Novel proton exchange rate MRI presents unique contrast in brains of ischemic stroke patients

Zhenxiong Wang, Mehran Shaghaghi, Shun Zhang, Guiling Zhang, Yiran Zhou, Di Wu, Zhuoli Zhang, Wenzhen Zhu*, Kejia Cai

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


Background: To map and quantify the proton exchange rate (kex) of brain tissues using improved omega plots in ischemic stroke patients and to investigate whether kex can serve as a potential endogenous surrogate imaging biomarker for detecting the metabolic state and the pathologic changes due to ischemic stroke. New Method: Three sets of Z-spectra were acquired from seventeen ischemic stroke patients using a spin echo-echo planar imaging sequence with pre-saturation chemical exchange saturation transfer (CEST) pulse at B1 of 1.5, 2.5, and 3.5 μT, respectively. Pixel-wise kex was calculated from improved omega plot of water direct saturation (DS)-removed Z-spectral signals. Results: The derived kex maps can differentiate infarcts from contralateral normal brain tissues with significantly increased signal (893 ± 52 s-1 vs. 739 ± 34 s-1, P < 0.001). Comparison with Existing Method(s): The kex maps were found to be different from conventional contrasts from diffusion-weighted imaging (DWI), CEST, and semi-solid magnetization transfer (MT) MRI. In brief, kex MRI showed larger lesion areas than DWI with different degrees and different lesion contrast compared to CEST and MT. Conclusions: In this preliminary translational research, the kex MRI based on DS-removed omega plots has been demonstrated for in vivo imaging of clinical ischemic stroke patients. As a noninvasive and unique MRI contrast, kex MRI at 3 T may serve as a potential surrogate imaging biomarker for the metabolic changes of stroke and help for monitoring the evolution and the treatment of stroke.

Original languageEnglish (US)
Article number108926
JournalJournal of Neuroscience Methods
StatePublished - Dec 1 2020


  • Chemical exchange saturation transfer (CEST)
  • Omega plot
  • Proton exchange rate (k)
  • Stroke

ASJC Scopus subject areas

  • Neuroscience(all)


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