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MAGMA. 2018 Jun;31(3):355-366. doi: 10.1007/s10334-017-0657-5. Epub 2017 Nov 6.

Manipulating transmit and receive sensitivities of radiofrequency surface coils using shielded and unshielded high-permittivity materials.

Author information

1
Center for Advanced Imaging Innovation and Research and the Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, 660 First Ave, Fourth Floor, New York, NY, 10016, USA. mvv218@nyu.edu.
2
The Sackler Institute of Graduate Biomedical Sciences, New York University School of Medicine, 550 First Avenue, New York, NY, 10016, USA. mvv218@nyu.edu.
3
NYU WIRELESS, 2 Metro Tech Center, Brooklyn, NY, 11201, USA. mvv218@nyu.edu.
4
Center for Advanced Imaging Innovation and Research and the Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, 660 First Ave, Fourth Floor, New York, NY, 10016, USA.
5
NYU WIRELESS, 2 Metro Tech Center, Brooklyn, NY, 11201, USA.
6
The Sackler Institute of Graduate Biomedical Sciences, New York University School of Medicine, 550 First Avenue, New York, NY, 10016, USA.

Abstract

OBJECTIVE:

To use high-permittivity materials (HPM) positioned near radiofrequency (RF) surface coils to manipulate transmit/receive field patterns.

MATERIALS AND METHODS:

A large HPM pad was placed below the RF coil to extend the field of view (FOV). The resulting signal-to-noise ratio (SNR) was compared with that of other coil configurations covering the same FOV in simulations and experiments at 7 T. Transmit/receive efficiency was evaluated when HPM discs with or without a partial shield were positioned at a distance from the coil. Finally, we evaluated the increase in transmit homogeneity for a four-channel array with HPM discs interposed between adjacent coil elements.

RESULTS:

Various configurations of HPM increased SNR, transmit/receive efficiency, excitation/reception sensitivity overlap, and FOV when positioned near a surface coil. For a four-channel array driven in quadrature, shielded HPM discs enhanced the field below the discs as well as at the center of the sample as compared with other configurations with or without unshielded HPM discs.

CONCLUSION:

Strategically positioning HPM at a distance from a surface coil or array can increase the overlap between excitation/reception sensitivities, and extend the FOV of a single coil for reduction of the number of channels in an array while minimally affecting the SNR.

KEYWORDS:

Computer Simulation; Electromagnetic Fields; Magnetic Resonance Imaging

PMID:
29110240
PMCID:
PMC5936683
DOI:
10.1007/s10334-017-0657-5
[Indexed for MEDLINE]
Free PMC Article

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