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EMF Study
(Database last updated on Nov 16, 2019)

ID Number 1000
Study Type In Vivo
Model Millimeter-wave band (24.5 - 95 GHz) and 2450 MHz exposure to rabbits (+/- anesthesia) and analysis of ocular effects and dielectric property measurements of ocular tissue up to 110 GHz.
Details

Dutch rabbits (n=43) were exposed to 2.45 GHz MW at 300 mW/cm2 for 60-120 minutes either under anesthesia (ketamine hydrochloride (5 mg/kg, i.m.) + xylazine (0.23 mg/kg, i.m.) or without anesthesia using an open waveguide exposure system located 4cm away from one eye with the animals in restraining tubes. Exposure resulted in average SAR over the exposed whole eye of 108 W/kg, 105 W/kg in the cornea, 141 W/kg in the anterior chamber, 138 W/kg in the lens, 105 W/kg in the vitreous and 75 W/kg in the sclera. Exposure resulted in temporarily inflammation as well as lens changes. These changes were more pronounced in exposed animals given anesthesia. Using both infra-red thermography on exposed rabbit phantoms made from CT images as well as experimental thermometry inserted into the eyes of living rabbits, the investigators also showed that the temperature of the exposed eye in anesthetized rabbits was significantly higher (up to 9°C) than in exposed eyes of non-anesthetized rabbits. The authors point out international exposure guidelines (ICNIRP and IEEE C95.1) limit local SAR based upon research showing cataract formation in the eye due to specific (thermal) levels of RF exposure. Such studies might have been influenced by the use of anesthesia, however. Additional studies are ongoing using lower (ICNIRP and IEEE permissible) exposure levels as well as using higher frequencies (60 GHz at 100 mW/cm2) to see if tissue damage is induced and whether injury from short term exposures can be repaired or reversed. for 60 GHz studies,the authors report miosis and iris vasodilation but no corneal opacity following exposure at 3,000 mW/cm2. Corneal opacification and corneal epithelial damage was seen 1-7 days after exposure. Half of the rabbits in the 1,500 mW/cm2 exposure-group showed the same symptoms as those in the 3,000 mW/cm2 exposure-group. Subsequent studies showed a threshold temperature of 54.2 °C for 6 minutes required for corneal damage and epithelial cell loss, and that different antennas (with different radiation profiles) caused different types of damage with different thresholds. AUTHORS' ABSTRACT: Sasaki, Kojima, Hirata et al. 2014 (IEEE #5801): 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/cm with our exposure system at frequencies from 26.5 to 95 GHz. AUTHORS' ABSTRACT: Sasaki et al. 2015 (IEEE #6130): Measurement of the dielectric properties of ocular tissues up to 110 GHz was performed by the coaxial probe method. A coaxial sensor was fabricated to allow the measurement of small amounts of biological tissues. Four-standard calibration was applied in the dielectric property measurement to obtain more accurate data than that obtained with conventional three-standard calibration, especially at high frequencies. Novel data of the dielectric properties of several ocular tissues are presented and compared with data from the de facto database.

Findings Effects (only at thermal levels)
Status Completed With Publication
Principal Investigator Kanazawa Medical University, Japan - sasaki-k@kanazawa-med.ac.jp
Funding Agency MIC, Japan
Country JAPAN
References
  • Kojima, M et al. Health Phys, (2009) 97:212-218
  • Kojima , M et al. Bioelectromagnetics, (2004) 25:228-233
  • Sasaki, K et al. IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES., (2014) 62:1554-1564
  • Sasaki, K et al. Physics in Medicine and Biology., (2015) 60(16):6273-6288
  • Kojima, M et al. J Infrared Milli Terahz Waves., (2015) 36:390-399
  • Kojima, M et al. J. Infrared Millim. Terahertz Waves., (2018) 39:912-925
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