Z-spectrum appearance and interpretation in the presence of fat: Influence of acquisition parameters

Shu Zhang, Jochen Keupp, Xinzeng Wang, Ivan Dimitrov, Ananth J. Madhuranthakam, Robert E. Lenkinski, Elena Vinogradov

Research output: Contribution to journalArticlepeer-review

17 Scopus citations


Purpose: Chemical exchange saturation transfer (CEST) MRI is increasingly evolving from brain to body applications. One of the known problems in the body imaging is the presence of strong lipid signals. Although their influence on the CEST effect is acknowledged, there was no study that focuses on the interplay among echo time, fat fraction, and Z-spectrum. This study strives to address these points, with the emphasis on the application in the breast. Methods: Z-spectra were simulated in phase and out of phase of the main fat peak at −3.4 ppm, with the fat fraction varying from 0 to 100%. The magnetization transfer ratio asymmetry in two ranges, centering at the exchanging pool and at 3.5 ppm approximately opposite the nonexchanging fat pool, were calculated and were plotted against fat fraction. The results were verified in phantoms and in vivo. Results: The results demonstrate the combined influence of fat fraction and echo time on the Z-spectrum for gradient echo based CEST acquisitions. The influence is straightforward in the in-phase images, but it is more complicated in the out-of-phase images, potentially leading to erroneous CEST contrast. Conclusions: This study provides a basis for understanding the origin and appearance of lipid artifacts in CEST imaging, and lays the foundation for their efficient removal. Magn Reson Med 79:2731–2737, 2018.

Original languageEnglish (US)
Pages (from-to)2731-2737
Number of pages7
JournalMagnetic resonance in medicine
Issue number5
StatePublished - May 2018


  • CEST
  • IP
  • OP
  • body imaging
  • breast imaging
  • lipid artifact

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging


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