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Phase reconstruction from multiple coil data using a virtual reference coil
Author(s) -
Parker Dennis L.,
Payne Allison,
Todd Nick,
Hadley J. Rock
Publication year - 2014
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.24932
Subject(s) - electromagnetic coil , phase (matter) , computer science , rogowski coil , nuclear magnetic resonance , physics , electrical engineering , engineering , quantum mechanics
Purpose This study develops a method to obtain optimal estimates of absolute magnetization phase from multiple‐coil MRI data. Theory and Methods The element‐specific phases of a multi‐element receiver coil array are accounted for by using the phase of a real or virtual reference coil that is sensitive over the entire imaged volume. The virtual‐reference coil is generated as a weighted combination of measurements from all receiver coils. The phase‐corrected multiple coil complex images are combined using the inverse covariance matrix. These methods are tested on images of an agar phantom, an in vivo breast, and an anesthetized rabbit obtained using combinations of four, nine, and three receiver channels, respectively. Results The four‐ and three‐channel acquisitions require formation of a virtual‐reference receiver coil while one channel of the nine‐channel receive array has a sensitivity profile covering the entire imaged volume. Referencing to a real or virtual coil gives receiver phases that are essentially identical except for the individual receiver channel noise. The resulting combined images, which account for receiver channel noise covariance, show the expected reduction in phase variance. Conclusion The proposed virtual reference coil method determines a phase distribution for each coil from which an optimal phase map can be obtained. Magn Reson Med 72:563–569, 2014. © 2013 Wiley Periodicals, Inc.