Combined use of magnetic resonance imaging (MRI) and spectroscopy (MRS) by whole body magnets in studying skeletal muscle morphology and metabolism.

As a pilot study, 31-P-spectra of the quadriceps femoris muscle (1.5T) and proton images of the right thigh (.5T) were performed in two cyclists (T) and two 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 minutes. Ergometric bicycle tests were performed outside the magnet. Submaximal workload (UT 150W/T 260W, 3.5 minutes) caused transient minimal changes in phosphorus metabolites. Supramaximal, partially anaerobic exercise (UT 320W/T 350W, 3.5 minutes) induced similar changes in heart rate, oxygen 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.