Yukihisa Suzuki

Intercomparison of induced fields in Japanese male model for ELF magnetic field exposures: effect of different computational methods and codes

The present study provides an intercomparison of the induced quantities in a human model for uniform magnetic field exposures at extremely low frequency. A total of six research groups have cooperated in this joint intercomparison study. The computational conditions and numeric human phantom including the conductivity of tissue were set identically to focus on the uncertainty in computed fields. Differences in the maximal and 99th percentile value of the in situ electric field were less than 30 and 10 % except for the results of one group. Differences in the current density averaged over 1 cm(2) of the central nerve tissue are 10 % or less except for the results of one group. This comparison suggests that the computational uncertainty of the in situ electric field/current density due to different methods and coding is smaller than that caused by different human phantoms and the conductivitys of tissue, which was reported in a previous study.

Effects of 2.45-GHz Electromagnetic Fields with a Wide Range of SARs on Micronucleus Formation in CHO-K1 Cells

There has been considerable discussion about the influence of high-frequency electromagnetic fields (HFEMF) on the human body. In particular, HFEMF used for mobile phones may be of great concern for human health. In order to investigate the properties of HFEMF, we have examined the effects of 2.45-GHz EMF on micronucleus (MN) formation in Chinese hamster ovary (CHO)-K1 cells. MN formation is induced by chromosomal breakage or inhibition of spindles during cell division and leads to cell damage. We also examined the influence of heat on MN formation, since HFEMF exposure causes a rise in temperature. CHO-K1 cells were exposed to HFEMF for 2 h at average specific absorption rates (SARs) of 5, 10, 20, 50, 100, and 200 W/kg, and the effects on these cells were compared with those in sham-exposed control cells. The cells were also treated with bleomycin alone as a positive control or with combined treatment of HFEMF exposure and bleomycin. Heat treatment was performed at temperatures of 37, 38, 39, 40, 41, and 42°C.The MN frequency in cells exposed to HFEMF at a SAR of lower than 50 W/kg did not differ from the sham-exposed controls, while those at SARs of 100 and 200 W/kg were significantly higher when compared with the sham-exposed controls. There was no apparent combined effect of HFEMF exposure and bleomycin treatment. On heat treatment at temperatures from 38–42°C, the MN frequency increased in a temperature-dependent manner. We also showed that an increase in SAR causes a rise in temperature and this may be connected to the increase in MN formation generated by exposure to HFEMF.

Acute Ocular Injuries Caused By 60-ghz Millimeter-wave Exposure

The goal of this study was to examine the clinical course of 60-GHz millimeter-wave induced damages to the rabbit eye and to report experimental conditions that allow reproducible induction of these injuries. The eyes of pigmented rabbits (total number was 40) were irradiated with 60-GHz millimeter-waves using either a horn antenna or one of two lens antennas (6 and 9 mm diameter; ϕ6, ϕ9) Morphological changes were assessed by slit-lamp microscopy. Additional assessments included corneal fluorescein staining, iris fluorescein angiography, and lens epithelium light microscopy. Under the standardized eye-antenna positioning, the three antennas caused varying damages to the eyelids or eyeglobes. The most reproducible injuries without concurrent eyelid edema and corneal desiccation were achieved using the ϕ6 lens antenna: irradiation for 6 min led to an elevation of the corneal surface temperature (reaching 54.2 ± 0.9°C) plus corneal edema and epithelial cell loss. Furthermore, mitotic cells appeared in the pupillary area of the lens epithelium. Anterior uveitis also occurred resulting in acute miosis (from 6.6 ± 1.4 to 2.2 ± 1.4 mm), an increase in flares (from 6.7 ± 0.9 to 334.3 ± 130.8 photons per second), and iris vasodilation or vessel leakage. These findings indicate that the three types of millimeter-wave antennas can cause thermal injuries of varying types and levels. The thermal effects induced by millimeter-waves can apparently penetrate below the surface of the eye.

Imaging the 3D temperature distributions caused by exposure of dielectric phantoms to high-frequency electromagnetic fields

A new method of measuring the temperature distribution due to high frequency electromagnetic field (HF-EMF) power absorption is established. The method is applied to the measurement of the spatial distribution of specific absorption rate (SAR) in tissue exposed to HF-EMF. A microencapsulated thermotropic liquid crystal (MTLC) is employed as the temperature probe because of high resolution and high sensitivity. A high-molecular gel phantom with a high transparency and a high viscosity is developed to realize visualization technique with MTLC. The complex permittivity of the phantom is adjusted to that of muscle at 900 MHz and 1.45 GHz. This method is proven to be efficient in visualizing HF-EMF power absorption by exposure experiment

Effects of 21-kHz intermediate frequency magnetic fields on blood properties and immune systems of juvenile rats

Abstract Purpose: Due to a lack of science-based evidence, we explored the effects of exposure to intermediate frequency magnetic fields (IF-MF) on experimental animals. We assessed several immunological parameters to determine the effect of exposure of the whole body to IF-MF. Materials and methods: Male Sprague-Dawley rats (4–5 weeks old) were divided into three groups: Cage-control, sham, and 3.8-mT (rms) exposure groups. The animals were exposed to IF-MF at 21 kHz under fixed conditions in an acrylic holder. Exposure was performed for 1 h/day for 14 consecutive days. On the 15th day following the exposure, biochemical and hematological parameters in blood were analyzed. The effects of the exposure on immunological functions such as the cytotoxic activity of lymphocytes, chemotactic and phagocytic activity of granulocytes, and T (cluster of differentiation 4 [CD4] and cluster of differentiation 8 [CD8])-cell frequency were also examined. Results: Hematological parameters were not affected by IF-MF exposure. Other immune functions such as the cytotoxic activity and phagocytic activity were not affected. Populations of T cells after exposure also did not show any significant differences. In blood biochemistry, there was significant difference in inorganic phosphorus level between sham and exposure group. However, this will not induce any pathophysiological status, because they were still within physiological range. Overall, no significant effect by exposure of IF-MF was observed under our experimental conditions. Conclusions: Our results suggest that exposure to 21-kHz sinusoidal IF-MF at 3.8 mT for 1 h/day for 14 days did not affect immune function in juvenile rats.

Dosimetry Using a Localized Exposure System in the Millimeter-Wave Band for in vivo Studies on Ocular Effects

We developed a millimeter-wave (MMW) exposure system for in vivo experiments for operating frequencies ranging from 24.5 to 95 GHz. The MMWs are localized to the rabbit ocular tissue with a spot-focus lens antenna. The MMW energy absorption and consequent temperature elevation are evaluated by numerical simulation using measured antenna distribution and precisely modeled rabbit ocular data. Results suggest that corneal damage occurs at an incident power density of 300 mW/cm2 with our exposure system at frequencies from 26.5 to 95 GHz.

Evaluation of biological effects of intermediate frequency magnetic field on differentiation of embryonic stem cell

The embryotoxic effect of intermediate frequency (IF) magnetic field (MF) was evaluated using murine embryonic stem (ES) cells and fibroblast cells based on the embryonic stem cell test (EST). The cells were exposed to 21 kHz IF–MF up to magnetic flux density of 3.9 mT during the cell proliferation process (7 days) or the cell differentiation process (10 days) during which an embryonic body differentiated into myocardial cells. As a result, there was no significant difference in the cell proliferation between sham- and IF–MF-exposed cells for both ES and fibroblast cells. Similarly, the ratio of the number of ES-derived cell aggregates differentiated to myocardial cells to total number of cell aggregates was not changed by IF–MF exposure. In addition, the expressions of a cardiomyocytes-specific gene, Myl2, and an early developmental gene, Hba-x, in the exposed cell aggregate were not altered. Since the magnetic flux density adopted in this study is much higher than that generated by an inverter of the electrical railway, an induction heating (IH) cooktop, etc. in our daily lives, these results suggested that IF–MF in which the public is exposed to in general living environment would not have embryotoxic effect.

Design and implementation of multi-frequency magnetic field generator producing sinusoidal current waveform for biological researches

Recently, induction heating systems are being widely used in many applications, and wireless power transmission systems are being introduced into commercially available electrical vehicles. These applications use time varying magnetic fields (under 100 kHz) which are in close proximity of the human body. Therefore, it should be discussed an influence of the time varying magnetic fields around 100 kHz to the human body. This paper presents design and implementation of a magnetic field generator for biological research. While conventional magnetic field generators only produce one frequency component, this paper discusses a multi-frequency range magnetic field generator with frequencies of 200 Hz and 20 kHz. In addition, actual systems with the inverter circuits for the purpose of biological evaluation are presented.

Electromagnetic and Thermal Dosimetry of a Cylindrical Waveguide-Type in vitro Exposure Apparatus

In this paper, dosimetry of an in vitro exposure apparatus based on a cylindrical waveguide is performed. The SAR distributions are first obtained numerically by using FDTD method. The thermal fields in the medium are then estimated by numerical calculations of the equation of heat conduction. The maximum temperature rise for 17.9 W/kg average SAR during 3000 s exposure is about 2°C on the bottom of the medium where cells are located. The thermal distribution is relatively uniform new the center of the dish and the temperature in this region is around 38.7°C. The results of the numerical calculation are experimentally supported. The results provide the electromagnetic and thermal characteristics of the exposure apparatus, which will define the exposure conditions of the planned experiments using this apparatus.

High-Efficiency Applicator Based on Printed Circuit Board in Millimeter-Wave Region

The purpose of this study is to develop a novel in vitro millimeter-wave (MMW) applicator for an exposure apparatus that allows high power efficiency with reasonably good homogeneity over a sufficient exposure area, as well as the capability of temperature control in biological samples. The applicator is made of a printed circuit board and has a large and circular (90-mm diameter) exposure area that is fed with MMWs using post-wall waveguide technology. The applicator is designed for the exposure of cells to MMWs at 60 GHz. The proposed applicator has an absorption efficiency of 54%, where the absorption efficiency is defined as the ratio of the total power absorbed in the culture medium to the input power. Its efficiency is higher than those of other apparatuses operating at 60 GHz reported in the literature. Most of the cells (89%) are located within the ±5-dB region relative to the average specific absorption rate, which shows reasonably good homogeneity compared with previously reported literature data. The applicator enables efficient temperature control for in vitro experiments to explore unknown and possible nonthermal effects of MMW exposures.