Compact shielded exposure system for the simultaneous long-term UHF irradiation of forty small mammals II. Dosimetry

A four-antenna collinear array in an electromagnetically shielded chamber w as designed and constructed to preferentially irradiate the brains of a lar ge number of small mammals using cellular telephony microwave signals. Ten animals in special restrainers were positioned symmetrically around a centr ally located antenna. These restrainers are resting on a circular structure made of acrylic plastic called a "carousel." Four carousels are stacked ve rtically, forming the array, inside a microwave anechoic chamber called a " chamberette." (Details of the design of this irradiator and of a 12-chamber ette irradiation facility are given in a previous article.) In this article , the dosimetry on rats is reported. Both thermometric and thermographic me asurements were performed. The average specific absorption rate (SAR) in br ain tissue measured thermometrically was 0.85 +/- 0.34 W/kg per watt of net input power into the radiating antenna. This range agrees with the SAR lev els reported in the Literature for cellular telephones. Thermographic evalu ation using splittable phantoms showed that most of the energy absorbed by the rats is concentrated in and around the brain. Moreover, it was found th at the SAR in brain tissue can vary considerably for rats of similar weight s, depending on position of the rats' heads inside the restrainers, and tha t there exists a significant dependence of SAR on animal weight. These vari ations may be of importance in the interpretation of results of life-long s tudies. The data presented clearly show that the chamberette is, dosimetric ally, a suitable irradiation system for electromagnetic bioeffects studies in the cellular communication frequency range, especially when a large numb er of laboratory animals is required. (C) 1999 Wiley-Liss, Inc.