Moorhead K T, Chase J G, David T, Arnold J
Department of Mechanical Engineering, University of Canterbury, Private Bag 4800, Christchurch, New Zealand.
J Biomech Eng. 2006 Jun;128(3):462-6. doi: 10.1115/1.2187048.
The Circle of Willis (CoW) is a ringlike structure of blood vessels found at the base of the brain. Its main function is to distribute oxygen-rich arterial blood to the cerebral mass. In a previous study, a one-dimensional (1D) model of the CoW was created to simulate a series of possible clinical scenarios such as occlusions in afferent arteries, absent or stringlike circulus vessels, or arterial infarctions (Moorhead et al., 2004, Comput. Methods Biomech. Biomed. Eng., 7(3), pp. 121-130). The model captured cerebral haemodynamic autoregulation by using a proportional-integral-derivative (PID) controller to modify efferent artery resistances. Although some good results and correlations were achieved, the model was too simple to capture all the transient dynamics of autoregulation. Hence a more physiologically accurate model has been created that additionally includes the oxygen dynamics that drive the autoregulatory response. Results very closely match accepted physiological response and limited clinical data. In addition, a set of boundary conditions and geometry is presented for which the autoregulated system cannot provide sufficient perfusion, representing a condition with increased risk of stroke and highlighting the importance of modeling the haemodynamics of the CoW. The system model created is computationally simple so it can be used to identify at-risk cerebral arterial geometries and conditions prior to surgery or other clinical procedures.
Willis环（CoW）是位于脑底部的一种环状血管结构。其主要功能是将富含氧气的动脉血输送到脑实质。在之前的一项研究中，创建了一个Willis环的一维（1D）模型，以模拟一系列可能的临床情况，如传入动脉阻塞、环血管缺失或呈条索状，或动脉梗死（Moorhead等人，2004年，《计算方法在生物力学和生物医学工程中的应用》，第7卷第3期，第121 - 130页）。该模型通过使用比例积分微分（PID）控制器来修改传出动脉阻力，从而捕捉脑血流动力学自动调节。尽管取得了一些良好的结果和相关性，但该模型过于简单，无法捕捉自动调节的所有瞬态动力学。因此，创建了一个生理上更准确的模型，该模型还包括驱动自动调节反应的氧动力学。结果与公认的生理反应和有限的临床数据非常匹配。此外，还给出了一组边界条件和几何形状，对于这些条件，自动调节系统无法提供足够的灌注，这代表了一种中风风险增加的情况，并突出了对Willis环血流动力学进行建模的重要性。所创建的系统模型计算简单，因此可用于在手术或其他临床程序之前识别有风险的脑动脉几何形状和状况。
