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PRELIMINARY STUDIES ON THE HEATING AND CIRCULATORY EFFECTS OF MICRO-WAVES—'RADAR'

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URSULA M. LEDEN, J. F. HERRICK, KHALIL N. WAKIM, FRANK H. KRUSEN · 1947

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1947 Mayo Foundation research on dogs and other animals found 3,000 megacycle micro-waves heated tissue by 3-5°C and increased femoral vein blood flow by an average of 109 percent.

Plain English Summary

Summary written for general audiences

This 1947 study from the Mayo Foundation investigated the heating and circulatory effects of micro-waves at 3,000 megacycles per second (10 centimeter wavelength) in trained dogs and anaesthetized animals, examining their therapeutic potential. A 20-minute exposure at 65 watts and 5 centimeters distance raised temperatures 3-5°C in skin, subcutaneous tissue and muscle to 2 centimeters depth, and femoral vein blood flow increased by an average of 109 percent after exposure.

Why This Matters

This 1947 research reported heating and circulatory effects of 3,000 megacycle micro-waves in animal subjects, with a view to their therapeutic use in medicine. Tissue temperatures rose 3-5°C to a depth of 2 centimeters, blood flow in the femoral vein increased by an average of 109 percent after exposure, and heart rate rose in anaesthetized animals with a general temperature rise but not in trained animals where local heating did not cause a general temperature rise. Superficial tissues cooled faster than deeper ones. The authors described micro-waves as suitable for heating living tissues with accurate localization, since the radiation can be directed along a beam and focused.

Figures from the Original Paper

Diagrams extracted from the original research document.

chartPage 2 - AI-described figure: The radio-frequency spectrum showing particularly the radio-frequencies allocated to physical medicine by the Federal Communications Commission.
p. 2 of the original PDF
diagramPage 3 - AI-described figure: Figure 3 illustrates a small portable experimental model of a micro-wave generator containing an air-cooled ambidextrous magnetron with maximal output.
p. 3 of the original PDF
graphPage 4 - AI-described figure: Fig. 4: Increases in temperature of skin, subcutaneous tissue and muscle after exposure to micro-waves of the thigh of an anesthetized animal on which a surgical procedure was performed.
p. 4 of the original PDF

Exposure Information

A logarithmic frequency spectrum from 10 Hz to 100 GHz showing where this study's 3,000 MHz exposure sits relative to common EMF sources.Where This Frequency Sits on the EMF SpectrumELFVLFLF / MFHF / VHFUHFSHFmm10 Hz100 GHzThis study: 3,000 MHzPower lines50/60 Hz5G mm28 GHzLogarithmic scale

Specific exposure levels were not quantified in this study. Duration: 20 minutes

Study Details

To investigate the heating and circulatory effects of micro-waves at 3,000 megacycles per second with a wavelength of 10 centimetres, examining their therapeutic potential and physiological responses in animal subjects.

Experiments were conducted on trained dogs and anaesthetized animals using a small hemispherical dir...

Micro-waves produced significant heating of tissues with temperature rises of 3-5°C in skin, subcuta...

Micro-waves are suitable for heating living tissues with accurate localization. The radiation can be directed along a beam and focused, permitting precise treatment. The high absorption rate at 3,000 megacycles (7,000 times that of 27 megacycles used in short-wave diathermy) indicates more efficient heating. The technique offers advantages over conventional methods including freedom of movement, rapid cooling, and potential for cross-firing multiple beams.

Cite This Study
URSULA M. LEDEN, J. F. HERRICK, KHALIL N. WAKIM, FRANK H. KRUSEN (1947). PRELIMINARY STUDIES ON THE HEATING AND CIRCULATORY EFFECTS OF MICRO-WAVES—'RADAR'.
Show BibTeX
@article{preliminary_studies_on_the_heating_and_circulatory_effects_of_micro_waves_radar__g4149,
  author = {URSULA M. LEDEN and J. F. HERRICK and KHALIL N. WAKIM and FRANK H. KRUSEN},
  title = {PRELIMINARY STUDIES ON THE HEATING AND CIRCULATORY EFFECTS OF MICRO-WAVES—'RADAR'},
  year = {1947},
  
  
}
No DOI on file for this study.

Quick Questions About This Study

In dogs and other animals, micro-waves at 3,000 megacycles per second produced significant heating of tissues with temperature rises of 3-5°C, a consistent increase in venous blood return, and an average increase of 109 percent in femoral vein blood flow after exposure.
Exposure was 75 milliamperes (65 watts) at 5 centimeters distance for 20 minutes, using a small hemispherical director with a magnetron tube producing 3,000 megacycles per second.
Magnetron tubes were the micro-wave generation technology used in the study; a magnetron tube producing 65 watts at 3,000 megacycles per second powered the director. In 1938 the researchers had advised Bell Telephone Laboratories that higher-wattage magnetron tubes should prove suitable for therapeutic purposes.
Micro-waves are suitable for heating living tissues with accurate localization. The radiation can be directed along a beam and focused, and the technique offers advantages over conventional methods including freedom of movement, rapid cooling, and potential for cross-firing multiple beams.
Heart rate increased in anaesthetized animals with a general temperature rise but not in trained animals, where local heating did not cause a general temperature rise.