Focusing system of burst electromagnetic waves for medical applications

Bioelectrics has attracted much attention. Inducing apoptosis in malignant cells using subnanosecond pulses has previously been investigated; these results have encouraged the authors to develop a burst electromagnetic wave focusing system for cancer treatment through the induction of apoptosis to cells. Burst electromagnetic waves are characterized by a high-frequency and narrow band signal over a very short duration. This system consists of a radiating antenna and an ellipsoidal reflector which focuses radiation waves. The ellipsoidal reflector has the characteristic of focusing burst electromagnetic waves radiated from the first focal point to the second focal point, thus enhancing the electric field at the second focal point. This system is immersed in heated water to avoid permittivity mismatch between living tissue and the water in which electromagnetic waves propagate, thus reducing reflection and refraction at the surface of biological tissue. This paper presents experimental and simulated results purposed on narrowing focusing point area. The focusing of burst electromagnetic wave at the second focal point was confirmed by preparing a distribution map of electric fields. The experiment and simulation compared three types of transmitting antenna: sleeve, brown and discone antennas. The discone antenna was found to give the shortest FWHM of the electric field distribution. Attenuation of burst electromagnetic waves by biological tissue was investigated using pig tissue: skin, fat and muscle. Attenuation by muscle was found to be greatest. Thicker tissue was found to lead to greater attenuation.