基于4D-PC-MRI的主动脉夹层TEVAR术后血流-支架-主动脉间耦合作用的仿真研究

Based upon a series of studies, our research team put stent-graft-induced mechanical injury forward as a hypothesis underlying the stent-graft-induced new entry (SINE) which was considered the first important fatal complication after the thoracic endovascular aortic repair (TEVAR) for Stranford type B aortic dissection（TBAD）. After a previous study supporting the hypothesis, we are applying for this project (1) to acquire the patients’ imaging data of aorta with 4D-PC-MRI before and after TEVAR, and the perform the processing; (2) to conduct a numerical simulation on the interaction among flow, stent-graft and aorta, and fulfil the verification in a physical manner in order to determine the method; (3) to include 200 patients with TBAD and group them, complete the simulation and clinical follow-up. The anticipated outcomes would contribute to (1) obtaining the technical method for the data acquisition by 4D-PC-MRI and their post processing; (2) revealing the hemodynamic features of TBAD before and after TEVAR; (3) quantitative analysis on the interaction among flow, stent-graft and aorta. The current project would: (1) provide an quantitative evidence to reveal the mechanism of SINE and set up a prophylaxis for it, so as to reduce the post-TEVAR mortality; (2) promote a wide use of 4D-PC-MRI for the pre-TEVAR evaluation and post-TEVAR follow-up, and offer a more accurate imaging method for TBAD and TEVAR.

课题组发现主动脉夹层（AD）腔内修复（TEVAR）后首位致死性并发症支架源性新破口（SINE），提出“支架源性力学损伤”是主因的假说。前期研究获初步论证。本申请拟：（1）4D-PC-MRI采集TEVAR前后AD数据并后处理，感应导丝体内测量以验证并优化前者技术参数；（2）仿真分析血流－支架－主动脉间相互作用，并物理验证，固定技术参数；（3）选择200例AD-TEVAR患者，根据SINE危险因素分组，仿真分析，组间比较，并与临床随访结果比对。旨在：（1）建立针对AD的4D-PC-MRI采集及后处理方法；（2）获得TEVAR前后AD血流动力学特征及变化规律；（3）定量分析搏动血流下支架－主动脉间相互作用。从而：（1）为阐明SINE发生机制、制定防治措施提供量化依据，降低TEVAR死亡率；（2）推广4D-PC- MRI在AD-TEVAR术前评估与术后随访中的应用，为临床提供更为准确的检测手段。

申请人前期研究发现了主动脉夹层胸主动脉腔内修复（TEVAR）术后严重并发症-支架源性新破口（SINE），并提出了"支架源性力学损伤"的机制假说，但缺乏定量实验证据，难以为阐明机制和制定防治措施提供确切证据。计算机模拟为研究SINE的发生提供了新的思路，但是以往的研究均采用了理想化模型，并非基于患者影像学的个体化模型。SINE的发生涉及到血流、支架和主动脉三个主要因素。为了进一步提高数值仿真的准确性，学者们通过力学实验和体外主动脉标本的测算，得到了相对准确的支架和主动脉参数，但是血流的参数仍旧是影响数值仿真准确性的主要因素之一，亟待解决。本研究（1）通过4D-PC-MRI对主动脉夹层患者全流场数据的采集，并在此基础上计算出主动脉各部位的压力值，为后续的数值模拟奠定了基础。（2）利用术中对TEVAR前后主动脉夹层真假腔压力测量和基于4D-PC-MRI计算的主动脉各部位压力进行对比，矫正、优化其技术参数，初步建立了4D-PC-MRI对主动脉夹层血流采集的技术路线，证实了4D-PC-MRI计算个体化主动脉血流参数的准确性。（3）利用计算机模拟将4D-PC-MRI图像与主动脉CTA segmentation模型进行耦合，然后将耦合满意的.stl文件导入到自编程的Matlab程序中，同时导入升主动脉导管测压曲线作为原点，根据4D-PC-MRI获取的流场信息来计算各部位压力梯度，从而获取各部位的压力值，并通过Ensight软件的可视化功能将数据可视化，用于后续数值模拟的入口条件。（4）初步完成了基于4D-PC-MRI推算主动脉入口流速的流-固-固耦合仿真模拟。为今后全个体化的数值仿真奠定了基础。