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Multipathway multi‐echo (MPME) imaging: all main MR parameters mapped based on a single 3D scan
Author(s) -
Cheng ChengChieh,
Preiswerk Frank,
Hoge W. Scott,
Kuo TaiHsin,
Madore Bruno
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.27525
Subject(s) - imaging phantom , flip angle , echo (communications protocol) , physics , nuclear magnetic resonance , magnetic resonance imaging , image resolution , spin echo , nuclear medicine , gradient echo , computer science , optics , medicine , radiology , computer network
Purpose Quantitative parameter maps, as opposed to qualitative grayscale images, may represent the future of diagnostic MRI. A new quantitative MRI method is introduced here that requires a single 3D acquisition, allowing good spatial coverage to be achieved in relatively short scan times. Methods A multipathway multi‐echo sequence was developed, and at least 3 pathways with 2 TEs were needed to generate T 1 , T 2 , T 2 * , B 1 + , and B 0 maps. The method required the central k ‐space region to be sampled twice, with the same sequence but with 2 very different nominal flip angle settings. Consequently, scan time was only slightly longer than that of a single scan. The multipathway multi‐echo data were reconstructed into parameter maps, for phantom as well as brain acquisitions, in 5 healthy volunteers at 3 T. Spatial resolution, matrix size, and FOV were 1.2 × 1.0 × 1.2 mm 3 , 160 × 192 × 160, and 19.2 × 19.2 × 19.2 cm 3 (whole brain), acquired in 11.5 minutes with minimal acceleration. Validation was performed against T 1 , T 2 , and T 2 * maps calculated from gradient‐echo and spin‐echo data. Results In Bland‐Altman plots, bias and limits of agreement for T 1 and T 2 results in vivo and in phantom were −2.9/±125.5 ms ( T 1 in vivo), −4.8/±20.8 ms ( T 2 in vivo), −1.5/±18.1 ms ( T 1 in phantom), and −5.3/±7.4 ms ( T 2 in phantom), for regions of interest including given brain structures or phantom compartments. Due to relatively high noise levels, the current implementation of the approach may prove more useful for region of interest–based as opposed to pixel‐based interpretation. Conclusions We proposed a novel approach to quantitatively map MR parameters based on a multipathway multi‐echo acquisition.