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Semi‐LASER localized dynamic 31 P magnetic resonance spectroscopy in exercising muscle at ultra‐high magnetic field
Author(s) -
Meyerspeer Martin,
Scheenen Tom,
Schmid Albrecht Ingo,
Mandl Thomas,
Unger Ewald,
Moser Ewald
Publication year - 2011
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.22730
Subject(s) - phosphocreatine , nuclear magnetic resonance , temporal resolution , spectroscopy , magnetic resonance imaging , excitation , chemistry , laser , magnetic field , saturation (graph theory) , nuclear magnetic resonance spectroscopy , voxel , materials science , physics , optics , computer science , mathematics , medicine , quantum mechanics , combinatorics , radiology , energy metabolism , artificial intelligence
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 31 P 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 T 1 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.