Objective To discusse the influence of permeating perfluoropentane drops-encapsulated mesoporous silica nanocapsules (MSNC-PFP) on HIFU surface ablation in vitro bovine liver.Methods Fifity bovine liver tissues were divided into 5 groups:Control group,0.25 mg/ml group,0.50 mg/ml group,1.00 mg/ml group,2.00 mg/ml group according to the concentration of MSNC-PFP.The synergistic agent was injected along the ablation line path under the guiding of ultrasound.The surface ablation model was structured by 6 coagulation necrosis side by using HIFU linear scanning,inner region without melting,and the ultrasonographic changes were observed in the melt area.The coagulation necrosis range was assessed by TTC staining,and necrosis degree was observed by HE staining.The coagulation necrosis volume was measured,the coverage index (CI),external volume index (EI),energy efficiency factor (EEF) were used to evaluate the ablation effect in each group.Results The MSNC-PFP more than 1.00 mg/ml was shown as strong echo in ultrasonic image,fade after 3-5 min.The grey value was changed in HIFU ablation area related to the concentration of MSNC-PFP.The total ablation volume of 0.50 mg/ml group,1.00 mg/ml group,2.00 mg/ml group were more than control group,the EEF was lower than that of the control group (all P＜0.01).The CI and EI of 1.00 mg/ml group and 2.00 mg/ml group were higher than those of the other group (all P＜0.01).The coagulation necrosis became complete when the concentration of MSNC-PFP above 0.50 mg/ml.Conclusion MSNC-PFP can increase the volume of coagulation necrosis,decrease the EEF and increase the efficiency of HIFU surface ablation of bovine liver in vitro.

Objective To investigate the effect of blood vessels at different locations and angles between blood vessel and sonic axis within the target area on HIFU peripheral ablation.Methods Totally 56 phantoms containing rabbit thoracic a orta were divided into group A (different vessel locations) and B (different vessel angles).According to the distance (d)between the blood vessel center and the deepest (top) layer of the peripheral scanning,group A was divided into A1 (d=0),A2 (d=10 mm),A3 (d=20 mm) subgroups.According to the angle (α) between the vessel long axis and the acoustic axis,group B was divided into B1 (α=0-5°),B2(α=60° 65°),B3 (α=90°-95°),B4 (α=115°-120°) subgroups.A4,B5 subgroups were set as the control groups.The vessel diameter and vessel wall thickness were measured.The lesion morphology was observed and the energy efficiency factor (EEF) was calculated.Results There was no significant difference in vessel diameter and vessel wall thickness in both group A and B (all P＞0.05).There was no residual area in the target area of A1,B1 subgroup,while there was residual area in the target area of the other subgroups.EEF of group A in ascending order were A4,A1,A2 subgroup,and statistically significant differences in pairwise comparisons (all P＜0.05) except for A1 and A3 subgroup (P＞0.05).EEF of group B in ascending order were B5,B2,B3 subgroup,respectively,and statistically significant differences in pairwise comparisons (all P＜0.05) except for B2 and B4,B5 and B1 subgroup (both P＞0.05).Conclusion It is 10 mm that the distance between the blood vessel center and the deepest (top) layer of the pe ripheral scanning,and 90°-95° that the angle between the vessel long axis and the acoustic axis has the greatest influence on the ablation of the target area.

Objective To explore the impact of different angles between blood vessels and acoustic axis in the target area on pulse high intensity focused ultrasound (PHIFU) peripheral ablation.Methods Thirty New Zealand rabbits were selected,and the thoracic aortas were obtained.Models of tissue mimicking material were used via embedding the rabbit thoracic aorta into the center of the target barrier area.Then the models were divided into 0°,45° and 90° groups according to the angles with the acoustic axis,and the control group was set up as well (each n =10).Under B-ultrasound monitoring,PHIFU peripheral ablation was performed with the same parameters in each group.The temperature was measured during ablation.After ablation,the models were cut step by step for macroscopic and ultrasound observation.The total volumes (V) were calculated and compared,and the target blood vessels were sampled for pathological examination.Results The peripheral region in control group showed strong echo on ultrasound image,while in 0°,45° and 90° group the blood vessels showed low echo accordingly.The maximal temperatures in control group,0°,45° and 90° group was (98.60 ± 5.76) ℃,(98.90 ± 7.09) ℃,(71.10 ± 13.85) ℃ and (70.20 ± 9.14) ℃,respectively.Statisticaldifference was found between control group and 45°,90° group (all P＜0.05).The total volume in control group,0°,45° and 90° group was (40 709.70 ± 3 193.31) mm3,(40 029.02 ± 3 580.17) mm3,(34 562.59 ± 3 883.26) mm3 and (36 737.01± 3 278.68)mm3,respectively,while no statistical difference was found between control group and 0° group (P＞0.05).Pathological examination showed that the elastic fibers fractured partly,and disruption of cell nucleus were observed in 45° and 90° group.Conclusion When the angle between the blood vessel and acoustic axis is 0°,its impact on energy deposition is minimally,while the destruction of the vascular wall becomes stronger when the angle is 45°and 90°.