Study type: Medical/biological study (experimental study)

Effects of field orientation during 700-MHz radiofrequency irradiation of rats. med./bio.

Published in: Physiol Chem Phys Med NMR 1989; 21 (1): 65-72

Aim of study (acc. to author)

To determine if the E-orientation (long axis of body parallel to electric field) versus H-orientation (long axis parallel to magnetic field) effects upon thermal, cardiovascular, and respiratory changes noted at 2450 MHz (see publication 2239) were also present at the resonant frequency of 700 MHz.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 700 MHz
Modulation type: CW
Exposure duration: intermittend 7.2 min +/ 0.5 min exposure - 10.6 min +/- 0.5 min recovery time
Exposure 2: 700 MHz
Modulation type: CW
Exposure duration: intermittend 7.2 min +/ 0.5 min exposure - 10.6 min +/- 0.5 min recovery time

General information

*The exposure was discontinued when the colonic temperature increased to 39.5°C and it was initiated again when the temperature returned to 38.5°C. This procedure was continued for 3 cycles

Exposure 1

Main characteristics
Frequency 700 MHz
Type
Charakteristic
Polarization
Exposure duration intermittend 7.2 min +/ 0.5 min exposure - 10.6 min +/- 0.5 min recovery time
Additional info Animals were exposed in E.orientation (long axis parallel to electric field)
Modulation
Modulation type CW
Exposure setup
Exposure source
Distance between exposed object and exposure source 1 m
Chamber Eccosorb RF-shield anechoic chamber
Setup Animals placed on a holder which consisted of seven 0.5 cm (O.D) Plexiglas rods mounted in a semicircular pattern on 4 cm x 6 cm Plexiglas plates (0.5 cm thick)
Parameters
Measurand Value Type Method Mass Remarks
SAR 9.2 mW/g mean calculated whole body -

Exposure 2

Main characteristics
Frequency 700 MHz
Type
Charakteristic
Polarization
Exposure duration intermittend 7.2 min +/ 0.5 min exposure - 10.6 min +/- 0.5 min recovery time
Additional info Animals were exposed in H.orientation (long axis parallel to magnetic field)
Modulation
Modulation type CW
Exposure setup
Exposure source
Distance between exposed object and exposure source 1 m
Parameters
Measurand Value Type Method Mass Remarks
SAR 13 mW/g mean calculated whole body -

Exposed system:

Methods Endpoint/measurement parameters/methodology

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

Main outcome of study (acc. to author)

In spite of equivalent colonic specific heating rates (SHR) and the reduced E-orientation average SAR, the right subcutaneous, tympanic, and tail SARs, SHRs and absolute temperature increases were significantly greater in E- than in H-orientation. The cooling rate of the animals at all monitoring sites was also significantly greater in E- than in H-orientation. Heart rate and mean arterial blood pressure significantly increased during exposure; however, alterations between orientations were not different. Respiratory rate significantly increased during exposure in H-, but not in E-orientation.
These findings suggest that during resonant frequency irradiation, differences occur in the pattern of heat deposition between E- and H-orientation exposure. When compared with previous studies performed at supraresonant frequencies (e.g. publication 2239), the lower level of cardiovascular change in this investigation was probably related to the lower periphery-to-core thermal gradient.

Study character:

Study funded by

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