椎动脉狭窄及介入治疗的血流动力学分析

目的研究椎动脉狭窄及介入治疗后血流动力学状态的变化。方法数字减影血管造影(DSA)可为介入治疗提供直接的影像依据,以内蒙古民族大学附属医院1例椎动脉狭窄患者的DSA病例资料为例,利用计算流体力学(CFD)软件FLUENT 6.2.16,在一个心动周期(T)内对椎动脉狭窄介入治疗前后局部血管血流动力学变化情况进行了分析,重点讨论了椎动脉狭窄存在时,t1=0.05T、t2=0.12T、t3=0.21T时刻血液流场状况,比较t3(血流速度峰值)时刻介入治疗前后血液流场及血管壁切应力变化。结果血流速度较小时(t1、t2时刻),由于起始端狭窄存在,椎动脉中血流量不足,影响大脑供血。血流速度较大时(t3时刻),椎动脉入口处血液出现了严重紊流,同样影响大脑供血,并且狭窄处血管壁较大的切应力可能会撕裂血管内膜,加重增生。椎动脉实施支架植入术后,显著改善椎动脉对大脑的供血情况,同时也改善血管壁的应力状况,起到保护血管的作用。结论对椎动脉狭窄的早期诊断和积极有效治疗可以降低卒中发病率。     

颅内动脉瘤夹闭手术的血流动力学数值分析

本文利用计算流体力学(CFD)方法对颅内动脉瘤夹闭手术前后血液流场进行三维数值模拟,根据血流动力学对手术方案的可行性进行预估。采用逆向工程软件Mimics对临床CT图像进行三维数字化重构,结合相关脉动血流量,模拟心动周期不同时刻的血流动力学细节。通过计算得到了模型手术前后在心动周期不同时刻的速度场、壁面剪切应力场、压力场的分布特征,对比分析手术前后分叉处的血流速度、壁面剪切应力、壁面压力变化,结果显示术后的血流速度与壁面剪切力显著提高,而壁面压强则明显降低。     

全方向M型超声成像的研究

本文介绍了一种全方向Ｍ型超声成像方法，使传统的Ｍ型取样线能任意旋转和平移，从而可以测量器官任意部位，任意方向上的运动幅度，速度等参数，文章分析了此方法的误差来源及克服方法。     

活体微血栓形成过程的定量分析

在应用激发光照射荧光物质注射后的微血管来形成活体微血栓模型的基础上,开发了一种计算机图像处理方法,对微血栓形成的动态过程进行了定量的分析。利用这一方法不仅对形成过程中不同时刻微血栓形成的面积大小进行了测定,而且,进一步应用了计算机图像减影技术,将2幅不同时刻的形成过程中的图像相减,求出形成过程中血栓生长的程度和形状的变化。该方法不仅有利于血栓生长机制研究也可用作抗血栓药物的药效评价。     

任意剖面显示算法研究

对三维体数据进行立体显示的基本方式之一是任意剖面显示。但是，现有算法得到的剖面边缘不同程度地有模糊，本文对任意剖面显示过程中象素的重采样，象素的重赋值，以及加权系数的选择三个方面做了理论分析和实验研究，基于上述分析，作者了一种基于边界的选择性邻域体系算法，较好地解决了边缘模糊问题，并对此算法进行了优化，使其速度大大提高，最后对已有的剖面显示算法进行了比较。     

微循环血管网络研究中的一种动态定量测量方法

这里介绍了一种面向血管网络的微循环动态定量研究新方法。在通常的显微电视测量方法中,引入计算机控制的全数字式摄像机,不仅能对任意位置、任意角度及流向的直血管进行跟踪扫描,获得血管管径和血流速度     

一种基于微机的新型Morris水迷宫分析系统

我们设计了一种新型的能够在线和离线分析Morris水迷中过程的图像追踪系统。该系统以电荷耦合器件（CCD）和赛扬400微型计算机为基础，实验过程中不需要对实验动物作特殊标记，识别算法采用了轨迹预测、局部和全局相结合的搜索技术，从而使得追踪和记录实验动物（大鼠）的速度达到18帧／s，空间分辨率达到2cm。该系统提供了丰富的参数，并具有对任意点和任意时间段进行参数分析和轨迹显示的功能。实验结果可以保存为文本文件，方便地利用Excel等工具软件作进一步分析。     

具不同狭窄-吻合口位置关系的冠状动脉搭桥术的血流动力学仿真分析

目的通过有限元仿真探索带有辅助搭桥血管模式的冠状动脉搭桥术中,辅助搭桥管吻合口与冠状动脉狭窄处之间的距离对该吻合口及其下游区域的血流动力学影响,为带有辅助搭桥管的新型冠状动脉搭桥术的临床应用提供理论指导。方法利用有限元分析方法,假定血液为不可压缩牛顿流体,建立3种搭桥血管模型,其冠状动脉上吻合口和狭窄的距离分别为0.0045 m、0.006 m和0.009 m。通过仿真结果考察不同模型中的血流速度、壁面切应力等参数的变化。结果吻合口与狭窄处之间的距离不同,冠状动脉血管内的血流动力学参数也不相同。速度方面,心动周期0.09 s时刻L1.5模型中吻合口足跟处轴向截面的最大速度约为0.54 m/s,同时刻L2和L3模型中其最大速度分别为0.45 m/s和0.37 m/s。壁面切应力方面,0.09 s时刻,L1.5模型中吻合口对应面的血管壁上其流动停滞点距离吻合口足跟仅为0.0024 m,同时刻L2和L3模型中其流动停滞点距离足跟处分别为0.0039 m和0.0068 m,长度明显增加。其他时刻流动停滞点分布有相同趋势。结论在实施冠状动脉搭桥术时,吻合口与狭窄处之间保持较大的距离,有利于改善吻合口处的血流动力学环境,降低吻合口处发生再狭窄的可能性。     

二维脉动流场中内皮细胞表面切应力分布的数值模拟

本文对三种生理相关的正弦入口速度波形的脉动流场内,VEC表面的切应力分布进行了有限差分方法的数值模拟.结果表明(1)脉动流场与稳态流场中内皮细胞表面的流场分布完全不同,脉动流场中内皮细胞表面的切应力变化幅值远大于稳态流场中的值.(2)同一时刻,每个VEC上的切应力分布是不均匀的,细胞形状影响其表面的切应力分布.(3)在脉动周期的不同时刻,细胞表面的切应力分布也是不均匀的,切应力分布随时间的变化波形与入口波形相类似,但相位有所超前.(4)细胞的伸长主要取决于EC表面的最大平均切应力大小.(5)本章的计算结果可以用于对Helmilinger实验现象的解释.     

二维脉动流场中内皮细胞表面切应力分布的数值模拟

本文对三种生理相关的正弦入口速度波形的脉动流场内,VEC表面的切应力分布进行了有限差分方法的数值模拟。结果表明：（1）脉动流场与稳态流场中内皮细胞表面的流场分布完全不同,脉动流场中内皮细胞表面的切应力变化幅度远大于稳态流场中的值。（2）同一时刻,每个VEC上的切应力分布是不均匀的,细胞形状影响其表面的切应力分布。（3）在脉动周期的不同时刻,细胞表面的切应力分布也是不均匀的,切应力分布随时间的变化波形与入口波形相类似,但相位有所超前,（4）细胞的伸长主要取决于EC表面的最大平均应力大小。（5）本章的计算结果可以用于Helmilinger实验现象的解释。     

Flow cytometry

Flow cytometry (FCM) allows the rapid measurement of a variety of physical and biochemical properties of individual cells suspended in a liquid medium. Recent developments now allow FCM to assess cellular properties with a speed and precision unobtainable by any other means. Because of its multiple capabilities, FCM is being used for ever greater numbers of applications, in both basic and applied biology, and its expected soon to be widely used in the clinical laboratory.     

Cerebrospinal Fluid Flow Dynamics in the Central Nervous System

Cine-phase-contrast-MRI was used to measure the three-dimensional cerebrospinal fluid (CSF) flow field inside the central nervous system (CNS) of a healthy subject. Image reconstruction and grid generation tools were then used to develop a three-dimensional fluid–structure interaction model of the CSF flow inside the CNS. The CSF spaces were discretized using the finite-element method and the constitutive equations for fluid and solid motion solved in ADINA-FSI 8.6. Model predictions of CSF velocity magnitude and stroke volume were found to be in excellent agreement with the experimental data. CSF pressure gradients and amplitudes were computed in all regions of the CNS. The computed pressure gradients and amplitudes closely match values obtained clinically. The highest pressure amplitude of 77 Pa was predicted to occur in the lateral ventricles. The pressure gradient between the lateral ventricles and the lumbar region of the spinal canal did not exceed 132 Pa (~1 mmHg) at any time during the cardiac cycle. The pressure wave speed in the spinal canal was predicted and found to agree closely with values previously reported in the literature. Finally, the forward and backward motion of the CSF in the ventricles was visualized, revealing the complex mixing patterns in the CSF spaces. The mathematical model presented in this article is a prerequisite for developing a mechanistic understanding of the relationships among vasculature pulsations, CSF flow, and CSF pressure waves in the CNS.     

Tools for Managing Image Flow in the Modality to Clinical-Image-Review Chain

Web-based clinical-image viewing is commonplace in large medical centers. As demands for product and performance escalate, physicians, sold on the concept of any image, anytime, anywhere, fret when image studies cannot be viewed in a time frame to which they are accustomed. Image delivery pathways in large medical centers are oftentimes complicated by multiple networks, multiple picture archiving and communication systems (PACS), and multiple groups responsible for image acquisition and delivery to multiple destinations. When studies are delayed, it may be difficult to rapidly pinpoint bottlenecks. Described here are the tools used to monitor likely failure points in our modality to clinical-image-viewing chain and tools for reporting volume and throughput trends. Though perhaps unique to our environment, we believe that tools of this type are essential for understanding and monitoring image-study flow, re-configuring resources to achieve better throughput, and planning for anticipated growth. Without such tools, quality clinical-image delivery may not be what it should.     

流式细胞术定量检测细胞凋亡

本文报道了几种药物处理人体外周血细胞后，用双染色法在流式细胞仪检测凋亡细胞的发生。将凋亡细胞分选出用琼脂糖核酸电泳ＤＮＡ分析，证实了流式细胞仪所测定的结果。比较了单染色法检测凋亡细胞的局限性．     

Flow rate dependence of in vitro removal of anti-A and anti-B antibodies by immunoadsorbents with synthetic oligosaccharides representing blood group substances

In vitro removal of anti-A and anti-B antibodies by immunoadsorbents with synthetic oligosaccharide structures representing blood group substances have been studied under controlled and simulated extracorporeal perfusion conditions at different flow rates ranging from 20 to 160 mL/min. There is a gradual decline in antibody titers in the plasma, as it relates to the antibody binding capacity and efficiency of the immunoadsorbents, both as a function of time and plasma volume at any of the flow rates employed. Approximately the same maximal binding capacity is achieved in about 4 hours of perfusion regardless of the flow rate, whereas increased number of plasma volumes are required at higher flow rates to compensate for the appropriate residence times needed in the column to utilize the same capacity. The perfusion time alone appears to be a critical factor which via the flow rate determines the residence time between the plasma and the immobilized hapten in the column. Also, the optimal flow rate at which maximum binding capacity of the immunoadsorbent may be utilized efficiently appears to fall within a range of the flow rate. The factors determining this range and the efficiency of the immunoadsorbents under dynamic conditions are discussed. The results obtained under the controlled conditions and the discussions that follow are expected to be generally useful, at least, as approximate clinical guidelines, for selective removal of specific substances by extracorporeal perfusion techniques utilizing therapeutic intervention with immunoadsorbents in this important area of medical therapy.     

Flow cytometric analysis of bromodeoxyuridine-induced micronuclei

The effects of DNA substitution by the thymidine analogue 5-bromodeoxyuridine(BrdU) on cell cycle progression and micronucleus inductionwere studied in different mammalian cell cultures. Simultaneousflow cytometric measurements of DNA content and side scatterof nuclei in Chinese hamster embryo (CHE) cells revealed a concentration-dependenttemporary block in the G₂/M phase of the first cell cycle. NTH3T3 cells and human amniotic fluid fibroblast-like cells, onthe contrary, did not show any cell cycle disturbances in thepresence of BrdU. Micronucleus frequency increased as soon asCHE cells started to divide and reached a plateau when all cellshave divided. The height of this plateau was almost equal for60 and 100 µM BrdU. This saturation of micronucleus inductionwas due to a saturation of BrdU incorporation into DNA alreadyat a dosis of 60 µM as shown by the BrdU/Hoechst quenchingtechnique. Indirect immunofluorescent staining of kinetochoreswith CREST antibodies revealed that nearly all BrdU-inducedmicronuclei were kinetochore-negative suggesting the presenceof acentric chromosome fragments in these micronuclei. DNA distributionsof micronuclei measured by flow cytometry showed several peaksrepresenting micronuclei which contain DNA fragments of definedsizes induced by non-random breakage of chromosomes 1 and Xas verified by flow karyotyping and C-banding.     

Endothelialization and Flow Conditioning of Fibrin-Based Media-Equivalents

It is generally accepted that endothelialization and subsequent development of a functional endothelium are of paramount importance to the success of any bioartificial artery. In this study, we aimed to assess the ability of smooth muscle cell-remodeled, fibrin-based media-equivalents (MEs) to be endothelialized, examine the morphological changes of endothelial cells (ECs) associated with exposure to physiologically-relevant shear stress in a custom-built bioreactor, and determine if adherent ECs are capable of withstanding average physiological shear stresses. It was found that MEs could be readily endothelialized with surface coverages of 98.8 ± 0.9% after two days, and the ECs expressed von Willebrand factor. Furthermore, EC retention remained high (steady: 96.5 ± 4.4%, pulsatile: 94.3 ± 4.3%) under exposure to physiologically relevant shear stresses for 48 h. The results indicate that these MEs are conducive to generating an EC monolayer, with the ECs possessing adhesion strength sufficient to withstand physiological shear stress and maintain a normal phenotype.     

Describing the Highly Three Dimensional Right Ventricle Flow

Visualization of the three-dimensional flow within the Right Ventricle (RV) is a challenging issue due to the fully three-dimensional geometry of the ventricular cavity. To date proper characterization and quantification of the RV flow still remains incomplete, and techniques that can be easily applied to current medical imaging are scarce. A method for simulating the highly complex, multi directional flow within the RV is presented by coupling 4D echocardiography imaging with numerical simulations based on the Immersed Boundaries Method (IBM). A novel formulation for accurately computing the space-time distribution of the blood residence time inside the cavity is introduced. Results showed an initial compact vortex forming past the tricuspid orifice at early diastole that quickly breaks into a weakly turbulent flow pattern and rearranges, during systole, into a peculiar stream-wise vortex spinning out towards the pulmonary orifice. This arrangement is maintained when the Ejection Fraction (EF) is reduced from 58 to 32%. The average blood transit time is found to scale almost inversely proportional to the EF. A careful analysis of the residence time permitted to assess the relative significance of the different flow components (from the direct flow, with a residence time less than one heartbeat, to the residual volume, that stagnates in the ventricle) and their distribution in space.     

高通滤波器对多普勒血流信号的影响

在绝大多数连波多普勒血流测量系统中，通常采用一个高通滤波器来滤除由固定目标和血管壁产生的强反射信号。本文从理论上推导出引入高通滤波器会导致血流平均速率估值偏高。     

Flow measurements with a high-speed computed tomography scanner

A high-speed computed tomography (CT) scanner with a scan time of 50 ms was used to measure flow in a phantom constructed to simulate both tissue and vessels. After a bolus injection of iodinated contrast medium, the phantom was scanned at a rate of up to 2 images/s. A gamma-variate curve was fit to the time-density data obtained from the inlet and outlet, as well as from the tissue-equivalent part of the phantom. Flow was then calculated using different curves and curve parameters according to the Stewart-Hamilton equation, the mean transit time, and a modification of the Sapirstein principle. Actual flow rates were assessed by timed sampling. The results demonstrated that high-speed CT can measure flow accurately by all these methods. Application of high-speed CT for flow measurements in experimental animals and patients is, therefore, promising. The limitations of each technique for clinical application are discussed.