An evaluation of microwave diathermy applicators using free space electric field mapping.

An electric field mapping study is described which was designed and executed to study the performance characteristics of various prototype and currently used microwave diathermy applicators operating at 2450 MHZ. A miniature diode detector/dipole probe, developed by the Bureau of Radiological Health, was used to map the 'near' electric fields in the aperture plane of each applicator. From the field mapping results, parameters for use in the evaluation of the radiation safety of various applicators are developed. A thermographic camera was used to determine heating characteristics of the applicators in simulated biological material. The thermal effectiveness of these applicators was also investigated by determining their Specific Absorption Rate, a recently developed parameter. The superiority of a specially designed prototype applicator (in terms of uniformity and effectiveness of energy deposition, and minimal leakage radiation) compared with currently used applicators is demonstrated.