Flexible, Stretchable, and MR-Invisible Dielectric Material for Magnetic Resonance Imaging

Abstract

Flexible, stretchable, and MR-invisible dielectric materials were studied to increase the local magnetic field (B ₁ ) and signal-to-noise ratio (SNR) in magnetic resonance imaging. An electromagnetic simulation was performed with different dielectric constants and physical structures to measure the effects on the magnetic field (H) distribution and the specific absorption rate (SAR). After flexible and stretchable dielectric pads composed of silicon carbide (SiC)- and barium titanate (BaTiO ₃ )-based polymer mixtures were fabricated, MR imaging tests with two isotropic phantoms and an oxtail sample were performed in a preclinical 7 T scanner (BioSpec scanner, Bruker). The B ₁ field intensities and SNR were compared with a reference image. Also, additional noise and image artifacts were evaluated. Simulation results show that wrapping an object with a dielectric material is the most effective method to increase the intensity and uniformity of the H field. The results of MR imaging consistently show a higher B ₁ field intensity and SNR when utilizing dielectric materials. An improvement of 25.78% and 18.27% in SNR was observed when SiC- and BaTiO ₃ -based dielectric pads were wrapped around an oxtail, respectively. In this work, the first stretchable dielectric materials with MR-invisibility were developed, and their performance was demonstrated with 7 T MR imaging.