Development of Cancer Ablation System using the High-frequency Inductive Heating of Ferrite Powder

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An attempt has been made to develop a cancer ablation therapy applying the high-frequency inductive heating of the ferrite powder, as a cooperative approach from medical, physical and engineering fields. The Mg ferrite powder was prepared by the reverse coprecipitation method using metal nitrates as the starting materials. In the instillation of the ferrite powder into a tumor, it is indispensable to obtain a magnetic fluid consists of nano-scale particles. Thus, we investigated the dispersion ability of the magnetite powder prepared by the reverse coprecipitation method. Controlling their pH value by the addition of hydrochloric acid, a significant improvement of dispersion ability was achieved in the range from pH1 to pH3.The heating properties of both the needle-shaped Mg ferrite obtained using a sintering technique and the Mg ferrite powder packed into the Ti tube were measured in the magnetic field of 1.77kA/m at 370kHz. The increase in temperature (ΔT) reached 16 ℃ for the former inserted in the cylindrical clay. The ΔT value of three complementary Mg ferrite sticks was as high as 40℃ at the central position, suggesting that the heating ability of these magnetic materials is sufficient for the ablation of liver tumor. Although the Ti tube without the Mg ferrite powder or Ti rod exhibited poor heat generation ability, the ΔT of the latter was markedly improved by the existence of Mg ferrite powder in the Ti tube. The apparatus for the high-frequency inductive ablation of liver cancer was produced on trial for the clinical testing on patients. The experiments on rats and rabbits allowed us to conclude that the usage of the Mg ferrite powder to the thermal coagulation therapy is effective owing to the large heat generation ability in the high-frequency magnetic fields.