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

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Abstract

Purpose To develop an inversion pulse-based, chemical exchange saturation transfer-like method for detection of 31P 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 31P 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.

Original languageEnglish (US)
Pages (from-to)1359-1369
Number of pages11
JournalMagnetic resonance in medicine
Volume73
Issue number4
DOIs
StatePublished - Apr 1 2015

Keywords

  • T relaxation time
  • chemical exchange
  • magnetization transfer
  • nuclear Overhauser effects
  • skeletal muscle

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging

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