The histological classification of rabbit liver treated with high intensity focused ultrasound

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

INTRODUCTION

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 SonoVuer (Bracco, Milan, Italy).

METHODS

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.

RESULTS

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.

CONCLUSION

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.

Study of sequential histopathologic changes, apoptosis, and cell proliferation in rabbit livers after high-intensity focused ultrasound ablation

OBJECTIVE

The purpose of this study was to investigate the sequential changes of rabbit liver tissue after high-intensity focused ultrasound (HIFU) ablation in histopathologic characteristics, apoptosis, and expression of proliferating cell nuclear antigen (PCNA).

METHODS

Thirty-five rabbits were anesthetized and received HIFU ablation on livers after laparotomy. Rabbits were killed at 0, 1, 24, 72, 144, 216, and 336 hours after HIFU ablation. The livers were cut off and examined under a light microscope with hematoxylin-eosin staining and under a transmission electron microscope. Proliferating cell nuclear antigen expression was detected by immunohistochemical staining, and apoptosis was observed by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling (TUNEL).

RESULTS

After HIFU ablation, fibra bands were detected under the light microscope in the rim of targeted areas after 72 hours, and the band became wide sequentially. Cells labeled by TUNEL and PCNA-positive cells were detected to different extents in surrounding tissues but not in targeted areas at 0, 1, 24, 72, 144, 216, and 336 hours after HIFU ablation. The apoptosis index detected by TUNEL reached a peak value at 72 hours after ablation, and the highest PCNA-positive index was found at 144 hours after ablation. Apoptotic bodies and oncotic mitochondria in surrounding areas were observed under the electron microscope.

CONCLUSIONS

After HIFU ablation, coagulated necrotic tissues became organized and fibra encapsuled gradually. Apoptosis and cell proliferation were detected in surrounding areas, which provided some implications for controlling HIFU treatment, although thermometry was not done to correlate the HIFU region with the cellular damage region, limiting correlation of the results.