基于醫(yī)學(xué)影像的鎳鈦合金膨出式支架的設(shè)計與性能研究
發(fā)布時間：2019-01-29 20:56
【摘要】：主動脈夾層是異常兇險的主動脈高危疾病,嚴(yán)重影響人們的健康與正常生活。我國主動脈疾病以主動脈夾層為主。主動脈腔內(nèi)支架修復(fù)術(shù)(TEVAR)能夠有效封堵夾層近端破口,促進假腔血栓化。主動脈覆膜支架作為TEVAR治療的主要器械,承擔(dān)重建血液通路、加快血管重塑等重要作用。夾層患者的醫(yī)學(xué)影像是選擇合適的支架規(guī)格的重要依據(jù),也是未來個性化支架設(shè)計參數(shù)的重要來源。覆膜支架植入后的力學(xué)性能表現(xiàn)是主動脈疾病療效的重要評價指標(biāo)。有限元分析技術(shù)作為一種體外模擬研究方法,在醫(yī)學(xué)領(lǐng)域已獲得廣泛應(yīng)用。通過有限元分析,能夠?qū)χЪ苤踩牒蟮氖芰顟B(tài)進行較為全面的評價與預(yù)測。本課題根據(jù)夾層患者術(shù)后遠(yuǎn)端返流的現(xiàn)象,基于患者的醫(yī)學(xué)影像數(shù)據(jù),創(chuàng)新性提出一種變截面式鎳鈦合金覆膜支架,通過膨出段與夾層內(nèi)膜相互緊貼并對夾層內(nèi)膜施加一定壓迫,加速假腔近端血栓化,達到積極的治療效果。通過對患者醫(yī)學(xué)影像的提取與處理,能夠獲得夾層病變的重要尺寸參數(shù)與形態(tài)參數(shù),能夠指導(dǎo)合適支架的設(shè)計與選擇。通過有限元分析得出幾何參數(shù)對支架的徑向支撐力性能具有重要影響:增加支架絲徑與膨出段支架環(huán)個數(shù),可以提高膨出段支架的支撐性能,增加膨出段長度則會使支撐性能降低;當(dāng)膨出段支架的膨出度為8 mm時,其支撐性能為較好水平;幾何參數(shù)影響程度由大至小依次為絲徑、膨出段長度、支架環(huán)個數(shù)、膨出度。通過靜力學(xué)計算與誤差分析,得到相應(yīng)支架的理論徑向支撐力值與誤差范圍,對支架的設(shè)計與改進提供一定的理論基礎(chǔ)與幫助。在本實驗條件下,根據(jù)設(shè)計理念篩選獲得的較優(yōu)組合為絲徑中0.5mm,膨出段長度50mm,膨出段上支架環(huán)個數(shù)3個,膨出度12 mm。通過對夾層內(nèi)膜的力學(xué)性能測試,獲得相應(yīng)的力學(xué)性能參數(shù),為支架合理的參數(shù)選擇提供重要評價標(biāo)準(zhǔn):通過改變支架幾何參數(shù)提高支架支撐性能時,其設(shè)計徑向支撐力不能超過夾層內(nèi)膜或者主動脈血管壁的生理承受極限,防止因支架力學(xué)性能不匹配產(chǎn)生的嚴(yán)重術(shù)后并發(fā)癥。CFD流體動力學(xué)的模擬結(jié)果表明,遠(yuǎn)端破口未及時處理時,離支架末端較近的破口有可能成為新入口,持續(xù)為下段夾層假腔提供灌注;而膨出式支架能夠有效阻斷夾層假腔破口的返流現(xiàn)象。體外流體模型的觀測結(jié)果能夠較好地驗證CFD流體模擬結(jié)果的有效性。
[Abstract]:Aortic dissection is an extremely dangerous high-risk disease of aorta, which seriously affects people's health and normal life. Aortic dissection is the main disease of aorta in China. Endovascular stent repair (TEVAR) can effectively close the proximal break of the dissection and promote pseudo-lumen thromboembolization. As the main instrument of TEVAR, aortic stent graft plays an important role in reconstructing blood pathway and accelerating vascular remodeling. Medical imaging of dissection patients is an important basis for selecting appropriate stent specifications and an important source of personalized stent design parameters in the future. The mechanical performance of stent implantation is an important index to evaluate the curative effect of aortic disease. Finite element analysis, as an in vitro simulation method, has been widely used in the field of medicine. Through finite element analysis, the stress state of the scaffold can be comprehensively evaluated and predicted. According to the phenomenon of distal regurgitation in patients with dissection and based on the medical image data of the patients, a new type of nickel-titanium alloy coated stent with variable cross-section was proposed. In order to accelerate the thromboembolization of the proximal pseudo-lumen, a positive therapeutic effect was achieved by pressing the intima of the dissection by pressing the swelling segment closely to the intima of the dissection. Through the extraction and processing of medical images of patients, the important size parameters and morphological parameters of dissection lesions can be obtained, and the design and selection of suitable scaffolds can be guided. Through finite element analysis, it is concluded that geometric parameters have an important effect on the support performance of the support: increasing the diameter of the wire and the number of rings in the extruding section can improve the support performance of the extruded bracket. Increasing the length of the extruded section will reduce the support performance. When the extruding degree of the extruded bracket is 8 mm, the support performance is better, and the influence degree of geometric parameters from big to small is the wire diameter, the length of the extruded segment, the number of the bracket rings and the expansion degree. Through static calculation and error analysis, the theoretical radial support force and error range of the corresponding support are obtained, which provides a certain theoretical basis and help for the design and improvement of the support. Under the experimental conditions, the optimum combination is 0.5 mm in diameter, 50 mm in length, 3 rings in the extruded segment, and 12 mm. in the extruded section, according to the design concept. The optimum combination is 0.5 mm in diameter, 50 mm in length of extruding segment, 3 in the number of bracket rings on the extruded segment, and 12 mm. in expansion degree. Through testing the mechanical properties of the interlayer inner membrane, the corresponding mechanical performance parameters are obtained, which provides an important evaluation criterion for the reasonable selection of the support parameters: when the support performance is improved by changing the geometric parameters of the scaffold, The designed radial supporting force should not exceed the physiological endurance limit of the dissecting intima or the aortic vascular wall and prevent the serious postoperative complications caused by the mismatch of the mechanical properties of the stent. The simulation results of CFD fluid dynamics show that, When the distal break is not treated in time, the break near the end of the scaffold may become a new entrance, which will continue to provide perfusion for the lower segment of the false chamber. The extruded bracket can effectively block the reflux phenomenon of the break in the false cavity of the interlayer. The observational results of the external fluid model can well verify the validity of the CFD fluid simulation results.
【學(xué)位授予單位】：北京有色金屬研究總院
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：R318.08
[Abstract]:Aortic dissection is an extremely dangerous high-risk disease of aorta, which seriously affects people's health and normal life. Aortic dissection is the main disease of aorta in China. Endovascular stent repair (TEVAR) can effectively close the proximal break of the dissection and promote pseudo-lumen thromboembolization. As the main instrument of TEVAR, aortic stent graft plays an important role in reconstructing blood pathway and accelerating vascular remodeling. Medical imaging of dissection patients is an important basis for selecting appropriate stent specifications and an important source of personalized stent design parameters in the future. The mechanical performance of stent implantation is an important index to evaluate the curative effect of aortic disease. Finite element analysis, as an in vitro simulation method, has been widely used in the field of medicine. Through finite element analysis, the stress state of the scaffold can be comprehensively evaluated and predicted. According to the phenomenon of distal regurgitation in patients with dissection and based on the medical image data of the patients, a new type of nickel-titanium alloy coated stent with variable cross-section was proposed. In order to accelerate the thromboembolization of the proximal pseudo-lumen, a positive therapeutic effect was achieved by pressing the intima of the dissection by pressing the swelling segment closely to the intima of the dissection. Through the extraction and processing of medical images of patients, the important size parameters and morphological parameters of dissection lesions can be obtained, and the design and selection of suitable scaffolds can be guided. Through finite element analysis, it is concluded that geometric parameters have an important effect on the support performance of the support: increasing the diameter of the wire and the number of rings in the extruding section can improve the support performance of the extruded bracket. Increasing the length of the extruded section will reduce the support performance. When the extruding degree of the extruded bracket is 8 mm, the support performance is better, and the influence degree of geometric parameters from big to small is the wire diameter, the length of the extruded segment, the number of the bracket rings and the expansion degree. Through static calculation and error analysis, the theoretical radial support force and error range of the corresponding support are obtained, which provides a certain theoretical basis and help for the design and improvement of the support. Under the experimental conditions, the optimum combination is 0.5 mm in diameter, 50 mm in length, 3 rings in the extruded segment, and 12 mm. in the extruded section, according to the design concept. The optimum combination is 0.5 mm in diameter, 50 mm in length of extruding segment, 3 in the number of bracket rings on the extruded segment, and 12 mm. in expansion degree. Through testing the mechanical properties of the interlayer inner membrane, the corresponding mechanical performance parameters are obtained, which provides an important evaluation criterion for the reasonable selection of the support parameters: when the support performance is improved by changing the geometric parameters of the scaffold, The designed radial supporting force should not exceed the physiological endurance limit of the dissecting intima or the aortic vascular wall and prevent the serious postoperative complications caused by the mismatch of the mechanical properties of the stent. The simulation results of CFD fluid dynamics show that, When the distal break is not treated in time, the break near the end of the scaffold may become a new entrance, which will continue to provide perfusion for the lower segment of the false chamber. The extruded bracket can effectively block the reflux phenomenon of the break in the false cavity of the interlayer. The observational results of the external fluid model can well verify the validity of the CFD fluid simulation results.
【學(xué)位授予單位】：北京有色金屬研究總院
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：R318.08
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