ISMRM 24th Annual Meeting & Exhibition • 07-13 May 2016 • Singapore

Scientific Session: Cardiac & Muscle MRS

Friday, May 13, 2016
Room 331-332
08:00 - 10:00
Moderators: Roland Kreis, S. Sendhil Velan

1H-MRS of the myocardium at 3T applying a 60-channel body array coil – initial experiences
Jürgen Machann1, Malte Niklas Bongers2, Andreas Fritsche3, Hans-Ulrich Häring3, Mike Notohamiprodjo4, Andreas Greiser5, Konstantin Nikolaou4, and Fritz Schick2
1Section on Experimental Radiology, Department of Diagnostic and Interventional Radiology, Institute for Diabetes Research and Metabolic Diseases (IDM) of the Helmholtz Center Munich, German Center for Diabetes Research (DZD), Tübingen, Germany, 2Section on Experimental Radiology, Department of Diagnostic and Interventional Radiology, University Hospital Tübingen, Tübingen, Germany, 3Department of Endocrinology and Diabetology, Angiology, Nephrology and Clinical Chemistry, Institute for Diabetes Research and Metabolic Diseases (IDM) of the Helmholtz Center Munich, German Center for Diabetes Research (DZD), Tübingen, Germany, 4Department of Diagnostic and Interventional Radiology, University Hospital Tübingen, Tübingen, Germany, 5Siemens Healthcare, Erlangen, Germany
1H-MRS is increasingly applied in many organs for non-invasive tissue characterization, e.g. for quantification of ectopic lipids. Spectroscopic examinations of the myocardium often suffer from limited spectral dispersion, thus limiting the metabolic information content. Applying a new 60-channel body-array receive coil, high quality spectra with superior dispersion as compared to previous setups are shown in this work. A single voxel PRESS technique was applied in 10 subjects. After higher-order shimming, linewidths of <20 Hz were obtained with high SNR in a clinically acceptable measuring time. High reproducibility and performance of the method may promote 1H-MRS applications in metabolic research and sports medicine.

Adiabatic excitation for 31P spectroscopy in the human heart at 7T
Ladislav Valkovic1,2, William T Clarke1, Benoit Schaller1, Lucian A B Purvis1, Stefan Neubauer1, Ivan Frollo2, Matthew D Robson1, and Christopher T Rodgers1
1Oxford Centre for Clinical Magnetic Resonance Research, University of Oxford, Oxford, United Kingdom, 2Department of Imaging Methods, Institute of Measurement Science, Slovak Academy of Sciences, Bratislava, Slovakia
31P-MRS is of particular interest in cardiovascular medicine, as the PCr/ATP ratio can serve as a predictor of mortality. However, due to inherently low signal-to-noise ratio (SNR), cardiac 31P-MRS is not yet practical in the clinic. To increase SNR, the use of 7T and dedicated receive arrays has been proposed. However, the peak B1+ was inadequate for the use of B1 insensitive pulses, thus far. In this study, we demonstrate the feasibility of homogeneous adiabatic excitation for cardiac 31P-MRS using a novel quadrature 31P transceiver at 7T. This constitutes an important step towards absolute quantification of cardiac metabolites at 7T.

Improvement of Quantification of 1H Cardiac MR Spectra Acquired at 3T by the Use of Prior Knowledge
Ariane Fillmer1,2, Andreas Hock2,3, and Anke Henning2,4
1Physikalisch Technische Bundesanstalt (PTB), Berlin, Germany, 2Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland, 3Department of Psychiatry, Psychotherapy and Psychosomatics, Hospital of Psychiatry, University of Zurich, Zurich, Switzerland, 4Max Planck Institute for Biological Cybernetics, Tuebingen, Germany
1H cardiac MRS is a promising tool for investigation of human heart disease. In this context the independent quantification of intramyocellular (IMCL) and extramyocellular lipids (EMCL) is desired. Quantification itself, however, remains challenging. This work investigates, whether quantification of metabolite signals within 1H cardiac MR spectra could be improved by the use of prior knowledge about the behavior of metabolite signals in the quantification process.

3D resolved human cardiac creatine kinase rate by 31P-MRS at 7T.
William Thomas Clarke1, Matthew D Robson1, and Christopher T Rodgers1
1Oxford Centre for Clinical Magnetic Resonance Research, University of Oxford, Oxford, United Kingdom
The creatine kinase (CK) forward rate constant kf is a sensitive biomarker for heart failure. However, the low SNR of 31P-MRS at 1.5T and 3T has only allowed it to be measured at low spatial resolution by 1D-CSI. Here, we show how cardiac 7T 31P-MRS permits 3D resolved measurements for the first time. A 3D variant of the FAST kfCK method was combined with 31P Bloch-Siegert B1+ mapping to enable 3D-resolved measurements at 7T. The first measurements of the creatine kinase rate in myocardium in the interventricular septum are obtained from four subjects. Our mean kf = 0.36±0.04 s-1 was consistent with literature values.

Second-Order Motion-Compensated PRESS for Cardiac Spectroscopy
Maximilian Fuetterer1, Christian Torben Stoeck1,2, and Sebastian Kozerke1,2
1Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland, 2Division of Imaging Sciences and Biomedical Engineering, King's College London, London, United Kingdom
Second-order motion compensation for PRESS (PRESSmc) is proposed to allow for robust single-voxel cardiac spectroscopy throughout the entire cardiac cycle. Motion-compensated spoiler gradients were designed and implemented into a cardiac-triggered PRESS sequence. A numerical 3D model of cardiac motion was used to optimize and validate the gradient waveforms. In-vivo measurements in healthy volunteers were obtained to assess SNR and triglyceride-to-water ratio (TG/W). SNR gains and variability of TG/W of PRESSmc were evaluated against a conventional PRESS sequence with optimized gradients. PRESSmc effectively reduces cardiac-motion induced signal degradation during FID spoiling providing higher SNR and less variability for TG/W quantification. 

Mapping of pH in the human calf muscle at 7 T with 31P 3D echo–planar spectroscopic imaging
Andreas Korzowski1 and Peter Bachert1
1Medical Physics in Radiology, German Cancer Research Center, Heidelberg, Germany
The tissue–pH value is an important parameter to assess physiological function. The purpose of this work was to explore the potential of three-dimensional 31P–{1H} echo–planar spectroscopic imaging at B0 = 7 T for mapping of intracellular pH in the human calf muscle with high spatial resolution. The acquired data demonstrate that the proposed method allows the robust quantification of intracellular pH value of voxels with less than 1 ml volume and therefore may give insight into the pH heterogeneity of different muscle groups.

Rapid and Simultaneous Measurements for Reaction Kinetics and Metabolite Pool Size Ratios using 31P Magnetization Saturation Transfer Spectroscopy
Sang-Young Kim1,2, Wei Chen3, Dost Ongur2, and Fei Du1,2
1McLean Imaging Center, McLean Hospital, Harvard Medical School, Belmont, MA, United States, 2Psychotic Disorders Division, McLean Hospital, Harvard Medical School, Belmont, MA, United States, 3Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States
 We demonstrates a novel strategy to simultaneously measure metabolites pool sizes and kinetic constants of CK/ATPase reactions using 31P-MST spectroscopy. Our method enables the corrections for T1relaxation time and chemical exchanges effects due to short TR. The most important advantage of our proposed method is the reduction of TR for complete measurements of both metabolites ratios and reaction kinetics with high sensitivity. This can facilitate future applications requiring high temporal and/or spatial resolution. 

Observation of 31P magnetization transfer at 3 Tesla using asymmetric adiabatic inversion and two different fitting strategies.
Bertrand Pouymayou1, Tania Buehler1, Roland Kreis1, and Chris Boesch1
1Depts. Radiology and Clinical Research, University of Bern, Bern, Switzerland
31P-MR spectroscopy inversion transfer (IT) is increasingly investigated as a complementary method to study ATP-synthesis and creatine kinase in vivo. Three aspects of the IT experiment are studied here, in a test-retest design (12 volunteers, resting vastus muscle): the ability to produce an efficient half band inversion in vivo with a short asymmetric adiabatic pulse, the repeatability of the kinetic parameters estimation at 3T and the impact of two different fitting strategies (individual spectrum vs. two-dimensional fitting). As a result, k[Pi>γ-ATP] can be reliably estimated within cohorts while k[PCr>γ-ATP] is accurate enough to be distinguished between individuals.

Localized 31P magnetization transfer in the rat brain to measure ATP synthesis rate: inorganic phosphate comes in two pools
Brice Tiret1,2, Vincent Lebon1,2, Emmanuel Brouillet1,2, and Julien Valette1,2
1CEA/DSV/I2BM/MIRCen, Fontenay-aux-Roses, France, 2CNRS Université Paris-Saclay UMR 9199, Fontenay-aux-Roses, France
Localized 31P MRS with progressive saturation transfer was performed in the rat brain to estimate the exchange rate between inorganic phosphate (Pi) and adenosine-tri-phosphate (ATP). It was found that two Pi pools, tentatively intra and extracellular pools, can be resolved at 11.7 T, and that only the intracellular Pi signal varies with progressive saturation, while the extracellular Pi signal remains constant. Not resolving this extracellular Pi can cause a significant bias in the estimation of the forward constant rate of ATP synthesis.

Dynamic 31P MRSI with spiral readout for quantification of mitochondrial capacity in muscles of the calf during plantar flexion exercise at 7T - Permission Withheld
Ladislav Valkovic1,2,3,4, Marek Chmelík1,2, Martin Meyerspeer1,5, Borjan Gagoski6, Martin Krššák1,2,7, Christopher T Rodgers4, Ivan Frollo3, Ovidiu C Andronesi8, Siegfried Trattnig1,2,9, and Wolfgang Bogner1,2
1High-field MR Centre, Medical University of Vienna, Vienna, Austria, 2Department of Biomedical Imaging and Image-guided Therapy, Medical University of Vienna, Vienna, Austria, 3Department of Imaging Methods, Institute of Measurement Science, Slovak Academy of Sciences, Bratislava, Slovakia, 4Oxford Centre for Clinical Magnetic Resonance Research, University of Oxford, Oxford, United Kingdom, 5Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria, 6Fetal Neonatal Neuroimaging and Developmental Science Center, Boston Children's Hospital, Boston, MA, United States, 7Division of Endocrinology and Metabolism, Department of Internal Medicine III, Medical University of Vienna, Vienna, Austria, 8Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, United States, 9Christian Doppler Laboratory for Clinical Molecular MR Imaging, Vienna, Austria
Typically, only rough localization by the sensitive volume of the surface coil is used for dynamic 31P-MRS. However, such localization often mixes signals from several muscle groups. Available single-muscle localization techniques (e.g., semi-LASER or DRESS) provide only limited coverage and current 31P-MRSI techniques suffer from slow acquisition. To overcome the low temporal resolution of the standard 31P-MRSI, caused by slow Cartesian readout, we have developed, and tested in healthy subjects at 7T, a 31P-MRSI sequence using spiral readout trajectory. This sequence enables spatially resolved quantification of mitochondrial capacity in several investigated muscles (e.g., GM, GL and SOL) simultaneously at 7T.



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