| HIFU ablation has become an effective method in the clinical treatment of benign and malignant solid tumors.The ablation efficiency is closely related to the size and location of the tumor,long time of HIFU irradiation and treatment to patients and doctors bring great challenge.Coverage to melt completely,applied at present in ablation area on the larger irradiation dose,treatment time is long,produce the complications such as such as skin burn injury and adjacent organs or increase of adverse reaction,serious impact on the safety,effectiveness of HIFU ablation mass.The edge of the malignant tumor invasive growth,micro capillary proliferation as "germinal layer" to the proliferation and metastasis;but internal regional organizations,in the case of low perfusion of ischemia hypoxia,there are varying degrees of necrosis.Aiming at this phenomenon,from the surrounding of the tumor,inactivated invasion growth bands,blocking blood flow,is expected to achieve the goal of treatment.In malignant tumor is interested area(ROI),using HIFU coagulation necrosis in the organization,in forming complete coagulation necrosis with surrounding the ROI,reduce the energy on the inner region,is expected to improve the efficiency of HIFU for large volume of tumor ablation,reduce the complications of the irradiation for too long.But the tissue degeneration necrosis,temperature rising,cavitation and vaporizing from HIFU ablation influence subsequent focal spot(lesion);The blood flow and the existence of breathing exercises,the establishment of models of necrosis with "shell closure" is incomplete.Many studies have shown that the nano micro bubbles can strengthen the energy deposition of HIFU;It is expected to be used to increase efficiency by HIFU ablation,improve the efficiency of melting.Therefore,on the basis of the previous studies,the purpose of the this topic is to using perfluoropentane drops-encapsulated mesoporous silica nanocapsules(MSNC-PFP)as HIFU synergist,seeking to achieve a smaller energy delivery can form a complete,adequate thickness of coagulation necrosis shell,in order to further improve the "surface of HIFU ablation model" and to provide the experimental basis.This topic research mainly includes the following two parts:Part I The area of injecting MSNC-PFP on the surface ablation of HIFU in vitro bovine liverObjective: To explore the influence of injecting MSNC-PFP on the linear scanning ablation in the HIFU ablation bovine liver in vitro experiments,contrast observe the influce of synergistic agent fully and gradually distributed in the ablation area on the surface melting,determining the strategy of the synergistic agent injection,laying the foundation for subsequent tests.Methods: Fresh ex vitro bovine was Selected after degassing and warm standby,continuous wave HIFU linear scanning way,and different power in turn from the depth of 40 mm to the shallow level,the strip echo appeared in the monitor the sonograms was used as a valid ablation,according to the width and height of linear coagulation necrosis,the parameters and combination of irradiation at different depth,the plan of ablation was developed;Five loci in linear scanning path design,site spacing of 10 mm,respectively in each point injection of MSNC-PFP(concentration of 1 mg/ml)immediately after HIFU irradiation,observation results of linear ablation;Surface ablation group was divided into blank control group,a one-time injection of synergistic agent group,several times synergisticinjection agent group,HIFU irradiation immediately after injection.Coagulation necrosis with the formation of surface models of necrosis in six faces way shell layer,inner region does not directly to melt.After ablation,the liver was cut along the long axis and short axis acoustic beam,respectively melting range was measured,and the volume of coagulation necrosis was calculated and statistical analysed.Internal without ablation area,coagulation necrosis and the border area organization were taken to H&E staining.Results: A strip coagulation necrosis was performed with line scanning speed of 5 mm/s and HIFU power rang 140 W from 240 W at the depth of 14 mm,22mm,29 mm,35mm,40mm;the whole line of melting volume was enhanced by injecting synergistic agent at 40 mm line scanning path quartering site;The formation of coagulation necrosis band was more and more complete after ablation as planned in experimental group B,group C,and the thickness of coagulation necrosis of group C was greater than group B(P < 0.05),the control group coagulation necrosis was incomplete.A large thermal damage necrosis was fond in group B and control group internal area,exclude group C.Conclusion: Accroding to coagulation necrosis belt on ex-vivo bovine liver,the surface of ablation HIFU continuous wave linear scanning way that combination line-line into the face to the body with the internal area not direct melt is unsuccessful,necrosis barrier is discontinuous and poor fused;Fore and aft point injection of MSNC-PFP after ablation line with progressive increase,intermediate site injections of MSNC-PFP efficiency of coagulation necrosis of partial enlargement,beam five sites at the same time after the injection of MSNC-PFP can increase the whole line of ablation volume;After surface ablation,one-time injection synergist group,injections can more and more complete the formation of coagulation necrosis,and many times injection group formed by coagulation necrosis with thickness is more than a one-off injection group(P < 0.05),the control group coagulation necrosis with incomplete.Nano synergistic agent can form a complete holistic coagulation necrosis of shell layer,and one-off injection group can enhance the thermal damage in internal area tissue.Part II Effect of Nano synergistic agent concentration on the surface ablation of HIFU on ex-vivo bovine liverObjective: The quantity and the concentration of nano synergistic agent can bring different result of HIFU ablation,the former part had explored different ablation result caused by different injection way,this part was to explore the influence of concentration of the nano synergist on surface ablation of HIFU on ex-vivo bovine liver.Methods: 50 fresh ex vitro bovines were divided into group A(0.25 mg/ml)and group B(0.5 mg/ml),group C(1 mg/ml),group D(2 mg/ml)according to the injection concentration of synergistic agent,and blank control group E.The synergistic agent was injected along the plan under the monitoring of ultrasound image,and then each group was ablated with the same HIFU irradiation dose on the surface of the target,the inner region does not directly melting.ultrasonographic changes were observed.Then the beef liver was cut apart along the long axis of the beam after melting,the range of coagulation necrosis was observed,the volume and energy efficiency factor of coagulation necrosis were measured and calculated.Results: Strong echo of synergist agent was slightly appeared in group C,group D,but not in group A,group B.Strong echo appeared in HIFU irradiation area in each groups,the stronger and the bigger grey value change strip echo was appeared along with the increase of the concentration of the synergist.Except the control group with incomplete ablation area necrosis,experimental groups can form a complete coagulation necrosis.With the increase of synergistic agent concentration,coagulation necrosis caused by thickness broadening,ablation volume increases,the energy efficiency factor decreased;The heat produced in the melting of the ablation area spread,expand the dead volume,produce a broader than planned coagulation necrosis.Conclusion: The high concentration of nano synergist can produce strong echo and improve the grey value change of HIFU ablation on the ultrasonic image.The higher concentration of synergistic agent injection,the coagulation necrosis of HIFU continuous wave surface ablation on ex-vivo bovine liver is greater,and the area of necrosis extends to inner and outer of the ablation area. |
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