Spectroscopy Methodology for Improved Metabolite Detection
Wednesday 5 May 2010
Room A5 10:30-12:30 Moderators: Malgorzata Marjanska and Douglas L. Rothman

10:30 372.  

GABA Editing at 3T with Macromolecule Suppression:  MEGA-SPECIAL
Jamie Near1, Philip J. Cowen1, Peter Jezzard2
1Department of Psychiatry, University of Oxford, Oxford, OXON, United Kingdom; 2The Centre for Functional Magnetic Resonance Imaging of the Brain, John Radcliffe Hospital, Oxford, OXON, United Kingdom

GABA editing using the MEGA-PRESS technique at 3T results in signal contamination from macromolecules.  We present a modified spectral editing technique called MEGA-SPECIAL, which enables the use of longer, more frequency-selective editing pulses.  This, in turn, enables the use of previously described strategies for the removal of macromolecular contamination.  In-vitro measurements indicate that the newly developed sequence provides improved editing efficiency over MEGA-PRESS, and experiments performed in-vivo confirm that macromolecular suppression is achieved.

10:42 373.  

13C MRS of Frontal Lobe at 3 Tesla  Using a Volume Coil for Stochastic Proton Decoupling
Shizhe Steve Li1, Yang Zhang1, Shumin Wang1, Maria Ferraris Araneta1, Christopher S. Johnson1, Yun Xiang1, Robert B. Innis1, Jun Shen1
National Institutes of Health, Bethesda, MD, United States

13C spectra from the frontal lobe of human brain were acquired for the first time at 3 Tesla. After intravenous infusion of [2-13C]glucose, glutamate, glutamine, and aspartate were detected in the carboxylic/amide carbons region. The RF power deposition was well below the safety guidelines, due to enhanced decoupling efficiency from the volume coil and weak J coupling between proton and carboxylic/amide carbons. The effect of the strong B0 field inhomogeneity in the frontal lobe region was reduced by RF coil arrangement and by a reference deconvolution technique that used the glutamate C5 peak as a lineshape reference.

10:54 374

In Vivo detection of trans-Fatty Acids by 13C MRS at 7T
Ivan Dimitrov1,2, Jimin Ren2, Deborah Douglas2, A Dean Sherry2, Craig R. Malloy2
Philips Medical Systems, Cleveland, OH, United States; 2Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX, United States

The severe health implications of trans-fats are well-known: their consumption leads to coronary heart disease, diabetes, cancer, liver dysfunction, and Alzheimerís. We report the first non-invasive detection of trans-fats in humans by 13C MRS at 7T. WALTZ-16 decoupled FIDs with NOE were acquired from calves of healthy volunteers in 5 min. The allylic carbons (α to C=C) display substantially different chemical shifts (cis 27.18 vs. trans 32.59 ppm). A volunteer on a Western diet had a trans : cis ratio = 4.4 %, consistent with ex vivo reports, whereas no trans-fats were detected in a volunteer on a Mediterranean diet.

11:06 375.  

Stimulated-Echo Contrast with Hyperpolarized [1-13C]-Pyruvate
Peder E. Z. Larson1, Ralph Hurd2, Adam B. Kerr3, Robert Bok1, John Kurhanewicz1, Daniel B. Vigneron1
Radiology and Biomedical Imaging, University of California - San Francisco, San Francisco, CA, United States; 2Applied Science Laboratory, GE Healthcare, Menlo Park, CA, United States; 3Electrical Engineering, Stanford University, Stanford, CA, United States

Stimulated-echoes can be used to provide high sensitivity to diffusion and flow, providing unique contrast.  We have developed and applied stimulated-echo pulse sequences for hyperpolarized 13C metabolic imaging, studying both normal animals and the TRAMP prostate cancer mouse model to better distinguish the local metabolite environment.  These experiments demonstrated a dramatic increase in CNR for tumors and present a new parameter for characterizing the metabolic state.

11:18 376.

Rapid Volumetric Imaging of Cardiac Metabolism
Angus Z. Lau1,2, Albert P. Chen3, Nilesh Ghugre2, Venkat Ramanan2, Wilfred W. Lam2, Kim A. Connelly4, Graham A. Wright1,2, Charles H. Cunningham1,2
Dept. of Medical Biophysics, University of Toronto, Toronto, ON, Canada; 2Imaging Research, Sunnybrook Health Sciences Centre, Toronto, ON, Canada; 3GE Healthcare, Toronto, ON, Canada; 4Keenan Research Centre, Li Ka Shing Knowledge Institute, St. Michaelís Hospital and University of Toronto, Toronto, ON, Canada

A rapid multi-slice cardiac-gated spiral 13C imaging pulse sequence consisting of a large flip-angle spectral-spatial excitation RF pulse with a single-shot spiral k-space trajectory was implemented and demonstrated in vivo. This sequence allows for whole heart coverage (6 slices, 8.8 mm in-plane resolution) in any plane, with imaging of the metabolites of interest, [1-13C] pyruvate, [1-13C] lactate, and 13C bicarbonate, within a single 20 s breathhold. The sequence is anticipated to be useful in the non-invasive monitoring of changes in spatial distribution of metabolites in disease.

11:30 377

High Resolution 31P Magnetic Resonance Spectroscopic Imaging of the Human Brain at 7T
Jannie Petra Wijnen1, Arend Heerschap1, Tom W.J. Scheenen1,2
1Radiology, Radboud University Nijmegen Medical Centre, Nijmegen, Gelderland, Netherlands; 2Erwin L. Hahn Institute for Magnetic Resonance Imaging, Essen, Germany

We demonstrated the use of a surface 31P quadrature coil in combination with a 1H CP head coil for 31P MRSI of the brain at 7T with high sensitivity and spatial resolution. 31P MRS was run with a pulse acquire MRSI sequence with adiabatic excitation. With this method we detected phosphorylated signals from the energy metabolism in the brain as well as resonances from phosphomono and diester compounds and inorganic phosphate in the human brain within relatively short acquisition times (16 or 25minutes).

11:42 378

Diffusion-Weighted Spectroscopy in the Healthy and U87 Glioblastoma-Induced Mouse Brain - not available
Julien Valette1,2, Boucif Djemai2, FranÁoise Geffroy2, Mohamed Ahmed Ghaly2, Fawzi Boumezbeur2, Denis Le Bihan2, Franck Lethimonnier2
1CEA-MIRCen, Fontenay-aux-Roses, France; 2CEA-NeuroSpin, Gif-sur-Yvette, France

Diffusion-weighted (DW) spectroscopy is a unique tool for probing the intracellular compartment in vivo. As far as we know, the apparent diffusion coefficient (ADC) of metabolites has never been reported in the mouse brain. In this preliminary work, the ADC of six metabolites is measured in a mouse brain for the first time, using an original DW-LASER sequence. In addition, measurements are performed in a Human U87-MG glioblastoma induced in the same animal, showing a dramatic increase in the ADC of choline compounds, which might be ascribed to lactacidosis-induced cell swelling.

11:54 379

Real Time Measurement and Correction of Motion-Induced Changes in B0 Field for Neuro Spectroscopic Imaging
Aaron Timothy Hess1, Ovidiu C. Andronesi2,3, Matthew Dylan Tisdall2,3, Ernesta M. Meintjes1,4, Andre J. van der Kouwe2,3
1University of Cape Town, Cape Town, South Africa; 2Martinos Center for Biomedical Imaging, Massachusetts General Hospital, MA, United States; 3Department of Radiology, Harvard Medical School, MA, United States; 4MRC/UCT Medical Imaging Research Unit

Real time measurement of the B0 field using an EPI navigator is presented, its use in real time first order shim correction for LASER spectroscopic imaging is demonstrated. Homogeneity of the B0 field is important in spectroscopy and spectroscopic imaging and thus, by measuring the B0 field in real time, changes to the linear shim gradients and frequency offset are corrected on the fly. This technique is shown to minimise line broadening due to motion induced B0 changes.

12:06 380.

Accelerated 1H Chemical Shift Imaging of the Brain Using Compressive Sensing
Sairam Geethanath1, Hyeonman Baek2, Vikram D. Kodibagkar1,2

1Biomedical Engineering, UT Southwestern Medical Center at Dallas, Dallas, TX, United States; 2Dept of Radiology, UT Southwestern Medical Center at Dallas, Dallas, TX, United States

Application of compressed sensing to 1H Chemical Shift Imaging (CSI) of in vivo human brain data has been performed for the first time. The CSI data is sparse in the wavelet domain along the spatial and temporal dimensions and hence can be reconstructed with high SNR from significantly undersampled k-space. This provides a significant reduction in acquisition time which is highly desired for CSI. The metabolite maps generated for 3 major metabolites of N-acetylaspartate, Creatine and Choline from 20% of the original k-space data match closely with the corresponding metabolite maps generated for the original k-space.

12:18 381

In Vivo L-COSY MR Distinguishes Glutamate from Glutamine and  Shows Neuropathic Pain to Cause a Buildup of Glutamine in the Brain
Alexander Peter Lin1, Saadallah Ramadan1, Peter Stanwell1, Tuan Luu1, James Celestin2, Zahid Bajwa2, Carolyn Mountford1
1Center for Clinical Spectroscopy, Brigham and Women's Hospital, Boston, MA, United States; 2Pain Management Center, Beth Israel Deaconess Medical Center, Boston, MA, United States

This study utilizes two-dimensional (2D)  COrrelated SpectroscopY (COSY) to allow, in a clinically accepted time, detailed chemical information to be collected in situ from the brain.  2D COSY can in theory separate the glutamate and glutamine resonances by measuring distinct  scalar coupling.  These metabolites are neurotransmitters and  affected by a number of diseases.  For the first time we successfully distinguished between  glutamine and glutamate using 2D COSY and show that glutamine is present  in higher quantities  in subjects with neuropathic pain.



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