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Novel quadrature birdcage coil for a vertical B 0 field open MRI system
Author(s) -
Fujita Hiroyuki,
Braum William O.,
Morich Michael A.
Publication year - 2000
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 - 10.1002/1522-2594(200010)44:4<633::aid-mrm18>3.0.co;2-k
Subject(s) - nuclear magnetic resonance , electromagnetic coil , radiofrequency coil , quadrature (astronomy) , magnetic resonance imaging , computer science , physics , nuclear medicine , medicine , radiology , optics , quantum mechanics
A birdcage coil possesses various intrinsic resonant modes. One of the modes produces sinusoidal current distribution around the rung elements of the birdcage and generates a highly uniform B 1 field in the transverse plane. Another mode is the end‐ring resonant mode, in which there are no currents in the rungs of the birdcage, leaving the currents flowing in the top and bottom end‐rings. Thus, this mode behaves like a “Helmholtz pair,” producing a highly uniform B 1 field along the axis of the birdcage. By combining the sinusoidal resonant mode and the end‐ring resonant mode at the same frequency, a quadrature birdcage coil for a vertical B 0 field is made possible. In particular, the coil dimension can be chosen such that the two end‐ring loops behave as a Helmholtz pair, assuring the optimized B 1 field uniformity around the coil center region. The coil is well suited for a vertical B 0 MRI system, as both B 1 fields are perpendicular to the vertical B 0 field. To mimic a vertical B 0 field orientation, an existing horizontal bore MRI system was used with the RF coil oriented to simulate a “vertical” B 0 field. This is a report of the successful quadrature implementation of this novel birdcage coil. Magn Reson Med 44:633–640, 2000. © 2000 Wiley‐Liss, Inc.