RF fields induced during MRI in a heterogeneous human head model

Results from numerical calculations of the radiofrequency electromagnetic fields induced in the human head during magnetic resonance imaging (MRI) of the head at frequencies from 63 to 200 MHz are presented. Numerical values are given in a form that can easily be used to determine specific SAR levels for any MRI procedures at these frequencies. Maximum local SAR levels are lower at lower frequencies, in circularly- than in linearly-polarized fields, and in linearly-polarized fields polarized posterior-to-anterior than left-to-right in the head model. Magnetic field homogeneity and signal-to-noise ratio are greater at lower frequencies and in circularly-polarized fields