Topical cardiac cooling--computer simulation of myocardial temperature changes

Topical cardiac cooling (TC) is often used in cardiac surgery. We used a computer simulation to study temperature changes in the heart, especially in the right ventricular wall. A three-dimensional computer heart model, derived from Visible Human Data set, National Library of Medicine was used. The model is made from cubes, with spatial resolution of 1mm. Explicit Finite Different method and temperature diffusion equation were used to calculate new temperatures. Three different simulations were performed and simulated temperatures were drawn on a cross-section of heart model in different colors. The results show that areas not immersed into TC solution are less protected against ischemia. It is important not to rely solely on topical cooling but use appropriate method of myocardial protection technique.     

心电图心肌缺血可视化显示与输出

目的:研究常规12导联心电图心肌缺血的三维可视化显示和输出。方法:利用美国可视人体心脏切面解剖数据,用Rhino建立三维心脏表面模型,把模型输出为XGL格式的文档,并从此文档中提取三维模型顶点信息,用VC 和Direct3D编写三维显示子程序读取这些顶点信息,显示心脏三维模型并实现对三维模型运动的控制,根据缺血ST段偏移方向和幅值,在心脏三维模型上用颜色深浅来表示缺血区面积大小及心肌缺血的程度。结果:经临床应用,常规心电图心肌缺血的部位、范围和程度可以通过三维动态心脏模型准确、形象的显示出来,显示结果可以动画和图片两种格式保存和输出。结论:将可视人技术和心电图有机结合起来,可拓展心电图的应用空间。     

Acceleration of cardiac tissue simulation with graphic processing units

In this technical note we show the promise of using graphic processing units (GPUs) to accelerate simulations of electrical wave propagation in cardiac tissue, one of the more demanding computational problems in cardiology. We have found that the computational speed of two-dimensional (2D) tissue simulations with a single commercially available GPU is about 30 times faster than with a single 2.0 GHz Advanced Micro Devices (AMD) Opteron processor. We have also simulated wave conduction in the three-dimensional (3D) anatomic heart with GPUs where we found the computational speed with a single GPU is 1.6 times slower than with a 32-central processing unit (CPU) Opteron cluster. However, a cluster with two or four GPUs is faster than the CPU-based cluster. These results demonstrate that a commodity personal computer is able to perform a whole heart simulation of electrical wave conduction within times that enable the investigators to interact more easily with their simulations.     

Three-dimensional reconstruction of paracentesis approach in transjugular intrahepatic portosystemic shunt

To establish a digital transjugular intrahepatic portosystemic shunt (TIPS) model and provide morphological data for radiological diagnosis and interventional radiology to reduce portal vein pressure, 400 serial sectional images from the internal jugular vein superior margin to the lower edge of the liver were chosen from the Chinese Visible Human dataset. Surface and volume reconstructions were performed using 3D-DOCTOR 3.5 software on an ordinary personal computer. Volume and surface renderings were employed to perform data segmentation and image edge detection for reconstruction of the internal jugular vein, brachiocephalic vein, superior vena cava, heart, inferior vena cava, hepatic vein, and portal vein for computerized 3D reconstruction of the TIPS pathway and construction of a 3D visible model of different structures along it. The model can also display pathway and distribution characteristics and interactively show the spatial structural relationships between intrahepatic venous lines from any position and angle, plus complete data acquisition for any range and angle for 3D reconstruction with stereopsis and measurements using any visualization platform. The digital reconstruction of the TIPS pathway correctly reflected the complicated anatomic structural characteristics and spatial adjacency relationships between intrahepatic venous lines, providing a reference 3D morphology for image diagnostics and interventional TIPS therapy.     

Thin sectional anatomy, three-dimensional reconstruction and visualization of the heart from the Chinese Visible Human

The research aimed to provide sectional anatomic and three-dimensional (3D) virtual anatomic bases for imaging diagnosis and surgical operation by the use of data from the heart of the first Chinese digitized Visible Human. Data from the series of thin sections of the heart were analyzed and input into an SGI workstation, and 3D reconstruction and virtualization of the heart were performed. Each image of sectional anatomy was clear and the 3D structures of the heart were reconstructed in their entirety. All reconstructed structures can be displayed by multiple structural and color modes, individually or jointly, and can be rotated continuously in any plane. The model of the virtual heart clearly showed fine structures of the heart in random orientation. The dataset of the sectional anatomy provides a fine and integrated morphologic base for imaging diagnosis. The 3D reconstructed images clearly show the internal and entire structures of the heart.This research was supported by the National Science Fund of China (NSFC) nos. 39925022 and 30720698     

The study of three-dimensional reconstruction of Chinese adult liver

Purpose  To build a three-dimensional (3D) visible model of human liver and provide visualization of precise anatomical structures for making plans for hepatic operations and obtain accurate simulation of liver on computer. Methods  Based on the Chinese Visible Human data set, the hepatic structures were precisely segmented by Photoshop software. Then the segmented structures were reconstructed in surface rendering method and the hepatic parenchyma and the other parts of upper abdomen were reconstructed with volume rendering method by using our software on personal computer. Results  A 3D model of human liver and its surrounding structures was built. The reconstructed structures can be displayed singly, in small groups or as a whole and can be continuously rotated in 3D space at different velocities. This model can help doctors to understand the spatial structure of the liver and its surrounding organs and also help surgeons to devise a reasonable surgical plan and reduce the risk of surgical malpractice. Conclusion  Combining volume-rendering reconstruction with surface rendering reconstruction can overcome some of the defects of both rendering reconstructions. The reconstructed liver and the main internal structures are realistic, which demonstrate the natural shape and exact position of the structures. They provide an accurate anatomical model for Chinese adult and also provide a basis for performing virtual hepatic operation.     

基于心室动作电位的三维心肌组织模型算法研究

心肌电折返是引起心律失常的重要因素之一,它会导致心动过速(VT)乃至室颤(VF)的发生,从而引起心源性猝死。随着计算机仿真在定量电生理研究中的广泛应用,迫切需要建立三维心肌组织实验平台。本文就这种组织模型的数值解方法进行了研究。文中利用Luo-Rudy 1991心室肌细胞模型结合扩散方程形成三维组织模型,利用算子分裂法求其数值解。分别采用ADI格式和七点差分格式求解描述电扩布的偏微分方程,边界条件采用二阶精度的离散格式。实验结果表明,以上两种格式均可成功地解算出细胞膜电位的变化以及电兴奋的活动,且具有良好的稳定性。但ADI格式可较大幅度地缩短计算时间。因此ADI格式下增加时间步长以提高计算效率的方法更具优势。     

Physical and computer modelling of blood flow in a systemic-to-pulmonary shunt

The aim of this work was the application of computer and physical in vitro simulation methods for estimating surgery procedure hemodynamics. The modified Blalock-Taussig (mB-T) palliative surgical procedure is performed to increase the pulmonary blood flow in children with congenital heart defects. Such a systemic-to-pulmonary shunt yields substantial modification in the blood flow within the large blood vessels. The objective of the present study was to investigate basic characteristics of the flow, flow pattern and pressure-flow efficiency, before and after opening of the mB-T graft. Methods: The model was based on the vessel geometry obtained from the Visible Human Project and included the arch of aorta, the three arteries branching from the arch, the pulmonary trunck, and the left and right pulmonary arteries. The graft was added between the left subclavian artery and the left pulmonary artery. The glass model of the vessels was produced and investigated in a physical model of the cardiovascular system with an artificial ventricular device as the blood pump. Flow rate and hydrostatic pressure were measured at the inlet to and outlets from the glass model and in a few points within the system. Laser flow visualization was also performed. Computer simulations were done using the boundary conditions from the physical model. Results: The opening of the mB-T graft changed flow distribution in all branches (including inflow). A complex flow pattern with large eddies and channelling of the flow in the vicinity of the graft and within it was observed in flow visualization and in computer simulations. Because of that complexity the local measurements of hydrostatic pressure at the vessel wall could not predict the average flow rate. The reversed flow in the graft was observed during the systole. Conclusions: The complex flow pattern developed in the physical model of the mB-T graft. The channelling of the flow and the formation of large eddies may yield high shear stress and modify blood properties. The rigid wall model can describe only some flow characteristics observed in vivo. Computer simulation is a very fast and accurate method which permits earlier qualification of cardiac surgeons on how to change cardiac vascular blood flow after operations.     

数字化人体表面三维重建及显示的有关问题

目的：探讨使用切片技术建模的“虚拟人体”图库,重建人体三维图像的表面形状。方法：在目前通用的个人计算机装备上,结合计算机的视觉、数据存储、图形学和数字图像处理等技术,重建人体表面三维图像。结果：在大图库基础上建立了小图库,减少了数据量;通过滤镜除去噪点,提取边界;确定可见边界点,消除冗余边界点;构成前视冠状图;将静态显示制成动画;用实时计算显示,解决可控问题。结论：探讨了变处理大图库大数据量为小图库小数据量,建立表面三维要素数据库,减少计算机的计算量,加速三维重建及显示的过程,对未来“虚拟中国人”应用有较宽广的覆盖面。     

Analysis of cardiac ventricular wall motion based on a three-dimensional electromechanical biventricular model

This paper describes a biventricular model, which couples the electrical and mechanical properties of the heart, and computer simulations of ventricular wall motion and deformation by means of a biventricular model. In the constructed electromechanical model, the mechanical analysis was based on composite material theory and the finite-element method; the propagation of electrical excitation was simulated using an electrical heart model, and the resulting active forces were used to calculate ventricular wall motion. Regional deformation and Lagrangian strain tensors were calculated during the systole phase. Displacements, minimum principal strains and torsion angle were used to describe the motion of the two ventricles. The simulations showed that during the period of systole, (1) the right ventricular free wall moves towards the septum, and at the same time, the base and middle of the free wall move towards the apex, which reduces the volume of the right ventricle; the minimum principle strain (E3) is largest at the apex, then at the middle of the free wall and its direction is in the approximate direction of the epicardial muscle fibres; (2) the base and middle of the left ventricular free wall move towards the apex and the apex remains almost static; the torsion angle is largest at the apex; the minimum principle strain E3 is largest at the apex and its direction on the surface of the middle wall of the left ventricle is roughly in the fibre orientation. These results are in good accordance with results obtained from MR tagging images reported in the literature. This study suggests that such an electromechanical biventricular model has the potential to be used to assess the mechanical function of the two ventricles, and also could improve the accuracy of ECG simulation when it is used in heart-torso model-based body surface potential simulation studies.     

The Effect of Conductivity on ST-Segment Epicardial Potentials Arising from Subendocardial Ischemia

We quantify and provide biophysical explanations for some aspects of the relationship between the bidomain conductivities and ST-segment epicardial potentials that result from subendocardial ischemia. We performed computer simulations of ischemia with a realistic whole heart model. The model included a patch of subendocardial ischemic tissue of variable transmural thickness with reduced action potential amplitude. We also varied both intracellular and extracellular conductivities of the heart and the conductivity of ventricular blood in the simulations. At medium or high thicknesses of transmural ischemia (i.e., at least 40% thickness through the heart wall), a consistent pattern of two minima of the epicardial potential over opposite sides of the boundary between healthy and ischemic tissue appeared on the epicardium over a wide range of conductivity values. The magnitude of the net epicardial potential difference, the epicardial maximum minus the epicardial minimum, was strongly correlated to the intracellular to extracellular conductivity ratios both along and across fibers. Anisotropy of the ischemic source region was critical in predicting epicardial potentials, whereas anisotropy of the heart away from the ischemic region had a less significant impact on epicardial potentials. Subendocardial ischemia that extends through at least 40% of the heart wall is manifest on the epicardium by at least one area of ST-segment depression located over a boundary between ischemic and healthy tissue. The magnitude of the depression is a function of the bidomain conductivity values.     

基于"中国数字人"切片和CT数据重建下颌骨的对比研究

目的：探索快速重建人体下颌骨三维模型的方法，比较常用CT资料重建与切片资料重建骨组织的优劣差异。方法：获得虚拟人数据集，并取虚拟人数据中下颌骨部分的切片资料和CT资料分别进行软件的三维重建。结果：利用切片资料建立了较之CT资料更为精细准确的人体下颌骨三维模型。结论：采用应用软件重建方法快速可行，而且利用虚拟人的切片数据建立了高度精确的下颌骨三维模型。     

手指解剖结构的三维建模及临床意义

目的:应用计算机辅助模拟技术(CAD)建立手指解剖结构的三维模型.在计算机上实现手指解剖结构的三维演示.方法:根据手部解剖图谱及相关资料,应用3ds max的放样、多边形等算法建立三维模型.结果:应用上述方法成功地建立了手指解剖结构及指固有动脉逆行岛状瓣的三维模型.该模型可在电脑屏幕上自由旋转,隐藏不感兴趣结构.结论:应用三维建模软件进行手指解剖结构的三维演示是可行的,它有助于人们更好的理解和记忆解剖结构,进行手指手术设计.     

Study Development of the Cardiac Computer Simulations

The technique of computer simulations is a very efficient method in investigating mechanisms of many diseases. This paper reviews how the simulations of the human heart started as a simple mathematical models in the past and developed to the point where genetic information is needed to do suitable work like finding out new medicaments against heart diseases. Also the Influence of the development of computer performance in the future as well as the data presentation is described.     

3D打印技术在先天性心脏病伴气管软化诊断与治疗中的应用

目的:运用3D打印技术建立儿童先天性心脏病伴气管软化模型,探讨3D打印建模对于临床诊断和治疗方案制定的意义。 方法:1例先天性心脏病伴气管软化的患儿,行容积螺旋穿梭技术（VHS）CT扫描后获得影像资料;将CT图像导入Mimics 17.0软件并对气管区域进行图像重建后处理,得到气管三维重建模型;再运用3-Matic10.0软件对三维模型进行网格优化操作并保存成STL格式;最后将数据导入Objet 260 3D打印机打印出三维模型。 结果:利用3D打印构建了患儿吸气相和呼气相气管模型,与气管镜检查的结果一致。 结论:通过3D打印技术打印了患儿的全尺寸气管模型,给先天性心脏病伴气管软化的临床诊断和治疗予以有效的协助和指导。     

The initiator titration model: computer simulation of chromosome and minichromosome control

The initiator titration model was formulated to explain the initiation control of the bacterial chromosome. In particular, features concerning the replication behaviour of minichromosomes, such as their high copy number and Escherichia coli's ability to coinitiate chromosome and many minichromosome origins, were considered during the formulation of the model. The model is based on the initiator protein DnaA and its binding sites, DnaA boxes, in oriC, in the dnaA promoter and at other positions on the chromosome. Another important factor in the model is the eclipse period created by the hemimethylation of a new oriC which makes it refractory to initiation. The model was analysed by computer simulations using a stochastic approach varying the different input parameters, and the resulting computer cells were compared with data on living E. coli cells. Here we present the outcome of a few of these simulations concerning the eclipse period, in silico-shift experiments blocking initiation or elongation of replication, and introduction of minichromosomes into the computer cells. We also discuss the synthesis of DnaA protein in the computer cells. From our simulations, we conclude that, whether true or not, the model can mimic the in vivo initiation control of E. coli.     

侧向冲击载荷作用下股骨-骨盆复合体的生物力学响应

目的利用三维有限元分析方法研究股骨-骨盆复合体在人体侧向摔倒时冲击载荷作用下的生物力学行为特性。方法基于中国力学虚拟人模型库建立股骨-骨盆-软组织复合体的三维有限元模型,包括皮质骨、松质骨和软组织;同时,构建一个刚体平面仿真地面。约束地面刚体,对整个股骨-骨盆-软组织复合体模型施加侧向2 m/s的速度载荷,整个仿真分析时间设定为20 ms。通过三维有限元分析计算获得股骨-骨盆侧摔冲击过程中应力应变变化特性。结果在13 ms时,股骨大转子处软组织与地面的接触力达到最大值7 656 N,对应的骨盆软组织上的最大等效应力值为2.64 MPa。冲击过程中,耻骨联合处骨皮质上等效应力出现极大值,为142.64 MPa,接近其屈服强度;股骨颈和大转子处应力水平较高,股骨颈处皮质骨上的最大等效应力值为76.49 MPa;股骨颈处松质骨上的最大等效应力值为8.44 MPa,最大压缩应变值为0.94%;股骨大转子处松质骨上的最大等效应力值为8.50 MPa,最大压缩应变值为0.93%。结论人体股骨-骨盆复合体在侧摔减速冲击载荷作用下股骨颈、大转子及耻骨联合处易出现骨折。     

Tachycardia-induced early afterdepolarizations: insights into potential ionic mechanisms from computer simulations

Although early afterdepolarizations (EADs) are classically thought to occur at slow heart rates, mounting evidence suggests that EADs may also occur at rapid heart rates produced by tachyarrhythmias, due to Ca overload of the sarcoplasmic reticulum (SR) leading to spontaneous SR Ca release. We hypothesized that the mechanism of tachycardia-induced EADs depends on the spatial and temporal morphology of spontaneous SR Ca release, and tested this hypothesis in computer simulations using a ventricular action potential mathematical model. Using two previously suggested spontaneous release morphologies, we found two distinct tachycardia-induced EAD mechanisms: one mechanistically similar to bradycardia-induced EADs, the other to delayed afterdepolarizations (DADs).     

An Experimentally Derived Stress Resultant Shell Model for Heart Valve Dynamic Simulations

In order to achieve a more realistic and accurate computational simulation of native and bioprosthetic heart valve dynamics, a finite shell element model was developed. Experimentally derived and uncoupled in-plane and bending behaviors were implemented into a fully nonlinear stress resultant shell element. Validation studies compared the planar biaxial extension and three-point bending simulations to the experimental data and demonstrated excellent fidelity. Dynamic simulations of a pericardial bioprosthetic heart valve with the developed shell element model showed significant differences in the deformation characteristics compared to the simulation with an assumed isotropic bending model. The new finite shell element model developed in the present study can also incorporate various types of constitutive models and is expected to help us to understand the complex dynamics of native and bioprosthetic heart valve function in physiological and pathological conditions.     

Interactive Visualization and Analysis of Multimodal Datasets for Surgical Applications

Surgeons use information from multiple sources when making surgical decisions. These include volumetric datasets (such as CT, PET, MRI, and their variants), 2D datasets (such as endoscopic videos), and vector-valued datasets (such as computer simulations). Presenting all the information to the user in an effective manner is a challenging problem. In this paper, we present a visualization approach that displays the information from various sources in a single coherent view. The system allows the user to explore and manipulate volumetric datasets, display analysis of dataset values in local regions, combine 2D and 3D imaging modalities and display results of vector-based computer simulations. Several interaction methods are discussed: in addition to traditional interfaces including mouse and trackers, gesture-based natural interaction methods are shown to control these visualizations with real-time performance. An example of a medical application (medialization laryngoplasty) is presented to demonstrate how the combination of different modalities can be used in a surgical setting with our approach.