A technique for localized tumor hyperthermia in small animals

Hyperthermia, the intentional elevation of tissue temperature above 41°C is being intensely researched as a therapeutic modality for cancer, especially when used in combination with radiation therapy and/or chemotherapy. A serious impediment to laboratory progress in this area has been the lack of affordable equipment providing control and reproducibility when faced with highly variable factors including tumor size and shape, blood flow, heat conduction, and tissue dielectric discontinuity. Our solution has been the development of a laboratory microwave hyperthermia system, dedicated to the treatment of small, superficial tumors. This system uses a 2.45-GHz microwave generator and custom applicator to noninvasively heat a mass of tissue about 2 cm in diameter and 1.5 cm in depth. Tissue temperature at up to four locations is measured using miniature, Teflon-encased thermocouples. The microwave generator and the thermometry are interfaced to a personal computer which provides fully automated hyperthermia treatment reproducible to ±0.2°C.