Compressed perovskite aqueous mixtures near their phase transitions show very high permittivities: New prospects for high‐field MRI dielectric shimming

Abstract

This new preparation method allows improved pad geometry and placement, as a result of the high relative permittivity values achieved. This method has great significance for medical applications of MRI dielectric shimming, being easy to replicate and implement on a large scale. Magn Reson Med 79:1753-1765, 2018. © 2017 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.

Kerker Effect in Ultrahigh-Field Magnetic Resonance Imaging

“…Once again, the characteristic inhomogeneous rf field pattern is obtained. The permittivity of the BaTiO 3 mixture designed is close to ϵ r ¼ 220, which is optimal for a 1-cm-thick pad [5]. The mixture is sealed in a plastic box of dimensions 12 × 10 × 1 cm 3 and placed on the righthand side of the SAM phantom.…”

“…Different approaches have been proposed to tackle this problem. The first one consists of using high dielectric constant pads surrounding the region of interest to locally enhance the rf field [4,5]. Unfortunately, major drawbacks prevent their use in high-field clinical routine: performance decay over time and ecotoxicity of the active substances used conventionally [6].…”

Mitigation of B1+ inhomogeneity for ultra-high-field magnetic resonance imaging: hybrid mode shaping with auxiliary EM potential

“…Dielectric pads filled with water (ε ~ 78 at 300 MHz) placed in contact with the head have been used to improve the sensitivity of the signal in the peripheral region of the ROI (region of interest), especially in proximity to the high permittivity pads 18 . Pads of mixtures of metal titanate and water have been employed to increase the permittivity of the pads so that they can be used in similar strategies [19][20][21][22][23][24] have also been reported to manipulate field profiles at subwavelength scales 25,26 . However, while successful in controlling the field distribution, most of the past efforts utilizing the local enhancement of B 1 + in the vicinity of the pad structures, especially those in contact with the body, often resulted in deterioration of the global B 1 + homogeneity over the ROI.…”

Enhancement of transmit and receive efficiencies with hybridized meta-atom in 7T head coil array

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B1 + heterogeneity remains an important challenge for ultra-high field MRI scanners (B0≥7T). There are two methods to mitigate this problem: parallel transmission pTx [1], and passive shimming using highdielectric pads [2], in this paper we will focus on passive shimming.High-dielectric constant pads have been proposed and optimized for passive shimming purposes [2][3][4]. Common formulations of dielectric pads for 7T applications are based on BaTiO3 mixed with water present some drawbacks such as performance decay over time.

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“…High-dielectric constant pads have been proposed and optimized for passive shimming purposes [2][3][4]. Common formulations of dielectric pads for 7T applications are based on BaTiO3 mixed with water present some drawbacks such as performance decay over time.…”