血管内支架三角形截面结构流阻的数值模拟实验

利用数值模拟方法分析新型的三角形截面支架的血液流阻,找出影响血流动力学的支架结构参数,为血管内支架结构设计和优化提供参考依据.通过SoildWorks软件构建了三角形截面裸支架在无限流场中的4种模型,借助ANSYS有限元软件分别对4种模型进行计算流体力学数值模拟,分析模型施加非定常流之后的流动情形、压力分布和流阻的变化情况.结果提示三角形截面形状的支架应用于动脉瘤可以使血流流入瘤腔的阻力大而流出瘤腔的阻力小,导致血液流出容易流入难,从而抑制瘤腔的血液灌注和流动,能够降低瘤腔内的压力,对于动脉瘤的治疗起到一定的效果,这为今后支架结构的设计提供了一些理论指导意义.     

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.     

血管内超弹性TiNi合金支架的有限元模型及流体动力学计算分析

利用有限元模型与计算流体动力学的方法,结合有限元软件COSMOS Works与计算流体动力学软件COSMOSFloWorks,分析了具有特殊形状记忆和超弹性功能的TiNi支架在置入过程中与斑块、血管的相互作用及其对血流情况的影响.计算结果表明,使用COSMOS可较为准确地模拟TiNi合金支架的超弹性;由于具有形状记忆特征,TiNi支架置入后对血管产生更好的顺应性,不易损伤血管壁;利用TiNi材料的超弹性,大变形时会产生更大的支撑力的优势,适当缩短支撑筋的长度来增加支架的支撑力;TiNi合金超弹性产生的柔顺性能让血液流动更畅通,降低血管的再狭窄率.     

瓦楞状组织工程骨支架对种子细胞接种和成骨的影响

背景：不同形状工程骨支架负载种子细胞修复骨缺损的研究效果评价不一,而负载细胞数量的多少是影响疗效的重要因素之一,目前该方面研究证据不多。目的：自制瓦楞状组织工程骨支架和其他3种形状的支架,比较4种不同形状支架负载种子细胞的数量,以及瓦楞状组织工程骨支架体内成骨时凹槽的优势及特点。方法：①体外实验：将体积和样本数相同的4组支架分为单纯瓦楞状支架组、无瓦楞支架组、圆柱状支架组和带中空管柱状支架组,分别以相同密度、相同容积的成骨诱导兔骨髓间充质干细胞悬液接种于支架表面,孵育、培养、消化、收集,进行细胞计数、吸光度值检测以及碱性磷酸酶和茜素红染色。②体内实验：将兔随机分为重组人骨形态发生蛋白2/瓦楞状自固化磷酸钙人工骨组,瓦楞状自固化磷酸钙人工骨组和松质骨组,将体积相同的3组支架植入兔L_（5-6）两侧横突间,植入后4,8,12周行大体、组织学观察。结果与结论：体外实验显示,瓦楞状工程骨支架上滴注的细胞液能充分停留在表面,由于表面瓦楞状凹槽和液体的表面张力以及支架本身的无孔隙性使得细胞液不向培养皿流失,每个样本平均消化下来的正常形态的细胞数量高于其他3组（P〈0.05）,吸光度值差异无显著性意义（P〉0.05）。体内实验显示,各时间点重组人骨形态发生蛋白2/瓦楞状自固化磷酸钙人工骨组的成骨量比瓦楞状自固化磷酸钙人工骨组明显多（P〈0.05）,与松质骨组之间比较差异无显著性意义（P〉0.05）。结果证实,实验自制的瓦楞状工程骨支架的形状特点有利于种子细胞负载,从数量上保证了接种种子细胞的有效性,可促进支架大量成骨和段状骨缺损的愈合。     

彩色多普勒超声及能量图对软组织蔓状血管瘤的诊断

目的探讨彩色多普勒超声及多普勒能量图在诊断蔓状血管瘤中的应用价值。方法对27例软组织不同部位的蔓状血管瘤行二维、彩色多普勒血流检查及多普勒能量图分析。结果蔓状血管瘤二维形态表现为呈梭形或长条状,内为网格或蜂窝样低或无回声区。相互交通。CDFI:内充满闪烁明亮的红蓝相间的彩流,或以低速静脉血流为主,或以高速低阻型动脉血流信号为主。加用能量图见血流信号极其丰富,连续性好,形成血管树样网状结构分布。乏氏试验,加压或体位改变后其大小形态及血流状态随之发生变化。结论彩色多普勒超声及能量图对蔓状血管瘤的诊断具有重要的临床应用价值。     

基于生物力学性能的血管内支架弧梁单元结构优化设计

背景:在扩张置入体内支撑血管的过程中血管内支架的结构需具备多种生物力学性能,支架结构可以通过综合多目标优化达到其整体性能的最佳状况.目的:鉴于国内外的血管内支架结构设计,提取支架结构特征参数,进行生物力学指标的综合多目标优序分析.方法:基于金属覆盖率、扩张最大支架内应力、最大扩张支架半径、轴向回缩率、径向回缩率等5种生物力学性能的分析,使用ADINA有限元软件建立了81种不同周向单元数、梁宽和单元轴长的支架闭口、平行和开口弧梁单元结构,并使用无量纲化和多目标优序法分析支架性能.结果与结论:结果显示,可设计以单元轴长较大的闭口和平行弧梁单元为主、具有较小的均匀弧梁宽度的闭口、平行和开口弧梁混合单元结构.实验结果对血管内支架的结构设计和力学性能评价体系具有重要的指导意义.     

诊断超声联合微泡开放体外血脑屏障的机理研究

目的 建立体外血脑屏障(blood brain barrier,BBB) 模型,探讨诊断超声联合造影剂(微泡)可逆性开放血脑屏障的机理.方法 BALB/c小鼠脑微血管内皮细胞(brain microvascular endothelial cells,BMVEC) 建立BBB体外实验模型.选择青壮年标本颞骨片,大小1.5 cm×2.0 cm,置于细胞小室上,模拟经颅骨超声声窗条件,根据分组在模型中加入自制的脂膜氟烷超声造影剂(微泡),采用经头颅超声诊断仪辐照,辐照10 min.分为4组,每组4个样本:(1)对照组;(2)超声组;(3)微泡组;(4)超声联合微泡组.经上述处理后,光镜和电镜观察BBB细胞膜及超微结构改变,在不同的时间点检测跨内皮细胞电阻(transendothelial electrical resistance,TEER)和辣根过氧化物酶(horseradish peroxidase,HRP) 的通透性,探讨可逆开放BBB的机理.结果 光镜和扫描电镜显示实验后4组样本细胞表面无明显形态学改变和损伤,透射电镜证实超声联合微泡组辐照后细胞间紧密连接向桥粒连接过渡,超声组紧密连接减少,但没有明显连接分离现象; HRP通透率检测显示超声联合微泡组辐照后细胞通透率呈波浪形增加,18 h后完全恢复,超声组辐照后BBB通透率增加,于30 min内恢复,通透率最高时跨细胞电阻抗(TEER)降低至(179±8) Ω/cm2,随着HRP通透率的减低,TEER逐渐恢复;电镜、HRP通透率在微泡组和对照组没有明显改变.结论 微泡联合诊断超声波能通过短暂开放紧密连接,降低细胞间电阻,提高通透率,达到可逆性开放血脑屏障.     

组织工程小血管支架移植于异种动物的血流和管壁变化

背景:脱细胞的异种小血管支架已被初步去除引起排斥反应的异种抗原.目的:将脱细胞的Wistar大鼠尾动脉支架移植于日本大耳白兔耳血管间,观察移植后血流和管壁变化.方法:15只Wistar大鼠每只取2条长2.50 cm的尾动脉干共30条作为异种小血管,15条直接作为供体尾动脉干,另15条经1%聚乙二醇辛基苯基醚脱细胞处理作供体组织工程小血管支架.受体为15只日本大耳白兔左右耳背面中央动脉.在外科显微镜下,兔中央动脉近侧断端采用全层套叠吻合法套入供体血管近侧腔内,远侧断端按常规端端吻合.采用勒通试验法和常规血管管腔血液、管壁染色法,连续观察血管内血流状况.结果与结论:血管移植后的即刻通畅率达100%.异种小血管支架血液通畅最长时间为46 h 47 min,长于异种小血管移植(14 h),两组远侧的端端吻合区首先出现血流不畅;套叠区小血管支架与中央动脉外膜间由蒂状结缔组织相连.第10天,小血管支架可见内膜纤维组织仍然呈梳头状整齐排列,未见细胞附着;在术后第100天,仍保留着血管支架的完整性.结果提示,脱细胞异种小血管支架可作为血管移植物吻合于动物宿主内,异种小血管支架移植的套叠式吻合法优于经典的端端吻合法.     

逆向工程法建立下颌第一磨牙种植体有限元模型

背景:逆向工程建模在以往的研究中也较多采用,但针对种植方面建模的研究却鲜见,尤其下颌磨牙种植方面的研究更为少见.而下颌磨牙是牙列中缺失率最高的,所以利用逆向工程建立含下颌磨牙种植义齿的颌骨三维有限元模型,对下颌磨牙种植修复的研究具有参考价值.目的:利用逆向工程快速建立含下颌磨牙种植义齿的颌骨三维有限元模型,为口腔生物力学的研究提供数学模型基础.方法:通过螺旋CT扫描正常下颌骨,Mimics软件读取断层影像数据、数据分割、三维重建,应用Magics软件优化网格设计,Pro/E软件前处理实体模型,SolidWorks2007软件建立三维有限元模型并划分网格、求解.结果与结论:成功地重建了正常牙槽骨高度的下颌第一磨牙种植体三维有限元模型,与实体模型具有高度的几何相似性,力学性质、网格质量较好,模型可以根据需要进行简便易行的修改.可为研究不同种植设计方式修复下颌第一磨牙种植体周围骨的应力分析,提供极好的模型支持.     

药物洗脱支架晚期管腔丢失与冠状动脉再狭窄的关系

在冠状动脉支架植入成功后,有许多方法用来评价再狭窄,如通过定量测量管腔的狭窄程度或是长期临床失败的发生率.冠状动脉支架植入后的再狭窄率因受到多种已知和未知因素的影响而差异很大.有研究报道,金属裸支架的临床再狭窄率小于5%,与药物洗脱支架相同.这一结果不是因为支架本身有降低再狭窄的作用,而是由于入选患者多为再狭窄的低危患者.当在危险因素更广范围的人群内进行研究时,同一支架的再狭窄率的差异甚至可达4倍以上.因此,临床再狭窄率并不能客观地对不同随机试验和观察研究中所应用的支架进行评价[1].由于以上原因,有研究者提出了晚期管腔丢失的概念.现就药物洗脱支架晚期管腔丢失与冠状动脉再狭窄的关系作一简要综述.     

Evaluation of flow velocities after carotid artery stenting through split spectrum Doppler optical coherence tomography and computational fluid dynamics modeling

Hemodynamics plays a critical role in the development of atherosclerosis, specifically in regions of curved vasculature such as bifurcations exhibiting irregular blood flow profiles. Carotid atherosclerotic disease can be intervened by stent implantation, but this may result in greater alterations to local blood flow and consequently further complications. This study demonstrates the use of a variant of Doppler optical coherence tomography (DOCT) known as split spectrum DOCT (ssDOCT) to evaluate hemodynamic patterns both before and after stent implantation in the bifurcation junction in the internal carotid artery (ICA). Computational fluid dynamics (CFD) models were constructed to simulate blood velocity profiles and compared to the findings achieved through ssDOCT images. Both methods demonstrated noticeable alterations in hemodynamic patterns following stent implantation, with features such as slow velocity regions at the neck of the bifurcation and recirculation zones at the stent struts. Strong correlation between CFD models and ssDOCT images demonstrate the potential of ssDOCT imaging in the optimization of stent implantation in the clinical setting.OCIS codes: (170.4500) Optical coherence tomography, (170.3880) Medical and biological imaging, (120.5050) Phase measurement     

In vitro validation of Doppler indices using blood and water

Using an in vitro flow model, volume flow and pressure were measured to compare calculated resistance with simultaneously measured continuous-wave Doppler indices during imposed changes in downstream resistance to pulsatile flow. With stepwise reductions in flow, the peak (S) and trough (D) points of the maximum shifted-frequency envelope fell in parallel in a linear fashion until D reached zero. Pressure remained constant, and the pressure waveform remained unchanged. As calculated resistance increased, resistance index (RI) and pulsatility index (PI) both increased in a linear fashion until the point at which D became zero. However, S/D ratio was not linear, and the slope increased as resistance increased. The results obtained from microspheres suspended in water and with heparinized sheep's blood were similar. The results indicate that, with reductions in flow at constant pressure in vitro, S/D ratio does not relate to calculated resistance in the same linear manner as PI and RI.     

数值模拟技术预测颈动脉支架植入术治疗颈动脉重度狭窄效果

目的 观察以数值模拟技术预测颈动脉支架植入术（CAS）治疗颈动脉重度狭窄效果的价值。方法 采用Mimics和Geomagic软件对1例因右侧颈内动脉重度狭窄拟行颈内动脉支架植入术的女性患者的CT血管成像（CTA）DICOM格式数据进行三维重建,获得颈动脉狭窄三维模型;再以Solidworks软件模拟CAS,获得术后颈动脉三维模型;最后以ANSYS FLUENT软件计算模型血流动力学,获得相关血流动力学参数,评估模拟CAS的治疗效果。结果 模拟CAS前,颈动脉狭窄处血流速度及壁面切应力较高而壁面压力较低,且存在二次流、涡流、回流及流动分离;颈动脉整体壁面切应力及壁面压力分布不均;颈内、颈外动脉血流灌注比为0.34,颈内、颈总动脉血流灌注比为0.25。模拟CAS后,该处血流速度及壁面切应力均降低,壁面压力升高,且二次流、回流、涡流及流动分离基本消失;颈动脉整体壁面切应力及壁面压力分布较均匀;颈内、颈外动脉血流灌注比为0.63,颈内、颈总动脉血流灌注比为0.62。结论 采用数值模拟技术可于CAS前有效预测其治疗重度颈动脉狭窄的疗效。     

Reproducibility of the Carpet View system: a novel technical solution for display and off line analysis of OCT images

The optical coherence tomography (OCT) evaluation of the stent anatomy requires the inspection of sequential cross section (CS). However stent coils cannot be appreciated in the conventional format as the OCT CS simply display stent struts, that are poorly representative of the stent architecture. The aim of the present study was to validate a new software (Carpet View), which unfolds the stented segment, reconstructing it as an open structure and displaying the stent meshwork. 21 patients were studied with frequency domain OCT after the deployment of different stents: seven bio-absorbable scaffolds (Dream), seven bare metal stent (Vision/Multilink8), seven drug eluting stent (Cre8). Conventional CS reconstructions were post-processed with the Carpet View software and analyzed by the same reader twice (intra-observer variability) and by two different readers (inter-observer variability). A small average difference in the number of all struts was obtained with the two methods (conventional vs carpet view reconstruction). Using the carpet view, high intra-observer and inter-observer correlations were found for the number of struts obtained in each coil. The Pearson correlation values were 0.98 (p = 0.0001) and 0.96 (p = 0.0001) respectively. The same number of coils was found when analyses were repeated by the same reader or by a different reader whilst mild differences in the count of stent junctions were reported. The Carpet View can be used to address the stent geometry with high reproducibility. This approach enables the matching of the same stent portion during serial time points and promises to improve the stent assessment.     

Regional atrial blood flow in dogs. Effect of hypertrophy on coronary flow reserve.

Little is known regarding regional atrial blood flow responses during varying hemodynamic states in both the normal and hypertrophied atria. This study was undertaken to develop a canine model of chronic atrial hypertrophy and to define in both this group and in normal dogs the regional blood flow response to acute atrial fibrillation and to measure coronary flow reserve. In the 12 dogs with atrial but not ventricular hypertrophy the mean left and right atrial weights were 75 and 47% respectively greater than in the normal group. Blood flow in the normal dogs was less in the appendage than in the non-appendage region for both atria and increased significantly during atrial fibrillation. Similar findings were noted in the hypertrophy group except that during control conditions the left atrial appendage flow was similar to the nonappendage flow. Minimal vascular resistance for the hypertrophy group, 39 +/- 3 was significantly (P less than 0.05) greater when compared to the normal group 28 +/- 2 mmHg/cm3 per min per g. Thus, significant regional blood flow differences occur in both the normal and hypertrophied atria. In addition, atrial hypertrophy does not alter the autoregulatory capacity to the hemodynamic stress of atrial fibrillation but does reduce coronary flow reserve.     

超声监测跟腱断裂手术治疗后跟腱周长及断端血流动态变化的价值

目的 探讨超声监测跟腱周长及断端血流在跟腱手术治疗后恢复过程中的意义.方法 对31例跟腱断裂修补术后不同时期的患者,超声动态观察跟腱术后断端的血流变化,用轨迹测量法测量健侧和患侧跟腱多点的周长.结果 跟腱断裂后患侧跟腱周长较健侧大(P＜0.05).术后随着修复时间的延长,患侧跟腱周长有逐渐变小的趋势,但仍较同时期健侧跟腱的周长值大.跟腱术后8周,跟腱断端的血流信号由丰富逐渐减少.结论 监测跟腱术后周长及断端血流的变化可以准确跟踪跟腱术后的动态演变过程.     

The relationship of respiratory failure to the oxygen consumption of, lactate production by, and distribution of blood flow among respiratory muscles during increasing inspiratory resistance.

An animal model was developed to determine if blood flow to the respiratory muscles limits oxygen delivery and thus work output during inspiratory resistance. With incremental increases in the rate of work of breathing to 15 times the resting level, blood flow to the diaphragm rose exponentially 26-fold. Blood flow to other inspiratory and a few expiratory muscles increased to a much smaller extent, often only at the greater work loads. Cardiac output and blood pressure did not change. Arterial-venous oxygen content difference across the diaphragm became maximal at low work rates and thereafter all increases in oxygen delivery during higher work rates were accomplished by increments in blood flow. Oxygen consumption of the respiratory musculature calculated by blood flow times oxygen extraction increased exponentially with increasing work of breathing and was less than the increase in total body oxygen consumption at each work load. Hypoxemia and respiratory acidosis occurred when the animals inspired through the highest resistance; blood flow and oxygen consumption were even higher than that observed during previous resistances and there was no evidence of a shift to anaerobic metabolsim in blood lactate and pyruvate levels. Respiratory failure did not appear to be a consequence of insufficient blood flow in this model.     

Acute effects of walking and combined exercise on oxidative stress and vascular function in peripheral artery disease

The aim of this study was to compare the effects of a single session of walking and combined exercise on oxidative stress and vascular function in peripheral arterial disease patients. Thirteen patients with peripheral arterial disease underwent two experimental sessions in random order: walking (ten sets of 2‐min walking at the speed corresponding to the onset of claudication pain with 2‐min interval between sets) and combined exercise (1 × 10 reps in eight resistance exercises plus five‐two‐minute sets of walking). Before and after the exercise, vascular function (blood flow, leg vascular resistance and blood‐flow postreactive hyperaemia) and oxidative stress (malondialdehyde and plasma nitrite levels) were obtained. Blood flow increased similarly after both sessions, whilst leg vascular resistance decreased similarly after both sessions. Plasma nitrite increased only after the combined exercise. Malondialdehyde decreased after both sessions, and the decrease was greater after combined exercise. As a conclusion, a single session of combined exercise improves blood flow and leg vascular resistance similarly to walking session; however, combined exercise promoted better effects on oxidative stress.     

切片厚度伪像造成穿室间隔血流成因的分析

目的 研究切片厚度伪像在超声心动图检查中造成穿宅间隔血流的原因,为避免临床误判或误诊提供临床试验依据.方法 使用不同型号的超声诊断仪对50例无室间隔缺损者行超声心动图检查.观察图像中出现穿室间隔血流的切面观、条件和所使用的仪器之间的关系.结果 8例受检者在使用特定超声诊断仪检查时于胸骨旁四腔观或胸骨旁不规则观可见穿室间隔血流.其余42例在使用不同超声诊断仪检查时均未出现穿室间隔血流.多切面动态扫查结合解剖学分析可推断穿室间隔血流为后房室沟内走行的冠状血管.结论 无室间隔缺损的正常人出现穿室间隔血流伪像足由于冠状血管内的彩色血流信号与窒间隔重叠所致,是切片厚度伪像在心脏超卢的一种表现.