颅内动脉瘤的三维数值模拟分析

目的应用计算流体力学软件结合有限元法对颅内动脉瘤进行三维数值模拟,分析动脉瘤的血液动力学特性。方法利用临床三维血管造影图像建立动脉瘤数值模型,用Matlab7.0软件及Ansys软件提取动脉瘤的立体轮廓并进行三维网格划分,然后应用Fluent6.02软件进行动脉瘤数值模拟及血流动力学分析。结果本例研究对象显示动脉瘤流入道的血流速度、动压及壁面切应力最高,流出道次之,顶部最低。结论①根据病人的解剖结构所构建的动脉瘤模型的三维数值模拟,把压力入口及脉搏波动应用其中,对血流动力学数据分析更先进、更接近临床实际。②动脉瘤顶部的血流流速、瘤内压力、壁面切应力均最低,这种特殊的结构导致了动脉瘤顶部可能成为动脉瘤破裂的部位。③动脉瘤三维数值模拟能够很好地反应动脉瘤的血液动力学特性,是一种极好的动脉瘤实验及临床研究方法。     

动脉瘤的血流动力学数值模拟初步分析

目的数值模拟分析动脉瘤的血流压力、速度和切应力3个指标特点,探讨动脉瘤生长、破裂的可能机制。方法采用动脉瘤的医学影像结合计算流体力学(CFD)软件,对动脉瘤内血液流动进行数值模拟。结果 (1)流场压力呈周期性变化,压力剧烈变化的时间窗为0～0．62T,与速度剧烈变化时间窗一致,动脉瘤内各处压力周期变化与流场的周期变化一致,每一个具体的时刻流场压力分布不均衡;(2)脉动状态下,每个心动周期里,在0 ～0．4T内,速度变化最剧烈,在动脉分叉处形成涡运动,通过瘤颈进入动脉瘤内时,血流速度骤减,在动脉瘤中央形成涡,速度逐渐减小并可能静止,瘤顶血流速度很小甚至静止;(3)动脉瘤内,整个心动周期里切应力几乎都在迅速的变化,与血流速度的急剧变化的时间一致,切应力存在于瘤颈,瘤壁为零。结论 3个指标(压力、速度、切应力) 是导致瘤颈内皮损伤、瘤生长、扩大的重要危险因子。数值模拟能较好反映动脉瘤血液流动过程,能够帮助认识动脉瘤的病理生理机制和指导临床治疗。     

不同类型脑动脉瘤内流体力学的三维数值模拟研究

目的探讨不同类型脑动脉瘤内流体力学的特征,为其治疗提供依据。方法建立宽颈与窄颈两种弯曲管侧壁型动脉瘤血液动力学三维数值模型,采用Fluent软件进行分析。结果宽颈动脉瘤内流速在任一时间点内均高于窄颈动脉瘤。瘤颈部的壁面切应力高于其他部位。瘤内压力场与瘤颈处载瘤动脉内压力值一致。结论宽颈动脉瘤较窄颈动脉瘤内血流动力学更加复杂,数值模拟研究有助于制订个体化治疗方案。     

顶端动脉瘤的血流动力学数值模拟压力分析

目的探讨顶端动脉瘤的血流动力学特点,分析动脉瘤的生长、破裂的可能机制。方法采用计算瘤体力学(CFD)软件结合顶端动脉瘤的医学影像,对动脉瘤内血液流动行数值模拟。结果流场压力呈周期性变化,压力剧烈变化的时间窗为0～0.62T (T为周期),与速度剧烈变化时间窗一致;动脉瘤内各处压力周期变化与流场的周期变化一致;每一个具体的时刻,流场压力分布不均衡。结论压力是动脉瘤破裂的危险因子之一,压力急剧变化的时间窗是0～0.62T,与流场速度急剧变化窗一致,是动脉瘤破裂的的危险窗。每一个时刻动脉瘤流场内压力分布不均衡。CFD数值模拟是一种反映动脉瘤血流动力学较好的方法,能为动脉瘤的病理生理机制和临床治疗提供较好的帮助。     

支架置入对颅内动脉分叉部动脉瘤血流动力学的影响

目的 探讨支架置入对颅内动脉分叉部动脉瘤血流动力学的影响.方法 设计颅内分叉部动脉瘤的聚酯玻璃及计算机三维数值模型,通过体外循环技术和计算流体力学技术两种方法来比较支架置入前后动脉瘤的血流动力学变化.结果 体外循环模拟实验的结果 与计算流体力学数值模拟的结果 具有较好的一致性.支架置入弱化了瘤颈处的涡流运动并减轻了血液对瘤体侧壁的冲击.支架置入后,动脉瘤瘤颈处平均剪切力降低22.3%,瘤顶处平均剪切力增高44.9%,但瘤顶处剪切力仍低于瘤颈处.结论 支架置入带来的动脉瘤瘤内血流动力学参数的改变,可能有利于瘤内的血栓形成和减少治疗后的复发.     

三维数值模拟颅内分叉部动脉瘤及血流动力学分析****☆

背景：已知血流动力学因素在动脉瘤的发生、发展和破裂中起重要作用。 目的：以三维计算机数值模拟观察颅内分叉部动脉瘤的血流动力学特性。 设计、时间及地点：三维数值模拟试验，于2008-07在北京神经外科研究所血管内治疗实验室进行。 对象：选择2008-04/07首都医科大学附属北京天坛医院神经介入科住院患者2例。病例1，女，37岁，血管造影示左侧前交通动脉瘤（共面的分叉部动脉瘤），右侧大脑前动脉A1段不显影。病例2，女，61岁，血管造影示基底动脉顶端动脉瘤（不共面的分叉部动脉瘤）。 方法：利用临床三维血管造影图像建立动脉瘤数值模型，并在GE公司的专用工作站进行三维重建。调整重建后的血管图像，并对其进行重新切片。然后运行Matlab 7.0软件及自写程序，逐渐生成动脉瘤的STL文件。导入网格生成软件，生成动脉瘤的三维网格。定义边界条件及提取血压波后，应用Fluent软件进行动脉瘤数值模拟。 主要观察指标：动脉瘤流入道、流出道、瘤顶部的血流速度、动压及壁面切应力。 结果：两个分叉部动脉瘤流入道的血流速度、动压及壁面切应力均最高，瘤顶部最低，与流出道相比较差异有显著性意义 （P < 0.05）；但共面的分叉部动脉瘤瘤顶部的动压较高，平均动压为(62.385 3±35.076 5) Pa；不共面的分叉部动脉瘤瘤顶部壁面切应力较低，平均壁面切应力为(0.220 7±0.071 6) Pa。 结论：瘤内动压在共面的分叉部动脉瘤破裂因素中起主要作用，而壁面切应力不足是不共面分叉部动脉瘤破裂的主要原因。     

颅内典型囊性动脉瘤的三维数值模拟及血流动力学分析

目的应用计算流体力学软件进行三维数值模拟,分析不同类型动脉瘤的血液动力学特性。方法根据动脉瘤瘤体与载瘤动脉的关系,将颅内典型囊性动脉瘤分为A（动脉瘤位于血管弓背侧）、B（动脉瘤位于血管弓内侧）、C（分叉部动脉瘤,瘤轴平面与载瘤动脉轴共面）,D（分叉部动脉瘤,瘤轴平面与载瘤动脉轴不共面）四类。联合应用Matlab软件、Ansys软件、Fluent软件及自写程序对颅内囊性动脉瘤进行计算机数值模拟分析。结果颅内动脉瘤模型流入道的血流速度、动压及壁面切应力最高,流出道次之．顶部最低;A、B、D类动脉瘤冲击域壁面切应力最大;C类动脉瘤内动脉压普遍较高。结论对A、B、D类动脉瘤,冲击域壁面切应力最大可能是动脉瘤生长的主要因素,而其顶部壁面切应力不足可能是破裂的主要因素之一;对C类动脉瘤,动脉瘤内动压较高是其破裂的主要因素。     

颅内动脉瘤Enterprise支架辅助弹簧圈栓塞术后的血流动力学变化:基于计算流体力学分析

目的 探讨颅内动脉瘤Enterprise支架辅助弹簧圈栓塞后瘤腔和载瘤动脉的血流动力学改变.方法 回顾性分析2021年3～8月Enterprise支架辅助弹簧圈栓塞治疗的24例颅内动脉瘤的临床资料.收集术前、术后即刻动脉瘤瘤腔和载瘤动脉处DSA数据的DICOM格式,导入OpenFOAM软件,应用计算流体力学数值模拟技术...     

兔特异性动脉瘤数值模型的建立及血流动力学分析

目的建立兔特异性动脉瘤数值模型并分析其血流动力学特征。方法采用外科手术结合弹性蛋白酶诱导法建立兔特异性动脉瘤数值模型,计算动脉瘤体颈比(AR),采用ANSYS CFX软件对动脉瘤的血流动力学特征如壁面切应力、流场、冲击域、压力场等进行数值模拟计算,并统计分析。结果动脉瘤AR值最大为1.79,最小为0.49。壁面切应力在动脉瘤流入道最高(28.39 Pa),瘤顶次之(11.39 Pa),流出道最低(6.64 Pa)。动脉瘤流入道和流出道壁面切应力梯度变化与AR值均无相关性(r=-0.016,P=0.957;r=0.185,P=0.527)。流场复杂性与AR值显著相关(r=0.627,P=0.016),而动脉瘤颈口的冲击域宽度与AR值相关性不显著(r=0.38,P=0.18)。动脉瘤顶压力最高(3 046.72Pa),动脉瘤流入道和流出道压力梯度变化与AR值均无相关性(r=0.202,P=0.489;r=-0.147,P=0.616)。结论兔特异性动脉瘤数值模型的血流动力学特征与病人特异性动脉瘤的血流动力学特征基本吻合,是研究动脉瘤的理想模型。     

半圆形截面血管内支架结构流阻的数值模拟实验

通过SoildWorks软件构建血液流场和8种不同结构裸支架(支架形状和通透率不同)的三维实体模型。利用计算流体力学方法,借助于有限元软件ANSYS 11.0对不同结构内支架分别置入血管后进行仿真研究。一定通透率范围内,对于半圆形截面支架模型血液从半圆面流向平面时的流阻大于反向流过时的流阻;通透率大到一定值时,结果相反。无论是网格状支架模型还是正弦状支架模型,血液从支架正反两个方向流过时的流阻大小随通透率的增加而减小;相同通透率下,血液从相同方向流过支架时,网格状支架模型的流阻比正弦状支架模型的大一些,大概在1.5倍左右。结果提示,血液从不同方向流过半圆形支架丝时的流阻存在一定的差异,这为支架结构设计提供了重要的理论指导意义。     

Three-dimensional pulsatile flow simulation before and after endovascular coil embolization of a terminal cerebral aneurysm.

The effect of different percentages of coil mesh in a cerebral aneurysm on the pulsatile flow and pressure in the parent vessel and aneurysm lumen was evaluated. Geometric data on a basilar tip aneurysm and vertebrobasilar arteries after subarachnoid hemorrhage was obtained by computer tomographic angiography. Intraarterial pressure was measured at four vertebrobasilar points before and after treatment with detachable coils. Pulsatile flow was documented by transcranial ultrasonography. A three-dimensional computer simulation was created using a commercial fluid dynamics solver for four aneurysm conditions: (1) before intervention; (2) with a 20% filling showing a complete cessation of the inflow through the aneurysm neck; (3) with a 12% filling showing an incomplete deceleration of inflow through the aneurysm neck, with a remaining flow around the embedded platinum coils; and (4) with a 12% filling and simulation of clotted aneurysm dome, which did not inhibit persisting flow phenomena. The relative pressure amplitudes neither increased nor decreased under the different simulated aneurysm filling conditions. Inserted platinum coils can immediately and decisively relieve the influx of pulsating blood and allow for initial clotting. To reach this effect, a volume density of 20% platinum coil mesh in the aneurysm neck is needed.     

血管内支架结构截面形状的生物力学实验

血管内支架置入体内后会影响血流动力学和血管壁剪切应力等生物力学耦合作用。分析支架杆件扩张受力弯曲的梯形截面比例系数,分别对二维支架梯形截面结构进行血管壁接触和血液流场流固耦合数值计算实验。结果显示,支架结构梯形截面比例系数为4时可减小支架对血管壁的接触应力,并改善支架表面的血流动力学状况。这可以避免支架置入后对血管壁形成的应力受损,显著减低支架表面血栓沉积的再狭窄率,对于血管内支架的设计具有重要的指导意义。     

LVIS支架释放前后颅内动脉瘤瘤腔内压力变化的研究

目的 探讨LVIS支架辅助栓塞颅内动脉瘤术中,支架释放前后动脉瘤瘤腔内压力的变化.方法 对40例颈内动脉海绵窦段至颈内动脉末端未破裂动脉瘤患者行LVIS支架辅助栓塞术,术中将Echelonl0微导管连接压力传感器送至动脉瘤腔内,测量支架释放前后动脉瘤腔内的压力值,并同时测量平均动脉压(MAP).比较支架释放前后动脉瘤腔...     

Understanding the effect of effective metal surface area of flow diverter stent’s on the patient-specific intracranial aneurysm numerical model using Lagrangian coherent structures

The effective metal surface area (EMSA) of flow diversions plays an essential role in the occlusion mechanism inside the aneurysm since the value of EMSA determines the amount of blood flow into the aneurysm sac. In the present study, three different models of a flow diverter stent, namely FRED 4017, FRED 4038, and FRED 4539, were virtually placed at the aneurysm neck of a 52-years-old female patient to identify the effect of EMSA on stagnation region formation inside the aneurysm sac. Lagrangian coherent structures (LCSs), hyperbolic time, and particle tracking analysis were employed to the velocity vectors obtained from computational fluid dynamics (CFD). It is noticed that use of FRED 4017 stent with 0.42 EMSA value caused nearly 40% of the weightless blood flow particles (more than FRED 4038 and FRED 4539) to stay inside the aneurysm while only 0.35% of the blood flow was remaining inside the aneurysm sac when no stent was placed into the aneurysm site. Furthermore, hyperbolic time computations illustrated the formation of stagnation fluid flow zones that can be associated with the residence time of the blood flow particles. Lastly, the results of hyperbolic time analysis are in good agreement with digital subtraction angiography (DSA) images taken in the clinic a few minutes after a FRED 4017 implantation.     

磁共振相位对比血管成像测量脑血流量的最佳速度编码

实验运用1.5-T磁共振的2D cine PC序列对10位健康志愿者C2水平感兴趣区血管进行速度编码为30~90cm/s,间隔10cm/s的7次同层扫描,探讨速度编码在磁共振相位对比血管成像中对测量脑血流量及入脑/出脑血流的影响。发现不同的速度编码对颈内动脉血流量、最大血流速度和平均血流速度影响较大,对椎动脉及颈内静脉影响不明显。当速度编码为60～80cm/s时,入脑血流量为(655±118)mL/min,出脑血流量(506±186)mL/min,入脑血流量/出脑血流量稳定在0.78～0.83,且所有血管中无混淆现象。提示在应用磁共振相位增强血管成像测量脑血流量时,应选择60～80cm/s的速度编码。     

Assessing the Hemodynamics in Residual Cavities of Intracranial Aneurysm after Coil Embolization with Combined Computational Flow Dynamics and Silent Magnetic Resonance Angiography

Background and PurposeMetal artifacts limit computational fluid dynamics analysis after coil embolization. Silent magnetic resonance angiography reduces metal artifacts and improves visualization of the residual cavity of coil-embolized aneurysms. This study investigated the flow dynamics of the residual cavity after coil embolization using silent magnetic resonance angiography and computational fluid dynamics to elucidate the hemodynamic characteristics of recanalization.MethodsTwenty internal carotid-posterior communicating aneurysm cases treated with coil embolization and without stent assistance were followed up (mean±standard deviation, 13.0±6.1 months) and assessed using silent magnetic resonance angiography. The hemodynamic characteristics of the residual cavities in both types of aneurysms were compared between neck remnants, which persisted for >12 months (NR group), and those treated with coil compaction-induced body filling (BF group). Computational fluid dynamics analysis of each aneurysm was performed using morphological data obtained from silent magnetic resonance angiography. Pressure, pressure difference, normalized wall shear stress, and flow velocity were measured.ResultsThe residual cavity was well-visualized using silent magnetic resonance angiography and compared with those imaged using conventional time-of-flight magnetic resonance angiography, and eight internal carotid-posterior communicating aneurysms with neck remnants and body filling were investigated. The maximum pressure area was localized to the aneurysm wall in the NR group (n=4) and to sides of the coil surface in the BF group (n=4). No significant differences were observed for each hemodynamic parameter.ConclusionsCombination of silent magnetic resonance angiography and computational fluid dynamics helps to understand the hemodynamic characteristics of residual cavity in coil- embolized aneurysms. The flow-impingement zone at the coil surface (maximum pressure area) may influence the risk for future coil compaction.     

Role of prostaglandins in blood-induced vasoconstriction of canine cerebral arteries

We tested the hypothesis that the vasoconstriction produced by the application of blood to the adventitial surfaces of the vessels of an isolated perfused canine circle of Willis preparation was mediated by products of prostaglandin metabolism. In this preparation (perfused at constant flow and outflow pressure), topical application of blood produced an average 16.6 +/- 1.8 (SE) mm Hg increase in inflow pressure. This response could be prevented with four structurally dissimilar cyclooxygenase inhibitors (aspirin, indomethacin, ibuprofen, and meclofenamate), suggesting that the blood-induced increase in vascular resistance was mediated by prostaglandins. Imidazole, an inhibitor of thromboxane synthetase, had no effect on the blood response. Further support for the involvement of prostaglandins in this response was provided by additional experiments in which either arachidonic acid, prostaglandin E2 (PGE2), or PGF2 alpha were administered. All three treatments produced vasoconstriction. These results suggest that the vessels of this preparation are capable of synthesizing vasoconstrictor prostaglandins and indicate that they are reactive to known vasoactive prostaglandins.