• Open Access

Semi-LASER localized dynamic 31P magnetic resonance spectroscopy in exercising muscle at ultra-high magnetic field

Authors

  • Martin Meyerspeer,

    1. Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Wien, Austria
    2. MR Centre of Excellence, Medical University of Vienna, Wien, Austria
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  • Tom Scheenen,

    1. Department of Radiology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
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  • Albrecht Ingo Schmid,

    1. Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Wien, Austria
    2. MR Centre of Excellence, Medical University of Vienna, Wien, Austria
    3. Department of Clinical Pharmacology, Medical University of Vienna, Wien, Austria
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  • Thomas Mandl,

    1. Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Wien, Austria
    2. MR Centre of Excellence, Medical University of Vienna, Wien, Austria
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  • Ewald Unger,

    1. Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Wien, Austria
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  • Ewald Moser

    Corresponding author
    1. Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Wien, Austria
    2. MR Centre of Excellence, Medical University of Vienna, Wien, Austria
    • Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Lazarettgasse 14, 1090 Wien, Austria===

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Abstract

Magnetic resonance spectroscopy (MRS) can benefit from increased signal-to-noise ratio (SNR) of high magnetic fields. In this work, the SNR gain of dynamic 31P MRS at 7 T was invested in temporal and spatial resolution. Using conventional slice selective excitation combined with localization by adiabatic selective refocusing (semi-LASER) with short echo time (TE = 23 ms), phosphocreatine quantification in a 38 mL voxel inside a single exercising muscle becomes possible from single acquisitions, with SNR = 42 ± 4 in resting human medial gastrocnemius. The method was used to quantify the phosphocreatine time course during 5 min of plantar flexion exercise and recovery with a temporal resolution of 6 s (the chosen repetition time for moderate T1 saturation). Quantification of inorganic phosphate and pH required accumulation of consecutively acquired spectra when (resting) Pi concentrations were low. The localization performance was excellent while keeping the chemical shift displacement acceptably small. The SNR and spectral line widths with and without localization were compared between 3 T and 7 T systems in phantoms and in vivo. The results demonstrate that increased sensitivity of ultra-high field can be used to dynamically acquire metabolic information from a clearly defined region in a single exercising muscle while reaching a temporal resolution previously available with MRS in non-localizing studies only. The method may improve the interpretation of dynamic muscle MRS data. Magn Reson Med, 2011. © 2011 Wiley-Liss, Inc.

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