Medical School, Minneapolis, MN, United States, 2Center of Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, MN, United States

Nicotinamide adenine dinucleotide (NAD), as an important coenzyme and/or co-substrate in all living cells, plays vital roles in cellular metabolism and regulation. However, due to the technique limitation, it is very difficult to directly measure the NAD and its redox state (define as the ratio of oxidized and reduced forms: NAD+/NADH) in a live brain. We have developed an in vivo 31P MRS approach that is capable of quantitative and non-invasive imaging of the intracellular NAD levels and the NAD+/NADH ratio in intact organs, such as brain. In the present study, we applied this novel MRS approach to image the intracellular NAD contents, including the NAD+, NADH and total NAD concentrations, and the NAD+/NADH redox ratio in anesthetized cat brain under normal physiological condition, and in the rat brains under acute ischemia-recovery conditions. The results indicate that the NAD imaging approach can provide reliable measure of the cerebral NAD contents and redox state and is sensitive to detect their changes in response to physiopathological alteration in brain energy and metabolism; thus, has great values for basic biomedical research and potential for clinical translation.

12:06 0862.   Metabolic Flux Maps from 3D MRSI of Rat Brain in Situ
Sungtak Hong1, Golam M.I. Chowdhury2, Xiaomin Ma1, Monique Thomas2, Graeme F. Mason2, Gerard Sanacora2, Douglas L. Rothman1, Kevin L. Behar2, and Robin A. de Graaf1
1Diagnostic Radiology, Yale University, New Haven, Connecticut, United States, 2Psychiatry, Yale University, New Haven, Connecticut, United States

Recently, a new ex vivo assay that combines 3D magnetic resonance spectroscopic imaging (MRSI) with focused-beam microwave-euthanasia was developed to generate quantitative metabolic maps of brain metabolites at high spatial resolution. In this work, detailed processing procedures and routines are described to analyze 3D MRSI data acquired from rat brain receiving timed intravenous infusions of 13C labeled glucose. The rich dynamic metabolic information obtained in the resulting metabolic maps is demonstrated.

12:18 0863.   Oxygen-17 MRS for CMRO2 Measurements in the Mouse Brain at 16.4T
Weina Cui1, Xiao-Hong Zhu1, Manda Vollmers1, Emily Colonna1, Gregor Adriany1, Brandon Tramm2, Janet Dubinsky1, and Gulin Oz1
1University of Minnesota, Minneapolis, MN, United States, 2Virtumed, LLC, Minneapolis, MN, United States

To assess cerebral energetics in transgenic mouse models of neurological disease, a robust and quick method for quantification of cerebral oxygen consumption is needed. 17O MRS methodology has been validated in rats and cats to measure CMRO2, however mice present unique challenges due to their small size. We show that 17O MRS in the mouse brain is feasible with high sensitivity using 16.4T, a surface 1H/17O coil and a newly designed oxygen delivery system. The method can be utilized to measure mitochondrial function in mice quickly and repeatedly, without oral intubation, and has numerous potential applications to study cerebral energetics.