基于血管内超声(IVUS)的人体冠状动脉随心动周期形变的流固耦合数值模拟与分析

IVUS-BASED COMPUTATIONAL MODELS FOR FLUID-STRUCTURE INTERACTION AND STRESS/STRAIN ANALYSIS OF HUMAN CORONARY WITH CYCLIC BENDING

人体动脉血管内粥样斑的受损和破裂与血管内的受力等力学情况密切相关.基于各种医学成像数据建立的血管数值模拟模型能很好的考察血管内的受力及血流情况,已成为对血管内粥样斑的受损和破裂作出评估和预测的有力工具.本文利用一位患者的血管内超声(IVUS)图像数据建立了其冠状动脉血管的三维流固耦合数值模拟模型,并根据患者CT造影的动态影像数据模拟了冠状动脉在人体内随心脏搏动而产生的周期性运动过程.模型中冠状动脉血管采用各向异性Mooney-Rivlin材料模型,其材料参数是由冠状动脉血管样本的双轴加载拉伸实验获得的拉伸比率———应力数据拟合得到的,血压数据也采用了患者自身的数据,因而本文建立的数值模型真实模拟了人体内冠状动脉的实际运动情况.本文给出了血管内的应力应变分布、血流速度、血液最大剪切应力等数值模拟结果,并比较了血管的周期弯曲和血压变化的相位差的影响.结果表明:血管内部的脂肪斑对血管的应力应变分布有显著的影响;就该患者个体而言,血管弯曲程度对血管内部的应力应变分布的影响要强于血压的影响.而相比于血管的弯曲程度,血管内的血流速度和流通量受血压的影响较为显著.本文建立的模拟冠状动脉周期运动的数值方法可以进一步地应用于大量冠状动脉粥样硬化患者的病例研究.随着患者数量的积累,通过分析可以更精确地评估和预测粥样斑的受损性和破裂发生可能性.

It is commonly believed that the rupture of atherosclerotic plaque may be closely linked to critical stress/strain conditions.To assess and predict plaque rupture,image-based computational models combining mechanical analysis with image technology have been developed to identify critical flow and stress/strain conditions.Two models of three-dimensional fluid structure interactions（FSI） were proposed based on intravascular ultrasound（IVUS） imaging.Periodic bending of coronary artery due to movements of the heart was simulated after X-ray coronary angiography.Modified anisotropic model of Mooney-Rivlin（M-R） was applied to the coronary.Parameters of the model were determined by least-squares fitting of biaxial experimental stress-stretch data obtained from a human coronary specimen.Patient-specific pressure data were acquired using IVUS Combowire and used to obtain more realistic boundary conditions.Stress/strain of coronary,flow velocity and flow maximum principal shear stress were investigated.Impact of phase angle of cyclic bending and pressure was compared.The plaque was found to have significant influence on the distribution of stress/strain.The effect of bending on stress/strain in coronary was more significant than pressure.Fluid velocity and flow rate had closer relationship with blood pressure than bending had.Simulation of periodic motion of the coronary could be applied to coronary vulnerable plaques,this will be of great interest to clinic practice and public health.The long term goal will be to make plaque vulnerability assessment and prediction more accurate.