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Rong Guo^1,2, Yibo Zhao^2,3, Yudu Li^2,4, Chao Ma⁵, Wen Jin^2,3, Yao Li⁶, Georges El Fakhri⁵, Brad Sutton^2,3,4,7,8, and Zhi-Pei Liang^2,3,4
1Siemens Medical Solutions USA, Inc., Urbana, IL, United States, ²Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL, United States, ³Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, United States, ⁴National Center for Supercomputing Applications, University of Illinois at Urbana-Champaign, Urbana, IL, United States, ⁵Gordon Center for Medical Imaging, Department of Radiology, Massachusetts General Hospital, Boston, MA, United States, ⁶School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China, ⁷Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, IL, United States, ⁸Carle Illinois College of Medicine, University of Illinois at Urbana-Champaign, Urbana, IL, United States

Keywords: Spectroscopy, Spectroscopy

High-resolution mapping of GABA in the brain has long been desired by the neuroscience community. But it is still challenging due to several long-standing technical obstacles including low SNR, long scan time, and spectral overlapping. This work proposes an MRSI method integrating multi-slab EPSI acquisition, MEGA spectral editing, and subspace modeling to overcome these difficulties, successfully achieving 3D GABA and metabolite mapping (at 3.0×3.0×4.0 mm³ nominal resolution) in a 12-minute scan time.

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Zepeng Wang^1,2, Yahang Li^1,2, and Fan Lam^1,2
1Bioengineering, University of Illinois at Urbana-Champaign, Champaign, IL, United States, ²Beckman Institute for Advanced Science and Technology, Urbana, IL, United States

Keywords: Spectroscopy, Quantitative Imaging

J-resolved MRSI is a powerful molecular imaging tool for measuring brain metabolites, neurotransmitters and other important biophysical parameters. The inherent SNR challenge of MRSI and prolonged scan time for multi-TE data limit the imaging resolution. This work presents a brand-new capability of whole-brain multiparametric, quantitative MRSI, by integrating a fast-scanning J-resolved MRSI sequence with SNR-efficient multi-band excitation, task-specific experiment designs, subspace imaging and optimized parameter estimation. Experimental studies and initial validation were performed to demonstrate this capability for high-resolution metabolite, neurotransmitter and metabolite T2 mapping from a single scan.

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Hidenori Takeshima¹, Shuki Maruyama², and Masao Yui^3
1Imaging Modality Group, Advanced Technology Research Department, Research and Development Center, Canon Medical Systems Corporation, Kanagawa, Japan, ²Imaging Modality Group, Advanced Technology Research Department, Research and Development Center, Canon Medical Systems Corporation, Tochigi, Japan, ³Research and Development Center, Canon Medical Systems Corporation, Tochigi, Japan

Keywords: Pulse Sequence Design, Spectroscopy

In this abstract, a spectral editing method using MEGA-PRESS with conditional frequency-selective saturation pulses is proposed. The proposed method used additional frequency-selective saturation blocks before the excitation block. The saturation pulses were activated only when the MEGA pulses were inactive. When saturation pulses were activated, the sequence acted as the conventional MEGA-PRESS whose editing pulses were inactive except that the passband of the saturation pulse was not excited. Spectrum reconstruction for the proposed method was same as that for the conventional MEGA-PRESS. Experimental results showed that the proposed method selectively extracted J-coupled signals with all frequencies.

Mark Mikkelsen¹, Ralph Noeske², and Dikoma Shungu^1
1Department of Radiology, Weill Cornell Medicine, New York, NY, United States, ²GE Healthcare, Berlin, Germany

Keywords: Spectroscopy, Spectroscopy, Reproducibility

Multi-metabolite spectral-edited MRS enables the efficient detection of multiple low-concentration metabolites. Two such approaches, HERMES and HERCULES, directly edit two or more metabolites in a single scan. However, the reproducibility of these techniques has yet to be fully established. This study investigated PRESS- and sLASER-localized HERMES and HERCULES test-retest reliability, with the additional aim of demonstrating that sLASER localization is the better of the two sequences for obtaining reproducible measurements. Overall, the test-retest reliability of sLASER was found to be higher than that of PRESS.

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Zeinab Eftekhari^1,2,3, Thomas B Shaw^1,4,5, Jin Jin^2,6, Kieran O'Brien⁶, Gary Cowin¹, Dinesh K Deelchand⁷, Robert Henderson^5,8, Frederik Steyn^5,8, Sicong Tu⁹, Wolfgang Bogner¹⁰, and Markus Barth^1,2,4
1Centre for Advanced Imaging, The University of Queensland, Brisbane, Australia, ²ARC Training Centre for Innovation in Biomedical Imaging Technology, The University of Queensland, Brisbane, Australia, ³Queensland Brain Institute, The University of Queensland, Brisbane, Australia, ⁴School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, Australia, ⁵Neurology Department, Royal Brisbane and Women’s Hospital, Brisbane, Australia, ⁶Siemens Healthcare Pty Ltd, Brisbane, Australia, ⁷Centre for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, MN, United States, ⁸School of Medicine, The University of Queensland, Brisbane, Australia, ⁹Brain and Mind Centre, The University of Sydney, Sydney, Australia, ¹⁰High-field MR Centre, Department of Biomedical Imaging and Image-guided Therapy, Medical University of Vienna, Vienna, Austria

Keywords: Spectroscopy, Spectroscopy, High-Field MRI, Magnetic Resonance Spectroscopy

Magnetic Resonance Spectroscopy (MRS) can offer a unique, non-invasive tool for measuring the neurochemicals in the brain in vivo. This technique may be useful for studying the ratio of metabolites in both health and disease, including in Amyotrophic Lateral Sclerosis (ALS), where differing neuronal populations of the motor cortex are impacted. This study aimed to develop a 7T MRS protocol for ALS patients and measured metabolite ratios in the upper and lower limb regions of the motor cortex at 7T in controls and in ALS. This has the potential to improve progression monitoring and diagnostic certainty in early-stage disease.

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Zoona Javed^1,2, Gary V Martinez³, Marta Mulero-Acevedo^1,4,5, Ana Paula Candiota^1,4,5, Carles Arús ^1,4,5, Miquel Cabañas Egaña^2,4, and Silvia Lope-Piedrafita^2,4
1Departament de Bioquímica i Biologia Molecular, Universitat Autònoma de Barcelona, Cerdanyola del Valles, Spain, ²Servei de Ressonància Magnètica Nuclear, Universitat Autonoma de Barcelona, Cerdanyola del Valles, Spain, ³Department of Imaging Physics,, The University of Texas M.D. Anderson Cancer Center, Houston, TX, United States, ⁴Centro de Investigación Biomédica en Red en Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), Cerdanyola del Valles, Spain, ⁵Institut de Biotecnologia i de Biomedicina (IBB), Universitat Autònoma de Barcelona, Cerdanyola del Valles, Spain

Keywords: Spectroscopy, Cancer, Brain Tumor

MRSI-based nosological images have been previously applied to monitor therapy response in a murine model of GL261 glioblastoma using a commercially available MRSI-PRESS sequence. Due to the heterogeneous nature of glioblastomas, increasing spatial resolution could provide additional insight into changes related to therapy response. The in-house implementation of the MRSI-semi-LASER sequence, using weighted acquisition, has allowed us a 20% slice thickness reduction without losing relevant spectral quality. Moreover, different k-space sampling strategies have been evaluated showing significant SNR increase with elliptical sampling, which may allow further increase in the spatial resolution or reduction in the total experimental time.

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Pandichelvam Veeraiah^1,2, Rick Voncken¹, Kim Brouwers^1,3, Julian Mevenkamp³, Job van den Hurk^1,4, Joachim E Wildberger³, and Vera B Schrauwen-Hinderling^3,5,6
1Scannexus (Ultra-High Field Imaging Center), Maastricht, Netherlands, ²Faculty of Health Medicine and Life sciences (FHML), Maastricht University, Maastricht, Netherlands, ³Department of Radiology and Nuclear Medicine, Maastricht University Medical Center (MUMC), Maastricht, Netherlands, ⁴Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, Maastricht, Netherlands, ⁵Nutrition & Movement Sciences, Maastricht University, Maastricht, Netherlands, ⁶German Diabetes Center, Dusseldorf, Germany

Keywords: Spectroscopy, Muscle, Ultra-high field MRS, proton MR spectroscopy, Muscle

Long echo time ¹H-MRS has been used to determine in vivo acetylcarnitine (ACCT) concentrations in the skeletal muscle. At ultra-high field (UHF), STEAM-based ¹H-MRS was used for this purpose, in combination with a knee birdcage coil. However, STEAM suffers from an inherent 50% signal loss and a knee coil often does not fit around the upper leg in obese volunteers. Here, we demonstrated that sLASER, in combination with a surface coil, provides high signal-to-noise ratio (SNR) and can be used as an alternative method at 7T to detect physiologically low ACCT concentrations at rest in both lean and obese volunteers. 

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Limin Zhou¹, Keith Hulsey¹, Durga Udayakumar^1,2, Andrea J. Wiethoff³, and Ananth J. Madhuranthakam^1,2
1Department of Radiology, University of Texas Southwestern Medical Center, DALLAS, TX, United States, ²Advanced Imaging Research Center, University of Texas Southwestern Medical Center, DALLAS, TX, United States, ³Novartis Institutes for BioMedical Research, Cambridge, MA, United States

Keywords: Spectroscopy, Kidney, Phosphorous (31P) MR spectroscopy (MRS), healthy volunteers

Phosphorous (³¹P) MR spectroscopy (MRS) can measure high energy phosphate metabolism non-invasively in vivo, which can provide metabolic insights into kidney pathophysiology. However, obtaining spectra from healthy volunteers for reference is challenging. In this study, we investigate the feasibility of localized ³¹P MRS in kidneys of healthy volunteers with a 3T clinical MR scanner. ³¹P spectra were successfully obtained in 10 healthy volunteers with metabolite ratio calculated to provide information about the energy metabolism.

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Jabrane Karkouri¹, Lieke van den Wildenberg², Bobby Runderkamp³, Jeanine Prompers², Paolo Cecchi⁴, Michela Tosetti^4,5, Dennis Klomp², and Christopher T. Rodgers^1
1University of Cambridge, Cambridge, United Kingdom, ²Center for Image Sciences, University Medical Center Utrecht, Utrecht, Netherlands, ³Department of Radiology and Nuclear Medicine, Amsterdam UMC, Amsterdam, Netherlands, ⁴IMAGO7 Research Foundation, Pisa, Italy, ⁵Laboratory of Medical Physics and Magnetic Resonance, IRCCS Stella Maris, Pisa, Italy

Keywords: Spectroscopy, Non-Proton

We present preliminary baseline results from three-vendor 7 T MRSI for applications on liver ³¹P MRS. Liver scans were performed on 21 healthy volunteers, at 4 sites and 3 different 7T MR scanner platforms.  Data were analysed using a new Matlab pipeline combining the best methods from our labs. This pipeline is operator independent and we report here the liver metabolites as ratios of PME/PDE and Pi/ATP concentrations. The cross-site average PME/PDE was 0.63 ± 0.12, and the cross-site average Pi/ATP was 0.76 ± 0.11. This compares favourably with literature reports [Purvis et. al., 2017].  

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Lukas Hingerl¹, Bernhard Strasser¹, Gilbert Hangel^1,2, Stanislav Motyka¹, Fabian Niess¹, Eva Niess¹, Alexandra Lipka¹, Dario Goranovic¹, Philipp Lazen¹, Stephan Gruber¹, Siegfried Trattnig^1,3, and Wolfgang Bogner^1
1Department of Biomedical Imaging and Image-guided Therapy, Radiology and Nuclear Medicine, Medical University of Vienna, HFMR Centre, Vienna, Austria, ²Department of Neurosurgery, Medical University of Vienna, Vienna, Austria, ³Institute for Clinical Molecular MRI in Musculoskeletal System, Karl Landsteiner Society, Vienna, Austria

Keywords: Spectroscopy, Spectroscopy, Lipid Fat Suppression Removal

We present an elegant and easy to implement method for MRI and CSI steady-state sequences to remove or suppress lipids or other components with short transverse relaxation times by neither introducing additional pulses nor hardware and by just altering the excitation pulse phase.

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Yizun Wang^1,2, Stanislav S. Rubakhin^1,2,3, and Fan Lam^1,2,4
1Department of Bioengineering, 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, ³Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL, United States, ⁴Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, United States

Keywords: Spectroscopy, Data Acquisition, MRSI Data Processing

Ultrahigh-field systems offer sensitivity and specificity advantages for metabolite mapping using MRSI. We present here a method that integrates relaxation enhancement acquisition, a unique strategy leveraging higher fields, and subspace imaging, for high-resolution 1H-MRSI at a 9.4 T system. Both in vitro and in vivo experiments have been performed to demonstrate the feasibility of the proposed method. We are able to achieve significantly enhanced SNR compared to no relaxation enhancement and produce high-quality spatially-resolved spectra and high-resolution metabolite images using subspace imaging with 0.6×0.6×2 mm³ nominal resolution in 18 minutes or 1×1×2 mm³ in 10 minutes. 

Dario Goranovic¹, Stanislav Motyka¹, Bernhard Strasser¹, Paul Weiser², Georg Langs², and Wolfgang Bogner^1
1High Field MR Center - Department of Biomedical Imaging and Image-Guided Therapy, Medical University of Vienna, Vienna, Austria, ²Computational Imaging Research Lab - Department of Biomedical Imaging and Image-guided Therapy, Medical University of Vienna, Vienna, Austria

Keywords: Spectroscopy, Brain

The abstract investigates the possibilities of using convolutional neural networks for enhanced and robust spectral quantification of simulated 7T FID-MRSI brain spectra. The proposed network architecture predicts wavelet parameters for baseline correction, as well as spectral parameters and metabolite amplitudes for spectral reconstruction. The potential reduction in quantification times could thus mitigate some disadvantages of current MRSI processing techniques.

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Yibo Zhao^1,2, Rong Guo^1,3, Yudu Li^1,4, Wen Jin^1,2, Yao Li⁵, Jie Luo⁵, and Zhi-Pei Liang^1,2
1Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL, United States, ²Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, United States, ³Siemens Medical Solutions USA, Inc., Urbana, IL, United States, ⁴National Center for Supercomputing Applications, University of Illinois at Urbana-Champaign, Urbana, IL, United States, ⁵School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China

Keywords: Spectroscopy, Relaxometry

In MRSI studies, T1 values of metabolites are desirable for correcting relaxation and B1 inhomogeneity effects, and for evaluating microenvironmental changes in pathological conditions. Current metabolite T1 mapping has been limited to single-voxel or single-slice experiments due to SNR and imaging time constraints. In this work, we demonstrated the feasibility of 3D high-resolution T1 mapping of brain metabolites using a novel data acquisition and processing method featuring physics-based low-rank tensor modelling and FID acquisitions. The proposed method has been validated using phantom and in vivo data, producing encouraging results.

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Bernhard Strasser¹, Ovidiu C Andronesi², Lukas Hingerl¹, Stanislav Motyka¹, Siegfried Trattnig¹, Wolfgang Bogner¹, and Antoine Klauser^3
1Department of Biomedical Imaging and Image-guided Therapy, Medical University of Vienna, Vienna, Austria, ²Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, United States, ³Department of Radiology and Medical Informatics, University of Geneva, Geneva, Switzerland

Keywords: Spectroscopy, New Trajectories & Spatial Encoding Methods

We show the feasibility of compressed sensing for MRSI using concentric ring trajectories. Four volunteers (three for 2D- and one for 3D-MRSI) were measured in about 9 minutes (2D-MRSI), and 14 minutes (3D-MRSI) using an FID-based MRSI sequence at 7 T. An iterative compressed sensing reconstruction including coil sensitivities and a total general variation spatial regularization was performed with retrospective undersampling factors of 1.5, 2.0 and 2.9. RMSE values were below 22 % and SSIM values above 0.8 for medium accelerations below 2.9 in the 2D case. The metabolic maps and spectra are similar to the gold standard without acceleration.

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Onur Ozyurt¹, Diana Rotaru², Nicholas Farley³, Zoe Kourtzi², Guy Williams¹, and Uzay Emrah Emir^3,4
1Wolfson Brain Imaging Center, Department of Clinical Neurosciences, University of Cambridge, Cambridge, United Kingdom, ²Department of Psychology, University of Cambridge, Cambridge, United Kingdom, ³School of Health Sciences, Purdue University, West Lafayette, IN, United States, ⁴Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN, United States

Keywords: Spectroscopy, Brain, GABA, Glutamate, MRSI

High-resolution neurochemical mapping using 2D zoom or reduced field of view (rFOV) magnetic resonance spectroscopy (MRSI) enables the high-resolution metabolic assessment of brain regions that is difficult to probe with standard MRSI sequences. To our knowledge this is the first study to have demonstrated the application of zoom MRSI at 7T for GABA and glutamate mapping.  

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Marc Jonuscheit^1,2, Benedict Korzekwa^1,2, Yuliya Kupriyanova^1,2, Julian Mevenkamp³, Michael Roden^1,2,4, and Vera B. Schrauwen-Hinderling^1,2,3
1Institute for Clinical Diabetology, German Diabetes Center, Leibniz Institute for Diabetes Research at Heinrich Heine University, Düsseldorf, Germany, ²German Center for Diabetes Research (DZD e.V.), München-Neuherberg, Germany, ³Department of Radiology and Nuclear Medicine, Maastricht University Medical Center, Maastricht, Netherlands, ⁴Department of Endocrinology and Diabetology, Medical Faculty, Heinrich Heine University, Düsseldorf, Germany

Keywords: Spectroscopy, Spectroscopy, 13C-MRS, Quadrature Coil, Absolute Quantification

We determined day-to-day variation and intra-session reproducibility of ¹³C-MRS based hepatic glycogen quantification by phantom replacement, using a custom-created rigid quadrature surface coil and determining the C1-glycogen signal in eight healthy volunteers. The quadrature coil allows measurements at high distances, which can be important for applications in overweight and obese people. Coefficients of variation were less than 22% for day-to-day variation and less than 9% for intra-session reproducibility (with repositioning of volunteer). In conclusion, our ¹³C-MRS protocol yields robust absolute concentrations of the hepatic glycogen and the day-to-day variation assessed here can be the basis for sample size calculations.

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Guglielmo Genovese¹ and Małgorzata Marjańska^1
1Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States

Keywords: Spectroscopy, Data Processing, Diffusion-Weighted MRS, High Field (3T), Denoising, Low-Rank Model

Diffusion-weighted (DW) MRS is a useful tool for detecting microstructural changes linked to neurological diseases. However, DW-MRS suffers from low signal-to-noise ratio, which makes human application extremely difficult. To overcome this issue, a denoising algorithm based on low-rank approximation was recently utilized. Here, effects of the application of low-rank based denoising algorithm to DW-MRS data are described based on synthetic data. Severely artifactually low group SDs for the apparent diffusion coefficients (ADCs) of all metabolites and biased mean ADC values were observed after denoising. These findings suggest that low-rank approximations are detrimental to a reliable quantification of ADCs of metabolites.

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Angeliki Stamatelatou¹, Rudy Rizzo^2,3, Kadir Simsek⁴, Jack J.A. van Asten¹, Arend Heerschap¹, Tom WJ Scheenen¹, and Roland Kreis^2,3
1Department of Medical Imaging, Radboud University Medical Center, Nijmegen, Netherlands, ²Magnetic Resonance Methodology, Institute of Diagnostic and Interventional Neuroradiology, University of Bern, Bern, Switzerland, ³Translational Imaging Center, sitem-insel, Bern, Switzerland, ⁴Cardiff University Brain Research Imaging Centre (CUBRIC), School of Psychology, Cardiff University, Cardiff, United Kingdom

Keywords: Spectroscopy, Diffusion/other diffusion imaging techniques

Diffusion-weighted Magnetic Resonance Spectroscopy (DW-MRS) is ideally suited to explore complex microstructure with metabolites selectively distributed in different subspaces. So far this technique was applied in brain and muscle only. In this work, we explored DW-MRS for the first time in the prostate, an organ, with potentially more motion problems. Thus, dedicated acquisition and post-processing techniques were used including the measurement of water next to that of metabolites for corrections. ADC values of citrate, total choline, total creatine and spermine were estimated and evaluated according to the compartmental structure of the prostate indicating hindered metabolite diffusion in the luminal space.

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Michal Považan¹, Mads Just Madsen¹, and Leo Tomasevic^1
1Danish Research Centre for Magnetic Resonance, Hvidovre, Denmark

Keywords: Spectroscopy, Neuroscience

The neurochemical substrate of the measures observed with transcranial magnetic stimulation remains unclear. MR spectroscopy may provide valuable insights into understanding the synaptic GABAergic and glutamatergic activity, however studies comparing these methods haven’t provided an adequate explanation. We aimed to compare GABA and glutamate concentrations with short-interval afferent inhibition measured with TMS. We found positive correlation between the amount of inhibition and tonic GABA levels, however this finding needs to be carefully scrutinized.

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Alireza Abaei¹, Dinesh K Deelchand ², Stefano Antonucci³, Jelena Scekic-Zahirovic³, Florian olde Heuvel³, Francesco Roselli³, and Volker Rasche^4
1Ulm University, Ulm, Germany, ²Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States, ³German Center for Neurodegenerative Diseases (DZNE), Ulm, Germany, ⁴Core Facility Small Animal Imaging (CF-SANI), University of Ulm, Ulm, Germany

Keywords: Spectroscopy, Spectroscopy, in vivo ex vivo MRS

The goal of this study is to demonstrate the feasibility and reliability of metabolite characterization by MR spectroscopy ex vivo in order to maximize the information obtained from a single brain specimen, without the limitations such as scanning time, degraded MRI quality due to intervening tissue and motion artifacts.  We demonstrate that ex-vivo spectroscopy obtained after rapid PBS/PFA perfusion is strongly correlated with the MR spectrum previously acquired in the same animal but in vivo but distinct abnormalities due to hypoxia and incomplete fixation do appear; the quality of the spectrum quickly degrades upon longer fixation times.