Eight samples were exposed at a time by placing them inside the waveguide which was located in the incubator. Holes (4 mm in diameter) were drilled into the waveguide near the sample location to allow air flow and constant CO2 concentration for the culture medium.
For sham exposure, samples were placed in a second waveguide in another incubator, but no microwave power was applied.
The specific absorption rates (SAR) for the samples were obtained from a numerical calculation of the field distribution based on the Finite Difference Time Domain method (FDTD). Calculations were verified by comparing the resulting values of reflection and transmission factors with measured values and were used to establish the relation between the field distribution inside the waveguide and the microwave power transmitted through it. Thus, the SAR-values could be monitored simply by measuring the transmitted microwave power.