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

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.

[1]  H. Hetherington,et al.  Non‐Pi buffer capacity and Initial phosphocreatine breakdown and resynthesis kinetics of human gastrocnemius/soleus muscle groups using 0.5 s time‐resolved 31P MRS at 4.1 T , 1999, NMR in biomedicine.

[2]  P. Carlier,et al.  Muscle blood flow and oxygenation measured by NMR imaging and spectroscopy , 2006, NMR in biomedicine.

[3]  D. Wilkie,et al.  The activity of creatine kinase in frog skeletal muscle studied by saturation-transfer nuclear magnetic resonance. , 1981, The Biochemical journal.

[4]  J. S. Orr,et al.  Tissue characterization by magnetic resonance spectroscopy and imaging: Results of a concerted research project of the European Economic Community. Introduction, objectives, and activities. , 1993, Magnetic resonance imaging.

[5]  R. Spencer,et al.  Measurement of Spin-Lattice Relaxation Times in Systems Undergoing Chemical Exchange , 1994 .

[6]  B. Damon,et al.  Spatial heterogeneity in the muscle functional MRI signal intensity time course: effect of exercise intensity. , 2008, Magnetic resonance imaging.

[7]  S. Forbes,et al.  Comparison of oxidative capacity among leg muscles in humans using gated 31P 2‐D chemical shift imaging , 2009, NMR in biomedicine.

[8]  E. Moser,et al.  Dynamic interleaved 1H/31P STEAM MRS at 3 Tesla using a pneumatic force-controlled plantar flexion exercise rig , 2005, Magnetic Resonance Materials in Physics, Biology and Medicine.

[9]  P. Cozzone,et al.  23 – 31P NMR Spectroscopy of Metabolic Changes Associated with Muscle Exercise: Physiopathological Applications , 1994 .

[10]  Ewald Moser,et al.  Absolute quantification of phosphorus metabolite concentrations in human muscle in vivo by 31P MRS: a quantitative review , 2007, NMR in biomedicine.

[11]  Ewald Moser,et al.  Direct noninvasive quantification of lactate and high energy phosphates simultaneously in exercising human skeletal muscle by localized magnetic resonance spectroscopy , 2007, Magnetic resonance in medicine.

[12]  S. Confort-Gouny,et al.  Heterogeneity of metabolic response to muscular exercise in humans , 1990, FEBS letters.

[13]  C. Hofer,et al.  Effects of functional electrical stimulation in denervated thigh muscles of paraplegic patients mapped with T2 imaging , 2008, Magnetic Resonance Materials in Physics, Biology and Medicine.

[14]  Vanhamme,et al.  Improved method for accurate and efficient quantification of MRS data with use of prior knowledge , 1997, Journal of magnetic resonance.

[15]  E. Moser,et al.  Three‐dimensional high‐resolution magnetic resonance spectroscopic imaging for absolute quantification of 31P metabolites in human liver , 2008, Magnetic resonance in medicine.

[16]  E Moser,et al.  Quantitative ATP synthesis in human liver measured by localized 31P spectroscopy using the magnetization transfer experiment , 2008, NMR in biomedicine.

[17]  R. Ogg,et al.  The Line Broadening and Unambiguous Specification of the Gaussian Filter , 1995 .

[18]  J. Listinsky.  NMR in Physiology and Biomedicine , 1996 .

[19]  C. Boesch,et al.  Effect of ethanol and fructose on liver metabolism: a dynamic 31Phosphorus magnetic resonance spectroscopy study in normal volunteers. , 1997, Magnetic resonance imaging.

[20]  Shoko Nioka,et al.  Skeletal muscle energetics with PNMR: personal views and historic perspectives , 2006, NMR in biomedicine.

[21]  Ewald Moser,et al.  Ultra-high-field magnetic resonance: Why and when? , 2010, World journal of radiology.

[22]  P. Carlier,et al.  Multiparametric NMR-based assessment of skeletal muscle perfusion and metabolism during exercise in elderly persons: preliminary findings. , 2009, The journals of gerontology. Series A, Biological sciences and medical sciences.

[23]  P. Zaniol,et al.  in vivo assessment of mitochondrial functionality in human gastrocnemius muscle by 31P MRS. The role of pH in the evaluation of phosphocreatine and inorganic phosphate recoveries from exercise , 1993, NMR in biomedicine.

[24]  Wei Chen,et al.  Efficient in vivo 31P magnetization transfer approach for noninvasively determining multiple kinetic parameters and metabolic fluxes of ATP metabolism in the human brain , 2007, Magnetic Resonance in Medicine.

[25]  G. Hunter,et al.  31P MRS measurement of mitochondrial function in skeletal muscle: reliability, force‐level sensitivity and relation to whole body maximal oxygen uptake , 1995, NMR in biomedicine.

[26]  On neglecting chemical exchange effects when correcting in vivo (31)P MRS data for partial saturation. , 2001, Journal of magnetic resonance.

[27]  S Trattnig,et al.  Assessment of 31P relaxation times in the human calf muscle: A comparison between 3 T and 7 T in vivo , 2009, Magnetic resonance in medicine.

[28]  L DelaBarre,et al.  The return of the frequency sweep: designing adiabatic pulses for contemporary NMR. , 2001, Journal of magnetic resonance.

[29]  Dennis W J Klomp,et al.  Short echo time 1H‐MRSI of the human brain at 3T with minimal chemical shift displacement errors using adiabatic refocusing pulses , 2008, Magnetic resonance in medicine.

[30]  P. Cozzone,et al.  Functional investigations of exercising muscle: a noninvasive magnetic resonance spectroscopy-magnetic resonance imaging approach , 2004, Cellular and Molecular Life Sciences CMLS.

[31]  Robert J. Gillies,et al.  NMR in physiology and biomedicine , 1994 .

[32]  M. Weiner,et al.  Noninvasive quantitation of phosphorus metabolites in human tissue by NMR spectroscopy , 1989 .

[33]  G. Kemp,et al.  Non-Invasive Methods for Studying Brain Energy Metabolism: What They Show and What It Means , 2000, Developmental Neuroscience.

[34]  D. Wilkie,et al.  Muscular fatigue investigated by phosphorus nuclear magnetic resonance , 1978, Nature.

[35]  Ewald Moser,et al.  Relaxation times of 31P‐metabolites in human calf muscle at 3 T , 2003, Magnetic resonance in medicine.

[36]  Arend Heerschap,et al.  Towards 1H-MRSI of the human brain at 7T with slice-selective adiabatic refocusing pulses , 2008, Magnetic Resonance Materials in Physics, Biology and Medicine.

[37]  D. Graveron-Demilly,et al.  Java-based graphical user interface for the MRUI quantitation package , 2001, Magnetic Resonance Materials in Physics, Biology and Medicine.

[38]  B Chance,et al.  Mitochondrial regulation of phosphocreatine/inorganic phosphate ratios in exercising human muscle: a gated 31P NMR study. , 1981, Proceedings of the National Academy of Sciences of the United States of America.