HAGAN et al.: NOVEL WAVEGUIDE-BASED RF/MW EXPOSURE SYSTEM FOR STUDYING NONTHERMAL EFFECTS

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Fig. 6. Surface plots of the  field and  (a) based on waveguide theory using measured forward and reflected powers and (b) predicted by the XFDTD model.

W, frequency

GHz.

Forward power

even when a much smaller time step (1/4 of the default value)

used for both cases to compute the detailed  field and SAR

was implemented.

patterns in the region where the chromaffin cells are located on

A final difference between the theoretical field pattern and

the glass fiber filter. In addition, in order to determine the op-

that computed by XFDTD was the appearance of spikes in the

timum exposure conditions for the cells, the effects of different

magnitude of both components ( and ) of  in the vicinity

orientations of the cell perfusion apparatus were examined: the

of the waveguide slots in the XFDTD model (Fig. 6). These

plane of the glass fiber filter was placed either perpendicular

or parallel to the  field. Henceforth, these are referred to as

spikes died out rapidly with distance from the slots and did

the "perpendicular" and "parallel" orientations. In the labora-

not observably affect the overall standing wave pattern in the

tory, this is physically achieved by rotating the waveguide by

waveguide.

90 while maintaining the cell perfusion apparatus with the per-

B. Characterization of the RF Exposure System

fusion tubing vertical and the glass fiber filter horizontal in the

waveguide. In the XFDTD model, the waveguide was rotated

The exposure protocols for the experiments call for the cell

by 90 from the perpendicular orientation to achieve the par-

perfusion apparatus to be placed at one of two possible locations

allel orientation.

in the waveguide, at the maximal  or  . Thus, XFDTD was