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An equal‐TE ultrafast 3D gradient‐echo imaging method with high tolerance to magnetic susceptibility artifacts: Application to BOLD functional MRI
Author(s) -
Ryu JaeKyun,
Jung Won Beom,
Yu Jaeyong,
Son Jeong Pyo,
Lee SeungKyun,
Kim SeongGi,
Park JangYeon
Publication year - 2021
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.28564
Subject(s) - nuclear magnetic resonance , magnetic resonance imaging , functional magnetic resonance imaging , spin echo , in vivo , neuroimaging , physics , human brain , biomedical engineering , computer science , nuclear medicine , neuroscience , medicine , psychology , biology , radiology , microbiology and biotechnology
Purpose To develop an ultrafast 3D gradient echo–based MRI method with constant TE and high tolerance to B 0 inhomogeneity, dubbed ERASE (equal‐TE rapid acquisition with sequential excitation), and to introduce its use in BOLD functional MRI (fMRI). Theory and Methods Essential features of ERASE, including spin behavior, were characterized, and a comparison study was conducted with conventional EPI. To demonstrate high tolerance to B 0 inhomogeneity, in vivo imaging of the mouse brain with a fiber‐optic implant was performed at 9.4 T, and human brain imaging (including the orbitofrontal cortex) was performed at 3 T and 7 T. To evaluate the performance of ERASE in BOLD‐fMRI, the characteristics of SNR and temporal SNR were analyzed for in vivo rat brains at 9.4 T in comparison with multislice gradient‐echo EPI. Percent signal changes and t‐scores are also presented. Results For both mouse brain and human brain imaging, ERASE exhibited a high tolerance to magnetic susceptibility artifacts, showing much lower distortion and signal dropout, especially in the regions involving large magnetic susceptibility effects. For BOLD‐fMRI, ERASE provided higher temporal SNR and t‐scores than EPI, but exhibited similar percent signal changes in in vivo rat brains at 9.4 T. Conclusion When compared with conventional EPI, ERASE is much less sensitive, not only to EPI‐related artifacts such as Nyquist ghosting, but also to B 0 inhomogeneity including magnetic susceptibility effects. It is promising for use in BOLD‐fMRI, providing higher temporal SNR and t‐scores with constant TE when compared with EPI, although further optimization is needed for human fMRI.