| The role of cardiovascular 3D model in reconstructing cardiac anatomy can no longer meet the needs of diagnosis and treatment of cardiovascular diseases.Especially with the aggravation of the aging population in China,more and more elderly patients with cardiovascular diseases have high mortality due to the combination of other organ diseases,physical failure or poor cardiac function,resulting in many elderly patients losing the opportunity for surgery.Therefore,the development of various intracardiac interventions is imminent.However,due to the impact of blood flow shock,the release of intracardiac devices is prone to displacement,and the success rate is low.It is necessary to accumulate rich experience in locating and balancing points during release.At present,the static cardiovascular 3D model can not meet the need of simulating interventional operation,therefore,the simulation materials similar to the mechanical properties of heart structures should be screened out,the simulated cardiovascular model should be exhaustively research and development,the mock circulatory system should be established.Only in this way,the authenticity and accuracy of simulating intracardiac interventional operation can be restored to the greatest extent,the possible problems during operation can be predicted,and the complications after operation can be evaluated.It also can be used for the development,testing and improvement of intracardiac devices.The main soft materials available in the market for cardiovascular 3D printing are silicone and rubber-like materials.Among them,rubber-like materials can be used for direct printing with stable performance.The shortcomings of these materials are material calibration based on aorta,which can not well imitate myocardium and valves.Silicone material is more flexible,but it needs to be molded.The structure of cardiovascular system is complex.The traditional printing method of mold modeling can not meet the requirement of high accuracy of cardiovascular 3D model.Therefore,the existing 3D printing rapid prototyping materials on the market can not meet the requirement of structural simulation and material simulation of cardiovascular 3D model at the same time.Previous studies have shown that three-dimensional transesophageal echocardiography(3D-TEE)can be used as a data source for cardiovascular 3D printing,and its accuracy has been fully verified.Especially,the application of Doppler echocardiography on cardiac hemodynamics parameters are the basis for setting parameters of personalized mock circulatory system.In this study,rapid prototyping materials closest to the mechanical properties of myocardial tissue in vivo were screened out by multiple detection methods.We also explored a more suitable method for the formation of complex cardiovascular structures.Based on transesophageal echocardiography(TEE),the 3D imaging of left atrial appendage(LAA)was completed and LAA 3D models with different soft materials were obtained.Placed in dynamic fluid in vitro,the left atrial appendage occlusion(LAAO)were simulated,the advantages of different soft materials LAA models were evaluated.Based on the myocardial tissue-like materials,the study moved forward to obtain the complete left atrium model including left atrium,four pulmonary veins and LAA,improved the mock circulatory system and simulated the LAAO.The accuracy and clinical application value of the mock circulatory system was evaluated.It also lay a foundation for the establishment of the personalized mock circulatory system with simulated complete heart 3D model.There are four parts in this study:Part 1: Screening,rapid prototyping and simulation test of myocardial tissue-like materials.Part 2: Accuracy analysis of left atrial appendage 3D models with different soft materials.Part 3: Accuracy of the left atrial appendage 3D models with different soft materials to simulate left atrial appendage occlusion in dynamic fluid in vitro.Part 4: Feasibility study of mock circulatory system with integrated left atrial 3D model for guiding left atrial appendage occlusion.Part 1: Screening,Rapid Prototyping and Simulation Test of Myocardial Tissue-like MaterialsObjectiveRapid prototyping materials with similar mechanical properties to normal myocardium were screened out to lay a material foundation for the construction of simulated heart model.MethodsBased on silicone and hydrogel in a certain proportion,the hardness of the mixture was adjusted by dimethyl silicone oil and soluble starch.With normal myocardium as reference,the best ratio of silicone and hydrogel was obtained through hardness and elasticity test.The mechanical properties of silicone-hydrogel mixture,silicone and rubber-like materials such as Tangoplus were tested by mechanical tests and ultrasonic shear wave elastography.Establish a rapid prototyping material fidelity score table,ask clinical doctors to score the three materials blindly,and finally screen out the rapid prototyping soft materials which mechanical property is most close to the normal myocardium.Results1.After mixing silicone and hydrogel in a certain proportion,add dimethyl silicone oil and soluble starch,the mixture can solidify and tested successfully.2.The shear wave velocity of myocardial tissue at the instant of cardiac arrest in dogs were obtained by shear wave elastography.3.Comprehensive analysis of the test results shows that the elastic modulus and shear wave velocity of the silicone-hydrogel mixtures are closer to the myocardial tissue.The tensile strength of the silicone-hydrogel mixture,silicone materials and Tangoplus materials are not significantly different from the myocardial tissue.The hardness of the silicone-hydrogel mixtures and silicone materials is similar to the myocardial tissue.4.Obtained the stress-strain curves of silicone-hydrogel,silicone and Tangoplus materials.5.According to the comprehensive statistical analysis of the rapid prototyping materials fidelity score table,the mixed materials of silicone-hydrogel are superior to those of silicone and Tangoplus materials in terms of hand-feeling fidelity(elasticity/hardness),cut-off fidelity and suture fidelity.Conclusion1.Silicone-hydrogel mixture is similar to myocardium in mechanical tests and ultrasonic shear wave elastography test.It can be used as myocardial tissue-like materials and basic materials for cardiovascular system 3D printing.2.Ultrasound shear wave elastography can be used to detect the elasticity of myocardial tissue in vivo.It is a useful attempt to apply elastography to cardiovascular system.Part2: Accuracy Analysis of Left Atrial Appendage 3D Model with Different SoftMaterialsObjectiveTo explore the feasibility and accuracy of left atrial appendage(LAA)3D models using three different rapid prototyping soft materials(Silicone-hydrogel,Silicone,Tangoplus)and two printing methods(mold modeling and direct printing)based on transesophageal echocardiography(TEE)images.MethodsTwenty-one patients with non-valvular atrial fibrillation underwent TEE before transcatheter left atrial appendage occlusion(LAAO).Two-dimensional and threedimensional volume images of LAA were collected.After post-processing,and STL files of LAA 3D volume images were obtained.The STL files are input into Stratasys Objet Eden 500 V polymer jet printer,and Tangoplus LAA models is directly printed.Computer aided design software(3-Matic Research 11.0)was used to design appropriate moulds according to the corresponding LAA STL files.PVA was used to print out the moulds.Silicone LAA models were obtained with mold modeling method.Silicone-hydrogel LAA models were obtained by the certain proportion found in the first part with mold modeling method.The opening diameter,anchoring area diameter and depth of those LAA models and LAA 3D-TEE images were measured.The measurements were compared and analyzed between groups to verify the feasibility and accuracy of the models obtained by using soluble mold modeling.Results1.The 3D LAA images were reconstructed successfully base on TEE images.Silicone-hydrogel LAA models,silicone LAA models and the corresponding internal structure models were obtained at the same time by soluble mold modeling.Tangoplus LAA models were obtained by direct printing.2.After analysis the measurments of opening diameter,anchoring area diameter and depth of silicone-hydrogel LAA models,silicone LAA models,Tangoplus LAA models and 3D TEE LAA images,there were no significant difference among the groups(P > 0.05).3.Bland-Altman scatter plot shows that there are three data points(4.7%)outside the consistency bound between silicone-hydrogel LAA models and 3D-TEE measurements,two data points(3.2%)between silicone LAA models and 3D-TEE measurements,and four data points(6.3%)between Tangoplus LAA models and 3DTEE measurements.The consistency bound were(-0.55 mm,0.39 mm),(-0.54 mm,0.34 mm),(-0.39 mm,0.43 mm),respectively.Conclusion1.There is no significant difference between the measurements of the Tangoplus 3D models obtained by direct printing and silicone-hydrogel LAA models,silicone LAA models obtained by soluble mold modeling,and the measurements of siliconehydrogel LAA models,silicone LAA models and Tangoplus LAA models have good consistency with LAA 3D-TEE images.2.The soluble mold modeling method can obtain LAA exterior models and LAA inner structure models simultaneously,it can be used as the preferred method for 3D printing of cardiovascular system.Part 3: Accuracy of 3D Models of Left Atrial Appendage with Different Soft Materials to Simulate Left Atrial Appendage Occlusion in Dynamic Fluid in vitroObjectiveThree different soft material models of left atrial appendage(LAA)were placed in dynamic fluid in vitro to simulate the left atrial appendage occlusion(LAAO).The accuracy and application value of three materials of LAA 3D models were evaluated by comparing the occluder selection,release,compression ratio and residual leakage around the occluder with intraoperation.MethodsThe silicone-hydrogel LAA models,silicone LAA models and Tangoplus LAA models of 21 patients were placed in the dynamic fluid in vitro.The flow velocity at the opening of LAA was individually set.The occlusion operation was simulated to predict the type of occluder.Twenty-one patients with atrial fibrillation who underwent LAAO were monitored by TEE.The LAA images after release the occluder were collected and processed,measured the compression ratio of the occluder and residual leakage around the occluder.With the same type occluder as in surgery,the compression ratio of occluder and residual leakage around the occluder in silicone-hydrogel LAA models,silicone LAA models and Tangoplus LAA models were obseved and contrasted with intraoperative measurements.Results1.The silicone-hydrogel LAA models,silicone LAA models and Tangoplus LAA models of 21 patients in dynamic fluid in vitro were successfully constructed and compeleted the LAAO simulation.The size of occluder predicted by silicone-hydrogel LAA models were closer to the occluder size used in the operation.2.With the same size of occluder,there was no significant difference between the compression ratio of the occluder in silicone-hydrogel LAA models and intraoperative(P > 0.05).The compression ratio of the occluder in the silicone LAA models and Tangoplus LAA models were larger than that of intraoperative.The correlation between the compression ratio of occluder in silicone-hydrogel LAA models and intraoperative(r=0.902,P<0.01)were better than that in silicone models(r=0.783,P<0.01)and Tangoplus models(r=0.765,P<0.01).3.Observed and measured residual leakage around the occluder in those models,four cases of residual leakage were found in the silicone-hydrogel LAA models,five cases in silicone LAA models and Tangoplus LAA models,and seven cases in the operation of LAAO in patients.Conclusion1.Establishment of a dynamic fluid system based on LAA 3D models to simulate LAAO is helpful for preoperative decision-making,simulation exercises and postoperative evaluation.2.Preoperative simulation system of LAAO based on silicone-hydrogel LAA 3D models has better clinical application value.Part 4: Feasibility Study of Mock Circulatory System with Integrated Left Atrial3D Model for Guiding Left Atrial Appendage OcclusionObjectiveTo establish a mock circulatory system with integrated simulatied left atrial model,improve the accuracy and authenticity of left atrial appendage occlusion.It is also a preliminary exploration for establishing a mock circulatory system with integral heart 3D model.MethodsTransesophageal echocardiography(TEE)and color Doppler flow imaging(CDFI)were performed in patients with atrial fibrillation before the percutaneous left atrial appendage occlusion(LAAO)operation.Relevant parameters such as left atrial pressure and flow velocity in left atrial appendage were detected by CDFI.Cardiac CT examination was performed before operation and CT images were post-processed.Integrated left atrial 3D image modeling including four pulmonary veins and left atrial appendage was completed and stored as STL file.The integrated left atrial model was obtained using the silicone-hydrogel metarials screened in the first part by soluble mold modeling method.After connecting with the external power device,the external power device was adjusted according to the blood flow parameters measured by CDFI to realize the pulsation of the left atrial appendage,and the LAAO was simulated under TEE monitoring.ResultsThe integrated left atrial 3D model including four pulmonary veins and left atrial appendage was successfully acquired.After connecting with the external power device,the mock circulatory system was completed,the external pulsation of the LAA 3D model was reproduced,and the LAAO was successfully simulated in the mock circulatory system.ConclusionIndividualized mock circulatory system with simulated integrated left atrial model can improve the accuracy and authenticity of LAAO operation,it also lays a foundation for the establishment of mock circulatory system system of integral cardiac model,thereby improving the clinical application value of cardiovascular 3D printing. |
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