Study type: Medical/biological study (experimental study)

Effects of high peak power microwaves on the retina of the rhesus monkey med./bio.

By: Lu ST, Mathur SP, Stuck B, Zwick H, D'Andrea JA, Ziriax JM, Merritt JH, Lutty G, McLeod DS, Johnson M
Published in: Bioelectromagnetics 2000; 21 (6): 439-454
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Aim of study (acc. to author)

To determine if high peak power microwave radiation could induce retinal injuries.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 1.25 GHz
Modulation type: pulsed
Exposure duration: repeated daily exposure, 4 h/day, 3 days/week, for 3 weeks
  • power: 1.04 MW peak value
  • SAR: 1.3 kW/g peak value
  • SAR: 4.3 W/kg mean (± 0.1 W/kg)
  • SAR: 8.4 W/kg mean (± 0.3 W/kg)
  • SAR: 20.2 W/kg mean (± 0.4 W/kg)

Exposure 1

Main characteristics
Frequency 1.25 GHz
Type
Exposure duration repeated daily exposure, 4 h/day, 3 days/week, for 3 weeks
Additional info Lu S-T, DeAngelis ML, Gambrill CS. 1993. Ocular microwave thermometric dosimetry and thermometry in the rabbit. In: Blank M, editor. Electricity and magnetism in biology and medicine. San Francisco: San Francisco Press, Inc. p 675-678.
Modulation
Modulation type pulsed
Pulse width 6 µs
Rise time 0.9 µs
Fall time 0.9 µs
Additional info

Pulse repetition rates of 0, 0.59, 1.18, and 2.79 Hz were applied. The square wave equivalent pulse width calculated from pulse energy and peak power was 5.59 µs. The width of the entire sideband was less than 20 MHz.
Exposure setup
Exposure source
Distance between exposed object and exposure source 7.6 cm
Setup Monkeys were restrained in a PVC chair with head restraints. An open-end WR650 waveguide was used as an antenna to provide vertical E and horizontal H polarizations. The configuration allowed localized exposure limited to head and neck of the monkey.
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
power 1.04 MW peak value measured - -
SAR 1.3 kW/g peak value - - -
SAR 4.3 W/kg mean measured - ± 0.1 W/kg
SAR 8.4 W/kg mean measured - ± 0.3 W/kg
SAR 20.2 W/kg mean measured - ± 0.4 W/kg
Additional parameter details

The spatial peak-power density was 2.8 mW/cm² per W of transmitted power.

Measurement and calculation details

Redundant power measurements were made with calibrated instruments and components and recorded every 15 min. Power densities at the E-H plane and bore-sight power densities at various distances were mapped with a probe and meter positioned by a triaxial scanner using a CW signal. For ocular dosimetry, a thermometric procedure [Lu et al., 1993] was used on two 6 year old female monkey carcasses (4.5 and 4.9 kg) at 1 MW peak power, 6 µs pulse width, 17.5 Hz pulse repetition rate, and 80-100 W average transmitter output. The result was a retinal SAR rather than an intraocular SAR. Sixteen retinal SARs per globe and 32 retinal SARs per carcass were determined.

Exposed system:

Methods Endpoint/measurement parameters/methodology

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

Main outcome of study (acc. to author)

No evidence of degenerative changes and electroretinography (ERG) depression was seen. Retinal injury is very unlikely at 4W/kg. Functional changes that occur at higher R-SAR are probably reversible since no evidence of histopathologic correlation with ERG changes was seen.

Study character:

Study funded by

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