ABSTRACT
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°.
ABSTRACT
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.