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Correction of B 1 inhomogeneities using echo‐planar imaging of water
Author(s) -
Thulborn Keith R.,
Boada Fernando E.,
Shen Gary X.,
Christensen James D.,
Reese Timothy G.
Publication year - 1998
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.1910390306
Subject(s) - echo planar imaging , echo (communications protocol) , nuclear magnetic resonance , planar , materials science , magnetic resonance imaging , physics , computer science , medicine , radiology , computer graphics (images) , computer network
Reliable interpretation of the MR signal intensity over the FOV of an image must consider the spatial heterogeneity of instrumental sensitivity. A major source of such variation is the nonuniformity of the B 1 magnetic field of the radiofrequency coil. This heterogeneity can be minimized by coil design but is exaggerated by surface coils, which are used to maximize the signal‐to‐noise ratio for some applications. This paper describes a rapid method for mapping the B 1 field over the sample of interest, using 1 H echo‐planar imaging, to correct for B 1 distortions. The method applies to 1 H imaging and has been extended to non‐ 1 H imaging by using dual‐frequency coils in which the B., distributions are matched for the 1 H frequency and the frequency of interest. The approach is demonstrated in phantoms, animals, and humans and for sodium imaging.