2003 Volume 19 Issue 2 Pages 79-87
Dextran magnetite complex (DM) is a colloidal suspension of subdomain particles which efficiently generate heat under an alternating current (AC) magnetic field. Inductive heating using DM has attracted attention as a new method to overcome various problems in existing local hyperthermia. To make the system more convenient for clinical application, we developed a new portable device.
The device can use an alternating current (AC) of 200V (maximum output 3kW), and it is extremely small, about 0.4×0.4×0.4 meters long. The frequency can be adjusted continuously within the range of 100-500kHz. DM suspension containing 14mg Fe/ml (0.25M), 28mg Fe/ml (0.5M) or 56mg Fe/ml (1.0M) was used in an in vitro study, referring to our previous studies. The results obtained were as follows. 1) The temperature of DM rose in proportion to the iron concentration of DM. 2) The temperature of DM rose in proportion to the square of the magnetic field intensity. The temperature elevations were about 8°C/min and 14°C/min at frequencies of 299kHz and 418kHz, respectively, using a DM of 28mg Fe/ml and a magnetic flux density of 5.2mT. These results were identical to the results of the heating characteristics in the previous device. Moreover, this device was evaluated for its anti-tumor effect in VX-2 tumor-bearing rabbits. By using hyperthermia treatment with this device, the inhibition of the tumor growth in the treated group (n=8) was significantly greater than in the control group (n=3), and the frequency of lung metastasis was decreased, too. Thus, this study confirmed the usefulness of this portable hyperthermic device for local cancer therapy.
