The radial transmission line as a broad-band shielded exposure system for microwave irradiation of large numbers of culture flasks

The problem of simultaneously exposing large numbers of culture flasks at n ominally equivalent incident power densities and with good thermal control is considered, and the radial transmission line (RTL) is proposed as a solu tion. The electromagnetic design of this structure is discussed, and an ext ensively bench-tested realization is described. Referred to 1 W of net forw ard power, the following specific absorption rate (SAR) data were obtained: at 835.62 MHz, 16.0 +/- 2.5 mW/kg (mean +/-SD) with range (11-22); at 2450 MHz, 245 +/- 50 mW/kg with range (130-323). Radio-frequency interference f rom an RTL driven at roughly 100 W is so low as to be compatible with a cel lular base station only 500 m distant. To avoid potential confounding by te mperature differences among as many as 144 T-75 flasks distributed over 9 R TLs (six irradiates and three shams), temperature within all flasks was con trolled to 37.0 +/- 0.3 degrees C. Experience with over two years of troubl e-free operation suggests that the RTL offers a robust, logistically friend ly, and environmentally satisfactory solution to the problem of large-scale in vitro experiments in bioelectromagnetics. (C) 1999 Wiley-Liss, Inc.