Stonebridge Jb

Therapeutic applications of electromagnetic power

The use of electromagnetic (EM) power for therapeutic applications has existed since EM sources have been available to man. Physical medicine has been a major user of both shortwave (27.33 MHz) and microwave (2450 MHz) diathermy over the decades in which the EM power has been used to heat deep tissues for stimulating various medically beneficial physiologic responses in the relief of certain pathological conditions. Experimental and clinical research indicates that these responses will occur as a result of elevating the tissue temperatures in the range 41° to 45°C requiring absorbed power densities from 50 to 170 W/kg in the deep tissues where treatment is desired. The combination of pain responses and a large reserve of blood cooling capacity seems to be sufficient for limiting the heating to safe, but therapeutic levels in vasculated and innervated tissue. Recent research has shown that the use of the industrial, scientific, and medical (ISM) frequency of 915 MHz is more efficient than the currently used 2450-MHz microwave frequency in terms of maximum power transfer to deep tissues. The results also show that in addition to thermal applications, microwave energy can be used for the controlled transcutaneous stimulation of nerve action potentials via implanted miniature microwave diodes.

Development of a 915-MHz Direct-Contact Applicator for Therapeutic Heating of Tissues

The design of a 915-MHz diathermy dielectric-loaded applicator with a TE/sub 10/-mode aperture field distribution is described. The lightweight porous dielectric used for loading the applicator allows for the transmission of refrigerated air through the cavity to provide surface cooling so therapeutic temperature can be produced in deep tissues without excessive heating of surface tissues. The design is based on theoretical calculations previously developed by the authors which predict optimal size of the aperture and field distribution that would provide the best heating patterns in deep layers of tissue. Experimental evaluations of the heating of tissues of models and human beings are discussed.

Evaluation of a Therapeutic Direct-Contact 915-MHz Microwave Applicator for Effective Deep-Tissue Heating in Humans

A 13-cm square direct-contact microwave applicator which operates at 915 MHz was evaluated in tissue models and human volunteers to determine its therapeutic effectiveness. It was found that the applicator with radome- and forced-air cooling selectively elevates temperatures in muscles (1-2 cm) to 43-45/spl deg/C. At this higher range of temperature, certain physiologic responses such as an increase in blood flow are produced. The applicator may also be used to heat malignant tumors of muscle.