Numerical simulation of SAR and B1-field inhomogeneity of shielded RF coils loaded with the human head

The finite-difference time-domain (FDTD) method is combined with the method of moments (MoM) to compute the electromagnetic fields of shielded radio frequency (RF) coils loaded with an anatomically accurate model of a human head for high-frequency magnetic resonance imaging (MRI) applications. The combined method can predict both the specific energy absorption rate (SAR) and the magnetic field (known as the B-1 field) excited by any RF coils. Results for SAR and B-1 field distribution, excited by shielded and end-capped birdcage coils, are calculated at 64, 128, 171, and 256 MHz, The results show that the value of SAR increases when the frequency of the B-1 field increases and the B-1 field exhibits a strong inhomogeneity at high frequencies.