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Simultaneous estimation of PD, T 1 , T 2 , T 2 * , and ∆B 0 using magnetic resonance fingerprinting with background gradient compensation
Author(s) -
Hong Taehwa,
Han Dongyeob,
Kim DongHyun
Publication year - 2019
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.27556
Subject(s) - shim (computing) , imaging phantom , magnetic resonance imaging , nuclear magnetic resonance , compensation (psychology) , physics , nuclear medicine , optics , medicine , radiology , psychology , erectile dysfunction , psychoanalysis
Purpose This study aims to estimate PD, T 1 , T 2 , T 2 * , and Δ B 0 simultaneously using magnetic resonance fingerprinting (MRF) with compensation of the linearly varying background field. Methods MRF based on fast imaging with steady‐state precession (FISP) and multi‐echo spoiled gradient (SPGR) schemes are alternatively used, which encode T 2 and T 2 * , respectively. Simulations are performed to determine the appropriate ratio of the FISP and SPGR sections with respect to the T 2 and T 2 * accuracy. Additionally, background field inhomogeneity (G z ) compensation using z‐shim gradients are incorporated into the SPGR section and the dictionary. The background field compensation is tested in the phantom experiment under well‐shimmed and poor‐shimmed conditions. An in vivo experiment is performed and the estimated parameters are compared before and after G z compensation. Results The T 1 , T 2 , and T 2 * values from the phantom results are in good agreement with the reference methods under well‐shimmed condition. The underestimated T 2 and T 2 * values under poor‐shimmed condition are recovered by G z compensation and the parameters are also in good agreement with the reference methods. In the human brain, T 2 and T 2 * values are restored by G z compensation in regions where the magnetic field is particularly inhomogeneous, such as near the sinus and ear canals. Conclusions The proposed FISP and SPGR combined MRF provides a simultaneous estimation of PD, T 1 , T 2 , T 2 * , and Δ B 0 . By incorporating field inhomogeneity as a gradient term into both the sequence and dictionary, T 2 and T 2 * values can be restored where field inhomogeneity exists.