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Imaging pH using the chemical exchange saturation transfer (CEST) MRI: Correction of concomitant RF irradiation effects to quantify CEST MRI for chemical exchange rate and pH
Author(s) -
Sun Phillip Zhe,
Sorensen A. Gregory
Publication year - 2008
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.21653
Subject(s) - nuclear magnetic resonance , chemistry , magnetic resonance imaging , imaging phantom , irradiation , rf power amplifier , saturation (graph theory) , nuclear medicine , materials science , biomedical engineering , radiology , physics , optoelectronics , medicine , amplifier , mathematics , cmos , combinatorics , nuclear physics
Chemical exchange saturation transfer (CEST) MRI has been shown capable of detecting dilute labile protons and abnormal tissue glucose/oxygen metabolism, and thus, may serve as a complementary imaging technique to the conventional MRI methods. CEST imaging, however, is also dependent on experimental parameters such as the power, duration, and waveform of the irradiation RF pulse. As a result, its sensitivity and specificity for microenvironment properties such as pH is not optimal. In this study, the dependence of CEST contrast on experimental parameters was solved and an iterative compensation algorithm was proposed that corrects the experimentally measured CEST contrast from the concomitant RF irradiation effects. The proposed algorithm was verified with both numerical simulation and experimental measurements from a tissue‐like pH phantom, and showed that pH derived from the compensated CEST imaging agrees reasonably well with pH‐electrode measurements within 0.1 pH unit. In sum, our study validates the use of a correction algorithm to compensate CEST imaging from concomitant RF irradiation effects for accurate calibration of the chemical exchange rate, and demonstrates the feasibility of pH imaging with CEST MRI. Magn Reson Med 60:390–397, 2008. © 2008 Wiley‐Liss, Inc.