Improvement of Electromagnetic Field Distributions Using High Dielectric Constant (HDC) Materials for CTL-Spine MRI: Numerical Simulations and Experiments

This study investigates the use of pads with high dielectric constant (HDC) materials to alter electromagnetic field distributions in patients during magnetic resonance imaging (MRI). The study was performed with numerical simulations and phantom measurements. An initial proof-of-concept and validation was performed using a phantom at 64 MHz, showing increases of up to 10% in electromagnetic field when using distilled water as the high dielectric material. Additionally, numerical simulations with computational-models of human anatomy were performed at 128 MHz. Results of these simulations using barium titanate (BaTiO3) beads showed a 61% increase of vertical bar B-1(+)vertical bar with a quadrature driven RF coil and a 64% increase with a dual-transmit array. The presence of the HDC material also allowed for a decrease of SAR up to twofold (e.g., peak 10 g-averaged SAR from 54 to 22 W/kg with a quadrature driven RF coil and from 27 to 22 W/kg with a dual-transmit array using CaTiO3 powder at 128 MHz). The results of this study show that the use of HDC pads at 128 MHz for MRI spine applications could result in improved magnetic fields within the region of interest, while decreasing SAR outside the region.