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Dielectric waveguides for ultrahigh field magnetic resonance imaging
Author(s) -
Bluemink Johanna J.,
Raaijmakers Alexander J. E.,
Koning Wouter,
Andreychenko Anna,
Rivera Debra S.,
Luijten Peter R.,
Klomp Dennis W. J.,
van den Berg Cornelis A. T.
Publication year - 2016
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.26007
Subject(s) - nuclear magnetic resonance , magnetic resonance imaging , field (mathematics) , dielectric , magnetic field , resonance (particle physics) , materials science , physics , optics , optoelectronics , atomic physics , radiology , medicine , mathematics , quantum mechanics , pure mathematics
Purpose The design of RF coils for MRI transmit becomes increasingly challenging at high frequencies required for MRI at 7T and above. Our goal is to show a proof of principle of a new type of transmit coil for higher field strengths. Method We demonstrate an alternative transmit coil design based on dielectric waveguide principles which transfers energy via evanescent wave coupling. The operating principles and conditions are explored by simulations. The waveguide is applied for in vivo imaging at 7T. Results The waveguide can be an efficient transmit coil when four conditions are fulfilled: (1) the waveguide should be operated just above the cutoff frequency of the lowest order transverse electric mode, (2) the waveguide should not operate at a frequency where the wavelength fits an integer number of times in the waveguide length and standing wave patterns become very prominent, (3) for homogeneous excitation, the waveguide should be bent around the object, and (4) there should be an air gap between the waveguide and the object. Conclusions By choosing the dielectric and the dimensions adequately, the dielectric waveguide couples the magnetic field efficiently into the body. The waveguide can be redesigned for higher frequencies by simple adaptations and may be a promising transmit alternative. Magn Reson Med 76:1314–1324, 2016. © 2015 Wiley Periodicals, Inc.