Study type: Medical/biological study (experimental study)

In vitro studies of microwave-induced cataract. II. Comparison of damage observed for continuous wave and pulsed microwaves med./bio.

By: Creighton MO, Larsen LE, Stewart-DeHaan PJ, Jacobi JH, Sanwal M, Baskerville JC, Bassen HE, Brown DO, Trevithick JR
Published in: Exp Eye Res 1987; 45 (3): 357-373
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Aim of study (acc. to author)

To investigate the damage on rat eye lense caused by microwave irradiation either pulsed or continuous wave in vitro and to compare it with previous report (q.v. publication 9535)

Endpoint

Exposure

Exposure Parameters
Exposure 1: 918 MHz
Modulation type: pulsed
Exposure duration: continuous for 6, 20, and 60 min
Exposure 2: 918 MHz
Modulation type: CW
Exposure duration: continuous for 6, 20, and 60 min

Exposure 1

Main characteristics
Frequency 918 MHz
Type
Charakteristic
  • guided field
Exposure duration continuous for 6, 20, and 60 min
Modulation
Modulation type pulsed
Pulse width 10 µs
Additional info

Repetition rates were varied to obtain various average powers.
Exposure setup
Exposure source
Setup Lenses were maintained at constant temperature by circulating phosphate buffered saline (PBS) in a thermostatically-controlled exposure cell placed in the middle of a WR975 waveguide at 1/4 λ from the shorting plate as previously described [Stewart-De Haan et al., 1983].
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
power 24 kW peak value - - transmitted power
SAR 5.75 mW/g mean measured - 0.5 W
SAR 11.5 mW/g mean measured - 1 W
SAR 23 mW/g mean measured - 2 W
SAR 69 mW/g mean measured - 6 W
SAR 231 mW/g mean measured - 20 W
SAR 750 mW/g mean measured - 65 W
Additional parameter details

Five separate conditions were employed for both CW and pulsed microwaves with total energies of 0.23, 0.46, 1.38, 4.6, and 15 Wmin/g.

Measurement and calculation details

The SAR values were determined by measuring the temperature rise at the lens site of the exposure cell with the saline not circulating but filling the hoses. The results in this condition were about half the values previously reported with no saline in the hoses [Stewart-De Haan et al., 1983].

Exposure 2

Main characteristics
Frequency 918 MHz
Type
Charakteristic
  • guided field
Exposure duration continuous for 6, 20, and 60 min
Modulation
Modulation type CW
Exposure setup
Exposure source
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
SAR 5.75 mW/g mean measured - 0.5 W
SAR 11.5 mW/g mean measured - 1 W
SAR 23 mW/g mean measured - 2 W
SAR 69 mW/g mean measured - 6 W
SAR 231 mW/g mean measured - 20 W
SAR 750 mW/g mean measured - 65 W
Additional parameter details

Five separate conditions were employed for both CW and pulsed microwaves with total energies of 0.23, 0.46, 1.38, 4.6, and 15 Wmin/g.

Reference articles

Exposed system:

Methods Endpoint/measurement parameters/methodology

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

Main outcome of study (acc. to author)

Sham exposed control eye lenses did not show any damage. Different kinds of damage, such as foam, granulation, globular damage, holes in fibre cells, and capsular damage, could be examined by electron microscopy on lenses exposed to pulsed or continuous wave (CW) microwaves.
Pulsed exposure in contrast to CW exposure leads to a greater depth of damage, as well as damages caused by CW exposure occured at higher power than observed for pulsed microwave exposure. These findings combined with previous examinations suggest that pulsed field irradiation has an additional effect on biological tissue elicit by elastic (pressure) waves.

Study character:

Study funded by

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