Dosimetric analysis of a 900-MHz rat head exposure system

This paper describes a dosimetric analysis of a specific exposure system used to locally expose the heads of rats. This system operating at 900 MHz consists of a restrainer and a loop antenna having two metallic lines printed on a dielectric substrate; one of the extremities of the metallic structure forms a loop and is placed close to the head of the animal placed in a cylindrical "rocket-like" restrainer. This local-exposure system was analyzed using the finite-difference time-domain method. Comparisons between measurements and simulations were carried out using a homogeneous rat model. The aim of the study was to compare the exposure of the rat and human head in specific tissues such as the dura matter (DM). Specific absorption rate (SAR) levels were calculated in a heterogeneous rat phantom. With an input power of 1 W, the brain-averaged SAR was equal to 6.8 W/kg. Using a statistical approach, the maximum SAR in specific tissues was extracted. With an input power of 1 W, the maximum SAR inside the skull was estimated at 15.5+/-5 W/kg, while the maximum SAR in the skin was 33+/-5 W/kg. A comparison was made between SAR levels in a human head exposed to a global system for mobile communication handset operating at 900 MHz (250-mW output power) and those obtained in the rat tissues with a 100-mW input power at the connector of the loop. In this case, simulations showed that the ratio of the maximum local SAR in the rat versus human was 1.3+/-0.6 in the brain, 1.0+/-0.5 in the skin, and 1.2+/-0.6 in the DM.