Heating Performances of Array Applicator for Interstitial Microwave Hyperthermia: Numerical Simulation and Clinical Trial

INTRODUCTION In recent years, various types of medical applications of microwaves have widely been investigated and reported [1]. In particular, minimally invasive microwave thermal therapies using thin applicators are of a great interest. They are interstitial microwave hyperthermia [2] and microwave coagulation therapy (MCT) [3] for medical treatment of cancer, cardiac catheter ablation for ventricular arrhythmia treatment [4], thermal treatment of BPH (Benign Prostatic Hypertrophy) [5], etc. Up to now, the authors have been studying such thin coaxial antennas for the interstitial microwave hyperthermia. Hyperthermia is one of the modalities for cancer treatment, utilizing the difference of thermal sensitivity between tumor and normal tissue. In this treatment, the tumor is heated up to the therapeutic temperature between 42 and 45 C without overheating the surrounding normal tissues. We can enhance the treatment effect of other cancer treatments such as radiotherapy and chemotherapy by using them together with the hyperthermia. The interstitial microwave hyperthermia is applied to the localized tumor by inserting thin microwave antennas into the targeted tumor. In addition, an array applicator composed of few thin microwave antennas is employed for the treatment of large-volumed tumor. Therefore, we have investigated the array applicator composed of few coaxial-slot antennas, which are one of the thin microwave antennas. In this paper, first, the structure of the coaxial-slot antenna is explained. Then, the heating characteristics of the array applicator composed of four coaxial-slot antennas are introduced. Finally, the result of clinical trial by use of the presented array applicator is described.