Magnetic particles (
magnetite) were used to make radiofrequency (RF) capacitive
hyperthermia effective to a specific site. In an
agar phantom experiment, a
magnetite-containing
agar piece was buried in a large
agar phantom and 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 specific adsorption rate in the phantom was increased 1.5 times by the
magnetite particles. The temperature distribution in the large
agar phantom showed that the highest temperature was obtained at the center of the
magnetite-containing piece. The rate of temperature increase was approximately proportional to the
magnetite concentration to the power 0.8. This method was applied to an in vivo experiment using a pig.
Magnetite was prepared as a colloidal material dispersed in a
carboxymethylcellulose solution (CMC-Mag) and intramuscularly injected in the pig femur. As a result of 8 MHz-RF heating, the temperature at the CMC-Mag-injected point increased to over 43 degrees 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
magnetite-containing tissue was twice that of the
magnetite-free tissue. In addition, 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.