Electromagnetic Applicators for Non-Invasive Local Hyperthermia

The methods with the greatest potential for inducing localised hyperthermia in cancer therapy are those involving electromagnetic fields with a frequency ranging from approximately 500 KHz to 2-3 GHz or ultrasound with a frequency in the range 500 KHz to 5MHz. Invasive methods using electromagnetic power and techniques based on ultrasound are described elsewhere in this book. In this chapter we shall restrict our attention to non-invasive electromagnetic techniques which operate at a frequency of a few MHz or higher. The wide variations in tumour structure, geometry and location encountered in the clinic have led to the development of a range of techniques involving capacitive, inductive or radiative transfer of electromagnetic power to the tissues. It should be noted that although such a classification is a useful tool when discussing the various types of applicator, in practice the boundaries between the various types are often indistinct.