Mabotuwana Thusitha D S, Cheng Leo K, Pullan Andrew J
Bioengineering Institute, The University of Auckland, Auckland, New Zealand.
Biomed Eng Online. 2007 May 8;6:17. doi: 10.1186/1475-925X-6-17.
There are some early clinical indicators of cardiac ischemia, most notably a change in a person's electrocardiogram. Less well understood, but potentially just as dangerous, is ischemia that develops in the gastrointestinal system. Such ischemia is difficult to diagnose without angiography (an invasive and time-consuming procedure) mainly due to the highly unspecific nature of the disease. Understanding how perfusion is affected during ischemic conditions can be a useful clinical tool which can help clinicians during the diagnosis process. As a first step towards this final goal, a computational model of the gastrointestinal system has been developed and used to simulate realistic blood flow during normal conditions.
An anatomically and biophysically based model of the major mesenteric arteries has been developed to be used to simulate normal blood flows. The computational mesh used for the simulations has been generated using data from the Visible Human project. The 3D Navier-Stokes equations that govern flow within this mesh have been simplified to an efficient 1D scheme. This scheme, together with a constitutive pressure-radius relationship, has been solved numerically for pressure, vessel radius and velocity for the entire mesenteric arterial network.
The computational model developed shows close agreement with physiologically realistic geometries other researchers have recorded in vivo. Using this model as a framework, results were analyzed for the four distinct phases of the cardiac cycle--diastole, isovolumic contraction, ejection and isovolumic relaxation. Profiles showing the temporally varying pressure and velocity for a periodic input varying between 10.2 kPa (77 mmHg) and 14.6 kPa (110 mmHg) at the abdominal aorta are presented. An analytical solution has been developed to model blood flow in tapering vessels and when compared with the numerical solution, showed excellent agreement.
An anatomically and physiologically realistic computational model of the major mesenteric arteries has been developed for the gastrointestinal system. Using this model, blood flow has been simulated which show physiologically realistic flow profiles.
心脏缺血存在一些早期临床指标，最显著的是人的心电图变化。而在胃肠道系统中发生的缺血情况则鲜为人知，但可能同样危险。由于该疾病具有高度非特异性，若无血管造影（一种侵入性且耗时的检查方法），这种缺血很难诊断。了解缺血状态下灌注如何受到影响可能是一种有用的临床工具，可在诊断过程中帮助临床医生。作为实现这一最终目标的第一步，已开发出一种胃肠道系统的计算模型，并用于模拟正常情况下的实际血流。
已开发出一种基于解剖学和生物物理学的主要肠系膜动脉模型，用于模拟正常血流。模拟所用的计算网格是利用可视人项目的数据生成的。控制该网格内流动的三维纳维-斯托克斯方程已被简化为一种高效的一维格式。该格式与本构压力-半径关系一起，已对整个肠系膜动脉网络的压力、血管半径和速度进行了数值求解。
所开发的计算模型与其他研究人员在体内记录的生理现实几何形状显示出密切的一致性。以该模型为框架，分析了心动周期的四个不同阶段——舒张期、等容收缩期、射血期和等容舒张期的结果。给出了在腹主动脉处周期性输入在10.2千帕（77毫米汞柱）至14.6千帕（110毫米汞柱）之间变化时，显示随时间变化的压力和速度的剖面图。已开发出一种解析解来模拟锥形血管中的血流，与数值解相比，显示出极佳的一致性。
已为胃肠道系统开发出一种基于解剖学和生理学的主要肠系膜动脉计算模型。利用该模型模拟的血流显示出符合生理现实的血流剖面图。
