粒子图像测速技术及其在人体上呼吸道气流流场研究中的应用

分析了流场测量常用方法,介绍了粒子图像测速(PIV)技术与测试系统,综述了国内外利用PIV技术对人体上呼吸道内部气流运动测量的研究进展和已取得的研究成果,展望了PIV技术在研究人体上呼吸道气流特性方面的应用前景.     

基于粒子图像测速技术的血泵内流场研究

自制外触发同步系统,应用二维粒子图像测速技术技术(PIV)实现了流线型叶轮血泵和直叶片叶轮血泵的内流场的测量,并分析叶轮设计和运行条件对血泵内流场和血液相容性的影响.实验结果表明:基于外触发同步的PIV系统实现了对血泵同一流道的流速信息的连续采样;血泵内的绝对速度和相对速度分布随着叶轮设计、流量和进出口压差而改变.在设计工况(4 L/min,100 mmHg)下,流线型叶轮血泵流道内的流动模式较为规则,而直叶片血泵的流动模式则出现了明显的旋涡、回流和流动分离等现象.根据血液动力学理论,在设计工况下,流线型叶轮血泵具有较好的血液相容性.     

房水流动粒子图像测速测试中跟随性示踪粒子选择的实验研究

目的 在房水流动粒子图像测速(particle image velocimetry,PIV)测试中,选择最佳跟随性示踪粒子是展示真实流场的必要前提.本文探讨眼球房水慢流PIV测试中不同粒子的跟随性并选择最佳显影效果的示踪粒子.方法 依据几何相似性原理,设计并加工5倍于真实人眼大小的眼球模型;分别选择10μm空心玻璃珠,以及1μm、3μm、7μm和20～50μm粒径荧光粒子作为示踪粒子,运用PIV系统在眼球模型上进行流场测试,比较粒子的空间分布规律探讨粒子跟随性问题,确定可用于房水流场测试的最佳示踪粒子.结果 荧光粒子的粒径越大,沉淀的速度越快,则沉淀量越多.1μm的荧光粒子跟随性好,但显影效果不佳.3μm荧光粒子随着测量时间的增加,沉淀最不明显,跟随性和显影效果最佳.结论 示踪粒子直径对其在眼球房水流动中的跟随性和显影效果具有显著影响.基于当前的PIV设备,3μm荧光粒子是房水流场测试最佳的示踪粒子.本研究可为采用PIV技术进行体外房水流场测量提供一定的实验基础.     

左心室辅助装置与主动脉吻合角度对主动脉瓣膜影响的血流动力学研究

目的 探究左心室辅助装置(left ventricular assist device, LVAD)与主动脉吻合角度对主动脉瓣膜的血流动力学影响。方法 分别构建LVAD与主动脉吻合角度为45°、60°、90°的3个主动脉模型和主动脉瓣膜模型,搭建体外搏动台用于体外实验。运用粒子图像测速(particle image velocimetry, PIV)系统,选取心动周期中的3个时刻(T₁收缩峰值期,T₂瓣膜快速闭合时期和T₃舒张峰值期)探究主动脉瓣膜处血流动力学状态。结果 采用速度矢量、涡量、黏性剪切力指标评价LVAD吻合角度对主动脉瓣膜血流动力学的影响。瓣膜快速闭合时期,吻合角度增大时,瓣膜近壁面血流速度、平均涡量和最大黏性剪切力均增大。结论 吻合角度较低时,血流对主动脉瓣膜的冲击速度较小,瓣膜受到较小的剪切力,使瓣膜处于较好的血流动力学环境。研究结果为临床手术中吻合角度的选择提供参考。     

纳米粒子载体在防治血管损伤后再狭窄中的应用

血管损伤后再狭窄是影响经皮血管成型术和动脉旁路手术预后的主要原因。由于血液的流动和冲刷，使血管病变局部用药很难长期、持续发挥作用。纳米技术和纳米粒子载体的出现为这一临床问题的解决带来了希望：其亚微米的结构特性使之能顺利的通过组织间隙，分布于血管壁，同时极易被细胞吸收，使血管病变局部达到有效的治疗浓度；治疗剂经纳米粒子载体包载后，具有缓释效应，这有效的延长了治疗剂在血管病变局部的作用时间。     

图像分析技术在乳腺癌病理学研究中的应用

近30年来随着成像技术、数字计算机以及信息处理技术的迅速发展,兴起了一门交叉科学—图像分析技术,它的出现标志着形态定量研究进入了定量分析的新阶段。由于其克服了早年方格测试模板,称重法等计数测读的繁琐,因而倍受国内外学者关注,已广泛应用于胃癌、大肠癌、鼻咽癌、肝癌、乳腺癌及癌前病变的研究,为肿瘤的诊断、鉴别诊     

流场测试技术及其在血泵流场测试中的应用

心脏辅助血泵应用后出现的大多数并发症都与血液的流体动力学特征以及血泵制作的材料有关.因此,分析和认识辅助血泵内部流场对于血泵的设计和改进有着重要意义.     

基于CT血管成像的斑块定量分析在冠状动脉血流动力学异常诊断中的应用价值

目的:探讨基于冠状动脉CT血管成像(CCTA)分析斑块定量指标在冠状动脉血流动力学异常诊断中的应用价值。方法:回顾性病例对照研究。纳入2020年7—10月天津医科大学总医院行CCTA检查的冠状动脉单支或多支局限性狭窄患者104例(共检出病变血管200支)的临床及影像学资料,其中男63例、女41例,年龄45~83岁。依据...     

基于小波变换的血管内超声图像血流斑点噪声抑制研究

血管内超声成像已经越来越广泛地应用到冠心病的诊断和介入治疗中.为了提高图像分辨率必须增加超声频率,使得血流斑点噪声也显著增强,降低了管腔和管壁的对比度,增加了识别管壁与周围组织的难度,给病情的诊断和治疗带来了不便.本研究结合小波变换域软阈值滤波法和半软阈值滤波法,并设计了一种局部阈值来实现血流斑点噪声抑制.实验结果表明该方法在抑制斑点噪声的同时保留了图像的边缘,增强了管腔和管壁的哪对比度,有助于识别管壁和周围组织.     

四维血流磁共振成像在门静脉系统中的应用现状

磁共振成像在门静脉系统中的应用越来越受到重视,而四维血流磁共振成像作为一种新型磁共振技术,可以动态显示血管内血流动力学的变化。目前,该技术已广泛应用于全身各个血管系统检查中,其可以从形态学和血流动力学两方面对血流进行定性和定量分析,对疾病的诊断及其严重程度的判断具有重要意义。本文就四维血流磁共振成像在门静脉系统中的临床应用现状进行简要综述。     

搭桥冠脉内超声多普勒血流信号的仿真分析

为研究搭桥冠脉内血流状况与移植管结构因素的关系,采用基于计算流体动力学模型的信号仿真方法合成不同缝合角度、不同缝合距离的搭桥冠脉内的超声多普勒血流信号,并分析其频谱随两个结构因素变化的规律.结果 表明:缝合角度越小,缝合前端及下游仿真信号的频谱宽度越小,说明搭桥手术的效果越好;缝合位置距离狭窄越近,缝合后端附近血流信号的频谱宽度越大,缝合前端及下游的频谱宽度则越小,说明手术应折中选取缝合位置.结论 与血液动力学研究结果一致,可以为手术方案的设计和术后效果的监测提供参考.     

Patient-Specific Modeling of Blood Flow and Pressure in Human Coronary Arteries

Coronary flow is different from the flow in other parts of the arterial system because it is influenced by the contraction and relaxation of the heart. To model coronary flow realistically, the compressive force of the heart acting on the coronary vessels needs to be included. In this study, we developed a method that predicts coronary flow and pressure of three-dimensional epicardial coronary arteries by considering models of the heart and arterial system and the interactions between the two models. For each coronary outlet, a lumped parameter coronary vascular bed model was assigned to represent the impedance of the downstream coronary vascular networks absent in the computational domain. The intramyocardial pressure was represented with either the left or right ventricular pressure depending on the location of the coronary arteries. The left and right ventricular pressure were solved from the lumped parameter heart models coupled to a closed loop system comprising a three-dimensional model of the aorta, three-element Windkessel models of the rest of the systemic circulation and the pulmonary circulation, and lumped parameter models for the left and right sides of the heart. The computed coronary flow and pressure and the aortic flow and pressure waveforms were realistic as compared to literature data.     

Effects of Dynamic Wall Properties on Blood Flow in Stenotic Arteries

Highgradestenosesmaycausecriticalflowandmechanicalconditionssuchasnegativepressure,flowsepanion,highshearstressandwallcompressioninarterieswhichmayberelatedtoplateletaggregation,thrombusformation,atherosclerosisgrowthandplaquecaPruPturewhichleadsdirectlytostrokeandheartattack.Theexatmechanismoftheseeventsandtheconditionscausingthemarenotwellunderstood.Bloodflowishighlypulsatile'Thedynamicmechanicalpropertiesofstenoticalleriesareverycomplex-NumericalsimulationoftheflowbehaviorandwalIdeformati…     

Blood Flow in a Compliant Vessel by the Immersed Boundary Method

In this paper we develop a computational approach to analyze hemodynamics in the aorta; this may serve as a useful tool in the development of noninvasive methods to detect early onset of diseases such as aneurysms and stenosis in major blood vessels. We introduce a mathematical model which describes the interaction of blood flow with the aortic wall; this model is based on the immersed boundary method. A two-dimensional vessel model is constructed, the velocity at the inlet is prescribed based on the information from the Magnetic Resonance Imaging data measured in the aorta of a healthy subject, and the velocity at the outlet is prescribed by driving the pressure level reproduced from the literature. The mathematical model is validated by comparing with well-known solutions of the viscous incompressible Navier–Stokes equations, i.e., Womersley flow. The hysteresis behavior in the pressure–diameter relation is observed when the viscoelastic material property of the arterial wall is taken into consideration. Five different shapes of aortic wall are considered for comparison of the flow patterns inside the aorta: one for the normal aorta, two for the dilated aorta, and two for the constrictive aorta.     

弹性动脉狭窄血管内血液流动的ALE方法分析

针对弹性动脉狭窄血管中血液的流动状况,采用任意拉格朗日-欧拉方法(ALE),在给定相同的边界条件下模拟出了弹性血管和刚性血管中血流速度和压力的变化情况,分析了不同狭窄程度模型的血流状态.结果表明:随着动脉的狭窄程度增加,其中心流速越来越大,窄前压力逐渐升高,窄后压力逐渐降低,狭窄前后的压差单调增加;刚性血管无法对人体正常生理状态进行比较好的模拟,其计算所得结论与实际情况差距较大.说明ALE方法对血液流动的数值研究是可行的.     

Numerical Simulation and Experimental Validation of Blood Flow in Arteries with Structured-Tree Outflow Conditions

Blood flow in the large systemic arteries is modeled using one-dimensional equations derived from the axisymmetric Navier–Stokes equations for flow in compliant and tapering vessels. The arterial tree is truncated after the first few generations of large arteries with the remaining small arteries and arterioles providing outflow boundary conditions for the large arteries. By modeling the small arteries and arterioles as a structured tree, a semi-analytical approach based on a linearized version of the governing equations can be used to derive an expression for the root impedance of the structured tree in the frequency domain. In the time domain, this provides the proper outflow boundary condition. The structured tree is a binary asymmetric tree in which the radii of the daughter vessels are scaled linearly with the radius of the parent vessel. Blood flow and pressure in the large vessels are computed as functions of time and axial distance within each of the arteries. Comparison between the simulations and magnetic resonance measurements in the ascending aorta and nine peripheral locations in one individual shows excellent agreement between the two. © 2000 Biomedical Engineering Society. PAC00: 8719Uv     

脑中风患者彩色多普勒超声特征研究

目的用彩色多普勒超声观察中老年人脑中风患者颅内及颈动脉形态、结构和血流动力学改变. 方法应用2.5MHz探头和10MHz线阵探头分别观察155例不同类型脑中风患者和80例正常人颈动脉内中膜厚度、斑块情况及颅内与颈动脉血流动力学改变情况. 结果 (1)各型脑中风组颈总动脉(CCA)内中膜厚度均较对照组明显增厚,斑块有109例出现(70.3%),而对照组仅4例(5.0%)出现斑块;(2)各型脑中风组颈内动脉时间平均流速(TAVICA)较正常组减低、阻力指数(RI)、搏动指数(PI)较正常组明显升高;(3)脑梗死组大脑中动脉时间平均流速(TAVMCA)较正常组低,脑出血组TAVMCA较正常组明显升高,混合性中风组可出现TAVMCA升高或降低两种情况. 结论中老年人各型脑中风患者颈动脉粥样硬化程度加重,斑块出现率高及斑块所引起的颈动脉狭窄,对脑中风有直接的因果关系,联合检查颅内动脉和颈动脉血流动力学改变可协助诊断不同类型脑中风,对其疗效观察,预防复发有一定的指导作用.     

脑中风患者彩色多普勒超声特征研究

目的 用彩色多普勒超声观察中老年人脑中风患者颅内及颈动脉形态、结构和血流动力学改变。方法 应用2．5MHz线阵探头分别观察155例不同类型脑中风患者和80例正常人颈动脉内中膜厚度、斑块情况及颅内与颈动脉血流动力学改变情况。结果 （1）各型脑中风组颈总动脉（CCA）内中膜厚度均较对照组明显增厚,斑块有109例出现（70．3％）,而对照组仅4例（5．0％）出现斑块;（2）各型脑中风组颈内动脉时间平均流速（TAVICA）较正常组减低、阻力指数（RI）、搏动指数（PI）较正常组明显升高;（3）脑梗死组大脑中动脉时间平均流速（TAVMCA）较正常组低,脑出血组TAVMCA较正常组明显升高,混合性中风组可出现TAVMCA升高或降低两种情况。结论 中老年人各型脑中风患者颈动脉粥样硬化程度加重,斑块出现率高及斑块所引起的颈动脉狭窄,对脑中风有直接的因果关系,联合检查颅内动脉和颈动脉血流动力学改变可协助诊断不同类型脑中风,对其疗效观察,预防复发有一定的指导作用。