For a human head model, plots of (a) geometry of the problem showing the heat source (white box) within the head (the 3-D geometry and the cross section are the same as Fig. 2), (b) unaveraged SAR distribution, (c) 10 g average SAR distribution(4 min computation time), (d) temperature increase calculated with a rigorous FD algorithm (15 min heating time, 23 min computation time), (e) temperature increase calculated with the proposed rapid digital filter algorithm (15 min heating time, 25 s computation time), and (f) difference maps between the full FD method and the proposed method. The chosen time interval is tint = 30 s, the meshgrid resolution is 2 mm × 2 mm × 2 mm, and the matrix size is 150 × 140 × 120 cells.