In this study, we develop a numerical method for determining transient energy deposition in biological bodies exposed to electromagnetic (EM) pulses. We use a newly developed frequency-dependent finite-difference time-domain (FD2TD) method, which is combined with the fast inverse Laplace transform (FILT) and Prony method. The FILT and Prony method are utilized to transform the Cole-Cole model of biological media into a sum of multiple Debye relaxation terms. Parameters of Debye terms are then extracted by comparison with the time-domain impulse responses. The extracted parameters are used in an FDTD formulation, which is derived using the auxiliary differential equation method, and transient energy deposition into a biological medium is calculated by the equivalent circuit method. The validity of our proposed method is demonstrated by comparing numerical results and those derived from an analytical method. Finally, transient energy deposition into human heads of TARO and HANAKO models is then calculated using the proposed method and, physical insights into pulse exposures of the human heads are provided.
Many millimeter-wave exposure experiments using animals have been performed in order to investigate the possible health effects in the past but a few of them could provide dosimetry analysis. In this paper, we apply the Poggio-Miller-Chang-Harrington-Wu-Tsai method of moments to investigate differences in the absorbed power distribution due to three different exposure conditions; a rabbit head phantom exposed to an electromagnetic (EM) plane wave, and that exposed to EM fields radiated from a horn or a dielectric lens antenna at 40 GHz. We determined the power density absorbed into the region of the rabbit eye for each situation. The results showed that the dielectric lens antenna can be used to illuminate effectively the rabbit eye. It was found that nearly 65% of EM power applied into the antenna port can be effectively delivered to the rabbit eye.
In this paper, numerical dosimetry on induced current density inside a human body, exposed to magnetic fields due to an induction heating (IH) cooker, is performed by the impedance method (IM). The magnetic flux density distribution, which is obtained by a magnetic probe, is used for the incident magnetic field in IM. Induced current distributions for two voxel models of the average Japanese adult male and female are obtained. These results indicate that hot spots of induced current density are observed at a few cm inside from the surface of the two models because of inhomogeneous conductivity of the tissues. The maximum value of current density inside the male model is larger than that inside the female model.
In this study, we investigated whether exposure to 2450 MHz high-frequency electromagnetic fields (HFEMFs) could act as an environmental insult to evoke a stress response in A172 cells, using HSP70 and HSP27 as stress markers. The cells were exposed to a 2450 MHz HFEMF with a wide range of specific absorption rates (SARs: 5-200 W/kg) or sham conditions. Because exposure to 2450 MHz HFEMF at 50-200 W/kg SAR causes temperature increases in culture medium, appropriate heat control groups (38-44 degrees C) were also included. The expression of HSP 70 and HSP 27, as well as the level of phosphorylated HSP 27 ((78)Ser) (p-HSP27), was determined by Western blotting. Our results showed that the expression of HSP 70 increased in a time and dose-dependent manner at >50 W/kg SAR for 1-3 h. A similar effect was also observed in corresponding heat controls. There was no significant change in HSP 27 expression caused by HFEMF at 5-200 W/kg or by comparable heating for 1-3 h. However, HSP 27 phosphorylation increased transiently at 100 and 200 W/kg to a greater extent than at 40-44 degrees C. Phosphorylation of HSP 27 reached a maximum after 1 h exposure at 100 W/kg HFEMF. Our results suggest that exposure to a 2450 MHz HFEMF has little or no apparent effect on HSP70 and HSP27 expression, but it may induce a transient increase in HSP27 Phosphorylation in A172 cells at very high SAR (>100 W/kg).
