Comparison of 2D and 3D models of the human head surrounded by a dielectric sheet in MRI scans

A sheet of high dielectric constant surrounding the head has been used in MRI scans to improve signal-to-noise ratio and lower the power transmitted by the array of coils. In a study presented at the URSI General Assembly and Scientific Symposium, Beijing, China, August 2014, we have presented a two-dimensional model in which the human head is simulated by a cylinder with appropriate uniform dielectric constant and conductivity, surrounded by a dielectric sheet of high permittivity and illuminated by an array of line sources. We proved that under appropriate excitation of the array elements, the electric field is zero and the magnetic field is locally maximum and circularly polarized on the axis of the structure.