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High‐order coils as transmitters for NMR imaging
Author(s) -
Sotgiu Antonello,
Hyde James S.
Publication year - 1986
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.1910030108
Subject(s) - electromagnetic coil , axial symmetry , transverse plane , physics , radiofrequency coil , nuclear magnetic resonance , cylinder , magnetic field , context (archaeology) , optics , excitation , field (mathematics) , weighting , computational physics , acoustics , mathematics , geometry , quantum mechanics , engineering , paleontology , structural engineering , biology , pure mathematics
High‐order radiofrequency transmitter coils are described that permit, in the context of NMR imaging, a knowledgeable trade‐off between coil complexity and the degree of inhomogeneity over a specified volume of space. A mathematical formulation of high‐order coils is developed for an axially symmetric polarizing de field and transverse rf field. The field is created by a number of longitudinal current filaments with equal angular separations on the wall of a cylinder. In its most general form, each current can be independently specified. Circularly or linearly polarized fields can be created. Quadrature and saddleshaped coils emerge as special cases of the general formulation. The development has been tested experimentally and good agreement found. High‐order coils can also be used as receivers, permitting more equal weighting of the sensitivities of each pixel. © 1986 Academic Press, Inc.