Concern has been raised in recent years regarding the effect of exposure to electromagnetic fields in the intermediate frequency band on human health. The study of indirect effects, such as contact current hazards, is insufficient. Therefore, the authors have been measuring the current perception threshold in the intermediate frequency range. In this study, a simulation experiment of current perception threshold measurements was conducted to clarify the relationship between the current perception threshold and the current density and/or in situ electric field.
The numerical dosimetry of women during pregnancy is an important issue in electromagnetic field safety. We had developed a whole-body numerical pregnant-woman model at 26-weeks' gestation. In this study, we developed pregnant-woman models that included the inherent tissues of pregnant women adjusted to the standard reference values at 12- and 20-weeks' gestation by deforming the existing pregnant-woman model. We also improved the original 26-weeks' pregnant-woman model so that the masses of inherent pregnancy tissues are adjusted to the standard reference values. The anatomical details of the developed pregnant-woman models and basic SAR characteristics for whole-body exposure to RF electromagnetic fields are described.
The adverse health effects of human exposure to RF-EMFs have become of increasing concern. The safety is evaluated on the basis of the SAR. Variability in the SAR caused by differences in the physical features of real people is one of the several important issues. In this study, we developed the computational human models with different body-types by our proposed volume deformation technique to generate the model from magnetic resonance imaging data of target persons using existing human models. We also demonstrated SAR characteristics in human models with different body-types exposed to vertically and horizontally polarized EM waves ranging from 30 MHz to 6 GHz using the multi-GPU accelerated three-dimensional FDTD solver.
This paper introduced numerical estimations for SAR enhancement in human tissue due to metal plate implants with screw holes. To investigate the impact of the metal implants, we numerically evaluate SAR of human head phantom with complicated shaped metal implants. From the simulation results, SAR enhancement due to the implanted metallic plates was clearly observed at specific frequency. We also achieved temperature increase measurements using translucent solid phantoms in order to confirm validation of the numerical results.
Recently, there has been increasing concern regarding the safety of exposure to RF electromagnetic fields in pregnant females and their fetuses. Therefore, we acquired fetal MRI images from pregnant women during the second and third trimesters of pregnancy and newly developed six fetal computational models at 20, 23, 26, 29, 32 and 33 weeks of pregnancy on the basis of the acquired images. The fetal models consist of about 20 different tissue types. These tissues were segmented by medical staffs using both manual and semiautomatic segmentation techniques from fine-resolution images acquired by 3D-ture FISP (Fast Imaging with State Precession) sequence. The works were performed under the supervision of a pediatric radiologist. The number of tissues and the spatial resolutions of the fetal models are better than those of models previously developed. This paper outlines the high-fidelity computational models of human fetuses during the second and third trimesters of pregnancy.
The standard method for assessing the specific absorption rate of a mobile device involves scanning an electric field probe in a tissue equivalent liquid. The electric field probe is also calibrated in the liquid. Uncertainty of permittivity measurement of the liquid accounts for a large proportion of uncertainty of the specific absorption rate measurement and related probe calibration. The permittivity measurement of the liquid generally employs a coaxial probe method, but its uncertainty tends to be somewhat large because of its reflection measurement. In this paper, we propose a method to estimate the complex permittivity of the liquid from the attenuation and phase constants of the liquid surrounded by the waveguide well and moving the small dipole antenna in it, and show an example of actual measurement.
RF exposure guidelines [1–3] recognize that an increase in local SAR due to metallic implants is possible, depending upon the size and shape of the implant and the position. Some papers regarding interaction of radio frequency (RF) EMF and passive metallic implants have been published [4–5] . This study describes the local SAR calculations for human with metallic osteosynthesis plates embedded in the mandibular zone exposed to RF fields. The main objective is to assess whether combination of two metallic plates aligned in parallel in the head region could be expected to cause SAR enhancements under near-field exposure condition at 2 GHz [6] . In this paper, we achieve temperature distribution measurements for a phantom implanted with osteosynthesis plates. A physical phantom implanted with two metallic plates is developed and thermographic method are used to obtain temperature distribution. The solid phantom was manufactured using silicone rubber and carbon material. The obtained measurement data can be used for validation study for further SAR estimations using numerical analysis. After 10 seconds RF exposure, when the antenna input power was set to be 500 W, the temperature distribution was measured immediately in front of the plate of the phantom. Figure 1 shows example of surface temperature distributions of the phantom. In the temperature distributions, temperature increase due to the metallic plates was clearly observed near the plate region. In addition, the measured result agreed well with numerical simulation result obtained using a commercially available FDTD simulation software [7] . Local SARs for a human model with osteosynthesis plates in the head region were also evaluated. By using an anatomical phantom implanted with metallic plates at the median mandibular, the effect of combination of two metallic implants, were estimated under near-field exposure condition at 2 GHz. The results indicated that the increase rate was 34% under the condition.
