Premium
Coaxial waveguide MRI
Author(s) -
Alt Stefan,
Müller Marco,
Umathum Reiner,
Bolz Armin,
Bachert Peter,
Semmler Wolfhard,
Bock Michael
Publication year - 2012
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.23069
Subject(s) - imaging phantom , finite difference time domain method , electromagnetic coil , computer science , specific absorption rate , acoustics , antenna (radio) , transmission (telecommunications) , physics , coaxial , waveguide , focus (optics) , radiofrequency coil , energy (signal processing) , optics , telecommunications , quantum mechanics
As ultrahigh‐field MR imaging systems suffer from the standing wave problems of conventional coil designs, the use of antenna systems that generate travelling waves was suggested. As a modification to the original approach, we propose the use of a coaxial waveguide configuration with interrupted inner conductor. This concept can focus the radiofrequency energy to the desired imaging region in the human body and can operate at different Larmor frequencies without hardware modifications, as it is not limited by a lower cut‐off frequency. We assessed the potential of the method with a hardware prototype setup that was loaded with a tissue equivalent phantom and operated with imaging areas of different size. Signal and flip angle distributions within the phantom were analyzed, and imaging at different Larmor frequencies was performed. Results were compared to a finite difference time domain simulation of the setup that additionally provides information on the spatial distribution of the specific absorption rate load. Furthermore, simulation results with a human model (virtual family) are presented. It was found that the proposed method can be used for MRI at multiple frequencies, achieving transmission efficiencies similar to other travelling wave approaches but still suffers from several limitations due to the used mode of wave propagation. Magn Reson Med, 2011. © 2011 Wiley Periodicals, Inc.