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Relaxation‐compensated fast multislice amide proton transfer (APT) imaging of acute ischemic stroke
Author(s) -
Sun Phillip Zhe,
Murata Yoshihiro,
Lu Jie,
Wang Xiaoying,
Lo Eng H.,
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.21591
Subject(s) - magnetization transfer , nuclear magnetic resonance , multislice , magnetic resonance imaging , chemistry , relaxation (psychology) , imaging phantom , nuclear medicine , radiology , medicine , physics
Amide proton transfer (APT) imaging is a variant form of chemical exchange saturation transfer (CEST) imaging that is based on the magnetization exchange between bulk water and labile endogenous amide protons. Given that chemical exchange is pH‐dependent, APT imaging has been shown capable of imaging ischemic tissue acidosis, and as such, may serve as a surrogate metabolic imaging marker complementary to perfusion and diffusion MRI. In order for APT imaging to properly diagnose heterogeneous pathologies such as stroke and cancer, fast volumetric APT imaging has to be developed. In this study the evolution of CEST contrast after RF irradiation was solved showing that although the CEST steady state is reached by the apparent longitudinal relaxation rate, the decreases of CEST contrast after irradiation is governed by the intrinsic relaxation constant. A volumetric APT imaging sequence is proposed that acquires multislice images immediately after a single long continuous wave (CW) RF irradiation, wherein the relaxation‐induced loss of CEST contrast is compensated for during postprocessing. The proposed technique was verified by numerical simulation, a tissue‐like dual‐pH phantom, and demonstrated on an embolic stroke animal model. In summary, our study has established a fast volumetric pH‐weighted APT imaging technique, allowing further investigation to fully evaluate its diagnostic power. Magn Reson Med 59:1175–1182, 2008. © 2008 Wiley‐Liss, Inc.