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R 2 * mapping in the presence of macroscopic B 0 field variations
Author(s) -
Hernando Diego,
Vigen Karl K.,
Shimakawa Ann,
Reeder Scott B.
Publication year - 2012
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.23306
Subject(s) - dephasing , field (mathematics) , imaging phantom , nuclear magnetic resonance , signal (programming language) , paramagnetism , physics , tracking (education) , computational physics , algorithm , chemistry , computer science , mathematics , condensed matter physics , optics , psychology , pedagogy , pure mathematics , programming language
Abstract $R_2^{\ast ab}$ mapping has important applications in MRI, including functional imaging, tracking of super‐paramagnetic particles, and measurement of tissue iron levels. However, $R_2^{\ast ab}$ measurements can be confounded by several effects, particularly the presence of fat and macroscopic $B_0$ field variations. Fat introduces additional modulations in the signal. Macroscopic field variations introduce additional dephasing that results in accelerated signal decay. These effects produce systematic errors in the resulting $R_2^{\ast ab}$ maps and make the estimated $R_2^{\ast ab}$ values dependent on the acquisition parameters. In this study, we develop a complex‐reconstruction, confounder‐corrected $R_2^{\ast ab}$ mapping technique, which addresses the presence of fat and macroscopic field variations for both 2D and 3D acquisitions. This technique extends previous chemical shift‐encoded methods for $R_2^{\ast ab}$ , fat and water mapping by measuring and correcting for the effect of macroscopic field variations in the acquired signal. The proposed method is tested on several 2D and 3D phantom and in vivo liver, cardiac, and brain datasets. Magn Reson Med, 2012. © 2011 Wiley Periodicals, Inc.