Combined Use of Magnetic Resonance Imaging (MRI) and Spectroscopy (MRS) by Whole Body Magnets in Studying Skeletal Muscle Morphology and Metabolism

Abstract

As a pilot study, 31-P-spectra of the quadriceps femoris muscle (1.5T) and proton images of the right thigh (0.5T) were performed in 2 cyclists (T) and 2 untrained (UT) subjects. During ischemia, while MRI did not show any change, phosphocreatine (PCr) concentration decreased and inorganic phosphate (Pi) increased. Recovery occurred within 3 min. Ergometric bicycle tests were performed outside the magnet. Submaximal workload (UT 150W/T 260W, 3.5 min) caused transient minimal changes in phosphorus metabolites. Supramaximal, partially anaerobic exercise (UT 320W/T 350W, 3.5 min) induced similar changes in heart rate, O2 uptake rate and plasma lactate in both groups. Decrease of the PCr/Pi ratio, however, was more pronounced in UT subjects and clearly lasted longer. If methodical problems can be resolved, combined MRS and MRI in whole body magnets may become a standard noninvasive modality, adding unique information on morphology (organ volume) and local metabolism to classic mechanical and global physiologic data.