Dielectric waveguides for ultrahigh field magnetic resonance imaging
| Autor: | Anna Andreychenko, Debra S. Rivera, Alexander J.E. Raaijmakers, Cornelis A. T. van den Berg, J.J. Bluemink, W. Koning, Peter R. Luijten, Dennis W. J. Klomp |
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| Rok vydání: | 2015 |
| Předmět: |
Computer science
business.industry Physics::Optics Dielectric Cutoff frequency 030218 nuclear medicine & medical imaging law.invention Magnetic field Standing wave 03 medical and health sciences Wavelength 0302 clinical medicine Optics Nuclear magnetic resonance law Electromagnetic coil Radiology Nuclear Medicine and imaging business Waveguide 030217 neurology & neurosurgery Excitation |
| Zdroj: | Magnetic Resonance in Medicine. 76:1314-1324 |
| ISSN: | 0740-3194 |
| Popis: | 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. |
| Databáze: | OpenAIRE |
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