The influence of blood supply on high intensity focused ultrasound a preliminary study on rabbit hepatic VX2 tumors of different ages.

RATIONALE AND

OBJECTIVES

The aim of this study was to explore the effects of blood supply on high-intensity focused ultrasound (HIFU) applied to rabbit hepatic VX2 tumors of different ages.

MATERIALS AND

METHODS

Eighteen rabbits with VX2 hepatic tumors were randomly divided into three groups according to the time of sacrifice after tumor implantation: 10, 15, or 20 days. Contrast-enhanced ultrasound was performed immediately before HIFU ablation. The same settings for HIFU dose parameters were used to ablate the central tumor area in each group, and the real-time temperature of the targeted site of the tumor was measured. After HIFU, the coagulation necrosis volumes of tumor tissue and the microvascular density of residual tumor tissue were determined.

RESULTS

Histopathologic analysis showed that the extent of a tumor's blood supply followed the order 10-day group > 15-day group > 20-day group (P < .01). Contrast-enhanced ultrasound showed the same results. There was no statistically significant difference among the three groups in terms of temperature-increase parameters during HIFU treatment (P > .05). However, there were statistically significant differences between the groups in terms of temperature-decrease parameters during HIFU treatment and in terms of necrosis volumes after HIFU treatment (P < .05). Necrosis volume was inversely related to absolute enhanced intensity (r = -0.823, P < .001).

CONCLUSIONS

The extent of a tumor's blood supply had a significant effect on the temperature-decrease phase but not on the temperature-increase phase during HIFU treatment. The longer the temperature-decrease phase, the more slowly heat dissipated after HIFU, resulting in larger coagulation necrosis volumes.