| The purpose of this study is to explore the feasibility of changing acoustic environment in tissue (AET) by some approaches in order to enhance energy deposition in target region when ablation with focus ultrasound (FU) or high intensity focus ultrasound (HIFU). The ultimate goal is to accumulate the experiences of ablation big animals' liver with HIFU in non-costectomy condition. New Zealand rabbits and goats were used in this study. By its targeting role to liver, HL-1(HIFU liposome 1, HL-1, a kind of fat emulsion)or HL-2(HIFU liposome 2, HL-2, a kind of iodinated lipid emulsion)can be accumulated in animal liver after injected intravenously. After that, its behavior of changing acoustic environment in tissue (CAET) of animal liver and the efficiency of enhancing ultrasound energy deposition, the mechanism as well as the influence to animal liver and renal function and the changes of liver pathology were investigated. 一.The experimental study on CAET of rabbit liver with HL-1 1.Thermogenic action of HL-1 together with liver Eighteen rabbits were randomly divided into two groups, the experimental group and control group with nine rabbits respectively. HL-1 or normal saline (NS) was injected in experimental group or control group. Then rabbits liver were ablated with focused ultrasound (FU, CZF-1) ex vitro under the parameters of power 5 W, frequency 6.5 MHz and impulse 1000 Hz two hours after HL-1 or NS was injected. The temperatures in target tissue were measured immediately with thermocouple probe after ablation. The focus length was ≤8 mm and the exposure time were 3 s,6 s,9 s,12 s and 15 s both in two groups. Conclusion:1.HL-1 can be accumulated in large quantities in rabbits liver by its natural targeting to liver after acute injection, and cause correspond architecture changes in rabbits liver. 2.The histological changes caused by HL-1 may increase the average tissue density of rabbit liver from 1.0547±0.0388g/cm-3 to 1.1217±0.0281g/cm-3. 3.The changes of tissue structure and texture of rabbits liver caused by HL-1 possess the effect of enhancing ultrasound energy deposition, it confirmed temperature in target tissue in experimental group were higher than those of control group in every exposure time(P<0.05).4.HL-1 acute injection possesses the function of CAET in rabbit liver. 2.The behavior of ultrasonograph in rabbits liver when HL-1 injection Forty rabbits were randomly divided into two groups, the experimental group and control group with 20 rabbits respectively. HL-1 (in experimental group) or NS (in control group) was injected intravenously, meanwhile, the behavior of ultrasonograph of rabbit liver in 40 cases were real-time monitored by B mode ultrasonography affiliated to HIFU treatment system, and its BUGs (B mode ultrasound greyscale, BUGs) were recorded. Liver biopsy was performed right after experiment. Conclusion:1.HL-1 injection may cause the decrease of BUGs in rabbit liver, it behaviors as the resonance decrease in parenchyma, ductwork and the envelope of rabbits liver. 2.Under certain speed of HL-1injection, the decreases of BUGs in rabbits liver were regular with time. 3. There should exist a quantitative saturation stage of HL-1 accumulation in rabbits, and this stage may be arrived 15~20min after HL-1 injection with the speed in this experiment, at this point, the value of BUGs was minima(-12.90±2.53). 4.The structure changes of rabbit liver caused by HL-1 and the high values of nonlinear parameter B/A of lipid may be the reasons of enhancing ultrasound absorption. 二.The experimental study of enhancing ultrasound energy deposition in rabbits liver with HL-1 1.The quantitative study of HL-1 for its synergistic action Fifty rabbits liver were ablated with HIFU (5500W/cm2) according to the group and side after NS and HL-1 were injected, the focus length were the same in all rabbits but with ablation time variant. The greyscale changes in target region and ablation time in every scanning place were recorded. The size of necrosis happened in rabbits liver were measured... |
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