A dual vial waveguide exposure facility for examining microwave effects in vitro.

Abstract

A waveguide exposure system operated between 2 and 4 GHz was assembled in a laboratory incubator in order to study potential temperature-dependent and temperature-independent actions of microwaves. Two vials containing cell cultures were exposed simultaneously in a single waveguide in order to reduce the space required, and to allow concurrent study of autologous cell cultures in two different functional states (resting and stimulated) during exposure. Dosimetry was performed using three techniques with different underlying assumptions, as well as the technique of differential power measurement. Each of the four techniques yielded different results, although differences between the two vials using any single technique were negligible. A significant 'hot spot' occurred at the center of each vial. The ratio between maximum and minimum absorption rate within a single vial was 33-fold using a vial of 1.2-cm diameter and 1.6-cm height. With agitation and exposure at specific absorption rate (SAR) equal to 21 mW/ml, the thermal gradient was less than 0.1 degrees C between these two points. The averaged SAR can be determined by steady-state heating analysis. The exposure system can be calibrated readily by calculation for the measured powers, but not by differential power measurement.