| BackgroundEthanol is a widely used intravascular embolic agent in the field of interventional radiology,it’s hardly traced under X-ray fluoroscopy,therefore it often needs to be mixed with contrast agent in clinical procedures,resulting in concentration decline and uncertainty of embolization.Carbon dioxide,as a negative contrast agent,does not react with ethanol.Using the characteristics of the two substances,our team pioneered the prefilling of carbon dioxide and ethanol to the PE tube in a gas-liquid series pattern,and tested the possibility of using carbon dioxide as a tracer for ethanol.Part ⅠⅠObservation on physical properties of gas-liquid series embolic agent——carbon dioxide-ethanol.ObjectiveIn order to understand the physical properties as well as the imaging propertie’s under X-rays(that is,visibility)of the gas-liquid series embolic agent,a general observation was taken on this novel embolic agent--carbon dioxide ethanol prefilled PE tube,and X-ray imaging were conducted including radiogram,fluoroscopy and subtraction acquisition in vitro by means of digital radiography(DR)and digital subtraction angiography(DSA)system,simultaneously observing and recording the appearance changes of the gas-liquid series embolic agent within a certain period of timme to make a preliminary evaluation for further animal experiments.Materials and methods1.Materials:10 transparent polyethylene(PE)tubes prefilled with 75%ethanol solution and carbon dioxide in gas-liquid series pattern,all of which were 100cm in lengthy each section of the gas or liquid was around 1cm.2.In vitro digital radiography,fluoroscopy and subtraction were performed on 10 PE tubes with DR and DSA.Both imaging procedures were carried out under braking and moving the PE tubes respectively.The injection process of the contrast agent was simulated by manual traction of the tube or solution injection into the tube.An anthropomorphic phantom was overlaid on the tube when repeating the above imaging process to study the gas-liquid series at the thickness of the human body.3.Digital radiography was carried out after the PE tubes of prefilled gas-liquid series embolic agent had been delivered to the laboratory for one and two weeks.The length of gas and liquid sections in 9 PE tubes was measured by the built-in linear measurement tool of the PACS.The section length and the total length of gas and liquid of each tube at two time points were analyzed with statistical software.Results1.10 PE tubes with prefilled gas-liquid embolic agent were transparent.The gas and liquid columns can be distinguished by naked eyes,each section length being around 1cm.The photos taken before the experimental tubes being shipped showed that the section length of the gas and liquid in the tubes was relatively uniform.After air transportation,the section length was found to be nonuniform.2.Digital radiography can clearly show the arrangement of gas-liquid sections within the PE tubes,the liquid component(75%ethanol solution)was of higher density and the gas component(carbon dioxide)was of lower density.The image obtained by appropriately reducing the X-ray tube voltage can better display both the PE tube and its gas-liquid filler,and when an abdominal anthropomorphic phantom was overlaid for radiography,varying tissue densities produced concealing effect on the PE tubes to different extent.3.Amid simulating the interventional radiology procedure under fluoroscopy by DSA,no matter whether the PE tube was still or moving,or whether the phantom was overlaid,the contents within the PE tube cannot be clearly distinguished;the subtraction images obtained by simulating the progress of the catheter can display the gas-liquid sections and their movement.After overlaying the phantom,the gas-liquid sections were beyond recognition.4.Observation of gas-liquid changes in PE tubes:① The difference of section length of gas or liquid between 9 PE tubes was statistically significant after delivered to the laboratory one week and two weeks respectively(P<0.05).②The gas section length and liquid section length within each of the 9 PE tubes was analyzed after delivered to the laboratory at one week and two weeks respectively.Statistical significance between the gas section length and liquid section length was found in 4 PE tubes at two time points,the liquid section being longer than that of gas section was found in one PE tube at the second time point(P<0.05).③There was no statistical significance among these 9 PE tubes comparing their section length of gas or liquid at both one week and two weeks after delivered to the laboratory(P>0.05).④Total length of both gas and liquid sections of the 9 PE tubes were compared respectively at both one week and two weeks after delivered to the laboratory(P<0.05),the total length of liquid sections was statistically larger than that of gas sections.⑤There was no statistical significance among the 9 PE tubes comparing the total length of gas and liquid sections at both one week and two weeks after delivered to the laboratory(P>0.05).Conclusion1.Gas-liquid series embolic agent——carbon dioxide-ethanol,its X-ray imaging features are as follows:① the gas-liquid sections pattern within the PE tube can be well displayed by DR,the image quality can be modified by properly reducing the tube voltage.②Its low resolution under DSA fluoroscopy is not ideal for practice due to the small difference of X-ray attenuation between the two substances.With the current prefilling pattern,carbon dioxide cannot play the role in tracking for ethanol.2.After transportation and storage at room temperature in the laboratory,the gas and liquid in the tube mixed to a certain extent,and a small amount of carbon dioxide was lost.The sealing performance of the device needs to be further improved.Part ⅡExperimental arterial embolization with gas-liquid series embolic agentsObjectiveTo evaluate the practicability of gas-liquid series embolic agents in vivo interventional procedure,and to have the initial knowledge of the pathology caused by these kinds of embolic materials,three kinds of liquid embolic agent combined with CO2 were used in experimental rabbit renal arterial embolization.Materials and methods1.Two male healthy New Zealand rabbits were treated with renal artery embolization via the right common carotid artery approach,different formulations(C2H6O+CO2,75%C2H6O+Na2CO3+CO2,75%C2H6O+CO2)of gas-liquid series embolic agents were used respectively.Before and after the embolic agent was injected,the positive contrast agent iodroxol was injected as a reference to present the process of gas-liquid series embolic agent under fluoroscopy and subtraction.2.Following the renal arterial embolization,both kidneys were taken out immediately and observed thoroughly.Then the embolized kidney was fixed in formalin solution for 12 hours,then taken out and made pathological sections to exam microscopically.Results1.Angiographic performance of gas-liquid series embolic agent:transient bubble flow was detected fluoroscopically during embolizing left renal artery of rabbit 1 with C2H6O+CO2;bubble contraflow was found occasionally while embolic agent was hardly seen during embolizing left renal artery of rabbit 2 with 75%C2H6O+Na2CO3+CO2,similarly,75%C2H6O+CO2 could not be traced fluoroscopically during right renal arterial embolization of rabbit 2;all the three liquid embolic agent combined with CO2 were poorly developed in subtraction images.2.Acute pathological findings of rabbit kidney following embolization①Gross pathological findings:after embolization,kidneys were taken out for immediate observation,the embolized kidney was swollen with dark yellow ischemic area;after 12 hours of immersion in formalin solution,large extent of gray yellow change revealed while boundary between cortex and medulla was kept clear.②microscopical findings:degeneration and edema of renal tubulocyte was found in all the embolized kidneys.Broken elastic fiber of arterial wall was occasionally found in left kidney of rabbit 1.Infarction was found In the right kidney cortex of rabbit 2.Conclusion1.This experiment shows that the gas-liquid embolic agents needs to be further modified to achieve a better imaging quality for interventional practice.2.All of three liquid components prefilled in PE tube could cause degeneration and edema of renal tubular cells,leading to edema of small artery wall. |
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