Simultaneous localized 915 MHz external and interstitial microwave hyperthermia to heat tumors greater than 3 cm in depth

A technique for heating superficial lesions extending to a depth greater than 3 cm using 915 MHz electromagnetic energy is described. It is well established that with external microwave applicators operating at 915 MHz, it is only possible to heat adequately up to a maximum depth of 3 cm. However, it is demonstrated that by implanting additional layers of interstitial microwave antennas (1.5 cm spacing) at required depths greater than 3 cm, and by simultaneously exciting these applicators as well as an external applicator, it is possible to extend the depth of heating at this frequency. A large neck node was successfully heated when this combined technique was used. The details of the method and the equipment used are described. Specific Absorption Rate (SAR) values and temperature distributions obtained during the four treatments delivered to the patient are also presented. This technique can be used in situations where it is not possible to perform extensive interstitial implantation, and in institutions where hyperthermia equipment for heating deeper lesions is not available.