Improved traveling-wave efficiency in 7T human MRI using passive local loop and dipole arrays.

Yan X, Zhang X, Gore JC, Grissom WA
Magn Reson Imaging. 2017 39: 103-109

PMID: 28189821 · PMCID: PMC5410385 · DOI:10.1016/j.mri.2017.02.003

Traveling-wave MRI, which uses relatively small and simple RF antennae, has robust matching performance and capability for large field-of-view (FOV) imaging. However, the power efficiency of traveling-wave MRI is much lower than conventional methods, which limits its application. One simple approach to improve the power efficiency is to place passive resonators around the subject being imaged. The feasibility of this approach has been demonstrated in previous works using a single small resonant loop. In this work, we aim to explore how much the improvements can be maintained in human imaging using an array design, and whether electric dipoles can be used as local elements. First, a series of electromagnetic (EM) simulations were performed on a human model. Then RF coils were constructed and the simulation results using the best setup for head imaging were validated in MR experiments. By using the passive local loop and transverse dipole arrays, respectively, the transmit efficiency (B) of traveling-wave MRI can be improved by 3-fold in the brain and 2-fold in the knee. The types of passive elements (loops or dipoles) should be carefully chosen for brain or knee imaging to maximize the improvement, and the enhancement depends on the local body configuration.

Copyright © 2017 Elsevier Inc. All rights reserved.

MeSH Terms (11)

Brain Computer Simulation Electromagnetic Radiation Equipment Design Head Humans Knee Joint Magnetic Resonance Imaging Phantoms, Imaging Radio Waves Reproducibility of Results

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