Development of Selective Localized Hyperthermia for Deep Seated Cancer with Magnetic Seramic Microspheres.

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Hollow ferrimagnetic microspheres are more suitable for hyperthermia of cancer than dense ones, since the former is hard to sediment in blood vessels. In Kyushu Institute of Technology, preparation of hollow magnetite microspheres was examined. Emulsion was prepared where iron hydroxide sol was dispersed in 2-ethyl-l-hexanol that are immiscible with water. The iron hydroxide sol was gelled in butanol by dehydration of the sol. The obtained powders were filtered and then subjected to heat treatments at different temperatures in vacuo. Microspheres ranging 10 to 100 μm in diameter were obtained. Most of the microspheres over 100 μm in diameter was broken, but not those under 50 μm in diameter. It was confirmed by powder X-ray diffraction that hematite, mixture of hematite and magnetite, and magnetite was formed by the heat treatment at 800, 1000 and 1150℃, respectively. The formed microspheres were confirmed to be hollow by SEM observation of their cross-sections. The results in this year show that hollow magnetite microspheres 20-30 μm in diameter suitable for the hyperthermia of cancer can be successfully obtained by the present method.We injected the ferrimagnetic microspheres into the rabbit kidney, and confirmed the local heating. In histological evaluation, the microspheres were uniformly distributed in renal tissue. Although temporary elevation of hepatic enzymes was detected, but no major adverse effect was detected in the rabbit's liver injections. We confirmed the feasibility of the injection into the beagle liver in the experimental procedures. Our ferrimagnetic microspheres appear safe and promising, and clinical application is highly encouraged. And we developed an automatic injection system in Department of Therapeutic Radiology ＆ Oncology, Kyoto University. Using the injector, the microsphere can be slowly injected, at same speed without overflow.