title: Dynamic31P-MRSI using spiral spectroscopic imaging can map mitochondrial capacity in muscles of the human calf during plantar flexion exercise at 7 T.
abstract: Phosphorus MRSI (31P-MRSI) using a spiral-trajectory readout at 7 T was developed for high temporal resolution mapping of the mitochondrial capacity of exercising human skeletal muscle. The sensitivity and localization accuracy of the method was investigated in phantoms. In vivo performance was assessed in 12 volunteers, who performed a plantar flexion exercise inside a whole-body 7 T MR scanner using an MR-compatible ergometer and a surface coil. In five volunteers the knee was flexed (~60°) to shift the major workload from the gastrocnemii to the soleus muscle. Spiral-encoded MRSI provided 16-25 times faster mapping with a better point spread function than elliptical phase-encoded MRSI with the same matrix size. The inevitable trade-off for the increased temporal resolution was a reduced signal-to-noise ratio, but this was acceptable. The phosphocreatine (PCr) depletion caused by exercise at 0° knee angulation was significantly higher in both gastrocnemii than in the soleus (i.e. 64.8 ± 19.6% and 65.9 ± 23.6% in gastrocnemius lateralis and medialis versus 15.3 ± 8.4% in the soleus). Spiral-encoded31P-MRSI is a powerful tool for dynamic mapping of exercising muscle oxidative metabolism, including localized assessment of PCr concentrations, pH and maximal oxidative flux with high temporal and spatial resolution.
authors.affiliation: High-Field MR Centre, Medical University of Vienna, Vienna, Austria.|Department of Biomedical Imaging and Image-Guided Therapy, Medical University of Vienna, Vienna, Austria.|Christian Doppler Laboratory for Clinical Molecular MR Imaging, Vienna, Austria.|Department of Imaging Methods, Institute of Measurement Science, Slovak Academy of Sciences, Bratislava, Slovakia.|Oxford Centre for Clinical Magnetic Resonance Research (OCMR), University of Oxford, Oxford, UK.
authors.forename: Ladislav
authors.initials: L
authors.lastname: Valkovič
authors.affiliation: High-Field MR Centre, Medical University of Vienna, Vienna, Austria.|Department of Biomedical Imaging and Image-Guided Therapy, Medical University of Vienna, Vienna, Austria.|Christian Doppler Laboratory for Clinical Molecular MR Imaging, Vienna, Austria.
authors.forename: Marek
authors.initials: M
authors.lastname: Chmelík
authors.affiliation: High-Field MR Centre, Medical University of Vienna, Vienna, Austria.|Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria.
authors.forename: Martin
authors.initials: M
authors.lastname: Meyerspeer
authors.affiliation: Fetal Neonatal Neuroimaging and Developmental Science Center, Boston Children's Hospital, Boston, Massachusetts, USA.
authors.forename: Borjan
authors.initials: B
authors.lastname: Gagoski
authors.affiliation: Oxford Centre for Clinical Magnetic Resonance Research (OCMR), University of Oxford, Oxford, UK.
authors.forename: Christopher T
authors.initials: CT
authors.lastname: Rodgers
authors.affiliation: High-Field MR Centre, Medical University of Vienna, Vienna, Austria.|Department of Biomedical Imaging and Image-Guided Therapy, Medical University of Vienna, Vienna, Austria.|Christian Doppler Laboratory for Clinical Molecular MR Imaging, Vienna, Austria.|Division of Endocrinology and Metabolism, Department of Internal Medicine III, Medical University of Vienna, Vienna, Austria.
authors.forename: Martin
authors.initials: M
authors.lastname: Krššák
authors.affiliation: Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: Ovidiu C
authors.initials: OC
authors.lastname: Andronesi
authors.affiliation: High-Field MR Centre, Medical University of Vienna, Vienna, Austria.|Department of Biomedical Imaging and Image-Guided Therapy, Medical University of Vienna, Vienna, Austria.|Christian Doppler Laboratory for Clinical Molecular MR Imaging, Vienna, Austria.
authors.forename: Siegfried
authors.initials: S
authors.lastname: Trattnig
authors.affiliation: High-Field MR Centre, Medical University of Vienna, Vienna, Austria.|Department of Biomedical Imaging and Image-Guided Therapy, Medical University of Vienna, Vienna, Austria.|Christian Doppler Laboratory for Clinical Molecular MR Imaging, Vienna, Austria.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Bogner
mesh_terms: D000328:Adult; D004734:Energy Metabolism / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D017079:Exercise Tolerance / Q000502:physiology; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D008931:Mitochondria, Muscle / Q000502:physiology* / Q000648:ultrastructure; D057054:Molecular Imaging / Q000379:methods*; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging / Q000502:physiology*; D010725:Phosphocreatine / Q000378:metabolism*; D010759:Phosphorus Isotopes / Q000493:pharmacokinetics; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D016059:Range of Motion, Articular; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D010759:Phosphorus Isotopes; D019275:Radiopharmaceuticals; D010725:Phosphocreatine
keywords: MRSI; dynamic 31P-MRS; high energy phosphate; skeletal muscle; spiral spectroscopic imaging; ultra-high field