Leakage in the Proximity of Microwave Diathermy Applicators Used on Humans or Phantom Models
Howard I. Bassen, Gideon Kantor, Paul S. Ruggera, Donald M. Witters, Jr. · 1978
1978 government research found that medical microwave heating devices leaked electromagnetic radiation beyond their intended treatment areas.
Plain English Summary
This 1978 government report investigated electromagnetic radiation leakage from microwave diathermy machines, which use focused microwave energy for deep tissue heating in medical treatments. The study measured how much microwave radiation escaped from these therapeutic devices when used on human patients and laboratory test models. This research was part of early efforts to understand occupational and patient exposure risks from medical microwave equipment.
Why This Matters
This Bureau of Radiological Health report represents crucial early recognition that medical microwave devices could expose patients and healthcare workers to unintended radiation. Microwave diathermy units operate at similar frequencies to microwave ovens and early cell phones, typically between 915 MHz and 2.45 GHz. The science demonstrates that even medical devices designed for therapeutic heating can leak significant microwave energy beyond their intended treatment zones.
What this means for you: medical microwave exposure research like this laid the groundwork for understanding how focused electromagnetic energy affects human tissue. The reality is that if therapeutic microwave devices showed measurable leakage in 1978, it highlights how electromagnetic radiation from any high-powered source requires careful measurement and safety protocols. This government attention to medical device leakage also underscores why consumer devices operating at similar frequencies deserve equal scrutiny.
Finding
From typical 2450 MHz microwave diathermy treatments using a BRH-developed Transco applicator and performed on humans or phantoms at low levels, the leakage at 5 cm from the surface of the applicator/tissue interface was extrapolated to effective treatment conditions (235 W/kg delivered to the phantom muscle material). The leakage levels for the human back, thigh, and elbow treatments were computed to be less than 5 mW/cm2 under full-power conditions. The leakage for the forearm under full-power conditions was computed to be less than 10 mW/cm2, while for the upper arm a maximum
In their words
“From typical 2450 MHz microwave diathermy treatments using a BRH-developed Transco applicator and performed on humans or phantoms at low levels, the leakage at 5 cm from the surface of the applicator/tissue interface was extrapolated to effective treatment conditions (235 W/kg delivered to the phantom muscle material). The leakage levels for the human back, thigh, and elbow treatments were computed to be less than 5 mW/cm2 under full-power conditions. The leakage for the forearm under full-power conditions was computed to be less than 10 mW/cm2, while for the upper arm a maximum”
Figures from the Original Paper
Diagrams extracted from the original research document.
Exposure Information
Specific exposure levels were not quantified in this study. Duration: less than 1-minute duration
Study Details
To evaluate the practicality of using phantoms to predict leakage that would occur during actual clinical treatment procedures
Leakage radiation measurements were made in the immediate vicinity of a Transco 2450 MHz circularly ...
Low-power, human-subject leakage data were extrapolated to those values that would exist during clin...
The Transco contact applicator is generally appropriate for low-leakage back and thigh treatments. The proposed BRH standard calls for each applicator to be specified and labeled for use only on those parts of the body for which the applicator satisfies leakage and SAR tests. In addition, there is good agreement (within a factor of 2) between virtually all actual leakage data (human) and simulated (phantom) treatments, provided that appropriate phantoms are used. These results can be applied to the proposed BRH microwave diathermy standard (which purposely omits the use of human subjects for diathermy equipment performance testing). Leakage testing with appropriate phantoms is a reasonable means for minimizing unnecessary microwave leakage in clinical conditions. Phantom data on leakage and energy deposition for conventional, non-contact applicators (types B and E) revealed that high leakage (35.5 and 44.0 mW/cm2) would have occurred under identical 'effective' treatment conditions.
Show BibTeX
@article{leakage_in_the_proximity_of_microwave_diathermy_applicators_used_on_humans_or_ph_g6062,
author = {Howard I. Bassen and Gideon Kantor and Paul S. Ruggera and Donald M. Witters and Jr.},
title = {Leakage in the Proximity of Microwave Diathermy Applicators Used on Humans or Phantom Models},
year = {1978},
}