Dextran magnetite complex (DM) is a colloidal suspension of subdomain particles that efficiently generates heat when exposed to an alternating current (AC) magnetic field. Inductive heating using DM has attracted attention as a new method that can overcome various problems associated with currently available techniques for local hyperthermia. This study was performed to clarify the usefulness of DM for oral cancer hyperthermia.
DM suspension was locally injected into the normal tongue and the tumor-bearing tongue of golden hamsters. The tongues were heated to 43.0-45.0°C by exposure to an AC magnetic field of 500 kHz. The following results were obtained:
(I) Experiment on heating of normal tongue
a) When DM was injected into the tongue in concentrations of 112, 56, and 42mg (as Fe/ml), the tongue temperature reached 43.0°C at 60, 120, and 570 seconds after treatment, respectively.
b) By injecting DM in a concertration of 56mg Fe/ml and changing the intensity of the AC magnetic field, the temperature in the tongue could be maintained at 43.0-45.0°C for 30 minutes. Furthermore, the temperature rise in the rectum, used as control, was only 0.4°C during this period.
c) Histological examination revealed brown uniform DM accumulation in the connective tissue between fibers of the tongue muscle.
(II) Experiment on heating of tumor-bearing tongue
d) The central and marginal temperature of the tumors reached 43.0°C at 180 and 540 seconds, respectively, and both temperatures were maintained at 43.0-45.0°C for 30 minutes.
e) An increase in tumor volume was associated with prolongation of the time required for the central temperature of the tumor to rise to 43.0°C.
f) Histological examination revealed the brown uniform accumulation of DM in the stroma at the tumor margin.
These results suggest that this local hyperthermic system may be useful in the oral region, where the tumor can be directly observed and palpated.
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