Effect of functional magnetic particles on radiofrequency capacitive heating

Magnetic particles (magnetite) were used to make radiofrequency (RF) capaci tive hyperthermia effective to a specific site. In an agar phantom experime nt, a magnetite-containing agar piece was buried in a large agar phantom an d heated by an 8 MHz-RF capacitive heating device. The magnetite-containing agar piece was heated more than the magnetite-free agar phantom, and the s pecific adsorption rate in the phantom was increased 1.5 times by the magne tite particles. The temperature distribution in the large agar phantom show ed that the highest temperature. was obtained at the center of the magnetit e-containing piece. The rate of temperature increase was approximately prop ortional to the magnetite concentration to the power 0.8. This method was a pplied to an ill vivo experiment using a pig. Magnetite was prepared as a c olloidal material dispersed in a carboxymethylcellulose solution (CMC-Mag) and intramuscularly injected in the pig femur. As a result of 8 MHz-RF heat ing, the temperature at the CMC-Mag-injected point increased to over 43 deg rees C after 7 min, while the temperature at a point without magnetite was under 40 degrees C at the same time. The specific adsorption rate in the ma gnetite-containing tissue was twice that of the magnetite-free tissue. In a ddition, the time required to reach a temperature of over 43 degrees C was only 7 min, while it was over 15 min in the case without the CMC-Mag.