In vitro exposure systems for RF exposures at 900 MHz

In the context of European research programs, a reference setup based on waveguides (WGs) has been developed for the conduct of standardized in vitro experiments at the mobile frequency bands of 835 and 935 MHz. Its performance is compared to apparatus that are widely applied to expose cells settled as a monolayer on the bottom of a Petri dish, as well as for cells cultivated in homogenous suspension. The key figures-of-merit are uniformity of the specific absorption rate (SAR), induced temperature rise, SAR and volume efficiency, as well as the ability to ensure tight exposure and environmental control. For the exposure of cell monolayers, the WG setup with Petri dishes in the H-field maximum is superior in all respects. Reasonable performance is achieved with the resonator and transverse electromagnetic (TEM) cell. The best performance for cell suspensions is provided by the TEM cell for flasks in k-polarization. Acceptable performance is also achieved with the WG system and resonator. The temperature rise is an issue of concern for all setups. Measures to suitably control the temperature rise and to maintain equal temperature profiles between exposure and sham have been implemented for the WG and TEM cell setups. Localized temperature "hot spots" in the cell medium can be excluded for all investigated systems.