No abstract

Objectives: To evaluate an implanted thermal ablation device that can be heated with high efficiency using a resonant circuit as the implant. Methods: 16 rats were used. The implants, adjusted at a resonance frequency of 4 MHz, were fixed on the surface of the liver of rats under laparotomy. In 14 of 16 rats, an alternating magnetic field (AMF) was applied for 6 min with an output of 300 W from outside the body using a ferrite core applicator. The implant temperature during AMF exposure was measured. The 14 rats were divided into 5 groups, depending on time from AMF application until they were sacrificed (1 h, 1 day, 3 days, 7 days and 1 month after application). Two rats not exposed to AMF were used as controls. Livers were removed and evaluated; the cross-sectional area and width of the ablated region were measured. Results: During AMF exposure, the implant temperature rose to 127.8¡39.3 u C (mean ¡ standard deviation). The cross-sectional area of the ablated region was largest after 1 day and tended to decrease with time. The widths of the ablated region were 4.87¡0.22 mm, 4.15¡0.36 mm, 3.67¡0.58 mm and 3.24¡0.16 mm in the 1 day, 3 day, 7 day and 1 month groups, respectively. No significant differences (p,0.05) were seen in either cross-sectional area or width of the ablated region. Conclusion: Sufficient heat for ablation was obtained in vivo using a newly developed implanted thermal ablation device. This device may be a new option for thermal ablation therapy.