Robin A. de Graaf¹, Henk M. De Feyter¹, Peter B. Brown¹, Terence W. Nixon¹, Douglas L. Rothman¹, and Kevin L. Behar^1
1MRRC, Yale University, New Haven, CT, United States

Nicotinamide adenine dinucleotide (NAD+) has a central role in cellular metabolism and energy production and is related to gene expression, calcium mobilization, aging, cell death and timing of metabolism via the circadian rhythm. The in vivo detection of NAD+ has traditionally been limited and has only recently been demonstrated on rat brain with 1H and 31P NMR spectroscopy. Here the detection of NAD+ by 1H NMR spectroscopy is extended to human brain at 7 T. Results are quantitatively compared to those obtained with in vivo 31P NMR spectroscopy.

Ralf Mekle¹, Johanna Balz², Julian Keil², Yadira Roa-Romero², Semiha Aydin¹, Florian Schubert¹, Bernd Ittermann¹, Juergen Gallinat³, and Daniel Senkowski^2
1Medical Physics, Physikalisch-Technische Bundesanstalt, Berlin, Germany, ²Department of Psychiatry and Psychotherapy, Charité-Universitätsmedizin, Berlin, Germany, ³Department of Psychiatry and Psychotherapy, University Hospital Hamburg-Eppendorf, Hamburg, Germany

The integration of different sensory streams into a coherent, conscious percept is required for multisensory perception, where in human brain the superior temporal gyrus (STG) plays an important role. In this combined MRS-EEG study, the sound-induced flash illusion (SIFI) paradigm was applied to test the hypotheses that the GABA concentration in the STG predicts multisensory perception at the behavioral level and gamma-band activity during SIFI. MRS data were acquired using MEGA-PRESS at 3T, and EEG signals were recorded for 40 subjects. The hypotheses were confirmed, and a tight triangular relationship between GABA concentration, gamma-band oscillations, and multisensory perception was found.

Patrik Oliver Wyss^1,2, Andreas Hock^1,3, Milan Scheidegger^1,3, Niklaus Zoelch¹, Markus Rudin^1,4, Spyros Kollias², and Anke Henning^1,5
1Institute for Biomedical Engineering, UZH and ETH Zurich, Zurich, Zurich, Switzerland, ²Institute of Neuroradiology, University Hospital Zurich, Zurich, Zurich, Switzerland, ³Department of Psychiatry, Psychotherapy and Psychosomatics Hospital of Psychiatry, University of Zurich, Zurich, Zurich, Switzerland, ⁴Institute of Pharmacology and Toxicology, University of Zurich, Zurich, Zurich, Switzerland, ⁵Max Planck Institute for Biological Cybernetics, Tuebingen, Germany

The precise assessment of transverse relaxation time constant T₂ of brain metabolites is a prerequisite for reporting quantitative MR spectroscopy results. To reveal differences of T₂ in gray and white matter, echo time series data were recorded in 91 healthy volunteer at 3T and evaluated using ProFit2.0. Different T₂relaxation times in gray and white matter exist for mi, cho, naa, glu and naag, which should be considered and precisely evaluated for. Differences may show changes in degrees of freedom and therefore may be used to reveal a variation of cell compartments or interaction between molecules and enzymes.

Chen Chen¹, Peter Morris¹, Susan Francis¹, and Penny Gowland^1
1Sir Peter Mansfield Imaging Centre (SPMIC), University of Nottingham, Nottingham, Nottinghamshire, United Kingdom

GABA detection at 7T (B1,max=15uT) using an optimised long TE MEGA-sLASER spectral editing sequence was compared with a conventional short TE STEAM sequence in terms of 1) reproducibility and 2) measured [GABA]/[Cr+]. This study showed that 1) the intra-subject reproducibility of both methods was high (CV%=5-6%); 2) the inter-subject reproducibility of MM-corrected MEGA-sLASER was higher than STEAM, especially when the GABA concentration was low; 3) [GABA] ]/[Cr+] measured using both methods correlated well (r=0.69, p=0.006).

Liang Fang^1,2, Minjie Wu¹, Hengyu Ke², Anand Kumar¹, and Shaolin Yang^1,3
1Department of Psychiatry, University of Illinois at Chicago, Chicago, IL, United States, ²School of Electronic Information, Wuhan University, Wuhan, Hubei, China, ³Department of Radiology, University of Illinois at Chicago, Chicago, IL, United States

Multi-element coil arrays are commonly used in magnetic resonance imaging (MRI) for parallel imaging. However, how to combine the magnetic resonance spectroscopy (MRS) signal from a multi-element receiving coil array has been much less studied than imaging. In this study, we proposed a new method for theoretical optimal combination no matter the noise is correlated or uncorrelated among different coil elements. The validation experiments were performed with different voxel locations/sizes on a 3T MRI scanner with an 8-element head coil. The results verified the superior performance of the proposed method compared with the recently published and other routine combination methods.

Zhongxu An¹, Sandeep Ganji¹, Elizabeth A. Maher¹, Dianne Mendelsohn¹, Marco Pinho¹, Kevin Choe¹, and Changho Choi^1
1University of Texas Southwestern Medical Center, Dallas, Texas, United States

As a potential biomarker for clinical diagnosis and prognosis, in vivo 2HG detection in IDH mutated glioma patients with high specificity is important. Due to the extensively overlaps between 2HG signal at 2.25 ppm and GABA signal at 2.28 ppm, the estimation of 2HG is elusive when 2HG concentration is low (< 3mM). Here we present in vivo 2HG measurements without considerable GABA contamination achieved by 2HG optimized triple-refocusing at 3T.

Andreas Boss¹, Andor Veltien¹, and Arend Heerschap^1
1Radiology and Nuclear Medicine, Radboudumc, Nijmegen, Gelderland, Netherlands

We investigated the feasibility to assess hepatic glycogen turnover in mice by in vivo ¹³C-MRS. For this purpose, mice were infused with [1-¹³C]-labeled glucose (N=2), or galactose (N=3) for 120min, followed by 120min of infusion with the respective unlabeled substrate, while 13C-MR spectra of the liver were recorded throughout the experiment. Glycogen-signals increased in the first, and decreased in the second phase of all experiments indicating simultaneous synthesis and degradation. Turnover (rate of degradation/rate of synthesis) was determined from fitting the kinetics of glycogen to a metabolic model and was estimated to be ~84% with galactose as tracer substrate.

Li An¹, Shizhe Li¹, Maria Ferraris Araneta¹, Christopher Johnson¹, James B Murdoch², and Jun Shen^1
1National Institute of Mental Health, National Institutes of Health, Bethesda, MD, United States, ²Toshiba Medical Research Institute USA, Mayfield Village, OH, United States

In vivo measurement of glutamate (Glu) and glutamine (Gln) turnover can provide valuable information on energy metabolism and neurotransmission in the human brain. Since 7 Tesla proton MRS has been shown to be capable of measuring dynamic changes in Glu and Gln signal strength during intravenously infusion of [U-¹³C₆]glucose, in this work, we evaluated the feasibility of quantifying the time-courses of [4-¹³C]Glu and [4-¹³C]Gln concentrations measured by 7 Tesla ¹H MRS. It was shown that the time-course difference spectra could be fitted very well using a linear combination of a numerically simulated basis set.

Sreenath Pruthviraj Kyathanahally¹ and Roland Kreis^1
1Depts. Radiology and Clinical Research, University Bern, Bern, Switzerland

Presently, the spectral quality in 1H MRS can only be determined after performing the time-consuming part of the exam, i.e. the recording of the water-suppressed spectrum. In clinical routine, there is often no time to re-record a spectrum if it turns out to be of bad quality. Therefore, we have developed a tool to forecast the spectral quality and to judge the adequacy of the achieved shim and proposed number of scans using a single-shot non-water-suppressed spectrum. To test, we acquired in vivo brain spectra and compared the forecast with the actual errors found by LCModel and jMRUI-QUEST.

Ming Lu¹, Xiao-Hong Zhu¹, and Wei Chen^1
1Center for Magnetic Resonance Research, University of Minnesota Medical School, Minneapolis, Minnesota, United States

Simultaneous assessment of cerebral glucose consumption rate (CMR_glc) and TCA cycling rate (V_TCA) is crucial for understanding neuroenergetics under various physiopathological conditions; nevertheless, such measurement was not possible. Recently, we developed a novel in vivo Deuterium (²H) MR (DMR) approach for noninvasively assessing glucose metabolisms in rat brain at 16.4 T. Following a brief injection of deuterated glucose, the dynamic labeling on glucose, glutamate/glutamine (Glx), water and lactate in the brain tissue can be monitored via tracking their well-resolved ²H signals. To quantify metabolic rates, a new kinetic model incorporating glycolysis, TCA cycle and -ketoglutarate/Glx exchange was developed in this study. By least-square fitting of the model with the experimental data obtained from dynamic DMR measurement in rat brains, major metabolic fluxes such as CMR_glc and V_TCA can be determined concurrently. Two different metabolic conditions were examined; increased CMR_glc (0.46 vs. 0.28 µmol/g/min) and V_TCA (0.96 vs. 0.6 µmol/g/min) were found under morphine infusion as compare to the deeper anesthesia of 2% isoflurane, which are consistent with previous in vivo ¹³C or ¹H MRS studies. In summary, we demonstrate that the new DMR approach in combine with the kinetic model described in this work is capable of simultaneously determining CMR_glc and V_TCA with high sensitivity and reliability.