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High Permittivity Dielectric Pads Improve High Spatial Resolution Magnetic Resonance Imaging of the Inner Ear at 7 T

Brink, Wyger M. MSc*; van der Jagt, Annerie M.A. MD; Versluis, Maarten J. PhD*; Verbist, Berit M. MD; Webb, Andrew G. PhD*

doi: 10.1097/RLI.0000000000000026
Original Articles
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Objectives The objective of this study was to evaluate the use of dielectric pads for improving high spatial resolution imaging of the inner ear at 7 T.

Materials and Methods Two sets of dielectric pads were designed using electromagnetic simulations and implemented using a deuterated suspension of barium titanate. Their effect on transmit efficiency, contrast homogeneity, and diagnostic image quality was evaluated in vivo (N = 10). In addition, their effect on the specific absorption rate was evaluated numerically.

Results Statistically significant improvements (P < 0.001) in several measures of the image quality were obtained by using dielectric pads. The dielectric pads lead to an increase in the transmit efficiency and uniformity at the location of the inner ear, which is reflected in both an increased contrast homogeneity and an increased diagnostic value. Simulations show that the dielectric pads do not increase the peak local specific absorption rate.

Conclusions Using geometrically tailored dielectric pads enables high spatial resolution magnetic resonance imaging of the human inner ear at 7 T. The high spatial resolution improves the depiction of the fine inner ear structures, showing the benefit of magnetic resonance imaging at ultrahigh fields.

From the *C.J. Gorter Center for High Field MRI, Department of Radiology, †Department of Otorhinolaryngology-Head and Neck Surgery, Leiden University Medical Center, Leiden, and ‡Department of Radiology, Leiden University Medical Center, Leiden and Radboud University Medical Center, Nijmegen, The Netherlands.

Received for publication July 1, 2013; and accepted for publication, after revision, November 9, 2013.

Conflict of interest and sources of funding: Supported by the Dutch Organization for Scientific Research (Nederlandse Organisatie voor Wetenschappelijk Onderzoek) project number 176.010.2005.030.

Author Webb has received a TOP grant from Nederlandse Organisatie voor Wetenschappelijk Onderzoek. The other authors have no conflicts of interest and sources of funding to declare.

Reprints: Andrew G. Webb, PhD, C.J. Gorter Center for High Field MRI, Department of Radiology, Postzone C3-Q, Leiden University Medical Center, Albinusdreef 2, 2333 ZA, Leiden, The Netherlands. E-mail: a.webb@lumc.nl.

© 2014 by Lippincott Williams & Wilkins