Transmission electron microscopy of VX2 liver tumors after high-intensity focused ultrasound ablation enhanced with SonoVueA®

The purpose of this study was to observe sequential changes in rabbit VX2 liver tumors using transmission electron microscopy after high-intensity focused ultrasound (HIFU) ablation enhanced with the contrast agent SonoVuerA (R) (Bracco, Milan, Italy). Thirty New Zealand rabbits with VX2 liver tumors were randomly divided into two groups. The liver tumors of rabbits in Group A underwent single HIFU ablation; those in Group B were given the ultrasound contrast agent SonoVue 0.2 mL/kg before HIFU exposure. Five rabbits from each of the two groups were killed at 0 hours, 6 days, and 14 days after HIFU ablation. Tissue samples that included targeted and untargeted tissue were observed using transmission electron microscopy. Using transmission electron microscopy, it was evident that most of the cellular organs in the targeted areas of tumors in Groups A and B had disappeared early after HIFU, but the basic cell structure was seen in Group A. On the sixth day after HIFU ablation, all cells in the targeted areas were disrupted, and fibrous bands were detected in the rims of targeted areas in both groups. In the surrounding areas, cell swelling in Group B was more severe than in Group A, and a greater number of apoptotic bodies were found in Group B. The use of an ultrasound contrast agent can enhance the effects of HIFU ablation on the destruction of cell ultrastructure and can enlarge the region of HIFU ablation; this provides experimental evidence for the use of contrast agents in controlling the effects of HIFU.