Novel tumor‐ablation device for liver tumors utilizing heat energy generated under an alternating magnetic field

Abstract

We have developed a novel tumor-ablation device for liver tumors utilizing heat energy induced by magnesium ferrite (MgFe(2)O(4)) particles under an alternating magnetic field (AMF) produced by electric currents. This novel device can repeatedly heat liver tumors at lower temperature than usual heating devices, such as radiofrequency ablation therapy, with slight infliction of pain. This study assesses its heating effect on rat liver tumors as local therapy. The small needle was manufactured from MgFe(2)O(4) particles by sintering at 1100 degrees C. After a MgFe(2)O(4) needle was inserted into liver tumors comprising of dRLh-84 cells, the tumors were heated for 30 min under an AMF. We examined cellular activity by using nicotinamide adenine dinucleotide (NADH) diaphorase staining and terminal deoxynucleotidyl transferase-mediated digoxigenin-dUTP nick-end labeling (TUNEL) staining, and evaluated the effect of suppressing tumor growth by sequentially comparing the tumor diameter with that of the control group. The mean temperature of the heated tumors was 60.2 +/- 1.8 degrees C. The tumor cells were constricted, and chromatin of nuclei had shrunk immediately after heating. The heat-injury area that contained the tumors was negative for NADH diaphorase activity. After 3 days, the tumor cells in the heat-injury area became positive for TUNEL staining, which detects cell death. At 7 days, the mean tumor diameters were significantly smaller in the heating group than in the control group (6.15 +/- 0.47 mm vs 16.89 +/- 2.69 mm; P < 0.05). This device, utilizing heat energy induced by ferromagnetic metal under an AMF, appears useful as local thermotherapy for human liver cancer.