Recent antenna technology for medical applications

In general, there are three major applications of antenna technology to the recent medical fields: (1) information transmission, (2) diagnosis and (3) treatment. Regarding the information transmission, wireless capsule endoscopy has already been used in our daily life. Wearable or implantable monitoring systems including RFID (radio-frequency identification) tags have widely been investigated and reported. As for diagnosis, antenna technology is indispensable to MRI (magnetic resonance imaging) or fMRI systems. Microwave CT (computed tomography) or radiometry will be another promising technique for noninvasive diagnosis. Thirdly, heat generated by radiation from antennas has been used for treatment. Hyperthermia and coagulation are typical thermal therapies for cancer treatment. In this presentation, three different types of antennas which have been studied in our laboratory are introduced. Firstly, a pretty small antenna for an implantable monitoring system is presented. An H-shaped cavity slot antenna is a candidate for such a system. Some numerical and experimental characteristics of the antenna are demonstrated. Secondly, some different antennas or "RF coils" for MRI systems are introduced. In addition, SAR (specific absorption rate) distributions in the abdomen of a pregnant woman generated in a bird cage coil are illustrated. Finally, after a brief overview of thermal therapy and microwave heating, coaxial-slot antennas and array applicators composed of several coaxial-slot antennas for minimally invasive microwave thermal therapies are introduced. Then a few results of actual clinical trials by use of the coaxial-slot antennas are demonstrated from a technical point of view. Other therapeutic applications of the coaxial-slot antennas such as hyperthermic treatment for brain tumor and intracavitary hyperthermia for bile duct carcinoma are introduced.