1990 Volume 6 Issue 1 Pages 29-37
Heating effects induced by extremely low frequency (ELF) pulse magnetic fields have been investigated with relation to an application to local hyperthermia. The pulse generator used in this experiment has been already registered as a Japanese patent number 1394207. The generator permits the pulse direct current to flow through the coil rapidly. Generating the pulse magnetic field is achieved by discharging the capacitor. Discharge of the capacitor is accomplished by triggering on the thyristor (SCR). Two types of coils for magnetic exposure are provided. One is an air-core coil with 40 turns, the other is a transrectal applicator with bar-shaped ferrite core coil. The peak-current to flow the air-core coil and the transrectal applicator coil were 110A and 300A respectively, at a frequency of 8Hz. Using an air-core coil under a condition to be isolated completely from temporo-facial area in rabbits, the ELF pulse magnetic force applied to the parotid glands of the rabbits for 30 minutes. Thirty minutes after the magnetic exposure, the mean temperature of the parotid glands was increased by 7.3°C, and up to 45.5°C, reached finally an equilibrium temperature (n=5). The heating effect in this experiment must be the inductitve heating for thermoelectric current generated by the ELF pulse magnetic field. In the same manner, after inserting a transrectal applicator into the rectum, the transrectal pulse magnetic exposure was initiated. Thirty minutes after the magnetic exposure, the mean temperature of the rectovesical pouch in rabbits was raised by 6.9 °C, and up to 44.6 °C, reached an equilibrium temperature (n=5). In case of transrectal magnetic exposure, not all heating effects are coming from inductive heating, an influence of its own self-heating of the applicator must be also considered. However, it is no problem practically in applying the transrectal local hyperthermia to clinical region. It is concluded that the ELF pulse magnetic heating can be used enough for practical application in local hyperthermia.
