Dual‐beam TEM applicator for direct‐contact heating of dielectrically encapsulated malignant mouse tumor

A microwave heating technique, a direct parallel to the parallel‐opposed treatment field that is used in therapeutic ionizing radiation, has been developed. The sources of radiation are two oppositely directed TEM applicators that operate at 2450 MHz. The applicator's design consists of an open‐ended rectangular waveguide that is partially loaded with low‐loss dielectric slabs. Such a structure can support a TEM mode of propagation. On direct contact with a tissue‐equivalent slab, the TEM applicator heats uniformly in the transverse plane. Exposed C3H mouse tumors, 1 cm in diameter and transplanted to grow on the flank of mice, were encapsulated within simulated phantom materials with dielectric properties that are similar to that of the tumor to form a rectangular slab. The TEM applicators were used to heat from opposite sides at alternating intervals of 5 to 50 seconds. The technique is capable of producing a uniform temperature of 42 (±0.25) °C over the entire tumor.