A new inductive applicator for hyperthermia.

We have designed a new type of applicator for inductive heating which consists of a one-turn, square, column-like coil, through which RF current flows. The material to be heated is placed alongside one of the external sides of the coil. The depth of penetration from an applicator with a height of 20 cm, width of 20 cm, depth of 60 cm was calculated to be 11.7 cm. However, in experiments using a muscle-equivalent agar phantom 60 cm X 60 cm X 60 cm, the penetration depth proved to be 9.6 cm; but in another experiment using a smaller phantom 20 cm X 40 cm X 60 cm, the penetration depth was 6.3 cm. This means that the depth of penetration depends not only on the size of the applicator but also on the shape of the material heated. Our study clearly showed that this applicator produces much less heat in the fat layer than in the muscle layer and should be an inductive applicator suitable for deep heating cancer therapy.