二尖瓣偏心反流定量计算的超声模拟研究

发布时间：2018-02-23 01:13

本文关键词： 二尖瓣偏心反流 Field_II超声模拟附壁射流模型定量计算　出处：《四川大学》2007年硕士论文　论文类型：学位论文

【摘要】： 二尖瓣病变是心血管病中最常见的疾病之一，二尖瓣反流的精确定量评价对于临床修复或置换瓣膜手术的时机选择以及术后评估都有着重要的指导意义。目前，基于超声多普勒成像的二尖瓣检查成为反流评价最重要的工具，它操作简便、无副作用、成本低。然而，由于流场的复杂性，目前缺乏相关的流场模型，迄今为止，对于临床二尖瓣偏心反流的评价没有金标准，大部分医生仍是根据彩色多普勒凭借经验或用半定量的方法判断反流的严重程度，这在某种程度上限制了临床上利用彩色多普勒超声心动图对二尖瓣偏心反流进行评估的应用。本文在给出血流模型的基础之上，运用超声模拟软件Field_Ⅱ，模拟二尖瓣偏心反流并成像。并通过定量计算的反流率与模型的标准反流率进行比较，分析角度大小对反流量估计的影响因素，提出角度与反流量大小的一个定量关系，为建立临床二尖瓣偏心反流定量评价模型和制定评价金标准提供一定的依据。首先在系统研究了附壁射流数学模型与二尖瓣偏心反流模型之间的关系后，根据二尖瓣反流的血流动力学以及反流的特征并综合实验室以前的研究成果及目前国外最近的研究报道，建立了两种偏心反流的数学模型，第一种为瓣口尺寸d=0.01m，没有负向回流；第二种为瓣口尺寸d=0.005m，有负向回流。用超声模拟软件field_Ⅱ，根据给出的数学模型实现了两种情况下二尖瓣偏心反流的模拟显像，获得了两种模型下6个角度的模拟成像结果，分析了各个角度对于血流成像的影响，并利用所获得的rf信号，，通过目前大多数商品化彩色血流图系统采用的自相关技术实现了截面的速度信息提取。然后选取距离瓣口2cm-4cm的范围内相隔0.1cm的21个截面进行定量计算，以图表的形式给出了两个模型下6种常用角度的估计值结果，并与模型值进行比较，详细分析了成像角度对于偏心反流严重程度的评价影响。结果表明超声估计出来的反流量确实是要比真实值要低估，而且随着角度的不断增加，低估的量也相应的增大，这个和实际的情况是一致的。而且随着角度的不断增大，各个角度的反流率低估的趋势不断增加，并指出在用超声多普勒对二尖瓣偏心反流严重程度进行估计时，最好把成像的角度控制在20度之内，这样可以有效的减小由于角度原因对诊断结果的严重低估。通过对比两种模型下，计算值与模型值的差值与模型值本身的百分比的变化趋势及相关性分析，指出尽管模型不同，但是两组百分比却成高度相关(r=0.9977)。以此为据，利用最小二乘拟合出了超声成像角度与低估百分比之间的一个定量关系，可以用于修正估计出来的反流量，提高临床上评估二尖瓣偏心性反流程度的精确性。
[Abstract]:Mitral valve disease is one of the most common diseases in cardiovascular disease. The accurate quantitative evaluation of mitral regurgitation is of great significance for the choice of time for clinical repair or replacement valve surgery and for postoperative evaluation. Mitral valve examination based on Doppler ultrasound is the most important tool for reflux evaluation. It is easy to operate, has no side effects, and has low cost. However, due to the complexity of flow field, there is a lack of relevant flow field models. There is no gold standard for the evaluation of clinical eccentric mitral regurgitation, and most doctors still judge the severity of regurgitation on the basis of color Doppler experience or semi-quantitative methods. This limits the clinical application of color Doppler echocardiography in the assessment of eccentric mitral regurgitation. Based on the model of bleeding flow, this paper uses the ultrasonic simulation software FieldII to simulate the eccentric mitral regurgitation and imaging, and compares the reflux rate calculated quantitatively with the standard regurgitation rate of the model. This paper analyzes the influence factors of angle size on back flow estimation, and puts forward a quantitative relationship between angle and reverse flow, which provides a certain basis for establishing a quantitative evaluation model of eccentric mitral regurgitation and establishing the evaluation gold standard for clinical mitral eccentricity regurgitation. Firstly, the relationship between the mathematical model of the wall attached jet and the eccentric regurgitation model of the mitral valve is studied systematically. According to the hemodynamics of mitral regurgitation and the characteristics of mitral regurgitation, two kinds of mathematical models of eccentric regurgitation were established according to the previous research results in laboratory and recent reports abroad. The second is the valve orifice size dn0. 005m, with negative reflux. By using the ultrasonic simulation software fieldII, the simulation imaging of mitral eccentric regurgitation in two cases is realized according to the given mathematical model, and the simulated imaging results of 6 angles under two models are obtained. The effects of different angles on blood flow imaging are analyzed, and the obtained RF signals are used. The velocity information of the cross section is extracted by autocorrelation technique which is used in most commercial color flow chart systems at present. Then 21 sections with a distance of 0.1 cm within the distance of 2cm-4cm from the valve orifice are selected for quantitative calculation. The estimation results of six common angles under two models are given in the form of charts, and compared with the values of the model, and the influence of imaging angle on the severity of eccentric reflux is analyzed in detail. The results show that the inverse flow estimated by the ultrasound is indeed lower than the true value, and with the increasing of the angle, the undervalued amount increases accordingly, which is consistent with the actual situation. And with the increasing of the angle, The tendency to underestimate the reflux rate at all angles is increasing, and it is pointed out that in estimating the severity of eccentric mitral regurgitation with Doppler ultrasound, it is best to keep the imaging angle within 20 degrees. By comparing the difference between the calculated value and the model value and the percentage of the value of the model itself, it is pointed out that although the model is different, the difference between the calculated value and the value of the model is different. However, the two groups of percentages were highly correlated to 0.99770.The least square method was used to fit a quantitative relationship between the angle of ultrasound imaging and the under-estimated percentage, which could be used to correct the estimated backflow. Improve clinical accuracy in assessing the degree of eccentric mitral regurgitation.
【学位授予单位】：四川大学
【学位级别】：硕士
【学位授予年份】：2007
【分类号】：R312

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