血管粘弹性对（扌衮）法推拿作用下血管切应力的影响

目的 研究血管粘弹性对脉动血流在（扌衮）法推拿作用下切应力的影响。方法 建立具有局部轴向运动狭窄的粘弹性血管中脉动血流模型。设血液为牛顿流体，血管壁为线性粘弹体。在（扌衮）法推拿作用下血管受水平外力作用形成轴向运动缓变狭窄，血流遵循线化Navier-stokes方程。结果 粘弹性血管在（扌衮）法作用下，距离血管入口z=31cm处的平均切应力、最大切应力和瞬时切应力以及最大狭窄下游血管段最大切应力随着血管粘性系数和手法频率的改变而有较大变化。结论 （扌衮）法推拿作用下粘弹性血管的血管切应力有显著变化，这与中医推拿的活血化淤相吻合。     

血管粘弹性对法推拿作用下血管切应力的影响

目的研究血管粘弹性对脉动血流在(扌衮)法推拿作用下切应力的影响.方法建立具有局部轴向运动狭窄的粘弹性血管中脉动血流模型.设血液为牛顿流体,血管壁为线性粘弹体.在(扌衮)法推拿作用下血管受水平外力作用形成轴向运动缓变狭窄,血流遵循线化Navier-stokes方程.结果粘弹性血管在(扌衮)法作用下,距离血管入口z=31 cm处的平均切应力、最大切应力和瞬时切应力以及最大狭窄下游血管段最大切应力随着血管粘性系数和手法频率的改变而有较大变化.结论(扌衮)法推拿作用下粘弹性血管的血管切应力有显著变化,这与中医推拿的活血化淤相吻合.     

中医推拿(扌衮)法手部受力的生物力学建模及分析

目的 建立中医(扌衮)法的简化生物力学模型,对(扌衮)法过程中手部主要部位的受力进行定量分析.方法 应用摄像机和推拿手法测定仪实测推拿专家(扌衮)法推拿的运动学和力信号,建立含手部及桡骨、尺骨的简化的生物力学模型和方程,求解手部桡骨和尺骨远端点处的受力.结果 (扌衮)法外推时,手部桡骨和尺骨远端点处X方向((扌衮)动方向)受力方向不变,出现两个峰值,近外推结束时受力最大;回收时两处受力大小和方向出现波动.手部桡骨和尺骨远端点处,Y方向和Z方向受力趋势相同,在逐步上升后出现了一个平缓变化的阶段,之后急骤下降.结论 建立的简化生物力学模型可对中医法推拿手部受力进行较好的定量分析.     

切应力作用下联合培养的血管平滑肌细胞对内皮细胞PDGF-B mRNA表达的影响

目的：探讨切应力作用下联合培养的血管平滑肌细胞（VSMCs）对内皮细胞（ECs)PDGF-BmRNA表达的影响，为预防血管移植物发生再狭窄提供实验资料。方法：用原位杂交和图像分析等技术，以静态条件下单独培养的ECs和联合培养的ECs为两对照组，观察切应力作用下单独培养的ECs和与VSMCs联合培养ECs的PDGF－BmRNA表达变化。结果：静态条件下联合培养ECs和PDGF－BmRNA表达水平比单独培养的ECs下降；切应力作用下，联合培养ECs的PDGF－BmRNA的表达在切应力作用1h左右有瞬时上升，6h后 下降至低于联合培养条件下的静态水平，且瞬时上升的时间点比单独培养的ECs提前。结论：切应力作用下，与VSMCs联合培养ECs的PDGF－BmRNA表达水平下降，这可能有利于抑制VSMCs的增生。     

切应力与血管平滑肌细胞对内皮细胞增殖的影响及TGFβ1与p-Akt信号通路在其中的作用

目的探讨切应力与血管平滑肌细胞(VSMCs)对内皮细胞(ECs)增殖功能的影响及其一些分子机制。方法应用平行平板流动腔系统对单独培养的ECs以及与VSMCs联合培养的ECs施加15dyn/cm2(1dyn=10-5N)的正常切应力;Western blot技术检测反映细胞增殖能力的分子—增殖细胞核抗原(PCNA)的表达及细胞内信号转导分子Akt的磷酸化水平。静态条件下,以单独培养ECs为对照组,将ECs与VSMCs隔开培养,并应用TGFβ1封闭性抗体,观察TGFβ1在VSMCs诱导ECs增殖中的作用。结果正常切应力抑制了ECs增殖及p-Akt表达,VSMCs在与ECs联合培养及隔开培养时均明显促进ECs增殖及p-Akt表达。正常切应力部分逆转了联合培养VSMCs诱导的ECs增殖和p-Akt表达,而TGFβ1封闭性抗体能够拮抗隔开培养VSMCs诱导的ECs增殖和p-Akt表达。结论正常切应力可视为血管的保护因子,抑制ECs增殖;VSMCs通过旁分泌作用诱导了ECs增殖;TGFβ1及PI3/Akt信号分子参与了其调节过程。     

切应力作用下肾近端小管上皮细胞纤溶酶原激活物(tPA和uPA)表达的变化及意义

检测切应力作用下肾近端小管上皮细胞纤溶酶原激活物tPA和uPA mRNA表达的变化,探讨糖尿病肾病早期小管间质细胞外基质重塑的可能机制.用5 dyn/cm2和10 dyn/cm2的切应力处理肾近端小管上皮细胞(NRK-52E),作用时间分别为1、3和6 h,用RT-PCR法检测tPA及uPA mRNA的表达.结果表明:切应力呈大小和时间依赖性下调肾小管上皮细胞tPA及uPA mRNA的表达.在糖尿病肾病早期,高滤过引起的切应力增加可抑制肾近端小管上皮细胞tPA和uPA mRNA表达,导致肾小管间质纤维蛋白溶解活性降低,参与小管间质细胞外基质的重塑.     

黏弹性血管脉动血流在法推拿作用下的切应力分析

建立具有局部轴向运动狭窄的黏弹性血管中脉动血流模型,模拟研究中医     

分岔动脉血管内灌注药液时的药物浓度分布

建立了分岔动脉血管二维几何模型和动脉血流平均流速脉动流模型.对分岔动脉血管脉动血流的动力学状况和匀速进行药液注射进行了数值模拟,获得用导管注射药液时的血液流场的变化情况和药液在血液流场内的周期分布.计算结果表明,所建立的几何模型和血液平均流速脉动流模型可以较好地分析解释了临床上所观察到的血流动力学现象和药液传输现象,能够反映出分岔动脉血管脉动流的传质特点.这不但为实施进一步数值模拟提供了可靠的前提,而且本文的计算结果对优化血管性介入治疗等也提供了血流动力学依据.     

出口边界条件和壁厚对冠状动脉壁面剪切力和冯米塞斯应力的影响

探讨基于个体化患者计算机断层血管造影(CTA)影像的冠状动脉流固耦合(FSI)数值分析中,不同出口边界条件和血管壁模型对时间平均壁面剪切力(TAWSS)和冯米塞斯应力(VMS)的影响。根据患者CTA影像重建右冠状动脉(RCA)管腔流域三维几何;将管腔流域表面向外扩张0.5 mm,形成均匀厚度血管壁;运用类似虚拟去除斑块的方法建立不均匀厚度血管壁模型。FSI分析时,分别给予zero和impedance两种出口边界条件;获得从舒张末期开始心动周期主要时间点TAWSS和VMS的分布,比较不同模型结果的差异。结果表明, 两种出口边界条件下,TAWSS空间分布基本一致,且血管狭窄段均高于其他部位;zero条件下峰值VMS出现在压强最大时刻点0.42 s,而impedance条件下峰值VMS出现在入口血流速度最大时刻点0.64 s,并且达到前者的20倍。同是impedance出口边界条件时,TAWSS分布基本一致,没有显著性差异;两种血管壁模型中,VMS的分布一致,血管狭窄段比其他部位低,但是不均匀厚度血管壁模型中局部位置VMS绝对值高于均匀壁厚血管壁模型。医学影像技术的发展可以提供更高精度的冠脉结构以及出入口速度和压强边界条件,不但对研究血流动力学以及结构力学因素与心血管疾病的关系具有重要意义,也可以更好的服务于患者个体化诊断与治疗。     

Spatial Distribution of Wall Shear Stress in Common Carotid Artery by Color Doppler Flow Imaging

The purpose of this study is to provide a novel approach for measuring the spatial distribution of wall shear stress (WSS) in common carotid artery in vivo. WSS distributions were determined by digital image processing from color Doppler flow imaging (CDFI) in 50 healthy volunteers. In order to evaluate the feasibility of the spatial distribution, the mean values of WSS distribution were compared to the results of conventional WSS calculating method (Hagen–Poiseuille formula). In our study, the mean value of WSS distribution from 50 healthy volunteers was (6.91?±?1.20) dyne/cm², while it was (7.13?±?1.24) dyne/cm² by Hagen–Poiseuille approach. The difference was not statistically significant (t?=??0.864, p?=?0.604). Hence, the feasibility of the spatial distribution of WSS was proved. Moreover, this novel approach could provide three-dimensional distribution of shear stress and fusion image of shear stress with ultrasonic image for each volunteer, which made WSS “visible”. In conclusion, the spatial distribution of WSS could be used for WSS calculation in vivo. Moreover, it could provide more detailed values of WSS distribution than those of Hagen–Poiseuille formula.     

Wall Shear Stress and Pressure Distribution on Aneurysms and Infundibulae in the Posterior Communicating Artery Bifurcation

A growing number of cases of rupture at an infundibulum, progression of infundibulum to a frank aneurysm, and subarachnoid hemorrhage (SAH) in the posterior communicating artery (PCoA) have been reported. Using patient-specific geometric models of the supraclinoid internal carotid artery (ICA) with PCoA infundibulum or aneurysm, high-resolution computational fluid dynamics simulations were performed by solving the Navier–Stokes equations with a spectral/hp element method. Simulation results show that the flow impinges at the distal wall of infundibulum near the outside of the ICA bend and creates a region of higher pressure (4–5 mmHg) surrounded by a band of a high wall shear stress (WSS) (20–30 N/m² on average). At the proximal end of the infundibulum, another stagnation area is formed characterized by low WSS (<1 N/m²) and high oscillating shear index. This impingement region seems to coincide with the locations of the rupture of infundibulae or progression to aneurysms. In addition, the pulsatile flow becomes unstable due to the presence of aneurysms or aneurysm-like infundibulae, and this leads to WSS temporal fluctuations inside the aneurysm, which may accelerate the degenerative processes in the vessel walls.     

血管壁面剪切应力的测量及其临床研究进展

总结血管壁面剪切应力(WSS)的几种测量技术和计算方法,主要包括基于磁共振或磁共振结合计算流体动力学(CFD)、计算机断层扫描(CT)、血管内超声、传统超声、超声向量血流成像和超声粒子流的血流速度测量技术,以及根据速度计算WSS的几种不同运算方法。介绍WSS计算时的另一个重要参数--血液黏滞系数(又称“血黏度”),描述该参数在精确测量WSS时的选取和计算。此外,通过现有文献论述三维向量WSS的测量以及WSS相关临床参数的计算方法,对现有的WSS临床研究做综述性的讨论。针对颈动脉、主动脉、冠状动脉、肱动脉、股动脉等不同血管,列举WSS相关的临床研究结果,并从中归纳出绝大多数临床研究认可的3个主要结论。     

一种可控性大鼠颈总动脉狭窄模型的建立及切应力测定

目的：为在体研究切应力改变诱导内皮细胞组织因了的表达建立一种可控性的大鼠颈总动脉狭窄模型。方法：54只SD大鼠随机分为9组，用自制硅胶管套扎左颈总动脉中段，术后不同时相点用TS 420型多普勒血流仪测定血流量，灌注前用DIGITEXα数字血管减影操作系统测定血管内径，用Poiseiuue流体力学公式Tw=32ηQ／πD^3计算切应力。结果：颈总动脉狭窄85％后，平均血流量减少了65％，局部切应力发生了显著变化（P〈0．01），在7d内无明显改变。结论：硅胶管套扎大鼠颈总动脉中段的狭窄模型，是比较理想的在体检测血流壁切应力改变对血管内皮细胞形态和功能影响的方法。     

狭窄动脉血管中管壁切应力的数值研究

对血液脉动流动时血管狭窄部位的管壁切应力分布进行研究.文中利用不可压缩的N-S方程作为计算的理论基础,采用有限差分方案作为计算手段以得到在此流动过程中的数值解.     

Regional Blood Flow in the Left Ventricular Wall of Dogs with a Graded Coronary Artery Stenosis

Blood flow in the circumflex branch of the left coronary artery was recorded by electromagnetic flowmeter. In the area supplied by this branch vasodilatation was produced by progressive constriction until the diastolic reactive hyperemic response to 10 s occlusion disappeared (“optimum” stenosis). This degree of stenosis was accompanied by a 20% decrease in diastolic circumflex flow, while systolic flow remained unchanged. The distribution of blood flow in the left ventricular free wall was evaluated at “optimum” stenosis by counting activity in tissue blocks following bolus injection of Xe-133 into the aortic root. When Xe-133 was injected immediately after occlusion of the left anterior descending branch the Xe-133 concentration of the endocardial part of the area supplied by the circumflex branch was about half the concentration in the epicardial part. The concentrations in the two parts did not, however, differ significantly when occlusion of the left anterior descending branch was omitted. This indicates that the endocardial blood flow reserve is lower than the epicardial, and that, yet, a preferential fall in blood flow in the endocardial part of a post-stenotic area can be rapidly eliminated when blood supply from a neighbouring artery is available.