镜像破裂与未破裂后交通动脉瘤血流动力学的数值模拟分析

目的 探讨镜像破裂与未破裂动脉瘤的血流动力学特征差异.方法 1例镜像破裂与未破裂后交通动脉瘤的三维血管造影资料,采用数学建模的方法,利用流体力学软件分析两者的血流动力学参数及流场特征.结果 双侧动脉瘤的血流方式一致,但破裂动脉瘤射入流更宽且冲击域分布不一致;最大流速高于未破裂动脉瘤;破裂动脉瘤壁面切应力(wall shear stress,WSS)分布不均,低WSS区域较大.结论 血流动力学在镜像的破裂与未破裂动脉瘤中存在差异,高流速与低壁面切应力可能与动脉瘤破裂出血相关.     

Local hemodynamics at the rupture point of cerebral aneurysms determined by computational fluid dynamics analysis

Background: Cerebral aneurysms carry a high risk of rupture and so present a major threat to the patient's life. Accurate criteria for predicting aneurysm rupture are important for therapeutic decision-making, and some clinical and morphological factors may help to predict the risk for rupture of unruptured aneurysms, such as sex, size and location. Hemodynamic forces are considered to be key in the natural history of cerebral aneurysms, but the effect on aneurysm rupture is uncertain, and whether low or high wall shear stress (WSS) is the most critical in promoting rupture remains extremely controversial. This study investigated the local hemodynamic features at the aneurysm rupture point. Methods: Computational models of 6 ruptured middle cerebral artery aneurysms with intraoperative confirmation of rupture point were constructed from 3-dimensional rotational angiography images. Computational fluid dynamics (CFD) simulations were performed under pulsatile flows using patient-specific inlet flow conditions. Time-averaged WSS (TAWSS) and oscillatory shear index (OSI) were calculated, and compared at the rupture point and at the aneurysm wall without the rupture point. We performed an additional CFD simulation of a bleb-removed model for a peculiar case in which bleb formation could be confirmed by magnetic resonance angiography. Results: All rupture points were located at the body or dome of the aneurysm. The TAWSS at the rupture point was significantly lower than that at the aneurysm wall without the rupture point (1.10 vs. 4.96 Pa, p = 0.031). The OSI at the rupture point tended to be higher than at the aneurysm wall without the rupture point, although the difference was not significant (0.0148 vs. 0.0059, p = 0.156). In a bleb-removed simulation, the TAWSS at the bleb-removed area was 6.31 Pa, which was relatively higher than at the aneurysm wall (1.94 Pa). Conclusion: The hemodynamics of 6 ruptured cerebral aneurysms of the middle cerebral artery were examined using retrospective CFD analysis. We could confirm the rupture points in all cases. With those findings, local hemodynamics of ruptured aneurysms were quanti-tatively investigated. The rupture point is located in a low WSS region of the aneurysm wall. Bleb-removed simulation showed increased WSS of the bleb-removed area, associated with the flow impaction area. Although the number of subjects in this study was relatively small, our findings suggest that the location of the rupture point is related to a low WSS at the aneurysm wall. Further investigations will elucidate the detailed hemodynamic effects on aneurysm rupture.     

Association between hemodynamics,morphology, and rupture risk of intracranial aneurysms: a computational fluid modeling study

The objective of the study was to examine the correlations between intracranial aneurysm morphology and wall shear stress (WSS) to identify reliable predictors of rupture risk. Seventy-two intracranial aneurysms (41 ruptured and 31 unruptured) from 63 patients were studied retrospectively. All aneurysms were divided into two categories: narrow (aspect ratio ≥1.4) and wide-necked (aspect ratio <1.4 or neck width ≥4 mm). Computational fluid dynamics was used to determine the distribution of WSS, which was analyzed between different morphological groups and between ruptured and unruptured aneurysms. Sections of the walls of clipped aneurysms were stained with hematoxylin–eosin, observed under a microscope, and photographed. Ruptured aneurysms were statistically more likely to have a greater low WSS area ratio (LSAR) (P = 0.001) and higher aneurysms parent WSS ratio (P = 0.026) than unruptured aneurysms. Narrow-necked aneurysms were statistically more likely to have a larger LSAR (P < 0.001) and lower values of MWSS (P < 0.001), mean aneurysm-parent WSS ratio (P < 0.001), HWSS (P = 0.012), and the highest aneurysm-parent WSS ratio (P < 0.001) than wide-necked aneurysms. The aneurysm wall showed two different pathological changes associated with high or low WSS in wide-necked aneurysms. Aneurysm morphology could affect the distribution and magnitude of WSS on the basis of differences in blood flow. Both high and low WSS could contribute to focal wall damage and rupture through different mechanisms associated with each morphological type.     

破裂与未破裂镜像后交通动脉瘤形态与血流动力学分析

目的探讨破裂与未破裂颅内动脉瘤的血流动力学与形态学差异,分析动脉瘤破裂的危险因素。方法回顾性分析8例镜像后交通动脉瘤病人（均为一侧破裂,一侧未破裂）的临床资料,均行3D—DSA检查,建立数值模型。将16个动脉瘤按是否破裂分组,分析破裂组与未破裂组之间的形态学与血流动力学参数特征。结果破裂组动脉瘤平均擘面切应力（WSS）明显低于未破裂组（P〈0．05）;而低壁面切应力面积（LSA）比率和体颈比值明显高于未破裂组（P〈0．05）。剪切震荡指数（OSI）、动脉瘤直径、大小比率、血管角度和动脉瘤倾角组间差异无统计学意义（P〉0．05）。结论镜像后交通动脉瘤可能是研究动脉瘤破裂风险的理想模型,血流动力学与形态学在判断动脉瘤破裂风险方面同等重要。     

颅内破裂动脉瘤的血流动力学特征:基于流固耦合技术的计算流体力学模拟分析

目的 探讨颅内破裂动脉瘤破裂点和瘤囊处血流动力学特征。方法 选择2018年1月至2019年6月收治的颅内破裂动脉瘤21例，根据术前CTA、DSA数据三维重建动脉瘤模型，采用ANSYS软件计算动脉瘤破裂点和瘤囊处血流动力相关参数[壁剪切应力（WSS）、切应力震荡指数（OSI）]。结果 动脉瘤破裂点WSS[（0.215±0.047）Pa]明显低于瘤囊WSS[（0.464±0.148）Pa；P<0.001]。动脉瘤破裂点OSI[（0.035±0.024）]与瘤囊OSI[（0.030±0.016）]无统计学差异（P>0.05）。在一个心动周期中，随着血流动力学的变化，动脉瘤形态出现规律的变化，载瘤动脉及动脉瘤的形态变化存在明显差异，即动脉瘤两侧壁的形态变化相对较小，动脉瘤破裂点处形态变化明显。结论 颅内动脉瘤破裂点较动脉瘤囊WSS更低而形态变化更大，颅内动脉瘤破裂与WSS呈负相关，而与形态变化呈正相关。     

两种常见形态颅内动脉瘤的血流动力学研究

目的 对颅内动脉瘤进行三维数值模拟并分类.分析其血流动力学特性.方法 联合应用Matlab、Ansys、Fluent等软件及自写程序对39例颅内动脉瘤进行数值模拟.结果 两类动脉瘤模型流人道的血流速度、动压及壁面切应力最高,流出道次之,瘤顶部最低;且A类(长宽比>1.8)动脉瘤破裂率明显高于B类(长宽比≤1.8).A类动脉瘤流人道侧壁和瘤顶部壁而切应力比值(WSS'sratio)明显大于B类动脉瘤;且与其长宽比成正相关.结论 颅内动脉瘤顶部的血流速度、动压及壁面切应力均最低,是其破裂的主要原因和部位.流人道和瘤顶部壁面切应力比值及动脉瘤的长宽比反映动脉瘤的破裂风险,其比值越大,破裂风险越高.     

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。     

基于计算流体力学技术的个体化颅内动脉瘤三维刚性血流动力学模型

目的 建立基于计算流体力学技术（CFD）的个体化颅内动脉瘤血流动力学刚性模型.方法 用MIMICS软件读取病人颅内动脉瘤影像DICOM数据,进行三维实体重建.应用ANSYS-CFX软件进行三维刚性模型的数值仿真,分析与动脉瘤生长及破裂相关的血流动力学参数.结果 建立了个体化颅内动脉瘤血流动力学刚性模型,可以直观模拟动脉瘤血流动力学变化过程,形象地给出动脉瘤表面应力场的变化情况.在血流冲击瘤颈处,壁剪切力最大.结论 本研究建立的个体化颅内动脉瘤血流动力学模型快速、精确.动脉瘤的发生、发展和破裂与剪切力等血流动力学因素有关.动力学模型数值仿真结果可能为临床诊治提供理论分析基础.     

颅内镜面动脉瘤破裂的危险因素及预测研究

目的 探讨颅内镜面动脉瘤破裂的危险因素及预测指标。方法 回顾性纳入2016年1月-2021年12月于本院诊治颅内镜面动脉瘤患者共62例124个,根据动脉瘤是否破裂分为破裂组(60个)和未破裂组(64个);比较2组一般资料、电子计算机断层扫描(Computed tomography, CT)表现及血流动力学指标,采用Logistic回归模型分析颅内镜面动脉瘤破裂的独立危险因素,描绘受试者工作特征(Receiver operating characteristic, ROC)曲线评价上述独立危险因素的临床预测效能。结果 破裂组CT扫描动脉瘤最大径、颈宽、尺寸比、壁切应力变异系数、平均壁切应力均值变异系数、平均壁切应力绝对值变异系数、壁切应力梯度变异系数及平均壁切应力梯度变异系数均显著多于未破裂组(P<0.05);破裂组压力变异系数显著少于未破裂组(P<0.05);将单因素分析有统计学意义指标纳入Logistic回归模型行多因素分析显示,壁切应力变异系数和壁切应力梯度变异系数均是颅内镜面动脉瘤破裂的独立危险因素(P<0.05);ROC曲线分析显示,壁切应力变异系数联合壁切应...     

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。     

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.     

高分辨磁共振血管壁成像在评估颅内动脉瘤中的初步应用

目的探讨高分辨磁共振血管壁成像(high-resolusion magnetic resonance vessel wall imaging,HR-VWI)评估颅内动脉瘤的可行性。方法根据动脉瘤是否破裂,将接受HR-VWI检查的颅内动脉瘤分为破裂组(n=12)和未破裂组(n=88),对比两组动脉瘤的部位、大小、瘤颈宽度、高/颈比(aspect ratio,AR)、子囊和瘤壁强化等级。以动脉瘤是否破裂为因变量,以上各因素为自变量进行单因素和多因素Logistic回归分析。未破裂动脉瘤中,对症状性亚组(n=8)和无症状亚组(n=80)进行对比分析。结果破裂组的动脉瘤大小(t=2.187,P=0.031)、AR(t=3.164,P=0.002)、子囊比例(P=0.012)和瘤壁强化分级(P0.001)大于未破裂组。多因素Logistic回归提示瘤壁强化等级是破裂动脉瘤的独立危险因素(P=0.002)。未破裂动脉瘤中,症状性亚组瘤壁强化分级(P0.001)和AR(t=3.939,P0.001)大于无症状亚组。结论破裂动脉瘤中HR-VWI瘤壁强化分级高于未破裂动脉瘤,症状性未破裂动脉瘤存在瘤壁强化现象。有必要获得瘤壁的组织学标本,与HR-VWI结果对照分析,进一步研究瘤壁强化的机制和意义。     

基于影像数据的三维颅内动脉瘤血流动力学数值：手术前后壁面切模拟对比

背景：颅内动脉瘤是由于动脉血管壁病理性局限性扩张产生的脑血管瘤样突起。血流动力学因素被认为是颅内动脉瘤形成、生长、破裂过程中的一个重要因素，因此基于计算流体力学的计算机数值模拟技术得到了广泛的应用。 目的：通过对颅内动脉瘤术前术后进行血流动力学分析计算，探讨颅内动脉瘤术后壁面切应力的变化对动脉瘤是否复发的影响。 方法：对1例复发病例和1例未复发病例术前、术后的动脉瘤进行建模，实行血流动力学计算。 结果与结论：复发病例术后动脉瘤残颈处的切应力局部剧增；未复发病例术后动脉瘤残颈处切应力普遍减小。术后动脉瘤残颈处壁面切应力与术前相比，若普遍减小，能够降低动脉瘤复发的风险；反之，则增大了动脉瘤复发的风险，动脉瘤易复发。     

Metalloproteases and intracranial vascular lesions.

Recent studies have suggested that metalloproteinases (MMP) might be involved in the pathogenesis of cerebral aneurysm formation and rupture and that elevated serum levels of MMP may effectively be considered as possible markers of cerebrovascular malformations. The present study was planned in order to verify if serum levels of MMPs may be the mirror of the MMP activity in the wall of intracranial aneurysms, reflecting the predisposition to aneurysm development and/or rupture. A series of 84 patients operated for intracranial cerebrovascular lesions (63 aneurysms and 21 arterovenous malformations (AVM)) and 20 controls entered the study. Among the 63 cases of intracranial aneurysms, nine were discovered before rupture, while 54 patients were included after subarachnoid hemorrhage (SAH). Using radioimmunoassay, plasma elastase levels were measured in all cases, while in 25 cases, when aneurysmectomy was possible, the activity of elastase and collagenase were measured in aneurysm samples. Mean plasma elastase level in patients bearing both an intracranial aneurysm or an intracranial AVM was significantly higher than in controls, while there was no significant difference between plasmatic level of elastase in patients with aneurysms when compared with patients bearing an intracranial AVM; there was no significant difference between mean elastase level in patients who suffered SAH and patients bearing an intracranial unruptured aneurysm. The activity of elastase and collagenase measured in the aneurysm wall were significantly higher in cases of ruptured than in unruptured aneurysms. The present results show that plasmatic level of elastase does not reflect the activity of MMP as measured in the aneurysm wall and that the patterns of MMP activities measured in the aneurysm wall differ considerably at different stages of SAH. This suggests that local rather than systemic changes in metalloproteases activity might be involved in cerebral aneurysm formation and rupture.     

颅内囊性动脉瘤破裂形态学的危险因素分析

目的研究颅内囊性动脉瘤破裂的形态学危险因素。方法回顾性分析551例（共611个）颅内囊性动脉瘤的病例资料,以动脉瘤破裂作为最后评定指标,分为破裂组（341个动脉瘤）和未破裂组（270个动脉瘤）,使用SPSS17.0统计软件包分析数据。结果两组之间动脉瘤长、瘤颈宽、载瘤动脉平均直径、载瘤动脉近端与动脉瘤长轴夹角（IA）、瘤体长与瘤颈宽之比（AR）、瘤体最大径与载瘤动脉平均直径之比（SR）、动脉瘤面积与瘤颈处动脉面积之比（S1/S2）、存在子瘤有显著差异（P〈0.05）。多因素Logistic回归分析显示：瘤颈宽〈1.7 mm（OR=2.318,95%CI=1.381-3.893,P=0.001）、存在子瘤（OR=12.512,95%CI=7.827-20.002,P〈0.001）、S1/S2〉2.1（OR=2.460,95%CI=1.408-4.300,P=0.002）为颅内囊性动脉瘤破裂的独立危险因素。结论动脉瘤长、瘤颈宽、载瘤动脉平均直径、IA、AR、SR、S1/S2、存在子瘤是动脉瘤破裂的形态学危险因素。     

颅内动脉瘤影像学特征与动脉破裂的相关性研究

目的探讨颅内动脉瘤影像学特征与动脉破裂的关系。方法回顾性分析于我科行全脑血管造影的动脉瘤患者206例,分别研究患者的年龄、性别,动脉瘤的大小及分布位置与动脉瘤破裂的关系。结果206例患者共发生动脉瘤257个,其中破裂动脉瘤172个,未破裂动脉瘤85个;前循环217个,后循环40个。不同性别、年龄患者动脉瘤的破裂率比较,差异无统计学意义（P〉0．05）;不同动脉瘤位置的破裂率比较,差异有统计学意义（P〈0．05）;破裂动脉瘤的长度、高度、AR及SR均显著高于未破裂动脉瘤,差异有统计学意义（P〈0．05）。结论动脉瘤分布位置和动脉瘤大小与动脉瘤的破裂密切相关,前交通动脉瘤和后交通动脉瘤破裂率高,且大动脉瘤可能更容易破裂。     

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。     

Hemodynamic relationship between intracranial aneurysm and carotid stenosis: review of clinical cases and numerical analyses

Abstract

Objective: Coexistence of both an intracranial aneurysm and a stenosis at the same internal carotid artery is infrequent, but it may complicate therapeutic management of either disease. It is unclear if a stenosis plays any role in development of intracranial aneurysms. We study patients with intracranial aneurysms at our hospital and investigate if there is a relationship between a carotid stenosis and an intracranial aneurysm.

Methods: Two hundred and nine patients who were treated for their intracranial aneurysms in a 2-year period were reviewed. Fifty-four patients were found to have at least one intracranial aneurysm and one intracranial or extracranial carotid stenosis. Ten of them had bilateral stenoses; 17 aneurysms were on the ipsilateral side of the stenosis, and eight on the contralateral side. Nineteen aneurysms were elsewhere. Two cases were selected for detailed computational fluid dynamics (CFD) analyses: one with an intracranial and the other with an extracranial stenosis.

Results: Aneurysms on the contralateral side of a carotid stenosis are significantly larger than those aneurysms on the ipsilateral side or with bilateral stenoses (13.6 versus 6.6 mm; P < 0.01). CFD studies show that wall shear stress at the aneurysm is more likely affected by an adjacent intracranial stenosis than by an extracranial stenosis.

Conclusions: Intracranial carotid aneurysms contralateral to a carotid stenosis are significantly larger than aneurysms with a carotid stenosis elsewhere. Rupture can occur on aneurysms with an extracranial carotid stenosis on the contralateral side or with an intracranial carotid stenosis on the ipsilateral side.