MICROWAVE RADIATIONS: Heating of Human and Animal Tissues by Means of High Frequency Current with Wavelength of Twelve Centimeters (The Microtherm)

Radar was made possible by development of the magnetron oscillator tube. Radar was one of the closely guarded secrets during the war. Now, with the ending of hostilities, its field of usefulness has been extended into the field of medicine. The Raytheon microtherm, which generates energy in a continuous wave, air-cooled magnetron oscillator tube, is the first generator of this type to be developed for the heating of human tissues. The microtherm operates at a frequency of 2,400 to 2,500 megacycles, or at a wavelength of approximately 12 cm. with a maximum power output of 125 watts. The energy is applied to the patient by means of a director (fig. 1). The entire radio-frequency circuit consists of the magnetron oscillating tube with a coaxial cable connected to a director. This investigation was undertaken to determine whether high frequency current of this magnitude would heat living tissues to a temperature of