Objective:To investigate the method of damage in target region and the advantages of high intensity focused ultrasound(HIFU)circumferential ablation. Methods:Bovine liver was taken as the research object and was divided into three groups. Both simulation calculation and experimental results were compared to observe the shape and size of necrosis volume in single exposure group after the irradiation. The same irradiation parameters were used and the irradiation intensity was dynamically adjusted at different depths to complete ablation experiments. Irradiation time and energy accumulation were analyzed in the experiments. Two-dimensional ultrasound images were collected after circumferential ablation;the ablated area with hyperechoic changes was measured and reconstructed

and compared with the macroscopic measurement of coagulation necrosis in the liver. Results:There was no obvious difference in the area and volume of coagulation necrosis between theoretical simulation and experimental results. A complete necrosis around the circumferential region of the targeted liver was observed in circumferential ablation

and an obvious hyperechoic change was observed on ultrasound imaging. The 3D reconstruction of ultrasound images in the treated region was established

and the margin was easily identified between the treated and untreated areas. Total irradiation time and total energy accumulation were significantly different between the two ablation modes(P <0.05). No statistical difference was observed between two measurements(P >0.05).Conclusion:Real-time ultrasound imaging can monitor volume of the target in circumferential HIFU ablation procedure. Circumferential HIFU ablation mode can improve the efficiency of ablation

shorten the time of irradiation.