肝内胆管树形态学定量研究

在Ｓｔｒａｈｌｅｒ分级法的基础上，以狗胆道系统的灌注模型为材料，测量了胆管树上８个级别的分支的几何参数：分支数Ｎｎ、分支直径Ｄｎ及分支长度Ｌｎｏ分析计算发现：Ｎｎ、Ｄｎ和Ｌｎ与级别数ｎ之间均可用指数函数来描述。随后的分析引入分形几何的概念，认为胆管树是一种分形结构，其显著特征是在不同尺度下所表现出来的自相似性。根据分形理论，利用上述得到的几何参数变化规律，估算出了狗胆管树的分维数Ｄ。     

人体肺支气管树内的气流分布研究

在 Weible的人体肺支气管树统计数据的基础上 ,参照肺解剖图形 ,运用流体网络理论建立支气管树在前 5～ 7级为不对称分叉 ,后面的分级为对称分叉的三参数集中参数模型。采用 GEAR算法求解常微分方程组 ,探讨在正常呼吸过程中气体在肺支气管树内不同分段的压力流量分布。在此基础上探讨了支气管局部受阻时 ,肺支气管树内不同部位的压力和流量的分布状况 ,并进行了比较。该模型对认识肺支气管树在生理、病理状态下的气流分布有重要意义     

根据语音分形维和基音周期的说话人性别识别研究

根据语音特征实现说话人性别的自动识别,在音频处理与分析中具有重要的应用意义.为了克服语音常规线性参数在刻画说话人性别特征上的不足,本文使用了分形维等非线性参数作为特征空间的有效补偿.首先利用提升算法实现基音周期的提取;然后提取语音的分形维数;最后根据Takens定理,对分形维进行了重构,采用求近似熵的方法得到分形维复杂度.将基音周期、分形维数以及分形维复杂度构成三维向量,进行说话人的性别识别.实验证明,通过非线性参数的介入,与仅使用基音周期等传统线性特征的识别方法相比,识别系统的准确率和稳定性得到有效提高,因此为说话人性别识别提供了一个新的思路.     

分维(Fractaldimension)测试软件系统及其应用

分形几何（Fractalgeometry）是研究分形的非线性学科，近年已应用于生物医学领域。医学图像因其形态特殊，分维测试相当复杂，故我们研制开发了一套分维测试软件系统，已在分形应用研究中使用。简介如下：本软件系统利用MAS—l图像分析系统进行图像采集及分割，建立图像数据库。系统包括三大功能模块。（l）几何形态参数的分维测试：该模块根据分支系统的几何形态参数，利用“近似法”和welson’s法计算整个分支系统及其各级分支的分维。（2）图像的分维测试：包括图像信息处理、图像裁剪、图像特征提取、盒子法（BOX一CountinsMethod）分维m4试四个子模块。该模块的主要功能是通过对图像信息的处理、分析，求解其盒维数，并对盒子法的原理用＆。一方格覆盖图演示。拥有矩形、圆形和任意框三种图像裁剪方法。系统提供了由灰度差值提取及填充的血管树纹理提取方法。系统提供了单图、汇总图、平均图及统图四种盒维数结果显示方法。（3）分形的计算机模拟：系统根据Nelson模型，用“黑色区域的轮廓线抽出”算法行边沿提取，用速归算法实现了器官血管树分形的计算机模拟，并计算其长度分维。软件采用BorlandC“”为开发语言，系统在IBM－PC兼容机系列、中文Windows（3．1以上）环境运行，支持键盘和鼠标，     

基于中国数字化人体的支气管树三维模型构建及纤维支气管镜手术模拟仿真

目的 构建人体肺支气管树详细的三维数字化结构,并进行虚拟仿真和3D打印,为纤维支气管镜手术虚拟仿真提供精准的形态学资料。方法 选择中国数字化人体CVH1,2,5,6胸部的断层解剖图像,使用AMIRA软件对肺和支气管树进行分割并三维重建,使用Cinema 4D软件平滑,构建交互式3DPDF模型,并进行3D打印,创建虚拟纤维支气管镜手术仿真模型。结果 我们构建了4例详细的肺支气管树三维数字化模型,包括3例成人,1例儿童,展示了人体支气管树3～6级分支,4级与6级分支数都为上一级分支数两倍左右,左肺段支气管为8段,6级支气管分支数为63.8±3.6,右肺段支气管为10段,6级支气管分支数为63.8±3.6,左右肺6级支气管数比为0.79。支气管最长长度均位于左叶,儿童管腔直径均小于3例成人的管腔直径。结论 支气管树的三维数字化模型、3D打印模型、3D-PDF和手术虚拟仿真软件,提高了对支气管树解剖学和发育生物学的认识。我们认为,左肺的B¹⁺²和B⁷⁺⁸段支气管为单独的段支气管,而不是两段合并的段支气管,此研究为临床解剖学教学和纤维支气管镜手术虚拟仿...     

基因组序列CGR图形表示的多重分形分析

为了更好地描述基因组序列CGR(chaos-game representation)图形的分形特征,引入多重分形理论进行分析。通过研究3种概率集对标度不变性范围的影响,选取出标度不变性最好的概率集,计算光滑的广义维数谱和多重分形谱。结果表明:以相对概率组成概率集时标度不变性最好,而且标度不变性随尺度变化可被分为3个不同的区域,这反映了基因组序列不同长度的序列片段有不同的分布规律。可见,多重分形方法可以用于描述基因组序列CGR图形的分形特征。     

人工关节磨损颗粒的分形表征及分类特征分析

目的研究膝关节模拟实验条件下超高分子量聚乙烯(UHMWPE)磨损颗粒的形态及分形表征,对磨损颗粒进行分类特征分析,探讨分形维数与磨损状态的相关性。方法采用膝关节模拟器以实现模拟膝关节磨损运动,股骨、衬垫分别选用医用锻造CoCrMo合金和UHMWPE。磨损颗粒提取依据标准ISO 17853进行,利用磨粒轮廓自动提取与分形识别系统对磨损颗粒进行分形分析,采用网格划分、聚类分析和遗传模拟退火算法3种模型对磨粒进行分类识别。结果 UHMWPE单体磨粒的分形特征明显,尺寸较大的条形磨屑过渡到尺寸较小的类球形磨粒时,雷达分形维数不断减小,球状磨粒的分形维数D接近0。遗传模拟退火算法模型磨粒群体分类划分的分形维数内加权误差平方和最小,聚类特征明显。当磨损运行周期较低时,分形维数较大的条状、针叶状和纤维状磨粒占比较大,磨损以犁沟和剥落磨损为主;随磨损周期的延长,大分形维数磨粒占比下降,低分形维数的片状、块状和类球状磨粒占比上升,磨损向疲劳磨损和黏着磨损转变,磨损状态过渡到复合磨损期。当进入稳定磨损期后,各类形态磨粒的占比例变化不大。由于小尺寸磨粒的数量增加,群体分形维数有所减小。结论以改进雷达图分形方法为基础的磨粒轮廓自动提取与分形识别系统,可用于人工关节磨损颗粒的形态轮廓提取、分形维数计算和参数统计,为人工关节磨粒的识别和诊断提供新的数字化分析工具。     

肺癌分形维数特征的研究

目的:探索肺癌图像的纹理分形维数特征.材料与方法:选取得到病理证实的180例病变组织(良性或恶性),在小扫描野高分辨率条件下获取CT图像电子数据,应用盒维数方法计算病变组织纹理的分维数值.结果:良性病变组织分维数值大约在2.35左右,恶性病变其分维数值在2.50以上.结论:分维数值从某种意义上揭示了组织的纹理特征信息,有望通过CT图像的纹理分形维数的分析对肺癌的诊断提供依据.     

右肺肺段和亚肺段支气管和血管的矢状断层解剖学研究

目的：研究右肺肺段和亚肺段支气管和血管在矢状断面上的配布规律.方法：利用15例胸部连续矢状断层标本和2例多层螺旋CT图像,追踪观察了右肺肺段和亚肺段支气管和血管,并据此寻找在矢状断面上划分右肺肺段的方法.结果：在右主支气管杈层面上,右肺上叶动脉发出尖段动脉和前段动脉,右肺下叶支气管向后发出上段支气管、向下发出内侧底段支气管.在叶间动脉层面上,右肺上叶支气管发出尖、后、前段支气管,基底干支气管发出前、外侧和后底段支气管.在叶间动脉分叉层面上,后段静脉居前、后段支气管之间,尖段静脉与前段静脉合成尖前静脉,中叶支气管分为外、内侧段支气管,下叶动脉发出的段级动脉居相应支气管的上方.在右心房右侧第二层面上,右肺上、中叶的支气管和血管已为亚段级,在右肺下叶内,肺段支气管居中,其上、下方分别为相应的肺动脉和肺静脉.结论：在矢状断面上,右侧肺段内支气管和血管相对集中,且容易显示其发出处和长轴,故矢状断面是显示右肺肺段和亚肺段支气管和血管的优势断面.     

基于电网络模型的动脉树输入阻抗递归计算及参数分析

目的 通过提出一种计算人体动脉树输入阻抗的递归算法,分析动脉树各参数对输入阻抗的影响,为动脉树生理和病理变化分析提供参考。方法 利用由大动脉和主要外周动脉构成的55段人体动脉树建立分布式电网络模型,通过设定电网络模型外周阻力,建立动脉树单向数据链表,采用递归算法计算动脉树升主动脉的输入阻抗。在此基础上比较不同动脉顺应性、外周阻力和动脉长度、内径、壁厚等参数对输入阻抗的影响。结果 计算结果与实验数据和其他模型结果相一致,验证了该方法的有效性。不同参数对动脉树输入阻抗的影响有较大差异且呈现各自特征。结论 输入阻抗能有效地反映动脉树血液动力学参数的变化情况,是人体动脉树生理病理诊断的重要参考。     

Generation of an Anatomically Based Three-Dimensional Model of the Conducting Airways

An anatomically accurate model of the conducting airways is essential for adequately simulating gas mixing, particle deposition, heat and water transfer, and fluid distribution. We have extended a two-dimensional tree-growing algorithm to three dimensions for generation of a host-shape dependent three-dimensional conducting airway model. Terminal branches in the model are both length limited and volume-supplied limited. A limit is imposed on the maximum possible branch angle between a daughter and parent branch. Comparison of the resulting model with morphometric data shows that the algorithm produces branching and length ratios, path lengths, numbers of branches, and branching angles very close to those from the experimental data. The correlation between statistics from the generated model and those from morphometric studies suggests that the conducting airway structure can be described adequately using a supply and demand algorithm. The resulting model is a computational mesh that can be used for simulating transport phenomena. © 2000 Biomedical Engineering Society. PAC00: 8719Uv, 8710+e     

Generation of an Anatomically Based Geometric Coronary Model

A discrete anatomically accurate finite element model of the largest six generations of the coronary arterial network is developed. Using a previously developed anatomically accurate model of ventricular geometry the boundaries of the coronary mesh are defined from measured epicardial coronaries. Network topology is then generated stochastically from published anatomical data. Spatial information is added to this topological data using an avoidance algorithm accounting for global network geometry and optimal local branch angle properties. The generated vessel lengths, radii and connectivity are consistent with the published studies and a relativity even spatial distribution of vessels within the ventricular mesh is achieved. The local finite element coordinates of the coronary nodes within the ventricular mesh are calculated such that the coronary geometry can be recalculated within a deformed ventricular mesh. © 2000 Biomedical Engineering Society. PAC00: 8710+e, 8718Bb, 0270Dh     

Two-dimensional finite element model for oxygen transfer in cross-flow hollow fiber membrane artificial lungs.

A predictive, two-dimensional model with good absolute accuracy for flow and mass transfer in cross-flow hollow fiber membrane artificial lungs is developed. The proposed model is able to predict the gas transfer to water flowing outside and perpendicular to hollow fibers in the artificial lung. The model uses a finite element technique to solve the Navier-Stokes equations and the convection-diffusion equation on the computational domain of a unit fiber cell. Subsequent stream-wise and cross-wise unit fiber cells are then coupled/assembled to the relationship between the oxygen transfer rate and flow rate of a cross-flow hollow fiber membrane artificial lung. The model is compared to experimental water data obtained by perfusing three commercial artificial lungs with water.     

Study of the three-dimensional geometry of the central conducting airways in man using computed tomographic (CT) images

Clinical research on the deposition of inhaled substances (e.g. inhaled medications, airborne contaminants, fumes) in the lungs necessitates anatomical models of the airways. Current conducting airway models lack three‐dimensional (3D) reality as little information is available in the literature on the distribution of the airways in space. This is a limitation to the assessment or predictions of the particle deposition in relation to the subject’s anatomy. Detailed information on the full topology and morphology of the airways is thus required to model the airway tree realistically. This paper presents the length, diameter, gravity, coronal and sagittal angles that together describe completely the airways in 3D space. The angle at which the airways branch out from their parent (branching angle) and the rotation angle between successive bifurcation planes are also included. These data are from the study of two sets of airways computed tomography (CT) images. One CT scan was performed on a human tracheobronchial tree cast and the other on a healthy male volunteer. The airways in the first nine generations of the cast and in the first six conducting generations of the volunteer were measured using a computer‐based algorithm. The data contribute to the knowledge of the lung anatomy. In particular, the spatial structure of the airways is shown to be strongly defined by the central airways with clear angular lobar patterns. Such patterns tend to disappear with a mean gravity, coronal and sagittal angles of 90° in each generation higher than 13–15. The mean branching angle per generation appears independent of the lobe to which the airways belong. Non‐planar geometry at bifurcation is observed with the mean (± SD) bifurcation plane rotation angle of 79 ± 41° (n = 229). This angle appears constant over the generations studied. The data are useful for improving the 3D realism of the conducting airway structure modelling as well as for studying aerosol deposition, flow and biological significance of non‐planar airway trees using analytical and computational flow dynamics modelling.     

肺内支气管动脉分布的应用解剖

目的：为选择性支气管动脉造影提供解剖学依据。方法：选用40例肺血管灌注标本和8例肺腐蚀铸型标本进行观测。结果：40侧成人肺标本中．共有59支支气管动脉,左肺l～3支．右肺为1-2支。支气管动脉分为3型．左肺2支型最多．右肺1支型最多。肺门支气管动脉平均外径．右肺1支型口径显著大于2支型．左肺各型口径无显著性差别。支气管动脉进入肺门后,一支动脉分布到几个肺叶者：左侧占72．7％,右侧占92．3％．专入某一肺叶者：左侧占27．3％,右侧占7．7％。肺叶支气管动脉和肺段支气管动脉均以2支最常见。结论：对于肺内支气管动脉的去向应引起重视。     

A pore transport model for pulmonary alveolar epithelium

Hydrodynamic heteropore flow models for transport of solutes across alveolar epithelial tissue have been developed. A two-size cylindrical pore model and a similar parallel-plate model were formulated, tested and used to predict effective pore sizes from literature data on transport in bullfrog, canine and rat lungs. The best fit equivalent pore-size estimates were obtained using a modified, nonlinear least squares procedure, with alveolar surface area to volume ratio (S/V) and small-pore area fraction of total pore area as parameters. Small-pore and large-pore width estimates of 4 nm (84% of total flow area) and 10 nm, respectively, with an average deviation of 20% from experimentally derived permeabilities were obtained from the bullfrog alveolar epithelium parallel-plate pore model (13 solutes, diameters 0.3 to 2.8 nm). The equivalent cylindrical pore model diameter estimates were 5 nm and 10 nm, with small-pore area fraction and percentage deviations similar to the parallel-plate model estimates. Eighty-eight percent of the bulk water driven by a sucrose osmotic gradient was predicted to be transported through the small pores. The rat alveolus parallel-plate pore model (6 solutes) yielded small-pore and large-pore widths of 0.4 nm and 50 nm, respectively. Clearance rate-constant data for dextran macromolecules (3,000 to 250,000 Daltons), using a single parallel-plate pore model, resulted in a pore width estimate of 98 nm for canine alveoli with an average deviation of the predicted rate constants of 18% from literature experimental values. In all cases tested, the parallel-plate pore model predicted lower small-pore size estimates than did the cylindrical pore model, and both models had appreciably smaller percentage deviations from experimental data than previous models.     

Bronchial tree of the human embryo: Examination based on a mammalian model

The symmetry of the right and left bronchi, proposed in a previous comparative anatomical study as the basic model of the mammalian bronchial tree, was examined to determine if it applied to the embryonic human bronchial tree. Imaging data of 41 human embryo specimens at Carnegie stages (CS) 16–23 (equivalent to 6–8 weeks after fertilization) belonging to the Kyoto collection were obtained using phase-contrast X-ray computed tomography. Three-dimensional bronchial trees were then reconstructed from these images. Bronchi branching from both main bronchi were labeled as dorsal, ventral, medial, or lateral systems based on the branching position with numbering starting cranially. The length from the tracheal bifurcation to the branching point of the labeled bronchus was measured, and the right-to-left ratio of the same labeled bronchus in both lungs was calculated. In both lungs, the human embryonic bronchial tree showed symmetry with an alternating pattern of dorsal and lateral systems up to segmental bronchus B9 as the basic shape, with a more peripheral variation. This pattern is similar to that described in adult human lungs. Bronchial length increased with the CS in all labeled bronchi, whereas the right-to-left ratio was constant at approximately 1.0. The data demonstrated that the prototype of the human adult bronchial branching structure is formed and maintained in the embryonic stage. The morphology and branching position of all lobar bronchi and B6, B8, B9, and the subsegmental bronchus of B10 may be genetically determined. On the other hand, no common structures between individual embryos were found in the peripheral branches after the subsegmental bronchus of B10, suggesting that branch formation in this region is influenced more by environmental factors than by genetic factors.     

Measurements of thermal properties for human femora

In this study, density, specific heat, thermal conductivity, and thermal diffusivity were measured experimentally along the lengths of human cadaveric femora. Fresh and dry bone samples were selected from both male and female specimens, and for different age groups varying between 44 and 73 years old. Measured values for specific heat vary between 1.14 and 2.37 J/gm degrees C; for thermal conductivities the range is from 0.16 to 0.34 W/m degrees C; and for thermal diffusivities the range is from 0.10 to 0.23 cm2/sec, depending on whether the bone samples were fresh or dry, cancellous or cortical. The experimental results are presented in non-dimensional coordinates and are compared with the few other data available in the literature.     

Regional blood flow analysis and its relationship with arterial branch lengths and lumen volume in the coronary arterial tree

The limitations of visually assessing coronary artery disease are well known. These limitations are particularly important in intermediate coronary lesions (30-70% diameter stenosis) where it is difficult to determine whether a particular lesion is the cause of ischaemia. Therefore, a functional measure of stenosis severity is needed. The purpose of this study is to determine whether the expected maximum coronary blood flow in an arterial tree is predictable from its sum of arterial branch lengths or lumen volume. Using a computer model of a porcine coronary artery tree, an analysis of blood flow distribution was conducted through a network of millions of vessels that included the entire coronary artery tree down to the first capillary branch. The flow simulation results show that there is a linear relationship between coronary blood flow and the sum of its arterial branch lengths. This relationship holds over the entire arterial tree. The flow simulation results also indicate that there is a 3/4 power relation between coronary blood flow (Q) and the sum of its arterial lumen volume (V). Moreover, there is a linear relationship between normalized Q and normalized V raised to a power of 3/4 over the entire arterial tree. These results indicate that measured arterial branch lengths or lumen volumes can be used to predict the expected maximum blood flow in an arterial tree. This theoretical maximum blood flow, in conjunction with an angiographically measured blood flow, can potentially be used to calculate fractional flow reserve based entirely on angiographic data.