Geometrically Stochastic FDTD Method for Uncertainty Quantification of EM Fields and SAR in Biological Tissues

This paper presents a stochastic scheme called geometrically stochastic finite-difference time domain (GS-FDTD) to insert the statistical variation of model geometry directly into the FDTD method. Both 1-D and 2-D GS-FDTD formulations are presented. The method is utilized to investigate the impact of tissue size variation on the calculated EM fields in 1-D and 2-D layered and cylindrical biological models. In addition, we assess the specific absorption rate (SAR) variance in a 2-D slice of a human head model at 835 MHz with the size of the outer layer consisting of skin, ear, and nose varying ±10%. Also, an improved method of calculating SAR variance is presented. The results are verified using the Monte Carlo technique.