Effects on energy absorption of orientation and size of animals exposed to 2.45-GHz microwave radiation.

Rat cadavers oriented perpendicularly to the electric field (parallel to the magnetic field) were exposed to 2.45-GHz microwave radiation. The weight of the cadavers ranged from approximately 5 to 320 g and their lengths ranged from approximately 5 to 22 cm. Average, whole-body specific absorption rates (SAR) were measured using calorimetric techniques, and local specific absorption rates were obtained from time-temperature profiles measured with a non-interacting thermistor probe. The average, whole-body SAR decreased gradually from 0.58 mW g-1 per mW cm-2 at 40 g (10.1 cm in length) to 0.38 mW g-1 per mW cm-2 at 320 g (22 cm in length). The average whole-body SAR decreased from 0.81 to 0.34 mW g-1 per mW cm-2 for cadavers ranging in weight from 5 g (5 cm in length) to 30 g, respectively. The local SAR in the brains decreased from approximately 0.95 mW g-1 per mW cm-2 at 40 g to 0.54 mW g-1 per mW cm-2 at 320 g. Between 5 g and 30 g the SARs in the brain varied from 0.52 to 1.11 mW g-1 per mW cm-2. The local SAR in the colon ranged from 1.05 mW g-1 per mW cm-2 to 0.24 mW g-1 per mW cm-2 for weights between 40 and 320 g. In the 5 to 30 g range, the SAR varied from 0.48 to 1.23 mW g-1 per mW cm-2. A comparison of these results with data previously reported for animals oriented parallel to the E-field showed that the average whole-body SARs were larger for animals weighing greater than 40 g when oriented perpendicularly to the E-field. The local SARs in the colon and brain were slightly higher for the parallel orientation in animals weighing greater than 40 g. The average, whole-body and local SARs were significantly higher for the parallel orientation for animals weighing less than 40 g.