Exposure Functions for Uniform Dosimetry in Rats at 902 MHz and 1747 MHz

Introduction: Lifespan exposure at uniform dose is one of the basic requirement in the PERFORM A project. PERFORM A consists of two "classical" combined chronic toxicity and carcinogenicity two-year bioassays conducted at RCC Ltd, Switzerland at both GSM frequency bands (GSM900 and DCS1800) as well as a co-carcinogenicity study using DMBA induced Sprague Dawley rats at GSM900 at ARCS, Austria. An additional co-carcinogenicity study using DMBA induced Sprague Dawley rats will be carried out simultaneously at Hangzou University, China. Objectives: The objective of this study was to assess the incident exposures for 902MHz and 1747MHz as function of sex, age and weight in order to minimize the variations of whole-body as well as organ based SAR levels for uniform dosimetry during the 2-year exposure period starting at the age of 5-8 weeks. Methods: The evaluation of the setup was performed by numerical dosimetry using the FDTD simulation platform SEMCAD. The animal phantoms generated for the purpose of this study were 1) male Sprague Dawley of age 7weeks weight 200g (slice separation of 0.575mm), 2) pregnant female Sprague Dawley of weight 275g (slice separation of 0.595mm), 3) male Sprague Dawley of weight 370g (slice separation of 3mm), 4) female Sprague Dawley with a mammary tumor in plum, weight 500g (slice separation of 0.53mm) and 5) male Sprague Dawley of weight 566g (slice separation of 0.525). Up 100 different regions were discriminated. SEMCAD was extended to automatically assess the averaged, maximum, minimum SAR values for whole-body as well as every organ and tissues respectively. In addition, the values for the spatial peak SAR averaged over 0.01g, 0.1g and 1g were compared. In the first step, detailed but numerically optimized models of the two physical exposure setups were generated. They were optimized with respect to accuracy and numerical efficiency. In the second step, these numerical setups were extensively validated by comparing the performances with detailed measurements of the two physical setups using different dummy rats in two different setup configurations: (A) synthetic as symmetrical phantoms and (B) restraining tubes as rat-like phantoms. The experimental evaluations had been conducted using the near-field scanner DASY4 equipped with the latest probe technology as well temperature measurements. In the third step, the detailed rat phantoms were placed in the setup representing averaged positions and postures in the restraining tubes. Result and Conclusions: The whole-body and organ averaged SAR as function of age and weight are not identical requesting a compromise. On the other hand, the differences between the sexes are only minor. These findings enabled to implement a power control function to adjust the incident field depending on the animal weight in order to guarantee fairly uniform exposure during the entire lifespan of the animal. Acknowledgment: The study was supported by the 5th Framework Program of the European Union, the Swiss Government (BBW), the Mobile Manufacturers Forum (MMF) and the GSM Association.