Flexible metasurface for improving brain imaging at 7T

Magnetic Resonance in Medicine, vol. 92, pp. 869–880

Abstract

PURPOSE: field inhomogeneity, which results in signal intensity drops in temporal lobes and a bright region in the brain center. This study aims to evaluate using a metasurface to improve brain imaging at 7T and simplify the investigative workflow. METHODS: Two flexible metasurfaces comprising a periodic structure of copper strips and parallel-plate capacitive elements printed on an ultra-thin substrate were optimized for brain imaging and implemented via PCB. We considered two setups: (1) two metasurfaces located near the temporal lobes and (2) one metasurface placed near the occipital lobe. The effect of metasurface placement on the transmit efficiency and specific absorption rate was evaluated via electromagnetic simulation studies with voxelized models. In addition, their impact on signal-to-noise ratio (SNR) and diagnostic image quality was assessed in vivo for two male and one female volunteers. RESULTS: Placement of metasurfaces near the regions of interest led to an increase in homogeneity of the transmit field by 5% and 10.5% in the right temporal lobe and occipital lobe for a male subject, respectively. SAR efficiency values changed insignificantly, dropping by less than 8% for all investigated setups. In vivo studies also confirmed the numerically predicted improvement in field distribution and receive sensitivity in the desired ROI. CONCLUSION: Optimized metasurfaces enable homogenizing transmit field distribution in the brain at 7T. The proposed lightweight and flexible structure can potentially provide MR examination with higher diagnostic value images.

Authors 4

1. Vladislav Koloskov corresponding

   ITMO University

   Affiliation as printed

   School of Physics and Engineering ITMO University St. Petersburg Russia

   School of Physics and Engineering, ITMO University, St. Petersburg, Russia

2. Wyger M. Brink

   University of Twente

   Affiliation as printed

   Magnetic Detection & Imaging Group, TechMed Centre University of Twente Enschede The Netherlands

   Magnetic Detection & Imaging Group, TechMed Centre University of Twente Enschede The Netherlands

3. ANDREW G. WEBB Aachen C.J. Gorter MRI Center Department of Radiology Leiden University Medical Center Leiden The Netherlands Department of Radiology, Leiden University Medical Center

   Leiden University Medical Center

   Affiliation as printed

   C.J. Gorter MRI Center, Department of Radiology Leiden University Medical Center Leiden The Netherlands

   C.J. Gorter MRI Center, Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands

4. Alena V. Shchelokova

   ITMO University

   Affiliation as printed

   School of Physics and Engineering ITMO University St. Petersburg Russia

   School of Physics and Engineering, ITMO University, St. Petersburg, Russia