New heating system using resonant cavity applicator with electrical shield for rheumatoid arthritis

This paper discusses the improvement of the reentrant resonant cavity applicator with an electromagnetic shield for concentrating heating energy in deep regions inside a human knee. Thermotherapy is widely used for musculoskeletal disorders as a physical therapy in clinical settings. Hot packs, paraffin baths, ultra-short waves and microwaves are generally used as well as therapeutic exercises for joint diseases such as osteoarthritis (OA) and rheumatoid arthritis. However, all of them have advantages and disadvantages, and a successful heating method for deep tissue has not yet been realized. In this paper, first, the heating method with the resonant cavity applicator is presented. Second, the proposed method of reconstructing the 3-D anatomical human FEM model to calculate temperature distributions is described. Third, the results of temperature distributions are discussed. Finally, the results of the temperature distributions for the resonant cavity applicator is compared with the temperature distribution for microwave diathermy. As the penetration depth of microwave diathermy used in the clinic is less than approximately 20 mm, it is not easy to heat the joint cavity. However, the proposed heating method with the resonant cavity applicator can be expected to heat the joint cavity.