密网孔支架对脑动脉瘤内流体力学的影响

血管内栓塞治疗已成为颅内动脉瘤治疗的一种重要方法[1].血管内支架已被用于辅助复杂动脉瘤的栓塞治疗,并且发挥改变血流动力学的作用[2].本研究旨在设计密网孔支架并模拟支架置入载瘤动脉以覆盖瘤颈,研究该支架置入对宽颈及窄颈动脉瘤内血流动力学变化的影响.     

侧壁动脉瘤形态特点与血流关系的计算机数值模拟分析

目的 利用三维计算机血流动力学数值模拟技术分析不同形态侧壁动脉瘤的血流特点.方法 选取资料完整的侧壁动脉瘤患者14例,在三维计算机断层扫描血管造影(CTA)图像基础上,利用本课题组自写程序及美国Fluent公司的Fluent 6.02等,对动脉瘤进行三维计算机血流动力学数值模拟,得出动脉瘤血流速度、轨迹、剪切力等多项参数,结合动脉瘤形态特点进行对比分析.结果　根据分析结果　将患者侧壁动脉瘤分为两种类型.Ⅰ型:动脉瘤长径与载瘤动脉中心轴不共面,模拟结果　显示动脉瘤中有涡流产生,血流速度范围0.86～1.03 m/s.Ⅱ型:动脉瘤长径与载瘤动脉中心轴共面,模拟结果　显示动脉瘤中无明显涡流产生,血流速度范围0～0.013 m/s.结论　从Ⅰ、Ⅱ型动脉瘤特点可知,侧壁动脉瘤的形态特点决定瘤内血流特点.

Abstract：

Objective By 3D-computational numerical simulation, to analyze the hemodynamic characters of different lateral aneurysms. Methods In 14 cases of lateral aneurysm with complete clinical data, on the basis of 3D-CTA image, self-designed program and Fluent 6. 02 softwares were used to simulate blood flow in the aneurysm. The blood velocity, fluid track, wall shearing stress, etc. were obtained.Results The patients were claffied into two types: Type Ⅰ , the longest diameter of the aneurysm and the central axis of the mother artery were not in the same plane, there was turbulent flow, and the blood velocity was 0. 86-1.03 m/s; Type Ⅱ: the longest diameter of the aneurysm and the central axis of the mother artery were in the same plane, there was no typical turbulent flow, and the blood velocity was 0-0. 013 m/s.Conclusion From the characters of types Ⅰ and Ⅱ aneurysm, It is speculated that the hemodynamics is related to the morphology of lateral aneurism.     

动脉瘤模型栓塞前后血流动力学的改变

目的评价动脉瘤模型行腔内微弹簧圈栓塞前后血流动力学的改变，用以判断疗效。方法运用改进的显微外科技术建立犬颈总动脉（CCA）动脉瘤模型22个，其中侧壁型12个。分叉部4个，末端型6个。术后7～14d行彩色多普勒超声、经颅多普勒（TCD）、数字减影动脉血管造影（IADSA）及经微导管动脉瘤内测压，然后以微弹簧圈紧密填塞动脉瘤腔，栓塞后重复进行上述检查，比较栓塞前后血流动力学变化。结果所建模型均获成功。实验证实，动脉瘤微弹簧圈栓塞前后其血流动力学参数的差异有统计学意义（P〈0．01）。结论实验所建动物模型是研究动脉瘤血管内栓塞治疗的理想方法；动脉瘤微弹簧圈栓塞后，能减低、改变或消除载瘤动脉及动脉瘤内异常血流动力学状态，终止动脉瘤行为，防止动脉瘤扩大和破裂。     

动脉瘤模型栓塞前后血流动力学对比研究

目的 评价动脉瘤模型行腔内微弹簧圈栓塞前后血流动力学的改变，用以判断疗效。方法 运用改进的显微外科技术建立犬颈总动脉（CCA）动脉瘤模型22个，其中侧壁型12个，分叉部4个，末端型6个。术后7～14d行彩色多普勒超声、经颅多普勒（TCD）、数字减影动脉血管造影（IADSA）及经微导管动脉瘤内测压，然后以微弹簧圈紧密填塞动脉瘤腔，栓塞后重复进行上述检查，比较栓塞前后血流动力学变化。结果 所建模型均获成功。实验证实，动脉瘤微弹簧圈栓塞前后其血流动力学参数的差异有统计学意义（P〈0．01）。结论 实验所建动物模型是研究动脉瘤血管内栓塞治疗的理想方法；动脉瘤微弹簧圈栓塞后，能减低、改变或消除载瘤动脉及动脉瘤内异常血流动力学状态，终止动脉瘤行为，防止动脉瘤扩大和破裂。     

支架在颅内动脉瘤治疗中的实验研究

目的 探讨囊状动脉瘤血管内单纯支架治疗前、后血流动力学、继发的组织病理学变化。方法 采用静脉移植法将9条犬制成9个颈总动脉侧壁动脉瘤模型,约3mm×3mm大小。1周后行彩色多普勒及DSA检查,5条犬于动脉瘤口成功置入支架。4条为对照组。1个月后再行彩色多普勒、DSA及组织病理学检查。结果 DSA、彩色多普勒能显示动脉瘤位置、形态,支架置入前、后瘤体内及载瘤动脉内血流循环状态。置入支架组1个月后瘤腔闭塞,新生内膜环绕支架金属丝表面。结论 支架置入后改变动脉瘤附近血液动力学、继发局部组织病理学改变,有利于促进动脉瘤腔内血栓形成。     

Neuroform Atlas支架在颅内动脉分叉处宽颈动脉瘤栓塞中的应用体会

目的 探讨Neuroform Atlas支架在颅内动脉分叉处宽颈动脉瘤栓塞中的价值。方法 回顾性分析2021年1～9月16例采用Neuroform Atlas支架辅助弹簧圈栓塞治疗颅内动脉分叉处宽颈动脉瘤的临床和影像学资料。动脉瘤位于大脑中动脉分叉处8例，大脑前动脉分叉处4例，大脑前、中动脉分叉处2例，大脑前动脉A2远端分叉处1例，大脑后动脉P2分叉处1例。破裂动脉瘤10例(术前Hunt-Hess分级Ⅰ级6例，Ⅱ级2例，Ⅲ级2例),未破裂动脉瘤6例。结果 均在单一Neuroform Atlas支架辅助下完成栓塞，技术成功率100%。术后即刻造影显示动脉瘤完全闭塞13例，瘤颈残留2例，瘤体残留1例。术中及围手术期未观察到介入操作相关并发症。出院前改良Rankin量表(mRS)0～1分11例，2分3例，3分2例。16例随访时间3～14个月，(7.8±3.2)月。mRS评分0～1分14例，2分1例，3分1例。9例术后3～6个月行DSA,动脉瘤完全闭塞8例，瘤颈残留1例，9例均未见载瘤动脉狭窄或支架内闭塞。结论 Neuroform Atlas支架辅助弹簧圈栓塞治疗颅内动脉分叉处宽颈动脉瘤安全，...     

右大脑后动脉第二段巨大动脉瘤孤立术一例

患者 男，23岁，“因头痛、头昏伴视物模糊、行走不稳进行性加重2月余”由外院转入。外院MRI诊断“右侧大脑脚占位”。查体：一般情况好，眼底视乳头不清，右侧面部感觉减退，左侧肢体肌力Ⅳ^＋。MR示中脑和桥脑的右侧有一个直径4．0cm混杂信号占位。DSA显示右侧大脑后动脉第二段（P2段）巨大动脉瘤。入院完成检查后在插管全麻下行右侧颞下开颅，术中将小脑幕游离缘切开，见动脉瘤巨大，瘤颈由第二段起始部一直延伸到中脑顶盖前方，瘤体大部分被小脑幕掩盖，载瘤动脉已变成动脉瘤颈的一部分，动脉瘤颈宽度超过2．0cm，无法夹闭，亦无法切除动脉瘤后行载瘤动脉重建或用多个Sugita窗式直角型动脉瘤夹夹闭瘤颈，决定行动脉瘤孤立术。分别于P2段起始部、后交通动脉远端、P3段起始端阻断大脑后动脉，切开瘤体，瘤壁厚，含大量机化血栓，瘤腔并不大，取出可以取出的血栓，使瘤体缩小，但部分瘤体与脑干粘连紧密无法完全分离、切除。     

LEO支架结合微弹簧圈栓塞治疗宽颈动脉瘤2例报道

颅内宽颈动脉瘤一直是血管内治疗的难点问题，但随着Remodeling技术又称载瘤动脉球囊再塑型技术和各种支架辅助弹簧圈栓塞技术逐渐应用于临床，为颅内宽颌动脉瘤的治疗提供了一项较为理想的治疗方法。本文报道应用新型可伸缩的自膨式支架（LEO）辅助微弹簧圈栓塞治疗2例宽颈动脉瘤的初步体会并结合文献进行复习。     

改进手术技术制作的犬囊状动脉瘤模型

目的 改进手术技术，简化模型制作程序，提高动脉瘤模型制作成功率。方法 运用改进的手术技术将犬的颈外静脉囊吻合到颈总动脉（CCA）建立动脉瘤（AN）模型，包括：侧壁型15个，分叉部6个，末端型6个，术后7～14d行影像学检查，大体观察证实动脉瘤的形成情况。结果 术后动物全部健康成活，建立AN模型27个，制作成功率90％（27／30）。模型可持续存在达9周。结论 显微手术技术对模型形成的影响很大，该改进方法制作的模型较为理想，能模仿出人类动脉瘤的血流动力学，瘤体大小及载瘤动脉管径，且能进行常规导管介入神经外科操作。     

多技术联合应用于颅内巨大动脉瘤的显微外科治疗

目的 探讨神经电生理监测、术中超声、术中荧光造影、神经内镜多技术联合应用于颅内巨大动脉瘤的显微外科手术治疗的临床效果。方法 回顾性分析显微手术治疗颅内巨大动脉瘤17例的临床资料。术前采用3D-CTA、MRI和DSA,充分评估动脉瘤的位置、大小和形状。术中应用神经电生理监测评价动脉瘤夹闭前、后的神经功能保留和损害程度;通过微血管多普勒超声的定性和定量分析联合术中荧光造影评定动脉瘤和周围邻近血管的血液流速及通畅度;神经内镜观察动脉瘤区的局部解剖,辨认重要的穿支血管、瘤颈结构和动脉瘤夹情况。手术在手术显微镜下操作,采用载瘤动脉控制性技术、瘤颈成形技术、动脉瘤内减压和切除技术、多瘤夹夹闭技术和血管痉挛保护技术等进行联合治疗。 结果 在多技术联合监测下,显微外科手术成功夹闭巨大动脉瘤17个,术后恢复良好15例,出现轻偏瘫1例,重度偏瘫l例,无死亡病例。DSA复查示瘤颈夹闭完全,载瘤动脉通畅。远期随访仍在进行中。 结论 多技术联合显微手术技术,能有效提高颅内巨大动脉瘤的手术疗效。     

Effects of arterial geometry on aneurysm growth: three-dimensional computational fluid dynamics study

OBJECT: Few researchers have quantified the role of arterial geometry in the pathogenesis of saccular cerebral aneurysms. The authors investigated the effects of parent artery geometry on aneurysm hemodynamics and assessed the implications relative to aneurysm growth and treatment effectiveness. METHODS: The hemodynamics of three-dimensional saccular aneurysms arising from the lateral wall of arteries with varying arterial curves (starting with a straight vessel model) and neck sizes were studied using a computational fluid dynamics analysis. The effects of these geometric parameters on hemodynamic parameters, including flow velocity, aneurysm wall shear stress (WSS), and area of elevated WSS during the cardiac cycle (time-dependent impact zone), were quantified. Unlike simulations involving aneurysms located on straight arteries, blood flow inertia (centrifugal effects) rather than viscous diffusion was the predominant force driving blood into aneurysm sacs on curved arteries. As the degree of arterial curvature increased, flow impingement on the distal side of the neck intensified, leading to elevations in the WSS and enlargement of the impact zone at the distal side of the aneurysm neck. CONCLUSIONS: Based on these simulations the authors postulate that lateral saccular aneurysms located on more curved arteries are subjected to higher hemodynamic stresses. Saccular aneurysms with wider necks have larger impact zones. The large impact zone at the distal side of the aneurysm neck correlates well with other findings, implicating this zone as the most likely site of aneurysm growth or regrowth of treated lesions. To protect against high hemodynamic stresses, protection of the distal side of the aneurysm neck from flow impingement is critical.     

Patient-specific hemodynamic analysis of small internal carotid artery-ophthalmic artery aneurysms

BackgroundProphylactic treatment of unruptured small brain aneurysms is still controversial due to the low risk of rupture. Distinguishing which small aneurysms are at risk for rupture has become important for treatment. Previous studies have indicated a variety of hemodynamic properties that may influence aneurysm rupture. This study uses hemodynamic principles to evaluate these in the context of ruptured and unruptured small aneurysms in a single location.MethodsEight small internal carotid artery-ophthalmic artery (ICA-Oph) aneurysms (<10 mm) were selected from the University of California, Los Angeles, database. We analyzed rupture-related hemodynamic characteristics including flow patterns, wall shear stress (WSS), and flow impingement using previously developed patient-specific computational fluid dynamics software.ResultsMost ruptured aneurysms had complicated flow patterns in the aneurysm domes, but all of the unruptured cases showed a simple vortex. A reduction in flow velocity between the parent artery and the aneurysm sac was found in all the cases. Inside the aneurysms, the highest flow velocities were found either at the apex or neck. We also observed a trend of higher and more inhomogeneous WSS distribution within ruptured aneurysms (10.66 ± 5.99 Pa) in comparison with the unruptured ones (6.31 ± 6.47 Pa) (P < .01).ConclusionA comparison of hemodynamic properties between ruptured and unruptured small ICA-Oph aneurysms found that some hemodynamic properties vary between small aneurysms although they are similar in size and share the same anatomical location. In particular, WSS may be a useful hemodynamic factor for studying small aneurysm rupture.     

Rheological characteristics of the aneurysm at the middle cerebral artery bifurcation]

We performed a retrospective clinical study to estimate the morphological index such as aspect ratio (aneurysm depth/neck) and area ratio (ratio of the cross-sectional area of bifurcated arteries) of 64 cases with saccular aneurysms (ruptured aneurysms: 41, unruptured aneurysms: 23) at the bifurcation of the middle cerebral artery (MCA) and made a flow visualization study using a flat three dimensional acrylic aneurysm model to define the flow characteristics in conditions similar to those obtained from the clinical study. The mean aspect ratio and area ratio of the ruptured and unruptured aneurysm cases were 2.81 +/- 1.45, 2.52 +/- 0.91 and 1.56 +/- 0.59, 1.73 +/- 0.38. These respective values differ statistically. The area ratio of the MCA bifurcation with no aneurysm was 1.25 +/- 0.35. This value was also statistically different from the ruptured aneurysm case. The visualization study was performed changing the neck size and flow ratio into the peripheries to simulate various aspect ratio and flow ratio into peripheries. The results showed that intraanerysmal flow was definitely influenced by aspect ratio and area ratio. The aspect ratio over 2.0 and area ratio below 2.0 failed to drive the inflow inside the aneurysms and developed as a stagnant area in the dome side. The morphological index of aspect ratio and area ratio reflected the flow characteristics in the aneurysm and was statistically different in ruptured and unruptured aneurysm cases. The unruptured aneurysms with an aspect ratio of more than 1.6 and an area ratio of more than 2.0 must be followed up, because of the risk that they might rupture in the near future.     

Pressure distribution on the wall of experimental aneurysms

Summary Since it is known that turbulent flow exists in aneurysms, we have investigated whether pressure might be distributed unevenly on the aneurysmal wall, and whether it varies with the shape and size of the aneurysm and its orifice diameter as well as with the direction of blood flow in the parent vessel. It was found that in some instances, such as with aneurysms having narrow necks and situated at 90 degrees to the parent vessel blood flow, aneurysmal pressure is relatively low.     

前循环动脉瘤的介入治疗（附40例分析）

目的 探讨前循环动脉瘤介入栓塞的临床疗效及并发症的处理.方法 对40例前循环动脉瘤患者采用介入栓塞治疗（42枚）,其中颈内动脉动脉瘤2例（2枚）,大脑中动脉动脉瘤18例（20枚）,前交通动脉瘤15例（15枚）,大脑中-后交通动脉动脉瘤5例（5枚）.结果 介入栓塞动脉瘤40例（42个）,栓塞率达100％的36个,95％的5个,90％的1个.随访共37例,3例失访.所有患者均复查头颅CT,原则上要求均复查DSA,但5例因经济原因不愿意复查DSA.32例患者均于出院后6个月复查DSA,2例复发,其中1例弹簧圈向瘤内移位,瘤颈部位复发;复查头颅CTA的患者中1例为90％栓塞,6个月后出现瘤颈少许显影,2例患者均再次使用电解可脱式铂金螺旋圈后达100％栓塞.术后恢复良好.结论 采用电解可脱式铂金螺旋圈治疗前循环动脉瘤效果好、并发症少、恢复快,近期效果显著.     

A proposed parent vessel geometry-based categorization of saccular intracranial aneurysms: computational flow dynamics analysis of the risk factors for lesion rupture

OBJECT: The authors created a simple, broadly applicable classification of saccular intracranial aneurysms into three categories: sidewall (SW), sidewall with branching vessel (SWBV), and endwall (EW) according to the angiographically documented patterns of their parent arteries. Using computational flow dynamics analysis (CFDA) of simple models representing the three aneurysm categories, the authors analyzed geometry-related risk factors such as neck width, parent artery curvature, and angulation of the branching vessels. METHODS: The authors performed CFDAs of 68 aneurysmal geometric formations documented on angiograms that had been obtained in patients with 45 ruptured and 23 unruptured lesions. In successfully studied CFDA cases, the wall shear stress, blood velocity, and pressure maps were examined and correlated with aneurysm rupture points. Statistical analysis of the cases involving aneurysm rupture revealed a statistically significant correlation between aneurysm depth and both neck size (p < 0.0001) and caliber of draining arteries (p < 0.0001). Wider-necked aneurysms or those with wider-caliber draining vessels were found to be high-flow lesions that tended to rupture at larger sizes. Smaller-necked aneurysms or those with smaller-caliber draining vessels were found to be low-flow lesions that tended to rupture at smaller sizes. The incidence of ruptured aneurysms with an aspect ratio (depth/neck) exceeding 1.6 was 100% in the SW and SWBV categories, whereas the incidence was only 28.75% for the EW aneurysms. CONCLUSIONS: The application of standardized categories enables the comparison of results for various aneurysms' geometric formations, thus assisting in their management. The proposed classification system may provide a promising means of understanding the natural history of saccular intracranial aneurysms.     

Flow Dynamics in Expansions Characterizing Abdominal Aorta Aneurysms

Our purpose was to identify and quantify hemodynamic factors contributing to the generation, proliferation, and rupturing of abdominal aorta aneurysms (AAAs) using a computational investigation of steady laminar and turbulent flow in AAA models. Steady laminar and turbulent flows were computed using the incompressible Navier-Stokes equations. Flow fields in symmetric shapes of different extents and degrees of expansion are presented first. Two representative cases of asymmetric AAAs are considered next: an aneurysm with an elliptic cross section and an aneurysm with preferential expansion in one direction. For symmetric aneurysms, parametric studies are presented. For asymmetric aneurysms, flow fields are computed only for high flow rates representative of systolic flow. For all cases, a recirculating flow region was found in the expanded part of the AAA. Recirculation is accompanied by a minor increase in pressure but a significant increase in wall shear stress. For cases where turbulent flow was considered, it was found that the recirculation zone diminishes but the computed wall shear stress reaches levels higher than laminar flow. The levels of wall shear stress reached in turbulent flow may cause lesions of the aneurysmal wall. The minor variation of pressure within the aneurysms with smooth expansions indicates that the structural properties of the arterial wall tissue may play a significant role for the generation and subsequent proliferation of the aneurysm. However, the high values of the wall shear stress in AAAs appear to be an important hemodynamic factor that may contribute to wall degeneration and eventual rupturing. The recirculating flow in AAAs may explain the generation of intraluminal thrombi. Furthermore, the asymmetry and complexity of the flow in asymmetric AAAs may explain the frequently observed asymmetric thrombi distribution.     

A loose-packing approach for coil embolization of giant intracranial aneurysm

Endoluminal occlusion of giant intracranial aneurysms with coil embolization is a viable endovascular treatment option alternative to surgical clipping. However, due to the relatively large aneurysm size, the use of embolization coils for giant aneurysms could be great. A loose-packing embolization strategy in which the fundus of the aneurysm is loosely packed while the aneurysm base is tightly packed is presented. Such a coiling strategy is best suited to giant aneurysms of elongated configuration and narrow neck as illustrated in the present case. While the use of the loose-packing approach is recommended for elongated aneurysms with a narrow neck, its use is not to be generalized for aneurysms of other configurations.     

Flow diversion treatment: intra-aneurismal blood flow velocity and WSS reduction are parameters to predict aneurysm thrombosis

Background

To evaluate the haemodynamic changes induced by flow diversion treatment in cerebral aneurysms, resulting in thrombosis or persisting aneurysm patency over time.

Method

Eight patients with aneurysms at the para-ophthalmic segment of the internal carotid artery were treated by flow diversion only. The clinical follow-up ranged between 6?days and 12?months. Computational fluid dynamics (CFD) analysis of pre- and post-treatment conditions was performed in all cases. True geometric models of the flow diverter were created and placed over the neck of the aneurysms by using a virtual stent-deployment technique, and the device was simulated as a true physical barrier. Pre- and post-treatment haemodynamics were compared, including mean and maximal velocities, wall-shear stress (WSS) and intra-aneurysmal flow patterns. The CFD study results were then correlated to angiographic follow-up studies.

Results

Mean intra-aneurysmal flow velocities and WSS were significantly reduced in all aneurysms. Changes in flow patterns were recorded in only one case. Seven of eight aneurysms showed complete occlusion during the follow-up. One aneurysm remaining patent after 1?year showed no change in flow patterns. One aneurysm rupturing 5?days after treatment showed also no change in flow pattern, and no change in the maximal inflow velocity.

Conclusions

Relative flow velocity and WSS reduction in and of itself may result in aneurysm thrombosis in the majority of cases. Flow reductions under aneurysm–specific thresholds may, however, be the reason why some aneurysms remain completely or partially patent after flow diversion.