ABSTRACT
Objective To assess the influence of pre-exposure to non-ablating ultrasound on the effect of high intensity focused ultrasound(HIFU)ablation.Methods Forty rabbits with transplanted VX2 tumors on their livers were divided into three pre-exposure groups(60 W,80 W and 100 W)and a control group(O W),with 10 rabbits in each group.Each group was pre-exposed to lower intensity focused ultrasound at the corresponding power.From each group,5 rabbits were randomly selected to be exposed to HIFU on the next day.Each group received 14scans.The rabbits were sacrificed 24 h later to take tissue samples for tfipheny tetrazolium chloride(TTC)staining to measure the amount of coagulative necrosis.Hematoxylin and eosin(HE)staining and succinate dehydrogenase (SDH)were also measured to observe the structure and activation of pre-exposed tumors.Results After HIFU exposure,the ablated volumes increased with pre-exposure acoustic intensity,and all volumes were larger than those in the control group.The ablating efficiency in the 100 W group was the highest.The pre-exposure did not itself ablate tumor tissue,but in the 80 W and 100 W groups the structure and activation of the tissues changed.Those in the 60 W group were not obviously altered.Conclusion Prior exposure to non-ablating ultrasound can highly enhance the efficacy of HIFU ablation.