Dynamic interleaved 1H/31P STEAM MRS at 3 Tesla using a pneumatic force-controlled plantar flexion exercise rig

Objective: To develop a measurement method for interleaved acquisition of ¹H and ³¹ STEAM localised spectra of exercising human calf muscle. Materials and Methods: A non-magnetic exercise rig with a pneumatic piston and sensors for force and pedal angle was constructed to enable plantar flexion measured in the 3 T MR scanner, which holds the dual tuned (¹H ,³¹P) surface coil used for signal transmission and reception. Results: ³¹ spectra acquired in interleaved mode benefit from higher Signal to noice ratio (factor of 1.34 ±0.06 for PCr) compared to standard acquisition due to the Nuclear Overhauser effect and substantial PCr/P_i changes during exercise can be observed in ³¹P spectra. ¹H spectral quality is equal to that in single mode experiments and allows Cr2 changes to be monitored. Conclusion: The feasibility of dynamic interleaved localised ¹H and ³¹P spectroscopy during plantar flexion exercise has been demonstrated using a custom-built pneumatic system for muscle activation. This opens the possibility of studying the dynamics of metabolism with multi nuclear MRS in a single run.