Deep Thermal Therapy System for Osteoarthritis of Knee Joint Using Resonant Cavity Applicator

Authors:Yasuhiro Shindo

Source:FERMAT, Volume17, Sep._Oct._2016-004

Abstract:This paper describes the heating properties of an improved resonant cavity applicator applied to a thermal therapy system for treating osteoarthritis (OA) in the knee. OA is one of the most common joint diseases in not only elderly people but also young athletes. OA restricts movement in patients’ daily lives and causes stiff and painful joints. In order to fight the progression of the disease, a microwave diathermy system is commonly used in clinics. For effective thermal therapy of OA, the deep tissue of the knee joint should be heated to 36-38o C. However, from my previous research, it was found that the microwave diathermy system's penetration depth was only 20mm. To establish a more effective thermal therapy method, a smaller resonant cavity applicator which allows the patient's leg to be set in a bent position was proposed. With the previous version of my resonant cavity applicator, OA patients had to keep their leg in a straight position. With this new applicator, allowing OA patients to keep their leg bent during the thermotherapy improves their comfort. Two cylindrical metal shields are used to focus the heating energy on the diseased joint, and the human knee is noninvasively heated. In this paper, I first presented the estimated SAR distributions using a cylindrical agar phantom. Second, the calculated results of the human knee model reconstructed from 2D CT images were discussed. Then, experimental results using an agar phantom that was shaped like a bent leg were shown. Finally, I evaluated the effectiveness of this applicator from these results. It was found that the newly developed resonant cavity applicator was of a practical size and was able to effectively heat the deep tissue inside the knee joint with the leg in a bent position.

Index Terms:Thermal therapy, Knee osteoarthritis (OA), Finite Element Method (FEM), Resonant cavity, SAR distribution.

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Deep Thermal Therapy System for Osteoarthritis of Knee Joint Using Resonant Cavity Applicator