27 MHZ HYBRID EVANESCENT-MODE APPLICATORS (HEMA) WITH FLEXIBLE HEATING FIELD FOR DEEP AND SAFE SUBCUTANEOUS HYPERTHERMIA

A new class of low-frequency electromagnetic applicators for hyperther mic treatment of superficial and subcutaneous tissues is described. Th ese applicators employ an air-filled waveguide segment which is operat ing below the cut-off frequency, the evanescent modes of which are ene rgized by suitable exciters to produce modal field components. Direct radiators are integrated into the waveguide to generate additional dir ect field components. All field components may be combined in differen t power level ratio, phase, and orientation, to provide a composite he ating field exhibiting a large variety of field sizes, shapes, and pen etration features. The composite field emerging from the waveguide ape rture propagates within the tissue to be heated through a non-critical air-gap. These versatile heating devices appear of potential interest to heat a variety of deep and localized subcutaneous tissues to thera peutic temperatures without injury to access fat layers of substantial thickness.