Histological evaluation of high-intensity focused ultrasound with lower-intensity focused ultrasound pre-exposure on the treatment of rabbit VX2 liver tumors

This study was to evaluate the effect of pre-exposure lower-intensity focused ultrasound(US), or LIFU, in high-intensity focused ultrasound(HIFU) ablation of rabbit VX2 liver tumors. Liver VX2 tumor models were established in 30 rabbits, which were divided randomly into two groups. The liver tumors of rabbits in Group A underwent single HIFU ablation; those in Group B were given LIFU exposure before HIFU treatment. Five rabbits from each of the two groups were sacrificed at 0 hours, 3 days, and 7 days after HIFU ablation. Tissue samples that included targeted and short-range sounding (s-RS, within 5 mm of the targeted) and far-range sounding (f-RS, more than 5 mm of the targeted) tissues were observed using light microscope and transmission electron microscopy. The histological examination indicated that not only the targeted tumor cells became irreversible damage, but also the short-range sounding tumors were severely damaged by the HIFU with LIFU pre-exposure in group B. It is concluded that LIFU pre-exposure can enhance the effects of HIFU ablation on the destruction of cell ultrastructures and can enlarge the region of HIFU ablation.