Segmented RF shield design to minimize eddy currents for low-field Halbach MRI systems

Journal of Magnetic Resonance, vol. 362, pp. 107669

Abstract

MRI systems have a thin conducting layer placed between the gradient and RF coils, this acts as a shield at the RF-frequency, minimizing noise coupled into the experiment, and decreasing the coupling between the RF and gradient coils. Ideally, this layer should be transparent to the gradient fields to reduce eddy currents. In this work the design of such a shield, specifically for low-field point-of-care Halbach based MRI devices, is discussed. A segmented double layer shield is designed and constructed based on eddy current simulations. Subsequently, the performance of the improved shield is compared to a reference shield by measuring the eddy current decay times as well as using noise measurements. A maximum reduction factor of 2.9 in the eddy current decay time is observed. The segmented shield couples in an equivalent amount of noise when compared to the unsegmented reference shield. Turbo spin echo images of a phantom and the brain of a healthy volunteer show improvements in terms of blurring using the segmented shield.

Authors 3

1. Bart de Vos corresponding Aachen C.J. Gorter MRI Center

   Leiden University · Leiden University Medical Center · Delft University of Technology

   Affiliation as printed

   C.J. Gorter MRI center, Radiology, Leiden University Center, Leiden, The Netherlands; Terahertz Sensing, Microelectronics, Delft University of Technology, Delft, The Netherlands. Electronic address: b.devos26.07@gmail.com

   C.J. Gorter MRI center, Radiology, Leiden University Center, Leiden, The Netherlands

   Terahertz Sensing, Microelectronics, Delft University of Technology, Delft, The Netherlands

2. Rob Remis

   Delft University of Technology

   Affiliation as printed

   Terahertz Sensing, Microelectronics, Delft University of Technology, Delft, The Netherlands

3. ANDREW G. WEBB Aachen C.J. Gorter MRI Center

   Leiden University · Leiden University Medical Center · Delft University of Technology

   Affiliation as printed

   C.J. Gorter MRI center, Radiology, Leiden University Center, Leiden, The Netherlands; Terahertz Sensing, Microelectronics, Delft University of Technology, Delft, The Netherlands

   C.J. Gorter MRI center, Radiology, Leiden University Center, Leiden, The Netherlands

   Terahertz Sensing, Microelectronics, Delft University of Technology, Delft, The Netherlands