|Exposure 1: 1.25 GHz|
|Exposure 2: 1.25 GHz|
|Exposure 3: 1.25 GHz|
|Exposure 4: 1.25 GHz|
|Exposure 5: 1.25 GHz|
|Exposure 6: 1.25 GHz|
|Exposure 7: 1.25 GHz|
|Exposure 8: 1.25 GHz|
|Exposure 9: 1.25 GHz|
|Exposure 10: 1.25 GHz|
|Exposure 11: 1.25 GHz|
Twelve different MW events including sham were tested in two series of experiments. The first series was designed to compare the twofold increase in the response rate (evoked body movements) by pulsed to gated CW (single pulse) MW (E1, E2, E3, E6, E7, E8). The second series was designed to supplement and to expand the dose-response curve of the first series (E4, E5, E9, E10, E11, and sham). Each mouse was exposed in three sessions, at least 24 h apart. Each session comprised six consecutive randomised MW events, the testing period for each event lasting 15 s. To evaluate thermal stimulation and hyperthermia, rectal and four subcutaneous cranial temperatures were measured in an anaesthetised mouse for five different MW exposures (E4, E5, E9, E10, E11) and eight replications. Positive controls were performed using 100-ms acoustic (104 dB SPL, 2.5-25 kHz noise) and tactile (40 psi air puff) stimuli using a procedure similar to the MW exposure.
No difference in response to pulsed and gated continuous wave stimuli of equal average power was observed.
The incidence of evoked body movements increased proportionally with specific absorption when the whole-body average specific absorption rate (SAR) was at a constant level (7300 W/kg). Under a constant average specific absorption rate, the response incidence reached a plateau at 0.9 kJ/kg. For higher doses (than 0.9 kJ/kg), response incidence was proportional to the specific absorption rate and reached a plateau at 900 W/kg.
Body movements could be evoked by a single microwave pulse.
The lowest whole-body specific absorption investigated was 0.18 kJ/kg, and the corresponding brain specific absorption was 0.29 kJ/kg. Bulk heating potentials of these specific absorptions were less than 0.1°C. For doses higher than 0.9 kJ/kg, the response incidence was also proportional to subcutaneous heating rate. The extrapolated absolute thresholds (0% incidence) were 1.21°C temperature increment and 0.24°C/s heating rate.
Data of this study should be considered in promulgation of personnel protection guideline against high peak power but low average power microwaves.