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In vivo imaging of paraCEST agents using frequency labeled exchange transfer MRI
Author(s) -
Lin ChienYuan,
Yadav Nirbhay N.,
Ratnakar James,
Sherry A. Dean,
Zijl Peter C. M.
Publication year - 2014
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.24603
Subject(s) - in vivo , nuclear magnetic resonance , magnetization transfer , chemistry , paramagnetism , relaxation (psychology) , biophysics , magnetic resonance imaging , physics , radiology , medicine , microbiology and biotechnology , quantum mechanics , biology
Purpose A main obstacle to in vivo applications of paramagnetic chemical exchange saturation transfer (paraCEST) is interference from endogenous tissue magnetization transfer contrast (MTC). The suitability of excitation‐based frequency labeled exchange transfer (FLEX) to separate out such MTC effects in vivo was tested. Methods The FLEX sequence measures modulation of the water signal based on the chemical shift evolution of solute proton magnetization as a function of evolution time. Time‐domain analysis of this water signal allows identification of different solute components and provides a mechanism to separate out the rapidly decaying MTC components with short effective transverse relaxation time ( T 2 * ) values. Results FLEX imaging of paraCEST agents was possible in vitro in phantoms and in vivo in mouse kidneys and bladder. The results demonstrated that FLEX is capable of separating out the MTC signal from tissues in vivo while providing a quantitative exchange rate for the rapidly exchanging paraCEST water protons by fitting the FLEX time‐domain signal to FLEX theory. Conclusions The first in vivo FLEX images of a paraCEST agent were acquired, which allowed separation of the tissue MTC components. These results show that FLEX imaging has potential for imaging the distribution of functional paraCEST agents in biological tissues. Magn Reson Med 71:286–293, 2014. © 2013 Wiley Periodicals, Inc.