Exchange kinetics by inversion transfer: integrated analysis of the phosphorus metabolite kinetic exchanges in resting human skeletal muscle at 7 T

Magn Reson Med. 2015 Apr;73(4):1359-69. doi: 10.1002/mrm.25256. Epub 2014 Apr 14.


Purpose: To develop an inversion pulse-based, chemical exchange saturation transfer-like method for detection of (31) P magnetization exchanges among all nuclear magnetic resonance visible metabolites suitable for providing an integrated kinetic analysis of phosphorus exchange reactions in vivo.

Methods: The exchange kinetics by inversion transfer (EKIT) sequence includes application of a frequency-selective inversion pulse arrayed over the range of relevant (31) P frequencies, followed by a constant delay and a hard readout pulse. A series of EKIT spectra, each given by a plot of Z-magnetization for each metabolite of interest versus frequency of the inversion pulse, can be generated from this single data set.

Results: EKIT spectra reflect chemical exchange due to known biochemical reactions, cross-relaxation effects, and relayed magnetization transfers due to both processes. The rate constants derived from EKIT data collected on resting human skeletal muscle were: ATP synthesis via ATP synthase (0.050 ± 0.016 s(-1) ), ATP synthesis via creatine kinase (0.264 ± 0.023 s(-1) ), and cross-relaxation between neighboring spin pairs within ATP (0.164 ± 0.022 s(-1) ).

Conclusion: EKIT provides a simple, alternative method to detect chemical exchange, cross relaxation, and relayed magnetization transfer effects in human skeletal muscle at 7 T.

Keywords: T1 relaxation time; chemical exchange; magnetization transfer; nuclear Overhauser effects; skeletal muscle.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Algorithms*
  • Computer Simulation
  • Female
  • Humans
  • Magnetic Resonance Spectroscopy / methods*
  • Male
  • Models, Biological*
  • Muscle, Skeletal / metabolism*
  • Phosphorus Compounds / metabolism*
  • Phosphorus Isotopes / pharmacokinetics
  • Radiopharmaceuticals / pharmacokinetics
  • Rest
  • Systems Integration


  • Phosphorus Compounds
  • Phosphorus Isotopes
  • Radiopharmaceuticals