人体主动脉弓内三维血流动力学数值分析

目的阐明基于核磁共振数据进行数值建模的关键技术,利用计算流体动力学方法对人体主动脉弓内的血液流场进行了三维数值模拟。方法通过对临床核磁共振成像进行图像处理完成主动脉弓及分支血管的三维数字化重构,结合相关脉动血流量,模拟主动脉弓在心动周期不同时刻的血液流动细节。结果计算得到了人体主动脉弓内的血液流动在心动周期不同时刻的速度场、压力、壁面剪切应力的分布特征。结论基于核磁共振数据进行数值建模的关键技术有利于生物流体力学研究的深入开展,对主动脉弓进行血液流场的数值模拟有利于临床动脉粥样硬化、主动脉夹层的诊断和治疗。     

双向双侧格林手术的数值研究

目的利用数值模拟方法预测左上腔静脉与肺动脉的连接位置改变对双向双侧格林(BBDG)手术的影响。方法首先,根据拥有左上腔静脉的单心室心脏缺陷综合征病人的医学图像重建出三维几何模型。其次,基于力反馈器创建其他数值模拟所需的模型,并利用有限体积法进行流体力学的数值模拟。最后,分析与评估获得的血流动力学参数。结果血液在左、右上腔静脉与肺主动脉中进行再循环。左上腔静脉到右上腔静脉之间的距离由右上腔静脉直径的2倍逐渐变化到右上腔静脉直径的3.5倍,发现当距离为3倍直径时,能量损失最少,而距离为2倍时,能量损失最大。血液分流比(左肺动脉流量/右肺动脉流量)的计算结果范围为0.65～1.11。结论在BBDG手术的治疗中,左、右上腔静脉之间距离太近会导致不适宜的分流比以及消耗更多的能量。本研究结果对于评价伴随有左上腔静脉的单心室心脏缺陷综合征的治疗手术是非常有意义的。     

腹主动脉瘤几何形态对血液动力学影响的三维数值分析

目的研究腹主动脉瘤不同形态学对瘤内血液动力学的影响,为临床预估动脉瘤的破裂提供参考。方法根据动脉瘤影像学上的特点建立不同几何形态的数学模型,采用计算流体动力学(CFD)方法,在周期性脉动速度入流、刚性壁面以及血液为牛顿流体的条件下,对一个心动周期内瘤内流场进行数值分析研究,比较不同几何形态腹主动脉瘤内血液动力学。结果非轴对称模型可造成相对较大的壁面剪应力;带有峰值偏移和曲率半径偏转的腹主动脉瘤,瘤内漩涡的发展变化会随着几何形态的不同而产生变化。结论腹主动脉瘤内流场特征的变化受到不同形态学的影响。     

实体肿瘤血液动力学的三维数值模拟

目的　数值研究实体肿瘤内外三维微血管网及间质内的血液动力学。方法　数值生成实体肿瘤内外三维微血管网，根据Poiseuille定律和Darcy定律分别计算微血管内压强及肿瘤组织间质压、组织液流速。结果　肿瘤外部微血管内压强迅速降低，肿瘤内部微血管压强变化很小，可视为常数；肿瘤组织间质压呈现‘内高且平，外低且陡’的分布，组织液流速与之相反。结论　本模型得到了较为有效的肿瘤内外三维血管网结构；血液动力学计算结果与生理实际基本吻合，为研究肿瘤内药物输运提供了可信的模型及方法。     

改良B-T手术不同搭桥方式的血流动力学比较

目的 通过数值模拟的方法对比分析端对边（end-to-side, ETS）与边对边（side-to-side, STS）两种不同搭桥方式的改良B-T手术（modified blalock-taussig shunt, MBTS）对血流动力学的影响,为临床治疗单心室心脏缺陷综合征提供参考。方法 采集单心室心脏缺陷综合征病人的医学图像,重建病人心脏真实的几何模型;基于虚拟手术操作系统模拟手术过程;采集病人的生理数据,建立病人的集中参数模型（lumped parameter model, LPM）;通过LPM计算提供计算流体力学（computational fluid dynamics, CFD）仿真模型的近生理边界条件;利用有限体积法对模型进行数值仿真。结果 分别获取了ETS模型和STS模型的血液流速以及壁面切应力分布。ETS模型和STS模型的吻合口部位振荡剪切系数（oscillatory shear index, OSI）分别为3.058×10-3和13.624×10-3,能量损失分别为116.5 和94.8 mW,右、左肺动脉流量比RRPA/LPA分别为0.8和1.72。结论 两个模型的能量损失相差不大,对手术的影响相对较小。STS搭桥方式左右肺动脉流量分布均匀,吻合口位置OSI值较小,优于ETS搭桥方式,应着重考虑。本研究为临床治疗单心室心脏缺陷综合征提供重要的理论支持和参考。     

颅内动脉瘤夹闭手术的血流动力学数值分析

本文利用计算流体力学(CFD)方法对颅内动脉瘤夹闭手术前后血液流场进行三维数值模拟,根据血流动力学对手术方案的可行性进行预估。采用逆向工程软件Mimics对临床CT图像进行三维数字化重构,结合相关脉动血流量,模拟心动周期不同时刻的血流动力学细节。通过计算得到了模型手术前后在心动周期不同时刻的速度场、壁面剪切应力场、压力场的分布特征,对比分析手术前后分叉处的血流速度、壁面剪切应力、壁面压力变化,结果显示术后的血流速度与壁面剪切力显著提高,而壁面压强则明显降低。     

TCD对颈椎病血液动力学的探讨

目的:探讨经颅多普勒超声(TCD)对颈椎病诊断的临床意义。方法:对100例眩晕患者进行经颅多普勒超声检测,并进行结果分析。结果:在双侧椎动脉血流速不同程度减慢的患者中有88·4%患者有颈椎病的X线表现。结论:椎动脉血液动力学的改变与颈椎病有一定的联系。     

手术前后三维动脉瘤模型的血液动力学模拟对比

本研究目的 在于从临床患者的医学影像出发,在手术前后分别对三维动脉瘤模型进行了定常模拟,观察动脉瘤模型内的流场形态以及各血液动力学参数的变化并进行讨论.由于三维的数值模拟比二维的跟接近实际,而且更加直观形象,所以研究结果对于分析动脉瘤的破裂机理具有重要的临床应用价值.     

MRI纹理分析联合机器学习模型对前列腺腺泡癌Gleason分级的预测价值

目的 探讨利用前列腺腺泡癌MRI纹理分析对前列腺腺泡癌Gleason评分(GS)高危组(GS≥4+3分)与低危组(GS≤3+4分)进行预测的价值。方法 选择前列腺根治全切术后病理诊断为前列腺腺泡癌的148例患者,年龄43～90岁,平均年龄61.18岁;其中高危(GS≥4+3分)80例,低危(GS≤3+4分)68例;血清前列腺特异抗原(PSA)为0.70～161.92 ng/mL, PSA中位数7.16 ng/mL;前列腺体积(PV)为13.42～174.81 cm3,平均PV 45.32 cm³;前列腺病灶体积为0.26～122.70 cm3,病灶体积中位数2.71 cm3;病灶位置外周带(PZ)69例,交界地带13例,移行带(TZ)66例。患者均行高分辨率横轴面T2加权成像(T₂WI)和横轴扩散加权成像(DWI)扫描(b值=1 500 s/mm²)。利用ITKSNAP软件勾画三维(3D)病灶,从MRI图像中提取T₂WI和表观扩散系数(ADC)图像的影像组学纹理特征,依次采用Mann-Whitney...     

5种支架对颈内动脉瘤血液动力学影响的数值研究

目的 研究不同结构形状以及不同网丝截面的支架用于颈内动脉瘤治疗后对血液动力学及支架柔顺性的影响。方法 针对同一个体模型的颈内动脉瘤,构建5种不同支架介入治疗的模型。这些支架的支撑体网丝截面不同,但支架通透率近似相等。利用有限体积法进行数值仿真,获得其生物力学特性的定量信息。结果 5种模型中,矩形截面网格支架模型动脉瘤腔中平均流动速度的减小幅度最大;圆型截面支架和矩形截面螺旋支架模型中瘤面和瘤颈部分的壁面切应力减小面积较大;网格支架的柔顺性要远好于螺旋支架。结论 矩形截面网格支架对治疗颈内动脉瘤有较好的生物力学影响,这些发现可帮助临床医生在治疗脑动脉瘤时选择合适的支架。     

Numerical Experiment for Ultrasonic-Measurement-Integrated Simulation of Three-Dimensional Unsteady Blood Flow

Integration of ultrasonic measurement and numerical simulation is a possible way to break through limitations of existing methods for obtaining complete information on hemodynamics. We herein propose Ultrasonic-Measurement-Integrated (UMI) simulation, in which feedback signals based on the optimal estimation of errors in the velocity vector determined by measured and computed Doppler velocities at feedback points are added to the governing equations. With an eye towards practical implementation of UMI simulation with real measurement data, its efficiency for three-dimensional unsteady blood flow analysis and a method for treating low time resolution of ultrasonic measurement were investigated by a numerical experiment dealing with complicated blood flow in an aneurysm. Even when simplified boundary conditions were applied, the UMI simulation reduced the errors of velocity and pressure to 31% and 53% in the feedback domain which covered the aneurysm, respectively. Local maximum wall shear stress was estimated, showing both the proper position and the value with 1% deviance. A properly designed intermittent feedback applied only at the time when measurement data were obtained had the same computational accuracy as feedback applied at every computational time step. Hence, this feedback method is a possible solution to overcome the insufficient time resolution of ultrasonic measurement.     

缝合式和机械吻合式搭桥模型的血流动力学数值模拟

为了说明机械吻合器的引入对冠状动脉搭桥术近端吻合区血流动力学因素的影响,运用Solidworks软件构造了缝合式和机械吻合式两种搭桥模型。运用有限单元数值模拟的方法和Fluent6.3软件,对两种模型移植血管中脉动流进行数值化模拟和可视化分析。获得了吻合区在一个心动周期内不同时刻的速度场、二次流、压力及壁面切应力的分布情况。结果表明,机械吻合器的引入在增大移植血管中血流速度（大于缝合模型约0.2 m/s）的同时使得低速区范围增大,吻合区壁面切应力变化范围为0～50 Pa,应力集中现象明显,壁面切应力变化剧烈,易引起血小板活化和内膜增生。为了提高冠状动脉搭桥术的通畅率,对机械吻合器进行优化设计很有必要。     

Vortex Phenomena in Sidewall Aneurysm Hemodynamics: Experiment and Numerical Simulation

We carry out high-resolution laboratory experiments and numerical simulations to investigate the dynamics of unsteady vortex formation across the neck of an anatomic in vitro model of an intracranial aneurysm. A transparent acrylic replica of the aneurysm is manufactured and attached to a pulse duplicator system in the laboratory. Time-resolved three-dimensional three-component velocity measurements are obtained inside the aneurysm sac under physiologic pulsatile conditions. High-resolution numerical simulations are also carried out under conditions replicating as closely as possible those of the laboratory experiment. Comparison of the measured and computed flow fields shows very good agreement in terms of instantaneous velocity fields and three-dimensional coherent structures. Both experiments and numerical simulations show that a well-defined vortical structure is formed near the proximal neck at early systole. This vortical structure is advected by the flow across the aneurysm neck and impinges on the distal wall. The results underscore the complexity of aneurysm hemodynamics and point to the need for integrating high-resolution, time-resolved three-dimensional experimental and computational techniques. The current work emphasizes the importance of vortex formation phenomena at aneurysmal necks and reinforces the findings of previous computational work and recent clinical studies pointing to links between flow pulsatility and aneurysm growth and rupture.     

3种可转换型腔静脉滤器血流动力学数值模拟

目的研究不同血栓直径和血栓含量下可转换型腔静脉滤器用于治疗肺动脉栓塞后对血流动力学的影响。方法构建3种直径相同、过滤结构(L、S和W型)不同的滤器仿真模型,利用计算流体力学方法对植入血管以后的滤器进行血流动力学分析。结果在无血栓条件下,3种滤器均对血流有一定的阻碍作用,并使出口处的平均流速增大。其中,L型滤器引起的出口平均流速最大,S型次之,W型最小。在有血栓条件下,滤器过滤杆的结构形状对出口平均血流流速、血栓流速、血流出入口压差、血栓出入口压差影响不明显;而随着血栓直径的增大和血栓含量的增加,血流动力学因素呈现不同程度下降趋势。血流对3种滤器过滤杆上产生的壁面剪应力均在正常范围之内,而滤器支撑体下游端和支撑体与过滤杆连接处产生的壁面剪切应力都小于最小极限值,该处容易引起血栓形成。结论利用计算流体力学方法分析3种可转换型滤器在不同过滤杆结构以及不同血栓直径、血栓含量下对血流动力学的影响,为新型滤器的设计研发提供理论参考。     

Numerical Experiment of Transient and Steady Characteristics of Ultrasonic-Measurement-Integrated Simulation in Three-Dimensional Blood Flow Analysis

In ultrasonic-measurement-integrated (UMI) simulation of blood flows, feedback signals proportional to the difference of velocity vector optimally estimated from Doppler velocities are applied in the feedback domain to reproduce the flow field. In this paper, we investigated the transient and steady characteristics of UMI simulation by numerical experiment. A steady standard numerical solution of a three-dimensional blood flow in an aneurysmal aorta was first defined with realistic boundary conditions. The UMI simulation was performed assuming that the realistic velocity profiles in the upstream and downstream boundaries were unknown but that the Doppler velocities of the standard solution were available in the aneurysmal domain or the feedback domain by virtual color Doppler imaging. The application of feedback in UMI simulation resulted in a computational result approach to the standard solution. As feedback gain increased, the error decreased faster and the steady error became smaller, implying the traceability to the standard solution improves. The positioning of ultrasound probes influenced the result. The height less than or equal to the aneurysm seemed better choice for UMI simulation using one probe. Increasing the velocity information by using multiple probes enhanced the UMI simulation by achieving ten times faster convergence and more reduction of error.     

Hemodynamics Simulation of Stenosed Coronary Bypass Graft

By means of FEM, the physiological blood flow in coronary bypass graft is simulated. The stenosis in coronary artery is involved in the graft model,and the deformation of graft end to allow the surgical suture with a smaller diameter coronary is taken into consideration. The flow pattern, secondary flow and wall shear stress in the vicinity of anastomosis are analyzed. It is shown that a zone of low wall stress and high wall stress gradient exists downstream the toe. The floor opposed to the anastomosis is an area of high wall stress and high wall stress gradient. Both the toe downstream and the anastomosis bottom floor are prone to intimal hyperplasia.     

Three-Dimensional Hemodynamics in the Human Pulmonary Arteries Under Resting and Exercise Conditions

The biomechanical forces associated with blood flow have been shown to play a role in pulmonary vascular cell health and disease. Therefore, the quantification of human pulmonary artery hemodynamic conditions under resting and exercise states can be useful in investigating the physiology of disease development and treatment outcomes. In this study, a combined magnetic resonance imaging and computational fluid dynamics approach was used to quantify pulsatile flow fields, wall shear stress (WSS), oscillations in WSS (OSI), and energy efficiency in six subject-specific models of the human pulmonary vasculature with high spatial and temporal resolution. Averaging over all subjects, WSS was found to increase from 19.8 ± 4.0 to 51.8 ± 6.7 dynes/cm², and OSI was found to decrease from 0.094 ± 0.016 to 0.081 ± 0.015 in the proximal pulmonary arteries between rest and exercise conditions (p < 0.05). These findings demonstrate the localized, biomechanical effects of exercise. Furthermore, an average decrease of 10% in energy efficiency was noted between rest and exercise. These data indicate the amount of energy dissipation that typically occurs with exercise and may be useful in future surgical planning applications.     

体外模拟心血管系统血液动力学性能分析

为研究人工心脏和心血管系统之间的血液动力学作用机制．根据弹性腔模型建立了一套能反映血液动力学特性的体外血液循环模拟实验装置，测试血液动力学参量与心室后负荷（即外周力R和动脉顺应性C）以及每搏心输出量Vs，心动周期T和心室收缩时间间隔Ts，前负荷等六个参量之间的相互关系．通过改变六个参量中的某一个参量而固定其余参量，测试这个参量对动脉血压及流量的影响情况。实验结果与生理情况和数学模型分析相符合。压力和流量波呈脉动性，与真实生理波形相似。整个模拟装置能够反映血液动力学特性。