Computational fluid dynamics of blood flow in coil-embolized aneurysms: effect of packing density on flow stagnation in an idealized geometry

Coil embolization is performed to induce flow stagnation in cerebral aneurysms and enhance blood clot formation, thus preventing rupture and further growth. We investigated hemodynamics in differently positioned aneurysms coiled at various packing densities to determine the effective packing density in terms of flow stagnation. As a first step, hemodynamic simulations were conducted for idealized geometries of both terminal- and sidewall-type aneurysms. Porous media modeling was employed to describe blood flow in coil-embolized aneurysms. The stagnant volume ratio (SVR) was analyzed to quantify the efficacy of coil embolization. Regardless of aneurysm type and angle, SVR increased with increasing packing density, but the increase in SVR varied depending on type. For sidewall-type aneurysms, the packing density required to achieve 60 % SVR was 20 %, roughly independent of aneurysm angle; flow stagnation was achieved at low packing density. In contrast, in terminal-type aneurysms, the packing density required to achieve 60 % SVR was highly dependent on aneurysm angle, accomplishing a 20 % packing density only for lower angles. Indications are that a relatively high packing density would be required, particularly when these aneurysms are angled against the parent artery. The packing density required for flow stagnation varies depending on aneurysm type and relative position.     

Computational study for the effects of coil configuration on blood flow characteristics in coil-embolized cerebral aneurysm

Coil embolization of cerebral aneurysms with inhomogeneous coil distribution leads to an incomplete occlusion of the aneurysm. However, the effects of this factor on the blood flow characteristics are still not fully understood. This study investigates the effects of coil configuration on the blood flow characteristics in a coil-embolized aneurysm using computational fluid dynamics (CFD) simulation. The blood flow analysis in the aneurysm with coil embolization was performed using a coil deployment (CD) model, in which the coil configuration was constructed using a physics-based simulation of the CD. In the CFD results, total flow momentum and kinetic energy in the aneurysm gradually decayed with increasing coil packing density (PD), regardless of the coil configuration attributed to deployment conditions. However, the total shear rate in the aneurysm was relatively high and the strength of the local shear flow varied based on the differences in coil configuration, even at adequate PDs used in clinical practice (20–25 %). Because the sufficient shear rate reduction is a well-known factor in the blood clot formation occluding the aneurysm inside, the present study gives useful insight into the effects of coil configuration on the treatment efficiency of coil embolization.     

CFD modeling of blood flow following coil embolization of aneurysms

In case of coil embolization of a giant or a multilobular aneurysm, it is difficult to fill an aneurysm sac completely with coils, therefore, partial blocking of an aneurysm sac is inevitable. Blood flow characteristics, which may influence embolization process of an aneurysm, are affected by the locations of coils for partially blocked aneurysms. Blood flow fields inside an aneurysm are also influenced by the geometry of a parent vessel. In order to suggest the coil locations effective for aneurysm embolization, the blood flow fields of lateral aneurysm models were analyzed for different coil locations and parent vessel geometries. Flow rate into an aneurysm sac from a parent vessel (inflow rate) and wall shear stress were also calculated. Inflow rates were smaller and low wall shear regions were larger in the distal neck blocked model comparing to the dome blocked models. In the distal neck blocked model, inflow volume was smaller by 31% (straight parent vessel model) and 34% (curved parent vessel model) comparing to other models. The time averaged values of normalized low wall shear regions were 4% and 12% greater in the distal neck blocked models with a straight and a curved parent vessel, respectively. Since smaller inflow and low wall shear stress provide hemodynamic environment promoting thrombus embolization, distal neck should be the effective coil location for aneurysm embolization.     

水解脱弹簧圈填塞治疗急性期破裂颅内动脉瘤1例

背景：以往多采用电解脱弹簧圈填塞治疗颅内动脉瘤,但电解脱弹簧圈解脱时间较长,解脱区质地硬,并发症发生率较高,不利于微小动脉瘤的栓塞。 目的：观察水解脱弹簧圈填塞治疗急性期破裂颅内动脉瘤的效果。 方法：经头颅CT检查确认蛛网膜下腔出血并有脑叶出血1例,数字减影血管造影系统证实为颅内动脉瘤,采用水解脱弹簧圈栓塞动脉瘤。 结果与结论：经过治疗,患者破裂动脉瘤致密栓塞,填塞达99%,出血得到控制。提示水解脱弹簧圈的超柔软性及对瘤体壁的顺应性,操作方便,提高了动脉瘤的致密性栓塞的可能性,减少并发症的可能,应该为目前急性期颅内动脉瘤破裂较好的栓塞方法。     

LEO+Baby单支架辅助弹簧圈栓塞前交通动脉瘤的有效性及安全性

目的评价专为小血管设计的低剖面、自膨式LEO+Baby单支架辅助弹簧圈栓塞前交通动脉瘤的有效性和安全性。方法回顾性分析应用LEO+Baby单支架辅助弹簧圈栓塞技术治疗的52例前交通动脉瘤患者的临床资料,统计患者基本信息、影像学资料、手术情况及并发症情况。结果52例前交通动脉瘤患者应用LEO+Baby支架51枚,1例患者支架导管到位困难,转开颅手术治疗,其余均操作成功,成功率为98%(51/52);术后即刻造影动脉瘤完全栓塞42例,瘤颈残留9例。术中动脉瘤破裂1例,支架内血栓形成3例,术中弹簧圈脱出1例。术后随访6~12个月,改良Rankin量表(mRS)评分为4~5分2例,2~3分5例,随访无死亡病例。46例患者术后6个月DSA复查结果显示完全栓塞率89.1%(41/46),其余5例未行DSA复查;无支架相关并发症及动脉瘤再破裂出血发生。头颅CT显示,无迟发性脑梗死、脑出血发生。结论应用LEO+Baby单支架辅助弹簧圈栓塞前交通动脉瘤操作成功率和安全性高、围术期并发症少且短期预后良好。     

颅内宽颈动脉瘤的血管内介入治疗

目的：总结血管内介入治疗颅内宽颈动脉瘤的技术及操作方法,并分析其临床疗效。方法：39例经头颅CTA和／或全脑血管造影确诊的颅内宽颈动脉瘤,其中未破裂动脉瘤9例;破裂动脉瘤30例,按Hunt—Hess分级标准,Ⅰ级8例、Ⅱ级17例、Ⅲ级4例、Ⅳ级1例。根据动脉瘤的具体位置、大小、形态及与载瘤动脉的关系分别采用3D弹簧圈网篮编织技术、血管内支架辅助弹簧圈栓塞技术、瘤颈重塑形技术、双导管技术,选用合适的弹簧圈逐步填塞治疗。结果：完全栓塞31例（79．4％）,大部栓塞8例（20．6％）。无术中出血病例。术中共置人164枚弹簧圈,15枚支架。术后第7天,1例患者因肾功能衰竭及严重的肺部感染死亡。38例患者出院后3个月依据GOS评分评价疗效,恢复良好（GOS5／4分）34例、轻度残疾（GOS3分）2例、重度残疾（GOS2分）2例。其中21例术后随访6～36个月,分别于术后6个月或16个月或36个月行全脑血管造影,未见动脉瘤复发。结论：绝大部分颅内宽颈动脉瘤通过选用合适的血管内辅助技术及方法能够得到成功的栓塞治疗。     

GDC栓塞术中颅内动脉瘤再破裂的原因、对策与结果

目的探讨电解脱弹簧圈(Guglialm i detachab le coil,GDC)颅内动脉瘤栓塞术中动脉瘤再破裂的发生率、原因、对策及结果。方法302例颅内动脉瘤破裂患者行GDC栓塞术,其中8例发生术中动脉瘤再破裂。结果2例由微导丝穿破动脉瘤壁引起,3例由微导管穿破动脉瘤壁引起,2例由置放首枚弹簧圈时顶破动脉瘤壁引起,l例术中自发破裂,所有病例均继续行GDC动脉瘤填塞。2例死于动脉瘤破裂后大出血,其他6例均康复没有留下后遗症。本组术中动脉瘤再破裂发生率为2.6%,死亡率为25%。结论GDC血管内栓塞术中引起动脉瘤再破裂是十分少见的,但大部分病例经过继续填塞GDC可达到完全填塞动脉瘤,且不留下后遗症。     

Blood flow dynamics in patient-specific cerebral aneurysm models: the relationship between wall shear stress and aneurysm area index

Hemodynamics plays an important role in the progression and rupture of cerebral aneurysms. The temporal and spatial variations in wall shear stress (WSS) within the aneurysmal sac are hypothesized to be correlated with the growth and rupture of the aneurysm. The current work describes the blood flow dynamics in 34 patient-specific models of saccular aneurysms located in the region of the anterior and posterior circulation of the circle of Willis. The models were obtained from three-dimensional rotational angiography image data and blood flow dynamics was studied under a physiologically representative waveform of inflow. The three-dimensional continuity and momentum equations for unsteady laminar flow were solved with commercial software using non-structured fine grid sizes. The vortex structure, the wall pressure, and the WSS showed large variations, depending on the morphology of the artery, size of the aneurysm, and form. A correlation existed between the mean WSS on the aneurysmal sac for lateral unruptured and ruptured aneurysms with an aneurysm surface index, which is defined as the ratio between the aneurysm area and the artery area at model inlet, respectively.     

电解可脱性弹簧圈栓塞治疗95例颅内动脉瘤

目的:探讨电解可脱性弹簧圈(GDC)血管内栓塞治疗颅内动脉瘤的效果.方法:回顾性分析2002年10月～2010年8月收治的95例颅内动脉瘤患者行电解可脱弹簧圈栓塞治疗的临床资料.本组患者均在全脑血管造影的同时或择日在静脉复合全身麻醉下经导引导管引入微导管和与之相匹配的微导丝.头端经过塑形的微导管在微导丝配合下置入瘤腔并固定于距瘤颈1/3处,选择大小适合的GDC进行栓塞治疗,依次将GDC填入瘤腔.结果:95例中,84例动脉瘤100%栓塞,8例95%栓塞,2例90%栓塞,1例基底动脉顶端动脉瘤患者微导管无法到位放弃治疗.94例术后随访3～12个月,均无再出血.3例术中出现并发症,其中2例后交通动脉瘤术中发生破裂出血,治疗后痊愈; 1例前交通动脉瘤治疗过程中见同侧大脑前动脉未显示,立即经引导管罂粟碱推注、40万尿激酶溶栓后再通,无并发症.结论:血管内栓塞治疗颅内动脉瘤是一种比较安全、可靠、有效的治疗手段.     

Willis环周围窄颈动脉瘤与栓塞材料选择的相关性*

背景：随着影像学设备与栓塞材料的不断发展,颅内动脉瘤的血管内栓塞治疗也成为治疗方法之一。 目的：探讨Willis环周围窄颈动脉瘤的形态学特点与栓塞材料选择及血管内栓塞治疗的关系。 方法：用双源CT血管成像检查筛选患者,采用Seldinger技术行全脑血管造影,根据动脉瘤的不同解剖学形态选用合适的弹簧圈进行介入栓塞治疗。 结果与结论：31例患者共36枚动脉瘤均成功栓塞,完全栓塞31枚、占86.11%,大部分栓塞5枚、占13.89%;随访6~12个月,所有患者均未发生再出血或脑血栓形成;动脉瘤的栓塞程度不仅与动脉瘤的形态有关,而且与栓塞材料直接相关。故认为根据不同的形态学特点选用合适的弹簧圈进行血管内栓塞治疗,是一种安全有效的方法。     

Lvis支架辅助弹簧圈血管内栓塞治疗颅内破裂动脉瘤的临床效果和安全性

目的:探讨Lvis支架辅助弹簧圈血管内栓塞治疗颅内破裂动脉瘤中的临床效果和安全性。方法:选取84例颅内破裂动脉瘤患者作为观察对象,随机分为A、B两组,每组42例患者。A组采用Lvis支架辅助弹簧圈血管内栓塞方式进行治疗,B组采用Solitaire支架辅助弹簧圈血管内栓塞方式进行治疗。采用RS评分、Raymond评分和GOS评分对临床效果进行评价,并对治疗后的不良反应发生率及复发率进行分析。结果:RS评分方面,A组为（0.23±0.57）分,B组为（2.48±0.96）分,A组低于B组（P<0.05）;Raymond评分方面,A组Ⅰ级发生率为92.24%,B组为78.57%,A组高于B组（P<0.05）;GOS评分方面,A组5分的发生率为92.86%,B组为73.81%,A组高于B组（P<0.05）。不良反应发生率方面,A组为2.38%,B组为21.43%,A组低于B组（P<0.05）。复发率方面,A组无一例复发,B组复发率为4.76%,A组低于B组（P<0.05）。结论:Lvis支架辅助弹簧圈血管内栓塞治疗颅内破裂动脉瘤,临床效果好且具有一定安全性。 【关键词】颅内破裂动脉瘤;Lvis支架;弹簧圈血管内栓塞     

颅内动脉瘤介入栓塞术后二次复发的影响因素分析

目的 探讨颅内栓塞术后复发动脉瘤介入治疗后再复发的影响因素。方法 采用回顾性队列研究方法。纳入2010年1月—2016年12月北京市大兴区人民医院神经外科二次介入栓塞术治疗的复发动脉瘤患者69 例,其中男27例、女42 例,年龄25~76(48±10)岁;二次介入手术后再复发13例,再复发率为18.8%(13/69)。采用单因素分析及Logistic回归分析方法, 分析复发颅内动脉瘤介入治疗后再复发的影响因素。结果 单因素分析显示,复发组与非复发组患者性别、年龄、合并高血压、合并糖尿病、吸烟、 动脉瘤瘤颈宽度、动脉瘤部位、是否支架辅助比较,差异均无统计学意义(P值均＞0.05);而两组患者动脉瘤大小、手术前后改良RANKIN量表(mRS)评分变化情况、术后Raymond分级比较,差异均有统计学意义(Z=-3.396、-5.955、-5.825, P值均＜0.05)。Logistic回归分析显示:以RaymondⅠ级为参照,RaymondⅡ级(OR=0.116,95%CI 0.025~0.546, P＜0.01)和Raymond Ⅲ级(OR=0.052, 95%CI 0.008~0.350, P＜0.01)为二次介入栓塞术后动脉瘤再复发的独立危险因素。结论 栓塞不完全(RaymondⅡ级和Ⅲ级)是二次介入栓塞术后动脉瘤再复发的独立危险因素;对于再复发的颅内动脉瘤,二次介入术中选择合适的弹簧圈,尽可能栓塞完全无残留,意味着更低的再复发率。     

基于三维医学影像的脑动脉瘤内血液流动的数值模拟

目的 利用数值模拟研究具有病人特异性的脑动脉瘤内的血液流动,为脑动脉瘤的破裂风险的评价和动脉瘤介入栓塞后复发风险的评价提供帮助。方法 从两例脑动脉瘤病人的3D-RA数据中重建动脉瘤几何模型,血液流变学模型选择假塑性非牛顿流体模型,利用商用CFD软件Fluent对两例动脉瘤内的血液流动进行数值模拟。结果 数值模拟给出了动脉瘤内的流线图、重要截面上的速度分布图、壁面上的切应力分布和压力分布图。并且绘制了在收缩期时刻动脉瘤颈部和瘤顶部各20个点上的壁面切应力和压力的变化情况。结论 血流动力学因素如流速、压力、壁面切应力、流动对壁面的冲击状况等因素与动脉瘤的生长和破裂密切相关,而由于脑动脉瘤形态各异、载瘤动脉与动脉瘤体的几何关系复杂,所以具有病人特异性的数值模拟对于研究动脉瘤破裂和复发风险具有重要价值。动脉瘤颈部的壁面切应力和壁面切应力的波动的变化规律并不相同,需要进一步研究壁面切应力的波动与脑动脉瘤生长与破裂之间的定量关系。     

A clinical analysis of twelve cases of ruptured cerebral de novo aneurysms

Formation of cerebral de novo aneurysms (CDNA) is rare, and the pathogenesis remains obscure. In this study, we investigated the factors that contribute to the formation of CDNA and suggest guidelines for following patients treated for cerebral aneurysms. We retrospectively reviewed 2,887 patients treated for intracranial aneurysm at our institute from January of 1976 to December of 2005. Of those patients, 12 were readmitted due to recurrent rupture of CDNA, which was demonstrated by cerebral angiography. We assessed clinical characteristics, such as gender, size and site of rupture, past history, and the time to CDNA rupture. Of the 12 patients, 11 were female and 1 was male, with a mean age at rupture of the first aneurysm of 44.7 years (range: 30-69 years). The mean time between the first episode of subarachnoid hemorrhage (SAH) and the second was 8.9 years (range: 1.0-16.7 years). The most common site of ruptured CDNA was the internal carotid artery (5 patients, 41.7%), followed by basilar artery bifurcation (3 patients, 25.0%). In the remaining 4 patients, rupture occurred in the anterior communicating, middle cerebral, anterior cerebral (A1), or posterior cerebral (P1) arteries. In 5 cases (41.7%), the CDNA occurred contralateral to the initial aneurysm. Eleven patients (91.7%) had a past history of arterial hypertension. There was no history of habitual smoking or alcohol abuse in any of the patients. Eight patients underwent clipping for CDNA and three patients were treated with coiling. One patient who had multiple aneurysms was treated with clipping following intra-aneurysmal coiling. Assessment according to the Glasgow Outcome Scale (GOS) of the patients after the treatment was good in 10 cases (83.3%) and fair in 2 cases (16.7%). Although formation of CDNA after successful treatment of initial aneurysm is rare, several factors may contribute to recurrence. In our study, female patients with a history of arterial hypertension were at higher risk for ruptured CDNA. We recommend follow-up imaging studies every five years after treatment of the initial aneurysm, especially in women and those with a history of arterial hypertension.     

分支血管直径对颅内动脉瘤置入血流导向装置后血流动力学参数的影响

目的综合考虑血流导向装置(flow diverter,FD)置入对动脉瘤瘤体及分支血管的影响,为临床制定更加合理的FD栓塞颅内动脉瘤手术策略提供参考。方法基于计算流体动力学(computational fluid dynamics,CFD)方法,创新应用多孔介质模型模拟FD栓塞颅内分叉动脉瘤的过程。分析和比较不同分支血管直径条件下FD置入动脉瘤前后瘤体与分支血管血液流场、血流速度、壁面压力、壁面剪切力(wall shear stress,WSS)等血流动力学参数的变化。结果 FD置入改变动脉瘤内的血流动力学特征,血流速度减小,动脉瘤壁尤其是顶部压力减小,瘤颈口WSS增大,但瘤颈远侧端与近侧端WSS的差异减小。且不同分支血管直径对血流动力学特征改变的影响程度不同,直径越大,FD置入后流入分支血管内血流的减少量越大,但瘤体内血液流速与瘤顶压力的减少量越小,同时瘤颈部WSS增加量越小。结论分支血管直径越大,FD对动脉瘤的栓塞治疗效果与对血管粥样硬化的改善作用越差,越易造成分支闭塞或其他缺血性并发症的发生。此类情况下进行FD介入栓塞术尤其需要引起临床医师注意。     

Risk Factors for Intraprocedural Rerupture during Embolization of Ruptured Intracranial Aneurysms

BackgroundIntraprocedural rupture (IPR) is a devastating complication in endovascular treatment of ruptured intracranial aneurysms, but its risk factors have not been fully assessed. This study was performed to explore the risk factors for IPR during embolization of ruptured cerebral aneurysms.MethodsA total of 1,494 patients with ruptured intracranial aneurysms who underwent endovascular interventional embolization were enrolled. Clinical characteristics were collected for each patient. Univariate and multivariate logistic regression analysis was employed to identify the factors independently associated with IPR. A receiver operating characteristic (ROC) curve analysis was performed to determine the cutoff values of continuous variables predicting IPR.ResultsForty-one patients suffered from IPR (2.7%). Multivariate logistic regression analysis indicated that aneurysm size (odds ratio [OR], 0.819; 95% confidence interval [CI], 0.732–0.916), aneurysms with irregular morphology (OR, 2.162; 95% CI, 1.143–4.091), time from symptom onset to intervention (OR, 1.615; 95% CI, 1.207–2.161), and vasospasm during embolization (OR, 2.021; 95% CI, 1.038–3.934) were the independent risk factors of IPR. ROC curve analysis showed that the area under the curve for aneurysm size and time from onset to intervention were 0.697 (cutoff value, 3.4 mm; sensitivity, 78.8%; and specificity, 53.7%) and 0.659 (cutoff value, 2 days; sensitivity, 78.0%; and specificity, 45.2%), respectively.ConclusionAneurysms with irregular morphology, aneurysms ≤ 3.4 mm in diameter, time from onset to intervention > 2 days and cerebral vasospasm during embolization are independent risk factors for IPR during coil embolization of ruptured aneurysms. More attention should be paid to the factors increasing the risk of IPR in patients with ruptured aneurysms so as to minimize this complication.     

Effects of framing coil shape, orientation, and thickness on intra-aneurysmal flow

To study the effects of the geometrical characteristics of a framing coil on aneurysm thromboembolization efficacy, the hemodynamics in lateral aneurysms filled with coils having a different shape, orientation, and thickness were analyzed using computational fluid dynamics. The aneurysms packed with vortex and cage-shaped coils were modeled using three different coil orientations: transverse, parallel, and orthogonal. The orthogonal orientation of a vortex coil and parallel orientation of a cage-shaped coil showed higher inflow, vorticity, and wall shear stress in the dome region, which provide an unfavorable hemodynamic environment for thromboembolization. Thicker coils also produced unfavorable hemodynamic conditions compared to normal coils having the same shape, orientation, and total coil volume. Though the effects of coil shape and orientation on the hemodynamic parameters of interest were not consistent, the open area at the distal half of the mid-transverse plane of an aneurysm showed significant positive correlation with flow into the dome region and mean vorticity in the dome region. Therefore, blocking the distal mid-transverse plane of an aneurysm using coils would effectively reduce the intra-aneurysmal flow activity and provide a more efficient hemodynamic environment for thromboembolization.     

Changes of flow characteristics by stenting in aneurysm models: influence of aneurysm geometry and stent porosity

An endovascular technique using a stent has been developed and successfully applied in the treatment of wide neck aneurysms. A stent can facilitate thrombosis in the aneurysm pouch while maintaining biocompatible passage of the parent artery. Insertion of the stent changes the flow characteristics inside the aneurysm pouch, which can affect the intra-aneurysmal embolization process. The purpose of this study is to clarify the velocity and wall shear stress changes that are caused by stenting in fusiform and lateral aneurysm models. We used a flow visualization technique that incorporated a photochromic dye in order to observe the flow fields and measure the wall shear rates. The intra-aneurysmal flow motion was significantly reduced in the stented aneurysm models. Coherent inflow along the distal wall of the aneurysm was diminished and inflow was distributed along the pores of the stent wall in the stented models. Also, sluggish intra-aneurysmal vortex motion was well maintained in the stented aneurysm models during the deceleration phase. A less porous stent generally reduced the intraneurysmal fluid motion further, but the porosity effect was not significant. The magnitude and pulsatility of the wall shear rate were reduced by stenting, and the reductions were more significant in the lateral aneurysm models compared to the fusiform aneurysm models. The hemodynamic changes that were observed in our study can help explain the efficacy of in vivo thrombus formation caused by stenting. © 2002 Biomedical Engineering Society. PAC2002: 8719Uv, 8780-y, 8719Xx     

单纯弹簧圈栓塞治疗颅内破裂宽颈动脉瘤的安全性和有效性

目的:探讨颅内宽颈动脉瘤破裂后急性期使用单纯弹簧圈栓塞治疗的安全性和有效性。方法:前瞻性研究。纳入2017年6月—2018年5月首都医科大学宣武医院神经外科符合要求的颅内破裂宽颈动脉瘤60例,其中男22例、女38例,年龄38～85(57±11)岁。术前Hunt-Hess分级Ⅰ级16例,Ⅱ级23例,Ⅲ级16例,Ⅳ级4例,...