Exposure setup to test effects of wireless communications systems on the CNS

This paper presents an exposure setup designed for in vivo studies of possible effects on the central nervous system due to the electromagnetic exposure from handheld mobile communications equipment. The setup consists of a carousel on which 10 rats, each restrained in a radially positioned tube, are exposed to the electromagnetic field emanating from a dipole antenna at the center. The rats are positioned with their snouts at a distance of 35 mm from the dipole antenna. The tubes restrain the movement of the animals to such an extent as to allow for well defined exposure conditions, yet without totally immobilizing them. Numerical and experimental dosimetric analysis of the setup was conducted using rats weighing 250-300 g at a frequency of 900 MHz. A detailed rat phantom derived from MRI scans was developed for the numerical assessment with a commercially available code based on the finite integration technique. The results were validated by measurements of the temperature rise in selected points of a rat cadaver. The dosimetric analysis shows that the setup is eminently suitable for central nervous system studies. It enables well defined field strengths to be induced in the brain tissue, whereby the variations in the specific absorption rate averaged over the brain tissue caused by movement and varying animal sizes was shown to be less than +/-16%. The specific absorption rate distribution in the brain is nonhomogeneous but comparable to that induced in the brain of a human using a handheld wireless phone. The efficiency of the exposure is about 0.20+/-0.05 mW g(-1) for the brain average value per 100 mA feedpoint current. The whole-body average specific absorption rate is considerably lower, i.e., about half of that of the brain averaged value. In addition, the setup has been proven to be practical in use, and the stress levels caused by restraining the animals in this setup are deemed by neurologists and veterinary scientists to be very low.