Adam Berrington¹, Michal Povazan², Christopher Mirfin¹, Stephen Bawden¹, Richard Bowtell¹, and Penny Gowland^1
1Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham, Nottingham, United Kingdom, ²Russel H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School Of Medicine, Baltimore, MD, United States

RF shimming can increase B₁⁺ availability, which is critical for robust localised MR spectroscopy at ultra-high field. Shim calibration is performed on a region-wise basis and is, therefore, tim­­­e consuming. Additionally, B₁ distributions become difficult to predict. Recent work has shown that ‘universal’ pulses can be generated offline – avoiding the need for calibration. Here, we determine static calibration-free RF shims, optimised over 5 heads, for 3 different brain regions. B₁⁺ availability using calibration-free shims was significantly higher than quadrature and comparable to tailored shimming. High quality spectra were also obtained from 3 regions with the calibration-free shims.

Kadir Şimşek¹, André Döring¹, André Pampel², Harald E. Möller², and Roland Kreis^1
1Department of Radiology and Biomedical Research, University of Bern, Bern, Switzerland, ²Max-Planck Institute For Human Cognitive and Brain Sciences, Leipzig, Germany

Diffusion-weighted MRS was successfully implemented on a 3T Connectom system reaching b-values of 25 ms/um2 at a short TE of 30 ms and a moderate TM of 65 ms. Motion-compensation based on the water peak was found feasible up to the highest b-value and can be supplemented by scaling to the macromolecule peak intensity at 0.9 ppm. Non-Gaussian diffusion behavior was detected for multiple metabolites and was modeled with biexponential and kurtosis representations. In addition, a macromolecular spectrum could be determined by diffusion weighting and simultaneous modeling, which can now be used for quantification in clinical short TE MRS.

Philipp Moser¹, Korbinian Eckstein¹, Lukas Hingerl¹, Michael Weber¹, Stanislav Motyka¹, Bernhard Strasser^1,2, Andre van der Kouwe³, Simon Robinson¹, Siegfried Trattnig^1,4, and Wolfgang Bogner^1
1High Field MR Centre, Department of Biomedical Imaging and Image-guided Therapy, Medical University of Vienna, Vienna, Austria, ²Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Harvard Medical School, Massachusetts General Hospital, Vienna, MA, United States, ³Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology,, Harvard Medical School, Massachusetts General Hospital, Boston, MA, United States, ⁴Christian Doppler Laboratory for Clinical Molecular MR Imaging, Vienna, Austria

We demonstrate the combination of 3D free induction decay proton MR spectroscopic imaging and spatial encoding via concentric-ring trajectories at 3T. To improve the reliability a well as the temporal stability, single-echo, imaging-based volumetric navigators for real-time motion/shim-correction were additionally integrated. All intra-subject coefficients of variation and most of the inter-subject coefficients of variation obtained with motion/shim-correction were lower (i.e., better) than without and resulted in higher SNRs and lower CRLBs.

Yibo Zhao^1,2, Yudu Li^1,2, Jiahui Xiong^1,2, Rong Guo^1,2, Yao Li^3,4, and Zhi-Pei Liang^1,2
1Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, United States, ²Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL, United States, ³School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China, ⁴Med-X Research Institute, Shanghai Jiao Tong University, Shanghai, China

J-resolved MRSI is a powerful tool for separating overlapping resonances in conventional MRSI, which is especially useful for mapping neurotransmitters like γ-aminobutyric acid and glutamate. A major practical limitation of J-resolved MRSI lies in its long data acquisition time required to sample the high-dimensional data space using spin-echo-based sequences. In this work, we present a novel hybrid FID/SE data acquisition scheme to accelerate J-resolved MRSI. The proposed method has been validated using phantom and in vivo experimental data, producing high-quality 3D spatial maps of brain metabolites and neurotransmitters within clinically feasible time.

Chathura Kumaragamage¹, Henk M De Feyter¹, Peter B Brown¹, Scott McIntyre¹, Terence W Nixon¹, and Robin A de Graaf^1
1Radiology and Biomedical Imaging, Yale University, New Haven, CT, United States

Extracranial lipid contaminants impede the reliable and accurate metabolite quantification with human brain MRSI. Elliptical localization with pulsed second order fields (ECLIPSE) was previously demonstrated for MRSI with inner volume selection (IVS), providing robust lipid suppression with improved elliptical brain coverage relative to a cubical ROI. In this work, alternative ECLIPSE-based OVS and IVS  sequences were developed for human brain MRSI at 4T. Both ECLIPSE methods provide > 100-fold mean lipid suppression for short-TE MRSI. In addition, ECLIPSE-OVS consumes 30% of the power required by a traditional 8-slice OVS method, making ECLIPSE-OVS attractive for high field MRSI.

Diana Rotaru¹, Georg Oeltzschner^2,3, Richard Edden^3,4, and David Lythgoe^1
1Neuroimaging, King's College London, London, United Kingdom, ²Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, MD, United States, ³F. M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, United States, ⁴Radiology and Radiological Science, The Johns Hopkins University School of Medicine,, Baltimore, MD, United States

Advanced spectral editing techniques have focused mainly on GABA and GSH discrimination and detection. HERCULES, unlike all predecessor sequences, delivers a reliable detection method for GABA and GSH, but also for ascorbate, aspartate, 2-hydroxyglutarate, lactate, NAA and NAAG. However, current analysis methods have not been optimized for HERCULES analysis. We investigated simultaneous LCModel fitting of the concatenated sum and difference spectra calculated from HERCULES data. The concatenated (ConCAT) approach enables the use of all available spectral information. Compared to traditional single-spectrum analysis, ConCAT yielded improved results, with lower coefficients of variation obtained for concentration estimates and Cramér-Rao lower bounds.

Karl Landheer¹ and Christoph Juchem^1,2
1Biomedical Engineering, Columbia University, New York, NY, United States, ²Radiology, Columbia University, New York, NY, United States

It has recently been recommended to utilize the minimum echo time for non-editing magnetic resonance spectroscopic experiments. Despite this intuitive recommendation there is no comprehensive and systematic investigation into the choice of echo time across numerous sequences. Here the impact of echo time on the Cramér-Rao lower bounds for 17 different metabolites across the six most commonly used pulse sequences are investigated using simulated spectral shapes, as well as a MEGA-sLASER sequence for GABA quantification. Recommendations are provided for the choice of echo time which will minimize the expected Cramér-Rao lower bound for all metabolites and sequences in question.

Morteza Esmaeili^1,2, Bernhard Strasser¹, Wolfgang Bogner³, Philipp Moser³, Zhe Wang⁴, and Ovidiu C. Andronesi^1
1Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Boston, MA, United States, ²Department of Diagnostic Imaging, Akershus University Hospital, Lørenskog, Norway, ³High-field MR Center, Department of Biomedical Imaging and Image-guided Therapy, Medical University of Vienna, Vienna, Austria, ⁴Siemens Medical Solutions, Charlestown, MA, United States

Metabolic imaging using magnetic resonance spectroscopic imaging (MRSI) provides important biomarkers for brain neurochemistry. We developed a spiral-out-in (SOI) trajectory for human whole-brain MRSI at 7T to take advantage of increased sensitivity and spectral separation at ultra-high field. We hypothesized that spectral-spatial SOI sampling will provide higher signal-to-noise ratio(SNR) compared to spiral-out (SO) sampling by increasing the efficiency of data collection. We acquired data from phantom and six healthy volunteers. Metabolic maps, SNR, Cramér-Rao-Lower-Bounds (CRLB) were evaluated between SO and SOI acquisitions. By more efficient data points collection per repetition time, SOI provided a significant improvement in SNR and CRLB.

Andrew Martin Wright^1,2, Saipavitra Murali Manohar^1,3, and Anke Henning^1,4
1MRZ, Max Planck Institute for Biological Cybernetics, Tuebingen, Germany, ²International Max Planck Research School, University of Tuebingen, Tuebingen, Germany, ³University of Tuebingen, Tuebingen, Germany, ⁴Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX, United States

Quantitative metabolite maps are reported from in vivo results at 9.4T. These maps are produced by quantifying with an internal water reference and utilize a novel T1 correction method applied to each voxel individually. Quantitative results allow cross-vendor and cross-site comparisons of results which may help to understand and characterize a variety neurological diseases.

Alireza Abaei¹, Dinesh K Deelchand², Francesco Roselli³, and Volker Rasche^1
1Core Facility Small Animal Imaging, Ulm University, Medical Center, ulm, Germany, ²Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States, ³German Center for Neurodegenerative Diseases (DZNE), Ulm, Germany

Several pathological conditions affect only a small volume of the cortex (such as the motor cortex in amyotrophic lateral sclerosis) and its characterization in mouse models is made impossible by the interference of normal, nearby cortical tissue. A sub-microlitre preclinical MRS technique was successfully implemented to detect subtle changes of the neurometabolite concentrations in three cortical areas. Employing LASER together with using cryogenically cooled RF coils significantly reduces the acquisition time to enable sub-microlitre MRS acquisition. Our findings demonstrate that neurochemical profiles of individual cortical brain regions can be reliably collected in pre-clinically feasible scan times.

Layla Tabea Riemann¹, Christoph Stefan Aigner¹, Rüdiger Brühl¹, Semiha Aydin¹, Ralf Mekle², Sebastian Schmitter¹, Bernd Ittermann¹, and Ariane Fillmer^1
1Physikalisch-Technische Bundesanstalt (PTB), Braunschweig und Berlin, Germany, ²Center for Stroke Research Berlin, Charité-Universitätsmedizin, Berlin, Germany

In this work, a novel ¹H MR spectroscopy sequence is proposed that provides the advantages of single voxel spectroscopy, such as high spectral bandwidth, a narrower point spread function, shorter measurement time and larger signal-to-noise-ratio, as compared to spectroscopic imaging while exciting more than one voxel. A multi-band adiabatic RF pulse was implemented into a SPECIAL sequence to simultaneously acquire the signal of two disjunct voxels at short echo times. The overlapping signal was decomposed using the SENSE algorithm. The new sequence was validated using a two-compartment phantom and its feasibility for in-vivo application is demonstrated at 7 T.

Maike Hoefemann¹, Raphaela Muri², Stephanie Abgottspon², Johannes Slotboom³, Regula Everts^2,4, Roman Trepp², and Roland Kreis^1
1Departments of Radiology and Biomedical Research, University of Bern, Bern, Switzerland, ²Department of Diabetes, Endocrinology, Clinical Nutrition and Metabolism, Bern University Hospital, University of Bern, Bern, Switzerland, ³Support Center for Advanced Neuroimaging, University Institute of Diagnostic and Interventional Neuroradiology Inselspital, Bern, Switzerland, ⁴Division of Neuropediatrics, Development & Rehabilitation, Pediatric University Hospital, University of Bern, Bern, Switzerland

For the quantification of the low-concentration metabolite phenylalanine (Phe) in patients with phenylketonuria using ¹H magnetic resonance spectroscopy, optimal acquisition parameters and fitting procedures are crucial. Using a large voxel size and short TE helps to increase the signal-to-noise-ratio and allows restriction to a measurement time of 12min. Using the comparison of healthy controls vs. patients affords modeling of the unknown downfield region to develop a robust fitting model. Low CRLB of around 0.004mM proved the good precision of the quantification results, yielding cohort values of 0.019±0.01mM in controls and 0.142±0.02mM in patients.

Andrew Apps¹, Justin Lau^1,2, Jane Ellis¹, Mark Peterzan¹, Moritz Hundertmark¹, Damian Tyler^3,4, Albrecht Ingo Schmid^4,5, Stefan Neubauer⁶, Oliver Rider⁶, Ladislav Valkovic^6,7, and Christopher T Rodgers^8
1Cardiovascular Medicine, University of Oxford, Oxford, United Kingdom, ²Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom, ³Physiology Anatomy and Genetics, University of Oxford, Oxford, United Kingdom, ⁴Oxford Centre for Magentic Resonance, University of Oxford, Oxford, United Kingdom, ⁵Medical University of Vienna, Vienna, Austria, ⁶Oxford Centre for Magnetic Resonance, University of Oxford, Oxford, United Kingdom, ⁷Imaging Methods, Slovak Academy of Sciences, Bratislava, Slovakia, ⁸Clinical Neurosciences, University of Cambridge, Cambridge, United Kingdom

The addition of Pi/PCr quantification adds value over PCr/ATP for the characterisation of myocardial energetics. In defining the chemical shift of the Pi resonance, pH can also be computed. Such measurements however are hampered in 31P MRS  due to the overlapping 2,3-DPG resonance. In harnessing the black blood contrast offered by STEAM, we successfully characterise Pi (and hence myocardial pH) in a cohort of patients with dilated cardiomyopathy. We go on to shown that in these patients (but not controls) Pi/PCr rises significantly during dobutamine stress, a finding that would significantly impair the free energy of ATP hydrolysis during exertion.

Ronald Ouwerkerk¹, Jatin Raj Matta¹, Ahmed Hamimi¹, Aaron M Cypess², Kong Y Chen³, and Ahmed Medhat Gharib^1
1Biomedical and Metabolic Imaging Branch, NIDDK/NIH, Bethesda, MD, United States, ²Translational Physiology Section, Diabetes, Endocrinology, and Obesity Branch, NIDDK/NIH, Bethesda, MD, United States, ³Energy Metabolism Section, Diabetes, Endocrinology, and Obesity Branch, NIDDK/NIH, Bethedsa, MD, United States

Localized 1H-MRS was used to determine relaxation properties of fatty acid (FA) resonances in supraclavicular adipose tissue and distal white adipose tissue (WAT). Blinded to MRS results 18FDG-PETwas used to detect cold activated metabolism to identify active brown adipose tissue (BAT).  Using the T2 of the FA methylene t a cutoff value of 76 ms this T2 can be used to distinguish BAT from distal or supraclavicular WAT with 85% sensitivity and 95% specificity

Natali Naude^1,2,3, Gorane Santamaria^1,2,3, Thomas Lloyd³, Ian Bennett³, Jeremy Khoo³, Peter Malycha^1,3, and Carolyn Mountford^1,2,3
1Translational Research Institute, Brisbane, Australia, ²Queensland University of Technology, Brisbane, Australia, ³Princess Alexandra Hospital, Brisbane, Australia

Breast density is a strong risk factor for breast cancer with a four to six fold increase for those in BI-RADS high density group versus low density group.  The current study acquired MRI and MRS in 65 women at average lifetime risk of developing breast cancer, and found statistically significant differences in various MR-visible lipids and metabolites as well as cholesterol between low and high breast density groups.  Results implicate that increased metabolic activity underlies increased mammographic breast density.  2D COSY offers a non-invasive window into breast tissue chemistry, without the use of gadolinium-based contrast media.