远端滤网保护装置的生物力学分析

Biomechanics Analysis for Distal Embolic Protection Devices

目的:模拟了一款镍钛合金远端滤网保护装置在扩张定型、径向压握和自膨胀释放过程中的情况,并对模型结构在各个接触载荷下的力学性能进行分析。方法:建立远端滤网保护装置、压握工具以及目标血管的有限元模型。对远端滤网保护装置一端沿Z轴负方向施加大小为-0.5 mm的位移载荷使其完成扩张,并对圆柱状定型模具沿R轴正方向施加大小为0.5 mm的位移载荷,使远端滤网保护装置最大外径定型为6.0 mm;对圆柱状压握工具施加向内的径向位移沿R轴正方向施加大小为2.0 mm的位移载荷,压握远端滤网保护装置至外径为2.0 mm;将压握工具恢复到原始尺寸,建立血管/远端保护器接触关系。分析远端滤网保护装置在扩张定型及压握状态下的最大主应变(MPS)峰值及分析后形态,释放状态下变形血管的等效应力峰值(VMS)。结果:结果表明,远端滤网保护装置最大扩张及最大定型主应变峰值分别为4.843%和2.955%;最大压握主应变峰值为7.22%;在自膨胀释放过程中,造成血管壁应力集中的峰值为0.447 MPa。结论:该远端滤网保护装置在各状态下应力应变皆在镍钛合金屈服极限之内,但其Z字状结构相联处应力应变集中。本研究结果可以用于远端滤网保护装置的结构优化设计,提高其生物力学性能,在工程和临床上具有重要应用价值。

Objective This paper is aimed at the process of a nickel titanium alloy distal embolic protection device in expansion,crimping and self-expanding, and analyzing the model＇s structure in each contacting mechanical loads. Methods First, buildingthe finite element model of the distal protection device, crimping tools and the target vessel. Rs expansion is completed byadding -0.5 ram displacement load along to Z axis to the distal embolic protection device. The protection device＇s maximumdiameter for 6.0 mm was applied 0.5 mm displacement load along to R axis and the diameter of protection device for 2.0 mmwas set by adding 2.0 mm displacement load along to R axis to cylindrical crimping tools. When the crimping tools backed toits original size, the contact between the vessel and distal protection device would be established. Then, the analysis of the max-imum principal strain （MPS） of protection device in expansion and crimping, and the maximum Von Mises stressCv＇MS） of ves-sel would be indicated when the protection device was full self-expanding. Results The maximum principal strain of distal pro-tection device in two process of expansion were respectively 4.843% and 2.955%, the maximum principal strain in crimpingprocess was 7.22% and in the self-expanding process, the Von Mises stress （VMS） of vessel was 0.447 MPa. Conclusion Thestress and strain of the distal embolic protection devices in every process are under the limitation of nickel titanium alloy, butthere is stress and strain concentration on the connections. The results of this study would be used for optimal structure design-ing for the distal embolic protection devices to improve its biomechanical properties in engineering and clinical science.