三维心电场的有限元仿真方法─—心电场仿真三维模型的理论基础

心电场仿真是心电理论的前沿课题，本文提出心电场耗散能量的数学模型及有限元求解方程，揭示心电场活动规律．     

三维心电场仿真模型及计算机仿真——Ⅰ心电场仿真模型的理论基础

心电场计算机仿真是心理论研究的重要手段,也是心电理论研究的前沿课题之一。本文介绍了我们新近在IBM PC机上开发完成的心电仿真模型,其各项指标均达到了国外同类模型的水平,它能完成以往在大型机上实现的仿真模型所能完成的研究工作。     

Kubicek每博心输出量计算公式的三维有限元仿真研究

我们从Kubicek模型三维有限元仿真的角度对Kubicek每搏心输出量计算公式的临床应用价值进行了研究。在计算机仿真研究中，我们对比了模型仿真结果、具体采用Kubicek每搏心输出量计算公式所得结果以及所设模型的理论计算结果。仿真结果表明：模型中阻抗改变与主动脉中血液容积改变之间存在着近拟的线性关系，证明了Kubicek每搏心输出量计算公式具有一定的临床应用价值，同时也为心阻抗血流图基础理论提供了新的研究途径。     

Kubicek每搏心输出量计算公式的三维有限元仿真研究

我们从 Kubicek模型三维有限元仿真的角度对 Kubicek每搏心输出量计算公式的临床应用价值进行了研究。在计算机仿真研究中 ,我们对比了模型仿真结果、具体采用 Kubicek每搏心输出量计算公式所得结果以及所设模型的理论计算结果。仿真结果表明 :模型中阻抗改变与主动脉中血液容积改变之间存在着近似的线性关系 ,证明了 Kubicek每搏心输出量计算公式具有一定的临床应用价值 ,同时也为心阻抗血流图基础理论提供了新的研究途径。     

每搏心输出量计算中电极配置结构的三维有限元仿真研究

从Kubicek模型三维有限元仿真的角度对用于每搏心输出量（SV）测定的Kubicek电极配置结构进行了三维有限元的仿真研究。分别探讨了电压电极带的宽度、厚度、材料特性即电阻率大小对SV计算结果的影响,以指导临床中电极配置结构及其材料的选择。仿真结果表明：Kubicek电极配置结构中,其电压电极带的特性,如材料的选择、带的宽度及带的厚度均对模型中用于SV计算的阻抗值结果产生影响,其中材料的选择是主要的影响因素。因此,采用Kubicek法进行SV计算时,应注意Kubicek电极配置结构的选择,以提高SV临床计算的精度。     

微机心电场仿真模型与仿真研究

心电场仿真是心电理论研究的前沿课题。本文讨论首次在IBM-PC/AT微机上实现的一个完整的心电场仿真模型。其中,人体和心脏的单元分割精度与国外最近的研究相同,采用边界元法求解心电场电位,并提出一种新的心脏兴奋传播仿真算法,提高了仿真速度。应用该模型对正常心脏和病变心脏进行了仿真研究,仿真结果与临床测量结果是一致的。     

人体胸腔三维恒定电场分布的有限元程序设计方法

本文介绍了一种采用等参数８节点任意六面体单元来求解人体胸腔三维恒定电场分布的有限元程序设计方法，程序的编制基于ＢｒｏｌａｎｄＣ＋＋Ｆｏｒ ＤＯＳ的编程环境，在对最终形成的有限元代数方程的求解过程中采用了分块处理总系数矩阵及“取大数”处理边界条件的方法。该程序设计方法为进一步深入研究人体胸腔阻抗血流图波形的成因打下了基础。     

Two-layered quasi-3D finite element model of the oesophagus

Analysis of oesophageal mechanoreceptor-dependent responses requires knowledge about the distribution of stresses and strains in the layers of the organ. A two-layered and a one-layered quasi-3D finite element model of the rat oesophagus were used for simulation. An exponential pseudo-strain energy density function was used as the constitutive equation in each model. Stress and strain distributions at the distension pressures 0.25 and 1.0 kPa were studied. The stress and strain distributions depended on the wall geometry. In the one-layered model, the stress ranged from -0.24 to 0.38 kPa at a pressure of 0.25 kPa and from -0.67 to 2.57 kPa at a pressure of 1.0 kPa. The stress in the two-layered model at the pressure of 0.25 and 1.0 kPa varied from -0.52 to 0.64 kPa and from -1.38 to 3.84 kPa. In the two-layered model, the stress was discontinuous at the interface between the muscle layer and the mucosa-submucosa layer. The maximum stress jump was 1.67 kPa at the pressure of 1.0 kPa. The present study provides a numerical simulation tool for characterising the mechanical behaviour of a multi-layered, complex geometry organ.     

Three-dimensional fibril-reinforced finite element model of articular cartilage

Collagen fiber orientations in articular cartilage are tissue depth-dependent and joint site-specific. A realistic three-dimensional (3D) fiber orientation has not been implemented in modeling fluid flow-dependent response of articular cartilage; thus the detailed mechanical role of the collagen network may have not been fully understood. In the present study, a previously developed fibril-reinforced model of articular cartilage was extended to account for the 3D fiber orientation. A numerical procedure for the material model was incorporated into the finite element code ABAQUS using the “user material” option. Unconfined compression and indentation testing was evaluated. For indentation testing, we considered a mechanical contact between a solid indenter and a medial femoral condyle, assuming fiber orientations in the surface layer to follow the split-line pattern. The numerical results from the 3D modeling for unconfined compression seemed reasonably to deviate from that of axisymmetric modeling. Significant fiber orientation dependence was observed in the displacement, fluid pressure and velocity for the cases of moderate strain-rates, or during early relaxation. The influence of fiber orientation diminished at static and instantaneous compressions.     

Three-dimensional filamentous human diseased cardiac tissue model

A human in vitro cardiac tissue model would be a significant advancement for understanding, studying, and developing new strategies for treating cardiac arrhythmias and related cardiovascular diseases. We developed an in vitro model of three-dimensional (3D) human cardiac tissue by populating synthetic filamentous matrices with cardiomyocytes derived from healthy wild-type volunteer (WT) and patient-specific long QT syndrome type 3 (LQT3) induced pluripotent stem cells (iPS-CMs) to mimic the condensed and aligned human ventricular myocardium. Using such a highly controllable cardiac model, we studied the contractility malfunctions associated with the electrophysiological consequences of LQT3 and their response to a panel of drugs. By varying the stiffness of filamentous matrices, LQT3 iPS-CMs exhibited different level of contractility abnormality and susceptibility to drug-induced cardiotoxicity.     

基于冷冻切片的人体腰椎三维有限元模型

目的利用上海交通大学生命质量与机械工程研究所自主开发的冷冻切片处理软件CryoSegmemation提取人体骨骼的边缘,利用逆向工程软件Imageware建立骨骼的面模型,在ANSYS中建立人体腰椎的三维有限元模型。方法利用第三军医大学的第一例男性冷冻切片数据进行图像处理,截面轮廓线信息处理。结果准确快速地建立了完全符合人体解剖特征的腰椎三维有限元模型。结论利用该研究所自主开发的冷冻切片软件和一些现有的商用软件可以准确、快速地建立人体腰椎的三维面模型、体模型及有限元模型,为航空、车辆、船舶、生物医学工程等不同的领域进行数值模拟计算和动力学仿真提供完全符合人体解剖学特征的原始模型。     

A finite volume model of cardiac propagation

This paper describes a two-dimensional cardiac propagation model based on the finite volume method (FVM). This technique, originally derived and applied within the field of computational fluid dynamics, is well suited to the investigation of conduction in cardiac electrophysiology Specifically, the FVM permits the consideration of propagation in a realistic structure, subject to arbitrary fiber orientations and regionally defined properties. In this application of the FVM, an arbitrarily shaped domain is decomposed into a set of constitutive quadrilaterals. Calculations are performed in a computational space, in which the quadrilaterals are all represented simply as squares. Results are related to their physical-space equivalents by means of a transformation matrix. The method is applied to a number of cases. First, large-scale propagation is considered, in which a magnetic resonance-imaged cardiac cross-section serves as the governing geometry. Next, conduction is examined in the presence of an isthmus formed by the microvasculature in a slice of papillary muscle tissue. Under ischemic conditions, the safety factor for propagation is seen to be related to orientation of the fibers within the isthmus. Finally, conduction is studied in the presence of an inexcitable obstacle and a curved fibe field. This example illustrates the dramatic influence of the complex orientation of the fibers on the resulting activation pattern. The FVM provides a means of accurately modeling the cardiac structure and can help bridge the gap between computation and experiment in cardiac electrophysiology.     

Microcomputer-based cardiac field simulation model

Cardiac field simulation is one of the frontier subjects in electrocardiogram theory study. The paper describes a complete cardiac simulation model implemented on an IBM-PC/AT microcomputer. This model uses a new algorithm for excitation propagation simulation. In comparison with the previous rule-based algorithms, the new algorithm shows better in simulation speed and simulation accuracy.     

仿真环境下医学器官的三维有限元建模方法

背景：通过医学影像图片数据进行三维重建的模型主要应用于医学临床分析,而采用激光扫描进行逆向重建时建立的模型主要用于生物力学分析。生物力学模型建立的精确程度,直接影响分析结果。 目的：分析采用医学影像图片数据和三维激光扫描重建医学器官模型的两种方法及意义。 方法：①通过人体CT断层扫描医学影像图片数据,并运用医学重建软件进行三维重建。②采用三维激光扫描仪对医学模型进行扫描得到点云数据,再利用逆向处理软件实现医学器官模型的逆向重建。 结果与结论：两种方法都可以建立符合人体解剖结构、可进行生物力学仿真计算的几何模型和有限元模型。医学影像CT/MRI数据重建的三维模型,能够真实再现被扫描对象的表面特征及内部结构,该模型为临床辅助诊断、手术规划、整形、假肢设计及解剖教学等方面提供了可靠的参考模型。三维激光扫描所得点云数据进行逆向重建,具有测量精度高、速度快,能够反映所测标本的表面形态,该模型可在交通运输、军事领域中因发生钝性冲击对人体内部器官造成的损伤进行计算机仿真分析。     

3D heart model for computer simulations in cardiac surgery

For a satisfactory computer simulation, a model, which imitates a natural situation, is needed. The Human heart is an irregular 3D object and thus difficult to reproduce. Basic data was taken from Visible Human Dataset (VHD), National Library of Medicine. The heart area was cut out of the original cross-sections and different tissues segmented. All the slices also had to be aligned to assure precise overlapping of the structures. A 3D computer heart model with the resolution of 1mm was designed. The heart model was dedicated to simulations of heat transfer during heart surgery however, it is applicable also to other medical simulations.