Study type: Medical/biological study (experimental study)

Studies on microwave and blood-brain barrier interaction. med./bio.

Published in: Bioelectromagnetics 1980; 1 (3): 313-323

Aim of study (acc. to author)

Examination of interaction between microwaves and the blood-brain barriers, and correlation of any change in permeability with the quantity and distribution of the absorbed microwave energy.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 2.45 GHz
Modulation type: pulsed
Exposure duration: continuous for 20 min
Exposure 2: 2.45 GHz
Modulation type: CW
Exposure duration: 15 s

Exposure 1

Main characteristics
Frequency 2.45 GHz
Type
Polarization
  • unspecified
Exposure duration continuous for 20 min
Modulation
Modulation type pulsed
Additional info

rectangular shaped 10 and 20 µs pulses delivered at 25, 50, 100 and 500 pps.

Exposure setup
Exposure source
  • dielectrically loaded coaxial applicator, 14 mm diameter aperture
Distance between exposed object and exposure source 0 m
Setup The applicator was in direct contact with the left side of head.
Parameters
Measurand Value Type Method Mass Remarks
power density 1 W/cm² mean measured - 80.0 mW/g corresponding average SAR in the brain at 20 µs pulse width and 500 pulses per second
power density 5 W/m² mean measured - 0.04 mW/g corresponding average SAR in the brain at 10 µs pulse width and 25 pulses per second
power density 200 W/m² mean measured - 1.6 mW/g corresponding average SAR in the brain at 20 µs pulse width and 500 pulses per second
power density 50 W/m² mean measured - 0.4 mW/g corresponding average SAR in the brain at 20 µs pulse width and 100 pulses per second
power density 10 W/m² mean measured - 0.08 mW/g corresponding average SAR in the brain at 10 µs pulse width and 50 pulses per second
power density 145 mW/cm² mean measured - 11.5 mW/g corresponding average SAR in the brain at 20 µs pulse width and 100 pulses per second

Exposure 2

Main characteristics
Frequency 2.45 GHz
Type
Waveform
Polarization
Exposure duration 15 s
Modulation
Modulation type CW
Exposure setup
Exposure source
  • coaxial applicator
Parameters
Measurand Value Type Method Mass Remarks
power 20 W - cf. remarks - -

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Investigated organ system:
Time of investigation:
  • during exposure
  • after exposure

Main outcome of study (acc. to author)

The rectal temperature showed a maximum increase of less than 0.75°C from a mean pre-exposure temperature of 36.6°C. The highest brain temperature recorded in a similar group of animals was less than 41°C. Brain temperatures must exceed 42°C for an appreciable length of time in order to effect changes in blood-brain barrier permeability. Consequently, barrier integrity was perserved. Conclusion: it appears that enhancement of blood-brain barrier permeation is not directly related to the strength of the microwave field in the tissue, but is associated with elevations of brain temperature.

Study character:

Study funded by