Development of Heat Generating Magnetic Materials for Hyperthermia and Application to Medical Treatment

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The implant materials for hyperthermia of cancer tissues were developed and the clinical investigations were performed. Results of the research are summarized as follows :1. The corrosion resistance of the Fe-Pt alloy implant material for hyperthermia, which has low Curie point and large heat generation through the eddy current loss, is larger than that of a stainless steel. However, when the implant was embedded in the tissue of the thigh of a rabbit, the dissolved Fe element was a little bit detected in the X-ray analysis(1.0 x 10^<-4> g/cm^2 month).2. In order to prevent the alloy elements from dissolving, the biocompatible compound SiO_2 was coated on the implant using silane and phosphorus acid. The coating improved the corrosion resistance remarkably.3. The powder samples of Fe-Pt alloys were prepared as a heat generation materials through magnetic hysteresis loss. The heat generation of the powder material was enough to be used for hyperthermia. A spray-drying method was developed for the SiO_2 coating of the powder particles.4. The ceramic materials of CaO-MgO-Fe_2O_3 system whose elements are all biocompatible were investigated as new powder implant materials for hyperthermia. It was found that the materials of x=0.525 for (MgO)_<1-x>(Fe_2O_3)_x and y=1.0 for (CaFe_4O_7)_<1-y>(MgFe_2O_4)_y have the large heat generation through hysteresis loss which is several times larger than that of Fe_3O_4. The curie points of the materials are lower than that of Fe_3O_4.5. The clinical treatment for brain tumors and tongue tumors were tried for several cases using Fe-Pt alloy implants. The effects of hyperthermia were remarkable, 45.5% for brain tumors and 100% for tongue tumors.