Non-invasive determination of mitochondrial content is an important objective in clinical and sports medicine. 31P MRS approaches to obtain information on this parameter at low field strength... Show moreNon-invasive determination of mitochondrial content is an important objective in clinical and sports medicine. 31P MRS approaches to obtain information on this parameter at low field strength typically require in-magnet exercise. Direct observation of the intra-mitochondrial inorganic phosphate (Pi) pool in resting muscle would constitute an alternative, simpler method. In this study, we exploited the higher spectral resolution and signal-to-noise at 7T to investigate the MR visibility of this metabolite pool. 31P in vivo MR spectra of the resting soleus (SOL) muscle were obtained with 1H MR image-guided surface coil localization (six volunteers) and of the SOL and tibialis anterior (TA) muscle using 2D CSI (five volunteers). A resonance at a frequency 0.38 ppm downfield from the cytosolic Pi resonance (Pi(1); pH 7.0 ± 0.04) was reproducibly detected in the SOL muscle in all subjects and conditionally attributed to the intra-mitochondrial Pi pool (Pi(2); pH 7.3 ± 0.07). In the SOL muscle, the Pi(2)/Pi(1) ratio was 1.6 times higher compared to the TA muscle in the same individual. Localized 3D CSI results showed that the Pi(2) peak was present in voxels well away from blood vessels. Determination of the T1 of the two Pi pools in a single individual using adiabatic excitation of the spectral region around 5 ppm yielded estimates of 4.3 ± 0.4 s vs 1.4 ± 0.5 s for Pi(1) and Pi(2), respectively. Together, these results suggest that the intra-mitochondrial Pi pool in resting human skeletal muscle may be visible with 31P MRS at high field. Show less
Non-invasive determination of mitochondrial content is an important objective in clinical and sports medicine. P-31 MRS approaches to obtain information on this parameter at low field strength... Show moreNon-invasive determination of mitochondrial content is an important objective in clinical and sports medicine. P-31 MRS approaches to obtain information on this parameter at low field strength typically require in-magnet exercise. Direct observation of the intra-mitochondrial inorganic phosphate (Pi) pool in resting muscle would constitute an alternative, simpler method. In this study, we exploited the higher spectral resolution and signalto-noise at 7T to investigate the MR visibility of this metabolite pool. P-31 in vivo MR spectra of the resting soleus (SOL) muscle were obtained with H-1 MR image-guided surface coil localization (six volunteers) and of the SOL and tibialis anterior (TA) muscle using 2D CSI (five volunteers). A resonance at a frequency 0.38 ppm downfield from the cytosolic Pi resonance (Pi(1); pH 7.0 +/- 0.04) was reproducibly detected in the SOL muscle in all subjects and conditionally attributed to the intra-mitochondrial Pi pool (Pi(2); pH 7.3 +/- 0.07). In the SOL muscle, the Pi(2)/Pi(1) ratio was 1.6 times higher compared to the TA muscle in the same individual. Localized 3D CSI results showed that the Pi(2) peak was present in voxels well away from blood vessels. Determination of the T1 of the two Pi pools in a single individual using adiabatic excitation of the spectral region around 5 ppm yielded estimates of 4.3 +/- 0.4 s vs 1.4 +/- 0.5 s for Pi, and Pi(2), respectively. Together, these results suggest that the intra-mitochondrial Pi pool in resting human skeletal muscle may be visible with P-31 MRS at high field. Copyright (c) 2010 John Wiley & Sons, Ltd. Show less
Kan, H.E.; Klomp, D.W.J.; Wohlgemuth, M.; Loosbroek-Wagemans, I. van; Engelen, B.G.M. van; Padberg, G.W.; Heerschap, A. 2010
Facioscapulohumeral muscular dystrophy (FSHD) is characterized by asymmetric dysfunctioning of individual muscles. Currently, it is unknown why specific muscles are affected before others and more... Show moreFacioscapulohumeral muscular dystrophy (FSHD) is characterized by asymmetric dysfunctioning of individual muscles. Currently, it is unknown why specific muscles are affected before others and more particularly what pathophysiology is causing this differential progression. The aim of our study was to use a combination of P-31 magnetic resonance spectroscopic imaging (MRSI) and T1-weighted MRI to uncover metabolic differences in fat infiltrated and not fat infiltrated muscles in patients with FSHD. T1-weighted images and 3D P-31 MRSI were obtained from the calf muscles of nine patients with diagnosed FSHD and nine healthy age and sex matched volunteers. Muscles of patients were classified as fat infiltrated (PFM) and non fat-infiltrated (PNM) based on visual assessment of the MR images. Ratios of phosphocreatine (PCr), phosphodiesters (PDE) and inorganic phosphate (Pi) over ATP and tissue pH were compared between PFM and PNM and the same muscles in healthy volunteers. Of all patients, seven showed moderate to severe fatty infiltration in one or more muscles. In these muscles, decreases in PCr/ATP and increases in tissue pH were observed compared to the same muscles in healthy volunteers. Interestingly, these differences were absent in the PNM group. Our data show that differences in metabolite ratios and tissue pH in skeletal muscle between healthy volunteers and patients with FSHD appear to be specific for fat infiltrated muscles. Normal appearing muscles on T1 weighted images of patients showed normal phosphoryl metabolism, suggests that in FSHD disease progression is truly muscle specific. Copyright (C) 2010 John Wiley & Sons, Ltd. Show less
