Iodized oil enhances the thermal effect of high-intensity focused ultrasound on ablating experimental liver cancer

The influence of the biological medium on high-intensity focused ultrasound (HIFU) therapy for ablating experimental liver cancer was studied. In study 1, the temperature rise in the focal zone in the presence of iodized oil or castor oil was observed in vitro. The results showed that HIFU with iodized oil produced a higher and faster temperature rise than did HIFU with castor oil, whether high-power (500 W/cm2) or relatively low-power (136 W/cm2) conditions were used (P=0.0008 and P=0.0004 respectively). With the excised liver samples, the temperature also rose higher and more rapidly after injection of iodized oil into the liver than when castor oil was injected (P=0.0239), and the target liver tissue revealed more radically and extensive destruction with iodized oil than with castor oil. In study 2, 48 nude mice, bearing primary liver cancer LTNM4 implanted subcutaneously, were randomly divided into four groups. Group I (n=12) were the controls, group II (n=12) were injected with iodized oil alone, group III (n=12) received HIFU treatement, and group IV (n=12) were exposed to HIFU after iodized oil injection. Significant inhibition of tumor growth was seen in groups III and IV as compared with group I or group II (P<0.05), the tumor growth inhibition rate on the 28th day after treatment being 87% and 93% respectively. Significantly improved survival was noted in groups III and IV compared with groups I and II (P<0.05). Histologically, group IV showed more complete tumor necrosis than did group III. These data suggest that HIFU combined with iodized oil might have achieve of synergism, location and targeting in the treatment of liver cancer.