Numerical simulation of SAR and B/sub 1/-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.