颅内动脉瘤动物模型的最新进展和应用

颅内动脉瘤足蛛网膜下腔出血的主要原因,致死率和致残率都很高,其破裂风险分析研究依赖所制备的真实可靠的动脉瘤动物模型.探讨动脉瘤的形态、病生理、演变过程,建立颅内动脉瘤动物模型,探索其发病机制,对临床治疗具有重要意义.本文对建立动脉瘤模型的几种方法进行了比较评述,并在此基础上提出了一种新的颅内动脉瘤动物模型的制作方法.     

基于膨隆实验的血管非线性力学特性确定方法

目的基于实验测试和数值模拟结果,建立反方法确定血管的非线性力学特性。方法采用自行设计的实验装置,对血管进行压力加载,获取血管膨隆的实验数据;假设血管材料特性符合超弹性Ogden模型,建立血管膨隆的有限元模型,然后结合实测数据及数值模拟结果,利用优化算法建立反方法确定血管的力学特性。结果得到了描述兔腹主动脉非线性力学特性的Ogden模型一阶和二阶的材料参数,其中一阶Ogden模型参数α=10.86±1.98。经验证兔腹主动脉的力学特性可用超弹性力学模型描述。结论基于实验测试和数值模拟方法建立的反方法可用来识别血管的非线性力学特性。     

阻塞性睡眠呼吸暂停低通气综合征模型鼠软腭的力学重建

目的　研究阻塞性睡眠呼吸暂停低通气综合征 (OSAHS)咽腔呼吸压力对软腭力学特性的影响。方法　用SD鼠建立OSAHS动物模型 ,对动物模型的软腭进行单轴拉伸实验 ,离体检测软腭的弹性。结果　通过对照正常生理状态下SD鼠的实验结果 ,比较研究与OSAHS有关的软腭力学特性的变化规律和软腭重建现象。结论　实验研究表明 ,类似OSHAS发病情形的咽腔呼吸压力可引起软腭发生易于OSAHS形成和发展的重建     

基于Amira的OSAS动物模型阻塞形态可视化研究

上气道组织结构异常诱发的气道狭窄,是OSAS病人发生阻塞件呼吸暂停的病理学基础.通过动物实验.建立猪的OSAS模型.结合数字图像处理技术以及三维重建方法.从形态学上观测OSAS动物模型上气道阻塞部位及其形态.结果发现,模型猪在出现常见的OSAS表现30天之后.在其上气道鼻腔部位观测到明显的阻塞形态.表明建立的OSAS动物模型不仪可行,而且有效,能为OSAS力学仿真模型的建立以及OSAS疾病的临床诊治提供可靠基础.     

力学载荷干预骨缺损原位修复的实验模型研究

组织工程复合物用于骨缺损治疗是目前研究的热点,力学载荷对组织工程复合物在体成骨具有重要意义,相关研究越来越受到研究者们的关注.在组织工程研究领域,建立标准化的动物模型是进行实验研究的基础,用于探索不同力学载荷环境对骨缺损原位修复的影响及其作用机制.综述了力学载荷干预骨缺损修复实验模型的建立方法,对常用的动物选择、缺损制备、固定方法及载荷加载方式进行总结,为相关研究提供实验模型选择方面的参考.     

猪眼虹膜力学特性的实验研究

研究猪眼虹膜的生物力学特性.通过模拟闭角型青光眼发生时眼睛前后房的力学环境,设计了一种实验方法并建立了闭角型青光眼的动物模型,在不破坏虹膜组织的完整性并尽量保持其活性的前提下,对猪眼虹珑膜的力学特性进行测试,得到了猪眼虹膜的面应变与前后房压强差之间的关系,可表示为δ=b0 b1ln△P,它具有黏弹性性质.实验结果还可为解释青光眼致盲机理和临床分析青光眼的病理状况提供理论和实验基础.     

基于CT的脑动脉瘤三维重建的有限元模型

目的建立脑动脉瘤三维重建的有限元模型,为临床脑动脉瘤破裂力学机制分析提供基础。方法依据临床脑动脉瘤患者CT数据,结合MIMICS 8.1数字化医学影像处理软件,运用三维重建技术构造脑动脉瘤的实体结构,最后导入ANSYS有限元通用软件完成脑动脉瘤的有限元建模与力学分析。结果建立临床上适用于脑动脉瘤患者血流动力学分析的有限元模型。结论模型具有数字化、个性化特征,可用于脑动脉瘤血流动力学性能计算,分析临床脑动脉瘤患者动脉瘤的破裂机制。     

老龄深静脉血栓动物模型下腔静脉的力学特性

比较正常动物下腔静脉和老龄深静脉血栓动物模型下腔静脉的拉伸力学特性,为临床提供生物力学参数.对正常和各老龄深静脉血栓动物模型20个下腔静脉试样进行拉伸实验,将试样装夹在试验机软组织实验夹具上,以5 mm/min的实验速度对试样施加拉应力,实验环境温度为(36.5±1)％.以回归分析的方法处理实验数据.老龄模型组最大载荷,最大应力/最大位移和最大应变均小于正常对照组,差异显著(P＜0.05).拉伸曲线是以指数关系变化的,老龄深静脉血栓对下腔静脉力学特性具有一定影响.     

移植性肺癌动物模型的建立和研究进展

肺癌是目前对人类威胁最大的恶性肿瘤之一,其发病率呈逐年上升趋势.肺癌动物模型在研究人类肺癌的诊断和治疗等方面发挥非常重要的作用,建立肺癌动物模型为研究者探索肺癌发病机制、研究预防策略、评价临床疗效提供基础.本文从理想的模型实验动物、移植方法、三种不同的裸鼠移植性肺癌动物模型建立方法等方面对国内外移植性肺癌动物模型的研究现状作一综述.     

高G环境下大鼠胫骨的力学性能

背景:随着中国航天事业的发展,飞行员面临承受高G力学环境,这种环境会对飞行员骨骼造成严重影响。而胫骨作为最容易发生骨折的骨骼之一,目前对极端力学环境下胫骨生物力学研究较少。目的:通过高G离心加载装置制作动物模型,探究不同高G力学环境对大鼠生长发育和胫骨力学性能的影响。方法:取解放军军事医学科学院实验动物中心提供的雄性Wistar大鼠,通过高G离心加载装置设置悬臂以不同的转速和加速度运行模拟高G环境,并制作动物模型。每周称量大鼠体质量。取大鼠左侧胫骨进行三点弯曲实验,计算胫骨挠度、弹性模量、极限载荷;右侧胫骨进行蠕变实验,在胫骨中段皮质骨表面施加恒定应力并保持3600 s,观察其蠕变应变变化。实验已由天津理工大学动物伦理委员会批准。结果与结论:高G环境会影响大鼠正常生长发育,抑制体质量增长并降低了大鼠胫骨的力学性能,使胫骨的极限挠度分别下降了8.1%,12.2%,37.8%,51.4%;极限载荷分别下降了16%,9%,25.2%,29%。说明极端高G环境会对大鼠产生严重的负面作用。     

优化设计颅内动脉瘤用梯形截面支架底边长度

目的为降低梯形截面丝支架植入颅内囊状动脉瘤后瘤腔破裂的风险,对支架丝截面底边长度进行优化设计。方法构建38种不同底边长度的梯形截面支架及其植入动脉瘤后的有限元模型,利用流固耦合数值模拟计算得到38组最大瘤腔壁面压力梯度值,并应用广义回归神经网络及遗传算法对梯形截面底边长度进行优化,使植入支架后最大瘤腔壁面压力梯度降到最低。结果优化结果显示,相对传统矩形截面支架,优化后支架将最大瘤腔壁面压力梯度降低了7.86%。结论广义回归神经网络与遗传算法结合可以很好地解决支架优化方面的问题。     

The importance of parent artery geometry in intra-aneurysmal hemodynamics

We show the importance of arterial geometry in intra-aneurysmal hemodynamics. Using a new geometric parameterized saccular aneurysm model including parameters for parent artery shape and the configuration of the aneurysm in the parent artery, we performed a parametric computational fluid dynamics study. We examined lateral saccular aneurysm models with different aneurysm shapes (i.e., the ratio of aneurysm height to aneurysm neck diameter) and different configurations (i.e., the torsion angle of the aneurysm to the upstream part of the parent artery). The aneurysm lateral to the curve of the parent artery had significantly higher wall shear stress than the aneurysm inside or outside the curve of the artery, even with the same shape of the aneurysm. Our findings suggest the important role played by the configuration of the aneurysm relative to the parent artery in intra-aneurysmal hemodynamics.     

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.     

Renal arterial aneurysm--an incidental finding at autopsy

Herein we describe a rare case of saccular renal artery aneurysm seen as an incidental autopsy finding in an elderly, hypertensive female. The aneurysm was seen as a small exophytic mass with calcified wall and lumen occluded by recanalized thrombus.     

Tissue Responses to Endovascular Stent Grafts for Saccular Abdominal Aortic Aneurysms in a Canine Model

We investigated tissue responses to endoskeleton stent grafts for saccular abdominal aortic aneurysms (AAAs) in canines. Saccular AAAs were made with Dacron patch in 8 dogs, and were excluded by endoskeleton stent grafts composed of nitinol stent and expanded polytetrafluoroethylene graft. Animals were sacrificed at 2 months (Group 1; n = 3) or 6 months (Group 2; n = 5) after the placement, respectively. The aortas embedding stent grafts were excised en bloc for gross inspection and sliced at 5 to 8 mm intervals for histopathologic evaluation. Stent grafts were patent in all except a dog showing a thrombotic occlusion in Group 2. In the 7 dogs with patent lumen, the graft overhanging the saccular aneurysm was covered by thick or thin thrombi with no endothelial layer, and the graft over the aortic wall was completely covered by neointima with an endothelial layer. Transgraft cell migration was less active at an aneurysm than at adjacent normal aorta. In conclusion, endoskeleton stent grafts over saccular aneurysms show no endothelial coverage and poor transgraft cell migration in a canine model.     

蜿蜒型脑动脉瘤的血流动力学仿真

目的分析在一个心动周期中蜿蜒型脑动脉瘤的血液流动情形、压力和壁面切应力分布和变化情况。方法构建了二维理想化的蜿蜒型脑动脉瘤（有2个动脉瘤）几何模型。利用计算流体力学方法对生理性脉动流进行了数值仿真。选择6个相继的心动时刻来显示流腔内的流动。结果2个流腔内的流动情形和壁面切应力分布呈现相似的特征,而第2个动脉瘤的末端瘤口则呈现非常高的壁面切应力和很高的压力梯度,这将更易于导致动脉瘤的发展和破裂。结论血液流动特征可以帮助人们更好地理解在S形弯曲动脉上滋生的在体蜿蜒型动脉瘤的血流动力学特性。     

支架置入前脑动脉瘤血流场的特性分析

BACKGROUND: Cerebral aneurysm is a kind of mortal hemangioma, and its treatments such as endovascular embolization and clipping both cause high postoperative recurrence rate and mortality. So the stent implantation for cerebral aneurysm is coming into being. OBJECTTVE: To evaluate the hemodynamic parameters after stent implantation into cerebral aneurysm and to provide a novel feasible strategy for clinical treatment. METHODS: A retrospective analysis was preformed based on the CT image data of 11 patients with cerebral aneurysm from the Affiliated Hospital of Xinjiang Medical University. Firstly, the flexible and solid model of cerebral aneurysm was established by the MIMICS and reverse engineering. Secondly, the matching stent model was implanted into the cerebral aneurysm, and then the blood flow structure of cerebral aneurysm was analyzed by the fluid dynamics theory and the Fluent with the method of two-way flow solid coupling. Finally, comparative analysis of the kinetic parameters of cerebral aneurysm before and after implantation, including wall pressure, blood velocity, path line of the blood flow, wall shear stress, wall deformation was conducted, and blood flow characteristics after stent implantation were analyzed under different entrance velocity. RESULTS AND CONCLUSION: After implantation, the wall surface pressure was reduced about 61.1%; the blood flow velocity around the stent and the inside of the cerebral aneurysm was decelerated obviously; under setting 2 000 lines of blood flow, the number of path line of blood flow into the cerebral aneurysm reduced about 75.0%, the maximum wall shear stress decreased about 79.3%, and the maximum wall deformation reduced to a lower level. The entrance velocity was respectively v1=0.1 m/s, v2=0.2 m/s, v3=0.3 m/s and the wall pressure was in a gradient ascent; the wall shear stress increased with the velocity, meanwhile, τzou (left neck of aneurysm) <τzhong (aneurysm )< τyou (right neck of aneurysm). The path lines of blood flow mainly concentrated in the top of the aneurysm, and the blood velocity markedly affected the surface deformation. These results indicate that main hemodynamic parameters are obviously improved after stent implantation into cerebral aneurysm, and the blood velocity should never be neglectful in the treatment process.     

The molecular organization of collagen in saccular aneurysms assessed by polarized light microscopy

The known relationship between the retardation of polarized light and the molecular organization of collagen enabled us to study collagen in cerebral saccular aneurysms, structures in which the collagen is probably abnormal. Six aneurysms and their adjacent arteries, obtained at autopsy, were sectioned at a thickness of 7 microns. Measurements of retardation in hematoxylin and eosin stained sections, obtained by the method of de Sénarmont, were significantly lower in the aneurysm wall compared with the adventitial region of adjacent arteries. A similar reduction in retardation was found by imbibition analysis on unstained sections from three of the aneurysms. We propose that the difference in optical properties arises because the aneurysm collagen is immature and so is less organized at the molecular level. The presence of immature collagen could also explain the altered mechanical properties that are necessary for the enlargement and rupture of saccular aneurysms.     

A Magnetic Approach to Decrease Stent Graft Endoleak: <Emphasis Type="Italic">Ex-Vivo</Emphasis> Validation

Stent graft endoleak is a major problem in endovascular aneurysm repair (EVAR). Endoleak occurs after EVAR and may lead to aneurysm rupture, acute vessel thrombosis or occlusion. This study presents a novel design to potentially reduce endoleak with use of magnets. A ferromagnetic stent is deployed into the vessel lumen, and two external flexible magnetic rings are used to clamp on the proximal and distal necks of the stent. The rings impose epivascular magnetic pressure on the vessel wall to prevent the vessel wall from separating from the stent under elevated blood pressure. The geometry and magnetic properties of the stent and rings were designed to produce sufficient pressure, without overly compressing the vessel wall. Feasibility of this design was demonstrated with in vitro experiments using porcine abdominal aortas. The experiments showed that magnetic ring significantly improved the seal between the stent and vessel wall with use of moderate-sized stent. For aortas subjected to physiological axial stretch, rings that generate magnetic pressure of about 45 mmHg were found sufficient to prevent endoleak at pressure of 140 mmHg. Evaluation of this design in an in vivo animal model of aortic aneurysm is warranted.     

Histopathologic characteristics of a saccular aneurysm arising in the non-branching segment of the distal middle cerebral artery

Currently, the characteristics of aneurysms arising in the distal middle cerebral artery (dMCA) are not well understood. Here, we report the case of a 56-year-old woman with a ruptured saccular aneurysm in the M2 segment of the middle cerebral artery (MCA). The patient presented with a disturbance of consciousness, and computed tomography revealed a subarachnoid hemorrhage that angiography disclosed as a result of a saccular-type aneurysmal dilatation in the M2 segment of the left MCA. We excluded infection, inflammation, trauma, and neoplasia as causes of the aneurysm. Pathologic examination confirmed a ruptured saccular aneurysm of the dMCA that was unrelated to a branching zone. The aneurysmal wall was composed primarily of αSMA-positive and calponin/desmin-negative spindle cells and lacked internal elastic lamina, which was completely disrupted at the neck of the aneurysm. There was a strong positive immunoreactivity for matrix metalloproteinases (MMPs) 1, 2, and 9 in the spindle cells of the aneurysmal wall. In contrast, tests for MMP-8 were negative. The parent artery showed thickening of both the intima and media, with preservation of the internal elastic lamina. Atherosclerosis was not detected in either the parent artery or aneurysm. These findings suggest that an overexpression of MMPs may contribute to the development of saccular aneurysms in regions of the arterial trunk unrelated to branching zones.