Cells (Dec 2020)

pH Mapping of Skeletal Muscle by Chemical Exchange Saturation Transfer (CEST) Imaging

  • Yu-Wen Chen,
  • Hong-Qing Liu,
  • Qi-Xuan Wu,
  • Yu-Han Huang,
  • Yu-Ying Tung,
  • Ming-Huang Lin,
  • Chia-Huei Lin,
  • Tsai-Chen Chen,
  • Eugene C. Lin,
  • Dennis W. Hwang

DOI
https://doi.org/10.3390/cells9122610
Journal volume & issue
Vol. 9, no. 12
p. 2610

Abstract

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Magnetic resonance imaging (MRI) is extensively used in clinical and basic biomedical research. However, MRI detection of pH changes still poses a technical challenge. Chemical exchange saturation transfer (CEST) imaging is a possible solution to this problem. Using saturation transfer, alterations in the exchange rates between the solute and water protons because of small pH changes can be detected with greater sensitivity. In this study, we examined a fatigued skeletal muscle model in electrically stimulated mice. The measured CEST signal ratio was between 1.96 ppm and 2.6 ppm in the z-spectrum, and this was associated with pH values based on the ratio between the creatine (Cr) and the phosphocreatine (PCr). The CEST results demonstrated a significant contrast change at the electrical stimulation site. Moreover, the pH value was observed to decrease from 7.23 to 7.15 within 20 h after electrical stimulation. This pH decrease was verified by 31P magnetic resonance spectroscopy and behavioral tests, which showed a consistent variation over time.

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