Magnetic nanoparticle-induced hyperthermia treatment under magnetic resonance imaging

Super paramagnetic iron oxide Fe₃O₄ nanoparticles prepared via photochemical reaction in pure form were used for inducing hyperthermia to treat subcutaneous Ehrlich carcinoma implanted in female mice. Our results indicate that the mean temperature profiles at the rectum, periphery of the tumor surface and at the center of the tumor during hyperthermia treatment increased gradually. The maximum temperature achieved in the tumor center was 47±1°C after 20 min with radiofrequency exposures at 25 kW. The acquired magnetic resonance images identified apoptotic cells in the center of the tumor which were exposed to magnetic resonance hyperthermia (MRH). Apoptotic cells presented as dark signal intensity in the T₁-weighted images which were further confirmed by pathological examinations. Also, the results revealed that the tumor size in the all mice exposed to MRH is still as the same as before the treatment, but the rate of tumor growth was very slow by comparing with the growth rate of the control group.