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Imaging of amide proton transfer and nuclear Overhauser enhancement in ischemic stroke with corrections for competing effects
Author(s) -
Li Hua,
Zu Zhongliang,
Zaiss Moritz,
Khan Imad S.,
Singer Robert J.,
Gochberg Daniel F.,
Bachert Peter,
Gore John C.,
Xu Junzhong
Publication year - 2015
Publication title -
nmr in biomedicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.278
H-Index - 114
eISSN - 1099-1492
pISSN - 0952-3480
DOI - 10.1002/nbm.3243
Subject(s) - magnetization transfer , nuclear magnetic resonance , chemistry , ischemic stroke , proton , stroke (engine) , magnetic resonance imaging , ischemia , cardiology , physics , medicine , radiology , thermodynamics , quantum mechanics
Chemical exchange saturation transfer (CEST) potentially provides the ability to detect small solute pools through indirect measurements of attenuated water signals. However, CEST effects may be diluted by various competing effects, such as non‐specific magnetization transfer (MT) and asymmetric MT effects, water longitudinal relaxation ( T 1 ) and direct water saturation (radiofrequency spillover). In the current study, CEST images were acquired in rats following ischemic stroke and analyzed by comparing the reciprocals of the CEST signals at three different saturation offsets. This combined approach corrects the above competing effects and provides a more robust signal metric sensitive specifically to the proton exchange rate constant. The corrected amide proton transfer (APT) data show greater differences between the ischemic and contralateral (non‐ischemic) hemispheres. By contrast, corrected nuclear Overhauser enhancements (NOEs) around −3.5 ppm from water change over time in both hemispheres, indicating whole‐brain changes that have not been reported previously. This study may help us to better understand the contrast mechanisms of APT and NOE imaging in ischemic stroke, and may also establish a framework for future stroke measurements using CEST imaging with spillover, MT and T 1 corrections. Copyright © 2014 John Wiley & Sons, Ltd.