Development of inductive regional heating system for breast hyperthermia

In response to demand for clinical use, a simple noninvasive regional heating applicator system for breast hyperthermia has been developed using ferrite cores. Since the breast is positioned between a pair of ferrite cores, it is possible to regionally heat it without considering the dimension of the breast. To find a method of controlling the heating position horizontally and vertically, magnetic-held distributions are analyzed using the three-dimensional finite-element method. Theoretical analyses suggest that a conductive thin plate and a novel eddy current absorber are effective for controlling the maximum heating position. A new applicator system operates at a frequency of 4 MHz and a maximum output power of 600 W. Heating tests using an agar phantom and rabbits show a temperature rise of more than 8°C at a depth of 8 cm after heating for 10 min without heating fatty tissue.