Sandeep Kumar Ganji¹, Ivan E Dimitrov^1,2, Elizabeth A. Maher³, and Changho Choi^1
1Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas, United States, ²Philips Medical Systems, Cleveland, Ohio, United States, ³Internal Medicine and Neurology, University of Texas Southwestern Medical Center, Dallas, Texas, United States

Abnormality of glycine (Gly) concentrations has been reported in several brain disorders using single-voxel localized spectroscopic methods. Spectroscopic imaging of Gly in vivo is challenging due to its low concentrations and the spectral overlap, primarily with myo-inositol. We employed an optimized-TE PRESS-based chemical shift imaging method for glycine imaging. We present phantom validation of the technique and preliminary data from tumor patients together with single-voxel data for comparison. The concentration maps of metabolites are also presented.

Bu S Park¹, M J Lizak², Y Xiang¹, and J Shen^1
1National Institute of Mental Health (NIMH), NIH, Bethesda, MD, United States, ²National Institute of Neurological Disorders and Stroke (NINDS), NIH, Bethesda, MD, United States

Adiabatic pulses are widely used for spatial localization in MR spectroscopy because of their high immunity to RF inhomogeneity and excellent slice profiles. Since non-rectangular volume is often preferred in localized spectroscopy, here we optimized and experimentally tested a scheme that uses a time-varying gradient orthogonal to a stationary slice-selection gradient to generate slices with nonparallel boundaries.

Vincent Oltman Boer¹, Dennis W.J. Klomp¹, Christoph Juchem², Peter R Luijten¹, and Robin A de Graaf^2
1Radiology, UMC Utrecht, Utrecht, Utrecht, Netherlands, ²MR Research Center, Yale University, New Haven, Conneticut, United States

Multi-slice MRSI of the human brain at ultra high field is challenging due to both static field inhomogeneity, spatial B1 variations and SAR limits. In this work it is shown how a low-power water and lipid suppression can be combined with pulse acquire-MRSI localization to generate a high SNR multi-slice MRSI sequence for high field. Steady state water suppression, RF shimmed lipid suppression and dynamic B0 and B1 shim updating were used to improve spectral quality in all slices.

Yoshitaka Bito¹, Yuko Kawai², Koji Hirata¹, Toshihiko Ebisu³, Toru Shirai¹, Satoshi Hirata¹, Yoshihisa Soutome¹, Hisaaki Ochi¹, Masahiro Umeda², Toshihiro Higuchi⁴, and Chuzo Tanaka^4
1Central Research Laboratory, Hitachi, Ltd., Kokubunji-shi, Tokyo, Japan, ²Medical Informatics, Meiji University of Integrative Medicine, Kyoto, Japan, ³Neurosurgery, Nantan General Hospital, Kyoto, Japan, ⁴Neurosurgery, Meiji University of Integrative Medicine, Kyoto, Japan

A diffusion-weighted echo-planar spectroscopic imaging with a pair of bipolar diffusion gradients (DW-EPSI with BPGs) was applied to acquire apparent diffusion coefficient (ADC) changes of N-acetylaspartate (NAA) after a right middle cerebral artery occlusion (MCAO) in rat brains. Acquired changes in ADC maps of NAA after MCAO were analyzed by using Gaussian mixture distribution, which can handle many spatial pixels acquired simultaneously by diffusion-weighted spectroscopic imaging. It is shown that DW-EPSI with BPGs is effective for investigating spatially varying ADC changes of metabolites and that this technique may be useful for understanding intra-cellular dynamics of neurons by using NAA as a probe.

Malte Frederick Alf^1,2, Hongxia Lei^1,3, Carole Berthet⁴, Lorenz Hirt⁴, Rolf Gruetter^1,3, and Vladimir Mlynárik^1
1Laboratory of Functional and Metabolic Imaging, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland, ²Institute of Pharmaceutical Sciences, ETH Zürich, Zürich, Switzerland, ³Department of Radiology, University of Lausanne, ⁴Department of Clinical Neuroscience, Centre Hospitalier Universitaire Vaudois

We developed a ¹H-MRSI protocol on a 14.1T magnet to investigate the localization of changes in the mouse neurochemical profile after 30 minutes of transient ischemia (MCAO model). Maps with 1.4 microliter effective resolution were acquired, including e.g. separate glutamate and glutamine and the, to our knowledge, first in vivo mapping of GABA and glutathione. Metabolite acquisition time was 45 minutes. Lactate and NAA concentration changed in core and penumbra; cholines and glutathione in the entire MCA-territory. Glutamine was elevated in ischemic striatum and cortex until 8h/24h after reperfusion respectively, indicating differences in excitotoxic effects and secondary energy failure.

Sairam Geethanath¹, Hyeon-Man Baek², Sandeep K Ganji^2,3, Yao Ding³, Robert D Sims⁴, Changho Choi^2,4, and Vikram D Kodibagkar^1,4
1Joint graduate program in biomedical engineering, UT Arlington and UT Southwestern Medical Center, Dallas, Texas, United States, ²Advanced Imaging Research Center, UT Southwestern Medical Center, ³Graduate program in radiological sciences, UT Southwestern Medical Center, ⁴Radiology, UT Southwestern Medical Center

MRSI has been shown to provide valuable metabolic information critical for cancer prognosis. However, the long acquisition time associated with multidimensional MRSI is a barrier for translation of this technology to the clinic. A novel approach to reduce acquisition time of MRSI has been proposed through the application of compressive sensing. An application of such a reconstruction method has been performed for 1H MRSI of in- vitro brain phantom, in vivo brain (normal, cancer), and prostate cancer MRSI data. The results of reconstruction indicate a significant potential to reduce acquisition times for such studies by 80%.

Anna Andreychenko¹, Vincent O. Boer¹, Jannie P. Wijnen¹, Catalina Arteaga¹, Peter Luijten¹, and Dennis W.J. Klomp^1
1University Medical Center Utrecht, Utrecht, Utrecht, Netherlands

Spectral editing techniques rely on subtraction of two in vivo MR spectra and, therefore, are prone to artefacts. Here, we implemented and performed an accurate and efficient spectral editing of the 3 ppm GABA resonance in-vivo in the human brain at 7 T, utilizing two editing MEGA pulses in a semi-LASER localization sequence with a minimal chemical shift displacement error. The total scan time was ~4 min. High efficiency of this MEGA-sLASER editing technique preserves 3 ppm GABA resonance in the edited spectrum even obtained with an echo time of 222 ms that allowed us to estimate the T2 relaxation time of GABA.

Ovidiu Cristian Andronesi¹, Borjan A. Gagoski², Elfar Adalsteinsson², and Gregory A. Sorensen^1
1Martinos Center for Biomedical Imaging, Radiology Department, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, United States, ²Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA, United States

The overlap of spectra in magnetic resonance spectroscopy limits the unambiguous identification and quantification of metabolites. Novel correlation chemical shift imaging sequences using optimized low power adiabatic excitation and fast spiral spatial encoding are demonstrated on 3T clinical scanners for two-dimensional COSY (Correlation Spectroscopy) and TOCSY (Total Correlation Spectroscopy) experiments. These methods could reveal metabolites that are otherwise obscured in 1D spectra. To date there has been limited progress reported towards a feasible and robust multivoxel COSY. TOCSY imaging is shown for the first time in this work. Results on phantoms, volunteers and patients with brain tumors are presented.

Aaron T Hess¹, André J.W. van der Kouwe², and Ernesta M. Meintjes^1
1MRC/UCT Medical Imaging Research Unit, Human Biology, University of Cape Town, Cape Town, South Africa, ²Radiology, Massachusetts General Hospital, Boston, MA, United States

In a single voxel spectroscopy scan voluntary and physiologic movement can induce frequency and phase variations between consecutive FIDs. These variations lead to destructive averaging and line broadening. We present a technique to robustly detect the frequency of each FID by using its spectral cross-correlation with a simulated spectrum. Further we recombined them in a phase-insensitive manner using a set of complex weights calculated from singular value decomposition. We demonstrate the spectral quality improvement using this method from a scan where the subject was particularly restless.

Zenon Starcuk jr.¹, Jana Starcukova¹, and Zenon Starcuk^1
1Magnetic Resonance and Bioinformatics, Institute of Scientific Instruments, Academy of Sciences of the Czech Republic, Brno, Czech Republic

Short VAPOR-like water suppression sequences have been shown feasible without sacrificing B1 and T1 insensitivity and exhibiting improved excitation profiles. The same construction principle, i.e. optimization of flip angles and pulse durations of chemical-shift selective pulses interleaved with fixed short delays, is proposed to be applied to fat suppression as well. Independently optimized water- and fat-presaturation sequences are superimposed into a series of customized dual-band presaturation pulses, followed by B1-insensitive inversion and a spin-echo localization module. The reduced length and improved robustness of such a sequence may improve quantifiability and suit the needs of spectroscopic imaging.