Study type: Medical/biological study (experimental study)

An investigation of the thermal and athermal effects of microwave irradiation on erythrocytes med./bio.

By: Peterson DJ, Partlow LM, Gandhi OP
Published in: IEEE Trans Biomed Eng 1979; 26 (7): 428-436
Download citation in RIS format

Aim of study (acc. to author)

To investigate thermal and athermal effects microwave irradiation on erythrocytes.

Background/further details

Potassium and hemoglobin loss were determined as it indicates altered stability and/or permeability of the erythrocyte membrane.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 2.45 GHz
Exposure duration: continuous for 45 min
  • power density: 10 mW/cm²
  • power density: 30 mW/cm² cf. remarks (to maintain temp at 37°C (30-35 mW/cm²))
  • power density: 43 mW/cm² cf. remarks (to raise temp to 37°C at half the rate)
  • power density: 90 mW/cm² cf. remarks (to raise temp to 37°C (86-90 mW/cm²))
  • power density: 140 mW/cm² cf. remarks (to raise temp to 37°C at twice the rate)
  • power density: 93 mW/cm² cf. remarks (to maintain temp at 41.5°C)
  • power density: 112 mW/cm² cf. remarks (to raise temp to 41.5°C)
Exposure 2: 12.5–18 GHz
Exposure duration: continuous for 45 min
  • power density: 31 mW/cm² cf. remarks (to maintain temp at 37°C)
  • power density: 124 mW/cm² cf. remarks (to raise temp to 37°C)

Exposure 1

Main characteristics
Frequency 2.45 GHz
Type
Charakteristic
Exposure duration continuous for 45 min
Exposure setup
Exposure source
Distance between exposed object and exposure source 137 cm
Setup The suspension was filled in 0.4 ml polypropylene microcentrifuge tubes of 0.4 cm diameter and 4.5 cm length with a 0.05 ml air gap remaining at the top after capping. In the first experiment, sample tubes were placed in a stationary Styrofoam sample holder with the long axis of each tube parallel to the E-field vector. For all further experiments, a rotating sample holder was used to achieve identical exposure of all tubes. They were inserted in radial holes in a Styrofoam disk held in the vertical position by a long Teflon shaft of 2.5 cm diameter turned at 2 rpm by a motor shielded by RF-absorbing material. The vertical rotation (reversed every minute) caused a continuous mixing of the suspension.
Additional info In the first experiment, irradiation was interrupted every 10 min in order to measure the temperature of the samples. In all further experiments, the temperature was continuously monitored using an LCOF probe. The matched thermal profile control samples were heated in a water bath (first experiment) or in a hot air incubator with a rotating sample holder.
Parameters
Measurand Value Type Method Mass Remarks
power density 10 mW/cm² - measured - -
power density 30 mW/cm² cf. remarks measured - to maintain temp at 37°C (30-35 mW/cm²)
power density 43 mW/cm² cf. remarks measured - to raise temp to 37°C at half the rate
power density 90 mW/cm² cf. remarks measured - to raise temp to 37°C (86-90 mW/cm²)
power density 140 mW/cm² cf. remarks measured - to raise temp to 37°C at twice the rate
power density 93 mW/cm² cf. remarks measured - to maintain temp at 41.5°C
power density 112 mW/cm² cf. remarks measured - to raise temp to 41.5°C
Additional parameter details

Samples were either irradiated at 10 mW/cm² reaching a temperature of 28.7°C (i.e. a rise of 3.7°C) or heated up to 37°C or 41.5°C by varying power densities.

Measurement and calculation details

Output power was measured by a power meter for both systems. Power density was measured by a radiation monitor for this system. SAR was determined from the rate of temperature rise using high field intensities and short exposure times.

Exposure 2

Main characteristics
Frequency 12.5–18 GHz
Type
Charakteristic
Exposure duration continuous for 45 min
Additional info Frequency was swept: 12.5-13 GHz, 13.5-14 GHz, 14.5-15 GHz, 15.5-16 GHz, 16.5-17 GHz, or 17.5-18 GHz.
Exposure setup
Exposure source
Distance between exposed object and exposure source 10 cm
Parameters
Measurand Value Type Method Mass Remarks
power density 31 mW/cm² cf. remarks measured - to maintain temp at 37°C
power density 124 mW/cm² cf. remarks measured - to raise temp to 37°C
Measurement and calculation details

Power density was calculated from the configuration for this system because it could not be measured directly by any available radiation monitor.

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Time of investigation:
  • after exposure

Main outcome of study (acc. to author)

No differences were found between microwave heated or conventionally heated erythrocyte-suspensions. Thus, the found effects should be ascribed only as thermal.

Study character:

Study funded by

Related articles