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Simulations of high permittivity materials for 7 T neuroimaging and evaluation of a new barium titanate‐based dielectric
Author(s) -
Teeuwisse W. M.,
Brink W. M.,
Haines K. N.,
Webb A. G.
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.24176
Subject(s) - barium titanate , permittivity , relative permittivity , dielectric , materials science , neuroimaging , magnetic resonance imaging , nuclear magnetic resonance , dielectric permittivity , barium , dielectric loss , image quality , computer science , acoustics , optoelectronics , physics , image (mathematics) , medicine , radiology , artificial intelligence , psychology , neuroscience , metallurgy
High permittivity “dielectric pads” have been shown to increase image quality at high magnetic fields in regions of low radiofrequency transmit efficiency. This article presents a series of electromagnetic simulations to determine the effects of pad size and geometry, relative permittivity value, as well as thickness on the transmit radiofrequency fields for neuroimaging at 7 T. For a 5‐mm thick pad, there is virtually no effect on the transmit field for relative permittivity values lower than ∼90. Significant improvements are found for values between 90 and ∼180. If the relative permittivity is increased above ∼180 then areas of very low transmit efficiency are produced. For a 1‐cm thick pad, the corresponding numbers are ∼60 and ∼120, respectively. Based upon the findings, a new material (barium titanate, relative permittivity ∼150) is used to produce thin (∼5 mm) dielectric pads which can easily be placed within a standard receive head array. Experimental measurements of transmit sensitivities, as well as acquisition of T 2 ‐ and T 2 * ‐weighted images show the promise of this approach. Magn Reson Med, 2012. © 2012 Wiley Periodicals, Inc.