Dynamic PCr and pH imaging of human calf muscles during exercise and recovery using (31) P gradient-Echo MRI at 7 Tesla

• Published in: Magnetic resonance in medicine 2016-06, Vol.75 (6), p.2324-2331
• Main Authors: Schmid, Albrecht Ingo, Meyerspeer, Martin, Robinson, Simon Daniel, Goluch, Sigrun, Wolzt, Michael, Fiedler, Georg Bernd, Bogner, Wolfgang, Laistler, Elmar, Krššák, Martin, Moser, Ewald, Trattnig, Siegfried, Valkovič, Ladislav
• Format: Article
• Language: English
• Subjects: Adult; Exercise - physiology; Female; Humans; Hydrogen-Ion Concentration; Image Processing, Computer-Assisted - methods; Magnetic Resonance Imaging - methods; Male; Muscle, Skeletal - diagnostic imaging; Muscle, Skeletal - metabolism; Muscle, Skeletal - physiology; Phosphocreatine - analysis; Phosphocreatine - metabolism; Phosphorus Isotopes - metabolism; Signal-To-Noise Ratio; Young Adult
• ISSN: 1522-2594
• DOI: 10.1002/mrm.25822

Simultaneous acquisition of spatially resolved (31) P-MRI data for evaluation of muscle specific energy metabolism, i.e., PCr and pH kinetics. A three-dimensional (3D) gradient-echo sequence for multiple frequency-selective excitations of the PCr and Pi signals in an interleaved sampling scheme was developed and tested at 7 Tesla (T). The pH values were derived from the chemical shift-induced phase difference between the resonances. The achieved spatial resolution was ∼2 mL with image acquisition time below 6 s. Ten healthy volunteers were studied performing plantar flexions during the delay between (31) P-MRI acquisitions, yielding a temporal resolution of 9-10 s. Signal from anatomically matched regions of interest had sufficient signal-to-noise ratio to allow single-acquisition PCr and pH quantification. The Pi signal was clearly detected in voxels of actively exercising muscles. The PCr depletions were in gastrocnemius 42 ± 14% (medialis), 48 ± 17% (lateralis) and in soleus 20 ± 11%. The end exercise pH values were 6.74 ± 0.18 and 6.65 ± 0.27 for gastrocnemius medialis and lateralis, respectively, and 6.96 ± 0.12 for soleus muscle. Simultaneous acquisition of PCr and Pi images with high temporal resolution, suitable for measuring PCr and pH kinetics in exercise-recovery experiments, was demonstrated at 7T. This study presents a fast alternative to MRS for quantifying energy metabolism of posterior muscle groups of the lower leg. Magn Reson Med 75:2324-2331, 2016. © 2015 Wiley Periodicals, Inc.