Hermien E. Kan1, Dennis W.J. Klomp2, Andrew G. Webb1, Peter R. Luijten2, Jeroen A.L. Jeneson3
1Radiology, Leiden University Medical Center, Leiden, Netherlands; 2High field MR laboratory, RNN, University Medical Center Utrecht, Utrecht, Netherlands; 33Biomedical NMR Laboratory, Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, Netherlands
Non-invasive fiber-type profiling of human skeletal muscles has been a long-time objective in musculoskeletal MR research. Up till now, most MR studies focused on contracting muscles to obtain a measure for fiber type. In the present study we show, for the first in resting human skeletal muscle, the existence of different pH compartments in the soleus muscle. We hypothesize that the second Pi resonance at 5.2 ppm originates from the mitochondrial matrix in type I myofibers, thereby providing a non-invasive measure for the in vivo free Pi concentration in mitochondria.