Thomas Kirchner¹, Ariane Fillmer¹, Klaas Paul Pruessmann¹, and Anke Henning^1,2
1Institute for Biomedical Engineering, UZH and ETH Zurich, Zurich, Switzerland, ²Max Planck Institute for Biological Cybernetics, Tuebingen, Germany

Spatial variations in the main magnetic field are a common source of artifacts in brain MRSI. When using overdiscrete target-driven reconstruction of ¹H FID MRSI at 7T, improvements not only in spectral SNR but also in metabolite line width are achieved by performing B₀ correction at a subvoxel level. The mechanisms behind these effects are spatial noise decorrelation and frequency alignment. Additional optimization of the FID acquisition time in conjunction with zero-filling is shown to be largely complementary and allows to further increase SNR enhancement.

Bryan Clifford¹, Chao Ma², Fan Lam¹, and Zhi-Pei Liang^1
1Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, United States, ²Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, IL, United States

We present a post-processing method for the removal of water and lipid signals from 3D ¹H-MRSI data that has limited and sparse coverage of (k, t)-space. Our method extends a recently proposed Union-of-Subspace method to enable the use of support constraints derived from high-resolution 3D anatomical scans. The method is capable of handling 3D data sets with only a limited number of spatial encodes in the slice direction. Experimental results show that the proposed method can effectively remove water and lipid signals from 3D ¹H-MRSI data of the brain. The method is particularly useful for accelerated¹H-MRSI with sparse sampling.

Wei Bian¹, Yan Li¹, Jason C. Crane¹, and Sarah J. Nelson^1
1Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA, United States

Repeatable volume positioning holds the key toward a robust reproducibility study for MRSI. In this study the repeatability of an atlas-based fully automated MRSI positioning method was evaluated. Our results showed that the method was highly reproducible with high percentage of overlap of target volume between serial scans. Also the reproducibility and reliability of metabolite ratios assessed respectively by the coefficient of variance and intraclass correlation coefficient showed no significant difference between intra- and inter-scans. This atlas-based method may provide a standard pipeline for assessing MRSI reproducibility, from the image acquisition to presentation of results on a template image space.

Maryam Vareth^1,2, Li Yan^2,3, Janine Lupo^2,3, and Sarah Nelson^2,3
1UCSF/UCBerkeley Joint Graduate Group in Bioengineering, University of California Berkeley, Berkeley, CA, United States, ²Surbeck Laboratory of Advanced Imaging, Department of Radiology and Biomedical Imaging, CA, United States, ³Radiology and Biomedical Imaging, University of California San Francisco, CA, United States

In this work five of most popular coil combination techniques have been studied and applied to 50 patients with 105 3D-MRSI exams to determine the most robust and accurate algorithm for clinical use.

Claudiu Schirda¹, Tiejun Zhao², Julie Pan¹, and Hoby Hetherington^1
1Radiology, University of Pittsburgh School of Medicine, Pittsburgh, PA, United States, ²Siemens Medical Solutions, Pittsburgh, PA, United States

Fast, high-sensitivity Rosette Spectroscopic Imaging (RSI) with Hadamard encoding is demonstrated in-vivo brain for four 10mm slices, 24x24 matrix, fov=240mm, 8-minute acquisition, with reduced gradient demands (maximum slew rate of 40mT/m/ms and maximum gradient readout of 5mT/m). Spectra for all voxels are processed and metabolites are quantified with an automated processing pipeline using LCModel.

Wolfgang Bogner¹, Bernhard Strasser¹, Michal Povazan¹, Gilbert Hangel¹, Borjan Gagoski², Stephan Gruber¹, Bruce Rosen³, Siegfried Trattnig¹, and Ovidiu C Andronesi^3
1MRCE, Department of Biomedical Imaging and Image-guided Therapy, Medical University Vienna, Vienna, Vienna, Austria, ²Fetal-Neonatal Neuroimaging & Developmental Science Center, Boston Children's Hospital, Harvard Medical School, Boston, MA, United States, ³Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, United States

The reduced form of Glutathione (GSH) is the most important intra-cellular antioxidant that prevents cellular damage caused by free radicals and peroxides. GSH can be measured via 1H-MR spectroscopy (MRS), but its low concentration and spectral overlap with signals from more abundant compounds require special editing techniques such as MEGA-PRESS. Previous reports were mostly limited to single-voxel, a few reported single-slice-MRS imaging. Here we introduce robust 3D mapping of brain GSH levels via a MEGA-edited, spiral-accelerated, real-time motion-&B0-corrected fully-adiabatic LASER localization sequence. As an excellent marker for oxidative stress, GSH imaging could be a powerful non-invasive imaging tool for the investigation of many neurological disorders.

Li An¹ and Jun Shen^1
1National Institute of Mental Health, National Institutes of Health, Bethesda, MD, United States

Image-guided compartmental localization allows the extraction of spectra or other tissue parameters from anatomical compartments with irregularly shaped boundaries using very few scans. Here we propose a novel method to take into consideration of biologically inhomogeneous signal distribution within each compartment. We first subdivide each compartment into multiple smaller subcompartments to capture intra-compartment heterogeneous signal distribution and then use compressed sensing for regularization. Application of this new method to single-shot separation of MRS signals from stroke and normal tissue compartments is demonstrated.

Morteza Esmaeili^1,2, Tone Frost Bathen², Bruce R. Rosen¹, and Ovidiu Cristian Andronesi^1
1Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States, ²Department of Circulation and Medical Imaging, Norwegian University of Science and Technology (NTNU), Trondheim, Norway

Full head proton magnetic resonance spectroscopic imaging (MRSI) is desirable to map metabolites over the entire brain but challenging due to large artifacts created by lipid signals. Hypergeometric dual band pulses have a very sharp passband and when combined with adiabatic spin echo and MEGA editing provide efficient lipid and water suppression for full brain metabolic imaging. Here we show that such a combined approach is robust with respect to B1 inhomogeneity at 3T and is superior to traditional suppression schemes for 3D MRSI of full brain.

Michal Považan¹, Gilbert Hangel¹, Bernhard Strasser¹, Marek Chmelik¹, Stephan Gruber¹, Siegfried Trattnig¹, and Wolfgang Bogner^1
1MRCE, Department of Biomedical Imaging and Image-guided therapy, Medical University Vienna, Vienna, Austria

The 1H ultra-short acquisition delay spectra are characterized by the superposition of signals of metabolites and macromolecules. We have developed a double inversion nulling method to measure macromolecular spectra at 7T with acquisition delay as short as 1.3 ms and very short repetition time (900 ms). Optimal inversion times were simulated and experimentally verified. Macromolecular spectra were acquired from four young healthy volunteers. The spectra did not exhibit any visible difference in inter-subject comparison. In addition, four conventional 1H MRSI datasets without inversion were acquired in healthy subjects and quantified using basis sets with and without incorporated macromolecules.

Chao Ma¹, Fan Lam^1,2, Qiang Ning^1,2, Curtis L. Johnson¹, and Zhi-Pei Liang^1,2
1Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States, ²Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Illinois, United States

SPICE (SPectroscopic Imaging by exploiting spatiospectral CorrElation) is emerging as a powerful tool for high-resolution spectroscopic imaging of the brain. As voxel size is getting smaller at higher resolution, further improvement of signal-to-noise ratio (SNR) becomes essential, especially with sparse sampling in (k,t)-space. This work presents a novel data acquisition and processing method to enable short-TE SPICE for high-resolution 1H-MRSI of the brain. In vivo experimental results show that the proposed method can achieve 2mm in-plane resolution in good SNR with a TE of 20ms in a 30min scan.