Study of implants for intraoperative hyperthermia

At the present time hyperthermia is recognized as one of the most promising methods in the combined treatment of malignant tumors. Nevertheless, for the most of existing methods for heating of tumor tissues it is rather difficult to realize the exact localization of heat exposure. The aim of this study is to compare two types of implants for intraoperative local tumor bed hyperthermia carried out using induction heating in an alternating magnetic field of the sub-MHz range. Composite implants of the first type are created on the base of a self-curing plastic mass mixed with electrically conductive ferromagnetic particles. The second type of implant is a hollow object with thin walls that follows the shape of the tumor. Implants of this type are filled with a liquid metal non-magnetic alloy with melting point below room temperature. The model implants were heated in a self-designed inductor with a short cylindrical coil 35 cm in diameter. Biological tissues were modeled using an ultrasound gel. Experimental results show that both types of implants were heated in an external alternating magnetic field with a frequency of 90 kHz and an amplitude not exceeding 4 kA/m up to temperatures that allow both traditional hyperthermia (tissue heating to 41-45 °C) and thermal ablation therapy (tissue heating to temperatures above 50 °C). Good agreement between the experimental data and model numerical calculations was obtained.